PUBLIC HEALTH ASSESSMENT
PADUCAH GASEOUS DIFFUSION PLANT (U.S. DOE)
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 the resulting adverse public health effects.
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, processing a gaseous form of uranium (uranium hexafluoride). TCE was used as a solvent to clean metal parts. Tc-99, a radioactive constituent of reprocessed uranium, was introduced at the site when uranium used in reactors was reprocessed and used at the site. 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 potentially 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 existing conditions and normal operations,
the Paducah Gaseous Diffusion Plant site poses no apparent public health hazard for the surrounding
community from current 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 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.
In the future, the rupture or destruction of one or more depleted uranium cylinders from a transportation accident involving a fire, a plane crash, severe weather, or natural disasters would create an urgent public health hazard for anyone near the damaged cylinders. Weather conditions and duration of exposure would affect the distance from the cylinders at which there would be a hazard; however, for transportation accidents, we predict that (1) the maximally exposed individual would be 100 feet (30 meters) or less from the cylinders and (2) an urgent public health hazard could exist out to 230 feet (70 meters) from the cylinders. Less-severe health effects could be experienced by individuals within several thousand meters of the cylinders. These types of accidents or incidences are unlikely but must continue to be recognized as possible.
In our assessment, 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 (DLs) 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 DLs for vinyl chloride and other TCE degradation products should be sensitive 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 pose an indeterminate public health hazard, 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. Also, in the past, it has been reported that UF6 was released at night through jets on top of the process buildings to accelerate the reduction of UF6 concentration in the process gas system in order to perform maintenance and inspection on process gas equipment. These releases, called "midnight negatives", potentially contained significant quantities of uranium and hydrogen fluoride; however, the quantities released and the frequency of releases are unknown. Currently, we have no reports of health effects related to these releases; 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.
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 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 gas. The gas is fed through diffusion
stages--compressors and converters. PGDP has 1,812 diffusion stages housed in six buildings, which
cover about 74 acres (30 hectares) [3]. The "product" (UF6 enriched in U-235 [4]) and "tails" (UF6
depleted in U-235) are removed and put in cylinders [5]. The product had been shipped to another
uranium enrichment facility in Piketon, Ohio for further enrichment; however, the Piketon
enrichment operation was shut down in the summer of 2001. PGDP has been upgraded to enrich
uranium up to 5% U-235 [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, water, and air cooling. Electricity for the diffusion processes came 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, but today it comes from a power-grid associated with these plants . 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 six 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 [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
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 and the plant did not become fully operational 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 metal 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 metal 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 metal plant stopped operating
in 1975 [13]. Also, between 1952 and 1986, PGDP operated several secondary smelters to recycle
scrap metals [14].
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 [15].
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 [16]. On July 28, 1998, USEC became a private-sector corporation licensed by the U.S. Nuclear Regulatory Commission.
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 [17].
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 [18]. 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 [19].
In March 1996, ATSDR 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 [20]. 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 [21]. 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 [22]. 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 [23]. 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 [24]. 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 [25]. 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 [26]. The addition of new housing subdivisions west of the city of Paducah accounts for the bulk of the growth [27]. 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 [28].
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) [26]. 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 [26]. 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 [29]. 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 Hinkleville Road (the old US Route 60; Figure 1), is the site of new subdivisions. A new US Route 60 has been 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 [30]. 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 2).
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 2. Property boundaries and other features
McCracken County, Kentucky has approximately 400 active farms with 45 to 50 operating near PGDP [31]. Soybeans, wheat, corn, and tobacco are the dominant crops being cultivated. The number of tobacco farms has declined, but the acreage used for this crop has been steady: farms have consolidated under fewer owners. The dominant crops grown in the area are mostly shipped to national and international markets. People grow their own vegetables for personal use, but this practice (as well as cultivating specialty crops for commercial sale) is on the decline. Approximately 350 head of dairy cattle and 4,000 head of beef cattle are 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 [8,9,32].
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 [33].
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 2). 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 [18]. 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) [17]. 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 [34]. 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 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 Bayou Creek before entering the Ohio River (Figure 1) [35,36]. 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 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) [8,9,32]. The monthly average temperatures vary from 34ºF (1ºC) during January to about 77ºF (26ºC) in July. The average annual temperature is 59ºF (14ºC).
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