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A. On-Site Contamination

Environmental monitoring locations for the SLAPS, HISS, and FUTURA areas are shown in Figures 5 and 6. Results of on-site sampling performed by the NRC, ORNL, and a DOE contractor found significant levels of radioactive materials in the groundwater, soils, and air. The contaminants detected were U-238, U-nat, Th-230 and Th-232, Ra-226, and radon (isotope not specified). The levels detected were in excess of the regional isotope background (bkg) values for the St. Louis area as determined by the DOE. Although there is no surface water at the NPL site that could be contaminated, Coldwater Creek forms a boundary of the site (Figure 1) and contaminated surface runoff has entered the creek (Mitre, 1988).


Monitoring wells were located along the periphery of the site. Sampling results of these on-site groundwater monitoring locations at the SLAPS from 1981 to 1982 showed elevated levels of U-238. The yearly average during this time was approximately 439 picocuries per liter (pCi/L) (one picocurie equals 10-12 curies), with the highest well averaging an excess of 1,851 pCi/L during this time. Radium-226 and Th-230 were also detected in the groundwater. These monitoring results showed average concentrations for Ra-226 and Th-230 of 0.64 pCi/L and 0.8 pCi/L, respectively. The highest concentrations detected showed levels of 1 pCi/L for Ra-226 and 1.8 pCi/L for Th-230.

In 1988, groundwater monitoring at SLAPS showed the concentrations of total uranium ranged from background (bkg) to over 5,500 pCi/L, for Ra-226 the concentrations ranged from bkg to about 1 pCi/L, and for Th-230 the concentrations ranged from bkg to over 50 pCi/L at on-site locations (Bechtel, 1989a). At HISS, groundwater samples from the site showed uranium concentrations ranging from bkg to 87 pCi/L, Th-230 from bkg to 64 pCi/L, and Ra-226 from bkg to 3.7 pCi/L (Tables 1, 2).

Surface Water

Surface water sampling in Coldwater Creek by the SLAPS showed the maximum concentration of total uranium, including background, was 4 pCi/L. The concentrations of Th-230 and Ra-226 were at or below bkg (Bechtel, 1989a). Surface water measurements for radionuclides at the HISS showed the presence of total uranium ranging from bkg to 5 pCi/L, Th-230 ranging from 0.1 to 0.9 pCi/L, and Ra-226 ranging from 0.1 to 0.3 pCi/L (Tables 1, 2).


Sediment sampling at the SLAPS for total uranium, Th-230, and Ra-226 showed maximum concentrations of 1.7 pCi/g, 4.1 pCi/g, and bkg, respectively (Bechtel, 1989a) (Table 1). Sediment sampling at the HISS for total uranium, Th-230, and Ra-226 showed average concentrations of 1.7 pCi/g, 4.8 pCi/g, and 1.2 pCi/g, respectively (Table 2) (Bechtel, 1989b).


Airborne contamination at these areas consists of both gamma radiation and Rn-222. The amount, or intensity, of gamma rays depends on the type of radioactive material at the site, its concentration and depth from the surface, and physical distribution in the soil. This intensity results in an exposure rate. Measurements of the gamma ray exposure rate were made with a pressurized ionization chamber. The Rn-222 concentration is dependent on the amount of Ra-226 present, since Rn-222 is the first decay product produced during decay of the Ra-226. Airborne measurements for Rn-222 were the average of 25 stations determined by alpha track detectors. The bkg station was 5 miles from the areas.

At the SLAPS, the gamma exposure rate has been measured at 9 to 261 x 10-6 roentgens per hour (R/hr, a roentgen is a unit of radiation exposure), with an average of 84 x 10-6 R/hr taken along the northern boundary (Bechtel, 1987c). In 1988, gamma radiation measurements showed a radiation exposure rate ranging from 17 to 2,229 x 10-3 R/yr above a bkg average of 73x10-3 R/yr (Bechtel, 1989a).

At the HISS area, the exposure rate was 13 to 55 x 10-6 R/hr, with an average of 24 x 10-6 R/hr. The exposure rate at the FUTURA site was 8 to 27 x 10-6 R/hr outside existing structures. The bkg in the St. Louis area was 8 x 10-6 R/hr. Gamma radiation readings at the site during 1988 ranged from 13 to 55 x 10-6 R/hr with an average exposure rate of 24 x 10-6 R/hr with the bkg in the St. Louis area of 8 x 10-6 R/hr.

Rn-222 measurements at the SLAPS site, including the bkg of 0.3 pCi/L, ranged from bkg to 6.8 pCi/L with a maximum average of 3.4 pCi/L. Results from the HISS ranged from bkg to 3.4 pCi/L with a maximum average of 1.8 pCi/L. Because gas emanation is dependent on atmospheric temperature and pressure, there were seasonal variations in the measurements. Rn-222 at the SLAPS for 1988 ranged from 0.3 to 4.6 pCi/L, including a bkg reading ranging from 0.3 to 0.6 pCi/L. Background sampling locations were located a minimum of 0.5 mile from the site. The average Rn-222 concentration at the site from 1984 to 1988 has ranged from 0.1 pCi/L to 3.6 pCi/L (Bechtel, 1989a). The DOE limit for FUSRAP sites is 3 pCi/L.

Ra-222 at the HISS for 1988 ranged from 0.3 to 2.4 pCi/L, including a bkg reading ranging from 0.3 to 1.0 pCi/L. Background sampling locations were located a minimum of 5 miles from the site. The average Rn-222 concentration at the site from 1984 to 1988 has ranged from 0.2 pCi/L to 2.2 pCi/L (Bechtel, 1989b).


In a limited characterization for nonradioactive materials present at the SLAPS area, no elevated levels of total organic halogens were detected in soils. This would suggest a lack of or very small amounts of halogenated organic compounds such as pesticides, polychlorinated biphenyls, or solvents. However, three samples suggested the presence of total organic carbon, present at a level of 1 percent. The analysis of soils for heavy metals suggested the presence, above bkg, of selenium (93 ppm), beryllium (190 ppm), nickel (5,800 ppm), copper (2,300 ppm), cobalt (4,600 ppm), tin (4,400 ppm), molybdenum (150 ppm), magnesium (19,000 ppm), thallium (33 ppm), lead (580 ppm), antimony (2,300 ppm), and cadmium (3.5 ppm) (Bechtel, 1987c). The depths at which these samples were collected were not given. Of these heavy metals, selenium and lead appear to pose a potential health risk.

The concentrations of radioactive materials at the SLAPS include uranium (1,600 pCi/g), Th-230 (2,600 pCi/g), Th-232 (63 pCi/g), and Ra-226 (5,600 pCi/g) (Table 1) (Bechtel, 1987c).

The radionuclides detected at the HISS as determined by actual soil analysis included U-238 (800 pCi/g), Th-232 (0.7-5 pCi/g), Th-230 (790 pCi/g), and Ra-226 (700 pCi/g) (Table 2) (Bechtel, 1987a ). The average depth of the contamination was 3 feet with the deepest contamination of 6 feet at one location within the site (Bechtel, 1987a).

Soil measurements collected at the FUTURA area indicated the presence of uranium (2,500 pCi/g), Th-230 (2,000 pCi/g), Th-232 (26 pCi/g), and Ra-226 (2,300 pCi/g) (Bechtel, 1987b).

Currently, biota measurements have not been collected on-site.

B. Off-Site Contamination

Off-site areas associated with this site include Coldwater Creek and the road systems used to haul radioactive materials to the SLAPS area and from the SLAPS to the HISS and FUTURA areas. Additional off-site locations include the Berkeley Khoury League Park (Figure 2); properties next to the site, collectively known as the Latty Avenue Properties (Figure 4); the Norfolk and Western Railroad property; and portions of property near the SLAPS location including ditches, Banshee Road, and portions of land owned by the St. Louis Airport Authority.


Sediments and soils from Coldwater Creek were collected before 1989 by Bechtel. These samples were analyzed for the presence of radioactive materials. The results of sediment sampling show the presence of U-238 (4.8 pCi/g), Th-232 (1.5 pCi/g), Th-230 (110 pCi/g), and Ra-226 (3.1 pCi/g). Of these values, only Th-230 was above the DOE guidelines for FUSRAP locations. Surface soils from along the creek bank suggested the presence of U-238 (78 pCi/g), Th-232 (5 pCi/g), Th-230 (5,100 pCi/g), and Ra-226 (71 pCi/g) (Bechtel, 1990).

During 1989, the COE requested that additional soil plug samples be collected along the banks of Coldwater Creek. These samples were collected beginning at the termination point of the Bechtel study and proceeded for an additional 4.8 miles along the banks at 500 foot intervals. The top 6 inches of the soil plug were also analyzed for U-238, Th-232, Th-230, and Ra-226. The results of these sampling activities showed the maximum concentrations (above background) of U-238, Th-232, Th-230, and Ra-226 were 12.9 pCi/g, 4 pCi/g, 27.7 pCi/g, and 2.4 pCi/g, respectively. Of these levels, Th-230 exceeded the DOE clean-up levels. It has not been determined if the concentration of uranium in this survey exceeds guidelines since the guidelines are still being formulated for the St. Louis area (FUSRAP, 1989).

The results of soil sampling from over 60 properties located along the haul roads have been reviewed and summarized. The maximum levels detected and the corresponding depths are given in Table 4 (Bechtel, 1990). The contamination was mostly confined to a depth of a foot over the haul roads. Along Latty Avenue, however, in one area, the contamination was found as deep as 7 feet. The survey along McDonnell Boulevard suggested the contamination in one location was at least 15 feet deep and over 1300 feet in length. In one isolated area near the intersection of Eva Avenue and McDonnell Boulevard, the contamination was found to a depth of 5 feet. Along Hazelwood Avenue, the contamination was spread from the intersection of Frost Road to Pershall Road. Contamination along Pershall Road was found at an average depth of 3 feet, with an isolated area contaminated to a depth of 13 feet (Bechtel, 1990).

The results of sampling supplied from the Latty Properties were for near surface (12 inches above the surface), borehole readings for gamma-emitting contamination, and soil sampling for radionuclides. These data are shown in Table 3 (Bechtel, 1988).

Results of sampling from the Berkeley Khoury League Park recreational area indicated that the concentrations, in soils, of U-238 were 10 pCi/g; Th-230, 20 pCi/g; and Ra-226, 2 pCi/g.


The ditches running along the boundary of the SLAPS were sampled by measurements in boreholes for the presence of gamma-emitting radioactive materials and soil samples. The major contaminant in these areas was Th-230, present at a maximum concentration of 15,000 pCi/g. The U-238, Th-232, and Ra-226 concentrations were 94 pCi/g, 6 pCi/g, and 130 pCi/g, respectively. These maximum contaminant levels were found in surface soils (a maximum depth of 1 foot).

Banshee Road borders the SLAPS on the southern boundary. The sampling of this area included 48 boreholes and sampling of surface soils. Two areas showed elevated levels of Th-230 (34 pCi/g) with U-238 (<46 pCi/g), Th-232 (<7.1 pCi/g) and Ra-226 (<7.1 pCi/g) also present.

Airport Property

No off-site air sampling data for Rn-222 were supplied.

Results of general sampling of biota along ditches near the creek showed that Ra-226 ranged from 0.008 to 0.2 pCi/g, Th-232 ranged from 0.0004 to 0.003 pCi/g, and U-238 ranged from 0.02 to 0.16 pCi/g (Bechtel, 1983).

C. Quality Assurance and Quality Control

In preparing this preliminary health assessment, the ATSDR relies on the information provided in the referenced documents. The ATSDR assumes that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analyses and conclusions drawn for this preliminary health assessment is determined by the availability and reliability of the referenced information.

In order to identify other possible facilities that could contribute to the release of contaminants into the environment near the SLAP site, ATSDR searched the most recent data contained in the Toxic Chemical Release Inventory (TRI). TRI is developed by the EPA from the chemical release (air, water, and soil) information provided by specified industries. In searching the data base by zip code, there were no reporting facilities in the same zip code as the SLAP site that released either radioactive materials or heavy metals to the environment.

D. Physical and Other Hazards

The three areas composing the NPL site are fenced and placarded as a radiation area. There are no physical hazards at these areas. The baseball field is not part of the NPL site, but the city of St. Louis has closed the field and placed signs stating the area is closed. The area is not fenced and access is not controlled.


A. Environmental Pathways (Fate and Transport)

The Coldwater Creek flows through or forms the boundary of the SLAPS areas. There is no known use of the creek for recreational purposes or as a water source near the site. The creek, 19 miles in length, originates about 3.5 miles south of SLAPS, flows for about 500 feet along the western boundary of the site, and then flows into the Missouri River about 15 miles northeast of the SLAPS area (FUSRAP, 1989). The river serves as the area's source of potable water, with the nearest water treatment facility on the Missouri River above the confluence of the creek with the river. The SLAPS was used without liners or a leachate collection system, and runoff has entered the creek. Surface water runoff ultimately flows into Coldwater Creek by direct overland flow or by drainage ditches into the creek that flows north-northeast into the Missouri River.

There are two groundwater systems at the SLAPS. The upper zone is composed of a wind deposit or an eolian layer and a lacustrine or lake deposit. The lower zone is composed of the lake deposit material only. Separating the upper and lower zone is a deposit of legislature silty clay (Bechtel, 1986). The underlying aquifer is alluvial and approximately 25 feet below the surface, is estimated to be 100 feet thick, and includes clay, silt, and gravel deposits. The depth to the water table ranges from 25 to 35 feet. The water from the system is saline, and wells produce low volumes of water. There is no known use of the aquifer within a 3-mile radius of the site.

Leaching from the soil to the groundwater has occurred. It is unknown if the groundwater, which is believed to flow toward Coldwater Creek, discharges into the creek.

The air pathway includes ionizing radiation, Rn-222, and the possible exposure from airborne dusts contaminated with radioactive substances or heavy metals. The ionizing radiation can easily penetrate air and nominal thickness materials with no or very little attenuation. Rn-222 is an inert, radioactive gas and migrates easily through air. The decay products of radon are particulate and can electrostatically attach to the dust particles.

There are no identified pathways for exposure from potentially contaminated biota. No commercial or private crops are grown in the area and no hunting or fishing is likely to occur in these areas.

B. Human Exposure Pathways

The surface water and groundwater near SLAPS are not used for water sources in the area, therefore, these pathways are not considered viable routes for exposure. Furthermore, the EPA drinking water standards (40 CFR 141) for radioactive materials are not exceeded in Coldwater Creek.

The exposure to ionizing radiation in the areas, although elevated in some sites, is not of concern because of the small amount of time a member of the public would spend in the areas of higher radiation.

The concentrations of Ra-226 and Th-230 at on-site locations are above the EPA and DOE limits of 5 pCi/g from 0 to 15 cm and 15 pCi/g over any 15 cm of soil beneath the surface (40 CFR 190-192). Since these areas are now fenced and covered with clean fill, this exposure route is not of great concern. There is concern, however, with the soil concentrations at the off-site Latty Properties because access to these areas are not as restricted as that of the SLAPS, HISS, and FUTURA areas. Many of these properties are businesses with public access areas.

The release of Rn-222 from the soils into the air at the SLAPS exceeds the regulations of DOE for FUSRAP sites (3.0 pCi/L) and poses an inhalation hazard to on-site personnel. Atmospheric dispersion of Rn-222 from these sites is expected to reduce the levels of Rn-222 to approximately background levels (0.3 pCi/L) and no adverse health effects would be expected in those individuals occupying nearby homes and businesses. Radon, however, does become a potential health hazard when present in elevated levels inside inhabited structures such as homes and businesses. From the information reviewed for this public health assessment, ATSDR does not have any indication that material from the SLAPS was ever used for fill around foundations, potentially increasing the concentration of indoor radon.

The elevated levels of the heavy metals antimony, beryllium, cobalt, nickel, selenium, and lead at the SLAPS, although of some public health concern, are not considered an imminent threat since the contaminated area is fenced and there is no public access.

Inhalation or ingestion of airborne contaminants associated with dusts potentially generated either at the on-site locations or, to a lesser degree, from the off-site locations, can result in radiation exposure to the respiratory system and, to a lesser degree, exposure to the gastrointestinal tract.

Additional inhalation and ingestion of soil contaminants may have occurred during the use of the recreational fields when fugitive dusts were generated during athletic events. Because the haul roads associated with these sites are known to be contaminated with radioactive materials, exposure to human populations may have occurred during remediation of the roads in 1986 and during use of the roads by commercial and private vehicular traffic.


A. Toxicological and Radiological Evaluation

The evaluation of toxicological and radiological properties of contaminants and their effects on human health depends on a variety of factors. First, a person must be exposed to a chemical by coming in contact with it, and with certain types of radiation, by being in the vicinity. Second, the type and severity of adverse health effects resulting from an exposure to a contaminant depends on the concentration, the frequency and/or duration of exposure, the route of exposure, if the exposure was to a single contaminant or a mixture of contaminants and if there were multiple exposures.

For chemicals, the route of exposure can include breathing, drinking, eating, or dermal (skin) contact with a substance that contains the contaminant. In the case of ionizing radiation, the energy can pass through solid matter. A combination of contaminants can result in synergistic actions, where the simultaneous action of the separate compounds together, have a greater total effect than the sum of their individual effects.

The opposite is also a possibility whereby the combination of contaminants can act antagonistically, with one contaminant acting in opposition to or counteracting another contaminant. A third situation could result with the contaminants having no effect on each other.

Once an exposure has occurred, characteristics such as age, sex, race, socioeconomic status, genetics, lifestyle, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes, and excretes the contaminant. All these factors and characteristics are considered when determining the health effects that may occur as a result of exposure to a contaminant.

The contaminants of concern at SLAPS are Rn-222 (radiological half-life of 3.8 days) and Th-230 (radiological half-life 75,400 years). Chemically, these contaminants pose no health threat. Because of the type of radiation these radionuclides emit--alpha particles and gamma rays--the greatest public health concern arises from inhalation or ingestion of the material.

Radon-222 (Rn-222):

Rn-222 measurements at the SLAPS site ranged from bkg to 6.8 pCi/L and at HISS, the Rn-222 ranged from bkg to 3.4 pCi/L. As previously stated, the DOE FUSRAP limit for Rn-222 emissions is 3 pCi/L. The EPA recommends that Rn-222 not exceed 4 pCi/L in residential areas. There were no reported measurements for off-site areas. However, the outdoor levels of Rn-222, although above average background levels are approximately equal to the concentration many homes across the nation.

Rn-222 has been shown to be carcinogenic when inhaled, producing lung cancers. Most of these studies have involved uranium miners because radon is present at high concentrations in these mines. Although the gas itself is inert, some will be absorbed into the blood from the lungs and transported through the body (ATSDR, 1989a). However, the radon decay products are charged particulates in nature and will electrostatically deposit on lung surfaces. As these products decay further, many emit alpha particles that are completely absorbed in the structures containing the radon decay products. These particles are the major health hazard from exposure to radon gas. The National Council on Radiation Protection and Measurements (NCRP) estimates the annual dose from radon to the bronchial epithelium is 190 millirads for males and 10 year old children and 170 millirads for females (a rad is an estimate of the radiation exposure actually absorbed by a body). The lifetime risk of developing lung cancer from the inhalation of radon at a concentration of a picocurie per cubic meter is estimated at 0.21 per 100,000 population. It is estimated that the annual exposure to radon alone exceeds the exposure to all other naturally occurring sources of radioactivity (NCRP, 1984).

Thorium-230 (Th-230):

The concentration of Th-230 in soils at these sites is in the picocurie range and 1 picocurie of Th-230 has a mass of 48 x 10-12 grams (picograms). This amount of thorium is not considered a chemical hazard. The Annual Limit on Intake for Th-230 is 15 pCi via inhalation. In soils, the maximum reported on-site concentration was 2,600 pCi/g; whereas the maximum reported off-site concentration was 15,000 pCi/g in the ditches associated with the railroad areas.

Mice exposed to milligram amounts of thorium per cubic meter for 18 weeks showed no compound-related mortality. Similar types of studies with rats, guinea pigs, rabbits, and dogs resulted in similar findings. There have been no studies with humans concerning systemic exposures to thorium alone. A statistically significant excess of deaths resulting from pancreatic cancer has been reported in former thorium workers exposed to 0.13 milligrams/cubic meter (ATSDR, 1989b). Based on the amount of thorium present at these areas, the greatest hazard is the internal exposure to alpha particles and other radiations emitted from Th-230. The committed whole body dose equivalents (the radiation dose delivered over a 50-year period following intake of a specific radioactive substance) for this radioisotope are approximately 0.32 x 10-3 rem per picocurie inhaled and 0.54 x 10-3 rem per picocurie ingested (USEPA, 1988).

Appendix A gives the DOE calculations for individuals using the recreational fields. The ATSDR has reviewed these calculations, and ATSDR's calculations were higher than those calculated by the DOE (ATSDR-15 mrem; DOE-6.5 mrem). ATSDR agrees with the initial calculation of the amount of contaminated dust inhaled. The difference in calculations appears to be in the amount of dust potentially ingested by a ball player. The DOE did not estimate the ingestion of soils by a person sliding into a base in the contaminated areas but used a value of 100 milligrams of soil ingested. The ATSDR used a value of 1 gram of soil being ingested which would account for the increase in the committed dose.

B. Health Outcome Data Evaluation

The National Academy of Sciences BIER V report estimates the risk of excess cancer mortalities related to these types of radiation exposure at 5 excess deaths per 1000 exposed population (NAS, 1990).

In response to the 1988 request at five hazardous waste sites in the St. Louis area, the MDOH conducted a health statistics review of mortality and incidence data by census tract and zip code. The mortality data were obtained from death certificates submitted to the State Center for Health Statistics. Incidence data were obtained from the MCR. In reviewing the mortality and incidence data MDOH had not discovered any excess of cancer.

Following a 1989 report of excess cancer adjacent to HISS, the MDOH, Bureau of Smoking, Tobacco, and Cancer opened an investigation by collecting information on the reported cancer cases and interviewing residents, relatives of cancer victims, and cancer victims to determine if any other cancer cases had occurred near the site. In February 1989, based on confirmation of cancer cases reported and knowledge of radioactive contamination at the waste sites in the area, the MDOH Cancer Inquiry Committee recommended expanding the inquiry.

The expanded inquiry included further interviews of residents and former residents, examination of medical records, and construction of chronology of deposition of radioactive materials, and chronologies of diagnosis dates and time residence of the cancer patients. Statistical tests used to evaluate the data were limited by incomplete information on the total number of residents who lived in the area during the last few decades, their ages, and how long they lived in the area, and by the small number of people and cancer cases on the street. Another problem in determining whether or not a cancer excess or a cancer cluster exist is the existence of several different kinds of cancer among the cases. A cancer cluster is used to describe a grouping of a number of cases of the same type of cancer that may be due to the same cause. Different types of cancer generally have different causes, it is usually unlikely that a grouping of different types of cancer would arise from the same cause. The MDOH was unable to confirm whether or not there is an excess number of cancers in the area and to determine the likelihood residence were exposed to types, quantities, and durations of radiation that would have induced the identified cancers.

Members of the Division of Health Studies, ATSDR, have met with MDOH and investigated these reports excess cancer. As a result of this investigation, ATSDR reviewed the MDOH health statistics review and cancer inquiry. ATSDR concluded that due to the lack of similarity with regard to site and histologic type, the reported cancer cases do not constitute a cancer cluster. In addition ATSDR concluded there is insufficient data to determine an increase incidence of cancer in the Hazelwood neighborhood or whether the identified cancers cases could be attributed to radiation exposure. Furthermore, the types of cancers in the Hazelwood area are not normally associated with exposure to alpha emitters found at this site but with exposure to gamma radiation.

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