PUBLIC HEALTH ASSESSMENT
PADUCAH GASEOUS DIFFUSION (USDOE)
PADUCAH, MCCRACKEN COUNTY, KENTUCKY
The U.S. Department of Energy (DOE)'s Paducah Gaseous Diffusion Plant (PGDP) was added to the U.S. Environmental Protection Agency's Superfund National Priorities List (NPL) on May 31, 1994, because elevated concentrations of trichloroethylene (TCE) and technetium 99 (Tc-99) were found in off-site groundwater (residential wells). The Superfund law (CERCLA) requires that the Agency for Toxic Substances and Disease Registry (ATSDR) conduct a public health assessment for all sites listed on the NPL. This public health assessment evaluates contaminant distributions, community health concerns, and available health outcome information to determine the potential for community exposures to hazardous substances and adverse public health effects resulting from those exposures.
The plant, which is about 10 miles (16 kilometers) west of Paducah, Kentucky, began operation in 1952. PGDP produces enriched uranium with a higher than natural concentration of uranium 235, using a gaseous form of uranium (uranium hexafluoride). TCE was used as a solvent to clean metal parts. Tc-99, a radioactive substance, was introduced at the site when uranium used in a reactor was reprocessed. This public health assessment presents an evaluation of these and other chemical and radioactive contaminants in human exposure pathways. ATSDR also considered other hazards--such as accidents involving the depleted uranium cylinders stored at and transported to and from this site--in evaluating the public health effects of past, current, and future PGDP operations on the surrounding community.
According to the information reviewed by ATSDR, under normal operating conditions, the Paducah Gaseous Diffusion Plant currently poses no apparent public health hazard for the surrounding community from exposure to groundwater, surface water, soil and sediment, biota, or air. "No apparent public health hazard" means that people may be exposed to contaminated media near the site, but that exposure to the contamination is not expected to cause any adverse health effects. We define "current" as ranging from 1990 to the present. This conclusion assumes the effectiveness of access restrictions to Little Bayou Creek, the outfalls, and the North-South Diversion Ditch; the fish advisories issued for Little Bayou Creek and some of the ponds in the Western Kentucky Wildlife Management Area; and existing regulation of discharges to air and surface water.
Historical groundwater exposure to TCE and lead was a public health hazard for children routinely drinking water from four residential wells. This means that long-term exposure occurred at concentrations that may have caused adverse health effects in children. A future groundwater exposure pathway could exist if new wells are drilled into the northwest or northeast plumes. No current exposure pathways to contaminated groundwater exist, but the current restrictions between DOE and the property owners do not restrict the drilling of new wells by future owners of this land. Although it is unlikely, potential future exposures could occur if new wells are drilled into these plumes.
Groundwater exposures to vinyl chloride (a degradation product of TCE) and acute air exposures to uranium and hydrogen fluoride are an indeterminate public health hazard for past and potential future exposures. This means that the information available is incomplete.
Information on vinyl chloride exposures is incomplete because the detection limits in most analyses of samples from tested residential wells were well above the levels of concern. Also, not all residential wells in or near the plume were tested for vinyl chloride. Future groundwater monitoring for vinyl chloride and other TCE degradation products should be low enough to determine whether concentrations exceed health-based guidelines. However, there appears to be no current exposure to vinyl chloride since these wells are not being used.
Past short-term, or acute air exposures to uranium and hydrogen fluoride are indeterminate, because total release quantities and completed exposure pathways are uncertain. The worst reported accidental release happened at 4:00 am on November 17, 1960. Potentially hazardous uranium and hydrogen fluoride concentrations, estimated using air dispersion models, reached off-site areas, but because the accident occurred at 4:00 a.m., it is not known if any residents were exposed. If people were exposed at the concentrations estimated by the model, adverse health effects may have resulted. Currently, we have no reports of health effects related to this accident; however, if data become available suggesting that health effects did occur, we will re-evaluate the need for followup activities.
Past long-term, or chronic uranium and hydrogen fluoride exposures were below levels of public health concern.
In the future, the rupture of one or more depleted uranium cylinders, which could occur from a transportation accident involving a fire, would create an urgent public health hazard for anyone near the accident. Weather conditions and duration of exposure would affect the distance from the accident at which there would be a hazard; however, we predict that (1) the maximally exposed individual would be 100 feet (30 meters) or less from the accident and (2) an urgent public health hazard could exist out to 230 feet (70 meters) from the accident. Less-severe health effects could be experienced by individuals within several thousand meters of the accident. This type of accident is very unlikely.
For other accident scenarios such as a plane crash, severe weather, or natural disasters involving the on-site depleted uranium cylinders, a temporary public health hazard could exist off site from hydrogen fluoride exposure. It is very unlikely that such an accident would happen.
ATSDR representatives reviewed available health outcome data, such as cancer registries and vital statistics. We evaluated the data using age-adjusted rates, concentrating mostly on nine general types of cancer. The health outcome data reviewed do not apply specifically to small groups of people who have been, or could be, exposed to PGDP contaminants. The data are recorded for larger areas (area development districts or counties) which include many people with no exposures to contaminants from the site (approximately 63,000 in McCracken County, 8,000 in Ballard County, and 15,000 in Massac County). The population of concern for the exposure pathways in the PDGP area (approximately 15 to 90 persons) is small. The associations between exposure from this site and any adverse health effects would be obscured or distorted by the presence of the much larger unexposed population.
ATSDR has collected people's concerns from the communities around PGDP for this public health assessment. Many people expressed concerns related to the incidence of cancer and other illnesses in the area and the possibility of exposure to contaminants through various media. Community concerns and our responses are presented in the main part of this document.
Based on the data and information obtained and evaluated for this public health assessment, ATSDR recommends the following:
Several of these recommendations may already be addressed by actions taken by DOE, the U.S. Enrichment Corporation, or other agencies. These actions are discussed in the Public Health Action Plan in the main part of this document.
ATSDR staff will continue to monitor environmental issues and remedial activities at PGDP, as well as proposals related to storage and transport of the depleted uranium cylinders. The interpretation, conclusions, and recommendations provided in this public health assessment are based on the data and information referenced. Additional data could alter those conclusions and recommendations. The conclusions and recommendations are site specific and should not be considered applicable to any other situation.
The Paducah Gaseous Diffusion Plant (PGDP) is a U.S. Department of Energy (DOE) owned, contractor-operated uranium enrichment facility. It is about 10 miles (16 kilometers) west of the city of Paducah and 3.5 miles (5.6 kilometers) south of the Ohio River in McCracken County, Kentucky (Figure 1) [1,2]. The site was added to the U.S. Environmental Protection Agency's (EPA's) Superfund National Priorities List (NPL) on May 31, 1994, because elevated concentrations of trichloroethylene and technetium 99 were found in off-site groundwater.
The primary plant process, gaseous diffusion, is a
physical process to enrich uranium hexafluoride
(UF6)--that is, to increase the percentage of uranium
235 (U-235) above natural concentrations in the UF6.
In the process, solid UF6 containing about 0.7% U-235 is heated to form a compressed gas. The gas is
fed through diffusion stages--compressors and converters. PGDP has 1,812 diffusion stages
housed in five buildings, which cover about 74 acres (30 hectares) [3]. The "product" (UF6
enriched up to 2.75% U-235 [4]) and "tails" (UF6 depleted between 0.2% and 0.4% U-235) are
removed and put in cylinders [5]. The product is shipped to another uranium enrichment facility
in Piketon, Ohio for further enrichment; however, the Piketon enrichment operation is scheduled
to shut down in the summer of 2001. PGDP is being upgraded to enrich uranium up to 5% U-235
by the spring of 2001 [6]. Most of the tails have been stored in cylinders in storage yards on site.
The enrichment process requires large amounts of electric power, lubrication, and air cooling. Electricity for the diffusion processes comes from the steam plant in Joppa, Illinois, and from the Tennessee Valley Authority (TVA) Shawnee Steam Plant, north of the site on the Ohio River. The compressed gases are cooled by heat exchange fluid, which in turn is cooled by recirculating water processed through four sets of cooling towers.
The PGDP facilities include process buildings, four major electrical switchyards, a three-boiler steam plant, a water treatment facility, a chemical cleaning and decontamination building, the northwest groundwater treatment facility, the northeast groundwater treatment system, maintenance and laboratory facilities, two active landfills, and several inactive facilities inside a fenced security area (Figure 2) [1,7]. The steam plant provides process and comfort heating for other buildings on site. In 1974 and 1975, two boilers were converted to burn low-sulfur coal and oil instead of natural gas. The third boiler burns natural gas or oil but cannot be converted to burn coal [8,9]. The site also includes a raw-water treatment plant, a residential landfill, an inert landfill, a former sanitary landfill, two industrial treatment lagoons, and several concrete rubble piles outside the fenced area.
 Figure 1. Plant Location and Vicinity (jpg) |
 Figure 1. Plant Location and Vicinity (pdf) |
 Figure 2. Plant Map (jpg) |
Figure 2. Plant Map (pdf) |
PGDP was built on a portion of 16,126 acres (6,450 hectares) of farmland acquired by the U.S. Department of Defense (DOD) during World War II. DOD acquired this land for a munitions facility, the Kentucky Ordnance Works (KOW), which was operated by Atlas Powder Company until it was closed in 1946 [1]. The KOW included a trinitrotoluene (TNT) manufacturing area; an acid production area; coal, sulfur, toluene, and ordnance storage areas; a sewage treatment plant; a water treatment plant; and burning grounds. PGDP now uses the water treatment plant. In 1950, 7,556 acres (3,022 hectares) of the land east of the former KOW were acquired by the Atomic Energy Commission as a site for a uranium enrichment facility--that is, PGDP. The plant began operating in 1952, but construction was not completed until 1954. The facility reservation covered a total of 3,424 acres (1,397 hectares), with about 750 acres (300 hectares) within the security fence. The rest of the land was transferred to TVA for the Shawnee Steam Plant and to the Commonwealth of Kentucky for wildlife conservation and recreational purposes [2].
In the early
years, the facilities included the gaseous diffusion plant, the uranium
hexafluoride manufacturing plant, the uranium metals plant, and
over a hundred support buildings [10,11]. The uranium hexafluoride manufacturing
plant converted natural uranium trioxide to UF6. It also converted
uranium reprocessed from plutonium production reactor tails. The reprocessing
of uranium brought to the site other radioactive materials not associated with
naturally occurring uranium, e.g., technetium 99 (Tc-99), americium 241 (Am-241),
neptunium 237 (Np-237), and plutonium 239 (Pu-239). Tc-99 was first reported
in airborne releases in 1953 [12]. Tc-99, Np-237, and Pu-239 were first reported
in liquid releases in 1953. The uranium hexafluoride manufacturing plant was
deactivated in 1964, but reactivated in 1968 and used until 1977. At the uranium
metals plant, depleted UF6 was reacted with hydrogen to recover
hydrogen fluoride and to convert the volatile UF6 to more easily
stored uranium tetrafluoride (UF4). Some of the UF4 was
reduced with magnesium to uranium metal. The uranium metals plant stopped operating
in 1975 [13].
In 1974, the responsibility for PGDP was
given to the newly formed U.S. Energy
Research and Development Administration,
which became DOE in 1977. DOE's primary
contractor for all operations was Martin
Marietta Energy Systems, Inc., which later
became Lockheed Martin Energy Systems (LMES) and Lockheed Martin Utility Services
(LMUS). Beginning July 1, 1993, LMUS operated and maintained PGDP under contract to the
United States Enrichment Corporation (USEC), the government-owned corporation formed by
the National Energy Policy Act of 1992 to take over the nation's uranium enrichment business
[2]. DOE remains as site owner of the original property. Environmental compliance and waste
generated from the operating plant since July 1, 1993, are the responsibility of the USEC. The
U.S. Nuclear Regulatory Commission assumed oversight of these activities on March 3, 1997
[14]. DOE and LMES retained the responsibility for environmental remediation and waste
handling from activities performed prior to July 1, 1993 [2]. As of April 1, 1998, the new DOE
contractor for these responsibilities is Bechtel-Jacobs Company [15].
Site Visits and Collection of Community Concerns
ATSDR representatives visited the PGDP site in May 1994, as part of a program to evaluate DOE NPL sites and to develop a workplan to address those sites. Some community health concerns were identified during this site visit and during ATSDR's participation in six DOE public meetings in June 1994, May 1995, July 1995, November 1996, January 1998, and July 1999 [16].
Community concerns also were identified through written correspondence, telephone conversations, informal meetings, and public availability sessions. In 1995 ATSDR solicited concerns from community members by direct mail inquiry: a package containing a query letter, an information brochure about ATSDR, and a self-addressed business reply envelope was mailed to about 1,700 community members. A total of 60 people responded to this mailing. In May 1996 ATSDR held five public availability sessions in Paducah and Heath, Kentucky, to solicit additional concerns. The public availability sessions were informal and allowed citizens to discuss their health concerns related to the site, one-on-one, with an ATSDR team member [17]. Staff from ATSDR and Boston University gathered concerns by attending several Site Specific Advisory Board (SSAB) meetings and DOE technical presentations. All in all, ATSDR received about 500 community concerns. These concerns are discussed in Appendix B and in the community health concerns section later in this report. Most of the concerns relate to the incidence of cancer, the incidence of other illnesses, and the possibility of exposure through various media.
ATSDR staff members visited the site in January 1996 to discuss the ATSDR public health assessment (PHA) process and ATSDR's data needs with DOE and LMES officials [18].
In March 1996, project representatives visited the area to discuss the PHA process with citizens, gauge the community's interest in public availability sessions, and meet with the newly formed Site Specific Advisory Board (SSAB) and local health officials [19]. They toured the Western Kentucky Wildlife Management Area (WKWMA) with a community member and staff from Kentucky's Department of Fish and Wildlife Resources and Kentucky's Department for Environmental Protection.
ATSDR representatives visited the area in December 1996, to gather relevant demographic and land-use data and to investigate possible exposure pathways in the community near the facility [20]. In June 1997, the ATSDR team conducted another site visit to address the SSAB and to meet with various officials and residents in the area [21]. In February 1998, staff attended the SSAB meeting and the first public meeting for the Draft Programmatic Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of Depleted Uranium Hexafluoride [22]. In July 2000, ATSDR staff attended DOE's public meeting on the Groundwater Operable Unit Feasibility Study and the SSAB meeting.
On September 11, 2000, an ATSDR representative addressed Active Citizens for Truth (ACT), a local community group, to discuss ATSDR and ATSDR's role at the PGDP site.
Demographic information characterizes the people in the communities potentially affected by the site, how long these people have lived there, and the current population trends [23]. Delineating the number of children and elderly people is particularly important, because these people tend to be more sensitive to environmental exposures than the general population [24]. Also, information on occupation, education level, poverty status, and household income can give clues to factors such as access to health care and subsistence fishing, hunting, or farming. Demographic information is essential when analyzing health outcome data and behavior patterns in a community.
PGDP is in northwestern McCracken County, Kentucky, near the border of Ballard County. North of the site (on the north side of the Ohio River) lies Massac County, Illinois. In the past, this area of Kentucky and southern Illinois was predominantly rural, with little population growth; now, however, McCracken County's population is growing [25]. The addition of new housing subdivisions west of the city of Paducah accounts for the bulk of the growth [26]. Also, there is an initiative to bring new industries into the area, which will undoubtedly affect the make-up of the population near the site. McCracken County, at 60,000 residents, has the largest population of the three counties near the site [27].
According to the 1990 U.S. Census, the largest cities in a 10-mile (16-kilometer) radius of the site are Paducah, Kentucky (27,256 persons); Metropolis, Illinois (6,734 persons); and Joppa, Illinois (492 persons) [25]. There are several small communities closer to the site: Heath, Grahamville, Rossington, Woodville, and Kevil. The two closest are Grahamville at 1.24 miles (2 kilometers) and Heath at 1.86 miles (3 kilometers) east of the plant [4].
The three counties encompassing the site have more people over 65 years of age than under 10 years of age [25]. This is unusual compared to the 1990 national averages, but not unusual for rural areas.
In the census tracts surrounding the site, approximately 70% of people 25 and older have high school diplomas, and approximately 15% are below the poverty level [28]. Over 75% of the residents live in owner-occupied housing units, which suggests a stable, non-transient population. Also, 25% of the housing units get their water from drilled wells or sources other than public or private suppliers. DOE has offered to provide municipal water to some residents of western McCracken County (in an area described in DOE's Water Policy), who previously used private wells (see the groundwater section of this report). For more detailed demographic information for this site, refer to Appendix A.
Land Use and Natural Resources
Land-use patterns and natural resource use in the area of the site can demonstrate if or how people could be exposed to environmental contaminants. Using well water, farming or gardening, and hunting or fishing are some of the activities that can result in exposure to site contaminants. Knowing the locations of schools, hospitals, and nursing homes is also important, since the populations of these institutions tend to be elderly, sick, or very young, and consequently may be at higher risk for adverse health effects. Reviewing zoning patterns helps us understand future use of land around the site and helps us evaluate the potential hazard to the community.
PGDP is in a rural/suburban area of McCracken County. The residential area near the plant is in a state of transition. Farmlands are increasingly being subdivided for additional residential development. The area west of Paducah, along US Route 60 (Figure 1), is the site of new subdivisions. A new US Route 60 is being built to accommodate the projected heavier traffic in the corridor between Paducah (Interstate 24) and the emerging suburbs. According to a December 1997 communication with the McCracken County Planning Office, US Route 60 will not be moved near the plant entrance, but will be widened. The closest residences to the site are approximately 3,280 feet (1,000 meters) north and 3,609 feet (1,100 meters) east of the PGDP fence line [29]. The closest schools are Heath Elementary, Middle, and High Schools. These are 1.86 miles (3 kilometers) southeast of the plant. According to information obtained from Heath Elementary school, there was another school--Forestdale Elementary--1.16 miles (1.86 kilometers) southwest of the plant; that school was closed in 1981 when Heath Elementary opened (Figure 3).
According to a June 1997 communication with the West McCracken County Water District, new homes being built in the area are served by municipal water through their local water districts, which receive water from the Ohio River. Other residents use drilled wells, except for those residents living in the Water Policy area that DOE has connected to a municipal water supply. Neither the Kentucky Department for Environmental Protections (KDEP)'s Division of Water nor the Purchase District Health Department routinely test existing wells; however, the health department will do limited testing on a well if asked. Newly drilled wells are tested for bacteria, iron, copper, and nitrates. Hand-dug (shallow) wells are illegal in Kentucky and are not under regulation by the Division of Water. Heath Elementary, Middle, and High Schools are supplied with municipal water from the Western McCracken County Water District. The high school was put on municipal water in 1968.
 Figure 3. Property Boundaries and Other Features (jpg) |
Figure 3. Property Boundaries and Other Features (pdf) |
There are approximately 400 active farms in McCracken County, Kentucky, with 45 to 50 operating in the area near PGDP [30]. Soybeans, wheat, corn, and tobacco are the dominant crops being cultivated. Although the number of individual tobacco farms has declined, the acreage used for this crop has been steady: farms have been consolidated under fewer owners. In general, the dominant crops grown in the area are shipped to national and international markets. There are people who grow their own vegetables in the area for personal use; however, this practice (as well as cultivating specialty crops for commercial sale) is on the decline. There are approximately 350 head of dairy cattle and 4,000 head of beef cattle in McCracken County.
Hand-dug wells are not used for irrigation of farmland. The farms rely on rainfall to water their crops and to supply large ponds used for recreation and watering livestock. The water for these ponds is not supplied by wells. The area receives an average of 47 inches (1.19 meters) of precipitation per year; the heaviest precipitation usually comes in March, April, and May [8,9,31].
Industrial activity now accounts for less than 5% of the land use [5]. With increasing residential use and the widening of US Route 60, however, this percentage may increase in the near future. The TVA Shawnee Steam Plant and PGDP are the main employers in the area. There is also a privately owned steam plant in Joppa, Illinois, across the Ohio River. (The steam plants, both coal-fired, were built in the early 1950s to supply electricity to PGDP). The Allied Signal Plant, which makes uranium fluoride products for PGDP, is across the Ohio River west of Metropolis, Illinois. Calvert City, a major industrial area, is approximately 13 miles (21 kilometers) east of the city of Paducah. It has the largest concentration of industry in western Kentucky; however, it is not believed to have an impact on public health in the PGDP area [32].
The WKWMA includes a 2,781-acre (1,125-hectare) buffer zone that surrounds PGDP [5]. This area is open to the public and is a popular location for local sports, fishing, and hunting. The WKWMA is accessible from Dyke Road, Ogden Landing Road, McCaw Road, and Woodville Road (Figure 3). Within the WKWMA are signs denoting DOE property and a fence separating the federal facility from public areas. Two families live on or within the WKWMA. One person who lives there maintains the area for the Kentucky Department of Fish and Wildlife Resources. The WKWMA supports an abundance and diversity of wild animals. Deer, fowl, turtles, fish, and small mammals such as raccoons are some of the animals caught in the area. Most community members believe that these animals are consumed by the hunters and fishers themselves [17]. Sports enthusiasts tend to come from a wide area within the region, whereas subsistence users tend to live near the city of Paducah. We found no evidence of camping.
The WKWMA includes the former KOW, where abandoned bunkers and other debris associated with past activities still exist. The former KOW's remedial investigation and cleanup are being managed by the U.S. Army Corp of Engineers (USACE) [16]. Some of the old bunkers have been used for hunting clubs, dog pens, and horse barns. Six ponds (or gravel pits), which are used for fishing, are part of the USACE's investigation and cleanup. Mercury advisories are posted at Fire Hydrant Pond, Horseshoe Pond, New Pond, Box Factory, and Gravel Pit #1 for largemouth bass [33]. No advisories have been issued for channel catfish or bluegills, which also are present.
One of the largest organized annual events to take place in the WKWMA is Earth Day, which takes place in the spring. On Earth Day, large groups of preteens gather to learn about nature and the environment [1]. Many area schools participate in this event, which is sponsored by DOE, Bechtel Jacobs Company, and the Kentucky Department of Fish and Wildlife Resources.
PGDP is on relatively flat land--ranging from 367 to 380 feet (112 to 116 meters) above sea level--on a drainage divide between Big Bayou and Little Bayou Creeks [13]. Both creeks flow north to the Ohio River, and receive surface water discharges from the plant. When the TVA Shawnee Power Plant was built in 1951 and 1952, Little Bayou Creek was diverted to the west, where it now joins with Big Bayou Creek before entering the Ohio River (Figure 1) [34,35]. Big Bayou Creek flows past a residential area to the west of the plant and overflows into people's fields during times of flooding. Channel catfish and bluegill appear in Big Bayou only when it is filled with backwater from the Ohio River, and fishing occurs occasionally. Little Bayou Creek is an intermittent stream on the eastside of the plant. Little flow occurs in Little Bayou Creek except for effluent from the plant [8,9]. Fishing does not normally occur in this creek. Warning signs for polychlorinated biphenyl (PCB) contamination in fish are posted at access areas along this creek, and these areas are partially fenced off. Fences and "No Trespassing" signs are present at all plant outfalls; however, in the past, access to Little Bayou Creek was generally unrestricted.
Residents of the surrounding communities also use the Ohio River and Metropolis Lake for recreational purposes. These surface water bodies are located approximately 3 miles (4.8 kilometers) north and northeast of PGDP, respectively. Metropolis Lake connects to the Ohio River and is part of a nature reserve. There is a warning issued against eating bass, carp, channel catfish, paddlefish and paddlefish eggs caught in the Ohio River due to chlordane and PCB contamination. Recently, a fish advisory was issued for Metropolis Lake due to mercury and PCB contamination.
At PGDP, the wind predominantly comes from the south-southwest, at an average speed of 14.4 feet per second (4.4 meters per second) [8,9,31]. The monthly average temperatures vary from 34oF (1oC) during January to about 77oF (26oC) in July. The average annual temperature is 59oF (14oC).
ENVIRONMENTAL CONTAMINATION, EXPOSURE PATHWAYS, AND POTENTIALLY EXPOSED POPULATIONS
This section discusses the various chemicals and radioactive materials (contaminants) evaluated for this site, how people may come into contact with them, and what populations are potentially exposed. These discussions are presented for groundwater, air, surface water, soil and sediment, and food and biota.
A release of a chemical or radioactive
material from a site does not always mean
that this substance will be a contaminant of
health concern to an off-site population.
ATSDR scientists first determine if a
chemical or radioactive substance in water,
air, soil, or biota (plants and animals) should
be considered a "contaminant of concern."
The criteria we use include (1) environmental levels exceeding media-specific comparison
values, (2) noted community health concerns, and (3) the quality and extent of the sampling data
we can use to evaluate potential exposure and human health hazard. For inorganic compounds
(metals) and radionuclides, background values may also be considered, since some of these
substances occur naturally. For chemicals, the highest environmental concentration detected off
site is compared with media-specific comparison values to determine if further evaluation is
warranted. Generally, if a contaminant's concentration exceeds one or more media-specific
comparison values, then the contaminant is evaluated further in this section and in the public
health implications section. (Refer to Appendix C for a description of comparison values.)
A release of a chemical or radioactive material into the environment does not always result in human exposure. For an exposure to occur, a completed exposure pathway must exist. A completed exposure pathway exists when all of the following five elements are present: (1) a source of contamination, (2) an environmental medium through which the contaminant is transported, (3) a point of human exposure, (4) a route of human exposure, and (5) an exposed population. A potential exposure pathway exists when one or more of the elements is missing, but available information indicates that human exposure is likely. Also, an exposure pathway is considered potential when modeled data are used to predict human exposure. An incomplete exposure pathway exists when one or more of the elements is missing and available information indicates that human exposure is unlikely to occur [23]. Figure 4 illustrates the necessary components of an exposure pathway.
Figure 4. Pathways To Exposure From Contamination
In addition, for each exposure pathway, ATSDR scientists identify whether releases of contaminants and exposures are likely to have occurred in the past, currently, or potentially in the future. All releases from the uranium process facilities have dramatically decreased since the first 10 years of plant operation; however, releases from other sources such as landfills and spill areas have increased.
This section also discusses potential hazards created by the storage of about 40,351 depleted uranium cylinders in outdoor cylinder yards. (Of these cylinders, 28,351 came from DOE and about 12,000 came from the U.S. Enrichment Corporation, or USEC.)
In this report, "on-site contamination and releases" describes contamination and releases of material within the fenced security area of the site or in areas for which public access is restricted (i.e., groundwater wells outside the security fence but on DOE property). "Off-site contamination" describes environmental media (soil, sediment, surface water, groundwater, air, or biota) that are contaminated as a result of chemical or radioactive contaminants leaving the site and are no longer being controlled by DOE or USEC. In this report, on-site sources of contamination are being considered only as sources of off-site contamination or for their impact on the community. (The impact of potential exposures to contaminants by workers is being studied by other organizations.)
Background and Site Hydrogeology
In August 1988,
contamination by trichloroethylene (TCE), an organic solvent, and technetium
99 (Tc-99), a beta-emitting radionuclide, was detected in four residential drinking
water wells located just north of the PGDP facility boundary [36]. Concentrations
of TCE ranged from 1.5 to 960 µg/L. Tc-99 concentrations ranged from 25 to 400
pCi/L. During that same year, residents were supplied with an alternate water
source, and DOE initiated an extensive groundwater monitoring and analysis program
[37].
Although no residents are currently exposed to off-site groundwater contaminants, four families living north of the facility were exposed to contamination prior to the August 1988 action. Since very little measured data exist to support the evaluation of public health effects for past exposures (prior to 1988), evaluation of past exposures is based on predicted or estimated contaminant concentrations and exposure durations. There is also potential for future exposures if contaminated groundwater migrates into areas not covered by DOE's Water Policy supply program or if future property owners drill new wells into the contaminated groundwater plumes.
The primary aquifer underlying the PGDP site is the Regional Gravel Aquifer (RGA). Flow is generally toward the north, with presumed discharge into the Ohio River or Big Bayou Creek immediately south of the Ohio River [37]. The aquifer is 10 to 40 feet (3 to 12 meters) thick and composed of very permeable sands and gravels. The RGA is the source of drinking water for residents with drilled wells in the PGDP area. In 1990, approximately 8% of the homes in McCracken County and 9% of the homes in Ballard County relied on privately drilled wells for their drinking water. In the census block group that includes PGDP, 24% of the houses relied on privately drilled wells [28].
The McNairy formation underlies the RGA. Water-bearing zones within the McNairy formation occur within sand layers interspersed in a relatively thick sequence of clays. Sandy units of the upper McNairy formation may make up the lowermost portion of the RGA in areas north of the PGDP facilities. Also, erosion of clay in the vicinity of PGDP allows interaction of the RGA with the McNairy and presents the potential for RGA contaminants to move into the McNairy formation [38]. Flow within the McNairy formation is north to northeast from the PGDP site. The McNairy formation is used as a drinking and industrial water source north of the Ohio River. According to analysis of hydraulic gradients in the McNairy formation, flow should discharge into the Ohio River [38]. The Kentucky Department for Environmental Protection analyzed samples taken north of the Ohio River, and did not detect contaminants characteristic of PGDP.
Groundwater is also present in the alluvial, loess, and Upper Continental deposits, which are above the RGA. The water table in these shallow units is typically 10 to 15 feet (3 to 4 meters) below land surface in the northwestern part of the site, and up to 46 feet (14 meters) below land surface in other areas [7]. Water flow in the shallow units is predominantly downward into the RGA, but lateral flow occurs in more permeable units and toward the surface water reaches. Surface water from Big Bayou Creek and Little Bayou Creek contributes to groundwater in the RGA for areas south of the site, with a transition to discharge from the RGA to surface waters north of the site [7].
Contaminants entered the groundwater as a
result of several processes: (1) disposal
practices (e.g., oil landfarming), (2)
accidental releases or spills (e.g., cylinder
leaks and ruptures, cylinder drop test area,
C-400 waste system leak), and (3) indirect
leaching from buried waste materials (e.g.,
C-749 uranium burial ground, C-404 low-level radioactive waste burial ground). Table 1 gives a
description and brief history of these sources. Several site-wide investigations have been
conducted, and additional characterization and remediation of the contaminant source areas are
currently ongoing.
Releases of contaminants into the groundwater varied widely over time and happened throughout the operating history of the plant. Leaching from disposal areas occurred over time, because buried drums and containers decompose slowly. There are now three groundwater contaminant plumes: the northwest plume, the northeast plume, and the southwest plume. Each plume has several sources; therefore, it is not possible to establish a specific time of origin for the plumes based on times of contaminant releases.
Several source control or interim remedial actions have been established to reduce contaminant migration from the site. These actions include (1) capping source areas with impermeable covers and (2) establishing extraction and treatment systems to remove contaminants from groundwater. The northwest plume treatment system was established in 1995, the northeast plume treatment system in 1997.
The distribution of several contaminants suggests that the Tennessee Valley Authority (TVA) Shawnee Steam Plant may be a source of some groundwater contaminants. Contaminants from the PGDP site have migrated in the northwest plume to the TVA plant. However, groundwater concentrations of arsenic, cadmium, chromium, lead, and uranium 238 at the TVA site are higher than concentrations in the northwest plume, and these contaminants were detected at the TVA plant before the PGDP plume reached the plant. Because these contaminants are the same as those detected at PGDP and are present in the same environmental media, they will be evaluated through the same exposure pathways.
Table 1. Groundwater contaminant sources at the Paducah
Gaseous Diffusion Plant [39,40,7]
| Northwest Plume1 Contaminant Source/SWMU | Source Description/History | Contaminants |
| C-400 area; TCE leak site/11, C-400 to C-404 underground transfer line/26, C-403 neutralization tank/40, C-400 Tc-99 storage tank/47, C-400 sump/203; C-400 south end storm sewer | Facility maintenance area; leak in waste processing lines and sump--repaired 1986 | TCE DNAPL (up to 890,000 µg/L in UCRS), Tc-99, 1,2-DCE, PCE, total PAHs, chromium |
| C-746-A septic system/196 | Sinks, showers, toilets, and floor drains; system was used from 1958 to 1980; contaminants probably released into drains | Heavy metals, radionuclides, possible TCE |
| C-745-B Cylinder drop test area/91 | TCE-based slush bath used to chill UF6 cylinders for shock tests; tests conducted in 1979 | TCE DNAPL (up to 160,000 µg/L in UCRS), 1,2-DCE, 1,1,1-TCA, PCE, chloroform |
| C-749 Uranium burial ground/2 | Burial ground in the northwest corner inside the security fence | TCE |
| C-404 Low-level waste burial ground/3 | Low-level radioactive and hazardous waste burial ground | TCE |
| C-747-A Burial ground/7 and 30 | Burial ground in the northwest corner inside the security fence | TCE |
| Southwest Plume2 Contaminant Source/SWMU | Source Description/History | Contaminants |
| C-747-C oil landfarm/1; C-747-C contaminated burial yard/4 | Landspreading of contaminated waste oil; site operated 1973-1979 | Petroleum products, TCE, 1,1,1-TCA, uranium, PCBs |
| C-720 Building and storm sewer | Maintenance facility | TCE, Tc-99 |
| C-740 TCE spill site/136 | TCE spill site | TCE |
| Northeast Plume3 Contaminant Source/SWMU | Source Description/History | Contaminants |
| C-745 Kellog building Site/99 | Building used for pipe fabrication during plant construction (1951-1956); extensive use of TCE; building demolished in 1956 | TCE, 1,1-DCE, low concentrations of Tc-99 |
| C-400 area/40 (C-403 neutralization tank) | Possible leak from tank or transfer line | TCE (up to 11,000 µg/L in RGA), Tc-99 (up to 1,735 pCi/L in RGA) |
| McGraw underground storage tank, southside cylinder yard, and construction facility; SWMUs 183, 193, and 194, respectively | Site characterization studies ongoing | |
| 1 Source: [41,42] 2 Source: [42] 3 Source: [42,43] |
||
| Key: 1,1-DCE = 1,1-dichloroethene;
1,1,1-TCA = 1,1,1-trichloroethane; 1,2-DCE = 1,2-dichloroethene; DNAPL =
dense nonaqueous-phase liquid; PAHs = polyaromatic hydrocarbons; PCBs = polychlorinated biphenyls; PCE = tetrachloroethylene; SWMU = solid waste management unit; Tc-99 = technetium 99; TCE = trichloroethylene; UCRS = Upper Continental Recharge System |
||
Results of groundwater monitoring, provided to ATSDR in several databases from DOE and the Commonwealth of Kentucky, were screened to determine contamination concentrations and distributions. These databases were transferred electronically and checked for completeness and consistency. Incomplete or missing records that could not be corrected with supporting documents or communications with site personnel were not used in the screening process. Electronic data were supplemented with published documents.
Because numerous
chemical analyses were performed for groundwater, ATSDR scientists used a series
of screening techniques to focus their evaluation on contaminants that
may be a human health hazard. The first phase of screening involved
identifying contaminants detected above media-specific comparison values in
on-site or off-site well samples. Forty-seven contaminants have been
detected in groundwater wells at concentrations above these comparison values.
(Refer to Appendix C for a description of comparison
values).
The second phase of screening was to determine whether the groundwater contaminants are present or potentially present in residential wells. Thirty of the forty-seven contaminants have been found in off-site groundwater wells where exposure to the community is possible. Table 2 provides information about these contaminants, the number of samples analyzed, the number of samples with positive detections, and maximum concentrations detected in off-site wells. Note that inclusion of a substance in Table 2 does not mean that anyone was exposed to that substance.
The third phase of screening involved comparing maximum concentrations of off-site groundwater contaminants in areas of potential exposure with their respective comparison values. Contaminant concentrations below these comparison values are not expected to cause adverse health effects following exposure. For contaminant concentrations above comparison values, ATSDR evaluated potential or documented exposures and public health implications.
Table 2. Off-site groundwater contaminants [44,45,46,47,48]
| Metals and Elements | Number of Off-Site Samples | Number of Off-Site Detects | Off-Site Maximum Concentration in µg/L | Background Range in µg/L |
| Arsenic | 77 | 9 | 90 | ND-10 |
| Beryllium | 41 | 7 | 40 | 10 |
| Cadmium | 35 | 1 | 10 | NT |
| Chromium | 82 | 44 | 270 | ND-70 |
| Fluoride | 20 | 20 | 550 | NT |
| Lead | 67 | 40 | 290 | 10 |
| Nickel | 110 | 42 | 210 | ND-140 |
| Nitrate | 35 | 34 | 21,800 | NT |
| Sulfate (dissolved and total) | 70 | 69 | 743,000 | 1,200 |
| Sulfide (dissolved and total) | 63 | 17 | 5,160 | ND |
| Thallium | 9 | 0 | (detection limit = 10) | NT |
| Vanadium | 37 | 30 | 210 | 10-170 |
| Zinc | 122 | 77 | 5,090 | 10-330 |
| Organic Compounds | Number of Off-Site Samples | Number of Off-Site Detects | Off-Site Maximum Concentration in µg/L | Background Range in µg/L |
| Bis(2-ethylhexyl)phthalate | 106 | 13 | 300 | (lab contaminant) |
| Bromodichloromethane | 435 | 2 | 16 | ND |
| Carbon tetrachloride | 438 | 3 | 8 | ND |
| Chloroform | 438 | 6 | 56 | ND |
| 1,2-Dichloroethane | 436 | 1 | 57 | ND |
| 1,1-Dichloroethene | 438 | 2 | 13 | ND |
| 1,2-Dichloroethene1 | 733 | 4 | 18 | ND |
| Methylene chloride | 142 | 1 | 27 | ND |
| Pentachlorophenol | 91 | 1 | 8 (residential detection limit = 50) | ND |
| Tetrachloroethylene | 438 | 1 |
1 |
ND |
| Trichloroethylene | 5,698 | 1,091 |
167,000 |
ND |
| Vinyl chloride | 438 | 2 |
110 |
ND |
| Radioactive Contaminants | Number of Off-Site Samples | Number of Off-Site Detects |
Off-Site Maximum Concentration in pCi/L (Bq/L) |
Background Range in pCi/L (Bq/L) |
| Radon 222 | 3862 | 3842 | 1,855 (68.7) | NA3 |
| Technetium 99 | ~5,000 | 898 |
5,804 (215) |
<25 (<0.93) |
| Uranium 234 | 139 | 80 |
24 (0.9) |
<2 (<0.07) |
| Uranium 235 | 119 | 3 |
3 (0.1) |
<1 (<0.04) |
| Uranium 238 | 140 | 120 |
97 (3.6) |
<2 (<0.07) |
| 1 1,2-Dichloroethene includes data
recorded as 1,2-dichloroethylene, 1,2-dichloroethene-cis, and 1,2-dichloroethene-trans. 2 Source: [45,46,47] 3 Background levels of radon 222 in groundwater vary; they are naturally high in some areas of the country. |
||||
| Key: < = less than; Bq/L = becquerels per liter, µg/L = micrograms per liter; NA = not applicable; ND = not detected; NT = not tested; pCi/L = picocuries per liter | ||||
Table 3 lists 30 off-site groundwater contaminants, their comparison values, and the number of off-site detections above the comparison value. For each contaminant, the table indicates which wells had maximum concentrations exceeding comparison values and presents the range of maximum concentrations in these wells. Residential wells are denoted with an "R" or "RW" well number. Few contaminants were detected in residential wells; however, only a few chemicals were tested for in residential well samples. Therefore, for screening purposes, we assumed that contaminants found in off-site monitoring wells could have been present in residential wells. Table 4 lists 17 groundwater contaminants (out of 47) that are not considered contaminants of concern and explains why we excluded these contaminants from further evaluation.
When a contaminant's maximum concentration exceeded a comparison value, that contaminant was considered a possible contaminant of concern. Other criteria used to select contaminants were (1) the frequency and location of detections (e.g., single detections are not reliable indicators of contaminant presence), and (2) quality and quantity of environmental sampling data (e.g., suspected laboratory contaminants or inappropriate detection levels). For an example of the latter, bis(2-ethylhexyl)phthalate was frequently detected above its comparison value in off-site groundwater samples. This contaminant is not a constituent of the PGDP process operations or waste products, but it is a common constituent of the plastic gloves and sampling equipment used in field sampling. It was detected with similar frequency in on-site, off-site, and background samples. For these reasons, positive detections were interpreted as an artifact of the sampling and laboratory processes. Bis(2-ethylhexyl)phthalate was not selected as a contaminant of concern for this exposure pathway.
Of the 30 off-site groundwater contaminants detected in areas of potential exposure, 15 contaminants either were found at levels of potential health concern or, because of inadequate analysis, could be present at levels of health concern. Fifteen off-site contaminants, for which adequate analyses have been conducted, are not considered contaminants of concern based on contaminant concentrations, distribution, and frequency of detection. The rationale for selection or exclusion is listed in Tables 3 and 4.
Beryllium, cadmium, nickel, sulfate, and zinc each had only one off-site measurement above their comparison values (as shown in Table 3). Beryllium, cadmium, nickel, and sulfate were only detected in wells near the TVA plant and the Ohio River, and no elevated concentrations for these contaminants were measured in the groundwater plumes between the PGDP facility and the TVA plant. Beryllium, nickel, and sulfate are not contaminants of concern in groundwater due to their low overall frequency of detection, their maximum concentrations, and the limited potential for exposure. Cadmium, thallium, pentachlorophenol, and vinyl chloride were selected as contaminants of concern for this exposure pathway, because analytical detection limits were greater than their respective comparison values. Zinc was measured above its comparison value only once off site, but the sample was taken from a residential well; therefore, zinc was selected as a contaminant of concern for this exposure pathway.
Arsenic, chromium, lead, nitrate, vanadium, and TCE were selected as contaminants of concern, because their maximum concentrations in off-site well samples were above their respective comparison values (as shown in Table 3). Maximum concentrations of chromium and vanadium were not above comparison values in the residential wells tested for these contaminants; however, the concentrations were above comparison values in monitoring wells near untested residential wells.
Uranium (as a chemical)(1) was detected in six off-site wells. The uranium concentration exceeded EPA's 1991 proposed maximum contaminant level (MCL)--20 micrograms per liter (µg/L)--in only one well (MW-135; 24 µg/L). Six subsequent analyses of MW-135 all indicated non-detects. Because uranium is rarely detected in off-site wells and the single detection above the MCL was not repeated in subsequent analyses, uranium metal (i.e., uranium as a chemical) is not a contaminant of concern in groundwater. (Note: EPA's National Primary Drinking Water Regulations final rule, published December 7, 2000, has the MCL for uranium as 30 g/L.)
Several of the chemical and radioactive contaminants listed in Table 3 are naturally occurring metals or elements. Some of these (e.g., nickel and vanadium) have background concentrations that exceed comparison values. Four of the five radioactive contaminants in Table 3 are naturally occurring, although process operations at PGDP may have caused groundwater concentrations to be elevated above background levels. However, vanadium and two of the naturally occurring radioactive contaminants (uranium 234 and uranium 238, also called U-234 and U-238) were selected as contaminants of concern for this exposure pathway regardless of their source.
Radon 222 (Rn-222) was detected in most of the wells around PGDP. Radon (a radioactive gas) occurs naturally in groundwater; and its presence may not be related to site activities. Because there is no accepted comparison value for Rn-222 in drinking water, ATSDR converted the groundwater concentration into a potential airborne dose using EPA's recommended procedures for determining potential radon gas concentrations in residential air. According to these calculations, the highest potential air concentrations in a home are less than EPA's recommended action level of 4 picocuries per liter (pCi/L) [49]. Also, using information from a recent article in Radiation Research [50] and the maximum concentration of Rn-222 found in well water, and assuming that a person ingests 2 liters of contaminated water per day, we calculated a whole body committed effective dose:(2) 50 millirems (or 0.5 millisieverts). This is less than a typical background dose from naturally occurring radon. Therefore, Rn-222 was not selected as a contaminant of concern for this exposure pathway.
Maximum concentrations of three other radioactive contaminants, Tc-99, U-238, and U-234, exceed EPA's proposed drinking water standards. Tc-99, U-238, and U-234 were selected as contaminants of concern.
Contaminants of concern in the groundwater exposure pathways are discussed further in the next section. Contaminants that were detected on site and/or off site but were not considered in the initial screening (17 of the original 47 chemicals, compounds, and elements in Table 2) are listed in Table 4 with the reasons why they were not considered. The contaminants listed in Table 4 will not be evaluated further.
Table 3. Groundwater contaminants detected off site,
comparison values, and locations
|
Metals and Inorganic Compounds |
CV1 (CV Source) in µg/L |
Number of Off-Site Detects Above CV | Wells With Detections Above CVs | Maximum Concentration Range in µg/L | Selected as Contaminant of Concern? Why? |
| Arsenic | 3 (Chr.EMEGc) | 9 | MWD-009, -025; MW-121, -143, -150, -192; RW-004, -294; TVA-04 |
7 to 90 | Yes, above CV |
| Beryllium | 20 (Chr.EMEGc) | 1 | MWD-014 | 40 | No, one off-site detection > CV and no exposure |
| Cadmium | 2 (Chr.EMEGc) | 1 | MWD-014 | 10 | Yes, all DLs > CV |
| Chromium | 30 (Chr.RMEGc for hexavalent) 100 (MCL for trivalent) |
28 | MWD-009, -019, -024, -025, -027; MW-121, -123, -125, -127, -133, -134, -138, -141, -142, -149, -153, -192, -194, -195, -199, -200, -201, -202, -234, -235; TVA-27 |
40 to 270 | Yes, above CV |
| Fluoride | 600 (Chr.EMEGc) | 0 | 550 | No, less than CV | |
| Lead | 15 (Action Level) | 16 | MWD-014, -019, -024, -025; MW-121, -123, -200, -202; RW-004, -113, -297; TVA-04, -27 |
20 to 290 | Yes, above CV; also, non-detects have DLs > CV |
| Nickel | 200 (Chr.RMEGc) | 1 | MWD-014 | 210 | No, one off-site detection > CV and no exposure |
| Nitrate (dissolved and total) | 20,000 (Chr.RMEGc) | 2 | RW-156; RW-294 | 21,800 to 29,200 | Yes, above CV |
| Sulfate (dissolved and total) | 500,000 (MCL) | 1 | TVA-25 | 743,000 (dissolved) | No, one off-site detection > CV and no exposure |
| Sulfide (dissolved and total) | 500,000 (MCL) | 0 | 5,160 | No, less than CV | |
| Thallium | 2 (MCL) | All DLs > CV | NA | Lowest residential well DL = 10 | Yes, all DLs > CV |
| Vanadium | 30 (Int.EMEGc) | 24 | MWD-009, -014, -019, -024, -025, -027; MW-121, -123, -125, -142, -149, -153, -194, -195,-199,-200,-202; TVA-04, -27 |
30 to 210 | Yes, above CV |
| Zinc | 3,000 (Chr.EMEGc) | 1 | RW-113 | 5,090 | Yes, single detect in residential well |
| Organic Compounds | CV1 (CV Source) in µg/L |
Number of Off-Site Detects Above CV | Wells With Detections Above CVs | Maximum Concentration Range in µg/L | Selected as Contaminant of Concern? Why? |
| Bis(2-ethylhexyl)phthalate | 6 (MCL) | 11 | MWD-003, -005, -019; MW-121, -125, -133, -143, -191; RW-021; RW-294 | To 300 | No, artifact of collecting and sampling |
| Bromodichloromethane | 100 (MCL) | 0 | 16 | No, less than CV | |
| Carbon tetrachloride | 70 (Int.EMEGc) | 0 | 8 | No, less than CV | |
| Chloroform | 100 (Chr.EMEGc) | 0 | 56 | No, less than CV | |
| 1,2-Dichloroethane | 2,000 (Int.EMEGc) | 0 | 57 | No, less than CV | |
| 1,1-Dichloroethene | 90 (Chr.RMEGc) | 0 | 13 | No, less than CV | |
| 1,2-Dichloroethene (includes cis- and trans-) | 2,000 (Int.EMEGc) | 0 | 18 | No, less than CV | |
| Methylene chloride | 2000 (Chr.EMEGc) | 0 | 27 | No, less than CV | |
| Pentachlorophenol | 10 (Int.EMEGc) | DLs > CV | NA | Lowest residential well DL = 50 | Yes, DLs for residential wells above CV |
| Tetrachloroethylene | 100 (Chr.RMEGc) | 0 | 1 | No, less than CV | |
| Trichloroethylene |
5 (MCL) |
722 |
Many wells | Up to 167,000 | Yes, above CV |
| Vinyl chloride |
0.2 (Chr.EMEGc) |
2 |
MW-97 | 54 to 110 | Yes, above CV and DL for wells in plume above CV |
| Radioactive Contaminants |
CV in pCi/L (Bq/L) |
Number of Off-Site Detects Above CV |
Wells With Detections Above CVs | Maximum Concentration Range in pCi/L (Bq/L) | Selected as Contaminant of Concern? Why? |
| Radon 222 |
None available |
(3093 ) |
Many wells3 | 328 to 1,855 (12.1 to 68.7) |
No, 1,855 pCi/L is equal to or less than 4 pCi/L in home air using EPA's recommended procedures to determine max. in residential air;4 annual dose approx. 50 mrem (0.5 mSv)5 |
| Technetium 99 |
3,790 (140) |
2 |
MW-261 | 5,125 to 5,804 (190 to 215) |
Yes, above CV |
| Uranium 234 |
15; 30 total U6 |
2 |
MW-141, MW-148 | 17 and 24 (0.6 to 0.9) |
Yes, above CV |
| Uranium 235 |
15; 30 total U6 |
0 |
3 (0.1) | No, less than CV--but estimated dose will be added to dose from other uranium isotopes and Tc-99 | |
| Uranium 238 |
15; 30 total U6 |
3 |
MWD-009; MW-141; TVA-14 | 17 to 97 (0.6 to 3.6) |
Yes, above CV |
| 1 Refer to Appendix C for a discussion
of comparison values (CVs). 2 For radioactive contaminants, the CV source is the current and/or proposed EPA Safe Drinking Water Standards [51]. 3 Data collected from 1990, 1991, 1992, and 1993 PGDP Environmental Reports [45,46,47,48]. (Number of detects above 300 pCi/L, EPA's proposed standard) 4 Source: [49] 5 Source: [50] 6 EPA's 1991 proposed Drinking Water Standard, 40 CFR Parts 141 and 142. |
|||||
| Key: Bq/L = becquerels per
liter; DLs = detection limits; Chr.EMEGc = Chronic Environmental Media Evaluation
Guide for children; Chr.RMEGc = Chronic Reference Dose Media Evaluation Guide for children; CV = comparison value; Int.EMEGc = Intermediate Environmental Media Evaluation Guide for children; MCL = EPA's Maximum Contaminant Level; µg/L = micrograms per liter; mSv = millisieverts; mrem = millirems; pCi/L = picocuries per liter |
|||||
Table 4. Groundwater contaminants (on and off site)
excluded from further analysis [44]
| Contaminant | Maximum Concentration (in µg/L) | Number of Detections | Comments |
| Arsenic, dissolved | 20 | 16 | Considered contaminant as total arsenic (non-reproducible results as dissolved) |
| Benzene | 12 | 4 | No off-site detections (only on site) |
| Boron | 1,540 | 34 | No off-site detections (only on site) |
| Cadmium, dissolved | 20 | 7 | Considered contaminant as total cadmium (non-reproducible results as dissolved) |
| Chloromethane | 180 | 4 | No off-site detections (only on site) |
| 2-Chlorophenol | 73 | 1 | Single on-site detection; no off-site detections |
| Chromium, dissolved | 110 | 35 | Considered contaminant as total chromium (non-reproducible results as dissolved) |
| 2,4-Dinitrotoluene | 28 | 1 | Single on-site detection; no off-site detections |
| Lead, dissolved | 80 | 22 | Considered contaminant as total lead (non-reproducible results as dissolved) |
| n-Nitroso-di-n-propylamine | 35 | 1 | Single on-site detection; no off-site detections |
| Nickel, dissolved | 660 | 104 | Considered contaminant as total nickel (non-reproducible results as dissolved) |
| Nitrate, nitrite | 68,600 (on site) | 414 | Considered contaminant as nitrate |
| PCB (Aroclor 1254) | 1 | 1 | Single on-site detection; no off-site detections |
| 1,1,1-Trichloroethane | 16 | 7 | No off-site detections (only on site) |
| Uranium (as a chemical) | 90 | 29 | Not tested off site as chemical (Analyzed as U-234, U-235, and U-238) |
| Vanadium, dissolved | 70 | 15 | Considered contaminant as total vanadium (non-reproducible results as dissolved) |
| Zinc, dissolved | 37,400 | 15 | Considered contaminant as total zinc (non-reproducible results as dissolved) |
| Key: µg/L = micrograms per
liter; PCB = polychlorinated biphenyl; U-234, U-235, and U-238 = uranium 234, uranium 235, and uranium 238 |
|||
ATSDR scientists identified completed and potential human exposure pathways for past, current, and potential future exposure to contaminants of concern in groundwater. In addition, we estimated human exposure doses for contaminants in these exposure pathways. In the public health implications section, we discuss potential health hazards from exposure to contaminants of concern at the estimated doses.
Currently, off-site residents are not being
exposed to groundwater contamination
originating from the PGDP site. Former
residential wells within the northwest and
northeast plumes either are used to monitor
contaminant distributions or have been plugged using procedures approved by EPA and the
Kentucky Department for Environmental Protection [52]. Although contaminated groundwater
from the northwest plume may be discharging into the Ohio River or the portion of Big Bayou
Creek directly adjacent to the Ohio River, the concentrations at those locations do not exceed
comparison values [37]. Therefore, there are no exposure pathways identified for current
exposure to groundwater contaminants from the site.
Prior testing of private wells in the PGDP area revealed contamination by lead. Of the 12 residential wells tested for lead, three were above the EPA action level of 15 µg/L [53,54,45,46,47,48]. One of these wells was at a horse barn and was not a private residence's primary drinking water source. Lead found in these wells may not originate from the PGDP site; lead contamination may have resulted from materials used in plumbing. The wells are no longer used as a source of drinking water, but if the lead originated in plumbing that is still being used, the source and exposure pathway for lead exposure may still exist. Persons who are concerned about the possibility of lead contamination in their drinking water may wish to have their water tested. A list at the end of the community health concerns section of this report provides names and phone numbers for persons to contact at the local health department. Additional information is available from EPA's Safe Drinking Water Hotline at 1-800-426-4791. As a general precaution, EPA recommends running taps for 30 seconds to 2 minutes before using the tap water. Possible adverse health effects from exposure to lead in drinking water are discussed in the public health implications section of this report.
Off-site residential wells in the northeast plume area were plugged or converted to monitoring wells before contaminant concentrations exceeded comparison values. Therefore, no completed exposure pathways are identified for past exposure to contaminants in the northeast plume.
For the northwest plume, TCE and Tc-99 were first detected in four private residential wells in
August 1988. At that time, these were the only contaminants measured in these wells; however,
well samples collected after 1988 indicate
that other contaminants may have been
present in the northwest plume along with
TCE and Tc-99. Arsenic, lead, nitrate, and
zinc were detected in samples from
residential wells after 1988, although they
may not be related to the northeast and
northwest plumes. Therefore, TCE, Tc-99,
arsenic, lead, nitrate, and zinc are
contaminants of concern for past exposure
via completed exposure pathways for
groundwater. Completed exposure pathways are described in Table 5.
Thallium, pentachlorophenol, and vinyl chloride were not detected in off-site residential wells; however, the lowest level of analytical detection exceeded the comparison value. Four other chemicals or metals (cadmium, chromium, fluoride, and vanadium) were detected in monitoring wells at maximum concentrations that exceeded comparison values. Analyses for these contaminants were not performed for most residential well samples. Because residential wells may have contained cadmium, chromium, fluoride, pentachlorophenol, thallium, vanadium, or vinyl chloride, they are contaminants of concern for past exposure via potential exposure pathways. Potential exposure pathways are described in Table 6.
Two radioactive contaminants, U-234 and U-238, were detected in off-site monitoring wells. The samples were collected in the deep RGA. Maximum concentrations exceeded EPA's drinking water standard. Although these results were not repeated and these contaminants were not detected in residential wells, U-234 and U-238 were detected in on-site groundwater and are considered contaminants of concern for past exposure via potential exposure pathways for groundwater. (Refer to Table 6.)
After the initial discovery and mapping of the northeast and northwest plumes, an additional groundwater contaminant plume, called the southwest plume, was identified from new source characterization and monitoring wells. The current mapped distribution of the southwest plume is largely inside the fenced security area on the west side of the plant property and entirely within the DOE property boundary. There are no residential drinking water wells within the past or current area of the southwest plume. Therefore, there are no exposure pathways identified for past or current exposure to contaminants in the southwest plume.
Because sampling and analysis data are not available for times before 1988; therefore, ATSDR scientists used measurements of TCE migration rates for 1988 through 1995 to estimate the duration of past exposure to groundwater contaminants.
Figures 5 and 6 show the concentrations of TCE and Tc-99 in four residential wells by year, beginning in 1988, when monitoring began. These wells were likely to have been contaminated with TCE above the comparison value (5 µg/L) before 1988. Evaluation of contaminant transport rates indicate that TCE concentrations were estimated to be greater than 100 µg/L for 5 to 15 years prior to 1988. Concentrations less than 100 µg/L may have been present in these wells for a longer period; however, that period's duration cannot be estimated with certainty. Therefore, we assumed an exposure duration of 5 to 15 years for all contaminants in the wells associated with the northwest plume. In evaluating contaminant transport, we assumed a concentration of 100 µg/L--but this is not a health-based concentration. Appendix D details the evaluation of contaminant migration and presents supporting information.
Past exposure doses for contaminants of concern in completed and potential exposure pathways are estimated using assumptions about who may have been exposed, how they may have been exposed, how long their exposures lasted, and how often they were exposed. We assumed that ingestion was the primary route of exposure for this exposure pathway, although inhalation and skin contact for some contaminants were secondary exposure routes. Studies have shown that volatile organic compounds released from water to air during showering or bathing can produce, through inhalation, a dose that is 50% to 90% as large as the dose through ingestion [55,56]. Absorption of these contaminants through the skin can contribute a dose up to 30% of the ingested dose [57]. As a conservative estimate, ATSDR scientists assumed that ingestion doses for volatile organic compounds, TCE, and vinyl chloride would increase 70% from inhalation and 30% from dermal absorption.
ATSDR scientists estimated doses to adults and children. Exposures are estimated for a 1- to 6-year-old child who weighs 13 kilograms and ingests 1 liter of water daily and for an adult who weighs 70 kilograms and drinks 2 liters of water daily at the maximum detected concentration.
Except for TCE, Tc-99, U-234, and U-238, the maximum off-site concentrations of the contaminants in groundwater were used to calculate exposure doses. Exposure doses for TCE and Tc-99 were based on maximum concentrations measured in 1988 at the most contaminated drinking water well (960 µg/L for TCE and 400 pCi/L for Tc-99). For U-234 and U-238, the exposure doses were based on maximum concentrations measured in MW-141 (24 pCi/L for both U-234 and U-238). Tables 5 and 6 show maximum estimated exposure doses for contaminants in completed and potential exposure pathways.
Potential future exposure pathways exist for contaminants in the northeast and northwest plumes, and possibly the McNairy Aquifer and the southwest plume.
For the northeast plume, the primary contaminant of concern is TCE. Also, chromium has recently been detected in several wells northeast of the site property. Although other contaminants (such as Tc-99 and arsenic) have been detected in the northeast plume, they have not migrated off site at concentrations exceeding health comparison values. The northeast plume is migrating to the northeast and is close to the eastern boundary of the Water Policy-affected area (Metropolis Lake Road), as Figure 7 shows. Although a groundwater extraction and treatment system was established for this plume in August 1997, contaminants at the leading edge may migrate beyond Metropolis Lake Road in the future. If the plume continues to migrate, it may contaminate additional private water wells before it discharges into the Ohio River.(3) DOE is continuing to monitor the movement of the northeast plume. DOE has indicated that they will expand the boundaries of the Water Policy area if ongoing monitoring indicates that additional wells may become contaminated [36]. If the plume migrates outside the water policy boundary and contaminated wells are capped using approved procedures, no exposure will occur.
Residents who have been provided with municipal water have agreed not to drill additional wells; however, new residents or new landowners in the area are not restricted from drilling new wells within the area of groundwater contamination. Therefore, there is a potential for future exposure if new wells are drilled into the northeast or northwest contaminant plumes.
The southwest plume was recently characterized. There is no current completed exposure pathway for this plume. Its future migration direction is unknown. The plume may turn north and join with the northwest plume.
The McNairy Aquifer also represents a potential source for future human exposure. Low concentrations of groundwater contaminants have been detected in the McNairy Aquifer. Subsequent northward transport to the Ohio River or under the river to water supply wells in Illinois presents a limited potential for exposure. In order for this exposure pathway to be completed, contaminants must migrate from the RGA into the McNairy Aquifer and then flow under the Ohio River to public supply wells. TCE and Tc-99 have been detected in McNairy wells (TCE in MW-114, MW-121, and MW-128; Tc-99 in all wells, including the background well MW-140). Contaminant concentrations are low: one TCE sample was above the comparison value (the sample had TCE at a concentration of 9 µg/L). According to available data, the well from which this sample was taken (MW-114) has not been re-sampled.
Continued monitoring of contaminants in the northeast, northwest, and southwest plumes is necessary until these flow systems are well defined and the effects of the extraction and treatment systems or other remedial techniques are known. ATSDR will re-evaluate this exposure pathway if future monitoring results indicate a potential for human exposure to groundwater contaminants.
DOE contractors are currently performing pilot studies for various technologies that might be able to remediate the groundwater aquifer. Several options and combinations of options have been presented to the public, along with estimated costs and timeframes [42]. No matter what options are chosen, the remediation will probably take a very long time.
Figure 5. TCE Concentrations in Residential Wells
Figure 6. Tc-99 Concentration in Residential Wells
 Figure 7. TCE and Tc-99 Groundwater Contamination, 1997 (jpg) |
Figure 7. TCE and Tc-99 groundwater contamination, 1997 (pdf) |
Table 5. Summary of contaminants of concern and exposure
doses in completed exposure pathways for off-site groundwater
| Major Sources | Contaminants | Exposure Point | Exposure Route | Exposed Persons | Period of Time and Duration | Maximum Estimated Exposure Doses 1 |
| Leaching of contaminants from disposal practices, accidental releases or spills, and buried waste materials to the Regional Gravel Aquifer | TCE2 (960 µg/L) |
Residential wells drilled into northwest plume in RGA | Ingestion (TCE includes inhalation and skin absorption) | Children and adults using RW-002, RW-017, and RW-113 (RW-004 at horse barn) | Past only 5 to 15 years chronic exposure ending in 1988 |
TCE:2 Children 0.148 mg/kg/d Adults 0.055 mg/kg/d |
| Tc-992 (400 pCi/L) |
Tc-99:2 (for annual intake)
Children 1.2 mrem (0.012 mSv) | |||||
| Arsenic | Two residential wells | Ingestion | Children and adults using RW-294 (RW-004 at horse barn) | Past only Wells no longer in use; exposure duration unknown |
Arsenic:3 Children 0.001 mg/kg/d Adults 0.0003 mg/kg/d |
|
| Lead | Residential wells northwest of site | Ingestion | Children and adults using RW-113 and RW-297 (RW-004 at horse barn) | Past Wells no longer in use; exposure duration unknown; see Table 6 |
Lead: Children 0.009 mg/kg/d Adults 0.003 mg/kg/d (RW-004) | |
| Nitrate | Three residential wells | Ingestion | Children using RW-002, RW-030, and RW-294 | Past only Wells no longer in use; exposure duration unknown |
Nitrate: Children 1.69 mg/kg/d Adults 0.63 mg/kg/d |
|
| Zinc | One residential well | Ingestion | Children and adults using RW-113 | Past Well no longer in use; exposure duration unknown |
Zinc: Children 0.392 mg/kg/d Adults 0.145 mg/kg/d |
|
| 1 In calculating exposure doses,
ATSDR assumed 13 kg body weight and 1 liter water per day for children and
70 kg body weight and 2 liters water per day for adults. ATSDR used dose
conversions from ICRP 72 [58]. 2 TCE and Tc-99 exposure doses based on maximum measured concentrations in residential wells for 1988. 3 Doses based on detections in residential wells. |
||||||
| Key: µg/L = micrograms per
liter; mg/kg/d = milligrams contaminant per kilogram body weight per day
(exposure unit used for chemicals); mrem = millirems (unit used for radiation exposure); mSv = millisieverts (1 mSv = 100 mrem); pCi/L = picocuries per liter; Tc-99 = technetium 99; TCE = trichloroethylene |
||||||
Table 6. Summary of contaminants of concern and exposure doses in potential exposure pathways for off-site groundwater
| Major Sources | Contaminants | Point of Exposure | Route of Exposure | Exposed Population | Period of Time and Duration | Maximum Estimated Exposure Doses1 |
| Leaching of contaminants from multiple on-site sources described in Table 1 | Arsenic
Cadmium Chromium Thallium Vanadium Pentachloro- Vinyl Uranium 234 Uranium 238 |
Residential wells northwest, north, and northeast of site | Ingestion | Children and adults living in houses in these areas with drilled wells | Potential past and future | Arsenic: Children 0.007 mg/kg/d Adults 0.003 mg/kg/d Cadmium: Chromium: Children 0.021 mg/kg/d Thallium: Vanadium: Pentachlorophenol: Children 0.0039 mg/kg/d Vinyl chloride: Children 0.017 mg/kg/d Uranium 234 (for annual intake): Children 2.9 mrem (0.029 mSv) Uranium 238 (for annual intake): Children 2.6 mrem (0.026 mSv) |
| Lead2 | Residential wells north and northwest of site | Ingestion | Potential current and future | See text | ||
| For northeast Plume: Building C-745, underground storage tanks, southside cylinder yard, construction facility, historical staging area |
TCE and potentially Tc-99 |
Eight residential wells drilled east of Metropolis Lake Road, north of McCaw Road, south of Ohio River | Ingestion (also, for TCE, inhalation and skin absorption during showering) | Households and visitors to about eight residences | Potential future | Future potential doses were not estimated. |
| For McNairy Aquifer: leaching of contaminants from Regional Gravel Aquifer |
TCE Tc-99 |
Public water supply wells north of Ohio River | Ingestion (also, for TCE, inhalation and skin absorption during showering) | Anyone using public water supply | Potential future | Future potential doses were not estimated |
| For northeast and northwest plumes: leaching of contaminants from multiple on-site sources described in Table 1 |
TCE Tc-99 |
New wells drilled into existing northeast and northwest plumes | Ingestion (also, for TCE, inhalation and skin absorption during showering) | Persons using new wells for residential purposes | Potential future | Future potential doses were not estimated. |
| 1 For calculating exposure doses,
ATSDR assumed 13 kg body weight and 1 liter water per day for children,
and 70 kg body weight and 2 liter water per day for children. Maximum estimated
exposure doses are based on maximum concentrations reported for off-site
monitoring wells. 2 Lead may not be related to PGDP or the northwest plume: it may be related to pluming materials. |
||||||
| Key: mg/kg/d = milligrams
contaminant per kilogram body weight per day (exposure unit used for chemicals);
mrem = millirems (unit used for radiation exposure); mSv = millisieverts (1 mSv = 100 mrem); Tc-99 = technetium 99; TCE = trichloroethylene |
||||||
PGDP operations and waste disposal activities have resulted in airborne releases of radioactive and chemical compounds. ATSDR scientists reviewed PGDP processes that produce air contaminant releases, selected contaminants of concern, identified potentially exposed populations, and evaluated exposure to those populations. Determination of contaminants of concern is based largely on information about process operations and accidents that produce air contamination, release information, data reported from the perimeter fence and off-site air monitors, and air dispersion modeling. Descriptions of air dispersion models used to evaluate air releases from the PGDP facility are included as Appendices E through H.
Contaminant
releases to the atmosphere at PGDP occur or have occurred as a result of primary
operations/processes and accidental releases. These processes include (1) uranium
hexafluoride (UF6) enrichment and handling, (2) uranium fluoride
manufacturing, (3) metal finishing and grease removal, (4) releases from the
water cooling towers, and (5) generation of electricity by the coal-fired steam
plant. Other process releases are caused by secondary operations, such as groundwater
treatment and cylinder maintenance (cleaning and painting cylinders). Each operation
is a source of specific air contaminants; one can determine which contaminants
an operation produces by estimating material usage or loss. (Refer to Figure
2 for locations of facilities on site.) Table 7 lists contaminants released to
the air from processes at the PGDP site, maximum annual releases with the year
of release, and major operations or release points. Contaminant sources or release
points that no longer exist are noted in the table.
During the uranium enrichment process, UF6 is released to the atmosphere mainly through vents in the process buildings and through a 61-meter stack at Building C-310 [60]. These releases occur primarily during the transfer of the gaseous UF6 from the cascade equipment into the storage cylinders. UF6 is the primary contaminant released in this process. Once released into the air, UF6 reacts rapidly with atmospheric water to form hydrogen fluoride (HF) gas, uranyl fluorides, and uranium oxides [61]. The year in which the most uranium was released was 1956 [12]. Better filtration and operational procedures reduced the total air release of uranium in 1977 to less than one-tenth the release in 1956. (Refer to Table 8A.) Also, major modifications were made to the C-310 stack in 1983 to reduce uranium emissions further [62].
Large quantities of uranium and fluoride were released from 1952 until 1977, when UF6 was produced from uranium oxides at the feed plant (Building C-410) and when UF6 was converted to uranium tetrafluoride (UF4) at the metals plant (Building C-340). Most airborne uranium during these years originated at the Feed Plant, where UF6 was produced from uranium oxide [63].
Table 7. Airborne releases (from PGDP processes) and
major release sources [40,7]
| Air Contaminants | Maximum Reported Annual Release (Year) | Major Release Sources |
| Hexavalent chromium | 1,700 kg (1990) | Cooling towers |
| Fluorine Fluoride Hydrogen fluoride |
(See Appendix F) | Plant operations (includes building vents, seal exhaust/wet exhaust, product/tail withdrawals, and laboratory hoods); C-310 stack emissions; U metals plant (past); C-400 UF4 pulverizer (past); C-410 HF storage and production areas (past) |
| Sulfur dioxide Nitrogen oxides |
399,579 kg (1993) 314,400 kg (1985) |
PGDP's coal-burning steam plant |
| Trichloroethylene | 62,826 kg (1986) | C-400 and C-720 degreasing operations, and spills (past); northeast and northwest water treatment facilities |
| Technetium 99 | 6.3 Ci (233.1 GBq) |
Plant operations (includes building vents, seal exhaust/wet exhaust, product/tail withdrawals, and laboratory hoods); C-310 stack emissions; U metals plant (past); C-400 spray booths, rotary vacuum dissolver, laundry, cylinder drying station |
| Uranium 234 Uranium 235 Uranium 238 |
1.62 Ci (59.9 GBq) 0.08 Ci (2.96 GBq) 3.50 Ci (130 GBq) |
Plant Operations (includes building vents, seal exhaust/wet exhaust, product/tail withdrawals, and laboratory hoods); C-310 stack emissions; U metals plant (past); C-400 spray booths, rotary vacuum dissolver, laundry, cylinder drying station; C-400 UF4 pulverizer (past) |
| Key: Ci = curies; GBq = gigabecquerels; kg = kilograms; HF = hydrogen fluoride; U = uranium; UF4 = uranium tetrafluoride | ||
In addition to ongoing operational contaminant releases, accidental releases of UF6 and HF have occurred throughout the operating history of the plant. The largest reported accidental release occurred in 1960, when a cylinder ruptured inside Building C-333 as a result of overfilling and released 17,800 pounds (8,074 kilograms) of UF6. Another major accident occurred in December 1962 during a fire in Building C-337; in that accident, 5,062 pounds (2,296 kilograms) of UF6 were released. There have been several other accidents, but these have involved much smaller quantities [64]. Refer to Appendices E and F for further details.
Also, four deliberate releases of UF6 were made as part of experiments to model the behavior of atmospheric releases of UF6 [59]. There were two releases in 1955 and two releases in 1974; the 1955 releases involved 4.4 kilograms and 0.68 kilograms (10 pounds and 1.5 pounds) of UF6, and both 1974 releases involved about 0.16 kilograms (0.4 pounds).
Fluoride releases were not reported for most of the years of operation. From 1955 until 1993, the Atomic Energy Commission, DOE, and their contractors used off-site air monitors to detect airborne fluorides, uranium, and beta-emitters in the surrounding environment [65]. A continuous stack sampler for HF was installed in the C-310 stack; however, the reviewed reports do not indicate when it was installed or how much fluoride was released before 1985. Starting in 1985, total annual releases of HF were reported in the annual reports. Fluoride releases from the C-310 stack and sulfur dioxide releases from the C-600 steam plant were sampled continuously until 1993. Other emissions from plant operations were intermittently sampled. The majority of the releases were determined by material balancing or engineering calculations using emission design factors from EPA's Compilation of Air Pollutant Emission Factors (cited in 40 CFR 61, Subpart H, Appendix D) and coal content information provided by the coal supplier [46].
Most of the uranium used at PGDP was extracted from uranium ore and shipped to PGDP as uranium oxide. However, from 1953 to 1975, some reprocessed uranium, which contained traces of other radioactive materials, was fed into the cascade system [4]. The other radioactive materials included technetium 99 (Tc-99), thorium 230 (Th-230), neptunium 237 (Np-237), and plutonium 239 (Pu-239). Significant quantities of Tc-99 were released to the air as early as 1953, with the largest annual release occurring in 1958 [12]. Several reports and studies, from as early as 1957, describe operational problems caused by these other radioactive materials, especially neptunium and plutonium [66,67,68,69,70]. Airborne releases of Th-230, Np-237, and Pu-239 were not reported in the annual environmental reports until the 1990s. These materials were released in much less quantity than Tc-99. (Refer to Table 8B.) These constituents in the reprocessed uranium were in very low concentrations when the material was received and mostly concentrated in the flame tower ash during the manufacturing of UF6.
PGDP also has operated two vapor degreasers in Building C-400 and one in Building C-720 for metal cleaning and degreasing. Two systems used trichloroethylene (TCE) and one used 1,1,1-trichloroethane (1,1,1-TCA) as organic solvents and degreasers. Both chemicals vaporize or evaporate readily, so PGDP assumed that 90% of the TCE and 1,1,1-TCA was released to the atmosphere [47]. Use of TCE and 1,1,1-TCA was discontinued in 1993; therefore, ATSDR scientists evaluated only past airborne exposures from these sources. Operation of the Northwest and Northeast Groundwater Treatment Systems (beginning in 1995 and 1997, respectively) has also resulted in small releases of TCE to the atmosphere.
PGDP uses four recirculating water cooling systems to dissipate heat generated by the diffusion process. Moisture in the air flow (drifts) from PGDP's cooling towers contains elements found in these recirculating water systems. These elements come from chemicals used as corrosion inhibitors, algicides, etc.; the corrosion inhibitor used at PGDP until 1993 was a chromate-zinc-phosphate compound. Of the contaminants released from the cooling towers, the two with the greatest potential environmental impact are hexavalent chromium and zinc. These were investigated by Oak Ridge National Laboratory in 1978 [71]. At that time, the hexavalent chromium was detected on vegetation and in the soil at a distance of about 0.9 miles (1,500 meters) from the cooling towers (extending outside the PGDP boundary). We do not have the release quantities for hexavalent chromium before 1988, so we cannot compare releases in 1978 with quantities seen in the off-site environment in 1978. Available data indicate that the highest annual quantity was released in 1992. In 1993, use of the chromium-zinc-phosphate anti-corrosion compound was discontinued [47].
PGDP operates a coal-burning steam plant to provide steam and generate supplemental electricity. In 1974 and 1975, two of the three boilers at the steam plant were converted to burn low-sulfur coal and oil instead of natural gas. Electrostatic precipitators with 97% efficiency for the capture of particulates were installed [47]. One boiler continues to use natural gas and oil. PGDP reports releases of sulfur dioxide, nitrogen oxides, particulates, carbon monoxide, non-methane volatile organic compounds, and methane. Sulfur dioxide was continuously monitored at the steam plant stacks from 1979 until 1993 [72]. The reported results were based on the quantity released per unit of heat (BTU) produced or total released for the year. Other emissions were calculated from fuel usage and emission factors [46]. Annual releases have been reported in DOE's annual reports for 1985 through 1993. No off-site air monitoring for sulfur dioxide and nitrogen oxides has been performed near the PGDP site.
Release quantities in Tables 8A and 8B were estimated by DOE, their predecessors, or their contractors, mainly through material balance records or by engineering calculations. Values listed with "est." in Table 8A are estimated by ATSDR using available information. Table 8A includes annual estimated release quantities for uranium and Tc-99. Table 8B includes annual estimated releases of other radioactive materials and chemicals from 1985 through 1996.
Table 8A. Annual estimated release quantities of uranium
and technetium 99 from process operations at PGDP for 1952 through 1993 and
1996 [12,65,4]
| Year |
U (in kg)
|
U (in Ci)
|
U-234 (in Ci) | U-235 (in Ci) | U-238 (in Ci) | Tc-99 (in Ci) |
| 1952 |
30
|
0.02
|
|
|
|
|
| 1953 |
500
|
0.25
|
|
|
|
|
| 1954 |
4,800
|
2.4
|
|
|
|
|
| 1955 |
8,400
|
4.2
|
|
|
|
|
| 1956 |
10,500
|
5.2
|
|
|
|
|
| 1957 |
3,900
|
2.4
|
|
|
|
|
| 1958 |
3,500
|
2.2
|
|
|
|
|
| 1959 |
3,300
|
2.1
|
|
|
|
|
| 1960 |
3,000
|
2.0
|
|
|
|
|
| 1961 |
3,600
|
2.4
|
|
|
|
|
| 1962 |
2,400
|
1.3
|
|
|
|
|
| 1963 |
2,400
|
1.3
|
|
|
|
|
| 1964 |
900
|
0.6
|
|
|
|
|
| 1965 |
20
|
0.02
|
|
|
|
|
| 1966 |
30
|
0.02
|
|
|
|
|
| 1967 |
20
|
0.02
|
|
|
|
|
| 1968 |
600
|
0.3
|
|
|
|
|
| 1969 |
1,800
|
1.0
|
|
|
|
|
| 1970 |
900
|
0.5
|
|
|
|
|
| 1971 |
1,200
|
0.7
|
|
|
|
|
| 1972 |
1,200
|
0.7
|
|
|
|
|
| 1973 |
1,400
|
0.8
|
|
|
|
|
| 1974 |
1,100
|
0.6
|
|
|
|
|
| 1975 |
1,100
|
0.7
|
|
|
|
|
| 1976 |
1,500
|
1.0
|
|
|
|
|
| 1977 |
610
|
0.4
|
|
|
|
|
| 1978 |
96
|
0.06
|
|
|
|
|
| 1979 |
48
|
0.03
|
|
|
|
|
| 1980 |
22
|
0.02
|
|
|
|
|
| 1981 |
140
|
0.06
|
|
|
|
|
| 1982 |
300
|
0.14
|
|
|
|
|
| 1983 |
11
|
0.0045
|
|
|
|
|
| 1984 |
3.2
|
0.0019
|
|
|
|
|
| 1985 |
4.4
|
3.7E-03
|
|
|
|
|
| 1986 |
0.79
|
3.6E-04
|
|
|
|
|
| 1987 |
<1.0
|
2.9E-04
|
|
|
|
|
| 1988 |
0.14
|
0.6E-04
|
|
|
|
|
| 1989 |
0.2
|
2.9E-04
|
|
|
|
|
| 1990 |
0.03
|
3.37E-05
|
|
|
|
|
| 1991 |
0.005
|
6.63E-06
|
|
|
|
|
| 1992 |
1.42
|
2.12E-03
|
|
|
|
|
| 19931 |
3.06
|
3.19E-03
|
|
|
|
|
| 1996 |
-----
|
4.37E-03
|
|
|
|
|
| 1 Uranium and uranium isotope values reported for 1993 were not consistent in the annual environmental report; maximum values were used. | ||||||
| Key: Ci = curies; kg = kilograms; est. = estimated; U = uranium; U-234, U-235, and U-238 = uranium 234, uranium 235, and uranium 238; Tc-99 = technetium 99 | ||||||
Table 8B. Annual estimated release quantities of major
airborne contaminants other than uranium and technetium 99 for 1985 through
1993 and 1996 [65,4]
| Year | Np-237 (in Ci) |
Pu-239 (in Ci) |
Th-230 (in Ci) |
Fluoride (in kg) |
Hexavalent Chromium (in kg) |
TCE (in kg) |
SO2 (in kg) |
NOx (in kg) |
| 1985 | ** | ** | ** | 5,268 | ** | 38,652 | 212,400 | 314,400 |
| 1986 | ** | ** | ** | 6,464 | ** | 62,856 | 176,575 | 262,800 |
| 1987 | ** | ** | ** | 7,100 | ** | 34,400 | 178,700 | 252,900 |
| 1988 | ** | ** | ** | 6,844 | 870 | 47,900 | 188,103 | 256,800 |
| 1989 | ** | ** | ** | 6,801 | 1,500 | 41,000 | 292,309 | 282,380 |
| 1990 | ** | ** | ** | 5,750 | 1,700 | 28,000 | 276,380 | 278,613 |
| 1991 | ** | ** | ** | 5,722 | 1,520 | 17,205 | 317,922 | 256,234 |
| 1992 | 3.8E-07 | 2.4E-06 | 2.7E-07 | 6,547 | 2,015 | 10,221 | 388,648 | 258,696 |
| 1993 | 2.1E-08 | 4.8E-06 | 5.9E-06 | 3,778 | 860 | 16,000 | 399,579 | 269,265 |
| 1996 | 2.7E-06 | 2.3E-06 | 2.1E-06 | ** | ** | 1,271 (DOE only) | ** | ** |
| ** Quantities were not reported in the documents reviewed. | ||||||||
| Key: Np-237 = neptunium 237; Pu-239 = plutonium 239; Th-230 = thorium 230; TCE=trichloroethylene; SO2 = sulfur dioxide; NOx = nitrogen oxides; Ci = curies; kg = kilograms | ||||||||
Since 1993, when the U.S. Enrichment Corporation (USEC) became responsible for the process facilities, DOE has not reported process release information or off-site air monitoring data. DOE retains responsibility for four sources of air emissions. The sources are the Northwest Groundwater Treatment Facility, the C-337 Cooling Tower (as part of the Northeast Groundwater Treatment System), the cylinder refurbishment operations, and two separate fluorescent lamp crushers [73]. The groundwater treatment systems released approximately 2 tons of TCE in 1997. Only the cylinder refurbishment operations require a permit from the Kentucky Division of Air Quality (KDAQ); these operations are the largest current source of non-radioactive air emissions [73]. Sandblasting of UF6 cylinders produced an estimated 4.5 tons of particulates or dust in 1996 [1] and approximately 5 tons in 1997 [73]. Cylinder painting operations released up to 3.4 tons of volatile organic compounds in 1996 [1] and 3.5 tons in 1997 [73]. These sources are classified as minor sources of hazardous air pollutants under the Clean Air Act, because they have limited potential for public health effects. DOE is also responsible for four empty TCE tanks. DOE has no plans to use these tanks at this time [73].
In 1988 and 1989, KDAQ cited PGDP for excessive dust emissions from the C-726 sandblasting facility [53,54]. The facility was shut down in May 1989. PGDP planned to install a dust collection filter system and return the facility to use, but the facility never re-opened.
Each release of a contaminant to the air represents a potential human exposure. ATSDR scientists used information about contaminant releases to identify and select possible contaminants of concern for air exposure pathways. Contaminant concentrations in off-site areas are used to determine contaminants of concern. Additional criteria used to select contaminants of concern were (1) maximum concentrations exceeding media-specific comparison values, (2) toxicity and radioactivity, and (3) community concerns. Modeling was used to estimate off-site air concentrations for those contaminants that did not have adequate off-site air monitoring. We compared modeling results to ambient air monitoring measurements, when possible, in order to evaluate the accuracy of model predictions.
In estimating the airborne release concentrations and the potential exposure doses for radioactive materials other than uranium and Tc-99, we assumed that process operations released these materials into the air in the same proportion to uranium as in the materials shipped to Paducah from other DOE facilities. Actually, most of these radioactive materials are removed in the ash residue when UF4 is converted to UF6. About 25% of the neptunium and trace amounts of the plutonium are converted to hexafluoride compounds and processed with the UF6. Under the original, conservative assumption, the contribution to the dose estimates from radioactive materials other than uranium and Tc-99 would be at least an order of magnitude smaller than the contribution from uranium isotopes, and would not add significantly to the dose estimates [68].
Zinc was released from the cooling tower with chromium. Zinc concentrations in foliage were studied at Oak Ridge Gaseous Diffusion Plant (ORGDP), where zinc and chromium concentrations were a little higher than at PGDP [74]. Beyond 660 feet (200 meters) from the base of the ORGDP cooling towers, zinc could not be differentiated from background levels. At PGDP, 660 feet from the base of the cooling towers would still be on site. Also, a study of mature tree cross sections showed that the zinc emissions were uniform over the past 20 years of cooling tower operations. This indicates that off-site air concentrations have not changed significantly. Based on the estimated quantities of zinc emissions and the probability that zinc would not be seen off site at PGDP, zinc was not selected as a contaminant of concern.
Lastly, 1,1,1-TCA was not selected as a contaminant of concern, because the small quantity released to the atmosphere would not produce adverse health effects off site.
ATSDR scientists used computer modeling to predict chronic and acute off-site concentrations of several contaminants known to be released from the PGDP site. These include uranium isotopes, Tc-99, uranium (as a chemical), HF, TCE, sulfur dioxide, nitrogen oxides, and hexavalent chromium. For chemical contaminants, maximum off-site concentrations were compared to media-specific comparison values to determine whether the contaminants should be selected as contaminants of concern for the air exposure pathways. For radioactive contaminants, ATSDR scientists estimated total committed effective doses.
Uranium Isotopes and Technetium 99
Historically, the PGDP site has released uranium isotopes (primarily U-234, U-235, and U-238) and Tc-99 into the air. ATSDR scientists evaluated off-site exposures (committed effective doses) to airborne radioactive materials using the Clean Air Act Assessment Package-1988 (CAP88-PC) [75,76]. This computer model was developed by EPA for assessing regulatory compliance with EPA's National Emission Standards for Hazardous Air Pollutants (NESHAP). The model has a number of adjustable parameters, which are discussed in Appendix E. Annual committed effective doses were based on air emissions of U-234, U-235, U-238, and Tc-99, and were calculated for chronic exposures using data from the highest-release years (1956, 1957, 1958, and 1959) and from 1996 (a recent year for which we have complete information). These estimated chronic doses (shown in Table 9) were calculated for the maximally exposed individual (the closest resident downwind, about 0.9 miles--1,500 meters--north of the source; CAP88 assumes the source is in the center of the site [29]). The total estimated annual committed effective doses for 1960 through 1963 were also calculated; these were between 100 and 150 millirems per year (1.0 to 1.5 millisieverts per year). The estimated committed effective dose from other constituents in reprocessed uranium could add up to 10% to these total doses.
The total estimated annual committed effective doses, shown in Table 9, were not compared to doses calculated from ambient air monitoring data: the air monitoring stations were located at the security fence perimeter, whereas the doses in Table 9 are estimated for the closest downwind residence--again, approximately 1,500 meters north of the fence. Both calculations result in potential exposures greater than 10 millirems per year, the current NESHAP emission standard for radionuclides (40 CFR 61). Therefore, these radionuclides were selected, as a group, as contaminants of concern for the air exposure pathway.
For acute (short-term) exposure, the highest estimated off-site exposure occurred when a cylinder ruptured in Building C-333 at 4:00 a.m. on November 17, 1960. According to our modeling of this accident (refer to Appendix E), an estimated uranium inhaled dose of 1.5 rems (0.015 sieverts) could have been received by the maximally exposed resident southeast of the site. Therefore, the uranium isotopes were selected as contaminants of concern for the air exposure pathway.
Table 9. Off-site estimated annual committed effective
doses from uranium 234, uranium 235, uranium 238, and technetium 99 air releases
from PGDP to the maximally exposed individual (approximately 1,500 meters north
of the source)1
| Year | Releases in curies (gigabecquerels) | Total estimated annual committed effective dose2 from releases in millirems (millisieverts) [58] | |||
| U-234 | U-235 | U-238 | Tc-99 | ||
| 1956 | 1.62 (59.9) | 0.08 (2.96) | 3.50 (129.5) | 2.6 (96.2) | 340 (3.40) |
| 1957 | 1.10 (40.7) | 0.05 (1.85) | 1.20 (44.4) | 4.8 (177.6) | 156 (1.56) |
| 1958 | 1.09 (40.3) | 0.05 (1.85) | 1.16 (42.9) | 6.3 (233.1) | 147 (1.47) |
| 1959 | 0.93 (34.4) | 0.04 (1.48) | 1.10 (40.7) | 5.1 (188.7) | 132 (1.32) |
| 1996 | 2.9E-03 (0.107) |
1.2E-04 (0.044) |
1.4E-03 (0.052) |
3.6E-02 (1.332) |
0.43 (0.0043) |
| 1 Predominant wind direction from
south-southwest. 2 Estimated using the Clean Air Act Assessment Package-1988 (CAP-88-PC) [76]. |
|||||
| Key: U-234 = uranium 234; U-235 = uranium 235; U-238 = uranium 238; Tc-99 = technetium 99 | |||||
Accidental uranium releases were also evaluated for uranium as a chemical--that is, based on its chemical toxicity as a heavy metal, not its radioactivity. Only one reported accident (same as above) could have caused significant off-site uranium exposures: an accident at Building C-333 at 4:00 a.m. on November 17, 1960. According to estimated exposures from modeling this accident (see Appendix E), the highest potential dose of inhaled uranium was 5 to 20 milligrams (mg) for residents living southeast of the site, 0.9 to 2.5 miles (1,500 to 4,000 meters) from Building C-333. The U.S. Nuclear Regulatory Commission's action level for intake of soluble uranium is 10 mg. (At this action level, residents may be instructed to evacuate or to stay indoors with windows closed.) Uranium as a chemical contaminant was selected as a contaminant of concern for the air exposure pathway.
HF (including fluoride and fluorine) was released at the PGDP site. This contaminant is also a noted community concern. Although fluoride emission data from the plant are limited, there is a strong correlation between uranium and fluoride releases, and there is historical information on uranium releases. Current fluoride releases are much smaller than past releases, because process and filtration equipment have changed and chemical manufacturing at the PGDP facilities has been discontinued.
Fluoride releases from the plant were not reported in annual reports until 1986. Results from off-site air monitoring were reported in the annual environmental reports from 1958 until 1993. However, results for each monitoring location and sampling period were not reported. For the first 3 years, the median value for all off-site air concentrations was reported. From 1961 until 1993, the mean values for each year were reported [65].
Because there is a strong correlation between uranium releases and ambient air concentrations of HF, ATSDR scientists assumed that the largest chronic HF release coincided with the highest annual uranium release in 1956. To evaluate off-site HF exposures for 1956, one must estimate or model HF emissions from periods of consistent data reporting when the processes on site were similar (e.g., 1962 through 1970). The method we used is discussed in Appendix F.
For chronic HF exposures, the maximally exposed individual is assumed to be at the perimeter north air monitoring station. This station is closer to the fluoride processing facility than others [65], and is downwind of the processing facility with respect to prevailing south-southwest winds [1]. Kentucky's ambient air standard for average annual exposure is 500 parts per billion (ppb) [77], and ATSDR's provisional guidance for long-term exposure (365 days or more) is 10 micrograms per cubic meter (µg/m3), or 12 ppb [78].
Modeling results indicate that long-term estimated HF concentrations at the north perimeter station did not exceed the Kentucky ambient air standard but exceeded ATSDR's provisional guidance in 1955, 1956, and 1961. However, estimated HF concentrations did not exceed ATSDR's provisional guidance 1 mile north of the perimeter. The estimated annual average airborne HF concentration at the nearest houses to the site was 22 ppb for 1956, which was above ATSDR's provisional guidance but approximately 25 times lower than Kentucky's standard. This was the only year for which the estimated concentration from long-term releases exceeded the provisional guidance at this location.
Of the documented accidental HF releases, the largest release occurred on November 17, 1960, when a cylinder ruptured in Building C-333. During this accident, 8,074 kilograms (17,800 pounds) of UF6 were released at approximately 4:00 a.m. As discussed in Appendix F, modeling of this accident estimates short-term hazardous HF concentrations more than a kilometer to the southeast of Building C-333, which would include property immediately off site. Therefore, hydrogen fluoride was selected as a contaminant of concern for the air exposure pathway.
Past operations at PGDP involved large quantities of TCE as an organic solvent and degreaser. Historical air releases of TCE were several orders of magnitude larger than current releases from the groundwater treatment facilities. Although significant amounts of TCE were released to the groundwater in the past, most operational releases of TCE volatilized into the atmosphere [47]. To determine if airborne releases presented a potential inhalation exposure to nearby residents, ATSDR scientists estimated the air dispersion of TCE using the Industrial Source Complex (ISC3) model [79], the maximum annual quantities of TCE released from the site, and very conservative assumptions about dispersion, plume rise, and atmospheric degradation. The model and assumptions are discussed in Appendix G.
The maximum estimated airborne TCE concentration at 1,000 meters (3,280 feet) north of Building C-400 is 112 µg/m3 for a 1-hour averaging period (i.e., an acute exposure) and 3 µg/m3 for an annual averaging period. Estimated concentrations were several times lower than the media-specific comparison values for TCE in air (10,920 µg/m3 for acute exposure and 546 µg/m3 for intermediate-duration exposure) [23]. Therefore, TCE was not selected as a contaminant of concern for air exposure pathways.
Sulfur Dioxide and Nitrogen Oxides
Sulfur dioxide and nitrogen oxides are both released to air from the PGDP site. Off-site monitoring for these contaminants has not been performed near the site; therefore, ATSDR scientists used the ISC3 model to estimate off-site concentrations of sulfur dioxide and nitrogen oxides from the on-site coal-burning steam plant. Modeling results indicated that off-site estimated concentrations of sulfur dioxide and nitrogen oxides for chronic exposure are not likely to exceed comparison values. Therefore, sulfur dioxide and nitrogen oxides were not selected as contaminants of concern for air exposure pathways.
Although airborne releases of hexavalent chromium from the cooling towers at PGDP were not reported until 1988, the plant used hexavalent chromium since the early days of operations. From 1988 until 1993, releases of hexavalent chromium from the cooling towers were estimated from concentrations in the cooling water and known annual quantities of chromium compound added to the water. As early as 1958, hexavalent chromium was considered a potential environmental contaminant [81]; however, only surface water samples were analyzed for chromium.
Union Carbide studied chromium contamination in the late 1970s: they evaluated chromium releases from the cooling towers to assess the potential for chromium transport and accumulation in the terrestrial environment [71,74]. Although the Union Carbide studies did not specifically address airborne hexavalent chromium concentrations, they do provide information about deposition of hexavalent chromium on vegetation and soil from the airborne releases. The studies also indicate that chromium deposited from the drift cloud was present as hexavalent chromium; therefore, it is reasonable to assume that airborne chromium was also present in the hexavalent form. Hexavalent chromium was detected on vegetation and in soil at a distance of 1,500 meters (about 0.9 miles) from the towers in 1978. Beyond 1,500 meters, soil and vegetation concentrations could not be differentiated from background chromium concentrations [74].
According to release data from 1988 and later, the maximum annual release of airborne hexavalent chromium occurred in 1992. Therefore, ATSDR scientists used 1992 release data and the ISC3 air dispersion model [79] to estimate maximum air concentrations on site, immediately off site, and at the closest downwind off-site residence for 1-hour, 8-hour, 24-hour, and annual exposures. Appendix H describes the model and the estimated exposure concentrations. Maximum off-site air concentrations were estimated to be at least 100 times lower than ATSDR's comparison values for hexavalent chromium in air. Therefore, chromium was not selected as a contaminant of concern for air exposure pathways.
ATSDR scientists identified completed and potential exposure pathways for past, current, and potential future exposure to air contaminants. Contaminants of concern in these exposure pathways will be evaluated further in the public health implications section of this report.
Off-site airborne radioactive material concentrations are currently being monitored by the Kentucky Department of Health's Radiation Control Program. Since monitoring began in 1996, no concentrations of radioactive materials have been detected above emission standards [80]. ATSDR's estimated committed effective dose for radioactive releases in 1996 is 0.43 millirems per year (0.0043 millisieverts per year)--more than 20 times smaller than the NESHAP requirement of 10 millirems per year (0.10 millisieverts per year) whole body dose.
The current maximum estimated or modeled off-site concentrations of HF, TCE, sulfur dioxide, nitrogen oxides, and hexavalent chromium are low and do not exceed their respective health-based comparison values.
Therefore, ATSDR scientists did not identify any contaminants of concern for current air exposure pathways.
In the
past, TCE, sulfur dioxide, nitrogen oxides, and hexavalent chromium were released
from PGDP; however, the maximum estimated off-site concentrations did not exceed
health-based comparison values. As discussed previously, radionuclides (U-234,
U-235, U-238, and Tc-99), uranium (as a chemical), and HF were identified as
contaminants of concern for past exposure via completed and potential air exposure
pathways. These contaminants will be discussed further in the public health
implications section.
As long as on-site processes remain similar to the current operations and no major accident occurs, future off-site releases of airborne contaminants should continue at current levels, which do not exceed health-based comparison values. Therefore, we did not identify any airborne contaminants of concern for potential future chronic exposure. Future releases of airborne contaminants from the processing facility will be the responsibility of USEC under the current privatization plans.
DOE is considering alternatives for the management of the aging depleted uranium cylinders at PGDP. Should any chemical processing or additional handling of the cylinders or storage of waste from remedial projects be done at this site, the potential for airborne releases will be part of the environmental impact considerations during the planning for the new operations. If on-site activities and operations change, then the potential for off-site exposure should be re-evaluated.
Table 10. Summary of completed and potential exposure
pathways for airborne contaminants
| Major Sources | Radioactive Contaminants | Point of Exposure | Route of Exposure | Exposed Population | Period of Time | Maximum Estimated Annual Committed Effective Dose |
| Process operations, Bldg. C-310 stack, Bldg. C-410 feed plant, Bldg. C-340 metals plant |
U-234, U-235, U-238
Tc-99 |
Downwind off-site ambient air (mainly north of the site) | Inhalation | Residents living within ~500 meters (~0.3 miles) north of fence | Past only 1954 to 1963 1955 to 1965; 1970, 1971, 1973 and 1974 |
Maximum in 1956: 340 mrem (3.4 mSv) |
| Major acute releases:
1960 cylinder rupture 1962 fire |
U-234, U-235, U-238
U-234, U-235, U-238 |
Downwind off-site ambient air (Both accidents toward the southeast) |
Inhalation |
Residents outdoors within 1.5 to 3
kilometers (~0.9 to 1.8 miles) of
accident, which happened at
Building C-333
Residents outdoors more than 0.2 kilometers (0.12 miles) from the accident |
11/17/60 4:00 a.m. 12/13/62 |
0.5 to 1.5 rem (5 to 15 mSv) < 1 mrem |
| Major Sources | Chemical Contaminants | Point of Exposure | Route of Exposure | Exposed Population | Period of Time | Maximum Estimated Exposure Dose (Chemicals) |
| Process operations | Hydrogen fluoride | Downwind off-site ambient air (north of site) | Inhalation | Resident living within ~500 meters (~0.3 miles) north of fence | 1956 only | 22 ppb average hydrogen fluoride concentration |
| Major acute releases:
1960 cylinder rupture |
Uranium
Hydrogen fluoride |
Downwind off-site ambient air (toward the southeast) | Inhalation | Residents outdoors within 1.5 to 4 kilometers (~0.9 to 1.8 miles) of accident, which happened at Building C-333 | 11/17/60 4:00 a.m. |
5 to 20 mg uranium
1 to 5 ppm hydrogen fluoride |
| Key: mg = milligrams; mrem
= millirems; mSv = millisieverts; ppm = parts per million; ppb = parts per
billion; U-234= uranium 234; U-235 = uranium 235; U-238 = uranium 238; Tc-99 = technetium 99 |
||||||
Surface waters around the PGDP site have elevated concentrations of chemical and radioactive
contaminants as a result of process operations and past waste disposal activities at the facility.
Surface waters may also receive contaminants as a result of groundwater discharge to Big Bayou
Creek and the Ohio River [82] and deposition of airborne particles [71]. Surface water
monitoring data reflect total contaminant load. Surface water drainage from PGDP is either east
or northeast to Little Bayou Creek or the
North/South Diversion Ditch, or west or
northwest to Big Bayou Creek. The
North/South Diversion Ditch has flow only
during periods of heavy rain and releases
from the plant. The ditch flows to the
north/northeast and discharges into Little
Bayou Creek. Big Bayou and Little Bayou
creeks converge about 3 miles (5 kilometers)
north of the facility and discharge directly into the Ohio River about a quarter mile (half a
kilometer) further downstream.
Surface water discharges from the PGDP site to Big Bayou and Little Bayou Creeks are regulated under Kentucky Pollutant Discharge Elimination System (KPDES) permits. Surface water runoff from the plant into the North/South Diversion Ditch and from the landfills and the plant into Little Bayou and Big Bayou Creeks are also monitored under KPDES permits. These permits specify allowable contaminant concentrations in discharges and require DOE or the U.S. Enrichment Corporation to monitor effluents and take corrective action if discharges exceed permitted limits.
ATSDR scientists reviewed data for 258 different off-site surface water monitoring stations that PGDP sampled between 1987 and 2000. All stations included in this evaluation are outside the security fence. Samples were analyzed for 511 different chemicals and radiological parameters [44]. PGDP sampled a few monitoring stations as early as 1958 [81]. However, these samples were analyzed for only a few contaminants, including fluoride, nitrate, hexavalent chromium, uranium, and gross beta activity. Maximum concentrations of fluoride, nitrate, hexavalent chromium, uranium, and gross beta activity in historical samples collected close to the site boundary in Big Bayou and Little Bayou Creeks were higher than in samples analyzed from 1987 to 2000 [65]. However, historical data are not directly comparable to more recent measurements, because there have been changes in sampling and analytical techniques over time. Because process operations and waste disposal practices have also changed over time, current contaminant releases to surface waters are generally one to two orders of magnitude lower than historical releases.
Concentrations for most surface water contaminants are not evenly distributed; maximum values may be two orders of magnitude higher than the next highest sample. The maximum concentrations for all surface water contaminants were obtained at one of two locations. For metals, the highest concentrations are at several surface water stations in Big Bayou Creek adjacent to the southwest landfill. Stations at the PGDP outfalls into Little Bayou Creek have the highest concentrations of fluoride, nitrate, polychlorinated biphenyls (PCBs), trichloroethylene (TCE), and radioactive materials.
According to samples collected upstream and downstream of the point where Big Bayou and Little Bayou Creeks discharge into the Ohio River, the river has several chemical contaminants that may be related to PGDP, including chloride, fluoride, and sulfate. Maximum concentrations downstream, however, are barely above the concentrations upstream, and are much lower than levels found in Big Bayou and Little Bayou Creeks [1]. Also, a different source may be responsible for these elevated concentrations of chloride, fluoride, and sulfate.
ATSDR scientists used a series of screening techniques to select contaminants of concern for
surface water exposure pathways. The first phase of this screening involved determining if
maximum off-site concentrations exceeded health-based comparison values for chemicals and if
maximum radiation doses exceed 4 millirems per year (EPA's Drinking Water Standard for
radioactive contaminants). Contaminants of concern for other exposure pathways were also
evaluated if detections were above comparison values. Seventeen chemicals (14 metals, TCE,
nitrate, and total PCBs) were detected in areas of
potential exposure at levels requiring additional
exposure analysis. Eleven radionuclides are
evaluated for potential exposure doses to
determine if they should be considered
contaminants of concern.
The second phase of contaminant screening is based on the calculation of potential exposure doses for each surface water contaminant. Concentrations of most surface water contaminants were log-normally distributed, meaning that a few samples had high concentrations while most of the samples had much lower concentrations. Consequently, the estimated exposure doses were calculated using the 67th percentile of the concentration distribution. The exposure analyses, along with the detection ranges, the 67th percentile concentrations, and the calculated exposure doses, for these contaminants are presented in Tables 11 and 12 in the following section.
Thallium is one of the seventeen chemical surface water contaminants and is the only one that has estimated exposure doses that exceed health guidelines. Therefore, thallium is a contaminant of concern for the surface water pathway and will be discussed further in the following pathway analysis section and in the public health implications section of this report.
Di(ethylhexyl)phthalate is not considered a contaminant of concern. Although this chemical was detected in surface water samples, it is not directly used or stored at PGDP. It is a common additive to plastic sample bottles, rubber gloves, and other plastic products. It was detected three times at different stations with widely varying concentrations. Therefore, ATSDR scientists presumed that di(ethylhexyl)phthalate was introduced during the sampling process and is not a site-related contaminant of concern for surface water.
For current concentrations of radioactive materials in the surface water we used the 67th percentile for reasons described previously; however, we did not have as much data for past concentrations so we used the annual average concentration at the sampling location that had maximum results. Also, there are important differences between current and past analyses of radioactive substances in surface water. Measured concentrations changed over time, but so did the methods of analysis used and the list of radioactive materials being measured. Historical analyses for radioactive materials included total uranium, gross alpha, and gross beta activity. In these analyses, the highest average annual total uranium concentration was 474 picocuries per liter (pCi/L), measured in samples collected from Big Bayou Creek in 1960. The highest average annual gross beta activity was 21,700 pCi/L (Little Bayou Creek, 1960) [83]. Most of this beta activity was attributed to technetium 99 (Tc-99). Therefore, ATSDR scientists used the maximum annual average concentrations for uranium and Tc-99 (gross beta) to estimate past exposure doses (annual committed effective doses) for children and adults. These doses are presented in Table 12 in the following section.
By the 1980s, maximum uranium concentrations had decreased to levels that were less than 1% to 5% of levels reported in 1960. Other radioactive contaminants (strontium 90, neptunium 237, plutonium 239, and thorium 230) were quantified in the 1987-1996 analyses. ATSDR included these other radioactive contaminants in the estimated current exposure doses (annual committed effective doses) for children and adults. These doses are also presented in Table 12 in the following section.
Surface Water Exposure Pathways
The greatest potential for human exposure to
contaminated off-site surface water has been
in Little Bayou Creek, Big Bayou Creek, and
the Ohio River downstream of Big Bayou
Creek. Persons may fish, wade, and play in
the creeks. In addition, there are noted
community health concerns about potential
human exposures. Because contaminants are
present in the creeks and humans may access
these areas, ATSDR scientists identified potential exposure pathways for past, current, and future
exposure to contaminants in surface water. Contaminants of concern in these exposure pathways
will be evaluated further in the public health implications section of this report.
As stated above, the highest concentrations of all surface water contaminants occur at one of two locations: either within the WKWMA property directly adjacent to the southwest landfill or in DOE buffer property at surface and storm water outfalls into Little Bayou Creek. (This includes the North-South Diversion Ditch.) Although exposure is possible in these areas, ongoing monthly ingestion of surface water is unlikely. Also, the 67th percentile concentrations of off-site contaminant levels is much more realistic for calculating potential surface water exposures around PGDP.
Exposure doses are estimated assuming incidental contact and ingestion, because surface water in this area is not used to supply drinking water. For chemical contaminants above the health-based comparison values, we assumed ingestion of 0.5 liters of water per exposure and one exposure per month for 12 months per year. We estimated exposure doses for a child (1 to 6 years old) and an adult, assuming incidental ingestion of surface water contaminated at the 67th percentile of off-site concentrations. For volatile organic compounds, dermal (skin) contact may contribute a dose up to 30% as large as the ingestion dose [56]. TCE was the only volatile organic compound detected in surface water off site. Therefore, we assumed that dermal contact contributed an additional 30% to the estimated ingestion dose for TCE. The estimated exposure doses for current exposure to most chemical contaminants and past exposure to hexavalent chromium, fluoride, and nitrate are shown in Table 11 (using pre-1987 annual average values). The estimated current and past exposures to radioactive contaminants are shown in Table 12. It was not possible to estimate past exposure doses to most chemicals and radioactive materials, because historical measurements are lacking.
Health guidelines provide a basis for evaluating exposure doses estimated from contaminant concentrations in soil, air, water, and food. Exposure doses depend on the characteristics of the people who might be exposed and the length of their exposure. The health guidelines are described in Appendix C. Most of the health guidelines were derived for chronic exposure--that is, exposure lasting more than 364 consecutive days. By contrast, human exposure to off-site contaminated surface water is likely to have occurred infrequently throughout the year and possibly not at all during winter months. According to local residents, there is very little swimming, wading, or other human activity in Big Bayou and Little Bayou Creeks. All of Little Bayou Creek is in DOE or Tennessee Valley Authority property, except for a small area that borders private property to the east of the plant. According to the Kentucky Radiation Control Program, Little Bayou Creek has been restricted and posted at access points since July 19, 1993.
Table 11. Estimated exposure doses for chemical contaminants
in off-site surface water at PGDP and health guidelines
| Chemical Contaminant |
Contaminant Range (and 67th percentile) in µg/L | Estimated Exposure Dose for Children (mg/kg/day)1 | Estimated Exposure Dose for Adults (mg/kg/day)1 |
Oral Health Guideline in mg/kg/day and Source1 | Estimated Exposure Dose Greater Than Health Guideline? |
| Antimony |
10-50 (42) |
0.000084 | 0.000013 | 0.0004 (Chronic RfD) | No |
| Arsenic | 6-90 (38) | 0.000076 | 0.000011 | 0.0003 (Chronic MRL) | No |
| Beryllium | 0-150 (75) | 0.00015 | 0.000023 | 0.002 (Chronic RfD) | No |
| Cadmium | 0-90 (32) | 0.000064 | 0.00001 | 0.0002 (Chronic MRL) | No |
| Chromium | 4-820 (210) | 0.00042 | 0.000063 | 1.5 (Oral RfD) | No |
| Chromium, hexavalent | 20-7,8802 (1,626) |
0.0033 | 0.00049 | 0.003 (ATSDR Interim Oral Intake) | No |
| Fluoride (Fluorine) | 100-35,0002 (1,047) |
0.0021 | 0.00031 | 0.05 (Chronic MRL) | No |
| Lead | 2-12,200 (1,945) | 0.0039 | 0.00058 | 0.0203 | No |
| Manganese | 8-187,000 (22,447) |
0.045 | 0.0067 | 0.07 (ATSDR Interim Guidance Value) | No |
| Nickel | 5-1,350 (320) | 0.00064 | 0.000096 | 0.02 (Chronic RfD) | No |
| Nitrate | 150-900,0002 (2,492) |
0.005 | 0.00075 | 1.6 (Chronic RfD) | No |
| Total PCBs | 1-42 (4.5) | 0.00001 | 0.000002 | 0.00002 (Chronic MRL for Aroclor 1254)4 | No |
| Sulfate | 3,800-1,680,000 (108,184) |
0.22 | 0.032 | 14.295 | No |
| Thallium | 16-5,260 (417) | 0.00083 | 0.00013 | 0.00008 (Chronic RfD) | Yes |
| Trichloroethylene | 1-51 (5) | 0.00001 | 0.000002 | 0.2 (Acute MRL) | No |
| Uranium | 1-3,000 (74) | 0.00015 | 0.000022 | 0.002 (Int./Chronic MRL) | No |
| Vanadium | 2-1,430 (156) | 0.00031 | 0.000047 | 0.003 (Int. MRL) | No |
| 1 For an explanation of health
guidelines and of how we calculated exposure doses, refer to Appendix C. 2 These concentrations are maximum annual averages from historical annual environmental reports [65]. The other concentrations are from the 1987-2000 electronic data and reports [44]. 3 Based on lowest-observed-adverse-effect level (acute) from ATSDR, 1997 [84]. 4 This MRL is based on Aroclor 1254, not total polychlorinated biphenyls. This provides a conservative evaluation. 5 Based on EPA's MCLG and equivalent exposure for a 70-kg adult ingesting 2 liters per day. |
|||||
| Key: mg/kg/day = milligrams of contaminant per kilogram of body weight per day; µg/L = micrograms per liter | |||||
Table 12. Past and current maximum estimated exposure
doses (annual committed effective doses) for radioactive contaminants in surface
water [58]
| Radioactive Contaminant | Past Maximum Concentration in pCi/L (and in Bq/L) |
Current Concentration Range and 67th Percentile in pCi/L (and Bq/L) | Maximum Annual Estimated Committed Effective Dose for Child in mrem (and mSv) | Maximum Annual Estimated Committed Effective Dose for Adult in mrem (and mSv) | ||
| Past | Current | Past | Current | |||
| Americium 241 |
------ |
0.05-17.1 (0-0.63) 13.7 (0.507) |
------ | 0.08 (8.2E-04) |
------ | 0.06 (6.1E-04) |
| Neptunium 237 | ------ | 0.04-13.6 (0-0.50) 0.8 (0.030) |
------ | 0.00 (2.5E-05) |
------ | 0.00 (2.0E-05) |
| Plutonium 238 | ------ | 0.5-3.2 (0.02-0.12) 2.7 (0.100) |
------ | 0.02 (1.9E-04) |
------ | 0.01 (1.4E-04) |
| Plutonium 239 | ------ | 0.01-2.7 (0-0.10) 0.3 (0.011) |
------ | 0.00 (2.2E-05) |
------ | 0.00 (1.6E-05) |
| Strontium 90 | ------ | 6.1-131.3 (0.23-4.86) 64 (2.37) |
------ | 0.07 (6.7E-04) |
------ | 0.04 (4.0E-04) |
| Technetium 99 | 21,700 (803.7)2 | 1-4,000 (0.04-148.1) 61 (2.259) |
1.11 (1.11E-02) |
0.00 (3.1E-05) |
0.309 (3.1E-03) |
0.00 (8.7E-06) |
| Thorium 230 |
------ |
0.002-6.0 (0-0.22) 1.4 (0.052) |
------ | 0.01 (9.7E-05) |
------ | 0.01 (6.6E-05) |
| Uranium, total1 |
474 (17.56)2 |
0.06- 9.5 (0-0.35) 3.4 (0.126) |
0.88 (8.8E-03) |
0.50 (5.0E-03) |
||
| Uranium 234 |
------ |
0.01-119 (0-4.41) 7.5 (0.278) |
------ | 0.01 (1.5E-04) |
------ | 0.01 (8.2E-05) |
| Uranium 235 |
------ |
0.01-2.34 (0-0.09) 0.6 (0.022) |
------ | 0.01 (8.5E-05) |
------ | 0.00 (4.7E-05) |
| Uranium 238 | ------ | 0.33-194 (0.01-7.19) 16.4 (0.607) |
------ | 0.01 (8.0E-05) |
------ | |
| Total committed effective dose | ------ | ------ | 1.99 (0.02)3 | 0.21 (0.00) | 0.81 (0.01)3 | 0.13 (0.00) |
| 1 Total uranium = uranium-234,
uranium-235, and uranium-238 (only used for past exposure calculations). 2 These concentrations are maximum annual averages from historical annual environmental reports [65]. The other concentrations are from the 1987-2000 electronic data and reports [44]. 3 Past total committed effective doses do not include potential exposure to several radionuclides, because there are not enough historical data. |
||||||
| Key: pCi/L = picocuries per liter; Bq/L = becquerels per liter; mSv = millisieverts; mrem = millirems | ||||||
Several chemical and radioactive contaminants have been detected in surface water samples taken from Big Bayou Creek, Little Bayou Creek, and the portion of the Ohio River downstream of Big Bayou Creek. Only one chemical contaminant, thallium, was selected as a contaminant of concern for surface water. The highest concentrations of thallium are reported for Big Bayou Creek and its tributaries near the inactive southwest landfill. Concentrations of thallium are also elevated in Little Bayou Creek east of the plant. ATSDR scientists cannot determine with certainty how long the streams may have been contaminated with thallium, because samples were not analyzed for thallium until 1987. Because thallium may have been present in off-site surface water prior to 1987, thallium is a contaminant of concern for past and current exposure via potential exposure pathways for off-site surface water (as shown in Table 13) and will be discussed in the public health implications section of this report.
Radioactive contaminants were present at low levels in samples taken from Little Bayou and Big Bayou creeks. Because the annual total committed effective doses are less than 4 millirems (0.04 millisieverts) for current exposures, radioactive contaminants are not contaminants of concern for current exposure to surface water. Lack of data for historical concentrations of radioactive materials other than Tc-99 and the uranium isotopes makes it difficult to determine past exposures to all radionuclides in surface waters. It is possible that, during a past release from the site, a person exposed to the surface waters could have received a dose in excess of 4 millirems. Therefore, radioactive materials are considered contaminants of concern for past exposures via potential exposure pathways for off-site surface water and will be discussed in the public health implications section of this report.
With partial restrictions on access to Little Bayou Creek, permitting discharges to off-site surface water, and remedial activities to remove sources of contamination, future exposures to surface water contaminants should either not occur or be much lower than current exposures. Therefore, ATSDR scientists did not identify any potential future exposure pathways for surface water. However, if new processes are initiated at the site or new sources of contamination are identified, future exposures should be addressed at that time.
Table 13. Summary of potential exposure pathways for off-site surface water contaminants
| Major Sources | Contaminants | Point of Exposure | Route of Exposure | Exposed Population | Period of Time | Maximum Estimated Exposure Doses |
| Process operations discharge, surface water runoff, leaching from past waste disposal activities, groundwater discharge, airborne deposition | Thallium
|
During wading or immersion in Little Bayou or Big Bayou Creeks | Incidental ingestion and dermal contact | Children playing in the creeks once per month, and adults fishing and wading in the creeks once per month | Past and current
|
Thallium (mg/kg/d)
Children: 0.00083
|
| Key: mg/kg/d = milligrams
of contaminant per kilogram of body weight per day; mrem = millirems |
||||||
Process operations and waste disposal
activities at PGDP have contaminated soil
and sediment. Off-site surface soil has
become contaminated mainly as a result of
releases from disposed waste material and
deposition of airborne releases. Surface soil
concentrations are highest in the predominant
downwind directions from the site and in soils near the creek and ditches as a result of leaching
from landfills and occasional flooding of the creeks and ditches. Sediment in nearby streams has
become contaminated as a result of surface water discharges and surface runoff from the site.
Deposition of airborne materials also introduces contaminants to streams and ponds, where they
are adsorbed to sediments.
Soil and sediment data evaluated were obtained via electronic transfer from the PGDP environmental database [44], the Kentucky Department for Environmental Protection (Hazardous Waste Branch) and the Kentucky Department for Public Health (Radiological Health and Toxic Agents Branch). The cumulative data set consists of 292,062 chemical and radiological measurements for 457 analytes from 1,737 locations. Data were available for five different sample types and depth profiles:
Because chronic human exposure to subsurface material is very unlikely, ATSDR evaluated only surface and top soil samples (including unspecified depth samples), as well as sediment samples. Sample station names did not designate whether any off-site samples were collected on residential properties. If the stations appeared to be located near residential properties, the residential properties were assumed to have similar soil concentrations. Samples in the electronic data set were collected and analyzed for 1987 through 2000. Additional soil and sediment data, available from annual environmental monitoring reports, were used to corroborate contaminant distributions. A limited soil sampling program began in 1971; however, few samples were collected and were analyzed only for uranium.
Off-site sample locations were not uniformly spaced. They were too far apart to determine whether contaminant distributions followed a regular pattern based on transport and fate (e.g., airborne dispersal) processes. For example, maximum concentrations of technetium 99 and neptunium 237 were found to the north of the fenced area and near the edge of the buffer zone; maximum concentrations of metals, uranium isotopes, thorium 230, and cesium 137 were found west and southwest of the site; and maximum concentrations of most of the radioactive contaminants in sediment were found in drainage ditches and in Little Bayou Creek. Also, most soil sampling stations have not had multiple sampling over time. Consequently, it is not possible to evaluate historical trends of soil contamination at PGDP. This evaluation will assume that if PGDP contaminants have been detected at a soil sampling location, that location has been contaminated since the beginning of PGDP operations. As with surface water, concentrations of most soil and sediment contaminants are not evenly distributed.
ATSDR scientists used a screening technique to select contaminants of concern for soil and
sediment exposure pathways. This screening
involved determining if maximum concentrations
of these contaminants in areas of potential human
exposure exceeded health-based comparison
values for chemicals and if maximum radiation
doses exceeded 25 millirems per year (mrem/year)
for radionuclides. Thirteen chemical contaminants
and twelve radionuclides were consistently
detected in areas of potential exposure at concentrations requiring additional exposure analyses.
Most of the contaminants remaining after the first phase of screening are naturally occurring metals with concentrations that may have been elevated above background levels by process operations or waste disposal activities. In addition, polychlorinated biphenyls (PCBs or Aroclors) have been detected above comparison levels. The PCBs have been analyzed as both individual species (Aroclor 1016, Aroclor 1242, Aroclor 1254, etc.) and as total PCBs. Only total PCBs will be evaluated further.
Several detected contaminants are not considered further. Metallic mercury, 1,2-dichloroethene (cis and trans), and ammonia each had only one sample above comparison values. These single high values were not repeated in other analyses, which indicates that the high values are sampling or analytical anomalies, or that the spatial extent of the contaminants is so limited that significant exposure is not possible. Silver was also detected at several on-site sediment or soil samples for which no chronic (long-term) community exposure is possible. Off-site detections of silver were below levels of health concern. Also, trichloroethylene, a contaminant of concern for the groundwater exposure pathway, was detected in five samples. However, those detections were at on-site stations and below levels of health concern. Chromium is also not evaluated further, because concentrations are below health-based comparison values for trivalent chromium. Although the valence of the chromium soil samples is not specified, other studies have shown that virtually all of the soil chromium is in the trivalent form, not the more toxic hexavalent form [71,74].
Most of the contaminants evaluated further have higher concentrations on site than off site. This means that site activities may be responsible for contaminant distributions. Arsenic, lead, and nickel have higher off-site concentrations, which suggests that PGDP activities may not be responsible for the distributions of these contaminants. It is also possible that several of the soil and sediment contaminants are at background levels--that is, that they do not represent site-related contamination. Prior use of the PGDP site by the Kentucky Ordnance Works could also contribute metals contamination. Because arsenic, lead, and nickel exceed health-based comparison values, the following exposure analyses will identify their potential exposure pathways and estimated exposure doses.
Soil and Sediment Exposure Pathways
Contaminated soils and sediments are present
both inside and outside of the PGDP security
fence. The most significant soil
contamination is within the fence but has
little potential for public exposure. However,
soil contaminants with concentrations above
health comparison values are present within
the unsecured buffer area maintained as part
of the Western Kentucky Wildlife
Management Area (WKWMA) and on private
land outside the buffer area. The most contaminated sediments are similarly located within the
access-restricted drainage ditches and Little Bayou, but contaminated sediments are also present
within the open access areas of Big Bayou, nearby ponds, and private lands.
The distribution of land uses surrounding PGDP presents two scenarios by which the public may be exposed to soil and sediment contaminants. Scenario 1 covers WKWMA workers and visitors, who may be exposed to soil and sediment contaminants in the buffer zone and adjacent WKWMA property. Scenario 2 covers people living adjacent to PGDP. As with surface water, concentrations of most soil and sediment contaminants are log-normally distributed, meaning that a few samples had high concentrations while most of the samples had much lower concentrations [85]. Consequently, the estimated exposure doses were calculated using the 67th percentile of the concentration distribution. The following sections present the exposure attributes, contaminant concentrations, and estimated exposure doses that are specific to each of those scenarios. The following scenarios assume that soils and sediments became contaminated shortly after the beginning of PGDP operations and that the exposure pathways are complete in the past, present, and future. The detection ranges, the 67th percentile concentrations and the calculated exposure doses are presented in Tables 14.A, 14.B, 15.A, and 15.B.
Scenario 1--WKWMA Workers and Visitors
WKWMA workers involved with maintenance of the buffer zone property have a high potential for contact with contaminated soil. This scenario also includes visitors to WKWMA, although they would be exposed less often than WKWMA workers and receive a commensurately lower exposure dose.
For this scenario, ATSDR scientists assumed that workers could be exposed to top soil, surface soil, or soil at unspecified depth and would spend approximately 8 hours a day for 1.5 days a week (i.e., 30% of their work week) in contaminated buffer zone areas. We also assumed that the same WKWMA workers were exposed to contaminated sediment for 0.75 days each week (15% of the work week). We assumed that these soil and sediment exposures went on for 50 weeks per year for 10 years, which is an approximate maximum period of employment at the WKWMA. Soil contaminant concentrations for these exposures were derived from buffer zone soil samples. Sediment contaminant concentrations were derived from all sediment samples taken outside the security fence.
Exposure was assumed to occur via direct (dermal) contact and ingestion for chemical contaminants and via ingestion and external exposure for radioactive contaminants. For ingestion, we assumed an ingestion rate of 200 milligrams (mg) of soil per day (four times the daily average adult rate [23]) and 100 mg of sediment per day (two times the average adult rate). We assumed that workers were men and women. Table 14A shows the estimated exposure doses for chemical contaminants (along with additional assumptions we made in calculating them). Table 14B shows estimated exposure doses (annual committed effective doses) for radioactive contaminants in this scenario. Table 14B does not show estimated external exposure to radioactive contaminants. (The estimated external exposure from surface and/or top soil would add approximately 8 mrem/year for this scenario [86].)
For this scenario, no chemical exposure doses exceed the health guidelines, and the estimated total annual committed effective dose for radioactive materials does not exceed 25 mrem (0.25 millisieverts, or mSv). Although this exposure pathway is presumed complete for past, current, and potential future exposures, the estimated exposure doses are not expected to produce adverse health effects.
Table 14A. Estimated exposure doses to WKWMA workers
and visitors for chemical contaminants in buffer zone soil and sediment (Scenario
1)
| Chemical | Soil Range and 67th
Percentile (mg/kg) |
Sediment range and 67th
Percentile (mg/kg) |
Combined Soil-Sediment Exposure Dose1 (mg/kg/day) | Health Guideline (mg/kg/day) (source)1 | Does Est. Exposure Dose Exceed Health Guideline? |
| Antimony | 1-18 2.7 |
0.5-1,320 11.3 |
0.000009 | 0.0004 (chronic RfD) | No |
| Arsenic | 1-38 8.3 |
0.7-30 7.6 |
0.00002 | 0.0003 (chronic MRL) | No |
| Barium | 7-360 102 |
11.6-1,160 134 |
0.0002 | 0.07 (chronic RfD) | No |
| Beryllium | 1-17 4.4 |
0.2-8.2 1.0 |
0.000006 | 0.002 (chronic RfD) | No |
| Cadmium | 1-4 1.5 |
0.1-21 1.3 |
0.000002 | 0.0002 (chronic MRL) | No |
| Fluoride | 200-310 301.6 |
170-210 182 |
0.0005 | 0.05 (chronic MRL) | No |
| Lead | 0.1-705 46 |
6-635 51.1 |
0.00009 | 0.022 | No |
| Manganese | 34-4,020 612 |
33-2,830 587 |
0.001 | 0.07 (ATSDR Interim Guideline) | No |
| Nickel | 2-461 26.8 |
2.5-540 29 |
0.00005 | 0.02 (chronic RfD) | No |
| Uranium | 0.04-1,850 43.1 |
0.3-13,070 85 |
0.00004 | 0.002 (chronic MRL) | No |
| Vanadium | 4-460 50.4 |
6.5-460 47.2 |
0.000007 | 0.003 (intermediate MRL) | No |
| Polychlorinated biphenyls (PCBs) | 0.07-2.4 0.8 |
0.01-58.7 1.4 |
0.000002 | 0.00002 (chronic MRL for Aroclor 1254) | No |
| 1 For an explanation of health
guidelines, and of how we calculated exposure doses, refer to Appendix C. 2 Based on the acute lowest-observed-adverse-effect level from ATSDR, 1997 [84]. |
|||||
| Key: mg/kg = milligrams per kilogram; mg/kg/day = milligrams of contaminant per kilogram of body weight per day; RfD = EPA's reference dose; MRL = ATSDR's minimal risk level | |||||
Table 14B. Estimated exposure doses (annual committed
effective doses) to WKWMA workers and visitors for radioactive contaminants
in buffer zone soil and sediment (Scenario 1) [58]
| Radioactive Contaminant | Soil Range and 67th Percentile in pCi/g (Bq/g)1 | Sediment Range and 67th Percentile in pCi/g (Bq/g) | Combined Exposure Dose (annual committed effective dose) in mrem (mSv)2 |
| Americium 241 | 0.09-13 (0.003-0.48) 6.2 (0.23) |
0.01-9.4 (0-0.35) 1.1 (0.04) |
0.072 (7.2E-04) |
| Cesium 137 | 0.03-160 (0.001-5.93) 6.5 (0.24) |
0.01-52.3 (0-1.94) 0.6 (0.02) |
0.005 (4.8E-05) |
| Neptunium 237 | 0.01-22 (0-0.81) 2.3 (0.09) |
0.01-63 (0-2.33) 0.5 (0.02) |
0.016 (1.6E-04) |
| Plutonium 238 | 0.03-0.62 (0.001- 0.02) 0.2 (0.01) |
0.001-0.6 (0-0.02) 0.1 (0.004) |
0.004 (3.8E-05) |
| Plutonium 239 | 0.01-31 (0-1.15) 1.2 (0.04) |
0.01-53 (0-1.96) 0.5 (0.02) |
0.017 (1.7E-04) |
| Potassium 40 | 0.44-74 (0.02-2.74) 11.8 (0.44) |
2.59-15.7 (0.10-0.58) 3.8 (0.14) |
0.004 (4.4E-05) |
| Technetium 99 | 0.00-2200 (0-81.48) 145.7 (5.40) |
0.04-3,900 (0-144.4) 18 (0.67) |
0.005 (5.3E-05) |
| Thorium 230 | 0.00-110 (0-4.07) 12.6 (0.47) |
0.01-1,300 (0-48.15) 5.2 (0.19) |
0.163 (1.6E-03) |
| Thorium 234 | 0.97-1,330 (0.04-49.26) 93 (3.44) |
0.6-3,263 (0.02-120.85) 22.3 (0.83) |
0.019 (1.9E-04) |
| Uranium 233/234, or Uranium 234 | 0.4-20,0003 (0.015-740.7) 21.4 (0.79) |
0.05-445 (0-16.48) 5.6 (0.21) |
0.062 (6.2E-04) |
| Uranium 235 | 0.00-1100 (0-40.74) 1.8 (0.07) |
0.01-57 (0-2.11) 0.6 (0.02) |
0.005 (5.3E-05) |
| Uranium 238 | 0.07-20,0003 (0-740.74) 93.5 (3.46) |
0.08-720 (0-26.67) 9.7 (0.36) |
0.24 (2.4E-03) |
|
Estimated Total Annual Committed Effective Dose: 0.61 (6.1E-03) | |||
| 1 The concentration range includes
soil sample results from soils up to and including 1 foot (30 centimeters
deep), as well as at unspecified depths. 2 In calculating exposure doses, we assumed 200 mg/day soil ingestion for 1.5 days/week and 100 mg/day sediment ingestion for 0.75 days/week for 50 weeks per year. Dose conversion factors from ICRP 72 were used [58]. External exposure (about 8 mrem/y) was not added in this table. 3 Unspecified-depth sample (actually a subsurface sample) near or at the southwest landfill. |
|||
| Key: pCi/g = picocuries per gram; Bq/g = becquerels per gram; mSv/y = millisieverts per year; mrem/y = millirems per year; mg/day = milligrams of soil per day | |||
For this scenario, we used soil and sediment contaminant concentrations outside the buffer area which, in general, are much lower than on-site concentrations. On the other hand, potential exposure in a residential setting is likely to occur at a much greater frequency than the exposure described in the previous scenario. The 67th percentile soil contaminant concentrations (rationale on page 63) were calculated for all soil sampling locations outside the buffer zone. (Soil sampling nomenclature did not designate whether the samples were taken on residential properties.) Also, ATSDR assumed people would be exposed to chemical contaminants via dermal contact and ingestion and to radioactive contaminants via ingestion only.
For children, we assumed a 1 to 6 year old child weighing 13 kilograms (kg) would consume soil at a rate of 200 mg per day while playing. Young children are more likely to play in creeks surrounding PGDP, so exposures to sediment were combined with residential soil exposures. Sediment exposures were assumed to occur for 1 day per month, with 100 mg of sediment ingested in each event. The scenario parallels the surface water exposure pathway evaluation, because exposure to contaminated surface water and sediment is assumed to occur at the same time.
Some children exhibit pica behavior, a craving for unnatural food like soil and sediment. The degree of pica behavior varies in the population and is influenced by nutritional status and quality of care and supervision [23]. Children less than 3 years old are most likely to exhibit this behavior. According to 1990 Census data for areas surrounding the PGDP facility, there were 24 children aged 1 to 6 living within 1 mile of the site security fence (as discussed in Appendix A). Therefore, we assumed that a child showing pica behavior, weighing 10 kg and ingesting 2,000 mg of soil per day could live in the area. [87].
For adults, we assumed that a 70-kg adult incidentally ingests 50 mg of soil per day [23].
For all persons, we assumed 5.6 days of soil exposure a week for 52 weeks a year, or a total of 292 days a year. For children, we assumed an exposure duration of 6 years; for adults, we assumed an exposure duration of 30 years, because more than 15% of households surrounding the PGDP facility had residents who lived in the area for more than 30 years (as described in Appendix A). These assumptions are conservative and protective since such exposures are very unlikely. Table 15A shows the estimated exposure doses for chemical contaminants. Table 15B shows estimated exposure doses (annual committed effective doses) for radioactive contaminants.
Table 15A. Estimated exposure doses to residents
for chemical contaminants in off-site soil (Scenario 2)
| Chemical | Soil Concentration Range in mg/kg | Soil 67th
% Concentration in mg/kg |
Estimated Exposure Dose in mg/kg/day1 | Health Guideline in
mg/kg/day (source)1 |
Does Est. Exposure Dose Exceed Health Guideline? | ||
| Adult Soil | Child Soil and Sediment2 | Pica Child Soil | |||||
| Antimony | 1-50 | 6.1 | 0.000009 | 0.00003 | 0.001 | 0.0004 (chronic RfD) | Yes, for pica child |
| Arsenic | 1-38 | 10.6 | 0.00002 | 0.0001 | 0.002 | 0.0003 (chronic MRL) | Yes, for pica child |
| Barium | 7-367 | 153 | 0.0003 | 0.001 | 0.02 | 0.07 (chronic RfD) | No |
| Beryllium | 1-29 | 4.8 | 0.00001 | 0.00005 | 0.0008 | 0.002 (chronic RfD) | No |
| Cadmium | 0.03-42 | 1.2 | 0.000002 | 0.000005 | 0.0002 | 0.0002 (chronic MRL) | No |
| Fluoride | 2.2-310 | 38.2 | 0.00008 | 0.0004 | 0.006 | 0.05 (chronic MRL) | No |
| Lead | 1-1,0103 | 45.4 | 0.00008 | 0.0003 | 0.007 | 0.024 | No |
| Manganese | 34-4,020 | 817 | 0.001 | 0.003 | 0.10 | 0.07 (ATSDR Interim Guideline) | Yes, for pica child |
| Nickel | 2-17,600 | 33 | 0.00005 | 0.0001 | 0.005 | 0.02 (chronic RfD) | No |
| Uranium | 2.1-346 | 20.1 | 0.00005 | 0.0001 | 0.00016 | 0.002 (chronic MRL) | No |
| Vanadium | 0.01- 300 | 35.5 | 0.00005 | 0.0001 | 0.006 | 0.003 (inter. MRL) | Yes, for pica child |
| Polychlorinated biphenyls (PCBs) | 0-4.7 | 0.8 | 0.000002 | 0.000008 | 0.00001 | 0.00002 (chronic MRL for Aroclor 1254) | No |
| 1 For an explanation of health
guidelines, and of how we calculated exposure doses, refer to Appendix C. 2 Sediment values listed in Table 14A. 3 Maximum lead value is at unspecified depth and only used for screening. 4 Based on the acute lowest-observed-adverse-effect level from ATSDR, 1997 [84]. |
|||||||
| Key: mg/kg = milligrams per kilogram; mg/kg/day = milligrams of contaminant per kilogram of body weight per day | |||||||
Table 15B. Estimated exposure doses (annual committed
effective doses) to residents for radioactive contaminants in off-site soil
(Scenario 2) [58]
| Radioactive Contaminant | Soil Concentration Range in pCi/g (Bq/g)1 | Soil 67th Percentile Concentration in pCi/g (Bq/g) | Estimated Exposure Dose (annual committed effective dose) in mrem (mSv)2 | ||
|
Adult Soil |
Child Soil and Sediment3 |
Pica Child Soil | |||
| Americium 241 | 0.03-1.5 (0.001-0.056) | 0.8 (0.030) | 0.009 (8.8E-05) | 0.049 (4.9E-04) | 0.648 (6.5E-03) |
| Cesium 137 | 0.03-11.1 (0.001-0.411) | 0.5 (0.019) | 0.000 (3.6E-06) | 0.001 (1.1E-05) | 0.013 (1.3E-04) |
| Neptunium 237 | 0.00-52.6 (0-1.948) | 0.3 (0.011) | 0.002 (1.8E-05) | 0.009 (9.3E-05) | 0.134 (1.3E-03) |
| Plutonium 238 | 0.03-0.06(0.001-0.002) | 0.03 (0.001) | 0.000 (3.4E-06) | 0.002 (1.9E-05) | 0.023 (2.3E-04) |
| Plutonium 239 | 0.00-31.0 (0-1.148) | 0.43 (0.016) | 0.006 (5.8E-05) | 0.010 (9.6E-05) | 0.392 (3.9E-03) |
| Potassium 40 | 0.44-18.6 (0.016-0.689) | 4.8 (0.178) | 0.002 (1.6E-05) | 0.022 (2.2E-04) | 0.437 (4.4E-03) |
| Technetium 99 | 0.0-4,840 (0-179.26) | 146 (5.41) | 0.005 (5.1E-05) | 0.073 (7.3E-04) | 1.517 (1.5E-02) |
| Thorium 230 | 0.00-34.8 (0-1.289) | 1.4 (0.052) | 0.016 (1.6E-04) | 0.101 (1.0E-03) | 1.245 (1.2E-02) |
| Thorium 234 | 0.97-136 (0.036-5.037) | 14.4 (0.533) | 0.003 (2.6E-05) | 0.042 (4.2E-04) | 0.778 (7.8E-03) |
| Uranium 234 | 0.12-102 (0-3.778) | 8.1 (0.300) | 0.021 (2.1E-04) | 0.156 (1.6E-03) | 2.278 (2.3E-02) |
| Uranium 235 | 0.00-2.2 (0-0.081) | 0.24 (0.009) | 0.001 (6.2E-06) | 0.005 (4.7E-05) | 0.068 (6.8E-04) |
| Uranium 238 | 0.23-86 (0.01-3.185) | 7.3 (0.270) | 0.018 (1.8E-04) | 0.130 (1.3E-03) | 1.892 (1.9E-02) |
|
Estimated Total Annual Committed Effective Doses |
0.083 (8.3E-04) | 0.600 (6.0E-03) | 9.425 (9.4E-02) | ||
| 1 The concentration range includes
soil sample results from soils at less than or equal to 1 foot (30 centimeters)
deep or unspecified depths. 2 For explanation of exposure dose calculations, refer to Appendix C. 3 Sediment values listed in Table 14B. |
|||||
| Key: pCi/g = picocuries per gram; Bq/g = becquerels per gram; mrem/y = millirems per year; mSv/y = millisieverts per year; mg = milligrams | |||||
For this scenario, the estimated total annual committed effective dose for radioactive materials does not exceed 25 mrem (0.25 mSv); therefore, we expect no adverse health effects from exposure to radioactive materials for residents. The estimated chemical exposure doses for children with pica behavior exceed the health guidelines for antimony, arsenic, manganese, and vanadium. These chemicals and their estimated exposure doses will be discussed further in the public health implications section of this report.
The soil exposure pathway is considered a potential exposure pathway for children with pica behavior, since the soil concentrations may or may not be on residential property and there may or may not be children in the area demonstrating pica behavior. The potential exposure pathway is summarized in Table 16.
Table 16. Summary of potential exposure pathways for
off-site soil and sediment
| Major Sources | Contaminants | Point of Exposure | Route of Exposure | Exposed Population | Period of Time | Maximum Estimated Exposure1 |
| Waste disposal activities
Airborne particle deposition Deposition from surface water discharge and runoff Background and/or prior site activities (Kentucky Ordnance Works) |
Antimony Arsenic Manganese Vanadium |
Off site; assumed samples taken on or near residential properties | Ingestion Dermal |
Children with pica behavior only (residents) | Past, current, and potential future |
Child with pica behavior only: 0.001 mg/kg/d (antimony) 0.002 mg/kg/d (arsenic) 0.10 mg/kg/d (manganese) 0.006 mg/kg/d (vanadium) |
| 1 For an explanation of how we calculated exposure doses, refer to Appendix C. | ||||||
| Key: mg/kg/d = milligrams of contaminant per kilogram of body weight per day (exposure unit for chemicals) | ||||||
Contaminants released from PGDP to air and
water may accumulate in plants and animals,
which are collectively referred to as biota.
Many of these plants and animals are
important sources of human nutrition. As
such people who consume them may be
potentially exposed to chemical and
radioactive substances. In this section, we
focus on complete or potential human exposure pathways (biota consumed by humans).
DOE began monitoring biota near PGDP in 1955, sampling broadleaf grass for fluorides [12]. DOE's results were published in the site annual reports beginning in 1958 [81]. Sampling locations and collection frequencies varied over the years. In 1994, DOE stopped sampling broadleaf grasses [44]. They began off-site sampling and radiological analyses of edible wildlife and garden vegetables in 1984 [88]. Fish sampling for plutonium 239, technetium 99, and uranium isotopes began in 1985 [89]. DOE began sampling local milk and food crops in 1988 and added animal tissue from wild animals in the Western Kentucky Wildlife Management Area (WKWMA) in 1989 [53,54].
The Kentucky Department for Environmental Protection (Division of Waste Management) and the Kentucky Department for Public Health (Radiation Health and Toxic Agents Branch) also collect and analyze biota samples near PGDP. In many cases, DOE and the state agencies split samples in order to validate their results. These state agencies also work closely with WKWMA personnel in this effort.
ATSDR scientists evaluated biota data contained in the site annual environmental reports, special study reports, and the PGDP and Commonwealth of Kentucky environmental databases. The databases include biota samples collected from 1989 through 1999. The data include 22,180 measurements of 150 different chemical and radioactive substances in 22 types of biota [44,80].
Chemical and radioactive contaminants have been measured in samples of fish (e.g., sunfish, bass, carp, and catfish), game, green beans, soybeans, nuts, corn, apples, persimmons, and other fruits and vegetables collected near PGDP [44,80]. DOE and the Commonwealth of Kentucky have sampled fish from several different locations in Big Bayou and Little Bayou Creeks and in several ponds and lakes in the area. They sampled game animals, including deer, rabbit, quail, raccoon, and squirrel, primarily from the WKWMA. They collected background fish samples from Hinds Creek and background deer samples from the Land Between the Lakes. Because fish and game are mobile, the exact location of samples has changed over time [60,53,54,45,46,47]. Food crop samples were obtained from approximately 89 locations, mainly residential locations. These locations and sample station names have also changed over time [60,53,54,44,45,46,47].
ATSDR scientists used screening techniques to focus the evaluation only on contaminants that may be a human health hazard for biota exposure pathways. First, we evaluated analytical data to determine maximum or average concentrations for the following chemical contaminants in biota: (1) metals, including aluminum, arsenic, barium, beryllium, cadmium, chromium, copper, lead, manganese, mercury, nickel, selenium, silver, uranium, vanadium, and zinc; (2) fluoride; and (3) one class of organic compounds, polychlorinated biphenyls (PCBs). Concentrations of the metals and fluoride in biota are in Table 17A(1), and concentrations of the PCBs in biota are in Table 17A(2). We also evaluated data for the following radioactive contaminants in biota: technetium 99, uranium 234, uranium 235, uranium 238, thorium 230, plutonium 239, americium 241, neptunium 237, strontium 90, and cesium 137. Concentrations of radioactive contaminants in biota are in Table 17B.
Since there were many types of biota sample, we grouped similar types into categories:
| Biota Category | Possible Biota Types in Category |
| Fish | Bass, catfish, sunfish, carp, creek chub |
| Game | Deer, quail, rabbits, raccoons, squirrels |
| Apples | Apples |
| Grapes | Grapes |
| Persimmons | Persimmons |
| Nuts, legumes | Walnuts, soy beans, green beans |
| Yellow vegetables | Corn, squash, carrots, eggplants, mixed vegetables |
| Green vegetables | Cabbages, cucumbers, peas, peppers (and broadleaf grass for fluoride only) |
| Tomatoes | Tomatoes |
For categories with more than one biota type (e.g., yellow vegetables), we averaged the maximum concentration for each type in the category. For fish, we averaged PCB concentrations within and over fish species to reflect fishing and consumption patterns. This would lead to more realistic exposure doses. Not all contaminants have been analyzed for each biota type. For example, green vegetables and grapes were analyzed only for radioactive contaminants. Overall, however, we felt there were sufficient data to evaluate most contaminants in each category, with a couple of notable exceptions.
PGDP has emitted significant quantities of fluoride, but the electronic database does not contain data for fluoride in biota. In the late 1950s and early 1960s, average fluoride levels in off-site broadleaf grass exceeded Kentucky's Ambient Air Quality Standard for fluoride in forage [77].(4) In 1959, the average fluoride level in broadleaf grass samples collected 0.5 miles east of the security fence was 50.6 micrograms of fluoride per gram of grass (µg/g), reported as a dry weight concentration. For purposes of estimating human exposure doses, we converted this fluoride concentration to a wet concentration, assuming a 50% moisture content: the result was a wet weight concentration of 25.3 µg/g. We assumed that wet weight concentration was present in off-site green vegetables. These conservative assumptions would most likely overestimate the dose.
Two bass samples in Gravel Pit Pond contained mercury at 5 to 10 times the level found in other bass, sunfish, and catfish samples near PGDP. We believe that these samples do not represent mercury levels typically found in bass near PGDP. The two samples were not used in the mercury evaluation and are not included in Table 17A(1). However, someone who ate only bass from the Gravel Pit Pond for an extended period of time might experience adverse health effects.
Annual environmental reports and special studies indicate that PCBs are present in fish collected from Big Bayou and Little Bayou creeks and other surface water sources. By the end of 1988, PCBs were detected in fish tissue samples from Little Bayou Creek and from Outfall #11 on the east side of the site [54]. For this reason, DOE started monitoring PCB levels in fish in the area. PCB results from the 1989 DOE environmental report indicates that the highest concentrations were found in fish tissue collected from the Outfall #11/Little Bayou Creek sampling location. Total PCB levels were more than three times the average level detected in fish from the remainder of Little Bayou Creek and almost 20 times greater than total PCB levels detected in fish from Big Bayou Creek. This means that, in the time covered by the 1989 report, total PCB concentrations detected in fish tissue from Little Bayou Creek (as a whole) were approximately five times greater than concentrations detected in fish tissue from Big Bayou Creek [54].
According to the Oak Ridge National Laboratory (ORNL) report on biological monitoring at PDGP for 1993-1994, average total PCB concentrations in fish tissue are approximately 10 times lower than the concentrations given in the PGDP 1989 report [90,54]. Also, the ORNL report listed total PCB levels in fish tissue from Little Bayou Creek as approximately four times greater than concentrations detected in fish tissue from Big Bayou Creek.
In September 1997, the University of Kentucky collected and analyzed fish samples from the Bayou Creek system and found that concentrations were similar to concentrations detected in the ORNL report for 1993-1994 [89,90]. This suggests that PCB concentrations are stabilizing in fish from Little Bayou Creek.
Table 17A(1). Maximum concentrations of chemical
contaminants (except PCBs) in biota (fish, game, and food crops) near PGDP (in
µg/g or ppm)1
| Sample | Biota | Type | Al | As | Ba | Be | Cd | Cr | Cu | F | Pb | Mn | Hg | Ni | Se | Ag | U | V | Zn |
| Fish | Bass | Tissue | 211.0 | 1.0 | 6.3 | 29.0 | 4.5 | 0.72 | 0.7 | ND | 58.8 | ||||||||
| Fish | Catfish | Tissue | 1.3 | 14.6 | 0.7 | 3.5 | 0.62 | 1.4 | ND | ND | 41.0 | ||||||||
| Fish | Sunfish | Tissue | 137.0 | 0.4 | 2.4 | 4.7 | 21.5 | 6.4 | 30.8 | 0.042 | 0.7 | ND | ND | 77.3 | |||||
| Fish | AVERAGE | 174.0 | 0.7 | 2.4 | 4.1 | 21.7 | 3.9 | 17.1 | 0.45 | 0.9 | ND | 59.0 | |||||||
| Game | Deer | Fat | 0.1 | 0.4 | ND | 1.3 | 43.3 | 3.1 | 4.2 | ND | ND | ND | 34.5 | ||||||
| Game | Deer | Liver | 23.0 | 0.0 | 34.0 | 0.8 | 0.7 | 1.7 | 110.0 | 3.3 | 6.8 | 2.1 | 14.2 | 4.5 | 0.6 | 0.0 | 0.3 | 58.0 | |
| Game | Deer | Muscle | 13.4 | 0.2 | 8.6 | 0.9 | 0.4 | 1.2 | 4.3 | 4.8 | 2.1 | 6.6 | 1.5 | 0.5 | 15.4 | 0.1 | 0.4 | 100.0 | |
| Game | Rabbit | Muscle | 3.9 | ND | 0.2 | ND | ND | ND | 1.2 | ND | 0.6 | ND | ND | ND | 0.5 | ND | 17.4 | ||
| Game | Rabbit/Quail | Muscle | ND | ND | ND | ND | 1.0 | ND | 0.1 | ND | ND | 5.0 | ND | 10.6 | |||||
| Game | Raccoon | Muscle | 51.8 | 0.1 | 0.4 | 0.0 | 16.1 | 1.6 | 8.8 | 0.7 | 5.0 | ND | 0.2 | 7.7 | 5.4 | 0.5 | 40.8 | ||
| Game | Raccoon | Fat | 25.0 | 0.1 | 9.6 | 1.1 | 0.5 | ND | 0.1 | 17.5 | |||||||||
| Game | Raccoon | Liver | 23.7 | 0.1 | 13.7 | 0.6 | 4.1 | ND | 0.4 | 30.4 | |||||||||
| Game | AVERAGE | 23.5 | 0.1 | 10.8 | 0.5 | 5.7 | 1.4 | 24.0 | 2.3 | 2.9 | 4.4 | 7.9 | 1.1 | 5.8 | 1.8 | 0.4 | 38.7 | ||
| Apple | Apple | Unknown | 60.6 | 0.1 | ND | ND | 2.1 | 15.3 | 1.8 | 3.2 | ND | 7.2 | ND | ND | ND | 11.6 | |||
| Persimmon | Persimmon | Unknown | 51.8 | ND | ND | 2.4 | 6.3 | 0.8 | 63.8 | ND | 2.7 | ND | ND | 15.5 | |||||
| Nut, legume | Walnut | Unknown | 46.0 | ND | ND | 2.2 | 23.3 | 0.8 | 5.9 | ND | 9.30 | ND | ND | 13.20 | |||||
| Nut, legume | Soybean | Unknown | 73.4 | 0.1 | 28 | ND | 2.3 | 5.5 | 0.9 | 181.0 | ND | 1.60 | ND | 8.40 | |||||
| Nut, legume | Green bean | Unknown | ND | ND | ND | ND | 1.2 | 12.8 | 0.7 | 3.3 | ND | 6.40 | ND | 8.10 | |||||
| Nut, legume | AVERAGE | 59.7 | 0.1 | 28 | ND | 1.9 | 13.9 | 0.8 | 63.4 | ND | 5.8 | ND | ND | 9.9 | |||||
| Yellow vegetable | Corn | Unknown | 275.0 | 0.4 | ND | 2.3 | 99.3 | 3.7 | 93.7 | ND | 44.6 | ND | ND | 76.7 | |||||
| Green vegetable | Grass | Unknown | 50.63 | ||||||||||||||||
| 1
Concentrations are maximums from 1987-2000 electronic databases, except
AVERAGE, which is the average of maximums in a group. Other exceptions are
indicated. 2 Concentration is maximum from UK study, Analysis of Mercury in Stream Water, Sediment and Fish from Bayou Creek System; however, bass sample from gravel pit pond not used (see narrative) [91]. 3 Average concentration in broadleaf grass at location with highest annual average, Environmental Monitoring Summary for the Paducah Plant for 1959 [65]. A blank cell means no valid analyses were conducted. |
|||||||||||||||||||
| Key: Al = aluminum; As =
arsenic; Ba = barium; Be = beryllium; Cd = cadmium; Cr = chromium; Cu =
copper; F = fluorine; Pb = lead; Mn = manganese; Hg = mercury; Ni = nickel; Se = selenium; Ag = silver; U = uranium; V = vanadium; Zn = zinc; ND = not detected or no samples had concentrations above analytical detection limits |
|||||||||||||||||||
Table 17A(2). Average concentrations of PCBs in
biota (fish and game) near PGDP (in µg/g or ppm)
| Sample | Year | Type |
Little Bayou Creek |
Big Bayou Creek |
Other: Little Bayou Creek |
|||
| Aroclor 1254 | Total PCBs1 | Aroclor 1254 | Total PCBs1 | Aroclor 1254 | Total PCBs1 | |||
| Fish (all species) | 19892 | Tissue | 2.196 | 4.843 | 0.477 | 1.02 | 7.63 | 17.95 |
| 1993-19943 | Tissue | 0.553 | 0.1425 | |||||
| 19974 | Tissue | 0.1612 | 0.561 | |||||
| Game (deer) | 19915 | Muscle | 0.05 | 0.05 | ||||
| 1 "Total PCBs" is the total concentration
for Aroclors 1248, 1254, and 1260. 2 PGDP environmental report for 1989 [54]. 3 ORNL report, December 1993 to December 1994 [90]. 4 Report to FFOU on Polychlorinated Biphenyl (PCB) Residue in Fish From the Bayou Creek System [89]. 5 DOE's electronic information management system database from 1987 to 2000 [44]. Only one sample had a detection level of 0.05 ppm. Other results were reported as non-detections; however, the detection levels were generally 0.05 ppm or higher. Note: Data were also reviewed from DOE and Kentucky Biological Monitoring Program Reports and the University of Kentucky's 1998 study; however, the results were substantially lower than the results above. In August 1997, the University of Kentucky also collected and analyzed deer tissue (liver, fat, muscle, and mammary tissue), but detected no Aroclor 1248, 1254, or 1260. | ||||||||
| Key: µg/g = micrograms per gram; ppm = parts per million; PCBs = polychlorinated biphenyls; WKWMA = Western Kentucky Wildlife Management Area | ||||||||
Table 17B. Maximum concentrations of radioactive
contaminants in biota near PGDP (in pCi/g)1
| Sample | Biota | Type | Tc-99 | U-234 | U-235 | U-238 | Th-230 | Pu-239 | Am-241 | Np-237 | Sr-90 | Cs-137 |
| Fish | Bass | Tissue | 1.8 | |||||||||
| Fish | Bluegill | Unknown | 0.11 | 0.02 | 0.007 | 0.006 | 0.003 | ND | ND | |||
| Fish | Carp/catfish | Unknown | 0.33 | 0.017 | 0.003 | 0.003 | 0.011 | ND | ND | |||
| Fish | Sunfish | Tissue | 6.0 | |||||||||
| Fish | AVERAGE | 2.1 | 0.019 | 0.005 | 0.005 | 0.007 | ||||||
| Game | Deer | Bone | 61 | 2.04 | 0.12 | 2.51 | 0.29 | 0.02 | 0.08 | 0.01 | 4.6 | ND |
| Game | Deer | Liver | 9.9 | 1.83 | 0.072 | 1.58 | 0.02 | 0.03 | 0.062 | 0.01 | ND | ND |
| Game | Deer | Muscle | 2.62 | 0.07 | 0.072 | 1.29 | 0.05 | 0.49 | 0.062 | 0.00 | 0.09 | 0.02 |
| Game | Rabbit | Muscle | ND | 0.01 | ND | ND | ND | ND | ND | ND | ND | |
| Game | Racoon | Unknown | 0.15 | 0.01 | 0.00 | 0.00 | ND | 0.00 | ||||
| Game | Squirrel | Unknown | 0.41 | 0.01 | 0.00 | 0.00 | 0.001 | 0.00 | 0.00 | |||
| Game | AVERAGE | 14.8 | 0.66 | 0.05 | 1.08 | 0.09 | 0.11 | 0.06 | 0.005 | 2.3 | 0.02 | |
| Apple | Apple | Unknown | 0.21 | 0.017 | 0.003 | 0.005 | 0.001 | 0.000 | ND | |||
| Green vegetable | Cabbage | Unknown | 0.01 | 0.010 | 0.001 | 0.002 | 0.000 | 0.000 | 0.000 | |||
| Green vegetable | Cucumber | Unknown | 0.15 | 0.018 | 0.005 | 0.001 | 0.008 | 0.002 | 0.002 | |||
| Green vegetable | Pea | Unknown | 0.09 | 0.030 | 0.005 | 0.001 | 0.004 | 0.000 | 0.001 | |||
| Green vegetable | Pepper | Unknown | 0.09 | 0.011 | 0.005 | 0.002 | 0.002 | 0.000 | 0.000 | |||
| Green vegetable | AVERAGE | 0.09 | 0.017 | 0.004 | 0.001 | 0.003 | 0.000 | 0.001 | ||||
| Grapes | Grape | Unknown | 0.14 | 0.017 | 0.003 | 0.005 | 0.000 | 0.000 | 0.000 | |||
| Persimmon | Persimmon | Unknown | 188 | 0.032 | 0.008 | 0.008 | 0.002 | 0.001 | 0.000 | |||
| Nut, legume | Green bean/soybean | Unknown | 17.2 | 0.005 | 0.003 | 0.001 | 0.001 | 0.000 | 0.001 | |||
| Tomato | Tomato | Unknown | 0.35 | 0.025 | 0.016 | 0.011 | 0.010 | 0.002 | 0.003 | |||
| Yellow vegetable | Eggplant | Unknown | 0.01 | 0.001 | 0.002 | 0.001 | 0.000 | 0.000 | 0.000 | |||
| Yellow vegetable | Mixed vegetables | Unknown | 0.14 | 0.005 | 0.002 | 0.001 | 0.002 | 0.000 | 0.000 | |||
| Yellow vegetable | Carrots | Unknown | 0.11 | 0.007 | 0.001 | 0.005 | 0.001 | 0.000 | 0.000 | |||
| Yellow vegetable | Corn | Unknown | 0.74 | 0.068 | 0.009 | 0.012 | 0.003 | 0.001 | 0.003 | |||
| Yellow vegetable | Squash | Unknown | 0.22 | 0.017 | 0.162 | 0.010 | 0.006 | 0.001 | 0.002 | |||
| Yellow vegetable | AVERAGE | 0.24 | 0.02 | 0.035 | 0.06 | 0.002 | 0.000 | 0.001 | ||||
| 1 Concentrations
are the maximum values from DOE's 1987-2000 electronic database, except
AVERAGE, which is the average of maximum in a group. Other exceptions are
indicated. 2 Concentrations are the maximum values from Kentucky's Analytical Draft Report for Deer Harvest 2000 [92]. |
||||||||||||
Food and Biota Exposure Pathways
ATSDR scientists identified completed and potential pathways of human exposure to plants and animals containing contaminants of concern.
ATSDR scientists estimated human exposure doses using the maximum and average contaminant concentrations in Tables 17A and 17B and other conservative assumptions. We estimated exposure doses for a child (1 to 6 years old) who weighs 13 kg and for an adult who weighs 70 kg. We assumed average food consumption rates for persons from the United States in each biota category (Table 18). For fish consumption, we assumed average intake rates for subsistence fishers and their children and for recreational fishers and their children. We also assumed that 20% of all food in a person's diet was harvested from a contaminated source. Estimated chemical exposure doses are in Tables 19A and 19B for a child and an adult, respectively. The estimated doses (total committed doses) for radioactive contaminants are in Tables 20A and 20B for children and adults, respectively.
Table 18. Average food consumption rates for children and adults1
| Age Group | Fish (g/day) |
Game (g/day) |
Apples, Grapes (g/kg/day) |
Persimmons (g/kg/day) |
Nuts, Legumes (g/kg/day) |
Green Vegetables (g/kg/day) |
Yellow Vegetables (g/kg/day) |
Tomatoes (g/kg/day) |
|
| S | R | ||||||||
| Child (1 to 6 years) |
3 | 0.85 | |||||||
| Adult | 8 | 0.85 | |||||||
| 1 Fish consumption rates are for average subsistence fishers and recreational fishers. Intake rates for all other types of biota are based on average U.S. persons (for game), average U.S. per capita rates (for persimmons), or southern U.S. per capita rates (for apples, nuts, legumes, dark green vegetables, yellow vegetables, and tomatoes). | |||||||||
| Sources: Fish = Columbia
River Inter-Tribal Fish Commission (CRITFC), 1994, and EPA Exposure Factors
Handbook (EFH), 1999. Game = U.S. Dairy Association (USDA) Nationwide Consumption Survey, 1987-1988, in EPA, 1995 [93]. Apples, nuts, legumes, dark green vegetables, yellow vegetables, and tomatoes = EPA, 1995 [93], reference EPA, 1984d. Grapes and persimmons = U.S. EPA's Dietary Risk Evaluation System (DRES), in EPA, 1995 [93]. |
|||||||||
| Key: g/day = grams per day; g/kg/day = grams of food per kilogram of body weight per day; S = subsistence; R = recreational | |||||||||
ATSDR scientists then compared the total estimated exposure doses for chemicals to appropriate health guidelines. Tables 19A and 19B illustrate this comparison. (Appendix C of this report describes the health guidelines we used.) Only the PCB exposure doses for specific exposure scenarios exceed the health guideline; they will be discussed further in the public health implications section. For radioactive materials, the estimated annual committed effective doses for this exposure pathway are less than 1 millirem, which would not cause an adverse health effect. Nonetheless, the public health implications section discusses exposure to radioactive contaminants for each exposure pathway; therefore, they are included in Table 21.
Table 19A. Maximum estimated child exposure doses
and health guidelines for consumption of biota near PGDP for chemical contaminants
(in milligrams per kilogram of body weight per day)
| Chemical | Fish (Tissue) |
Game (Meat) |
Apples | Persimmons | Nuts, Legumes | Yellow or Green Vegetables | Estimated Total Exposure Dose per Chemical | Health Guide-line1 | Is Total Exposure Dose > Health Guideline? |
| Aluminum | 0.0535 | 0.00036 | 0.01939 | 0.00004 | 0.01433 | 0.03135 | 0.11897 | 2.00 | No |
| Arsenic | 0.00022 | 0.00000 | 0.00003 | ND | 0.00002 | 0.00005 | 0.0003 | 0.0003 | No |
| Barium | 0.00074 | 0.00017 | NR | NR | 0.00672 | NR | 0.00763 | 0.07 | No |
| Beryllium | NR | 0.00001 | ND | ND | ND | ND | 0.00001 | 0.002 | No |
| Cadmium | NR | 0.00009 | ND | NR | NR | NR | 0.00009 | 0.0002 | No |
| Chromium | 0.00126 | 0.00002 | 0.00067 | 0.00000 | 0.00046 | 0.00026 | 0.00267 | 1.00 | No |
| Copper | 0.00668 | 0.00037 | 0.00490 | 0.00001 | 0.00334 | 0.01132 | 0.02662 | 0.04 | No |
| Fluoride | 0.0043 | 0.0043 | 0.05 to 0.06 | No | |||||
| Lead | 0.00120 | 0.00004 | 0.00058 | 0.00000 | 0.00019 | 0.00042 | 0.00243 | 0.02 | No |
| Manganese | 0.00526 | 0.00005 | 0.00102 | 0.00005 | 0.01522 | 0.01068 | 0.03228 | 0.14 | No |
| Mercury | 0.00014 | 0.00007 | ND | ND | ND | ND | 0.00021 | 0.0003 | No |
| Nickel | NR | 0.00012 | 0.00230 | 0.00000 | 0.00139 | 0.00508 | 0.00889 | 0.02 | No |
| Selenium | 0.00028 | 0.00002 | ND | ND | ND | ND | 0.0003 | 0.005 | No |
| Silver | NR | 0.00009 | ND | ND | ND | ND | 0.00009 | 0.005 | No |
| Uranium | NR | 0.00003 | NR | NR | NR | NR | 0.00003 | 0.002 | No |
| Vanadium | ND | 0.00001 | ND | NR | NR | NR | 0.00001 | 0.003 | No |
| Zinc | 0.01815 | 0.00060 | 0.00371 | 0.00001 | 0.00238 | 0.00874 | 0.03359 | 0.3 | No |
| Total PCBs | 0.00387 | 0.00000 | 0.00387 | 0.00002 | Yes | ||||
| PCB (Aroclor 1254) | 0.00164 | 0.00164 | 0.00002 | Yes | |||||
| 2 For an explanation of health guidelines and exposure calculations, refer to Appendix C. | |||||||||
| Key: NR = not reported; ND = not detected; PCBs = polychlorinated biphenyls | |||||||||
Table 19B. Maximum estimated adult exposure doses
and health guidelines for consumption of biota near PGDP for chemical contaminants
(in milligrams per kilogram of body weight per day)
| Chemical | Fish (Tissue) |
Game (Meat) |
Apples, Grapes | Persimmons | Nuts, Legumes | Yellow Vegetables | Estimated Total Exposure Dose per Chemical | Health Guide-line1 | Is Total Exposure Dose > Health Guideline? |
| Aluminum | 0.02983 | 0.00013 | 0.01939 | 0.00004 | 0.01433 | 0.03135 | 0.09507 | 2.00 | No |
| Arsenic | 0.00012 | 0.00000 | 0.00003 | NR | 0.00002 | 0.00005 | 0.00022 | 0.0003 | No |
| Barium | 0.00041 | 0.00006 | NR | NR | 0.00672 | NR | 0.00719 | 0.07 | No |
| Beryllium | NR | 0.00000 | NR | NR | NR | NR | 0.00000 | 0.002 | No |
| Cadmium | NR | 0.00003 | NR | NR | NR | NR | 0.00003 | 0.0002 | No |
| Chromium | 0.00070 | 0.00001 | 0.00067 | 0.00000 | 0.00046 | 0.00026 | 0.00210 | 1.00 | No |
| Copper | 0.00372 | 0.00014 | 0.00490 | 0.00001 | 0.00334 | 0.01132 | 0.02341 | 0.04 | No |
| Fluoride | NR | NR | NR | NR | NR | NR | 0.0043 | 0.05 to 0.06 | No |
| Lead | 0.00067 | 0.00001 | 0.00058 | 0.00000 | 0.00019 | 0.00042 | 0.00187 | 0.02 | No |
| Manganese | 0.00293 | 0.00002 | 0.00102 | 0.00005 | 0.01522 | 0.01068 | 0.02992 | 0.14 | No |
| Mercury | 0.00008 | 0.00003 | NR | NR | NR | NR | 0.00011 | 0.0003 | No |
| Nickel | 0.00005 | 0.00230 | 0.00000 | 0.00139 | 0.00508 | 0.00882 | 0.02 | No | |
| Selenium | 0.00015 | 0.00001 | NR | NR | NR | NR | 0.00016 | 0.005 | No |
| Silver | NR | 0.00003 | NR | NR | NR | NR | 0.00003 | 0.005 | No |
| Uranium | NR | 0.00001 | NR | NR | NR | NR | 0.00001 | 0.002 | No |
| Vanadium | NR | 0.00000 | NR | NR | NR | NR | 0.00000 | 0.003 | No |
| Zinc | 0.01011 | 0.00022 | 0.00371 | 0.00001 | 0.00238 | 0.00874 | 0.02517 | 0.3 | No |
| Total PCBs | 0.00215 | 0.00000 | NR | NR | NR | NR | 0.00215 | 0.00002 | Yes |
| PCB (Aroclor 1254) | 0.00092 | NR | NR | NR | NR | NR | 0.00092 | 0.00002 | Yes |
| 1 For an explanation of health guidelines and a discussion of the dose calculations, refer to Appendix C. | |||||||||
| Key: NR = not reported; PCBs = polychlorinated biphenyls | |||||||||
Table 20A. Estimated child exposure doses (annual
committed effective doses) for annual consumption of biota near PGDP in millirems
(and in millisieverts) [58]
| Radioactive Contaminant | Fish | Game (meat) |
Apples, Grapes | Other Fruit (Persimmons) |
Nuts, Legumes | Dark Green Vegetables | Yellow Vegetables1 | Tomatoes | Total Estimated Committed Effective Dose |
| Technetium 99 | 0.018 (1.8E-04) |
0.009 (9.2E-05) |
0.003 (2.7E-05) |
0.006 (6.1E-05) |
0.167 (1.67E-03) |
0.001 (6.0E-06) |
0.001 (1.1E-05) |
0.002 (2.3E-05) |
0.21 (2.1E-03) |
| Uranium 234 | 0.006 (6.3E-05) |
0.016 (1.6E-04) |
0.008 (8.4E-05) |
0.000 (0.000) |
0.002 (1.9E-05) |
0.005 (4.5E-05) |
0.004 (3.5E-05) |
0.006 (6.2E-05) |
0.05 (4.6E-04) |
| Uranium 235 | 0.002 (1.6E-05) |
0.001 (1.1E-05) |
0.001 (1.4E-05) |
0.000 (0.000) |
0.001 (1.1E-05) |
0.001 (1.0E-05) |
0.006 (6.0E-05) |
0.004 (3.8E-05) |
0.02 (1.6E-04) |
| Uranium 238 | 0.002 (1.5E-05) |
0.023 (2.3E-04) |
0.002 (2.2E-05) |
0.000 (0.000) |
0.000 (3.0E-06) |
0.000 (2.0E-06) |
0.010 (9.6E-05) |
0.003 (2.5E-05) |
0.04 (3.9E-04) |
| Thorium 230 | 0.008 (8.2E-05) |
0.008 (7.5E-05) |
0.002 (1.7E-05) |
0.000 (0.000) |
0.001 (1.3E-05) |
0.003 (2.8E-05) |
0.001 (1.2E-05) |
0.009 (8.7E-05) |
0.03 (3.1E-04) |
| Plutonium 239 | 0.010 (9.8E-05) |
0.000 (0.000) |
0.002 (1.9E-05) |
0.01 (1.2E-04) |
|||||
| Americium 241 | 0.004 (4.4E-05) |
0.00 (4.4E-05) |
|||||||
| Neptunium 237 | 0.000 (2.0E-06) |
0.001 (6.0E-06) |
0.000 (4.0E-06) |
0.000 (3.0E-06) |
0.001 (1.2E-05) |
0.00 (2.7E-05) |
|||
| Strontium 90 | 0.029 (2.9E-04) |
0.03 (2.9E-04) |
|||||||
| Cesium 137 | 0.000 (1.0E-06) |
||||||||
| Estimated
annual committed effective dose |
0.036 (3.6E-04) |
0.100 (1.0E-03) |
0.016 (1.6E-04) |
0.006 (6.1E-05) |
0.172 (1.7E-03) |
0.010 (9.5E-05) |
0.022 (2.2E-04) |
0.027 (2.7E-04) |
0.39 (3.9E-03) |
|
Total estimated annual committed effective dose for all above radioactive contaminants in food crops is 0.39 millirems (or 3.9E-03 millisieverts) | |||||||||
| 1 "Yellow vegetables," in this table, includes eggplant, mixed vegetables, soybeans, carrots, corn, and squash. | |||||||||
Table 20B. Estimated adult exposure doses (annual
committed effective doses) for annual consumption of biota near PGDP in millirems
(and in millisieverts) [58]
| Radioactive Contaminant | Fish | Game (meat) |
Apples, Grapes | Other Fruit (Persimmons) |
Nuts, Legumes | Dark Green Vegetables | Yellow Vegetables1 | Tomatoes | Total Estimated Committed Effective Dose |
| Technetium 99 | 0.024 (2.4E-04) |
0.005 (5.1E-05) |
0.004 (4.1E-05) |
0.009 (9.1E-05) |
0.250 (2.5E-03) |
0.001 (0.9E-05) |
0.002 (1.7E-05) |
0.003 (3.4E-05) |
0.298 (29.8E-04) |
| Uranium 234 | 0.017 (1.7E-04) |
0.018 (1.8E-04) |
0.025 (2.5E-04) |
0.000 (0.1E-05) |
0.006 (5.6E-05) |
0.014 (1.4E-04) |
0.011 (1.1E-04) |
0.019 (1.9E-04) |
0.110 (11.0E-04) |
| Uranium 235 | 0.004 (4.3E-05) |
0.001 (1.3E-05) |
0.004 (4.3E-05) |
0.000 (0.000) |
0.003 (3.2E-05 ) |
0.003 (3.0E-05) |
0.018 (1.8E-04) |
0.011 (1.1E-04) |
0.044 (4.4E-04) |
| Uranium 238 | 0.004 (4.1E-05) |
0.026 (2.6E-04) |
0.007 (6.8E-05) |
0.000 (0.000) |
0.001 (1.0E-05) |
0.001 (0.7E-05) |
0.029 (2.9E-04) |
0.008 (7.5E-05) |
0.076 (7.6E-04) |
| Thorium 230 | 0.027 (2.7E-04) |
0.010 (1.0E-04) |
0.006 (6.4E-05) |
0.000 (0.000) |
0.005 (4.8E-05 ) |
0.010 (1.0E-04) |
0.005 (4.5E-05) |
0.032 (3.2E-04) |
0.095 (9.5E-04) |
| Plutonium 239 | 0.015 (1.5E-04) |
0.000 (0.000) |
0.008 (7.6E-05) |
0.023 (2.3E-04) |
|||||
| Americium 241 | 0.007 (6.5E-05) |
0.007 (0.7E-04) |
|||||||
| Neptunium 237 | 0.000 (0.3E-05) |
0.003 (2.5E-05) |
0.002 (1.8E-05) |
0.001 (1.2E-05) |
0.005 (5.0E-05) |
0.011 (1.1E-04) |
|||
| Strontium 90 | 0.035 (3.5E-04) |
0.035 (3.5E-04) |
|||||||
| Cesium 137 | 0.000 (0.1E-05) |
0.000 (0.0E-04) |
|||||||
| Estimated annual committed effective dose | 0.076 (7.6E-04) |
0.117 (11.7E-04) |
0.047 (4.7E-04) |
0.009 (9.2E-05) |
0.267 (2.67E-03) |
0.030 (3.0E-04) |
0.065 (6.5E-04) |
0.085 (8.5E-04) |
0.699 (7.0E-03) |
|
Total estimated annual committed effective dose for all above radioactive contaminants in food crops is 0.70 millirems (or 7.0E-03 millisieverts) | |||||||||
| 1 "Yellow vegetables," in this table, includes eggplant, mixed vegetables, soybeans, carrots, corn, and squash. | |||||||||
Chemical and radioactive contaminants have been detected in fish samples from Little Bayou and Big Bayou Creeks and from outfalls east of the plant. Most of the biota sampling data reflect current or recent past conditions.
The estimated total annual committed effective doses for all radioactive contaminants in biota do not exceed 1 millirem. This level would not produce an adverse health effect; however, radioactive materials from the combined exposure pathways will be discussed in the public health implications section.
The estimated total exposure doses for total PCBs and Aroclor 1254 exceed the health guidelines. PCB exposure doses were calculated under two different exposure scenarios (subsistence fishers and recreational fishers) for adults and children in Big Bayou Creek, Little Bayou Creek, and Outfall#11/Little Bayou Creek. Outfall #11 had the highest concentrations of PCBs in fish. This outfall has restricted access and is posted with fish consumption advisory signs [47]. It is unlikely that anyone would regularly fish in Outfall #11 and/or regularly eat fish caught at Outfall #11. Fish collected from Little Bayou Creek had higher PCB concentrations than fish from Big Bayou Creek. (Our site visits and observations indicate that people are more likely to fish in Big Bayou Creek.) It should be noted that the Ohio River provides a more extensive fishing area and offers easier access; therefore, fishing in the PGDP area is probably rarer than we estimate it to be. PCB analyses were not conducted for food crops; however, uptake of PCBs by plants is very low [95], and fish consumption would be the main exposure pathway for PCBs. ATSDR's assumptions are conservative and may overestimate exposure doses. Despite uncertainties in estimating human exposure doses, total PCBs and Aroclor 1254 were selected as contaminants of concern for current biota exposure pathways.
Since the majority of off-site releases occurred in the 1950s and early 1960s, and no sampling data are available for that time period, ATSDR scientists assumed that higher concentrations of chemical and radioactive contaminants in biota were possible. Also, outfalls to the creeks would not have been posted or restricted as they now are. Having discussed the matter with staff at the Kentucky Department for Environmental Protection, however, we believe that very few fish, if any, lived in Little Bayou Creek during these early years and very few people, if any, chronically fished in these areas. Since there were better places to fish in close proximity, we believe fishers would not have routinely fished in this creek system; however, despite the uncertainties, we selected total PCBs and Aroclor 1254 as contaminants of concern for past biota exposure pathways.
With access restrictions to areas near Outfalls #10 and #11 and posting of signs along Little Bayou Creek, potential future chronic exposure is not expected. However, other off-site fishing areas, such Big Bayou Creek and some nearby ponds, are potential sources of fish with chemical and radioactive contaminants and should continue to be monitored. Until the site remediation is completed, crops and game may continue to be contaminated at low levels. Therefore, ATSDR scientists identified potential future exposure pathways for biota. If additional biota sampling data become available, these human exposure pathways will be re-evaluated.
Table 21. Summary of potential exposure pathways for
human consumption of biota near PGDP
| Major Source | Contaminants | Point of Exposure | Route of Exposure | Exposed Population | Period of Time | Maximum Estimated Exposure Doses |
| Plant operations and waste disposal activities that release contaminants to soil, surface water, and air that are transported to creeks and pond near the plant | Total PCBs Aroclor 1254
|
Fish from Little Bayou Creek
|
Ingestion
|
Children and adults who eat 20% of their fish intake from
Little Bayou and Big Bayou creeks
|
Past, Current, and Potential Future Access to Little Bayou creek is partially restricted and fishing advisories are posted |
Total PCBs Adults: 0.00215 mg/kg/d Children: 0.00387 mg/kg/d PCB--Aroclor 1254 Radioactive Contaminants |
| Key: mg/kg/d = milligrams of contaminant per kilogram of body weight per day; mrem = millirems; mSv = millisieverts | ||||||
Storage of Depleted Uranium Cylinders
Uranium hexafluoride (UF6) is a solid stored under vacuum in steel cylinders in outdoor storage yards [96]. Most of the cylinders are 12 feet (about 3 ½ meters) long and 4 feet (about 1 meter) in diameter, with a nominal wall thickness of 5/16 inch (8 millimeters). The largest storage area at PGDP is in the southeast corner of the site. There are about 40,351 cylinders of depleted UF6 stacked two layers high at Paducah; 28,351 of them were generated by DOE and about 12,000 came from the U.S. Enrichment Corporation (USEC)(5) [5,97].
Although DOE believes that these cylinders do not present a health concern directly, the storage of large quantities of this material in one place has raised concerns among the local community and others. In 1994 and 1995, the Defense Nuclear Facilities Safety Board visited the gaseous diffusion plants at Paducah, Portsmouth, and Oak Ridge, Tennessee [98]. Their recommendation included a program to better maintain the physical condition of the cylinders, to better protect the cylinders from exposure to the elements and from damage during handling, and to study the feasibility of storing the material in a more suitable chemical form for long-term storage of the depleted uranium. In 1995, DOE submitted a plan to implement these recommendations. The plan included repainting cylinders to avoid excessive corrosion, removing cylinders from ground contact, spacing cylinders better to facilitate improved inspections, and improving handling procedures. DOE also completed a baseline inspection of all cylinders in 1994. Their plan calls for inspecting 25% of the cylinders each year and inspecting all the older cylinders each year [96].
Depleted UF6 is a white, crystalline solid when it is stored at temperatures below 134oF (57oC) at atmospheric pressure [5]. If one of the cylinders leaked, the UF6 would react with moisture in the atmosphere to form hydrogen fluoride (HF) gas and uranium reaction products such as solid uranyl fluoride. The solid would seal small leaks or cracks, preventing the escape of radioactive and chemical materials from the cylinders. If there were more severe damage to a cylinder, however, these materials might escape into the atmosphere and be a potential source of exposure to nearby residents.
Because the cylinders are currently being stored outside, the community is concerned about the possibility of a major accident that would damage the cylinders and result in large-scale release of UF6, and other reaction products, to the environment. Severe lightning storms, tornadoes, earthquakes, transportation accidents, plane crashes, or terrorist acts are examples of major accidents. These are discussed below.
A search of storm event data from the National Oceanographic and Atmospheric Administration's National Climatic Data Center (NCDC) revealed historical information for Ballard and McCracken counties in Kentucky [99]. Information on tornado activity is available from January 1, 1950, through December 31, 1991, and from January 1, 1995, through December 1998. During these 46 years, two tornadoes were recorded in Ballard County, with winds ranging from 40 to 206 miles per hour (64 to 332 kilometers per hour). In McCracken County, seven tornadoes and one funnel cloud were recorded, with winds from 73 to 157 miles per hour (118 to 253 kilometers per hour). These are considered small to mid-size tornadoes. Other severe weather conditions causing property damage, injury, or death have only been recorded by NCDC from January 1, 1995, through December 31, 1998. During these 4 years, Ballard County and McCracken County each had one lightning storm that caused property damage. Due to the cylinders' weight (each weighs 10 to 14 tons, or 9 to 12 metric tons), shape, and design, it is improbable that one of these storms would damage or move the cylinders. Also, lightning is usually attracted to the highest structure in the area--which would not be the cylinder yards--and it is not common for lightning to cause property damage in this area.
The New Madrid earthquake seismic zone includes western Kentucky. Although major earthquakes are not commonly considered a current problem for this area, it is true that one of the largest earthquakes in U.S. history (a 7.3-magnitude earthquake in 1812) had its epicenter 60 miles (97 kilometers) southwest of the site [100]. Researchers have provided varying estimates (or predictions) about how frequently accidents from earthquakes would occur in the area of PGDP [5,90,92,94].
Scientists at the U.S. Geological Survey estimate that the probability of a 6- to 7-magnitude earthquake occurring in this seismic zone within the next 50 years is very high. In contrast, DOE predicted that an earthquake-related accident is much less likely [5]. DOE's document, Programmatic Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of Depleted Uranium Hexafluoride [5], predicts the most likely types of accident (e.g., earthquake, transportation) that would affect each of the management strategies they proposed. Earthquakes were evaluated for long-term storage, use, and disposal of uranium oxide. DOE's estimated frequency for major earthquakes was one in 100,000 years, with 1 chance in 5,000 that an earthquake would occur in the next 40 years. They estimated that no additional cancer deaths would result from the release of uranium due to an earthquake-related accident; however, such an event is considered a low-frequency-high-consequence accident.
In 1997, USEC submitted an updated Safety Analysis Report to the U.S. Nuclear Regulatory Commission (NRC) that included a new seismic accident analysis for PGDP [101,102]. USEC identified equipment containing liquid UF6 that could fail during a 70-year return earthquake.(6) This equipment (an accumulator) is a reservoir used to hold liquid UF6 when cylinders are changed after being filled and during periods of equipment failure, etc. USEC determined that consequences from a 70-year return earthquake with full accumulators on site could include on-site fatalities and significant off-site injuries from exposure to UF6 and reaction products. NRC required immediate corrective actions to limit the amount of liquid in the accumulators and long-term corrective action to modify the equipment so it could withstand a design basis earthquake (a 250-year return earthquake). These modifications were completed by July 2000 [103,104].
Transportation and Plane Accidents or Terrorist Activities
Cylinders could be damaged or burn during transportation accidents, plane crashes, or terrorist attacks. Currently, cylinders are being transported between Allied Signal (which is on the other side of the Ohio River from PGDP) and PGDP. Also, some cylinders are being transported from PGDP to the Portsmouth Gaseous Diffusion Plant in Piketon, Ohio. Plane crashes are a possibility, since the Barkley Airport is about 3.7 miles (6 kilometers) southeast of the site. A plane crash accompanied by fire could damage the cylinders. As part of the Programmatic Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of Depleted Uranium Hexafluoride [5], Argonne National Laboratory used a FIREPLUME model to predict concentrations of materials released from cylinders containing UF6 under five accident scenarios and two different weather conditions (F and D stability cases) [105]. These scenarios include:
The model assumed that UF6 contained in cylinders was damaged in the accident, causing the release of HF gas and uranyl fluoride particulates to the atmosphere. For each scenario, they predicted concentrations at distances of 30 to 12,068 meters (about 100 feet to 7.5 miles) from the accident. They determined that the maximally exposed individual was 30 meters downwind of the accident. At each distance, the estimated dose was directly influenced by the airborne concentrations and the length of exposure time. The worst-case scenario (number 2) was a vehicle-induced fire with the rupture of three full 48Y cylinders (assuming F stability). Under this scenario, the maximally exposed individual would be exposed to 2,700 mg/m3 (or 3,293 ppm) of HF and 180 mg/m3 (or 2,250 ppm) of uranyl fluoride [105].
The estimated HF and uranyl fluoride exposure concentrations for the maximally exposed individual in accident scenario 2 (described on previous page) are high enough to pose a temporary urgent public health hazard; however, the probability of this type of accident occurring is very low. These substances are discussed below since they relate to this accident scenario. They may also be discussed in the public health implications section of this report.
HF is a colorless gas or liquid with a strong, irritating odor. It can be smelled in the air at concentrations of 0.5 to 3 ppm. The gas will readily react with water, releasing corrosive and toxic gases. Contact with metal can produce flammable hydrogen gas. Containers of HF can explode when heated or contaminated with water [106].
HF is highly corrosive and produces adverse effects at the point of contact, which is usually the respiratory tract (nose, throat, trachea, bronchi), eyes, and skin. Because HF is absorbed into the bloodstream, it can affect other organs in the body, such as the lungs, liver, kidney, and heart. Short-term exposure to HF in air at concentrations as low as 20 ppm can be tolerated for 1 minute, although concentrations of 120 ppm irritate the nose, throat, eyes, and skin in humans [106]. Vapors can cause ulcers of the respiratory tract at concentrations of 50 to 250 ppm--this concentration can be dangerous, even for brief exposures. Inhalation of HF at higher concentrations can cause severe throat irritation, cough, lung injury, and pulmonary edema (swelling) resulting in death. HF readily penetrates the skin and can cause deep tissue destruction and burns following dermal exposure. Exposure to the eye can result in irritation to severe ocular damage and visual effects.
The National Institute of Occupational Safety and Health recommends that exposure to HF by workers not exceed 3 ppm (or 2.5 mg/m3), with a 15-minute ceiling of 6 ppm (or 5 mg/m3). The recommendations are intended to protect workers from effects on the respiratory tract, eyes, skin, and bones. The recommendations are based on occupational studies of workers and laboratory animals. One study of rabbits and guinea pigs exposed to HF, at concentrations of 24 to 8,000 ppm for 5 to 41 minutes, reported eye and respiratory tract irritation at all exposure concentrations [107]. A significant number of animals died within 5 minutes when they inhaled air containing 1,500 mg/m3 of hydrogen fluoride. Weakness and appearance of illness were apparent in all animals at concentrations above 500 mg/m3 for 15 minutes or longer. Rabbits that survived returned to normal within a few weeks, but guinea pigs showed a definite tendency to delayed response and death between the fifth and tenth week following exposure.
Argonne's estimated exposure levels were at least 10 times higher than reported to cause adverse effects in humans (workers) and animals. Therefore, ATSDR concludes that potential future exposure to HF, at an estimated exposure level of 3,300 ppm for a hypothetical maximally exposed individual in accident scenario 2, poses an urgent health hazard.
Uranyl fluoride is a water-soluble compound of uranium. Its toxicity is determined primarily by route of exposure; exposure concentration, duration, and frequency; and particle size. Ingestion generally produces less toxicity than inhaled uranium, largely because uranium is so poorly absorbed from the gastrointestinal tract following ingestion. Respiratory and kidney (renal) toxicity are the targets for inhaled uranium.
ATSDR has developed an intermediate-duration health guideline for exposure to uranyl fluoride in air. The guideline is 0.0004 mg/m3 (or 0.005 ppm) and is based on a study in which dogs were exposed to uranyl fluoride in air daily for 5 weeks [108]. The lowest dose at which adverse effects on the kidney were observed in these animals was 0.15 mg/m3 (or 2 ppm). ATSDR applied a safety factor of 90 to this lowest dose, because humans may be more sensitive than dogs, some humans may be more sensitive than others, and there was no dose at which no adverse effects were seen. Although Argonne National Laboratory's estimated exposure concentration (180 mg/m3, or 2,250 ppm) was several orders of magnitude higher than the health guideline, the health guideline was based on an intermediate-duration study in which animals were exposed for 5 weeks. It is likely that exposure to uranyl fluoride during an accident will occur over a shorter (acute) duration.
A similar study in dogs acutely exposed to uranyl fluoride (one exposure lasting ½ to 1 hour) found extensive degeneration in kidney tissue following exposure at a concentration of 250 mg/m3 (more than 3,000 ppm) [108]. ATSDR considered these effects to be too severe to use the study as a basis for developing a health guideline. If we did derive a "guideline" by applying a similar safety factor of 90 to this concentration, the resulting "guideline" would be about 35 ppm. Argonne's estimated exposure concentration for uranyl fluoride, for the maximally exposed individual under scenario 2, was considerably higher than this "guideline." Therefore, ATSDR concludes that potential future exposure to uranyl fluoride, at an estimated exposure level of 180 ppm for a hypothetical maximally exposed individual in accident scenario 2, poses a public health hazard.
DOE is evaluating the feasibility of building a facility (or facilities) to convert its UF6 to a more stable form for long-term storage, use, or permanent disposal. DOE prefers to begin converting the depleted UF6 inventory to uranium oxide or uranium metal, or a combination of both, as soon as possible, but to allow for use of as much inventory as possible. Conversion to oxide for use or long-term storage would begin as soon as possible, with conversion to metal only if uses for the metal are identified [5]. DOE is now participating in a conversion pilot project with the private sector [109].
DOE stores the majority of its depleted uranium cylinders at PGDP. Most of the storage cylinders are not approved for transportation; therefore, it is logical that the conversion facilities would be built at or near the gaseous diffusion plants. On August 11, 1998, President Clinton signed Public Law 105-204 into law. This law (Section 1. United States Enrichment Corporation) states:
(a) Plan. -- The Secretary of Energy shall prepare, and the President shall include in the budget request for fiscal year 2000, a plan and proposed legislation to ensure that all amounts accrued on the books of the United States Enrichment Corporation for the disposition of depleted uranium hexafluoride will be used to commence construction of, not later than January 31, 2004, and to operate, an on-site facility at each of the gaseous diffusion plants at Paducah, Kentucky, and Portsmouth, Ohio, to treat and recycle depleted uranium hexafluoride consistent with the National Environmental Policy Act....(c) Sense of the Senate. - It is the sense of the Senate that Congress should authorize appropriations during fiscal year 2000 in an amount sufficient to fully fund the plan described in subsection (a).
(We assume that these facilities would also be used to dispose of DOE's depleted UF6.)
The community is concerned about transportation accidents that might occur if cylinders from other sites were brought to PGDP. Since conversion facilities are proposed at two sites, about 4,700 cylinders at Oak Ridge, Tennessee, would have to be transported. The material in these old cylinders will need to be transferred to DOT-approved transport cylinders or overpacks before the transfer occurs. ATSDR recommends using new DOT-approved transport cylinders or overpacks to transport any depleted uranium to or from PGDP.
The community is also concerned about potential environmental contaminants that the new facility might produce. The potential environmental contaminants from a conversion plant at a specific site are hard to predict until the technology is decided upon and the facilities are planned. When plans for the new facilities are proposed for the two sites, Environmental Impact Statements (EIS) required by the National Environmental Policy Act of 1969 will assess the site-specific impact of the proposed facilities on human and natural environments. DOE's final Programmatic Environmental Impact Statement [5] issued in April 1999 presented alternatives for long-term management of the depleted UF6 and included a comparison of impacts on human health and the environment for the alternative management strategies; however, it did not include the detailed, site-specific information that would be required in an EIS.
Potentially contaminated concrete rubble from PGDP was used at PGDP, the Tennessee Valley Authority Shawnee Steam Plant reservation, the Western Kentucky Wildlife Management Authority (WKWMA), and the Ballard County Wildlife Management Area approximately 11 miles (18 kilometers) west of PGDP, for bank erosion control, dam and structural support, and roadway stabilization [10,11]. Since the concrete was potentially contaminated, DOE and the Commonwealth of Kentucky surveyed the rubble piles and the adjacent soils and sediments. Contaminated soil piles were removed from an area at the WKWMA in July 1996; no further remedial actions are planned. The remaining rubble piles do not pose a public health hazard.
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