PUBLIC HEALTH ASSESSMENT
WELDON SPRING SITE REMEDIAL ACTION PROJECT
(CHEMICAL PLANT, RAFFINATE PITS, QUARRY)
ST. CHARLES, ST. CHARLES COUNTY, MISSOURI
There is documentation of the release of chemical and radioactive contaminants into theenvironment from the chemical plant site (chemical plant, raffinate pits, and the quarry). In thissection, Agency for Toxic Substances and Disease Registry (ATSDR) scientists evaluate whetherpeople are exposed to chemical and radioactive contaminants from the chemical plant site and, ifthey are exposed, what the public health implications are. This section also contains the findingsof prior ATSDR evaluations to address community members' exposure concerns (Table 1).
The release of contaminants into the environment does not always result in exposure. Todetermine whether people are exposed to contaminants from the chemical plant site and theWeldon Spring Ordnance Work Site, ATSDR scientists evaluate the environmental and humancomponents that can lead to human exposure. The evaluations include examinations ofpublished reports, environmental data, transport mechanisms, land use, and resource use toidentify exposure pathways by which a contaminant migrates from a source to an area where thepublic may come in contact with the contaminant. An exposure pathway consists of fiveelements: a source of contamination, transportation of environmental media, point of exposure, aroute of human exposure, and an exposed population.
The pathways analysis determines the status of each pathway. Exposure pathways may be (1)complete (all five pathway elements exist, exposure is occurring); (2) potential (at least one ofthe five elements is missing but the missing element could exist, exposure may occur); or (3)incomplete (one of the five elements is missing and will never be present, exposure will notoccur).
After identifying complete and potential exposure pathways, ATSDR health scientists determinethe public health implications of each completed pathway. Different methods are used to evaluatethe public health significance of exposure pathways for chemical contaminants and radioactivecontaminants.
To evaluate exposure to chemical contaminants, ATSDR toxicologists initially conduct apreliminary screening of chemicals identified at points of exposure to determine whethercontaminants are present in an environmental medium at concentrations that may be of healthconcern (see Appendix A). This preliminary screening compares the maximum concentration ofeach chemical found in each medium to a chemical- and media-specific ATSDR health-basedcomparison value. ATSDR comparison values are extremely conservative and protective ofpublic health in that they are based on daily long-term exposure to chemical doses that areunlikely to result in adverse health effects. Chemicals with maximum concentrations that exceedATSDR health-based comparison values are evaluated in further site-specific detail to determinethe public health implications of exposure. This site-specific evaluation involves estimatingchemical exposure doses from realistic site-specific exposure scenarios and comparing them withstandard health-based doses that are unlikely to cause an appreciable risk to health as well as toother medical and toxicological information. If the maximum concentration of a chemical isbelow the ATSDR health-based comparison value, exposure to the chemical at the point ofexposure is unlikely to pose a public health hazard and there is no further assessment ofexposure.
To evaluate radioactive materials, ATSDR health physicists use location-specific exposurescenarios instead of single media-specific comparison values because people can be exposed toradioactive materials in one or more environmental media (see Appendix C). These arehypothetical exposure scenarios, representing site-specific activities that have occurred or areoccurring at or near the site. We estimate total exposure to radiation for each scenario byconsidering the maximum concentration of each radionuclide in each environmental medium thatcontributes to exposure. From this estimate of total radiation dose, we subtract backgroundradiation doses (i.e., the natural amount of radionuclides present in the environment thatcontributes to the total radiation dose) to get the net radiation dose. We compare this radiationdose with nationally accepted standards to determine public health implications of each exposurescenario. For the general public (i.e., anyone not specifically classified as a radiation worker), themaximum net annual radiation dose is limited to 100 millirem per year (mrem/yr).
On-site describes locations on the U. S. Department of Energy (DOE) chemical plant site, whichincludes the chemical plant area, raffinate pits, and the quarry (see Figures 2 and 3). Thechemical plant area, raffinate pits, and quarry are each enclosed by fences and have 24-hourguards at the entry gates. With public access restricted, current exposure pathways involvingchemical contaminants in on-site soil, sediment, and sludge are incomplete, and no exposureexists to pose a public health hazard. Because local residents expressed concern abouttrespassing in the past, ATSDR evaluated potential trespassers' exposure and found thattrespassers' infrequent short-term past exposure was highly unlikely to result in health effects.
Sludge samples from raffinate pits and a few soil samples from within the chemical plant areacontain arsenic, lead, vanadium, nitrates, 2,4,6-trinitrotoluene (TNT) and polychlorinatedbiphenyls (PCBs) at concentrations that exceed ATSDR screening comparison values for chronicsoil ingestion. Concentrations of arsenic, lead, PCBs, TNT, and polycyclic aromatichydrocarbons in a few soil samples from the quarry also exceeded ATSDR screening comparisonvalues for chronic soil ingestion. Frequent and long-term ingestion of these contaminated on-sitesoils may result in exposure doses that can cause adverse health effects. However, trespassers'infrequent short-term exposure to chemicals in on-site soil, sediment, and sludge is highlyunlikely to result in health effects. Because of access restrictions, exposure pathways tochemicals in on-site soil, sediment, and sludge are incomplete and do not pose a public healthhazard.
Several residents expressed concern over exposures that may have occurred as a result oftrespassers swimming in the raffinate pits or quarry. Past access restrictions included chain-linkfencing and warning signs, and current restrictions include the addition of 24-hour guards. As aresult of current access restrictions, exposure pathways to chemical contaminants in on-sitesurface water are incomplete, and no exposure exists to pose a public health hazard. In addition,past swimmers' infrequent short-term exposure to chemicals in on-site surface water is highlyunlikely to result in health effects.
Surface water samples collected from the raffinate pits from 1983 to 1987 containedconcentrations of antimony, arsenic, chromium, lead, molybdenum, nitrate, sulfate, selenium, andvanadium that exceeded the ATSDR screening comparison values for chronic ingestion ofdrinking water. Quarry surface water samples collected from 1979 to 1987 contained arsenicconcentrations that exceeded the ATSDR screening comparison values for chronic ingestion ofdrinking water. Frequent and long-term ingestion of surface water from the raffinate pits and thequarry may result in chemical exposure doses that can cause adverse health effects. However,trespassers' infrequent short-term exposure to chemicals in on-site surface water is highlyunlikely to result in health effects.
DOE maintains more than 80 groundwater monitoring wells within the chemical plant and quarryboundaries (see Figure 6). These wells do not provide water for consumption, and site safetyplans stipulate precautions to prevent accidental exposure to groundwater. Because chronicexposure to groundwater from on-site wells is not possible and accidental ingestion is veryunlikely, the on-site groundwater pathway is incomplete, and no exposure exists to pose a publichealth hazard.
Groundwater samples collected from on-site monitoring wells in 1979, 1980, 1981, 1985, and1987 contained antimony, lead, manganese, nitrates, sulfates, and 1,3,5- trinitrobenzene atconcentrations that exceeded the ATSDR screening comparison values for chronic ingestion ofwater. Infrequent short-term exposure to chemicals in on-site groundwater is unlikely to result inany adverse health outcome. Without a completed chronic exposure pathway, the on-sitegroundwater is not a public health hazard.
Many on-site buildings and pipelines contained or were covered by asbestos insulating material.Removal and demolition of those facilities could expose workers to airborne asbestos. However,safety procedures used by workers while removing asbestos-containing materials are designed tolimit exposures to workers and the public. U.S. Environmental Protection Agency (EPA) andOccupational Safety and Health Administration (OSHA) regulations require adherence to sitesafety plans and operational procedures. Because of these safety procedures and regulatoryguidelines, the on-site asbestos exposure pathway is incomplete, and no exposure exists to pose apublic health hazard.
Off-site areas are portions of the original 17,232-acre Weldon Spring Ordnance Works thatinclude the Weldon Spring Training Area, August A. Busch Memorial Conservation Area,Weldon Spring Conservation Management Area, University of Missouri-Missouri Research Park,and other small properties (see Figure 2). In the 1995 Public Health Assessment for the WeldonSpring Ordnance Works Site and in various health consultations, ATSDR scientists evaluatedchemical contaminants in these off-site areas surrounding the DOE chemical plant site andassessed the public health implications of chemical contaminants in these off-site areas .ATSDR health physicists evaluated off-site radioactive contaminants in the RadioactiveMaterials Exposure Scenarios section of this public health assessment.
In the 1995 Public Health Assessment on the Weldon Spring Ordnance Works Site, ATSDRenvironmental health scientists determined that public access is controlled but that trespassersmight evade controls and gain access to the training area and contaminated conservation areas. However, this exposure would be infrequent and short-term and would represent no apparenthealth hazard . While preparing this health assessment, ATSDR environmental healthscientists reconsidered this information and concluded that the off-site soil pathway isincomplete, and no exposure exists to pose a public health hazard. Trespassers who ignore andevade security and warning measures may have short-term and infrequent contact withcontaminated soils.
In the 1995 Public Health Assessment on the Weldon Spring Ordnance Works Site, ATSDRenvironmental health scientists evaluated the potential for exposure to off-site groundwater andoff-site surface water. ATSDR scientists identified chemical contaminants associated withproduction processes in groundwater samples from monitoring wells and in surface watersamples from outfalls, springs, lakes, and streams within the boundaries of the former WeldonSpring Ordnance Works . The karst nature of the subsurface geology in the vicinity of the sitehas created many springs where groundwater becomes surface water and swallow-holes wheresurface water flows underground to become groundwater. ATSDR geologists determined that thekarstic terrain is such that tracing groundwater contaminant plumes with any accuracy is notpossible. However, in general terms, groundwater flow correlates roughly to surface waterdrainage .
In the 1995 public health assessment, ATSDR scientists concluded that, in the past people at theTwin Island Resort were exposed to low levels of explosive contaminants in drinking water fromresort wells (see Figure 4) ; however the extent of their exposure was unknown, and theirexposure was classified as an indeterminate public health hazard . Current exposure tochemical contaminants in groundwater from off-site private wells was reduced or eliminated in1989 when citizens were provided bottled water . After reconsidering this exposure pathway,ATSDR environmental health scientists concluded that the off-site private well water pathway iscurrently incomplete and poses no public health hazard.
In the 1995 Public Health Assessment of the Weldon Spring Ordnance Works Site, ATSDRscientists concluded that the contaminated groundwater exposure pathway at the training areais incomplete, and at the conservation areas, groundwater exposure is possible, although notfrequent. In both areas, groundwater exposure is not considered a threat [poses no healthhazard] to human health . No drinking water wells are within the conservation areas, andinstitutional controls enacted by the U.S. Army prohibit the use of groundwater on the trainingarea . Since the start-up of the Weldon Spring Ordnance Works and continuing today, the St.Charles County well field has supplied drinking water for these areas .
After reconsidering this exposure pathway, ATSDR environmental health scientists believe thatin both the training area and the conservation areas the groundwater exposure pathway isincomplete, and no exposure exists to pose a public health hazard.
Groundwater flow at the site can generally be roughly correlated to surface water drainages (i.e.,springs and streams), and public exposure is possible through contact with a few springs andstreams . The 1995 health assessment stated that because of the low probability that someonewould drink water from the springs and the lower probability that anyone would frequently drinkthis water, the springs should not be considered a threat [poses no health hazard] to humanhealth .
ATSDR scientists have determined that incidental ingestion of water (short-term exposure)containing these contaminant concentrations will not result in any health effects. Therefore, off-site surface water in the Weldon Spring Training Area, the August A. Busch MemorialConservation Area, and the Weldon Spring Conservation Management Area poses no publichealth hazard.
People drinking water from the St. Charles County Water Department are not exposed tochemical plant site contaminants. The municipal drinking water pathway is incomplete, and noexposure exists to pose a public health hazard.
The St. Charles County Water Supply District #2 provides drinking water to the chemical plantsite and to residents northeast of the chemical plant site . The county water department obtainswater from a municipal well field next to the Missouri River in the southern portion of theoriginal Weldon Spring Ordnance Works property (see figures 2 and 6) . This well field drawswater from the Missouri River alluvial aquifer and the bedrock aquifer . However, theproximity of the well field to the Missouri River and infiltration through the alluvial aquiferindicate that the major source of water is from the river . The water from the well field passesthrough the St. Charles County water treatment facility before being distributed to local users .The St. Charles County Water Department routinely monitors the municipal wells and adjacentmonitoring wells for site-related contaminants . Detectable levels of contaminants werereported on only one sampling event and are attributed to laboratory measurement error .
Extensive groundwater monitoring suggests that contaminants have seeped from the quarry .Contaminants from the quarry have been detected in shallow alluvial aquifer monitor wellsimmediately downgrade of the quarry, but exposure to the groundwater from these monitor wellsis not occurring (see Figure 6) . These contaminants in the groundwater have not migratedbeyond the northern margin of the alluvial aquifer and have not been detected in municipalsupply wells [2, 14, and 15]. This drinking water exposure pathway is incomplete. Inaddition, ongoing remediation at the quarry will further reduce the potential for contaminantmigration to the public water supply wells.
Effluent released from the chemical plant site water treatment plants into the Missouri River donot pose a public health hazard because the effluent is treated and monitored before released intothe Missouri River. The site's water treatment plant releases effluent into the Missouri Riverthrough an underground pipeline that runs parallel and south of the southeast drainage. A secondunderground pipeline runs parallel to Katy Trail and discharges effluent from the quarry watertreatment plant into the Missouri River. Discharge permits require that the effluent be evaluatedbefore its release to the Missouri River. Contaminant concentrations in the effluent are at orbelow background levels for area surface waters. Effluent is monitored for site contaminantsincluding total uranium, gross alpha, gross beta, and thorium and radium isotopes. Sampleanalyses by DOE, EPA, the Missouri Department of Natural Resources, St. Charles County, andSt. Louis County all show that the treated water is meeting all discharge requirements and thatcontaminant concentrations are below levels that may cause adverse health effects.
In a 1988 health consultation, ATSDR toxicologists concluded that no one should get sick fromeating fish from the lakes but recommended eating no more than one fish meal per month fromthose lakes . Based on more recent sampling data, ATSDR toxicologists concluded in a 1993health consultation that contaminant concentrations are lower than those in the 1989 report andthat no health effects are likely, even for persons consuming fish at subsistence consumptionrates . In the 1995 ATSDR Public Health Assessment on the Weldon Spring Ordnance Works,ATSDR scientists determined it is unlikely that fish in the conservation areas would becontaminated at levels of concern, based on recreational fishing . The health assessment alsoconcluded that recreationally eating fish from the conservation areas poses no apparent publichealth hazard .
After reviewing the 1995 health assessment, ATSDR scientists agree that recreationally eatingfish from the conservation areas poses no apparent public health hazard.
In the 1995 ATSDR Public Health Assessment on the Weldon Spring Ordnance Works, ATSDRscientists concluded that consumption of game animals from conservation areas is not anapparent public health hazard .
After reviewing the 1995 health assessment, ATSDR scientists agree that consumption of gameanimals from conservation areas is not an apparent public health hazard.
A few citizens mentioned concerns regarding potential release of toxic substances from failure ofa waste storage cell because of karst collapse or earthquake. The Weldon Spring area issusceptible to earthquakes and is underlain by karstified limestone . At the chemical plant site,limestone is overlain by relatively impermeable layers of clay and weathered limestone. Becauseof the low permeability of the clays capping the limestone and of the high water table, largesinkholes have not formed in these limestones . Placement of a low permeability surfacebarrier  will provide greater protection against acidic water reaching and dissolving theunderlying limestone. As a result of the natural and engineered features of the chemical plantsite storage cell, karst collapse is unlikely. Therefore, potential for contaminant release andhuman exposure is minimized. The use of appropriate design features and impermeable materialscan also reduce the risk of cell failure because of earthquakes. The storage cell will include bothclay and synthetic top and bottom liners to prevent leaching of groundwater. Even in the veryunlikely event of a storage cell collapse, leaching of contaminants to the water table aquifer (andpotential exposures to site contaminants) will be reduced if waste materials currently stored inthe open are stored in the proposed waste cell.
A few citizens mentioned concerns regarding potential exposure to emissions from a proposedincinerator. Information about a proposed plan for a hazardous material incinerator at the WeldonSpring Training Area is included in the 1995 Weldon Spring Ordnance Works public healthassessment . ATSDR's evaluation concluded that there will be no significant emissions ofcontaminants if the incinerator is appropriately designed and operated .
Radioactive Material Exposure Scenarios
Radionuclides have been detected in various media in areas where the public may have beenexposed or may be exposed currently. These points of exposure are in the chemical plant site,Weldon Spring Training Area, August A. Busch Memorial Conservation Area, Weldon SpringConservation Management Area, and off-site private wells. Maximum radionuclideconcentrations measured in the training area and conservation areas soil are presented in Table 3.The maximum radionuclide concentrations measured in surface water, fish, wild game, andgroundwater are presented in Table 4.
ATSDR health physicists evaluated hypothetical exposure scenarios that represent activities thathave occurred or are occurring at points of exposure in the chemical plant site, training area,conservation areas, and private off-site wells containing radionuclides. We then calculatedeffective radiation doses and determined the public health implications for each exposurescenario. In addition, health physicists evaluated community exposure concerns, such asexposure to trespassers swimming in Quarry and Raffinate Pits, airborne exposure at the FrancisHowell High School, and consumption of corn grown in nearby areas. For each scenario,ATSDR health physicists calculated the effective radiation dose using conservative exposureassumptions and the maximum radionuclide concentrations in each medium (see Appendix C).The use of conservative exposure assumptions and maximum concentrations of eachradionuclide in each medium overestimates potential radiation exposures and effective radiationdoses; therefore, ATSDR's approach is very conservative because realistic radiation exposuresand doses are much less than ATSDR's estimates. We compared the estimated effective radiationdose to nationally and internationally accepted standards, such as the annual radiation dose limitof 100 mrem/yr for the general public, to determine public health implications of each exposurescenario (see Appendix C).
Residues from the processing of uranium and thorium were placed in the quarry and raffinatepits, and water samples from these areas confirm the presence of radionuclides. Because ofcommunity members' concerns, ATSDR evaluated the risk of adverse health effects to personswho may have swum in these areas. ATSDR health physicists calculated an effective radiationdose of 0.4 mrem/yr to swimmers (see Appendix C). Based on this estimated annual effectiveradiation dose, swimming in the quarry or raffinate pits did not pose a radiation health hazard.
Radioactive contaminants have been detected in isolated soil samples from the Weldon SpringTraining Area. In the past, U.S. military reservists performing field training exercises in theWeldon Spring Training Area may have been exposed to radionuclides in soil, surface water, andair and to external radiation. ATSDR health physicists calculated an effective radiation dose of68.8 mrem/yr to reservists (see Appendix C). Based on this estimated annual effective radiationdose, the training area poses no apparent radiation health hazard to reservists.
Soil, surface water, fish, and wild game samples from the August A. Busch MemorialConservation Area and the Weldon Spring Management Conservation Area containradionuclides. Fishing, hunting, and hiking are common activities in the conservation areas.Anglers, hunters, and hikers may be exposed to radionuclides in conservation area surface water,soil, and air and to external radiation. In addition, anglers and hunters may be exposed toradionuclides by eating their catch. ATSDR health physicists calculated effective radiation dosesof 4.7 mrem/yr, 9.1 mrem/yr, and 6.1 mrem/yr for the angler, hunter, and hiker scenarios,respectively (see Appendix C). Based on these estimated annual effective radiation doses,fishing, hunting, hiking in the conservation areas do not pose an apparent radiation healthhazard.
Groundwater samples from off-site private wells contained radionuclide contaminants. In thepast, people who used and drank groundwater from these private wells may have been exposed toradionuclides by drinking the water and by breathing ambient air. ATSDR health physicistsevaluated a private well exposure scenario involving consumption of groundwater and inhalationof airborne radionuclides from groundwater. ATSDR health physicists calculated the effectiveradiation dose of 29.4 mrem/yr for people who, in the past, used groundwater from off-siteprivate wells (see Appendix E). Based on this estimated annual effective radiation dose, the useof off-site private well groundwater posed no apparent radiation health hazard in the past, doesnot pose a radiation health hazard now, and will not pose a radiation health hazard in thefuture.
At the request of local citizens, ATSDR completed a health consultation in 1994 on the potentialexposure of Francis Howell High School students and staff to airborne radionuclides from thechemical plant site. Results from DOE air monitoring samples did not indicate any airborneradioactive materials above background concentrations at the school. Also, measurements frommonitoring stations at the site boundary and at the high school during site building demolition(1993 calendar year) did not show any increased concentrations or exposures to site relatedcontaminants above background. Additionally, gross alpha particulate concentrations at thefacility boundary and the high school did not show any off-site migration of airborne alpha-emitting materials (uranium, thorium, etc.). ATSDR health physicists calculated an annualeffective radiation dose of 0.3 mrem/yr to the staff and students (see Appendix C). Based on thisestimated annual effective radiation dose, the site posed no apparent radiation health hazard tostaff and students at the school, and it does not pose a radiation health hazard now nor will it inthe future.
During interviews with the public, citizens expressed concern about the ingestion of crops grownnear the conservation areas. Portions of the conservation areas and farmlands outside theconservation areas are used to grow corn, soybeans, milo, wheat, and sunflowers. In generalpeople are likely to eat locally grown corn whereas the other crops usually require some type ofprocessing before people eat them. Therefore, it is unlikely that soybean, milo, wheat andsunflowers are grown directly for local human consumption.
According to Weldon Spring Site staff members, people do not eat the corn grown in theconservation areas. However, ATSDR health physicists evaluated human ingestion of the corn toaddress the public's concern. The estimated annual effective radiation dose to consumers of cornis 37.3 mrem/yr (see Appendix C). Based on this estimated annual effective radiation dose,eating corn grown in or near the conservation areas poses no apparent radiation health hazard.
The probability and severity of health effects increase as exposure to radiation increases,although exposure to background levels of radiation (i.e., those levels naturally occurring in theenvironment) are thought not to produce noticeable health effects in humans . Forradiation protection purposes, the effective radiation dose from radiation exposures abovebackground is calculated as an indicator of potential health effects. Cancer is believed to be thepredominant health effect associated with chronic radiation exposures [17, 18, 19, 20, and21]. The radiation exposures in areas adjacent to the chemical plant site are low-level, chronicexposures. Table 5 contains the internal and external doses calculated for potentially exposedpersons near the chemical plant site.
The total effective radiation doses for specific activities or populations near the chemical plantsite including background are less than the International Commission on Radiological Protection(ICRP) recommended 100 mrem/yr (excluding background) for the general public. Thesecalculated annual effective doses are unlikely to result in health effects. Therefore, based on theexposure scenarios evaluated in this public health assessment, the chemical plant site does notpose a public health hazard.
The contaminant values recorded in this public health assessment are based on data developedfor the U. S. Department of Energy, the Department of the Army, and the State of Missouri.These data were transferred electronically to ATSDR and translated into ATSDR's FederalFacilities Information Management System (FFIMS). The FFIMS contains a GeographicInformation System, which relates environmental sampling data to the location the datarepresent. Many of the environmental data ATSDR received could not be matched withgeographic locations, and many of the geographic locations did not have corresponding datavalues. When data values appeared erroneous, ATSDR staff members confirmed them with sitemanagers. Published reports and documents were used when possible to supplement analysis ofthe electronically-transmitted data.
The information ATSDR received included specific quality control parameters, such as fieldblanks, laboratory blanks, duplicate samples, and detection limits. Detection limits for all dataused in this report were lower than appropriate health comparison values, enabling ATSDR tohave confidence in its ability to evaluate exposures to contaminants for possible adverse humanhealth effects.
The Missouri Department of Health maintains health information within the Office ofSurveillance, Research, and Evaluation of the Division of Chronic Disease Prevention and HealthPromotion. The data comprise several components, including a cancer registry. This sectionassesses information from this registry that is relevant to community health concerns or toexposures occurring at the chemical plant site.
Community members expressed concern about several types of cancers: childhood leukemia,renal cell, nasal-pharyngeal, prostate, breast, and Hodgkin's disease. There was also concernabout the total numbers of cancer cases in the area. The Missouri Department of Healthinvestigated the incidence of these types of cancer in St Charles county, as well as the incidenceof all cancers in zip codes near the site (63303, 63304, 63341, and 63366) [22, 23]. Theresults of this investigation did not indicate that cancer incidence in these areas was elevated.However, one possible exception is for childhood leukemia in St Charles County. If fundingbecomes available, the Missouri Department of Health plans to conduct a more detailedinvestigation (i.e., a case control study versus a descriptive study) of childhood leukemia todetermine possible reasons for the increase in the number of new cases of leukemia.
Community members also expressed concern about effects such as autism, infertility, alopecia,aplastic anemia, and spina bifida. However, Agency for Toxic Substances and Disease Registry(ATSDR) staff have not been able to obtain information on the number of people in the area withthese conditions and, therefore, has no way of determining whether St. Charles County has higherthan expected incidence rates for these diseases. In the absence of definitive information aboutthe incidence rates for these diseases, the following sections will assess whether sitecontaminants have been related to those specific health outcomes identified by communitymembers (Tables 1 and 2).
Incidence data on childhood leukemia in St. Charles County for 1970-1993 indicate two timeperiods with statistically greater numbers of cases than expected [22, 23]. A 1986 report of ahospital record search identified 13 cases (7 expected) in children under 15 for 1975-1979. However, the 22 cases identified for the whole study period (1970-1983) were notstatistically greater than the 20 cases expected. Also, the geographic distribution of those casesdid not appear to have any relation to the chemical plant site .
A more recent data analysis has found 12 leukemia cases (6 expected) in St. Charles Countyfemales under 15 years of age for the period 1985-1991, but the overall occurrence of childhoodleukemia was not elevated . The Missouri Department of Health plans to follow up on theseresults, if funding becomes available, by conducting a case-control study of childhood leukemiain St. Charles County, including a detailed evaluation of the geographic distribution of thedocumented leukemia cases.
Most of the concerns about leukemia incidence have questioned the role of on-site radioactivecontaminants as a cause of leukemia. The primary radioactive materials at the site are uranium,thorium, and their respective decay products. Neither uranium nor thorium has been linked tochildhood leukemia [25, 26]. The incidence of leukemia has been linked to benzene,unidentified viral agents, and very high doses of radiation [27, 28]. ATSDR has not identified exposure to these contaminants.
ATSDR does not have information about the incidence rate of autism in St. Charles County.However, none of the contaminants present at the chemical plant site have been causally relatedto autism, and ATSDR scientists have not identified any completed pathways of public healthsignificance.
Uranium and several other heavy metals (i.e., mercury and lead) that are present at the chemicalplant site have been linked to renal diseases following oral and inhalation exposures [25, 29, 30]. However, these metals have not been linked to renal cell or other kidney cancers. Theinformation in the Missouri cancer registry for St. Charles County does not indicate a higher thanexpected rate of kidney cancers for this area. Based on the information available, exposure to sitecontaminants are not expected to result in renal cell cancer in residents of St. Charles County.
The State of Missouri's birth and death registries do not include the incidence rate of alopecia, soATSDR staff has no information about expected or observed rates. Many contaminants havebeen linked to alopecia, including several that are present at the chemical plant site [25, 29, 30,and Appendix D]. In areas of potential public exposure, these contaminants are present atbackground concentrations. Consequently, exposure at the conservation area is essentially thesame as exposures in residential areas of nearby St. Charles County.
Although exposure to these contaminants cannot be ruled out as a cause of alopecia, doses forthese contaminants via soil ingestion are much lower than those expected to create healthproblems. Additionally, there has been no identification of pathways of significant exposure tosite contaminants.
The State of Missouri's birth and death registries do not include incidence rates for infertility, soATSDR staff have no information about expected or observed rates. Reproductive problems havenot been identified with exposure to uranium  or thorium , although infertility has beenassociated with very high radiation exposures . The radiation doses that have been linkedwith temporary or permanent infertility  are single doses that are 10,000 to 350,000 timesgreater than the largest annual exposure identified at Weldon Spring (i.e., military personnel attraining area). ATSDR has not identified any pathways of radiation exposure that are capable ofproducing adverse health effects.
Data from the Missouri Cancer registry do not indicate higher than expected incidence rates forany of these cancers or for aplastic anemia in St. Charles County. ATSDR scientist have notidentified any pathways of significant exposure to any contaminants at the chemical plant site.The available data do not indicate that exposure to contaminants from the chemical plant sitehave caused these diseases in residents living around the site.
Institutional controls restrict (if not totally eliminate) public access to areas within the chemicalplant site, the Weldon Spring Training Area, and conservation areas that have significant levelsof explosives contamination. Localized high concentrations are not a danger in terms ofaccidental detonation, since even the pure product (2,4,6-trinitrotoluene [TNT] or 2,4-dinitrobenzene [DNT]) is extremely insensitive to physical shock. Also, remedial proceduresappropriate to the prevention of inappropriate handling or exposure to explosive materials are inplace .