Skip directly to search Skip directly to A to Z list Skip directly to site content

PUBLIC HEALTH ASSESSMENT

FEED MATERIALS PRODUCTION CENTER (US DOE)
[a.k.a. FERNALD ENVIRONMENTAL MANAGEMENT PROJECT]
HAMILTON AND BUTLER COUNTIES, OHIO

POTENTIAL EXPOSURE PATHWAYS

Soil Pathway

Background

Soil off site of the Fernald facility has become contaminated with uranium through several possible mechanisms. These include (1) releases to air as particulate emissions during production and waste incineration and deposition on soil, and (2) spills or leaks to soil from production processes, transport systems, or improper storage or disposal of uranium wastes.

Modeling of air particulate releases from the Fernald facility indicate that cumulative uranium deposition on soil was highest in the 1970s and remained steady or declined slightly until production operations stopped in 1988 (Shleien et al. 1995; Killough et al. 1998a). Maximum soil deposition occurred in areas east-northeast to southwest of the facility (Shleien et al. 1995; Killough et al. 1998a).

Facility records indicate that the majority of the uranium released from Fernald site to the atmosphere was relatively insoluble (Shleien et al. 1995; Killough et al. 1998a). The soluble fraction deposited on soil would have been dissolved in rain and surface water and leached rapidly into deeper soils, or would have been transported in surface runoff to Paddy=s Run and the storm sewer outfall ditch (DOE 1994). Essentially none of the soluble uranium released during the peak of operation in the 1950s and early 1960s is likely to have remained in soil in the 1980s and 1990s (Killough et al. 1998a). Less soluble forms of uranium (e.g., uranium oxides) may have remained in soil longer; however, even insoluble uranium compounds would have been removed from surface soil over time. Therefore, the chemical form of the uranium still remaining in surface soil after years of deposition is likely to have been uranium compounds of low solubility.

Uranium released as spills or leaks during process operations was likely to have been mixed with acids from cleaning operations (Voilleque et al. 1995). The presence of acid increases the mobility of uranium in water. Soluble uranium salts would have either leached into deeper soils, been dissolved in rain and surface water and transported off site, or have been converted to insoluble uranium compounds over time.

Environmental Data

Environmental sampling data used to evaluate human exposure to contaminated soil near the Fernald site were collected from 1971 to the present. Contractors for the Fernald facility began routine soil monitoring at the site in 1971. Sample depths for routinely collected samples changed over time. From 1971 to 1983, samples were taken at a depth of 0 to 10 centimeters (cm) from the surface. From 1983 to 1985, the sample depth was 0 to 5 cm. After 1986, samples were taken at two depths, 0 to 5 cm and 5 to 10 cm (Killough et al. 1998a).

Additional soil sampling events have been conducted at the site, from 1986 to the present, as a result of litigation, removals, and remedial investigation/feasibility studies (DOE 1972 - 1999; DOE 1994; Killough et al. 1998b). The majority of soil samples collected on site and off site were analyzed for total uranium, uranium 234, uranium 235, and uranium 238.

Of all the off-site samples, the highest uranium concentrations were found in samples collected along the northeastern and eastern facility boundary and along the outfall line leading from the site to the Great Miami River. In general, uranium levels are higher close to the facility boundary and decrease with increasing distance from the boundary (DOE 1972 - 1999; SED 1998).

Overall, the amount of information on concentrations of chemicals in off-site surface soils (except uranium) is limited. Soil samples collected off site were analyzed for metals and organic compounds (e.g., polyaromatic hydrocarbons, or PAHs) on a few occasions during the period from 1991 to 1993. These samples were collected at a depth of 0 to 6 inches below the ground surface from five different locations just east of the facility boundary. A greater number of samples, considered representative of background conditions, were collected northwest of the facility.

Several metals have been found at levels above media-specific comparison values in soils off site of the Fernald facility. These include arsenic, barium, beryllium, boron, chromium, lead, manganese, and thallium. Of these, beryllium and thallium were not evaluated further for soil pathways because (1) they were detected infrequently, (2) the maximum concentrations were just above the lower limit of analytical detection, and (3) the maximum concentrations were similar to (or lower than) background soil concentrations. Concentrations of organic compounds in off-site soils were lower than media-specific comparison values and were not evaluated further for soil pathways.

A summary of the environmental data used to evaluate chemicals in soil pathways for this site is presented in Table A-4 of Appendix A - Selection of Contaminants (for Potential Exposure Pathways).

Estimated Exposure Doses

ATSDR scientists evaluated past, current, and potential future exposure to chemicals in soil off site of the Fernald facility. Uranium and several metals (arsenic, barium, chromium, lead, and manganese) are the chemicals evaluated for this pathway.

ATSDR scientists also evaluated current and potential future exposure to radioactive contaminants in soil pathways. Uranium is the only radioactive contaminant evaluated for soil pathways. Past exposures to radioactive contaminants were addressed in the Fernald Dosimetry Reconstruction Project and the Fernald Risk Assessment Project (Voilleque et al. 1995; Shleien et al. 1995; Killough 1998a, 1998b; CDC 1998, 1999). A description of these projects, conducted by and for CDC, is provided in Appendix D of this report.

In estimating exposure doses for this pathway, we assumed that incidental ingestion is the primary route of exposure to soil contaminants. Although contaminated soils may become resuspended in air and be a source of inhalation exposure, this exposure route is discussed in the "Air Pathway" subsection of this report=s "Exposure Pathways Analyses" section.

In estimating exposure dose, ATSDR scientists evaluated a hypothetical exposure scenario. For this scenario, we assumed exposure to a child, 1 to 6 years old, who weighs 13 kg and who ingests maximum concentrations of uranium in surface soils while playing near the Fernald site. We assumed exposure to a child because children, with their immature or developing systems, may have increased sensitivity to the toxic effects of uranium. ATSDR does not have direct evidence that shows whether children currently play or have played near the facility boundary. Demographic data for Butler and Hamilton Counties indicate that 922 persons live within 1 mile of the Fernald facility. Of these, an estimated 110 persons are 6 years old or younger (as presented in the "Demographics" section of this report). The closest residence to the site is directly southeast of the site, and off-site contaminated areas are not restricted from public access. Therefore, children may have played near the site and been exposed to contaminated surface soil.

Most children ingest soil occasionally during play because of frequent hand-to-mouth activity and reliance on caregivers, rather than themselves, for hygiene. However, children vary greatly with respect to soil ingestion behavior (Calabrese and Stanek 1998). Also, individual children vary greatly with respect to their soil ingestion activities, ingesting relatively little soil one day and large amounts the next day. Some children ingest over 50 grams of soil in a single day. Historically it was thought that this subgroup of children, who are generally 1 to 6 years old, exhibited "pica" behavior or repeated ingestion of non-nutritive items such as soil. More recently, however, researchers believe that soil pica behavior may not be restricted to this special subgroup of children, but that most children on occasion display "pica-like" behavior (Calabrese and Stanek 1998).

Under the hypothetical exposure scenario for this pathway, we assumed that a child exhibits "pica-like" behavior and ingests 200 milligrams of soil per day, on a total of 35 days a year, for 4 consecutive years. These conservative assumptions are based on information from a recent review of soil ingestion studies (Calabrese and Stanek 1998). In this review, it was estimated that 72% of children ingest 200 milligrams (mg) or more of soil a total of 7 to 10 days a year, while 42% of children ingest this amount daily for 35 to 40 days of a year.

Chemicals

ATSDR scientists calculated two types of chemical exposure doses for exposure to uranium in soil for the hypothetical scenario (described above). These are a body dose and dose to the kidney.

The kidney is the target organ for chemical effects of ingested uranium. The chemical effects of uranium result only after the uranium is absorbed from the gastrointestinal tract into the bloodstream and transported (distributed) to the kidney. In estimating dose to the kidney, ATSDR scientists assumed that 5% of the uranium concentration in ingested soil is absorbed into the blood. This is a conservative assumption for two reasons. First, data from human ingestion studies and pharmacokinetic models indicate that maximum absorption of uranium from the gastrointestinal tract ranges from 2% to 4% for the most soluble forms (ATSDR 1999b; ICRP 1995a). Absorption generally decreases with decreasing water solubility of the uranium compound. Second, we assumed that all uranium in off-site soil was in a soluble form. This is a very conservative assumption, considering that a large fraction of the uranium released from the Fernald site was most likely insoluble (Killough et al. 1998a).

The gastrointestinal absorption of uranium does not vary substantially by age (ATSDR 1999b; ICRP 1995a). Recent information suggests that children 5 years old and older have rates of gastrointestinal absorption for uranium that are similar to those of adults (ICRP 1995a). Gastrointestinal absorption rates are not known for children less than 5 years old. Because there is no indication that children=s soil absorption rates in small children (younger than 5) are higher than those of adults, ATSDR scientists assumed that the absorption rate for a child is equal to the maximum absorption rate for adults (or 5%). In estimating dose to the kidney, we assumed that 12% of the absorbed uranium dose is distributed to the kidney (ICRP 1979, 1995a; Zhao and Zhao 1990).

ATSDR scientists also estimated chemical exposure doses (body doses) for current exposure to metals in soil via incidental ingestion. These estimated doses, and the corresponding health-based guidelines for metals, are presented in Table B-1 of Appendix B - Exposure Doses and Health-Based Guidelines (for Potential Exposure Pathways).

   
Health Guidelines for Chemical Uranium and Metals
   
    

There are two types of health guidelines for ingestion of chemical uranium and metals. The first is a body dose, presented as milligrams of uranium per kilogram of body weight per day (mg/kg/day). The second is dose to the kidney, which is available only for chemical uranium and is presented as a range of thresholds or minimum effect levels for kidney toxicity in units of micrograms (µg) of uranium per gram of kidney (or µg/g).

   

We compared our estimated exposure doses for ingestion of chemical uranium and metals in off-site soil to the health-based guidelines to determine whether further evaluation of potential public health hazard was warranted. Additional information about the health-based guidelines for uranium is provided in the "Public Health Implications" section of this report. Additional information about the health-based guidelines for metals is provided in Appendix B - Exposure Doses and Health-Based Guidelines (for Potential Exposure Pathways).

Radiation

For radiation effects, the bone surface is the primary target organ for ingested uranium. ATSDR scientists calculated two types of radiation doses for exposure to uranium in soil pathways. They are a committed effective dose (whole body) and a committed equivalent dose (bone surface). We estimated these doses for the hypothetical exposure scenario (described above) for soil pathways using ICRP=s models and methodology (ICRP 1995a).

As with chemicals, the radiation effects of uranium result only after the uranium is absorbed from the gastrointestinal tract into the bloodstream. ATSDR scientists assumed that 20% of the absorbed uranium is distributed to the bone of children in this age group (ICRP 1995a). Although the distribution of uranium to the bone is higher for children than adults, it is retained in the bone for a shorter period of time in children than in adults (ICRP 1995a).

Past Exposure

Past exposure to uranium was evaluated using environmental sampling data collected while the facility was operating. Above-background concentrations of uranium have been detected in surface soil samples collected off site of the Fernald facility since 1986 (DOE 1994). Historically, the highest uranium concentrations have been found just outside the eastern boundary of the facility. The maximum uranium soil concentration detected in this off-site area was 137 mg/kg in a sample (BS-3) collected at the eastern facility boundary in 1973 (DOE 1972 - 1999; Killough et al. 1998a). Because this area was accessible to the public, ATSDR scientists assumed that human exposure to this concentration could occur, and we estimated exposure doses based on this maximum concentration. Our estimated body doses and doses to the kidney for past exposure to a small child, via ingestion of uranium in this off-site soil sample, are presented in Table 6 (below).

Table 6. Estimated current and past chemical exposure doses for ingestion of uranium in surface soil off site of the Fernald facility by a small child

Exposure Route and Time

Maximum Exposure Concentration or Range
(mg/kg)

Estimated Body Dose* (mg/kg/day)

Estimated Kidney Dose*
(mg/g)

Current ingestion

18 to 87

3 x 10-5 to 1 x 10-4

9 x 10-6 to 4 x 10-5

Past ingestion

137

2 x 10-4

7 x 10-5

Key
mg/kg = milligrams of uranium per kilogram of soil
mg/kg/day = milligrams of uranium per kilogram of body weight per day
mg/g = micrograms of uranium per gram of kidney

* Equations used to estimate doses for this pathway are described in Appendix B - Exposure Doses and Health-Based Guidelines.

Our estimated chemical exposure dose is 10 times lower than the health-based guideline for ingested uranium, despite the fact that ATSDR scientists used conservative and not necessarily realistic assumptions about the amount and rate of soil ingestion (i.e., how much soil is ingested and how often) and uranium solubility. If more realistic assumptions were used, the estimated dose would have been considerably lower, perhaps as much as one 100 times lower than the dose presented in Table 6.

Although our estimated chemical dose is lower than the health-based guideline for ingested uranium, ATSDR scientists evaluated the public health hazard for this pathway together with other exposure pathways (i.e., groundwater, air, surface water, and biota) that contribute to total uranium exposure to Fernald residents. This evaluation is presented in the "Public Health Implications" section of this report.

The effects from past exposure to the radioactive uranium (and its decay products) in off-site soil have been addressed in the Fernald Dosimetry Reconstruction Project and the Fernald Risk Assessment Project (Voilleque et al. 1995; Shleien et al. 1995; Killough 1998a, 1998b; CDC 1998, 1999). A description of these projects is presented in Appendix D of this report.

Current Exposure

Contractors at the Fernald facility have been removing and remediating (cleaning up) contaminated soils on site and off site of the Fernald facility since 1989. Consequently, there are very few sources of current human exposure to off-site surface soil contaminants.

In estimating current exposure doses for chemical uranium in soil pathways, ATSDR scientists used a range of uranium exposure concentrations (18 mg/kg to 87 mg/kg). The upper bound of the range is the maximum uranium concentration found in any off-site surface soil sample. This concentration was detected in a sample collected just outside the eastern facility boundary (in 1989). Contaminated soil in this area was excavated (removed) in 1990, and, therefore, no longer represents a source of current exposure. The lower bound of the range is the maximum uranium concentration found in surface soil samples collected from areas that have not have been remediated and may represent current sources of human exposure. Based on sampling data contained in Fernald=s Site-Wide Environmental Database (SED), this concentration was detected in a sample (number 2393) collected south of the facility boundary in 1990 (SED 1998).

As shown in Table 6 (above), ATSDR=s estimated chemical exposure doses for ingestion of chemical uranium in off-site surface soil are 20 to almost 100 times lower than the health-based guideline for ingested uranium, despite the fact that we used conservative assumptions to estimate dose. ATSDR scientists evaluated the public health hazard for this pathway together with other exposure pathways (i.e., groundwater, air, surface water, and biota) that contribute to total uranium exposure to Fernald area residents. This evaluation is presented in the "Public Health Implications" section of this report.

ATSDR=s estimated exposure doses for ingestion of metals in off-site surface soil, and the corresponding health-based guidelines, are presented in Table B-1 of Appendix B - Exposure Doses and Health-Based Guidelines (for Potential Exposure Pathways). None of the estimated exposure doses exceed health-based guidelines for ingestion. No other exposure pathways identified for the site involved exposure to metals; therefore, we did not evaluate metal exposure for this or any other pathway.

In estimating current radiation doses for uranium in soil pathways, ATSDR scientists used a range of uranium concentrations, from 12 pCi/g to 58 pCi/g. The rationale for using this range is described (above) for chemical uranium. ATSDR=s estimated maximum current committed effective (whole-body) and committed equivalent (bone-surface) doses to a young child from ingestion of contaminated soil off site of the Fernald facility are presented in Table 7 (below). Further evaluation of human exposure to radioactive uranium in off-site soil, including a determination of whether these estimated doses indicate an increased likelihood of developing fatal cancers and bone cancer, is discussed in the "Public Health Implications" section of this report.

Table 7. Estimated current committed effective (whole-body) and committed equivalent (bone-surface) doses from 1 year of incidental ingestion of contaminated off-site surface soil by a child

 Target Organ

Range of Maximum Exposure Concentrations in pCi/g (Bq/g)

Range of Doses in mrem (mSv)

Whole body (committed effective dose)

12 to 58 (0.44 to 2.15)

0.02 to 0.12 (2.4E-04 to 1.2E-03)

Bone surface (committed equivalent dose)

12 to 58 (0.44 to 2.15)

0.37 to 1.8 (3.7E-03 to 1.8E-02)

Key
pCi/g = picocuries per gram
Bq/g = becquerels per gram
mrem = millirems
mSv = millisieverts


Potential Future Exposure

ATSDR scientists evaluated the likelihood that off-site areas will become a source of human exposure to contaminants from the Fernald site in the future. To do this, we used current measurements of contaminants in on-site and off-site soils and information about current and proposed remediation strategies for the site. Remediation activities at the Fernald site are expected to continue for several years. During that time, the former production buildings will be destroyed and contaminated soils around and under these buildings will be removed and transported to an off-site disposal area. Based on available sampling, there is no indication that future activities will result in human exposure to contaminated soils off site of the Fernald facility. However, if additional information becomes available indicating that contaminants have been released or migrated to soil off site, soil exposure pathways should be re-evaluated.

Air Pathway

Background

Air exposure pathways include contaminants released directly to air as particulate or gaseous emissions, and direct radiation (e.g., x-rays, gamma rays, energetic beta particles, neutrons.) They also include indirect releases to air from resuspension of particulates deposited on the ground surface.

The most important sources of past uranium releases to air from the site are the dust collectors in Plants 1, 2/3 and 8: and other monitored and unmonitored sources (e.g., cooling towers, wasted incinerators, waste pits, silos, and waste processing operations). Releases from these sources occurred continually throughout the operating history of the facility (Voilleque et al. 1995).

There were also several accidental, episodic releases of uranium to the atmosphere during the years when the Fernald facility was operating (Voilleque et al. 1995). Two of these events, one in 1953 and another in 1966, involved releases of large quanties of uranium hexafluoride (UF6) to the atmosphere. The 1966 accident was more serious, because a larger quantity of UF6 was released. This accident lasted 1 hour and involved a release of UF6 from a 10-ton cylinder. The cylinder was under pressure and a leak occurred when a valve unscrewed from the cylinder, expelling the pressurized gas. The escaping gas was vented to the atmosphere through a removable hood and carried by wind in a southeasterly direction over the Laboratory Building and the Administration Building, which were evacuated (Voilleque et al. 1995).

Airborne UF6 hydrolyzes rapidly with the moisture in air to form a soluble uranium compound, uranyl fluoride (UO2F2) and the gas hydrogen fluoride (HF). These products of UF6 hydrolysis can be more harmful than the parent compound. Contractors for the CDC used models to predict the concentrations of HF released to the atmosphere during the 1966 accident (Voilleque et al. 1995). They also estimates dose to the kidney from UO2 F2 exposure to a hypothetical individual located downwind of the release. These estimates are discussed in the "Estimated Exposure Doses" ("Past Exposure") section for this pathway.

The largest sources of radon 222 (which we will refer to as "radon" in this report) exposure and direct radiation to Fernald residents, under past conditions at the site, are the K-65 Silos (Silos 1 and 2), located on the western portion of the Fenald property. These silos contain residues left after extraction of uranium from pitchblende ores from the Belgian Congo. The residues contain high concentrations of radium 226, the parent of radon 222.  Airborne UF6 hydrolyzes rapidly with the moisture in air to form a soluble uranium compound, uranyl fluoride (UO2F2), and the gas hydrogen fluoride (HF). These products of UF6 hydrolysis can be more harmful than the parent compound. Contractors for the CDC used models to predict the concentrations of HF released to the atmosphere during the 1966 accident (Voilleque et al. 1995). They also estimated dose to the kidney from UO2F2 exposure to a hypothetical individual located downwind of the release. These estimates are discussed in the "Estimated Exposure Doses" ("Past Exposure") section for this pathway. Although the silos had 4-inch concrete domes, radon gas built up in the head spaces and was released to the atmosphere, especially through vents and other dome penetrators such as piping and manholes. In 1979, the major openings were sealed and the pipes removed. The past release of radon gas (before 1989), past direct radiation from the silos, and potential health effects from the resulting radiation exposures are extensively discussed in the Fernald Dosimetry Reconstruction Project and Fernald Risk Assessment Project (Voilleque et al. 1995; Shleien et al. 1995; Killough 1998a, 1998b; CDC 1998, 1999). A description of these projects is provided in Appendix D of this report.

Current and potential future releases of uranium and radon are occurring (or are likely to occur) as stack emissions from waste processing operations, lab emissions, and fugitive dust emissions from waste pits and remediation activities on site (DOE 1972 - 1999). Radon releases are also occurring from the K-65 silos on site. In 1991, a bentonite (clay) layer was added to the top of the K-65 silos, decreasing the release rate of radon gas and direct radiation levels. In recent years, direct radiation levels have appeared to increase near the K-65 silos (on-site). However, the current amount of radon, radon decay products, and direct radiation released from the silos is drastically lower since the facility stopped operating in 1988 and since the bentonite layer was added to the silos in 1991 (DOE 1972 - 1999).

Particle size and chemical form of uranium affect the transport of air releases to off-site locations where community residents may be exposed. These factors also affect the extent of human exposure, because particle size and chemical form influence the deposition of particles in the human respiratory tract and absorption into the bloodstream. In general, larger particles (greater than 10 microns in diameter) are transported short distances in the atmosphere and collect in the upper respiratory tract (i.e., nasal passages and pharynx) of exposed individuals. Smaller particles (less than 10 microns in diameter) are more readily transported in air and reach deeper regions of the respiratory tract. Larger particles may be cleared from the upper respiratory tract by coughing, or may be swallowed and then absorbed into the bloodstream through the gastrointestinal tract. More water-soluble compounds are more readily absorbed into the bloodstream from the lungs or gastrointestinal tract than less water-soluble uranium particles.

The particle size distributions of emissions from the Fernald processing areas varied widely from stack to stack. Measured particle size distributions and information about other uranium processing facilities were used to estimate particle size distributions for dust collectors and scrubbers at all Fernald processing plants (Voilleque et al. 1995; Shleien et al. 1995). The range of median particle sizes for dust collector emissions was 5.1 to 11 microns in diameter. About three-fourths of the releases from dust collectors were uranium oxides of low water solubility. The range of median particle sizes for scrubbers was 0.5 to 62 microns (Voilleque et al. 1995; Shleien et al. 1995). More than half of these emissions were uranium compounds of low solubility (e.g., uranium trioxide, triuranium octaoxide). Additional information about air particulate emissions from the Fernald facility is provided in Appendix E - Air Particulate Releases and ICRP Lung Models.

Environmental Data

ATSDR scientists used two general types of environmental sampling data to evaluate human exposure for the air pathway. These include measurements and estimates of uranium particulate emissions from scrubber and dust collector systems in processing plants on site, and routine monitoring for chemical and radioactive contaminants on site and off site.

The Fernald facility has conducted routine air monitoring at the site since 1960; however, systematic air monitoring for radon was not undertaken until the 1980s. The majority of air samples collected at the site have been analyzed for uranium, radon, and radon daughters. A smaller number of samples have been analyzed for other radionuclides, including radium 226 and 228; neptunium 237; plutonium 238 and 239; technetium 99; cesium 137; and thorium 228, 230, and 232 (DOE 1972 - 1999). These later radioactive contaminants have been released from the site in such small amounts that they are estimated to have contributed very little to overall airborne releases (Voilleque et al. 1995).

The Fernald facility began routine monitoring of uranium air particulates at the site in 1960. Because measurements were not made before 1960, contractors for CDC used computer models to predict past uranium airborne concentrations using known quantities of uranium emissions from stacks and vents on site (Voilleque et al. 1995; Shleien et al. 1995). From 1960 through 1970, continuous, high-volume samplers were located at the four corners of the fenced production area. Annual average uranium concentrations at these monitoring locations were highest in the early 1960s. The highest uranium concentration measured at these monitors was 0.518 mg/m3 at the southwest corner of the production area in 1960. These monitors were decommissioned after 1970 and six monitoring stations were established along the fenced property boundary. In 1981, an additional monitor was installed near the northwest corner of the property line (IT 1986).

During the period from 1973 to 1984, the highest annual average uranium concentrations measured at the property boundary were found at monitoring stations BS-1, BS-2, and BS-3, located north, northeast, and east of the facility, respectively. The highest annual average uranium concentration measured at these locations was 0.037 mg/m3, at monitoring station BS-3, located on the eastern property boundary (IT 1986).

By 1994, twenty monitoring stations were established on and off the Fernald property (DOE 1994). At that time, the facility began performing weekly analyses for total uranium and total suspended particulates. A fraction of each weekly sample was also composited for yearly analyses for several radionuclides, including radium 226 and 228; neptunium 237; plutonium 238 and 239; technetium 99; cesium 137; and thorium 228, 230, and 232 (DOE 1972 - 1999).

The Fernald facility began routine radon monitoring in July 1980. Alpha-track etch detectors (radon cups) had been used until the end of 1998 to collect airborne radon measurements at the site boundary and at various locations on and off the Fernald facility property. These detectors measure total radon concentration over an extended period and are returned to the manufacturer=s laboratory for analysis. Originally, the Fernald facility exchanged these detectors every 3 months; in later years, they exchanged them every 6 months.

In 1991, the facility installed real-time monitors (alpha scintillation detectors) to continuously monitor radon concentrations at some air monitoring stations on site, at the perimeter of the K-65 silo berm, in the head space of the silos, at the boundary of the site, and at two background locations. Real-time monitors operate continuously and provide radon concentration data in set time intervals, such as every hour.

The largest source of direct radiation at the site is the waste material stored in the silos. Gamma rays and x-rays are the dominant types of radiation emitted from this material. Integrated direct radiation measurements are taken quarterly at the site boundary and at on-site and off-site locations using thermoluminescent detectors (TLDs). The TLDs are used to indicate the relative energies associated with measured gamma radiation and provide a basis for converting radiation levels to a measure of whole body dose. TLDs are collected quarterly and counted at the Fernald laboratories; the data are reported in the annual Site Environmental Reports. In 1998, an increasing trend in radiation levels was identified at locations near the K-65 silos. However, the level was lower than the levels measured near the silos before the bentonite cap was added in 1991 (DOE 1972 - 1999).

Off-site sampling data are not available for all chemicals that may have been transported from on-site release sources to off-site locations where human exposure could occur. The boilers in the coal-fired steam plant at the western end of the production area are important sources of air particulate emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx). ATSDR scientists used computer models of air dispersion to predict levels of these contaminants in off-site air. The models required input data such as emission rates, release sources (e.g., stack heights), and meteorological data. Methods that ATSDR scientists used to model off-site concentrations of these contaminants, and the estimated concentrations, are described below.

Estimated Exposure Doses

ATSDR scientists evaluated past, current, and potential future exposure to chemicals in air off site of the Fernald facility. Uranium, SO2, NOx, and metals (arsenic, boron, chromium, and manganese) are the chemicals evaluated for this pathway. These metals were selected because they have been detected in off-site surface soils at concentrations that exceed media-specific comparison values (as discussed in the "Soil Pathway" subsection of the "Exposure Pathways Analyses," section of this report) and have been shown to be toxic to animals and humans when inhaled at sufficient doses (ATSDR 1999b, 1998c, 1998b, 1992, 1998a, 1997b). Metal-contaminated soil particulates may become resuspended in air, and represent a potential current source of human exposure via air pathways. Past exposure to hydrogen fluoride (HF) gas by nearby residents during an accidental release of uranium hexafluoride (UF6) is also discussed in this section.

ATSDR scientists also evaluated current and potential future exposure to radioactive contaminants in air and direct radiation off site of the Fernald facility. Uranium, radon, and radon daughters are the primary radioactive contaminants, and strontium 90; technetium 99; cesium 137; radium 226 and 228; thorium 228, 230, and 232; neptunium 237; plutonium 238 and 239 are secondary radioactive contaminants evaluated for this pathway. Collectively, we refer to all radionuclides evaluated for this pathway as "radioactive contaminants." Since exposures to radon and radon decay products are evaluated differently from the other radioactive airborne contaminants, ATSDR evaluated them as separate contaminants for the air pathway.

Past exposures to radioactive contaminants in air and to direct radiation were addressed in the Fernald Dosimetry Reconstruction Project and Fernald Risk Assessment Project (Voilleque et al. 1995; Shleien et al. 1995; Killough 1998a, 1998b; CDC 1998, 1999). A description of these projects is provided in Appendix D of this report.

Exposure to air contaminants may occur via inhalation of contaminants released directly to air from the Fernald site. In addition, contaminants released to air may be deposited onto soil or other ground surfaces and then become re-suspended (re-entrained) in air because of wind erosion or activities that disturb ground cover. Resuspension of deposited particulates represents an additional source of inhalation exposure to Fernald area residents, although it is estimated to contribute much less to exposure dose than direct inhalation of airborne releases (Killough et al. 1998b). We evaluated both types of exposures (inhalation of direct and indirect releases) for uranium. We evaluated only inhalation of indirect releases (soil resuspension) for metals, because there are no environmental measurements of metals in air at the site. We evaluated only inhalation of direct releases of SO2 and NOx from the site.

ATSDR scientists assumed that inhalation is the primary route of exposure, and ingestion the secondary route of exposure, to airborne contaminants. Ingestion is an important route when releases occur as large particles, greater than 10 microns in diameter. Particles of that size are deposited in the upper respiratory tract, transported upward by mucociliary action in the throat, and then swallowed.

   
Estimating Exposure Dose
   
    
ATSDR scientists evaluated two hypothetical exposure scenarios for exposure to chemical and radioactive contaminants in surface water pathways: (1) a child who plays near the site almost daily, and (2) a farmer who does heavy work near te site almost daily.
   

In estimating chemical and radiological doses, ATSDR evaluated two hypothetical exposure scenarios. The first scenario assumes exposure to a child, 1 to 6 years old and weighing 13 kg, who inhales (and ingests) airborne uranium while playing near the Fernald site. We assumed this child breathes 5 cubic meters of air per day (5 m3/day) while playing near the site for 10 hours a day, 351 days a year, for 6 consecutive years (EPA 1999).

We assumed exposure to a child because children, with their immature or developing systems, may have increased sensitivity to the toxic effects of uranium. ATSDR does not have direct evidence that show whether children play or have played close to the facility boundary. However, 1990 Census data for Butler and Hamilton Counties indicate that 922 persons live within 1 mile of the Fernald facility. Of these, an estimated 110 persons are 6 years old or younger (as discussed under "Demographics" in the "Background" section of this report). The closest residence to the site is directly southeast of the site, and access to off-site contaminated areas is not restricted. Therefore, ATSDR scientists made conservative assumptions in estimating exposure dose for inhalation (and ingestion) of airborne contaminants while playing near the Fernald facility.

The second hypothetical exposure scenario assumes exposure to an adult farm worker who weighs 70 kg and inhales (and ingests) maximum concentrations of uranium in air while working near the facility. We assumed this farmer breathes 51 m3/day while doing heavy work for 10 hours a day, 351 days a year, for 10 years or the period from 1989 through 1998 (EPA 1999). This is a realistic scenario, because several active farms are located near the Fernald facility.

Chemicals

ATSDR scientists calculated two types of doses for exposure to uranium in air for both hypothetical scenarios (described above). These are a body dose and a dose to the kidney.

In order to calculate exposure doses for uranium, ATSDR scientists used estimated and measured airborne concentrations of uranium and dosimetry models. We used dosimetry models to estimate the fraction of airborne uranium that is deposited in the various regions of the human respiratory tract, and the subsequent absorption from these regions into the blood (ICRP 1979, 1995a). The models are described in detail, together with the particulate size distributions for Fernald emissions, in Appendix E - Air Particulate Releases and ICRP Lung Models.

 

Because there are no measurements of metal concentrations in air at the Fernald site, ATSDR scientists estimated air concentrations using the maximum measured air concentrations of total suspended particulates (off site) and the maximum measured surface soil concentrations of metals (off site). We assumed that the suspended particulates were generated only by resuspension of surface soil, which is unrealistic but conservative. Surface soil concentrations of metals were measured on a few occasions in 1991 and 1993. No sampling data are available for the period when the facility was operating. Therefore, available data represent only current exposure conditions.

Assuming that 100% of the metal concentration in surface soil is resuspended into air, we estimated the current airborne concentration (conc.) of each metal using the following equation:

   

Airborne conc. (mg/m3) = soil conc. (mg/kg) x (1 kg/10-9µg) x particulate conc. (µg/m3)

where:

mg/m3           =  estimated number of milligrams of metal per cubic meter of air
mg/kg           =  measured number of milligrams of metal per kilogram surface soil (off site)
1 kg/10-9 µg  =  a conversion factor (to convert from kilograms to micrograms)
µg/m3            =  measured number of micrograms of total suspended particulate per cubic meter of air (off site)

   

We used our estimated airborne concentrations to estimate chemical exposure doses for metals in air pathways. Dosimetry models are not available for exposure to metal particulates in air. For exposure to metals, we made the conservative assumption that 100% of the estimated airborne concentration was deposited in a region of the lung, where it was entirely (100%) absorbed into the blood. Our estimated doses, and the corresponding health-based guidelines for metals, are presented in Table B-2 of Appendix B - Exposure Doses and Health-Based Guidelines (for Potential Exposure Pathways).

For exposure to HF and UO2F2 during an accidental (episodic) release of uranium hexafluoride (UF6) in 1966, we used CDC=s estimated airborne exposure concentration of HF, and doses to the kidney from UO2F2, for a hypothetical individual located 1.3 kilometers (km) downwind of the release. This release represents an acute (short-term) exposure as opposed to the chronic (long-term) exposures that we assumed for the other hypothetical exposure scenarios described above.

ATSDR scientists estimated off-site concentrations of SO2 and NOx from the coal-fired steam plant in the Fernald production area using the U.S. Environmental Protection Agency=s (EPA=s) SCREEN3 air dispersion model (EPA 2000). We selected inputs (e.g., wind speed, terrain, emission rates) to the model that produced the highest (worst-case) downwind concentrations at the nearest residence, located 2,500 feet (760 meters) north-northeast of the facility.

Emission rates were only available for one year, 1988, under past conditions at the site. These emission rates were equal to or lower than the highest emission rates reported for current conditions at the site: 410,000 kg of SO2 per year (yr) for 1991 and 160,000 kg/yr of NOx for 1994 (DOE 1972 - 1999). Using these current emission rates, and assuming worst-case conditions of air dispersion, the estimated maximum 1-hour SO2 concentration at the nearest residence, located 2,500 feet from the stack, was 227 micrograms per cubic meter (mg/m3). The estimated 1-hour NOx maximum at this residence was 89 mg/m3.

   
Health-Based Guidelines for Uranium and Other Chemicals
   
    
There are three types of health guidelines for exposure to uranium and other chemicals in air: (1) an airborne concentration, presented as micrograms of uranium or metal per cubic meter of air (µg/m3); (2) a body dose, presented as milligrams of uranium per kilogram of body weight per day (or mg/kg/day); and (2) a dose to the kidney, which is available only for uranium and is presented as micrograms of uranium per gram of kidney (µg/g).
   

We compared our estimated chemical exposure doses for inhalation of uranium, SO2, NOx, hydrogen fluoride, and metals to health-based guidelines to determine whether further evaluation of potential public health hazard was warranted. Additional information about the health-based guidelines for uranium is provided in the "Public Health Implications" section of this report. Additional information about the health-based guidelines for metals is provided in Appendix B - Exposure Doses and Health-Based Guidelines (for Potential Exposure Pathways).

Radiation

For radiation effects, the whole body, lungs, and bone surface are the major target organs for direct radiation and for inhaled uranium and most other airborne radioactive contaminants. We calculated committed effective doses (whole body) and committed dose equivalents (lung and bone surface) for airborne radioactive contaminants other than radon and radon decay products for both hypothetical exposure scenarios. (We used a different approach for radon and radon decay products.) For these radioactive contaminants, we calculated a lung dose and a bone surface dose for an adult male who could have received the highest potential dose. We also calculated a range of maximum external doses for the current years since the addition of the bentonite cap has changed (decreased) the potential for off-site exposure.

Past Exposure

Uranium releases to air were highest in the 1950s; however, uranium concentrations were not measured until 1960 (Voilleque et al. 1995). Computer modeling and known quantities of uranium emissions from stacks located in the production area were used to estimate concentrations of uranium in air prior to 1960 (Shleien et al. 1995; Killough et al. 1998a, 1998b). The highest estimated off-site uranium concentration is 1.5 mg/m3 for the area northeast of the facility in the 1950s (Killough et al. 1998b). This concentration represents overall site emissions from both direct and indirect releases of uranium to air. The estimate is based on the assumption that all uranium released from the site was present in a water-soluble form. ATSDR scientists used this estimated airborne uranium concentration to calculate exposure doses for a child and an adult farmer using the hypothetical exposure scenarios described above. ATSDR=s estimated exposure doses for uranium are presented in Table 8 (below).

As Table 8 shows, our estimated past airborne uranium concentration is lower than the health-based guideline (of 8 x 10-3 mg/m3) for intermediate-inhalation exposure to soluble uranium in air, but higher than the health-based guideline (of 3.3 x 10-4 mg/m3) for intermediate-chronic inhalation exposure to insoluble uranium in air. The guideline for insoluble uranium compounds is more relevant for evaluating health impact to Fernald residents, because the majority of releases from the site (and thus exposures) involved insoluble forms of uranium (Voilleque et al. 1995).

Our estimated past exposure doses (body doses) for a child and an adult farmer are both slightly lower than the health-based guideline (2 x 10-3 mg/kg/day) for ingested chemical uranium. Our estimated doses to the kidney for a child and adult farmer are almost 100 times lower than the proposed lower-bound threshold for kidney toxicity (1 x 10-1 mg/g) (Morris and Meinhold 1995).

Table 8. Current and past airborne concentrations and estimated exposure doses for exposure to uranium in air off site of the Fernald facility by a child (scenario #1) and an adult farmer (scenario #2)

 

Maximum Exposure Concentration
(mg/m3)

Estimated Body Dose*
(mg/kg/day)

Estimated Kidney Dose*
(mg/g)

Scenario #1: Child

 

 

 

Past exposure

1.5 x 10-3

6 x 10-4

2 x 10-3

Current exposure

6 x 10-7

2 x 10-7

7 x 10-7

Scenario #2: Adult Farmer

 

 

 

Past exposure

1.5 x 10-3

1 x 10-3

4 x 10-3

Current exposure

6 x 10-7

4 x 10-7

2 x 10-6

Key
mg/m3 = milligrams of uranium per cubic meter of air
mg/kg/day = milligrams of uranium per kilogram of body weight per day
mg/g = micrograms of uranium per gram of kidney

* Equations used to estimate doses for this pathway are described in Appendix BCExposure Doses and Health-Based Guidelines.

ATSDR scientists evaluated the public health hazard for this pathway together with other exposure pathways (i.e., groundwater, soil, surface water, and biota) that contribute to total uranium exposure to Fernald residents. This evaluation is presented in the "Public Health Implications" section of this report.

ATSDR also evaluated the public health hazard from exposure to hydrogen fluoride (HF) and uranyl fluoride (UO2F2) during an accidental release of uranium hexafluoride (UF6) in 1966. We used airborne exposure concentrations of HF, estimated by CDC contractors, for a hypothetical individual located 1.3 km downwind of the source (Voilleque et al. 1995). The estimated median HF concentration was 0.6 mg/m3, with a 95th percentile concentration of 1.5 mg/m3.

The Occupational Safety and Health Administration (OSHA) has set a permissible exposure level (PEL) of 3 ppm (or 2.5 mg/m3) for HF exposure to workers. The PEL represents a time-weighted average concentration for an 8-hour work day, 40-hour work week. The PEL is intended to protect workers from irritation effects of HF on the respiratory system, skin, and eyes. The National Institute for Occupational Safety and Health (NIOSH) has established an air concentration of 30 ppm (or 25 mg/m3) for HF that is considered immediately dangerous to life or health (IDLH). Air concentrations should not exceed the IDLH for a period of more than 30 minutes. CDC=s estimated air concentration of HF is below the OSHA PEL and NIOSH IDLH. Therefore, ATSDR did not evaluate the public health effects from exposure to HF due to accidental releases.

For UO2F2 released during an accident in 1996, contractors for the CDC estimated doses to the kidney for a hypothetical individual located 1.3 km and various other distances downwind from the source. For example, they predicted kidney doses for persons in New Baltimore, which is located about 3.5 kilometers from the site. They used dosimetry models, similar to those described above, to estimate the fraction of airborne UO2F2 deposited in the respiratory tract, absorbed into the blood, and transported to the kidney. They used a range of assumptions about wind dispersion (e.g., stability and speed) as inputs to the dosimetry models, because these factors affect particle deposition in the respiratory tract, and thus the kidney dose.

For an individual located 1.3 km downwind of the accident during the entire 1-hour period of release, under the most conservative ("worst-case") wind conditions, they estimated a median kidney dose of 0.86 micrograms (mg) of uranium per gram (g) of kidney, with 5th and 95th percentile estimates of 0.37 and 2.0 mg/g. The estimated kidney dose for an individual located 3.5 km downwind of the source is less than 0.2 mg/g. Under less conservative conditions of wind dispersion, the estimated kidney doses were 0.4 mg/g or less for an individual located 1.3 km downwind of the source, and less than 0.2 mg/g for an individual located 3.5 km downwind of the source.

Accidental or episodic releases of UO2F2 represent acute exposure conditions. This differs from the chronic (long-term) exposure conditions we assumed for the hypothetical exposure scenarios for a child and an adult farmer. Our estimated chronic doses actually represent higher exposures to the kidney, because these exposures accumulate over many years (Voilleque et al. 1995). The biological half-life of uranium in the kidney is 6 days; therefore, almost all of the uranium dose to the kidney following acute exposure would be cleared from the kidney in approximately 42 days (or 7 half-lives). In addition, the kidney concentration would decrease as the uranium was being cleared from the body.

For exposure to SO2 and NOx emissions from the coal-fired steam plant in the Fernald production area, we estimated maximum (worst-case) concentrations at the nearest off-site residence using computer air dispersion modeling. Our estimated exposure concentrations under past conditions are similar to, or lower than, exposure concentrations under current conditions. Because our estimated airborne concentrations of SO2 and NOx under current conditions do not exceed health-based guidelines (as discussed below), there is no indication that concentrations exceeded health-based concentrations under past conditions at the site.

The effects from past exposure to the radioactive uranium (and its decay products) in off-site air have been addressed in the Fernald Dosimetry Reconstruction Project and the Fernald Risk Assessment Project (Voilleque et al. 1995; Shleien et al. 1995; Killough 1998a, 1998b; CDC 1998, 1999). A brief description of these projects is presented in Appendix D of this report.

Current Exposure

Uranium emissions have been reduced drastically since the facility stopped operating in 1988 (Voilleque et al. 1995; DOE 1972 - 1999). Since 1988, the highest yearly average uranium concentration measured in off-site air is 0.000562 mg/m3 (or 6 x 10-7 mg/m3). This concentration was measured at the eastern facility boundary in 1993 and represents overall site emissions from both direct and indirect releases of uranium to air (DOE 1972 - 1999). This airborne chemical uranium concentration is lower than the health-based guideline (of 8 x 10-3 mg/m3) for intermediate-inhalation exposure to insoluble uranium in air, and lower than the health-based guideline (of 3.3 x 10-4 mg/m3) for intermediate-chronic inhalation exposure to soluble uranium in air. We used this maximum yearly concentration to estimate exposure doses for chemical uranium, and committed effective doses (whole body) and committed equivalent doses (lungs and bone surface) for radioactive uranium, for both hypothetical exposure scenarios. ATSDR=s estimated chemical exposure doses are presented in Table 8 (above).

For chemical uranium, our estimated current exposure doses (body doses) for a child and an adult farmer are more than 1,000 times lower than ATSDR=s health-based guideline for ingested uranium. Likewise, our estimated doses to the kidney for both scenarios (a child and adult farmer) are more than 100,000 times lower than the proposed lower-bound threshold for kidney toxicity (Morris and Meinhold 1995). Despite the fact that our estimated chemical exposure doses are lower than the health-based guidelines, ATSDR scientists evaluated the public health hazard for this pathway together with other exposure pathways (i.e., groundwater, soil, surface water, and biota) that contribute to total uranium exposure to Fernald residents. That evaluation is presented in the "Public Health Implications" section of this report.

ATSDR scientists used maximum concentrations of metals in off-site surface soil, and maximum concentrations of total suspended particulates in off-site air, to estimate concentrations of metals (present as re-suspended soils) in off-site air.

Total suspended particulates were routinely measured at sampling stations located within 4 miles of the Fernald production center. Yearly average particulate concentrations ranged from 30.0 to 39.6 mg/m3 (DOE 1972 - 1999). The highest particulate concentration (39.6 mg/m3) was used to calculate airborne concentrations of metals using the equation described previously in this section. Our estimated exposure doses for metals, along with a discussion of the health-based guidelines for these metals, are presented in Table B-2 of Appendix B - Exposure Doses and Health-Based Guidelines (for Potential Exposure Pathways). Neither our estimated airborne concentrations nor our estimated exposure doses exceed health-based guidelines for metals, despite the conservative assumptions used to estimate concentrations and doses. Further evaluation of exposure to metals for the air pathways is not included in the "Public Health Implications" section of this report.

Our maximum (worst-case) estimated 1-hour airborne concentrations of SO2 and NOx at the nearest off-site residence, located 2,500 feet north-northeast of the facility, are 227 micrograms per cubic meter (mg/m3) for SO2 and 89 mg/m3 for NOx. Concentrations decrease at increasing distance from this residence.

For SO2, our estimated off-site concentration is much lower than both the 3-hour and 24-hour National Ambient Air Quality Standard (NAAQS) established by the U.S. Environmental Protection Agency. The 3-hour average concentration (1300 mg/m3) is a secondary standard intended to protect public welfare; it takes into account decreased visibility, damage to animals, crops, vegetation, and buildings. The 24-hour standard (365 mg/m3) is a primary standard intended to protect public health, including the health of sensitive populations such as asthmatics, children, and the elderly. For NOx, our estimated off-site concentration is lower than the annual arithmetic mean standard of 100 mg/m3 established by the EPA. This standard is both a primary and secondary air standard. Because our estimated airborne concentrations, under worst-case conditions of air dispersion from the steam plant, are lower than regulatory standards intended to protect public health, we did not evaluate exposure to SO2 and NOx further.

For doses from radioactive contaminants other than radon and radon decay products, our estimated committed effective (whole-body) and committed equivalent (lung and bone surface) doses for radioactive contaminants in air pathways are presented in Table 9 (below). Further evaluation of human exposure to radioactive contaminants in off-site air, including a determination of whether these estimated doses present an increased likelihood of developing fatal cancers and lung or bone cancer, is discussed in the "Public Health Implications" section of the report.

Table 9. Estimated committed effective (whole body) and committed equivalent (lung and bone surface) doses for current exposure to radioactive contaminants in air off site of the Fernald facility by a child (scenario #1) and an adult farmer (scenario #2)

 

Max. Annual Average Conc. in pCi/m3 (Bq/m3)*

Committed Effective Dose (whole body) in mrem (mSv)

Committed Equivalent Doses (lungs and bone surface)

in mrem (mSv)

Child

Adult

Child

Adult

 

 

Lung

Bone Surface

Lung

Bone Surface

Total Uranium

3.8E-04 (1.4E-05)

2.5E-02 (2.5E-04)

2.1 (2.1E-02)

2.1 (2.1E-02)

0.22 (2.2E-03)

17.7 (0.177)

2.27 (2.3E-02)

Strontium 90

9.5E-06 (3.5E-07)

1.0E-04 (1.0E-06)

1.0E-03 (1.0E-05)

8.2E-04 (8.2E-06)

1.7E-04 (1.7E-06)

8.2E-03 (8.2E-05)

2.3E-03 (2.3E-05)

Technetium 99

1.4E-04 (5.2E-06)

1.3E-04 (1.3E-06)

1.2E-03 (1.2E-05)

1.1E-03 (1.1E-05)

4.8E-07 (4.8E-09)

1.0E-02 (1.0E-04)

2.3E-06 (2.3E-08)

Cesium 137

3.5E-05 (1.3E-06)

9.7E-05 (9.7E-07)

9.2E-04 (9.2E-06)

7.2E-04 (7.2E-06)

4.3E-06 (4.3E-08)

7.0E-03 (7.0E-05)

1.1E-04 (1.1E-06)

Radium 226

2.7E-06 (1.0E-07)

2.0E-03 (2.0E-05)

1.7E-02 (1.7E-04)

1.3E-02 (1.3E-04)

2.2E-03 (2.2E-05)

0.14 (1.4E-03)

2.9E-02 (2.9E-04)

Radium 228

1.4E-04 (5.2E-06)

0.18 (1.8E-03)

1.5 (1.5E-02)

1.5 (1.5E-02)

0.56 (5.6E-03)

12.4 (0.124)

2.77 (2.8E-02)

Thorium 228

1.3E-05 (4.8E-07)

4.2E-02 (4.2E-04)

0.34 (3.4E-03)

0.34 (3.4E-03)

1.36 (1.4E-02)

2.8 (2.8E-02)

10.3 (0.103)

Thorium 230

4.8E-05 (1.8E-06)

0.26 (2.6E-03)

3.2 (3.2E-02)

0.28 (2.8E-03)

10.7 (0.107)

2.5 (2.5E-02)

189.1(1.89)

Thorium 232

8.7E-06 (3.2E-07)

5.5E-02 (5.5E-04)

0.64 (6.4E-03)

8.5E-02 (8.5E-04)

2.08 (2.1E-02)

0.93(9.3E-03)

33.1 (0.33)

Neptunium 237

3.8E-06 (1.4E-07)

8.9E-03 (8.9E-05)

0.13 (1.3E-03)

2.4E-02 (2.4E-04)

0.28 (2.8E-03)

0.2 (2.0E-03)

6.56 (6.6E-02)

Plutonium 238

3.8E-07 (1.4E-08)

2.1E-03 (2.1E-05)

2.8E-02 (2.8E-04)

2.7E-03 (2.7E-05)

4.5E-02 (4.5E-04)

2.4E-02 (2.4E-04)

0.91 (9.1E-03)

Plutonium 239

7.6E-07 (2.8E-08)

4.4E-03 (4.4E-05)

6.0E-02 (6.0E-04)

5.0E-03 (5.0E-05)

0.10 (1.0E-03)

4.4E-02 (4.4E-04)

2.01 (2.0E-02)

TOTALS

 

0.58 (5.8E-03)

8.0 (8.0E-02)

4.3 (4.3E-02)

15.4 (0.154)

36.7 (0367)

246.9 (2.47)

Key
Max = maximum
Conc. = concentration
pCi/m3 = picocuries per cubic meter
Bq/m3 = becquerels per cubic meter
mrem = millirems
mSv = millisieverts
* Concentrations of radioactive contaminants are based on percentage of each isotope reported in the 1993 annual composite analyses and annual average uranium concentration from weekly collection of samples (DOE 1972B1999).

† Most conservative chemical form (most conservative conversion factors) used for calculation (ICRP 1995b).

For current dose estimates from radon and radon decay products from the K-65 silos (Silos 1 and 2) and from direct radiation from Silos 1, 2, and 3, ATSDR scientists reviewed DOE alpha-track monitoring and external exposure data from 1989 to 1999. FEMP discontinued the use of alpha-track detectors at the end of 1998 and now relies on alpha scintillation continuous monitors for detecting radon (DOE 1972 - 1999). The results from all alpha-track monitors at the fenceline and those closest to the K-65 silos are summarized in Table 10 below. The results are averaged over a year although the concentrations can vary significantly with the seasons of the year and time of day (Merrill 1998). In 1991, DOE added real-time monitors (continuous alpha scintillation detectors) at and near Silos 1 and 2. Silo 3 contains thorium waste but not high concentrations of radium waste like Silos 1 and 2; however, the waste in Silo 3 contributes to direct radiation levels.

Table 10. Summary of DOE=s alpha-track monitoring results at fenceline and at potentially affected residences (with background subtracted and reported in pCi/L and Bq/L)

Year

Average of 21 Property Fenceline Locations

Average of 6 Boundary Stations Closest to silos*

Max. Concentration at Residences on West Side of SiteH

Concentration Near Residence Northeast of SiteI

1989

0.24 ± 0.15
(0.009 ± 0.006)

0.28 ± 0.10
(0.010 ± 0.004)

0.4 (0.015)

0.2 (0.007)

1990

0.23 ± 0.28
(0.009 ± 0.010)

0.28 ± 0.07
(0.010 ± 0.003)

0.2 (0.007)

0.1 (0.004)

1991

0.31 ± 0.30
(0.011 ± 0.011)

0.34 ± 0.11
(0.013 ± 0.004)

1.0 (0.042)

0.1 (0.004)

1992

Less than background

0.17 ± 0.10
(0.006 ± 0.004)

0.4 (0.015)

Equal to background

1993

Less than background

Less than background

Less than background

Less than background

1994

Less than background

Less than background

Less than background

Less than background

1995

0.17 ± 0.10
(0.006 ± 0.004)

0.10 ± 0.10
(0.004 ± 0.004)

0.2 (0.007)

0.2 (0.007)

1996

0.20 ± 0.10
(0.007 ± 0.004)

Not reported

0.2 (0.007)

0.2 (0.007)

1997

0.40 ± 0.10
(0.015 ± 0.004)

0.30 ± 0.10
(0.011 ± 0.004)

0.2 (0.007)

Equal to background

1998

0.30 ± 0.20
(0.011 ± 0.007)

0.30 ± 0.10
(0.011 ± 0.004)

0.2 (0.007)

0.1 (0.004)

Key
pCi/l = picocuries per liter
Bq/l = becquerels per liter

* These locations were picked because of their close proximity to the silos; however, the prevailing wind direction is to the northeast or southeast from the silos.
H Ohio EPA=s Office of Federal Facilities Oversight have been using continuous radon monitors at three locations west of the site since 1996.
I This location was picked because a dose from other airborne radionuclides was calculated near this area.

Source: DOE 1972B1999

In 1992, ATSDR entered into an interagency agreement with EPA=s National Air and Radiation Environmental Laboratory (NAREL) to monitor environmental radon near residences neighboring the Fernald site. ATSDR prepared a Health Consultation, addressing emissions of radon and radon daughters from the K-65 silos, in May 1995 (ATSDR 1995b). The Health Consultation presented the results of the ATSDR/NAREL sampling from December 1993 through June 1994. In the consultation, ATSDR concluded that radon released during this period did not pose a public health hazard. However, we also highlighted some issues related to DOE=s monitoring program. For example, DOE=s continuous monitors were unreliable when they were used outside their operational temperature range, they did not obtain duplicate hourly radon measurements, and backup continuous monitors were not maintained to replace inoperable detectors. During this period, NAREL=s E-PERM monitors experienced some erroneously high readings, which were not confirmed by duplicate monitors in the same location.

Since 1994, additional sampling data have been collected by NAREL. In 1995, an ATSDR/NAREL decision was made to employ three alpha track detectors at each location along with the E-PERMS. As expected, the alpha track detectors were determined to be more reliable, and radon measurements are now determined using three alpha track detectors at each location.

ATSDR scientists compared monitoring data collected by NAREL and DOE from 1995 and 1996. We concluded that NAREL=s alpha-track detector data from 1995 was slightly biased toward higher readings, and DOE=s alpha-track detector data from 1996 was slightly biased toward higher readings; however, for the 2 years combined, there does not appear to be a difference in long-term concentrations measured by NAREL or DOE. ATSDR scientists provide a more thorough discussion of the ATSDR/NAREL and DOE radon monitoring programs, and a comparison of the sampling and analysis data, in Appendix F.

Since NAREL=s data did not cover the entire current time period (beginning in 1989), we used DOE=s data to calculate potential maximum exposures. Table 11 (below) presents the maximum current annual lung dose, calculated from the concentrations shown in Table 10, for the fenceline near the silos, a residence west of the site, and a residence northeast of the site. These concentrations can occur in different years, due to differences in wind direction and activity occurring on the site. Further evaluation of human exposure to radon and radon decay products in off-site air, including a determination of whether these estimated doses present an increased likelihood of developing lung cancer, is discussed in the "Public Health Implications" section of this report.

Table 11. Estimated average annual lung dose for an adult male exposed continuously to maximum concentrations (with background subtracted)

Location

Year

Estimated Average Annual Lung Dose in mrad/yr (mGy/yr)

Average of six boundary stations closest to silos

1991

102 ± 33 (1.02 ± 0.33)

Maximum annual concentration at residence west of silos

1991,
after 1991

300 (3.00),
60 (0.60)

Maximum annual concentration near residence northeast of site

1999

90 (0.90)

Key
mrad/yr = millirads per year
mGy/yr = milligrays per year
Source: NCRP 1984

 

In 1991, when bentonite (clay) caps were added inside the K-65 silo domes, direct radiation levels and radon releases from the silos decreased. The average annual lung dose after the cap was added is estimated at 60 millirad per year (0.60 milligray per year) for someone continuously present at a residence west of the silos. Recently there are indications that the direct radiation levels at the exclusion fence near the silos have increased; however, the radiation levels are lower than they were before the bentonite cap was added and do not add substantially to the total dose off site (DOE 1972 - 1999). (Refer to Table 12, below.) The radiation levels were determined using quarterly thermoluminescent detector (TLD) readings averaged over the year.

Table 12. Annual average external exposure doses at fenceline air monitoring stations west of the silos and northeast of the site (with background subtracted)

Year

Annual Average Dose at AMS-6 West of Silos in mrem/yr (mSv/yr)

Annual Average Dose at AMS-2 Northeast of Site in mrem/yr (mSv/yr)

1989

59 (0.59)

13 (0.13)

1990

59 (0.59)

11 (0.11)

1991

48 (0.48)

12 (0.12)

1992

7 (0.07)

12 (0.12)

1993

8 (0.08)

12 (0.12)

1994

8 (0.08)

11 (0.11)

1995

8 (0.08)

8 (0.08)

1996

11 (0.11)

7 (0.07)

1997

14 (0.14)

8 (0.08)

1998

17 (0.17)

7 (0.07)

Key
mrem/yr = millirems per year
mSv/yr = millisieverts per year

 

The silo domes were resealed in 1999 as an interim control measure. In the future, radon emissions will be mitigated when the waste is treated, removed from the silos, and sent off site for disposal (DOE 1972 - 1999). By January 2000, contracts had been awarded for remediation of Silo 3 and for Accelerated Waste Retrieval for Silos 1 and 2 (DOE 2000).

Potential Future Exposure

Chemicals and radioactive materials may be released from waste storage and processing areas (e.g., silos, waste pits) during future remediation activities at the Fernald site. The community is particularly concerned about future activities involving removal of radioactive waste material contained in the K-65 silos and transport of this material to a secured disposal area. ATSDR scientists used computer models to predict concentrations of radon and radon daughters that would be released from the K-65 silos if a catastrophic event (e.g., a terrorist attack) or natural disaster occurred and radioactive contaminants were released to the atmosphere. The results of these predictions, and a discussion of the models used, will be presented in a Health Consultation currently being prepared by ATSDR.

If additional information becomes available indicating that concentrations of chemicals or radioactive contaminants have increased, the air exposure pathways should be re-evaluated.

Next Section     Table of Contents

 
 
USA.gov: The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

A-Z Index

  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #