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PUBLIC HEALTH ASSESSMENT

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


Surface Water

Background

Surface waters around PGDP have elevated concentrations of chemicals and radioactive materials as a result of process operations and past waste disposal activities. In this section, we evaluate these contaminants and the potential for human exposure.Surface waters around the PGDP site have elevated concentrations of chemical and radioactivecontaminants as a result of process operations and past waste disposal activities at the facility.Surface waters may also receive contaminants as a result of groundwater discharge to Bayou Creekand the Ohio River [87] and deposition of airborne particles [76]. Surface water monitoring datareflect total contaminant load. Surface water drainage from PGDP is either east or northeast to LittleBayou Creek or the North/South DiversionDitch, or west or northwest to Bayou Creek.The North/South Diversion Ditch has flowonly during periods of heavy rain and releasesfrom the plant. The ditch flows to thenorth/northeast and discharges into LittleBayou Creek. Bayou and Little Bayou creeksconverge about 3 miles (5 kilometers) north ofthe facility and discharge directly into theOhio River about a quarter mile (half akilometer) further downstream.

Surface water discharges from the PGDP site to Bayou and Little Bayou Creeks are regulated underKentucky Pollutant Discharge Elimination System (KPDES) permits. Surface water runoff from theplant into the North/South Diversion Ditch and from the landfills and the plant into Little Bayou andBayou Creeks are also monitored under KPDES permits. These permits specify allowablecontaminant concentrations in discharges and require DOE or the U.S. Enrichment Corporation tomonitor effluents and take corrective action if discharges exceed permitted limits.

ATSDR scientists reviewed data for 258 different off-site surface water monitoring stations thatPGDP sampled between 1987 and 2000. All stations included in this evaluation are outside thesecurity fence. Samples were analyzed for 511 different chemicals and radiological parameters [45].PGDP sampled a few monitoring stations as early as 1958 [86]. However, these samples wereanalyzed for only fluoride, nitrate, hexavalent chromium, uranium, and gross beta activity.Maximum concentrations of fluoride, nitrate, hexavalent chromium, uranium, and gross betaactivity in historical samples collected close to the site boundary in Bayou and Little Bayou Creekswere higher than in samples analyzed from 1987 to 2000 [68]. However, historical data are notdirectly comparable to more recent measurements, because there have been changes in sampling andanalytical techniques over time. Because process operations and waste disposal practices have alsochanged over time, current contaminant releases to surface waters are generally one to two orders ofmagnitude lower than historical releases.

Concentrations for most surface water contaminants are not evenly distributed; maximum valuesmay be two orders of magnitude higher than the next highest sample. The maximum concentrationsfor all surface water contaminants were obtained at one of two locations. For metals, the highestconcentrations are at several surface water stations in Bayou Creek adjacent to the southwestlandfill. Stations at the PGDP outfalls into Little Bayou Creek have the highest concentrations offluoride, nitrate, polychlorinated biphenyls (PCBs), trichloroethylene (TCE), and radioactivematerials.

According to samples collected upstream and downstream of the point where Bayou and LittleBayou Creeks discharge into the Ohio River, the river has several chemical contaminants that maybe related to PGDP, including chloride, fluoride, and sulfate. Maximum concentrations downstream,however, are barely above the concentrations upstream, and are much lower than levels found inBayou and Little Bayou Creeks [1]. Also, a different source may be responsible for these elevatedconcentrations of chloride, fluoride, and sulfate.

Contaminants of Concern

Seventeen chemicals and eleven radionuclides were detected in areas of potential exposure at levels that required additinal exposure analysis.ATSDR scientists used a series of screening techniques to select contaminants of concern forsurface water exposure pathways. The first phase of this screening involved determining ifmaximum off-site concentrations exceeded health-based comparison values for chemicals and ifmaximum radiation doses exceed 4 millirems per year (EPA's Drinking Water Standard forradioactive contaminants). Contaminants of concern for other exposure pathways were alsoevaluated if detections were above comparison values. Seventeen chemicals (14 metals, TCE,nitrate, and total PCBs) were detected in areas ofpotential exposure at levels requiring additionalexposure analysis. Eleven radionuclides areevaluated for potential exposure doses todetermine if they should be consideredcontaminants of concern.

The second phase of contaminant screening isbased on the calculation of potential exposure doses for each surface water contaminant.Concentrations of most surface water contaminants were log-normally distributed, meaning that afew samples had high concentrations while most of the samples had much lower concentrations.Consequently, the estimated exposure doses were calculated using the 67th percentile of theconcentration distribution. The exposure analyses, along with the detection ranges, the 67thpercentile concentrations, and the calculated exposure doses, for these contaminants are presented in Tables 11 and 12 in the following section.

Thallium is one of the seventeen chemical surface water contaminants and is the only one that hasestimated exposure doses that exceed health guidelines. Therefore, thallium is a contaminant ofconcern for the surface water pathway and will be discussed further in the following pathwayanalysis section and in the public health implications section of this report.

Di(ethylhexyl)phthalate is not considered a contaminant of concern. Although this chemical wasdetected in surface water samples, it is not directly used or stored at PGDP. It is a common additiveto plastic sample bottles, rubber gloves, and other plastic products. It was detected three times atdifferent stations with widely varying concentrations. Therefore, ATSDR scientists presumed thatdi(ethylhexyl)phthalate was introduced during the sampling process and is not a site-relatedcontaminant of concern for surface water.

For current concentrations of radioactive materials in the surface water we used the 67th percentilefor reasons described previously; however, we did not have as much data for past concentrations sowe used the annual average concentration at the sampling location that had maximum results. Also,there are important differences between current and past analyses of radioactive substances insurface water. Measured concentrations changed over time, but so did the methods of analysis usedand the list of radioactive materials being measured. Historical analyses for radioactive materialsincluded total uranium, gross alpha, and gross beta activity. In these analyses, the highest averageannual total uranium concentration was 474 picocuries per liter (pCi/L), measured in samplescollected from Bayou Creek in 1960. The highest average annual gross beta activity was 21,700pCi/L (Little Bayou Creek, 1960) [88]. Most of this beta activity was attributed to technetium 99(Tc-99). Therefore, ATSDR scientists used the maximum annual average concentrations foruranium and Tc-99 (gross beta) to estimate past exposure doses (annual committed effective doses)for children and adults. These doses are presented in Table 12 in the following section.

By the 1980s, maximum uranium concentrations had decreased to levels that were less than 1% to5% of levels reported in 1960. Other radioactive contaminants (strontium 90, neptunium 237,plutonium 239, and thorium 230) were quantified in the 1987-1996 analyses. ATSDR includedthese other radioactive contaminants in the estimated current exposure doses (annual committedeffective doses) for children and adults. These doses are also presented in Table 12 in the followingsection.

Surface Water Exposure Pathways

Because contaminants are present in Little Bayou Creek and Bayou Creek, potential human exposure pathways were identified for past, current, and future exposure to contaminated off-site surface water. The highest concentrations are in the creek adjacent to the southwest landfill and the outfalls into Little Bayou Creek, including the North-South Division Ditch.The greatest potential for human exposure tocontaminated off-site surface water has been inLittle Bayou Creek, Bayou Creek, and theOhio River downstream of Bayou Creek.Persons may fish, wade, and play in the creeks.In addition, there are noted community healthconcerns about potential human exposures.Because contaminants are present in the creeksand humans may access these areas, ATSDRscientists identified potential exposurepathways for past, current, and future exposureto contaminants in surface water. Contaminantsof concern in these exposure pathways will be evaluated further in the public health implications section of this report.

As stated above, the highest concentrations of all surface water contaminants occur at one of twolocations: either within the WKWMA property directly adjacent to the southwest landfill or in DOEbuffer property at surface and storm water outfalls into Little Bayou Creek. (This includes theNorth-South Diversion Ditch.) Although exposure is possible in these areas, ongoing monthlyingestion of surface water is unlikely. Also, the 67th percentile concentrations of off-site contaminantlevels is much more realistic for calculating potential surface water exposures around PGDP.

Exposure doses are estimated assuming incidental contact and ingestion, because surface water inthis area is not used to supply drinking water. For chemical contaminants above the health-basedcomparison values, we assumed ingestion of 0.5 liters of water per exposure and one exposure permonth for 12 months per year. We estimated exposure doses for a child (1 to 6 years old) and anadult, assuming incidental ingestion of surface water contaminated at the 67th percentile of off-siteconcentrations. For volatile organic compounds, dermal (skin) contact may contribute a dose up to30% as large as the ingestion dose [58]. TCE was the only volatile organic compound detected insurface water off site. Therefore, we assumed that dermal contact contributed an additional 30% tothe estimated ingestion dose for TCE. The estimated exposure doses for current exposure to mostchemical contaminants and past exposure to hexavalent chromium, fluoride, and nitrate are shownin Table 11 (using pre-1987 annual average values). The estimated current and past exposures toradioactive contaminants are shown in Table 12. It was not possible to estimate past exposure dosesto most chemicals and radioactive materials, because historical measurements are lacking.

Health guidelines provide a basis for evaluating exposure doses estimated from contaminantconcentrations in soil, air, water, and food. Exposure doses depend on the characteristics of thepeople who might be exposed and the length of their exposure. The health guidelines are describedin Appendix C. Most of the health guidelines were derived for chronic exposure--that is, exposurelasting more than 364 consecutive days. By contrast, human exposure to off-site contaminatedsurface water is likely to have occurred infrequently throughout the year and possibly not at allduring winter months. According to local residents, there is very little swimming, wading, or otherhuman activity in Bayou and Little Bayou Creeks. All of Little Bayou Creek is in DOE orTennessee Valley Authority property, except for a small area that borders private property to the eastof the plant. According to the Kentucky Radiation Control Program, Little Bayou Creek has been restricted and posted at access points since July 19, 1993.

Table 11.

Estimated exposure doses for chemical contaminants in off-site surface water at PGDP and health guidelines
Chemical
Contaminant
Contaminant Range (and 67th percentile) in g/L Estimated Exposure Dose for Children (mg/kg/day)1 Estimated Exposure Dose for Adults
(mg/kg/day)1
Oral Health Guideline in mg/kg/day and Source1 Estimated Exposure Dose Greater Than Health Guideline?
Antimony

10-50 (42)

0.000084 0.000013 0.0004 (Chronic RfD) No
Arsenic 6-90 (38) 0.000076 0.000011 0.0003 (Chronic MRL) No
Beryllium 0-150 (75) 0.00015 0.000023 0.002 (Chronic RfD) No
Cadmium 0-90 (32) 0.000064 0.00001 0.0002 (Chronic MRL) No
Chromium 4-820 (210) 0.00042 0.000063 1.5 (Oral RfD) No
Chromium, hexavalent 20-7,8802
(1,626)
0.0033 0.00049 0.003 (ATSDR Interim Oral Intake) No
Fluoride (Fluorine) 100-35,0002
(1,047)
0.0021 0.00031 0.05 (Chronic MRL) No
Lead 2-12,200 (1,945) 0.0039 0.00058 0.0203 No
Manganese 8-187,000
(22,447)
0.045 0.0067 0.07 (ATSDR Interim Guidance Value) No
Nickel 5-1,350 (320) 0.00064 0.000096 0.02 (Chronic RfD) No
Nitrate 150-900,0002
(2,492)
0.005 0.00075 1.6 (Chronic RfD) No
Total PCBs 1-42 (4.5) 0.00001 0.000002 0.00002 (Chronic MRL for Aroclor 1254)4 No
Sulfate 3,800-1,680,000
(108,184)
0.22 0.032 14.295 No
Thallium 16-5,260 (417) 0.00083 0.00013 0.00008 (Chronic RfD) Yes
Trichloroethylene 1-51 (5) 0.00001 0.000002 0.2 (Acute MRL) No
Uranium 1-3,000 (74) 0.00015 0.000022 0.002 (Int./Chronic MRL) No
Vanadium 2-1,430 (156) 0.00031 0.000047 0.003 (Int. MRL) No
1 For an explanation of health guidelines and of how we calculated exposure doses, refer to Appendix C.
2 These concentrations are maximum annual averages from historical annual environmental reports [68]. The other concentrations are from the 1987-2000 electronic data and reports [45].
3 Based on lowest-observed-adverse-effect level (acute) from ATSDR, 1997 [89].
4 This MRL is based on Aroclor 1254, not total polychlorinated biphenyls. This provides a conservative evaluation.
5 Based on EPA's MCLG and equivalent exposure for a 70-kg adult ingesting 2 liters per day.
Key: mg/kg/day = milligrams of contaminant per kilogram of body weight per day; g/L = micrograms per liter


Table 12.

Past and current maximum estimated exposure doses (annual committed effective doses) for radioactive contaminants in surface water [60]
Radioactive Contaminant Past Maximum Concentration in pCi/L (and in Bq/L) Current Concentration Range and 67th Percentile in pCi/L (and Bq/L) Maximum Annual Estimated Committed Effective Dose for Child in mrem (and mSv) Maximum Annual Estimated Committed Effective Dose for Adult in mrem (and mSv)
Past Current Past Current
Americium 241

------

0.05-17.1 (0-0.63)
13.7 (0.507)
------ 0.08
(8.2E-04)
------ 0.06
(6.1E-04)
Neptunium 237 ------ 0.04-13.6 (0-0.50)
0.8 (0.030)
------ 0.00
(2.5E-05)
------ 0.00
(2.0E-05)
Plutonium 238 ------ 0.5-3.2 (0.02-0.12)
2.7 (0.100)
------ 0.02
(1.9E-04)
------ 0.01
(1.4E-04)
Plutonium 239 ------ 0.01-2.7 (0-0.10)
0.3 (0.011)
------ 0.00
(2.2E-05)
------ 0.00
(1.6E-05)
Strontium 90 ------ 6.1-131.3 (0.23-4.86)
64 (2.37)
------ 0.07
(6.7E-04)
------ 0.04
(4.0E-04)
Technetium 99 21,700 (803.7)2 1-4,000 (0.04-148.1)
61 (2.259)
1.11
(1.11E-02)
0.00
(3.1E-05)
0.309
(3.1E-03)
0.00
(8.7E-06)
Thorium 230

------

0.002-6.0 (0-0.22)
1.4 (0.052)
------ 0.01
(9.7E-05)
------ 0.01
(6.6E-05)
Uranium, total1

474 (17.56)2

0.06- 9.5 (0-0.35)
3.4 (0.126)
0.88
(8.8E-03)
  0.50
(5.0E-03)
 
Uranium 234

------

0.01-119 (0-4.41)
7.5 (0.278)
------ 0.01
(1.5E-04)
------ 0.01
(8.2E-05)
Uranium 235

------

0.01-2.34 (0-0.09)
0.6 (0.022)
------ 0.01
(8.5E-05)
------ 0.00
(4.7E-05)
Uranium 238 ------ 0.33-194 (0.01-7.19)
16.4 (0.607)
------ 0.01
(8.0E-05)
------  
Total committed effective dose ------ ------ 1.99 (0.02)3 0.21 (0.00) 0.81 (0.01)3 0.13 (0.00)
1 Total uranium = uranium-234, uranium-235, and uranium-238 (only used for past exposure calculations).
2 These concentrations are maximum annual averages from historical annual environmental reports [68]. The other concentrations are from the 1987-2000 electronic data and reports [45].
3 Past total committed effective doses do not include potential exposure to several radionuclides, because there are not enough historical data.
Key: pCi/L = picocuries per liter; Bq/L = becquerels per liter; mSv = millisieverts; mrem = millirems

Current and Past Exposure

Several chemical and radioactive contaminants have been detected in surface water samples takenfrom Bayou Creek, Little Bayou Creek, and the portion of the Ohio River downstream of BayouCreek. Only one chemical contaminant, thallium, was selected as a contaminant of concern forsurface water. The highest concentrations of thallium are reported for Bayou Creek and itstributaries near the inactive southwest landfill. Concentrations of thallium are also elevated in LittleBayou Creek east of the plant. ATSDR scientists cannot determine with certainty how long thestreams may have been contaminated with thallium, because samples were not analyzed for thalliumuntil 1987. Because thallium may have been present in off-site surface water prior to 1987, thalliumis a contaminant of concern for past and current exposure via potential exposure pathways foroff-site surface water (as shown in Table 13) and will be discussed in the public health implications section of this report.

Radioactive contaminants were present at low levels in samples taken from Little Bayou and Bayoucreeks. Because the annual total committed effective doses are less than 4 millirems (0.04millisieverts) for current exposures, radioactive contaminants are not contaminants of concern forcurrent exposure to surface water. Lack of data for historical concentrations of radioactivematerials other than Tc-99 and the uranium isotopes makes it difficult to determine pastexposures to all radionuclides in surface waters. It is possible that, during a past release fromthe site, a person exposed to the surface waters could have received a dose in excess of 4millirems. Therefore, radioactive materials are considered contaminants of concern for pastexposures via potential exposure pathways for off-site surface water and will be discussed in thepublic health implications section of this report.

Potential Future Exposure

With partial restrictions on access to Little Bayou Creek, permitting discharges to off-site surfacewater, and remedial activities to remove sources of contamination, future exposures to surface watercontaminants should either not occur or be much lower than current exposures. Therefore, ATSDRscientists did not identify any potential future exposure pathways for surface water. However, ifnew processes are initiated at the site or new sources of contamination are identified, futureexposures should be addressed at that time.

After evaluating potential exposure to surface water for children and adults, only thallium is identified as a contaminant of concern for this exposure pathway. However, due to uncertainty about radioactive contaminant concentrations in the past, both radioactive materials and thallium are discussed further in the public health implications section of this report.

Table 13.

Summary of potential exposure pathways for off-site surface water contaminants of concern
Major Sources Contaminants Point of Exposure Route of Exposure Exposed Population Period of Time Maximum Estimated Exposure Doses
Process operations discharge, surface water runoff, leaching from past waste disposal activities, groundwater discharge, airborne deposition Thallium During wading or immersion in Little Bayou or Bayou Creeks Incidental ingestion and dermal contact Children playing in the creeks once per month, and adults fishing and wading in the creeks once per month Past and current Thallium (mg/kg/d)
Children: 0.00083
Adult: 0.00013
Total uranium
Technetium 99
Americium 241
Strontium 90
Neptunium 237
Plutonium 238
Plutonium 239
Thorium 230
Past
(before 1987)
Radiation exposure:
uncertain (however, estimated committed effective doses were > 4 mrem but < 200 mrem for annual intake in both scenarios)
Key: mg/kg/d = milligrams of contaminant per kilogram of body weight per day; mrem = millirems

Soil and Sediment

Background

Activities at PGDP have contaminated surface soil and sediment. In this section, we evaluate this contamination and the potential for human exposure.Process operations and waste disposalactivities at PGDP have contaminated soil andsediment. Off-site surface soil has becomecontaminated mainly as a result of releasesfrom disposed waste material and deposition ofairborne releases. Surface soil concentrationsare highest in the predominant downwinddirections from the site and in soils near the creek and ditches as a result of leaching from landfillsand occasional flooding of the creeks and ditches. Sediment in nearby streams has becomecontaminated as a result of surface water discharges and surface runoff from the site. Deposition ofairborne materials also introduces contaminants to streams and ponds, where they are adsorbed tosediments.

Soil and sediment data evaluated were obtained via electronic transfer from the PGDPenvironmental database [45], the Kentucky Department for Environmental Protection (HazardousWaste Branch) and the Kentucky Department for Public Health (Radiological Health and ToxicAgents Branch). The cumulative data set consists of 292,062 chemical and radiologicalmeasurements for 457 analytes from 1,737 locations. Data were available for five different sampletypes and depth profiles:

  • Sediment.

  • Soil at unspecified depth.

  • Subsurface soil more than 12 inches (30 centimeters) deep.

  • Surface soil less than or at 12 inches deep but more than 3 inches deep (that is, from 8 centimeters to 30 centimeters).

  • Top soil less than or at 3 inches (8 centimeters) deep.

Because chronic human exposure to subsurface material is very unlikely, ATSDR evaluated onlysurface and top soil samples (including unspecified depth samples), as well as sediment samples.Sample station names did not designate whether any off-site samples were collected on residentialproperties. If the stations appeared to be located near residential properties, the residential propertieswere assumed to have similar soil concentrations. Samples in the electronic data set were collectedand analyzed for 1987 through 2000. Additional soil and sediment data, available from annualenvironmental monitoring reports, were used to corroborate contaminant distributions. A limited soilsampling program began in 1971; however, few samples were collected and were analyzed only foruranium.

Off-site sample locations were not uniformly spaced. They were too far apart to determine whethercontaminant distributions followed a regular pattern based on transport and fate (e.g., airbornedispersal) processes. For example, maximum concentrations of technetium 99 and neptunium 237were found to the north of the fenced area and near the edge of the buffer zone; maximumconcentrations of metals, uranium isotopes, thorium 230, and cesium 137 were found west andsouthwest of the site; and maximum concentrations of most of the radioactive contaminants insediment were found in drainage ditches and in Little Bayou Creek. Also, most soil samplingstations have not had multiple sampling over time. Consequently, it is not possible to evaluatehistorical trends of soil contamination at PGDP. This evaluation will assume that if PGDPcontaminants have been detected at a soil sampling location, that location has been contaminatedsince the beginning of PGDP operations. As with surface water, concentrations of most soil andsediment contaminants are not evenly distributed.

Contaminants of Concern

Thirteen chemicals and twelve radionuclides were detected in areas of potential exposure at levels that required additional exposure analysis.ATSDR scientists used a screening technique to select contaminants of concern for soil andsediment exposure pathways. This screening involved determining if maximum concentrations ofthese contaminants in areas of potential humanexposure exceeded health-based comparison valuesfor chemicals and if maximum radiation dosesexceeded 25 millirems per year (mrem/year) forradionuclides. Thirteen chemical contaminants andtwelve radionuclides were consistently detected inareas of potential exposure at concentrationsrequiring additional exposure analyses.

Most of the contaminants remaining after the first phase of screening are naturally occurring metalswith concentrations that may have been elevated above background levels by process operations orwaste disposal activities. In addition, polychlorinated biphenyls (PCBs or Aroclors) have beendetected above comparison levels. The PCBs have been analyzed as both individual species (Aroclor1016, Aroclor 1242, Aroclor 1254, etc.) and as total PCBs. Only total PCBs will be evaluatedfurther.

Several detected contaminants are not considered further. Metallic mercury, 1,2-dichloroethene (cisand trans), and ammonia each had only one sample above comparison values. These single highvalues were not repeated in other analyses indicating that the high values are sampling or analyticalanomalies, or that the spatial extent of the contaminants is so limited that significant exposure is notpossible. Silver was detected at several on-site sediment or soil samples for which no chronic (long-term) community exposure is possible. Off-site detections of silver were below levels of healthconcern. Trichloroethylene, a contaminant of concern for the groundwater exposure pathway, wasdetected in five samples. However, those detections were at on-site stations and below levels ofhealth concern. Chromium is not evaluated further, because concentrations are below health-basedcomparison values for trivalent chromium. Although the valence of the chromium soil samples is notspecified, other studies have shown that virtually all of the soil chromium is in the trivalent form, notthe more toxic hexavalent form [76,79].

Most of the contaminants evaluated further have higher concentrations on site than off site. Thismeans that site activities may be responsible for contaminant distributions. Arsenic, lead, and nickelhave higher off-site concentrations, which suggests that PGDP activities may not be responsible forthe distributions of these contaminants. It is also possible that several of the soil and sedimentcontaminants are at background levels--that is, that they do not represent site-related contamination.Prior use of the PGDP site by the Kentucky Ordnance Works could also contribute metalscontamination. Because arsenic, lead, and nickel exceed health-based comparison values, thefollowing exposure analyses will identify their potential exposure pathways and estimated exposuredoses.

Soil and Sediment Exposure Pathways

We investigated ways in which people could be exposed to soil and sediment contamination outside the PGDP security fence. We used two possible scenarios: (1) WKWMA workers and visitors may be exposed in the buffer zone and adjacent WKWMA property, and (2) people living next to PGDP may be exposed.Contaminated soils and sediments are presentboth inside and outside of the PGDP securityfence. The most significant soil contaminationis within the fence but has little potential forpublic exposure. However, soil contaminantswith concentrations above health comparisonvalues are present within the unsecured bufferarea maintained as part of the WesternKentucky Wildlife Management Area(WKWMA) and on private land outside the buffer area. The most contaminated sediments aresimilarly located within the access-restricted drainage ditches and Little Bayou, but contaminatedsediments are also present within the open access areas of Bayou, nearby ponds, and private lands.

The distribution of land uses surrounding PGDP presents two scenarios by which the public may beexposed to soil and sediment contaminants. Scenario 1 covers WKWMA workers and visitors, whomay be exposed to soil and sediment contaminants in the buffer zone and adjacent WKWMAproperty. Scenario 2 covers people living adjacent to PGDP. As with surface water, concentrationsof most soil and sediment contaminants are log-normally distributed, meaning that a few sampleshad high concentrations while most of the samples had much lower concentrations [90].Consequently, the estimated exposure doses were calculated using the 67th percentile of theconcentration distribution. The following sections present the exposure attributes, contaminantconcentrations, and estimated exposure doses that are specific to each of those scenarios. Thefollowing scenarios assume that soils and sediments became contaminated shortly after thebeginning of PGDP operations and that the exposure pathways are complete in the past, present,and future. The detection ranges, the 67th percentile concentrations and the calculated exposure doses are presented in Tables 14.A, 14.B, 15.A, and 15.B.

Scenario 1--WKWMA Workers and Visitors

WKWMA workers involved with maintenance of the buffer zone property have a high potential forcontact with contaminated soil. This scenario also includes visitors to WKWMA, although theywould be exposed less often than WKWMA workers and receive a commensurately lower exposuredose. Some of the WKWMA workers are also residents in the immediate area so their potentialexposures were both as WKWMA workers and as adult residents.

ATSDR scientists assumed that workers could be exposed to top soil, surface soil, or soil atunspecified depth and would spend approximately 8 hours/day for 1.5 days/week (i.e., 30% of theirwork week) in contaminated buffer zone areas. We also assumed that the same WKWMA workerswere exposed to contaminated sediment for 0.75 day/week (15% of the work week). We assumedthat these soil and sediment exposures went on for 50 weeks/year for 10 years, which is anapproximate maximum period of employment at the WKWMA. Soil contaminant concentrationsderived for this scenario were for buffer zone soil samples. Sediment contaminant concentrationswere derived from all sediment samples taken outside the security fence.

Exposure was assumed to occur via direct (dermal) contact and ingestion for chemicalcontaminants and via ingestion and external exposure for radioactive contaminants. For ingestion,we assumed an ingestion rate of 200 milligrams (mg) of soil per day (four times the daily averageadult rate [24]) and 100 mg of sediment per day (two times the average adult rate). We assumedthat workers were adult men and women. Table 14A shows the estimated exposure doses forchemical contaminants (along with additional assumptions we made in calculating them). Table14B shows estimated exposure doses (annual committed effective doses) for radioactivecontaminants in this scenario. Table 14B does not show estimated external exposure to radioactivecontaminants. (The estimated external exposure from surface and/or top soil would addapproximately 8 mrem/year for this scenario [91].)

For this scenario and for adult workers potentially exposed as WKWMA workers and as residents,no chemical exposure doses exceed the health guidelines, and the estimated total annual committedeffective dose for radioactive materials does not exceed 25 mrem (0.25 millisieverts, or mSv).Although this exposure pathway is presumed complete for past, current, and potential futureexposures, the estimated exposure doses are not expected to produce adverse health effects.

Table 14A.

Estimated exposure doses to WKWMA workers and visitors for chemical contaminants in buffer zone soil and sediment (Scenario 1)
Chemical Soil Range and 67th Percentile
(mg/kg)
Sediment range and 67th Percentile
(mg/kg)
Combined Soil-Sediment Exposure Dose1 (mg/kg/day) Health Guideline (mg/kg/day) (source)1 Does Est. Exposure Dose Exceed Health Guideline?
Antimony 1-18
2.7
0.5-1,320
11.3
0.0000090.0004 (chronic RfD)No
Arsenic 1-38
8.3
0.7-30
7.6
0.000020.0003 (chronic MRL)No
Barium 7-360
102
11.6-1,160
134
0.00020.07 (chronic RfD)No
Beryllium 1-17
4.4
0.2-8.2
1.0
0.0000060.002 (chronic RfD)No
Cadmium 1-4
1.5
0.1-21
1.3
0.0000020.0002 (chronic MRL) No
Fluoride 200-310
301.6
170-210
182
0.00050.05 (chronic MRL)No
Lead 0.1-705
46
6-635
51.1
0.000090.022No
Manganese 34-4,020
612
33-2,830
587
0.0010.07 (ATSDR InterimGuideline)No
Nickel 2-461
26.8
2.5-540
29
0.000050.02 (chronic RfD) No
Uranium 0.04-1,850
43.1
0.3-13,070
85
0.000040.002 (chronic MRL)No
Vanadium 4-460
50.4
6.5-460
47.2
0.0000070.003 (intermediateMRL)No
Polychlorinatedbiphenyls (PCBs) 0.07-2.4
0.8
0.01-58.7
1.4
0.0000020.00002 (chronic MRLfor Aroclor 1254)No
1 For an explanation of health guidelines, and of how we calculated exposure doses, refer to Appendix C.
2 Based on the acute lowest-observed-adverse-effect level from ATSDR, 1997 [89].
Key: mg/kg = milligrams per kilogram; mg/kg/day = milligrams of contaminant per kilogram of body weight per day; RfD = EPA's reference dose; MRL = ATSDR's minimal risk level


Table 14B.

Estimated exposure doses (annual committed effective doses) to WKWMA workers and visitors for radioactive contaminants in buffer zone soil and sediment (Scenario 1) [60]
Radioactive Contaminant Soil Range and 67th Percentile in pCi/g (Bq/g)1 Sediment Range and 67th Percentile in pCi/g (Bq/g) Combined Exposure Dose (annual committed effective dose) in mrem (mSv)2
Americium 241 0.09-13 (0.003-0.48)
6.2 (0.23)
0.01-9.4 (0-0.35)
1.1 (0.04)
0.072 (7.2E-04)
Cesium 137 0.03-160 (0.001-5.93)
6.5 (0.24)
0.01-52.3 (0-1.94)
0.6 (0.02)
0.005 (4.8E-05)
Neptunium 237 0.01-22 (0-0.81)
2.3 (0.09)
0.01-63 (0-2.33)
0.5 (0.02)
0.016 (1.6E-04)
Plutonium 238 0.03-0.62 (0.001- 0.02)
0.2 (0.01)
0.001-0.6 (0-0.02)
0.1 (0.004)
0.004 (3.8E-05)
Plutonium 239 0.01-31 (0-1.15)
1.2 (0.04)
0.01-53 (0-1.96)
0.5 (0.02)
0.017 (1.7E-04)
Potassium 40 0.44-74 (0.02-2.74)
11.8 (0.44)
2.59-15.7 (0.10-0.58)
3.8 (0.14)
0.004 (4.4E-05)
Technetium 99 0.00-2200 (0-81.48)
145.7 (5.40)
0.04-3,900 (0-144.4)
18 (0.67)
0.005 (5.3E-05)
Thorium 230 0.00-110 (0-4.07)
12.6 (0.47)
0.01-1,300 (0-48.15)
5.2 (0.19)
0.163 (1.6E-03)
Thorium 234 0.97-1,330 (0.04-49.26)
93 (3.44)
0.6-3,263 (0.02-120.85)
22.3 (0.83)
0.019 (1.9E-04)
Uranium 233/234,or Uranium 234 0.4-20,0003 (0.015-740.7)
21.4 (0.79)
0.05-445 (0-16.48)
5.6 (0.21)
0.062 (6.2E-04)
Uranium 235 0.00-1100 (0-40.74)
1.8 (0.07)
0.01-57 (0-2.11)
0.6 (0.02)
0.005 (5.3E-05)
Uranium 238 0.07-20,0003 (0-740.74)
93.5 (3.46)
0.08-720 (0-26.67)
9.7 (0.36)
0.24 (2.4E-03)

Estimated Total Annual Committed Effective Dose: 0.61 (6.1E-03)

1 The concentration range includes soil sample results from soils up to and including 1 foot (30 centimeters deep), as well as at unspecified depths.
2 In calculating exposure doses, we assumed 200 mg/day soil ingestion for 1.5 days/week and 100 mg/day sediment ingestion for 0.75 days/week for 50 weeks per year. Dose conversion factors from ICRP 72 were used [60]. External exposure (about 8 mrem/y) was not added in this table.
3 Unspecified-depth sample (actually a subsurface sample) near or at the southwest landfill.
Key: pCi/g = picocuries per gram; Bq/g = becquerels per gram; mSv/y = millisieverts per year; mrem/y = millirems per year;mg/day = milligrams of soil per day

Scenario 2--Residents

For this scenario, we used soil and sediment contaminant concentrations outside the buffer areawhich, in general, are much lower than on-site concentrations. On the other hand, potential exposurein a residential setting is likely to occur at a much greater frequency than the exposure described inthe previous scenario. The 67th percentile soil contaminant concentrations (rationale on page 61)were calculated for all soil sampling locations outside the buffer zone. (Soil sampling nomenclaturedid not designate whether the samples were taken on residential properties.) Also, ATSDR assumedpeople would be exposed to chemical contaminants via dermal contact and ingestion and to radioactive contaminants via ingestion only.

For children, we assumed a 1 to 6 year old child weighing 13 kilograms (kg) would consume soil ata rate of 200 mg per day while playing. Young children are more likely to play in creekssurrounding PGDP, so exposures to sediment were combined with residential soil exposures.Sediment exposures were assumed to occur for 1 day per month, with 100 mg of sediment ingestedin each event. The scenario parallels the surface water exposure pathway evaluation, becauseexposure to contaminated surface water and sediment is assumed to occur at the same time.

Some children exhibit pica behavior, a craving for unnatural food like soil and sediment. The degreeof pica behavior varies in the population and is influenced by nutritional status and quality of careand supervision [24]. Children less than 3 years old are most likely to exhibit this behavior.According to 1990 Census data for areas surrounding the PGDP facility, there were 24 childrenaged 1 to 6 living within 1 mile of the site security fence (as discussed in Appendix A). Therefore,we assumed that a child showing pica behavior, weighing 10 kg and ingesting 2,000 mg of soil perday could live in the area. [92].

For adults, we assumed that a 70-kg adult incidentally ingests 50 mg of soil per day [24].

For all persons, we assumed 5.6 days of soil exposure a week for 52 weeks a year, or a total of 292days a year. For children, we assumed an exposure duration of 6 years; for adults, we assumed anexposure duration of 30 years, because more than 15% of households surrounding the PGDP facilityhad residents who lived in the area for more than 30 years (as described in Appendix A). Theseassumptions are conservative and protective since such exposures are very unlikely. Table 15A shows the estimated exposure doses for chemical contaminants. Table 15B shows estimatedexposure doses (annual committed effective doses) for radioactive contaminants.

Table 15A.

Estimated exposure doses to residents for chemical contaminants in off-site soil (Scenario 2)
Chemical Soil Concentration Range in mg/kg Soil 67th %
Concentration in mg/kg
Estimated Exposure Dose in mg/kg/day1 Health Guideline in mg/kg/day
(source)1
Does Est. Exposure Dose Exceed Health Guideline?
Adult Soil Child Soil and Sediment2 Pica Child Soil
Antimony 1-50 6.1 0.000009 0.00003 0.001 0.0004 (chronic RfD) Yes, for pica child
Arsenic 1-38 10.6 0.00002 0.0001 0.002 0.0003 (chronic MRL) Yes, for pica child
Barium 7-367 153 0.0003 0.001 0.02 0.07 (chronic RfD) No
Beryllium 1-29 4.8 0.00001 0.00005 0.0008 0.002 (chronic RfD) No
Cadmium 0.03-42 1.2 0.000002 0.000005 0.0002 0.0002 (chronic MRL) No
Fluoride 2.2-310 38.2 0.00008 0.0004 0.006 0.05 (chronic MRL) No
Lead 1-1,0103 45.4 0.00008 0.0003 0.007 0.024 No
Manganese 34-4,020 817 0.001 0.003 0.10 0.07 (ATSDR Interim Guideline) Yes, for pica child
Nickel 2-17,600 33 0.00005 0.0001 0.005 0.02 (chronic RfD) No
Uranium 2.1-346 20.1 0.00005 0.0001 0.00016 0.002 (chronic MRL) No
Vanadium 0.01- 300 35.5 0.00005 0.0001 0.006 0.003 (inter. MRL) Yes, for pica child
Polychlorinated biphenyls (PCBs) 0-4.7 0.8 0.000002 0.000008 0.00001 0.00002 (chronic MRL for Aroclor 1254) No
1 For an explanation of health guidelines, and of how we calculated exposure doses, refer to Appendix C.
2 Sediment values listed in Table 14A.
3 Maximum lead value is at unspecified depth and only used for screening.
4 Based on the acute lowest-observed-adverse-effect level from ATSDR, 1997 [89].
Key: mg/kg = milligrams per kilogram; mg/kg/day = milligrams of contaminant per kilogram of body weight per day


Table 15B.

Estimated exposure doses (annual committed effective doses) to residents for radioactive contaminants in off-site soil (Scenario 2) [60]
Radioactive Contaminant Soil Concentration Range in pCi/g (Bq/g)1 Soil 67th Percentile Concentration in pCi/g (Bq/g) Estimated Exposure Dose (annual committed effective dose) in mrem (mSv)2
Adult Soil Child Soil and Sediment3 Pica Child Soil
Americium 241 0.03-1.5 (0.001-0.056) 0.8 (0.030) 0.009 (8.8E-05) 0.049 (4.9E-04) 0.648 (6.5E-03)
Cesium 137 0.03-11.1 (0.001-0.411) 0.5 (0.019) 0.000 (3.6E-06) 0.001 (1.1E-05) 0.013 (1.3E-04)
Neptunium 237 0.00-52.6 (0-1.948) 0.3 (0.011) 0.002 (1.8E-05) 0.009 (9.3E-05) 0.134 (1.3E-03)
Plutonium 238 0.03-0.06(0.001-0.002) 0.03 (0.001) 0.000 (3.4E-06) 0.002 (1.9E-05) 0.023 (2.3E-04)
Plutonium 239 0.00-31.0 (0-1.148) 0.43 (0.016) 0.006 (5.8E-05) 0.010 (9.6E-05) 0.392 (3.9E-03)
Potassium 40 0.44-18.6 (0.016-0.689) 4.8 (0.178) 0.002 (1.6E-05) 0.022 (2.2E-04) 0.437 (4.4E-03)
Technetium 99 0.0-4,840 (0-179.26) 146 (5.41) 0.005 (5.1E-05) 0.073 (7.3E-04) 1.517 (1.5E-02)
Thorium 230 0.00-34.8 (0-1.289) 1.4 (0.052) 0.016 (1.6E-04) 0.101 (1.0E-03) 1.245 (1.2E-02)
Thorium 234 0.97-136 (0.036-5.037) 14.4 (0.533) 0.003 (2.6E-05) 0.042 (4.2E-04) 0.778 (7.8E-03)
Uranium 234 0.12-102 (0-3.778) 8.1 (0.300) 0.021 (2.1E-04) 0.156 (1.6E-03) 2.278 (2.3E-02)
Uranium 235 0.00-2.2 (0-0.081) 0.24 (0.009) 0.001 (6.2E-06) 0.005 (4.7E-05) 0.068 (6.8E-04)
Uranium 238 0.23-86 (0.01-3.185) 7.3 (0.270) 0.018 (1.8E-04) 0.130 (1.3E-03) 1.892 (1.9E-02)

Estimated Total Annual Committed Effective Doses

0.083 (8.3E-04)

0.600 (6.0E-03)

9.425 (9.4E-02)

1 The concentration range includes soil sample results from soils at less than or equal to 1 foot (30 centimeters) deep or unspecified depths.
2 For explanation of exposure dose calculations, refer to Appendix C.
3 Sediment values listed in Table 14B.
Key: pCi/g = picocuries per gram; Bq/g = becquerels per gram; mrem/y = millirems per year; mSv/y = millisieverts per year; mg = milligrams

For this scenario, the estimated total annual committed effective dose for radioactive materials doesnot exceed 25 mrem (0.25 mSv); therefore, we expect no adverse health effects from exposure toradioactive materials for residents. The estimated chemical exposure doses for children with picabehavior exceed the health guidelines for antimony, arsenic, manganese, and vanadium. Thesechemicals and their estimated exposure doses will be discussed further in the public health implications section of this report.

The soil exposure pathway is considered a potential exposure pathway for children with picabehavior, since the soil concentrations may or may not be on residential property and there may ormay not be children in the area demonstrating pica behavior. The potential exposure pathway is summarized in Table 16.

Table 16.

Summary of potential exposure pathways for contaminants of concern in off-site soil and sediment
Major Sources Contaminants Point of Exposure Route of Exposure Exposed Population Period of Time Maximum Estimated Exposure1
Waste disposal activities

Airborne particle deposition

Deposition from surface waterdischarge and runoff

Background and/or prior site activities(Kentucky Ordnance Works)

Antimony
Arsenic
Manganese
Vanadium
Off site; assumed samples taken on or near residential properties Ingestion
Dermal
Children with pica behavior only (residents) Past, current, and potential future Child with pica behavior only:
0.001 mg/kg/d (antimony)
0.002 mg/kg/d (arsenic)
0.10 mg/kg/d (manganese)
0.006 mg/kg/d (vanadium)
1 For an explanation of how we calculated exposure doses, refer to Appendix C.
Key: mg/kg/d = milligrams of contaminant per kilogram of body weight per day (exposure unit for chemicals)

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