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

EXPOSURE PATHWAYS ANALYSIS

Introduction

A release of a chemical or radionuclide into the environment does not always result in human exposure. People can be exposed by eating, breathing, or contacting these substances when they are present in environmental media such as air, drinking water, or soil. Unlike chemicals, the presence of radionuclides at high enough concentrations in the environment can result in external (or direct) radiation exposures to persons who are close to the material.

Exposure Pathways

   

Contaminants Evaluated

   
    

Contaminants evaluated are those chemicals found in off-site environmental media at levels that exceed media-specific comparison values, and all radioactive contaminants found in off-site environmental media. Not all contaminants from the site are at levels that may pose a health hazard. The potential for exposure to contaminants in each pathway of exposure is evaluated in this section. The introduction to Appendix A provides additional information about the contaminants evaluated for each pathway and how they were selected.

   

The following section discusses the various chemicals and radioactive materials (contaminants) evaluated for the Fernald site,how people may come into contact with them, and the potential health effects that may result. Detailed information about the process ATSDR scientists use to select the contaminants evaluated in this public health assessment is provided in Appendix A - Selection of Contaminants.

For exposure to occur, an exposure pathway must exist. Exposure pathways are characterized as complete or potential. The five elements of a completed exposure pathway are (1) a source of chemical or radioactive contamination, (2) an environmental medium or media (e.g., groundwater, surface water, air) through which contaminants are transported from on-site to off-site locations, (3) a point of exposure or place where human exposure is likely to occur, (4) a route of human exposure (e.g., eating, breathing), and (5) an exposed population. A potential exposure pathway exists when one of the elements is missing, but available information indicates that human exposure is likely to occur via that pathway. Figure 4 illustrates the necessary components of an exposure pathway.

For example, chemicals or radionuclides may be released from a facility onto the ground (soil) during routine operations or an accident (the contaminant source). These substances may then dissolve in rainwater that percolates down through the soil to the underlying groundwater (the environmental media). If the contaminated groundwater is being used as a drinking water source (the point of exposure and exposed population), then people may be drinking and bathing (the routes of exposure) in water that contains these contaminants. All elements of the pathway must be present before the pathway is complete.

Figure 4. Pathways of exposure to contaminants from the Fernald site

The completed exposure pathways for the Fernald site are described in Table 2A; the potential exposure pathways are described in Table 2B. In this section, ATSDR scientists determine the potential for exposure to each contaminant in completed and potential exposure pathways identified for the site.

The focus of the ATSDR public health assessment is on current and past exposure to chemicals and on current exposure to radioactive materials from the site. For

   

Current and Past Exposure

   
    

Environmental data collected while the facility was in operation were used to estimate past exposure to Fernald residents. Environmental data collected after the facility stopped operating were used to estimate current exposure to Fernald residents.

   

the purposes of this health assessment, "current exposure" refers to the period from 1989, when the facility had stopped operating, to the present. "Past exposure" refers to the period from 1951 to 1988, while the facility was operating. When applicable, ATSDR scientists also evaluated potential future exposure to chemical and radioactive materials released from the site to the environment.

The "Exposure Pathways Analyses" section describes the first tier of a multi-tiered approach to evaluate public health hazard in the public health assessment. This first tier of analysis, the exposure pathways analysis, is essentially a screening step to rapidly identify which pathways and contaminants are unlikely to cause adverse health effects and require no further evaluation. Using conservative assumptions about exposure, ATSDR scientists estimate exposure doses for chemicals and radioactive materials in completed or potential exposure pathways.

For chemicals, the estimated exposure doses are compared to a variety of health-based guidelines. The health-based guidelines are used to identify whether contaminant exposure merits further evaluation, and not to quantify health risk. Methods and assumptions used by ATSDR scientists to calculate exposure doses are discussed in Appendix B - Exposure Doses and Health-Based Guidelines. When the estimated chemical exposure dose exceeds an appropriate health guideline, a second tier of analysis involving a more in-depth, weight-of-evidence approach is used to evaluate health hazard (Weis and Susten 1999). The weight-of-evidence evaluation is discussed in the following section of this report, "Public Health Implications." The weight-of-evidence approach involves a thorough evaluation of the quality and relevance of scientific information which is the basis of health guidelines considering various factors. The weight-of-evidence evaluation also considers whether human exposure will occur under hypothetical but realistic conditions of exposure.

For radioactive contaminants, ATSDR scientists evaluate all exposure pathways for the site that contribute to radiological doses (committed effective doses and equivalent doses to the target organ). In the following section of this report, "Public Health Implications," we added the doses that an individual could receive from all pathways and determined whether these combined doses indicate an increased likelihood of an individual developing cancer.

Special Consideration of Women and Children

Women and children may sometimes be affected differently than the general population by contaminants in the environment. Both are smaller than the population average and are affected by smaller quantities of the contaminants. The effect of hormonal variations, pregnancy, and lactation can change the way a woman's body responds to some substances. Exposure during pregnancy and lactation can expose the fetus or infant if contaminants cross the placenta or get into the mother's milk. Depending upon the stage of pregnancy, exposure of the fetus could result in death (miscarriage or stillbirth) or birth defects. If the mother is exposed during lactation, her milk may concentrate certain contaminants, increasing the exposure to her infant.

ATSDR's Child Health Initiative recognizes that developing young person, whether fetus, infant, or child, has unique vulnerabilities. For example, some exposures would affect children more than adults because of their lower body weight and higher ingestion rate, resulting in an increased dose or amount taken into the body compared to their body weight. Because children are shorter, their breathing zones are closer to the ground, and thus closer to soil contaminants and low-lying layers in the air. Different behavioral characteristics include more hand-to-mouth behavior, increasing the ingestion of soil or dust contaminants.

Furthermore, children's metabolic pathways are less developed than those of adults, especially in the first months after birth. In some instances children are better able to deal with environmental toxins, but in others, they are more vulnerable. Some chemicals that are not toxic to adults are highly toxic to infants.

Children grow and develop rapidly in their first months and years of life. Some organ systems, especially the nervous and respiratory systems, may experience permanent damage if exposed to high concentrations of certain contaminants during this period. Because of rapid growth and development, a child's genetic material (deoxyribnucleic acid, or DNA) is more likely to be exposed than later in life, making it more vulnerable to damage.

Children have more future years than adults, giving more time for the development of illnesses that require many years to progress from the earliest initiation to the manifestation of the disease.

Finally, young children have less ability to avoid hazards because of their lack of knowledge and their dependence on adults for decisions that may affect children but not adults.

In the "Exposure Pathways Analyses" section, we will indicate whether women and children were, are, or may be exposed to chemical and radioactive contaminants of concern in the completed and potential exposure pathways for the site. In the following section, "Public Health Implications," we discuss the public health hazard from exposures via these pathways.

Table 2A. Completed exposure pathways for the Fernald site

Radioactive Substances

Source

Environmental Media

Point of Exposure

Route of Exposure

Exposed Population

Exposure Time Frame

1. Uranium
2. Radon and radon daughters
3. Direct radiation from radioactive materials in Silos 1, 2 and 3

Process operations and waste management practices; radioactive materials stored in K-65 silos

Airborne transport

Off-site residential areas

Inhalation and external exposure (gamma radiation)

Children, teenagers, adults

Past

Radon and radon daughters

Process operations and waste management practices

Airborne transport

Off-site residential areas

Submersion (engulfed in air containing radon and radon daughters)

Children, teenagers, adults

Past

Uranium

Process operations and waste management practices

Leaching of contamination from on-site soil and surface water to groundwater

Off-site privately owned wells

Ingestion of groundwater used for potable purposes

Children, teenagers, adults

Past

Uranium

Process operations and waste management practices

Leaching of contamination from on-site soil and surface water to groundwater

Off-site privately owned wells

Absorption: Groundwater used for non-potable purposes

Children, teenagers, adults

Past

Table 2B. Potential exposure pathways for the Fernald site

 Radioactive Substances

Source

Environmental Media

Point of Exposure

Route of Exposure

Exposed Population

Exposure Time Frame

1. Uranium
2. Radon and radon daughters
3. Other radioactive materials

Remedial activities, waste management practices, radioactive material stored in silos

Airborne transport

Off-site residential areas

Inhalation and external exposure (gamma radiation)

Children, teenagers, adults

Current, potential future

Radon and radon daughters

Remedial activities and waste management practices

Airborne transport

Off-site residential areas

Submersion (engulfed in air containing radon and radon daughters)

Children, teenagers, adults

Current, potential future

Uranium, metals, nitric oxides (NOx), sulphur dioxide
(SO2), other radionuclides

Process operations, remedial activities, and waste management practices

Airborne transport, deposition

Off-site residential areas

Incidental ingestion of material on surface soils; inhalation of re-suspended materials

Children,

teenagers, adults

Past, current

Uranium, other

radionuclides

Process operations, remedial activities, and waste management practices

Airborne transport, deposition, uptake

Off-site commercial and private farms

Ingestion of biota (plants, animals, and animal products)

Children,

teenagers,

adults

Past, Current

Uranium, other radionuclides

Process operations, remedial activities, and waste management practices

Surface runoff to Paddy=s Run Creek

Off-site residential and public access areas

Ingestion of water in Paddy=s Run Creek; external exposure in Paddy=s Run Creek

Children, teenagers, adults

Past, current, potential future

Uranium, other radionuclides

Process operations, remedial activities, and waste management practices

Discharge to Great Miami River

Off-site residential and public access areas

Ingestion of water in Great Miami River; ingestion of fish caught in Great Miami River

Children, teenagers, adults

Past, current, potential future

Uranium

Remedial activities and waste management practices

Leaching from on-site soil to groundwater

Off-site privately owned wells

Ingestion of groundwater used for potable purposes

Children, teenagers, adults

Current, potential future

Uranium

Remedial activities and waste management practices

Leaching of contamination from on-site soil to groundwater

Off-site privately owned wells

Absorption: Groundwater used for non-potable purposes

Children, teenagers, adults

Current, potential future


COMPLETED EXPOSURE PATHWAYS

Groundwater Pathway (Privately Owned Wells)

Background

The Great Miami Aquifer is the source of groundwater for the Fernald area. Many residences in the immediate vicinity of the Fernald site have relied on privately owned wells supplied by the Great Miami Aquifer as their primary source of drinking water. Some of these wells are still in use today, although ATSDR does not know how many households near the site are currently using privately owned wells for drinking water, or where those households are relative to the site. Several residences also have used and currently use cisterns as a source of drinking water (ODH 1988).

In 1981, DOE first detected uranium at concentrations above background levels in privately owned drinking water wells south of the facility. Because of these elevated uranium concentrations, DOE began routine monitoring of private wells near the Fernald site in 1982. In 1984, the groundwater monitoring program was formally established. By 1996, the program had expanded to include more than 30 private wells. Wells were sampled monthly or quarterly, depending on the location (DOE 1972 - 1999). The private well locations are shown in Figure 5.

The area south of the Fernald site has historically had the highest concentrations of uranium. It is also where most private wells are located. DOE contractors at the site have been cleaning up (remediating) the groundwater contaminant plume since 1986. For purposes of remediation, the uranium plume (where uranium concentrations are greater than or equal to 20 micrograms per liter) was named the "South Plume." There are additional areas of groundwater contamination on the Fernald site, but only the South Plume extends outside the site boundary. According to monitoring well data and groundwater modeling, the South Plume is an elongated ellipse oriented in the northwest-southeast direction (Voilleque et al. 1995; DOE 1972 - 1999).

The primary sources of groundwater contamination in the South Plume are historical releases of uranium-contaminated water to the storm sewer outfall ditch (SSOD) and Paddy's Run Creek (Voilleque et al. 1995). The SSOD became contaminated by overflow of the site's storm sewer system when heavy rains exceeded the storm sewer lift station capacity. Overflow of contaminated water from the SSOD discharges into Paddy's Run Creek. The Stormwater Retention Basin, which began operations in 1986, greatly reduced discharges of contaminated stormwater to the SSOD and Paddy's Run Creek (DOE 1972 - 1999). Paddy's Run Creek also receives contaminated stormwater runoff from the western portion of the site (Voilleque et al. 1995). Contaminated surface water from the SSOD and Paddy's Run Creek seeped into the underlying groundwater. Releases from solid and liquid waste pits in the waste storage area contributed a small amount to groundwater contamination at the site (Voilleque et al. 1995).


Figure 5. Location of privately owned sampled wells near the Fernald site.

Environmental Data

ATSDR scientists used sampling data collected from 1981 to the present to evaluate potential human exposure to contaminants in privately owned drinking water wells near the Fernald site. Most data were measured concentrations of total uranium. A smaller portion of the data, collected during various time periods, were measured concentrations of metals, elements, and nitrates. A summary of the sampling data used to evaluate groundwater pathways for privately owned wells is provided in Table A-1 of Appendix A - Selection of Contaminants (for Completed Exposure Pathways).

Of the privately owned wells that were routinely monitored by the facility, only four wells (numbers 12, 13, 15, and 17) ever showed uranium concentrations above the proposed drinking water standard of 20 micrograms per liter (mg/L) (Voilleque et al. 1995; DOE 1972 - 1999). These four wells are close to each other and are directly within the South Plume. Well 15 has historically had the highest uranium concentrations; however, it is uncertain if this well was ever used as a drinking water source. None of these wells was used as a drinking water source after 1986. Well 13's water has contained uranium concentrations above 20 mg/L since 1992, although this well has not been used as a drinking water source since 1991. Maximum uranium concentrations measured in these wells are presented in Table 3 (below). Annual maximum uranium concentrations in water from these wells are presented in Table A-2 of Appendix A - Selection of Contaminants (for Completed Exposure Pathways).

Table 3. Maximum measured uranium concentrations in water from private wells (numbers 12, 13, 15, and 17) off site of the Fernald facility

Private Well

Maximum Concentration
(mg/L or ppb)

Year Maximum Concentration Detected

Water Potentially Used As a Drinking Water Source When Maximum Concentration Was Detected?

12

410

1987

No

13

120

1996

No

15

578

1983

Potentially

17

170

1987

No

Key
mg/L = micrograms of uranium per liter of water
ppb = parts per billion

Source: DOE 1972 - 1999; Voilleque et al. 1995

Groundwater modeling indicates that private wells south of the site may have been first impacted by the South Plume some time after 1962 (Voilleque et al. 1995). No private well sampling was conducted before 1981. Therefore, contractors for CDC estimated uranium concentrations using measurements (sampling) of water from the SSOD and Paddy's Run Creek, and known quantities of uranium releases to the SSOD (Voilleque et al. 1995). Maximum uranium concentrations were found in surface water samples from the SSOD and Paddy's Run Creek during the 1960s (Voilleque et al. 1995).

The CDC contractors estimated yearly median and upper-bound (95th percentile) uranium concentrations in the South Plume, and in private wells 12, 15, and 17, for the period from 1963 to 1988 (Voilleque et al. 1995). The highest estimated median uranium concentration was 918 mg/L in 1977 and 1978. The highest estimated upper-bound uranium concentration was 4,144 mg/L in 1963 (Voilleque et al. 1995). The contractors assumed that all uranium present in the South Plume was normal uranium (with isotopic ratios the same as or similar to natural uranium), rather than enriched or depleted uranium. This was a valid assumption, because many of the facility's operations involved uranium recovery and recycling (Voilleque 1999).

A public water supply to the area around the Fernald site did not exist when the routine groundwater monitoring program was initiated. If a nearby private well was found to be contaminated by uranium at concentrations above background concentrations, then the private well user was offered bottled water for household use (DOE 1972 - 1999). In 1996, public water was supplied to these area residents. As a result, DOE reduced its private well sampling program to three wells (wells 12, 13, and 14), which are located immediately downgradient of groundwater flow from the Fernald property boundary and within the South Plume (DOE 1972 - 1999).

Residences near the Fernald facility also used cisterns as a source of drinking water (ODH 1988; Pinney 2000). Investigations conducted by the Ohio Department of Health, from 1985 to 1988, identified and sampled water from 54 cisterns used as drinking water sources near the Fernald site (ODH 1988). Of these cisterns, only one located immediately north of the site was found to contain water contaminated with uranium at concentrations above background (0.4 to 3 mg/L). The concentration in this cistern was 43.3 mg/L, which was lower than uranium concentrations detected in the off-site private wells in the South Plume. The source of water for this cistern was rainwater collected via roof gutters. The cistern had been disconnected 2 years before this sampling and had not been used for drinking water since then. Therefore, the water in the cistern had not been disturbed for 2 years prior to sampling (ODH 1988).

Contractors for the Fernald facility are currently implementing the Great Miami aquifer groundwater restoration remedy as part of site remediation activities (DOE 1972 - 1999). The remedy consists of a series of groundwater extraction and re-injection modules, and a centralized water treatment facility. The extraction system is designed to prevent further southward movement of the uranium plume originating at the Fernald site. Six groundwater extraction wells make up the South Plume module. Four of these extraction wells have been in operation since 1993. As part of the South Plume module, groundwater in the South Plume is being monitored for total uranium, metals, elements, and volatile organic compounds. Groundwater south of the South Plume boundary is also being monitored for chemical contaminants, including arsenic, phosphorus, potassium, sodium, and volatile organic compounds, originating in a plume at the Paddy's Run Road site located south of the Fernald facility (DOE 1972 - 1999). Sampling results for 1996 and 1997 indicate that other than uranium in the South Plume, there are no concentrations of contaminants in groundwater that necessitate accelerated remediation ahead of the proposed schedule for the South Plume (DOE 1972 - 1999).

Estimated Exposure Doses

ATSDR scientists evaluated past, current, and potential future exposure to chemical contaminants in groundwater off site of the Fernald facility. Uranium was the only chemical evaluated for this pathway. Other chemicals (metals) were detected infrequently and at low levels in private wells off site of the Fernald facility. The data used to evaluate chemical contaminants in groundwater pathways are provided in Table A-3 of Appendix A - Selection of Contaminants.

ATSDR scientists also evaluated current and potential future exposure to radioactive contaminants (uranium) in groundwater 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 is in Appendix D of this report.

ATSDR assumed ingestion as the primary route of exposure to chemicals in well water. Uranium dissolved in water is not likely to volatilize into air; therefore, inhalation was not considered a possible route of exposure. Skin contact with uranium during household use of water may have occurred but is likely to contribute minimally to uranium exposure dose (ATSDR 1999b; CDC 1998).

In July 1996, ATSDR conducted a Health Consultation to evaluate exposure to uranium and other radioactive materials in water used by Fernald residents for non-potable purposes (ATSDR 1996a). The consultation used 1994 groundwater sampling data and reflects current conditions of exposure at the site.

   

Estimating Exposure Dose

   
    

ATSDR scientists evaluated two hypothetical exposure scenarios for exposure to uranium via groundwater: (1) a child who ingests maximum concentrations of uranium in private wells on a daily basis, and (2) an adult who ingests maximum concentrations of uranium in private wells on a daily basis

   

ATSDR evaluated two hypothetical exposure scenarios for this pathway. The first scenario assumes exposure to a young child, 1 to 6 years old, who weighs 13 kilograms (kg) and ingests 1 liter (L) of contaminated water a day from the tap at well 15, the most highly contaminated private well (ATSDR 1993; EPA 1999).

The second hypothetical exposure scenario assumes exposure to an adult who weighs 70 kg and ingests 2 L of contaminated water a day from the tap at private well 15 (ATSDR 1993; EPA 1999).

Chemicals

ATSDR scientists calculated two types of exposure doses for exposure to uranium in groundwater for the two hypothetical exposure scenarios (described above). These are a body dose and a dose to the kidney. The kidney is the target organ for ingested uranium.

The chemical effects of uranium result only after the uranium is absorbed into the bloodstream from the gastrointestinal tract (following ingestion) and transported (distributed) to the kidney. In estimating dose to the kidney, ATSDR scientists assumed that 5% of the uranium in ingested water is absorbed into the blood. This is a conservative assumption, because data from human ingestion studies and pharmacokinetic models indicate that maximum absorption of uranium from the gastrointestinal tract (e.g., stomach, small intestine) ranges from 2% to 4% for the soluble forms of uranium (ATSDR 1999b; ICRP 1995a).

Gastrointestinal absorption of uranium does not appear to vary substantially by age. Recent information suggests that children 5 years old and older absorb uranium from the gastrointestinal tract at the same rate as adults (ICRP 1995a; ATSDR 1999b). Gastrointestinal absorption rates are not known for children less than 5 years old. Because there is no indication that absorption rates in small children (i.e., children under 5) are higher than in adults, ATSDR scientists assumed that the absorption rate for a child is equal to the maximum absorption rate for an adult (or 5%).

ATSDR scientists also made assumptions about how much of the uranium absorbed into the blood is distributed to the kidney. Biokinetic models of uranium distribution in adults indicate that a maximum of 12% of the absorbed dose of soluble uranium is distributed to the kidneys (ICRP 1979, 1995a; Zhao and Zhao 1990). Therefore, ATSDR scientists assumed that 12% of the estimated body dose is distributed to the kidney. This may overestimate the fraction of uranium distributed to the kidneys of children, because the distribution in children is lower (approximately 9.5% for a child under 10) than in adults due to elevated uptake by bone (ATSDR 1999b; ICRP 1995a). Measurements of uranium in bones of persons exposed to uranium in the environment indicate that the concentration in children is higher than in adults because children have immature skeletons (ICRP 1995a).

   

Health Guidelines for Chemical Uranium

   
    

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

   

We compared our estimated exposure doses for ingestion of chemical uranium in groundwater to health-based guidelines to determine whether further evaluation of 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.

Radiation

For radiation effects, the bone surface is the primary target organ for ingested uranium. Although less uranium per gram of tissue goes to the bone surface than to the kidney, uranium is retained longer in the bone than in the kidney. Therefore, the bone surface receives more radiation as the uranium decays.

ATSDR scientists used the International Commission on Radiological Protection's (ICRP's) models and methodology (ICRP 1979, 1995a) to estimate the committed effective doses (whole body) and committed equivalent doses to the bone surface for both hypothetical exposure scenarios for groundwater.

Past Exposure

Although ATSDR scientists do not have direct information about whether wells 12, 13, 15, and 17 were ever used as drinking water sources, we evaluated potential past exposure based on uranium concentrations in these wells because they presumably had the highest concentrations and they represent possible points of human exposure. We evaluated past exposure using a range of maximum uranium concentrations that were measured and estimated in the well water. This concentration range is 578 micrograms of uranium per liter of water (578 mg/L) to 4,144 mg/L. The lower bound of the range is the maximum concentration measured in an off-site private well, which was found in well 15 in 1983 (Table 3). The upper bound of the range is the maximum estimated upper bound (95th percentile) concentration in wells 12, 15, and 17 in the 1960s (Voilleque et al. 1995). Maximum uranium concentrations and estimated past chemical exposure doses for a child (scenario #1) and an adult (scenario #2) are presented in Table 4 (below).

Table 4. Maximum concentrations and estimated chemical exposure doses for current and past exposure to uranium in water from private well 15 off site of the Fernald facility

 

 

Maximum Exposure Concentration or Range
(mg/L or ppb)

Body Dose*
(mg/kg/day)

Dose to Kidney*
(mg/g)

Current Exposure

 

 

 

Scenario #1: child

<100 to 283

0.006 to 0.008

0.003 to 0.005

Scenario #2: adult

<100 to 283

0.003 to 0.02

0.002 to 0.007

Past Exposure

 

 

 

Scenario #1: child

578 to 4,144

0.04 to 0.3

0.003 to 0.1

Scenario #2: adult

578 to 4,144

0.02 to 0.1

0.01 to 0.08

Key
mg/L = micrograms uranium per liter water
ppb = parts per billion
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. In estimating current doses, we assumed that the lower bound of the exposure concentration range (<100 ppb) was equal to 100 ppb.

As Table 4 shows, our estimated exposure doses (body doses) for past exposure are 0.04 to 0.3 milligrams of uranium per kilogram of body weight per day (mg/kg/day) for a child and 0.02 to 0.1 mg/kg/day for an adult. Our exposure estimates exceed the health-based guideline (0.002 mg/kg/day) for ingestion of uranium.

Our estimated upper-bound doses to the kidney for past exposure are 0.003 to 0.1 micrograms of uranium per gram of kidney tissue (mg/g) for a child, and 0.01 to 0.08 mg/g for an adult. The upper-bound estimate for a child is equal to the lower-bound threshold for kidney toxicity (of 0.1 mg/g), proposed by Morris and Meinhold (Morris and Meinhold 1995). (A discussion of the health-based guidelines for uranium, including the proposed threshold limits for kidney toxicity, are discussed in detail in the "Public Health Implications" section of this document.) However, there is considerable uncertainty in these upper-bound dose estimates, because they were calculated using water concentrations that were not measured directly but estimated from other environmental data. An additional source of uncertainty is whether persons were ever exposed to uranium at these estimated doses. ATSDR scientists do not have direct knowledge that persons drank water from wells 12, 15, and 17 during the 1960s, when they were estimated to have these maximum concentrations.

Further evaluation of past exposure to chemical uranium in groundwater, and the additional contribution of other pathways (e.g., air, surface water, biota) to total uranium exposure to Fernald residents, are discussed in the "Public Health Implications" section of this report.

The effects of past exposure to radioactive uranium (and its decay products) in drinking water have been addressed in the CDC's 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 presented in Appendix D of this report.

Current Exposure

ATSDR has no information about the number and location of residences near the Fernald site that are currently using privately owned wells for drinking and other household uses. In addition, we do not have current measurements of chemicals and radioactive materials in these wells, and some of them have never been sampled.

Therefore, for current ingestion of chemical uranium in private well water, we used a range of potential exposure concentrations in off-site private wells that were routinely sampled by the Fernald facility. Well 15 had the highest overall uranium concentrations of the wells that were routinely sampled. We used a range of concentrations in well 15 because uranium levels in the South Plume, and in this well, have been decreasing since the facility stopped operating. The upper end of this range is 283 mg/L which is the highest annual average uranium concentration ever detected in well 15 under current conditions. This maximum concentration was reported for 1989, 1990, and 1993 (DOE 1972 - 1999). Uranium concentrations in well 15 have declined to less than 100 mg/L in 1999 (DOE 1972 - 1999). Therefore, we used a concentration of 100 mg/L as a lower-bound concentration to estimate exposure dose under current conditions.

ATSDR=s estimated exposure doses (body doses) for current ingestion exposure to chemical uranium in off-site private well water are shown in Table 4 (above). Our estimated exposure doses for current exposure are 0.006 to 0.008 mg/kg/day for a child and 0.003 to 0.02 mg/kg/day for an adult. Therefore, our estimated exposure doses for a child and an adult exceed the health-based guideline for ingested chemical uranium. Our estimated kidney doses are at least 10 times lower than the lower-bound threshold for kidney toxicity (of 0.01 mg/g) proposed by Morris and Meinhold (Morris and Meinhold 1995). ATSDR scientists evaluated the public health hazard for this pathway together with other exposure pathways (i.e., soil, 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.

Residents of the Fernald site area may also be obtaining drinking water from cisterns (ODH 1988). Many of these cisterns were sampled in 1985 to 1988 (ODH 1988). Only one cistern was found to be contaminated with uranium at concentrations that are lower than currently present in off-site wells in the South Plume. Contamination of this cistern was presumed to have resulted from air particulate releases of uranium from the Fernald facility (ODH 1988). Because air particulate releases are currently much lower than they were while the facility was operating, it is not likely that cisterns in the Fernald area are contaminated at higher concentrations than reported for 1985 to 1988. This is especially true if cistern water is agitated frequently, as during regular use.

For radiation effects, ATSDR scientists used a range of uranium concentrations in well 15, as described for chemical uranium. The upper end of the range is 190 picocuries of uranium per liter of water (190 pCi/L), or 7.04 becquerels of uranium per liter of water (7.04 Bq/L), reported for 1989, 1990, and 1993 (DOE 1972 - 1999). By 1999, the uranium concentration in well 15 was reported as less than 67 pCi/L, or less than 2.48 Bq/L (DOE 1972 - 1999).

Table 5 presents ATSDR=s estimated committed effective (whole body) and committed equivalent (bone surface) doses for current ingestion of radioactive uranium in water from off-site privately owned wells. We estimated these doses using the ICRP=s models and methodology (ICRP 1995a). Further evaluation of human exposure to radioactive contaminants in groundwater, including a determination of whether these estimated doses present an increased likelihood of developing fatal cancers and bone cancer, is discussed in the "Public Health Implications" section of this report.

Table 5. Concentrations and estimated committed effective (whole body) and committed equivalent (bone surface) doses for current radiation exposure to uranium in private wells off site of the Fernald facility (based on annual ingestion)

 Scenario

Range of Concentrations from Maximum Exposure Well in pCi/L (Bq/L)

Committed Effective Dose (whole body) for 1 year of Ingestion in mrem (mSv)

Committed Equivalent Dose to Bone Surface for 1 year of Ingestion in mrem (mSv)

Scenario #1: child

< 67 (< 2.48) to
190 (7.04)

< 8.0 (< 0.08) to 22 (0.22)

< 113 (< 1.13) to 321 (3.21)

Scenario #2: adult

< 67 (< 2.48) to
190 (7.04)

< 9.0 (< 0.09) to 24 (0.24)

< 134 (< 1.34) to 380 (3.80)

Key
pCi/L = picocuries per liter
Bq/L = becquerels per liter
mrem = millirems
mSv = millisieverts


ATSDR has evaluated the potential for exposure, and health impact, from exposure to uranium and other radioactive materials in groundwater that is used by area residents for non-potable purposes (ATSDR 1996a). The results of this evaluation indicate that exposure doses do not exceed health-based guidelines (for chemical uranium) and do not contribute significantly to estimated committed effective doses and equivalent doses (for radioactive uranium and other radioactive materials) for this pathway.

Potential Future Exposure

ATSDR scientists evaluated the likelihood that off-site residential wells will be impacted by contaminants from the Fernald site in the future. To do this, we used current measurements of uranium and other contaminants in off-site groundwater and information about groundwater remediation strategies currently being implemented at the site. According to private well samples taken from 1996 and 1997, there are no contaminants in off-site groundwater, other than uranium, that necessitate remediation ahead of the proposed schedule for the South Plume (DOE 1972 - 1999). According to available environmental data, residents using private wells near the Fernald site in the future are not likely to be exposed to chemicals and radioactive materials from the site at levels greater than those currently present in the South Plume.

In 1999 and 2000, groundwater samples collected under the South Plume Module will also be analyzed for contaminants that may have originated from sources other than the Fernald site. Contractors at the Fernald facility consider the Paddy=s Run Road site, located on the southern edge of the South Plume, to be a potential source of groundwater contamination in the Fernald area (DOE 1972 - 1999). Other potential sources of groundwater contamination near the Fernald site may also be contributing to human exposures via this pathway. If additional information becomes available indicating that concentrations of uranium or other contaminants have increased to levels exceeding drinking water standards or other appropriate comparison values in off-site groundwater, groundwater 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. #