ATSDR - PHA - Paducah Gaseous Diffusion Plant (USDOE), Paducah, McCracken County, Kentucky

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PUBLIC HEALTH ASSESSMENT

PADUCAH GASEOUS DIFFUSION PLANT (U.S. DOE)
PADUCAH, MCCRACKEN COUNTY, KENTUCKY

Food and Biota Exposure Pathways

ATSDR scientists identified completed and potential pathways of human exposure to plants and animals containing contaminants of concern.

ATSDR scientists estimated human exposure doses using the maximum and average contaminant concentrations in Tables 18A and 18B and other conservative assumptions. We estimated exposure doses for a child (1 to 6 years old) who weighs 13 kg and for an adult who weighs 70 kg. We assumed average food consumption rates for persons from the United States in each biota category (Table 19). For fish consumption, we assumed average intake rates for subsistence fishers and their children and for recreational fishers and their children. We also assumed that 20% of all food in a person's diet was harvested from a contaminated source. Estimated chemical exposure doses are in Tables 20A and 20B for a child and an adult, respectively. The estimated doses (total committed doses) for radioactive contaminants are in Tables 21A and 21B for children and adults, respectively.

Table 19. Average food consumption rates for children and adults¹

Age Group Fish
(g/day) Game
(g/day) Apples, Grapes
(g/kg/day) Persimmons
(g/kg/day) Nuts, Legumes
(g/kg/day) Green Vegetables
(g/kg/day) Yellow Vegetables
(g/kg/day) Tomatoes
(g/kg/day)

S R

Child
(1 to 6 years) 20 3 1 1.6 0.004 1.2 0.85 0.57 0.8

Adult 60 8 2 1.6 0.004 1.2 0.85 0.57 0.8

¹ Fish consumption rates are for average subsistence fishers and recreational fishers. Intake rates for all other types of biota are based on average U.S. persons (for game), average U.S. per capita rates (for persimmons), or southern U.S. per capita rates (for apples, nuts, legumes, dark green vegetables, yellow vegetables, and tomatoes).

Sources: Fish = Columbia River Inter-Tribal Fish Commission (CRITFC), 1994, and EPA Exposure Factors Handbook (EFH), 1999 [117].
Game = U.S. Dairy Association (USDA) Nationwide Consumption Survey, 1987-1988, in EPA, 1995 [99].
Apples, nuts, legumes, dark green vegetables, yellow vegetables, and tomatoes = EPA, 1995 [99], reference EPA, 1984d.
Grapes and persimmons = U.S. EPA's Dietary Risk Evaluation System (DRES), in EPA, 1995 [99].

Key: g/day = grams per day; g/kg/day = grams of food per kilogram of body weight per day; S = subsistence; R = recreational

ATSDR scientists then compared the total estimated exposure doses for chemicals to appropriate health guidelines. Tables 20A and 20B illustrate this comparison. (Appendix C of this report describes the health guidelines we used.) Only the PCB exposure doses for specific exposure scenarios exceed the health guideline; they will be discussed further in the public health implications section. For radioactive materials, the estimated annual committed effective doses for this exposure pathway are less than 1 millirem, which would not cause an adverse health effect. Nonetheless, the public health implications section discusses exposure to radioactive contaminants for each exposure pathway; therefore, they are included in Table 22.

Table 20A. Maximum estimated child exposure doses and health guidelines for consumption of biota near PGDP for chemical contaminants (in milligrams per kilogram of body weight per day)

Chemical Fish
(Tissue) Game
(Meat) Apples Persimmons Nuts, Legumes Yellow or Green Vegetables Estimated Total Exposure Dose per Chemical Health Guide-line¹ Is Total Exposure Dose > Health Guideline?

Aluminum 0.0535 0.00036 0.01939 0.00004 0.01433 0.03135 0.11897 2.00 No

Arsenic 0.00022 0.00000 0.00003 ND 0.00002 0.00005 0.0003 0.0003 No

Barium 0.00074 0.00017 NR NR 0.00672 NR 0.00763 0.07 No

Beryllium NR 0.00001 ND ND ND ND 0.00001 0.002 No

Cadmium NR 0.00009 ND NR NR NR 0.00009 0.0002 No

Chromium 0.00126 0.00002 0.00067 0.00000 0.00046 0.00026 0.00267 1.00 No

Copper 0.00668 0.00037 0.00490 0.00001 0.00334 0.01132 0.02662 0.04 No

Fluoride 0.0043 0.0043 0.05 to 0.06 No

Lead 0.00120 0.00004 0.00058 0.00000 0.00019 0.00042 0.00243 0.02 No

Manganese 0.00526 0.00005 0.00102 0.00005 0.01522 0.01068 0.03228 0.14 No

Mercury 0.00014 0.00007 ND ND ND ND 0.00021 0.0003 No

Nickel NR 0.00012 0.00230 0.00000 0.00139 0.00508 0.00889 0.02 No

Selenium 0.00028 0.00002 ND ND ND ND 0.0003 0.005 No

Silver NR 0.00009 ND ND ND ND 0.00009 0.005 No

Uranium NR 0.00003 NR NR NR NR 0.00003 0.002 No

Vanadium ND 0.00001 ND NR NR NR 0.00001 0.003 No

Zinc 0.01815 0.00060 0.00371 0.00001 0.00238 0.00874 0.03359 0.3 No

Total PCBs 0.00387 0.00000 0.00387 0.00002 Yes

PCB (Aroclor 1254) 0.00164 0.00164 0.00002 Yes

¹For an explanation of health guidelines and exposure calculations, refer to Appendix C.

Key: NR = not reported; ND = not detected; PCBs = polychlorinated biphenyls

Table 20B. Maximum estimated adult exposure doses and health guidelines for consumption of biota near PGDP for chemical contaminants (in milligrams per kilogram of body weight per day)

Chemical Fish
(Tissue) Game
(Meat) Apples, Grapes Persimmons Nuts, Legumes Yellow Vegetables Estimated Total Exposure Dose per Chemical Health Guide-line¹ Is Total Exposure Dose > Health Guideline?

Aluminum 0.02983 0.00013 0.01939 0.00004 0.01433 0.03135 0.09507 2.00 No

Arsenic 0.00012 0.00000 0.00003 NR 0.00002 0.00005 0.00022 0.0003 No

Barium 0.00041 0.00006 NR NR 0.00672 NR 0.00719 0.07 No

Beryllium NR 0.00000 NR NR NR NR 0.00000 0.002 No

Cadmium NR 0.00003 NR NR NR NR 0.00003 0.0002 No

Chromium 0.00070 0.00001 0.00067 0.00000 0.00046 0.00026 0.00210 1.00 No

Copper 0.00372 0.00014 0.00490 0.00001 0.00334 0.01132 0.02341 0.04 No

Fluoride NR NR NR NR NR NR 0.0043 0.05 to 0.06 No

Lead 0.00067 0.00001 0.00058 0.00000 0.00019 0.00042 0.00187 0.02 No

Manganese 0.00293 0.00002 0.00102 0.00005 0.01522 0.01068 0.02992 0.14 No

Mercury 0.00008 0.00003 NR NR NR NR 0.00011 0.0003 No

Nickel 0.00005 0.00230 0.00000 0.00139 0.00508 0.00882 0.02 No

Selenium 0.00015 0.00001 NR NR NR NR 0.00016 0.005 No

Silver NR 0.00003 NR NR NR NR 0.00003 0.005 No

Uranium NR 0.00001 NR NR NR NR 0.00001 0.002 No

Vanadium NR 0.00000 NR NR NR NR 0.00000 0.003 No

Zinc 0.01011 0.00022 0.00371 0.00001 0.00238 0.00874 0.02517 0.3 No

Total PCBs 0.00215 0.00000 NR NR NR NR 0.00215 0.00002 Yes

PCB (Aroclor 1254) 0.00092 NR NR NR NR NR 0.00092 0.00002 Yes

¹For an explanation of health guidelines and a discussion of the dose calculations, refer to Appendix C.

Key: NR = not reported; PCBs = polychlorinated biphenyls

Table 21A. Estimated child exposure doses (annual committed effective doses) for annual consumption of biota near PGDP in millirems (and in millisieverts) [60]

Radioactive Contaminant Fish Game
(meat) Apples, Grapes Other Fruit
(Persimmons) Nuts, Legumes Green Vegetables Yellow Vegetables¹ Tomatoes Total Estimated Committed Effective Dose

Technetium 99 0.018
(1.8E-04) 0.009
(9.2E-05) 0.003
(2.7E-05) 0.006
(6.1E-05) 0.167
(1.67E-03) 0.001
(6.0E-06) 0.001
(1.1E-05) 0.002
(2.3E-05) 0.21
(2.1E-03)

Uranium 234 0.006
(6.3E-05) 0.016
(1.6E-04) 0.008
(8.4E-05) 0.000
(0.000) 0.002
(1.9E-05) 0.005
(4.5E-05) 0.004
(3.5E-05) 0.006
(6.2E-05) 0.05
(4.6E-04)

Uranium 235 0.002
(1.6E-05) 0.001
(1.1E-05) 0.001
(1.4E-05) 0.000
(0.000) 0.001
(1.1E-05) 0.001
(1.0E-05) 0.006
(6.0E-05) 0.004
(3.8E-05) 0.02
(1.6E-04)

Uranium 238 0.002
(1.5E-05) 0.023
(2.3E-04) 0.002
(2.2E-05) 0.000
(0.000) 0.000
(3.0E-06) 0.000
(2.0E-06) 0.010
(9.6E-05) 0.003
(2.5E-05) 0.04
(3.9E-04)

Thorium 230 0.008
(8.2E-05) 0.008
(7.5E-05) 0.002
(1.7E-05) 0.000
(0.000) 0.001
(1.3E-05) 0.003
(2.8E-05) 0.001
(1.2E-05) 0.009
(8.7E-05) 0.03
(3.1E-04)

Plutonium 239 0.010
(9.8E-05) 0.000
(0.000) 0.002
(1.9E-05) 0.01
(1.2E-04)

Americium 241 0.004
(4.4E-05) 0.00
(4.4E-05)

Neptunium 237 0.000
(2.0E-06) 0.001
(6.0E-06) 0.000
(4.0E-06) 0.000
(3.0E-06) 0.001
(1.2E-05) 0.00
(2.7E-05)

Strontium 90 0.029
(2.9E-04) 0.03
(2.9E-04)

Cesium 137 0.000
(1.0E-06)

Estimated annual committed effective dose 0.036
(3.6E-04) 0.100
(1.0E-03) 0.016
(1.6E-04) 0.006
(6.1E-05) 0.172
(1.7E-03) 0.010
(9.5E-05) 0.022
(2.2E-04) 0.027
(2.7E-04) 0.39
(3.9E-03)

Total estimated annual committed effective dose for all above radioactive contaminants in food crops is 0.39 millirems (or 3.9E-03 millisieverts)

¹ "Yellow vegetables," in this table, includes eggplant, mixed vegetables, soybeans, carrots, corn, and squash.

Table 21B. Estimated adult exposure doses (annual committed effective doses) for annual consumption of biota near PGDP in millirems (and in millisieverts) [60]

Radioactive Contaminant Fish Game
(meat) Apples, Grapes Other Fruit
(Persimmons) Nuts, Legumes Dark Green Vegetables Yellow Vegetables¹ Tomatoes Total Estimated Committed Effective Dose

Technetium 99 0.024
(2.4E-04) 0.005
(5.1E-05) 0.004
(4.1E-05) 0.009
(9.1E-05) 0.250
(2.5E-03) 0.001
(0.9E-05) 0.002
(1.7E-05) 0.003
(3.4E-05) 0.298
(29.8E-04)

Uranium 234 0.017
(1.7E-04) 0.018
(1.8E-04) 0.025
(2.5E-04) 0.000
(0.1E-05) 0.006
(5.6E-05) 0.014
(1.4E-04) 0.011
(1.1E-04) 0.019
(1.9E-04) 0.110
(11.0E-04)

Uranium 235 0.004
(4.3E-05) 0.001
(1.3E-05) 0.004
(4.3E-05) 0.000
(0.000) 0.003
(3.2E-05 ) 0.003
(3.0E-05) 0.018
(1.8E-04) 0.011
(1.1E-04) 0.044
(4.4E-04)

Uranium 238 0.004
(4.1E-05) 0.026
(2.6E-04) 0.007
(6.8E-05) 0.000
(0.000) 0.001
(1.0E-05) 0.001
(0.7E-05) 0.029
(2.9E-04) 0.008
(7.5E-05) 0.076
(7.6E-04)

Thorium 230 0.027
(2.7E-04) 0.010
(1.0E-04) 0.006
(6.4E-05) 0.000
(0.000) 0.005
(4.8E-05 ) 0.010
(1.0E-04) 0.005
(4.5E-05) 0.032
(3.2E-04) 0.095
(9.5E-04)

Plutonium 239 0.015
(1.5E-04) 0.000
(0.000) 0.008
(7.6E-05) 0.023
(2.3E-04)

Americium 241 0.007
(6.5E-05) 0.007
(0.7E-04)

Neptunium 237 0.000
(0.3E-05) 0.003
(2.5E-05) 0.002
(1.8E-05) 0.001
(1.2E-05) 0.005
(5.0E-05) 0.011
(1.1E-04)

Strontium 90 0.035
(3.5E-04) 0.035
(3.5E-04)

Cesium 137 0.000
(0.1E-05) 0.000
(0.0E-04)

Estimated annual committed effective dose 0.076
(7.6E-04) 0.117
(11.7E-04) 0.047
(4.7E-04) 0.009
(9.2E-05) 0.267
(2.67E-03) 0.030
(3.0E-04) 0.065
(6.5E-04) 0.085
(8.5E-04) 0.699
(7.0E-03)

Total estimated annual committed effective dose for all above radioactive contaminants in food crops is 0.70 millirems (or 7.0E-03 millisieverts)

¹ "Yellow vegetables," in this table, includes eggplant, mixed vegetables, soybeans, carrots, corn, and squash.

Current Exposure

Chemical and radioactive contaminants have been detected in fish samples from Little Bayou and Bayou Creeks and from outfalls east of the plant. Most of the biota sampling data reflect current or recent past conditions.

The estimated total annual committed effective doses for all radioactive contaminants in biota do not exceed 1 millirem. This level would not produce an adverse health effect; however, radioactive materials from the combined exposure pathways will be discussed in the public health implications section.

The estimated total exposure doses for total PCBs and Aroclor 1254 exceed the health guidelines. PCB exposure doses were calculated under two different exposure scenarios (subsistence fishers and recreational fishers) for adults and children in Bayou Creek, Little Bayou Creek, and Outfall#11/Little Bayou Creek. Outfall #11 had the highest concentrations of PCBs in fish. This outfall has restricted access and is posted with fish consumption advisory signs [48]. It is unlikely that anyone would regularly fish in Outfall #11 and/or regularly eat fish caught at Outfall #11. Fish collected from Little Bayou Creek had higher PCB concentrations than fish from Bayou Creek. (Our site visits and observations indicate that people are more likely to fish in Bayou Creek.) It should be noted that the Ohio River provides a more extensive fishing area and offers easier access; therefore, fishing in the PGDP area is probably rarer than we estimate it to be. PCB analyses were not conducted for food crops; however, uptake of PCBs by plants is very low [101], and fish consumption would be the main exposure pathway for PCBs. ATSDR's assumptions are conservative and may overestimate exposure doses. Despite uncertainties in estimating human exposure doses, total PCBs and Aroclor 1254 were selected as contaminants of concern for current biota exposure pathways.

Past Exposure

Since the majority of off-site releases occurred in the 1950s and early 1960s, and no sampling data are available for that time period, ATSDR scientists assumed that higher concentrations of chemical and radioactive contaminants in biota were possible. Also, outfalls to the creeks would not have been posted or restricted as they now are. Having discussed the matter with staff at the Kentucky Department for Environmental Protection, however, we believe that very few fish, if any, lived in Little Bayou Creek during these early years and very few people, if any, chronically fished in these areas. Since there were better places to fish in close proximity, we believe fishers would not have routinely fished in this creek system; however, despite the uncertainties, we selected total PCBs and Aroclor 1254 as contaminants of concern for past biota exposure pathways.

Potential Future Exposure

With access restrictions to areas near Outfalls #10 and #11 and posting of signs along Little Bayou Creek, potential future chronic exposure is not expected. However, other off-site fishing areas, such Bayou Creek and some nearby ponds, are potential sources of fish with chemical and radioactive contaminants and should continue to be monitored. Until the site remediation is completed, crops and game may continue to be contaminated at low levels. Therefore, ATSDR scientists identified potential future exposure pathways for biota. If additional biota sampling data become available, these human exposure pathways will be re-evaluated.

Table 22. Summary of potential exposure pathways for human consumption of contaminants of concern in biota near PGDP

Major Source Contaminants Point of Exposure Route of Exposure Exposed Population Period of Time Maximum Estimated Exposure Doses

Plant operations and waste disposal activities that release contaminants to soil, surface water, and air that are transported to creeks and pond near the plant Total PCBs
Aroclor 1254 Fish from Little Bayou Creek Ingestion Children and adults who eat 20% of their fish intake from Little Bayou and Bayou creeks Past, Current, and Potential Future
Access to Little Bayou creek is partially restricted and fishing advisories are posted Total PCBs
Adults: 0.00215 mg/kg/d
Children: 0.00387 mg/kg/d
PCB--Aroclor 1254
Adults: 0.00092 mg/kg/d
Children: 0.00164 mg/kg/d

Radioactive contaminants All biota in Tables 20A and 20B Ingestion Children and adults who eat 20% of their intake of fish, game, fruits and vegetables from areas near PGDP Radioactive Contaminants
(annual intake)
Adults: 0.7 mrem (0.007 mSv)
Children:0.4 mrem (0.004 mSv)

Key: mg/kg/d = milligrams of contaminant per kilogram of body weight per day; mrem = millirems; mSv = millisieverts

Other Hazards

Storage of Depleted Uranium Cylinders

Uranium hexafluoride (UF₆) is a solid stored under vacuum in steel cylinders in outdoor storage yards [102]. Most of the cylinders are 12 feet (about 3 � meters) long and 4 feet (about 1 meter) in diameter, with a nominal wall thickness of 5/16 inch (8 millimeters). The largest storage area at PGDP is in the southeast corner of the site. There are about 40,351 cylinders of depleted UF₆ stacked two layers high at Paducah; 28,351 of them were generated by DOE and about 12,000 were generated by the U.S. Enrichment Corporation (USEC)⁽⁵⁾ [5,103].

Although DOE believes that these cylinders do not present a health concern directly, the storage of large quantities of this material in one place has raised concerns among the local community and others. In 1994 and 1995, the Defense Nuclear Facilities Safety Board visited the gaseous diffusion plants at Paducah, Portsmouth, and Oak Ridge [104]. Their recommendation included a program to better maintain the physical condition of the cylinders, to better protect the cylinders from exposure to the elements and from damage during handling, and to study the feasibility of storing the material in a more suitable chemical form for long-term storage of the depleted uranium. In 1995, DOE submitted a plan to implement these recommendations. The plan included repainting cylinders to avoid excessive corrosion, removing cylinders from ground contact, spacing cylinders better to facilitate improved inspections, and improving handling procedures. DOE also completed a baseline inspection of all cylinders in 1994. Their plan calls for inspecting 25% of the cylinders each year and inspecting all the older cylinders each year [102].

Depleted UF₆ is a white, crystalline solid when it is stored at temperatures below 134^oF (57^oC) at atmospheric pressure [5]. If one of the cylinders leaked, the UF₆ would react with moisture in the atmosphere to form hydrogen fluoride (HF) gas and uranium reaction products such as solid uranyl fluoride. The solid would seal small leaks or cracks, preventing the escape of radioactive and chemical materials from the cylinders. If there were more severe damage to a cylinder, however, these materials might escape into the atmosphere and be a potential source of exposure to nearby residents, especially if the incident involved a fire.

Because the cylinders are currently being stored outside, the community is concerned about the possibility of a major accident that would damage the cylinders and result in large-scale release of UF₆, and other reaction products, to the environment. Severe lightning storms, tornadoes, earthquakes, transportation accidents, or plane crashes are examples of major incidents. These are discussed below.

Storms

A search of storm event data from the National Oceanographic and Atmospheric Administration's National Climatic Data Center (NCDC) revealed historical information for Ballard and McCracken counties in Kentucky [105]. Information on tornado activity is available from January 1, 1950, through December 31, 1991, and from January 1, 1995, through December 1998. During these 46 years, two tornadoes were recorded in Ballard County, with winds ranging from 40 to 206 miles per hour (64 to 332 kilometers per hour). In McCracken County, seven tornadoes and one funnel cloud were recorded, with winds from 73 to 157 miles per hour (118 to 253 kilometers per hour). These are considered small to mid-size tornadoes. Due to the cylinders' weight (each weighs 10 to 14 tons, or 9 to 12 metric tons), shape, and design, it is improbable that one of these storms would damage or move the cylinders. Other severe weather conditions causing property damage, injury, or death have only been recorded by NCDC from January 1, 1995, through December 31, 1998. During these 4 years, Ballard County and McCracken County each had one lightning storm that caused property damage. Since lightning is usually attracted to the highest structure in the area--which would not be the cylinder yards--and it is not common for lightning to cause property damage in this area, it is improbable that one of these storms would damage the cylinders.

Earthquakes

The Paducah area has a high probability for moderate earthquake activity in the near future according to U.S. Geological Survey scientists [106].

In the winter of 1811/1812, three of the largest earthquakes in North America occurred in the New Madrid seismic zone, adjacent to western Kentucky. Each of these three earthquakes had magnitudes of over 8.0 on the Richter Scale⁽⁶⁾ [107], or moment magnitude¹ of 7.1 to 7.5 according to recent reports [109]. However, based on recent unpublished data it is now estimated that the largest earthquake of the series was a moment magnitude of 7.7. On February 7, 1812, the last earthquake's epicenter was located near New Madrid, Missouri, which is 60 miles (97 kilometers) southwest of the current Paducah Gaseous Diffusion Plant site. Two other earthquakes of similar size occurred on December 16, 1811 and January 23, 1812, and thousands of aftershocks rocked the region during that winter [106]. Since then two major earthquakes have occurred [107]. A magnitude 6.5 earthquake occurred near Marked Tree, Arkansas in 1843, and a magnitude 6.8 earthquake occurred near Charleston, Missouri in 1895. Earthquakes of smaller magnitude have occurred in the past and continue to occur today. Most are too small to be felt by humans. The largest earthquakes in this seismic zone in recent times were a magnitude 5.0 earthquake in 1976 and a magnitude 4.8 earthquake on September 26, 1990.

It is not possible to predict the exact date, duration, or magnitude of an earthquake. From information known about the region, scientists can estimate the potential for different magnitude earthquakes. Scientists at the Center for Earthquake Research and Information estimated the potential for different magnitude earthquakes to occur in this region by computing sets of probabilities, as shown in the table below [107].

Table 23. Probabilities of Occurrence for Different Magnitude Earthquakes [107]

Magnitude Average Repeat Time (in years) Probability of occurrence in 15 years (%) Probability of occurrence in 50 years (%)

6.3 70 +/- 15 40 - 63 86 - 97

7.6 254 +/- 60 5.4 - 8.7 19 - 29

8.3 550 +/- 125 0.3 - 1.0 2.7 - 4.0

The magnitude of the earthquake is a measurement of the total energy released. The energy is transferred by movement in the ground which is modified as it moves through local rock and soil [109]. The ground movement may arrive at the ground surface with lesser or higher violence (intensity of shaking) depending on the frequency of the motions. In the Paducah area, it appears that low-frequency motions are amplified by thick soils and virtually unaffected by thin soils. However, high frequency motions are attenuated by thick soils and amplified by thin soils [109].

Dr. James Beavers from the University of Illinois at Urbana and Deputy Director of the Mid-America Earthquake Center has estimated that the topsoil peak ground acceleration⁽⁷⁾ at PGDP during a 2% probability earthquake in 50 years (moment magnitude of 7.75) would be approximately 0.5 g [110]. This would create a relatively high potential for earthquake damage unless the structures were designed and constructed under the strictest construction codes.

Citizens have raised concerns about the consequences of a major earthquake on the stored uranium cylinders. For the 2% probability earthquake in 50 years, it is likely that the cylinders would move around and potentially be breached. The consequences could include on-site fatalities from physical injuries and from exposure to UF₆ and the reaction products and significant off-site injuries from exposure to UF₆ and the reaction products.

Transportation and Plane Accidents

Cylinders could be damaged or burn during transportation accidents, or plane crashes. Currently, DOE is not transporting cylinders to or from the PGDP site. Plane crashes are a possibility, since the Barkley Airport is about 3.7 miles (6 kilometers) southeast of the site. A plane crash accompanied by fire could damage the cylinders. As part of the Programmatic Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of Depleted Uranium Hexafluoride [5], Argonne National Laboratory used a FIREPLUME model to predict concentrations of materials released from UF₆ cylinders under five accident scenarios and two weather conditions (F and D stability classes)[111]. These scenarios include:

Vehicle-induced fire with the rupture of three full 48G cylinders. (Primarily used for depleted UF₆ storage.)
Vehicle-induced fire with the rupture of three full 48Y cylinders. (Primarily used for transporting natural UF₆).
Small aircraft-induced fire with the rupture of two full 48G cylinders.
Small aircraft-induced fire with the rupture of two full 48Y cylinders.
Vehicle-induced fire with the rupture of two heel cylinders.

The model assumed that UF₆ contained in cylinders was damaged in the accident, causing the release of HF gas and uranyl fluoride particulates to the atmosphere. For each scenario, they predicted concentrations at distances of 30 to 12,068 meters (about 100 feet to 7.5 miles) from the accident. They determined that the maximally exposed individual was 30 meters downwind of the accident. At each distance, the estimated dose was directly influenced by the airborne concentrations and the length of exposure time. The worst-case scenario (number 2) was a vehicle-induced fire with the rupture of three full 48Y cylinders (assuming F stability). Under this scenario, the maximally exposed individual would be exposed to 2,700 mg/m³ (or 3,293 ppm) of HF and 180 mg/m³ (or 2,250 ppm) of uranyl fluoride [111].

Health Hazard Evaluation

The estimated HF and uranyl fluoride exposure concentrations for the maximally exposed individual in accident scenario 2 (described on previous page) are high enough to pose a temporary urgent public health hazard; however, the probability of this type of accident occurring is very low. These substances are discussed below since they relate to this accident scenario. They may also be discussed in the public health implications section of this report.

Hydrogen Fluoride

HF is a colorless gas or liquid with a strong, irritating odor. It can be smelled in the air at concentrations of 0.5 to 3 ppm. The gas will readily react with water, releasing corrosive and toxic gases. Contact with metal can produce flammable hydrogen gas. Containers of HF can explode when heated or contaminated with water [112].

HF is highly corrosive and produces adverse effects at the point of contact, which is usually the respiratory tract (nose, throat, trachea, bronchi), eyes, and skin. Because HF is absorbed into the bloodstream, it can affect other organs in the body, such as the lungs, liver, kidney, and heart. Short-term exposure to HF in air at concentrations as low as 20 ppm can be tolerated for 1 minute, although concentrations of 120 ppm irritate the nose, throat, eyes, and skin in humans [112]. Vapors can cause ulcers of the respiratory tract at concentrations of 50 to 250 ppm--this concentration can be dangerous, even for brief exposures. Inhalation of HF at higher concentrations can cause severe throat irritation, cough, lung injury, and pulmonary edema (swelling) resulting in death. HF readily penetrates the skin and can cause deep tissue destruction and burns following dermal exposure. Exposure to the eye can result in irritation to severe ocular damage and visual effects.

The National Institute of Occupational Safety and Health recommends that exposure to HF by workers not exceed 3 ppm (or 2.5 mg/m³), with a 15-minute ceiling of 6 ppm (or 5 mg/m³). The recommendations are intended to protect workers from effects on the respiratory tract, eyes, skin, and bones. The recommendations are based on occupational studies of workers and laboratory animals. One study of rabbits and guinea pigs exposed to HF, at concentrations of 24 to 8,000 ppm for 5 to 41 minutes, reported eye and respiratory tract irritation at all exposure concentrations [113]. A significant number of animals died within 5 minutes when they inhaled air containing 1,500 mg/m³ of hydrogen fluoride. Weakness and appearance of illness were apparent in all animals at concentrations above 500 mg/m³ for 15 minutes or longer. Rabbits that survived returned to normal within a few weeks, but guinea pigs showed a definite tendency to delayed response and death between the fifth and tenth week following exposure.

Argonne's estimated exposure levels were at least 10 times higher than reported to cause adverse effects in humans (workers) and animals. Therefore, ATSDR concludes that potential future exposure to HF, at an estimated exposure level of 3,300 ppm for a hypothetical maximally exposed individual in accident scenario 2, poses an urgent health hazard.

Uranyl Fluoride

Uranyl fluoride is water-soluble. Its toxicity is determined primarily by route of exposure; exposure concentration, duration, and frequency; and particle size. Ingestion generally produces less toxicity than inhaled uranium, because uranium is poorly absorbed from the gastrointestinal tract following ingestion. Respiratory and kidney toxicity are the targets for inhaled uranium.

ATSDR has developed an intermediate-duration health guideline for exposure to uranyl fluoride in air. The guideline is 0.0004 mg/m³ (or 0.005 ppm) and is based on a study in which dogs were exposed to uranyl fluoride in air daily for 5 weeks [114]. The lowest dose at which adverse effects on the kidney were observed in these animals was 0.15 mg/m³ (or 2 ppm). ATSDR applied a safety factor of 90 to this lowest dose, because humans may be more sensitive than dogs, some humans may be more sensitive than others, and there was no dose at which no adverse effects were seen. Although Argonne National Laboratory's estimated exposure concentration (180 mg/m³, or 2,250 ppm) was several orders of magnitude higher than the health guideline, the health guideline was based on an intermediate-duration study in which animals were exposed for 5 weeks. It is likely that exposure to uranyl fluoride during an accident will occur over a shorter (acute) duration.

A similar study in dogs acutely exposed to uranyl fluoride (one exposure lasting � to 1 hour) found extensive degeneration in kidney tissue following exposure at a concentration of 250 mg/m³ (more than 3,000 ppm) [115]. ATSDR considered these effects to be too severe to use the study as a basis for developing a health guideline. If we did derive a "guideline" by applying a similar safety factor of 90 to this concentration, the resulting "guideline" would be about 35 ppm. Argonne's estimated exposure concentration for uranyl fluoride, for the maximally exposed individual under scenario 2, was considerably higher than this "guideline." Therefore, ATSDR concludes that potential future exposure to uranyl fluoride, at an estimated exposure level of 180 ppm for a hypothetical maximally exposed individual in accident scenario 2, poses a public health hazard.

Additional Facilities

DOE is evaluating the feasibility of building a facility (or facilities) to convert its UF₆ to a more stable form for long-term storage, use, or permanent disposal. DOE prefers to begin converting the depleted UF₆ inventory to uranium oxide or uranium metal, or a combination of both, as soon as possible, but to allow for use of as much inventory as possible. Conversion to oxide for use or long-term storage would begin as soon as possible, with conversion to metal only if uses for the metal are identified [5]. DOE is now participating in a conversion pilot project with the private sector [116].

DOE stores the majority of its depleted uranium cylinders at PGDP. Many of the storage cylinders are not approved for transportation; therefore, it is logical that the conversion facilities would be built at or near the gaseous diffusion plants. On August 11, 1998, President Clinton signed Public Law 105-204 (Section 1. United States Enrichment Corporation) which states:

(a) Plan. -- The Secretary of Energy shall prepare, and the President shall include in the budget request for fiscal year 2000, a plan and proposed legislation to ensure that all amounts accrued on the books of the United States Enrichment Corporation for the disposition of depleted uranium hexafluoride will be used to commence construction of, not later than January 31, 2004, and to operate, an on-site facility at each of the gaseous diffusion plants at Paducah, Kentucky, and Portsmouth, Ohio, to treat and recycle depleted uranium hexafluoride consistent with the National Environmental Policy Act....(c) Sense of the Senate. - It is the sense of the Senate that Congress should authorize appropriations during fiscal year 2000 in an amount sufficient to fully fund the plan described in subsection (a).

(We assume that these facilities would also be used to dispose of DOE's depleted UF₆.)

The community is concerned about transportation accidents that might occur if cylinders from other sites were brought to PGDP. Since conversion facilities are proposed at two sites, about 4,700 cylinders at Oak Ridge, Tennessee, would have to be transported. The material in these old cylinders will need to be transported in cylinders or overpacks approved for transport by appropriate regulatory authority before the transfer occurs. ATSDR recommends using approved transport cylinders or overpacks to transport any depleted uranium cylinders to or from PGDP.

The community is also concerned about potential environmental contaminants that the new facility might produce. The potential environmental contaminants from a conversion plant at a specific site are hard to predict until the technology is decided upon and the facilities are planned. When plans for the new facilities are proposed for the two sites, Environmental Impact Statements (EIS) required by the National Environmental Policy Act of 1969 will assess the site-specific impact of the proposed facilities on human and natural environments. DOE's final Programmatic Environmental Impact Statement [5] issued in April 1999 presented alternatives for long-term management of the depleted UF₆ and included a comparison of impacts on human health and the environment for the alternative management strategies; however, it did not include the detailed, site-specific information that would be required in an EIS.

Concrete Rubble

Potentially contaminated concrete rubble from PGDP was used at PGDP, the Tennessee Valley Authority Shawnee Steam Plant reservation, the Western Kentucky Wildlife Management Authority (WKWMA), and the Ballard County Wildlife Management Area approximately 11 miles (18 kilometers) west of PGDP, for bank erosion control, dam and structural support, and roadway stabilization [10,11]. Since the concrete was potentially contaminated, DOE and the Commonwealth of Kentucky surveyed the rubble piles and the adjacent soils and sediments. Contaminated soil piles were removed from an area at the WKWMA in July 1996; no further remedial actions are planned. The remaining rubble piles do not pose a public health hazard.

5. In May and June 1998, DOE assumed management responsibility for approximately 11,400 cylinders generated by USEC.
6. The Richter Scale is a logarithmic scale ranging from 1 to 10, for expressing the magnitude or total energy of an earthquake. This scale was invented in 1935, but is rarely used today by scientists. Instead moment magnitude, a scale of numbers developed by Hiroo Kanamori in 1977, is used. For both scales, the stronger the earthquake is the higher the number. They are nearly identical for most earthquakes with a magnitude less than 7; however, moment magnitude more accurately describes the strongest earthquakes [104].
7. Peak ground acceleration is a measurement of the amount of surface ground movement and is defined as the maximum acceleration an object attached to the ground would experience during an earthquake. (The earth's gravity always subjects an object to 1 g; the peak ground acceleration would be the number of additional g's the object would be subject to.)

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Agency for Toxic Substances and Disease Registry, 1825 Century Blvd, Atlanta, GA 30345
Contact CDC: 800-232-4636 / TTY: 888-232-6348

Department of Health and Human Services

Age Group	Fish (g/day)		Game (g/day)	Apples, Grapes (g/kg/day)	Persimmons (g/kg/day)	Nuts, Legumes (g/kg/day)	Green Vegetables (g/kg/day)	Yellow Vegetables (g/kg/day)	Tomatoes (g/kg/day)
	S	R
Child (1 to 6 years)	20	3	1	1.6	0.004	1.2	0.85	0.57	0.8
Adult	60	8	2	1.6	0.004	1.2	0.85	0.57	0.8
¹ Fish consumption rates are for average subsistence fishers and recreational fishers. Intake rates for all other types of biota are based on average U.S. persons (for game), average U.S. per capita rates (for persimmons), or southern U.S. per capita rates (for apples, nuts, legumes, dark green vegetables, yellow vegetables, and tomatoes).
Sources: Fish = Columbia River Inter-Tribal Fish Commission (CRITFC), 1994, and EPA Exposure Factors Handbook (EFH), 1999 [117]. Game = U.S. Dairy Association (USDA) Nationwide Consumption Survey, 1987-1988, in EPA, 1995 [99]. Apples, nuts, legumes, dark green vegetables, yellow vegetables, and tomatoes = EPA, 1995 [99], reference EPA, 1984d. Grapes and persimmons = U.S. EPA's Dietary Risk Evaluation System (DRES), in EPA, 1995 [99].
Key: g/day = grams per day; g/kg/day = grams of food per kilogram of body weight per day; S = subsistence; R = recreational

Chemical	Fish (Tissue)	Game (Meat)	Apples	Persimmons	Nuts, Legumes	Yellow or Green Vegetables	Estimated Total Exposure Dose per Chemical	Health Guide-line¹	Is Total Exposure Dose > Health Guideline?
Aluminum	0.0535	0.00036	0.01939	0.00004	0.01433	0.03135	0.11897	2.00	No
Arsenic	0.00022	0.00000	0.00003	ND	0.00002	0.00005	0.0003	0.0003	No
Barium	0.00074	0.00017	NR	NR	0.00672	NR	0.00763	0.07	No
Beryllium	NR	0.00001	ND	ND	ND	ND	0.00001	0.002	No
Cadmium	NR	0.00009	ND	NR	NR	NR	0.00009	0.0002	No
Chromium	0.00126	0.00002	0.00067	0.00000	0.00046	0.00026	0.00267	1.00	No
Copper	0.00668	0.00037	0.00490	0.00001	0.00334	0.01132	0.02662	0.04	No
Fluoride						0.0043	0.0043	0.05 to 0.06	No
Lead	0.00120	0.00004	0.00058	0.00000	0.00019	0.00042	0.00243	0.02	No
Manganese	0.00526	0.00005	0.00102	0.00005	0.01522	0.01068	0.03228	0.14	No
Mercury	0.00014	0.00007	ND	ND	ND	ND	0.00021	0.0003	No
Nickel	NR	0.00012	0.00230	0.00000	0.00139	0.00508	0.00889	0.02	No
Selenium	0.00028	0.00002	ND	ND	ND	ND	0.0003	0.005	No
Silver	NR	0.00009	ND	ND	ND	ND	0.00009	0.005	No
Uranium	NR	0.00003	NR	NR	NR	NR	0.00003	0.002	No
Vanadium	ND	0.00001	ND	NR	NR	NR	0.00001	0.003	No
Zinc	0.01815	0.00060	0.00371	0.00001	0.00238	0.00874	0.03359	0.3	No
Total PCBs	0.00387	0.00000					0.00387	0.00002	Yes
PCB (Aroclor 1254)	0.00164						0.00164	0.00002	Yes
¹For an explanation of health guidelines and exposure calculations, refer to Appendix C.
Key: NR = not reported; ND = not detected; PCBs = polychlorinated biphenyls

Radioactive Contaminant	Fish	Game (meat)	Apples, Grapes	Other Fruit (Persimmons)	Nuts, Legumes	Green Vegetables	Yellow Vegetables¹	Tomatoes	Total Estimated Committed Effective Dose
Technetium 99	0.018 (1.8E-04)	0.009 (9.2E-05)	0.003 (2.7E-05)	0.006 (6.1E-05)	0.167 (1.67E-03)	0.001 (6.0E-06)	0.001 (1.1E-05)	0.002 (2.3E-05)	0.21 (2.1E-03)
Uranium 234	0.006 (6.3E-05)	0.016 (1.6E-04)	0.008 (8.4E-05)	0.000 (0.000)	0.002 (1.9E-05)	0.005 (4.5E-05)	0.004 (3.5E-05)	0.006 (6.2E-05)	0.05 (4.6E-04)
Uranium 235	0.002 (1.6E-05)	0.001 (1.1E-05)	0.001 (1.4E-05)	0.000 (0.000)	0.001 (1.1E-05)	0.001 (1.0E-05)	0.006 (6.0E-05)	0.004 (3.8E-05)	0.02 (1.6E-04)
Uranium 238	0.002 (1.5E-05)	0.023 (2.3E-04)	0.002 (2.2E-05)	0.000 (0.000)	0.000 (3.0E-06)	0.000 (2.0E-06)	0.010 (9.6E-05)	0.003 (2.5E-05)	0.04 (3.9E-04)
Thorium 230	0.008 (8.2E-05)	0.008 (7.5E-05)	0.002 (1.7E-05)	0.000 (0.000)	0.001 (1.3E-05)	0.003 (2.8E-05)	0.001 (1.2E-05)	0.009 (8.7E-05)	0.03 (3.1E-04)
Plutonium 239		0.010 (9.8E-05)		0.000 (0.000)				0.002 (1.9E-05)	0.01 (1.2E-04)
Americium 241		0.004 (4.4E-05)							0.00 (4.4E-05)
Neptunium 237		0.000 (2.0E-06)			0.001 (6.0E-06)	0.000 (4.0E-06)	0.000 (3.0E-06)	0.001 (1.2E-05)	0.00 (2.7E-05)
Strontium 90		0.029 (2.9E-04)							0.03 (2.9E-04)
Cesium 137		0.000 (1.0E-06)
Estimated annual committed effective dose	0.036 (3.6E-04)	0.100 (1.0E-03)	0.016 (1.6E-04)	0.006 (6.1E-05)	0.172 (1.7E-03)	0.010 (9.5E-05)	0.022 (2.2E-04)	0.027 (2.7E-04)	0.39 (3.9E-03)
Total estimated annual committed effective dose for all above radioactive contaminants in food crops is 0.39 millirems (or 3.9E-03 millisieverts)
¹ "Yellow vegetables," in this table, includes eggplant, mixed vegetables, soybeans, carrots, corn, and squash.

Major Source	Contaminants	Point of Exposure	Route of Exposure	Exposed Population	Period of Time	Maximum Estimated Exposure Doses
Plant operations and waste disposal activities that release contaminants to soil, surface water, and air that are transported to creeks and pond near the plant	Total PCBs Aroclor 1254	Fish from Little Bayou Creek	Ingestion	Children and adults who eat 20% of their fish intake from Little Bayou and Bayou creeks	Past, Current, and Potential Future Access to Little Bayou creek is partially restricted and fishing advisories are posted	Total PCBs Adults: 0.00215 mg/kg/d Children: 0.00387 mg/kg/d PCB--Aroclor 1254 Adults: 0.00092 mg/kg/d Children: 0.00164 mg/kg/d
	Radioactive contaminants	All biota in Tables 20A and 20B	Ingestion	Children and adults who eat 20% of their intake of fish, game, fruits and vegetables from areas near PGDP		Radioactive Contaminants (annual intake) Adults: 0.7 mrem (0.007 mSv) Children:0.4 mrem (0.004 mSv)
Key: mg/kg/d = milligrams of contaminant per kilogram of body weight per day; mrem = millirems; mSv = millisieverts

Magnitude	Average Repeat Time (in years)	Probability of occurrence in 15 years (%)	Probability of occurrence in 50 years (%)
6.3	70 +/- 15	40 - 63	86 - 97
7.6	254 +/- 60	5.4 - 8.7	19 - 29
8.3	550 +/- 125	0.3 - 1.0	2.7 - 4.0