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PUBLIC HEALTH ASSESSMENT

CORNHUSKER ARMY AMMUNITION PLANT
GRAND ISLAND, HALL COUNTY, NEBRASKA


PATHWAYS ANALYSIS

To determine whether nearby residents are exposed to contaminants migrating from a site, ATSDRevaluates the environmental and human components that lead to human exposure. This pathwaysanalysis consists of five elements: source of contamination, transport through an environmentalmedium, a point of exposure, a route of human exposure (for example, dermal contact or ingestion), andan exposed population.

ATSDR identifies exposure pathways as completed, potential, or eliminated. For a completed pathwayto exist, five elements must be present to provide evidence that exposure to a contaminant has occurred,is occurring, or will occur. A potential pathway, however, is defined as a situation in which at least oneof the five elements is missing, but could exist. Potential pathways indicate that exposure to acontaminant could have occurred, could be occurring, or could occur in the future. Pathways areeliminated when at least one of the five elements is missing and will never be present.

A. Completed Exposure Pathways

Private Well Pathway

Past, current, and future exposure pathways are possible by way of ingestion of contaminatedgroundwater from private wells. Waste sources at the site appear to be responsible for contaminationof groundwater near CAAP and Capital Heights. A major waste source was removed and remediatedin 1987, when approximately 44,000 tons of soil were incinerated. However, the groundwatercontamination plume is moving northeasterly at approximately 75 to 827 ft/year. Historically, between464 and 800 household drinking water supplies were affected or potentially affected (1). CAAP begansampling in 1982 and detected high concentrations of explosives in groundwater. Because local soilsare highly permeable, it is likely that groundwater contamination began when the installation initiatedsurface discharge of contaminants. In January, 1984, CAAP provided bottled water to approximately264 residents whose well-water contained RDX concentrations greater than 35 ppb. CAAP thenextended the Grand Island water supply line to the Capital Heights area and offered residents theopportunity to use that drinking water source. The Grand Island water supply is not (and likely neverwill be) considered a potential pathway.

A recent survey conducted by the City of Grand Island Utilities Department reported that five residenceschose not to connect to the city supply, but to continue to use their private wells for drinking water (25). Those homes are on Route 1, West 13th Street, and Engleman Road. It is unclear whether those privatewells have been sampled recently. In addition, some residents live outside the area accessible to the citywater connection, but near the contaminated groundwater plume. CAAP sampled private well waterfrom 10 residences on O'Flannagan, O'Grady, and North Webb streets in July, 1991. The analysesshowed that water from six of the ten wells contained concentrations of RDX greater than or close tothe 2 ppb action limit. The six concentrations ranged from 1.92 to 4.63 ppb. CAAP provided thoseresidents with an alternative water supply and planned to periodically check other areas to determineif an alternative water supply is necessary (12). Further study of the area resulted in a proposal toextend permanent water supplies (26). The proposal and public comment period (August 24-September24, 1992) was discussed at a public meeting on August 27, 1992 (27).

Reportedly, most residents have continued to use contaminated water for lawn and garden watering, andswimming pools. In addition, commercial irrigation wells used for crop irrigation and animal wateringare still operating. Recent information indicates that plants can efficiently absorb RDX. ATSDRdiscussed that information with USATHAMA, EPA, NDEC, and NDH and recommended stopping useof contaminated water for irrigation of private vegetable gardens. On July 30, 1991, NDEC and NDHadvised residents not to eat vegetables grown in gardens irrigated with water from private wells. Inaddition, NDEC and NDH recommended that residents stop using private wells for garden irrigationand stop using as compost grass clippings from lawns irrigated with private well water. ATSDRattended a public meeting sponsored by the state agencies on August 5, 1991, to discuss the newinformation with the public.

Residents using private wells were probably exposed to RDX and other explosives by way of ingestion,inhalation, and skin contact. Although ingestion is the most likely route of exposure to explosives,inhalation and skin contact could be routes for other, unknown contaminants. Analyses of watersamples historically have not included all potential contaminants; therefore, ATSDR is unable toevaluate all of the contaminants to which people could have been exposed. Groundwater plume locationand movement have not been completely characterized because of the lack of well construction data(except for the University of Nebraska monitoring wells), sampling frequency, and sampling parameters. Existing plume maps are difficult to read and often do not include sufficient detail about location. Thus,the exposed population and the concentrations to which people are being exposed are difficult todetermine. Capital Heights is approximately two miles from the CAAP boundary. Estimating theplume migration at an average 400 ft/yr up to 800 ft/yr, the first contaminants could have taken between13 and 26 years to reach the affected private wells. CAAP began operating in the 1940s and the CapitalHeights subdivision was developed in the early 1960s. The contamination might have already reachedthe private wells when the subdivision was developed. Residents using those wells could have beenexposed to some level of contaminants by way of ingestion and skin contact for approximately 30 years. Residents using private wells between CAAP and Capital Heights could have had a longer exposure.

Because the plume continues to migrate, residents near the affected areas can request from CAAPcontinued testing of their drinking water. If the water becomes contaminated, an alternative source,either bottled water or the city's water supply, can be substituted to eliminate exposure.

B. Potential Exposure Pathways

Little sampling information exists to document potential exposure pathways. Limited information isavailable on numbers of persons who might be exposed to contaminants.

Until more information becomes available, ATSDR cannot further assess those pathways or theirimportance.

Air Pathway

Air releases probably occurred from the 1940s until the mid 1970s, during open burning of wasteexplosives, solvents, oils, and other debris. Particulates and vapors associated with the burning representa past completed pathway to workers and nearby residents by way of inhalation. Prevailing winds arefrom the south in the summer and from the northwest in the winter. Summer winds are usuallymoderate to strong (1). The closest housing area is approximately one-half mile northwest and threemiles east. Although it is unlikely that critical concentrations of hazardous materials reached thoseareas, no air sampling data were available from that period to thoroughly evaluate the pathway.

On-Site Soil Pathway

Past, current, and future exposure pathways are possible because of contamination present in surfacesoils on site. Former employees, current tenants, and remedial workers could have been or are beingexposed to some level of contaminants by way of ingestion, inhalation, or skin contact withcontaminated surface soils. Limited surface soil sampling has been conducted, and current employeesand tenants have access to many of the potentially contaminated on-site areas. A major remediationeffort to remove contaminated soil took place in 1987. The extent of the remaining contamination hasnot been fully characterized, although further characterization is proposed in the RI/FS workplan. ATSDR will review that information when it becomes available.

A soil sample collected near a building in the North Magazine Area had lead contamination as high as1,460 ppm. That area has not been thoroughly characterized and hazardous substances may be in oraround individual magazine areas. Many current tenants use those areas and sometimes bring theirchildren on post; thus, a possible exposure pathway exists. Restricting access would eliminate theexposure.

Sediment Pathway

The eastern channel, western channel, and the railroad ditch accumulate runoff from the site, and, whenflowing, eventually discharge to Silver Creek. Those three primary collectors of surface runoff couldhave transported contaminants into sediments and surface waters. No sampling has been conducted toverify that exposure pathway. Access to Silver Creek is unrestricted. Sampling is planned for theditches as part of the RI/FS. Because most of the contamination was discharged into collection sumpsand transferred to the leach pits, large volumes or high concentrations of waste probably were nottransported off site by the ditches.

Food Chain Pathway

Past, current, and future exposure pathways are possible by way of ingestion of contaminated cattle andcrops. Irrigation wells are used to water animals and crops both on and off site. Several irrigation wellscontain RDX-contaminated water. Recent studies indicate that crops can uptake explosives (28, 29). Discussions were held among ATSDR, USATHAMA, EPA, NDEC, and NDH about possible vegetablecontamination, and, in August 1991, CAAP began sampling vegetables and soil from residentialgardens as well as soil from yards irrigated with RDX- and TNT-contaminated water. As described inthe Environmental Contamination and Other Hazards section, RDX was not found in vegetables at concentrations higher than the health-based risk level of 0.19 ppm.

The effects of watering cattle with contaminated water or of cattle ingesting contaminated soil have notbeen evaluated. From the limited information available (see the Public Health Implications section)about uptake of explosives by plants or animals, it is unlikely that concentrations would be high enoughto cause acute adverse health effects after eating meat or vegetables for a short period. For significantexposure to occur over a long period, the food source would have to continuously contain contaminantsat concentrations above health-based risk levels. Generally, families eat meat obtained from severalsuppliers rather than from a single source. Therefore, the chances that a family would ingestcontaminated meat over an extended period would be low. If a family regularly obtained their meatfrom the same supplier, however, a greater potential for exposure would exist.

The same would be true of most commercial supplies of vegetables. On the other hand, if over a longperiod of time a family relied on its own gardens (watered with contaminated water), or on a roadsidevegetable stand that sold vegetables from the same source (watered with contaminated water), theamount of exposure might be of concern. CAAP has made the city's water supply available to thefeedlot areas. Using the city water supply for watering livestock would eliminate the possibility ofcontaminant accumulation in cattle.

C. Summary of Pathways Analysis

The private well pathway is considered complete because exposure to some level of contaminants hasoccurred via ingestion and skin contact. People exposed include residents drinking contaminated privatewell water. Potential exposure pathways include on-site surface soil, sediment, food chain, and air. Exposure to surface soil and sediment could occur via ingestion and skin contact. Exposure tocontaminants could result from ingestion of contaminated food. Past inhalation of contaminants mighthave resulted from open burning on-site. Potentially exposed persons include former employees and nearby residents. Tables 8 and 9 outline exposure pathways.

Table 8.

Completed Exposure Pathway
PATHWAY NAME COMPOUNDS EXPOSURE PATHWAY ELEMENTS TIME COMMENTS
SOURCE MEDIA POINT OF EXPOSURE ROUTE OF EXPOSURE EXPOSED POPULATION
Private Wells Explosives, VOCs CAAP Groundwater Residences and Businesses Ingestion, Inhalation, Skin Contact Residents and workers near Capital Heights in the contamination plume, especially those using private well water for vegetable and lawn watering and in swimming pools Past
Present
Future
Sampling confirmed contamination in 1983. Most residents are using city water. All of the possible contaminants have not been analyzed for.


Table 9.

Potential Exposure Pathways
PATHWAY NAME COMPOUNDS EXPOSURE PATHWAY ELEMENTS TIME COMMENTS
SOURCE MEDIA POINT OF EXPOSURE ROUTE OF EXPOSURE EXPOSED POPULATION
On-Site Surface Soil Explosives, heavy metals, other unknowns CAAP Surface Soil On-site soils Ingestion, Inhalation, and Skin Contact Former employees, current tenants, and remedial workers Past
Present
Future
Limited soil sampling data are available for both on and off site; however, off-site migration is unlikely.
Sediment Unknown CAAP Sediment Eastern and western channels, railroad ditch, Silver Creek Ingestion, Skin Contact Nearby residents (especially children) Past
Present
Future
No sediment sampling data were available; however, contamination is likely.
Ambient Air Unknown CAAP Air Former employees and nearby residents and workers at businesses Inhalation Former employees and nearby residents Past No sampling data are available. Workers conducting open burning and downwind residents might have been exposed.
Food Chain Unknown CAAP,
local farms, and gardens
Food Chain (cattle, corn, alfalfa, and other crops) On- and off-site agricultural areas and residential yards Ingestion Consumers of farm products and residents using contaminated water for garden and yard irrigation Past
Present
Future
Surface soil data are not available for all areas. Extensive plant or animal uptake information was not available.


PUBLIC HEALTH IMPLICATIONS

In this section we will discuss health effects that might occur in people exposed to specific contaminants;evaluate state and local health databases that address those health effects; and address specificcommunity health concerns.

A. Toxicological Evaluation

To understand health effects that may be caused by a specific chemical, several factors related to theinteraction of the chemical with the individual must be considered. Health effects caused by a specificchemical are sometimes related to the route of entry into the body (i.e., inhalation vs ingestion of water). The amount or dose of a chemical to which a person is exposed may also determine the type or severityof health effects. Health effects are related not only to the dose to which the person is exposed, but tothe amount of chemical that the body actually absorbs. The manner in which a specific chemical isabsorbed, metabolized or otherwise broken down by natural body mechanisms also determines the typeof health effects that may result.

To determine the possible health effects produced by specific chemicals, ATSDR considers thepreviously discussed factors as described in the scientific literature. Compilation by ATSDR of thisinformation has resulted in a number of chemical-specific ATSDR documents called toxicologicalprofiles. Toxicological profiles are used for guidance in determining concentrations of specific chemicalsin the environment (i.e., air, soil, and water) that may be harmful to health under certain conditions (i.e.inhalation, dermal exposure, or ingestion) for different periods of exposure (acute, intermediate, orchronic). When toxicological profiles are not available for a certain chemical, we review varioussources, including the scientific literature, research reports, and reports from regulatory agencies.

The Pathways Analyses section of this document discussed the most likely chemicals to which peoplehave been exposed or are now being exposed. This section will discuss the health effects that may becaused by those chemicals. Those chemicals have been found on post in soil and groundwater as wellas in groundwater off post. Because little human exposure to contaminated soil is believed to be takingplace on post, the chemical-specific health effects will be discussed with respect to groundwater only.

HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE (RDX)

Information in the literature about the health effects of RDX in humans is primarily limited to plantworkers exposed to RDX dust by way of inhalation. Effects have included insomnia, restlessness,irritability, disorientation, epileptiform seizures (convulsions), and unconsciousness (30). Workers inthe report were exposed to finely powdered RDX dust; absorption was probably by inhalation. Allgenerally recovered within one day. No abnormalities were observed in workers' blood or urine. Whenexposure was prevented by hygienic measures, no further adverse effects were seen. Health effects fromexposure to smoke when RDX-containing plastic explosives were burned to heat food were also seenin U.S. soldiers in Vietnam (31, 32). Symptoms of central nervous system (CNS) toxicity, ranging fromconfusion to multiple seizures followed by amnesia, were seen.

Few studies have investigated inhalation exposure to more moderate concentrations of RDX in the air. A study was conducted of munitions plant workers exposed to RDX and HMX to determineabnormalities of the hematologic, hepatic, and renal systems. Of 93 workers with varying degrees ofexposure, no abnormal findings or presence of autoimmune disease were observed. No symptoms ofacute central nervous system toxicity were seen (33).

Acute CNS toxicity has also been seen after ingestion of RDX-containing material. Reports of soldiersin Vietnam eating RDX for purported hallucinogenic effects document generalized convulsions andstates of consciousness varying from coma to lethargy. Moderate changes in liver and kidney functionwere observed. No fatalities resulted, and mental capacity and other changes returned to normal within10-30 days (34, 35). The levels of RDX ingested in those cases ranged, if known, from 25-180 grams(g) of C-4 plastic explosive (91% RDX).

Ingestion of approximately 1.23 g (85 mg/kg body weight) C-4 by a three-year-old child also resultedin convulsive CNS symptoms, but no long-lasting liver or kidney damage (36). The child ingestedRDX from plastic explosive brought home on the contaminated clothing of his mother, who worked ina munitions plant.

The reports described here provide information about severe health effects after acute inhalation oringestion of RDX. However, because the routes of exposure and the doses vary from the situation foundat CAAP, the data do not adequately address possible chronic health effects of long-term exposure toRDX in drinking water. When adequate studies in humans are not available, studies in animals mustbe used to extrapolate information applicable to the exposure situation.

Three 24-month continuous feeding studies have been performed in mice and rats (37-39). The highestdoses of RDX used in those studies (40-100 mg/kg body weight/day) resulted in increased mortality,CNS effects, weight loss, anemia, liver toxicity, renal toxicity, testicular degeneration, and inflammationof the prostate. Inflammation of the prostate was seen at 1. mg/kg body weight/day, but not at 0.3mg/kg body weight/day (39). Testicular degeneration was seen in mice receiving 35 mg/kg bodyweight/day, but no toxic effects were seen at 7 mg/kg body weight/day (37).

The three studies also addressed the question of carcinogenicity of RDX. The two studies in rats foundno evidence of carcinogenicity (38, 39). The combined incidence of hepatocellular carcinomas andadenomas was significantly increased compared to control animals in female mice receiving 7, 35, and100 mg RDX/kg body weight/day over a two-year period (37). No significant increases were found atthe 1.5 mg/kg body weight/day dose level. The increased rates of carcinomas and adenomas were notsignificant when considered separately.

Based on various criteria of sensitivity and completeness in animal studies, EPA has used certain studiesto develop guideline values to protect human health. A series of guidelines can be developed,progressing at each step to include a greater number of considerations to protect human health.

The starting point for those EPA guidelines is the selection of a scientifically appropriate study. ForRDX, the lowest dose in mice that gave no demonstrable effect was 0.3 mg/kg body weight/day (39). The next highest dose of 1.5 mg/kg body weight/day caused an inflammation of the prostate gland. Aninitial EPA guideline called the No Observed Adverse Effect Level (NOAEL), for RDX is the dose of0.3 mg/kg body weight/day.

The next guideline is the EPA Reference Dose (RfD). A RfD is an estimate of a daily exposure tohumans that is likely to be without appreciable risk of deleterious effects over a lifetime. The RfD startswith the NOAEL and modifies it through consideration of uncertainty factors derived from the EPAOffice of Drinking Water guidelines which consider variations in experiments or species of animals usedin the experiments. Using the RfD, the EPA Drinking Water Equivalent Level (DWEL) is calculated;the DWEL is the lifetime exposure level, assuming 100% exposure from drinking water, at whichadverse noncarcinogenic health effects would not be expected to occur. The DWEL considers theassumed body weight (70 kg) and the assumed daily water consumption (2 L/day) of an adult. TheDWEL for RDX is 0.105 mg/L or 105 µg/L.

From the DWEL, an EPA Lifetime Health Advisory (HA) can be calculated. The EPA Lifetime HArepresents that portion of an individual's total exposure attributed to drinking water and is consideredprotective of noncarcinogenic adverse health effects over a lifetime exposure. The HA for a chemicalis a concentration in drinking water at which adverse health effects would not be anticipated and whichincludes a margin of safety to protect the most sensitive members of the population at risk (40). An HAis calculated from the DWEL with the consideration that drinking water may not be the only source ofexposure. If data are not available, a factor of 20% is used. For chemicals, such as RDX, that havebeen classified as Group C chemicals (possible carcinogens because experimental data are not complete)a further lowering of the HA value can take carcinogenicity into account. After these factors areconsidered, the EPA Lifetime Health Advisory for RDX is 0.002 mg/L or 2 g/L (i.e., 2 parts perbillion [ppb]). Similar water quality criteria for RDX have been calculated by others and compared tothe values derived by EPA (41, 42).

As can be seen, the amount of RDX that a person can drink over a lifetime and not be adversely affected begins from an amount shown in experimental animals not to cause an effect. From that experimental data point, several assumptions are used to build safety factors into the final value. Therefore, 2 µg/L of RDX in contaminated water represents an estimate of a safe level. If a person drinks less water, is exposed for only a few years, or is influenced by a number of other biological factors, the actual amount of RDX that would cause an adverse health effect might vary considerably. Because 2 µg/L is only a guideline, drinking water with higher levels of RDX contamination may or may not adversely affect health.

2,4,6-TRINITROTOLUENE (TNT)

During large-scale production of TNT during WWI, many workers in munitions factories died of TNTintoxication (43-45). With application of hygienic precautions (such as periodic hand-washing, routinechanges of protective clothing, and respiratory protection) to prevent inhalation exposure, fatalitiesdecreased. Liver disease and aplastic anemia were the primary causes of death. Absorption of TNTthrough the skin or lungs can produce cyanosis (lack of oxygen-carrying capacity of the blood), severeliver damage, anemia, cataract formation, CNS manifestations, and kidney damage. Although thoseeffects of TNT are well documented, they primarily result from exposure by way of inhalation and notthrough ingestion of contaminated drinking water, as may occur at CAAP.

Long-term, low-dose TNT-ingestion studies have been carried out in mice, rats, and dogs (46-48). Athigher doses in mice and rats (10-70 mg/kg body weight/day), over a 24 to 26-week period,hematological signs of anemia and liver damage were noted. When dogs were fed TNT (0.5, 2, 8, or32 mg/kg body weight/day) over 26 weeks, liver damage was noted at all dosage levels (48). Increasedincidence of urinary bladder papilloma and carcinoma was found in female rats (46). Using this study,EPA classified TNT as a Group C chemical (possible human carcinogen) (43). The dog studies showedsimilarities to TNT effects in man and data from them were used to develop EPA Lifetime HA criteria(43).

Based on a Low Observed Adverse Effect Level (LOAEL) of a 0.5 mg/kg body weight/day dose, an RfD for RDX was determined. A DWEL was calculated and modified by considering drinking water as one of a number of potential sources of contamination and by an additional uncertainty factor based on the limited evidence of carcinogenicity. This resulted in an EPA Lifetime HA for TNT of 0.002 mg/L or 2 µg/L. Similar water quality criteria have been developed by other agencies and compared to the EPA Health Advisory (49, 50).

OCTAHYDRO-1,3,5,7-TETRANITRO 1,3,5,7-TETRAZOCINE (HMX)

Little information is available about human exposure to HMX. Health effects of HMX were studiedin explosive plant workers, but results were inconclusive because HMX was a contaminant of otherproducts, e.g., TNT and RDX (see RDX discussion and 33). Some dermal toxicity following exposureto HMX was noted (51).

Few animal studies have been performed to determine the health effects of HMX. In a 14-day study of rats fed high doses (9,000 mg/kg body weight/day) of HMX, pathological changes in liver were noted (52). In a 14-day mouse study, CNS effects were seen at 100 mg/kg body weight/day (53). In a more chronic study over 13 weeks, rats were fed HMX at doses between 50 and 1,500 mg/kg body weight/day. Pathological changes in the liver were seen at 450 mg/kg body weight/day (54). The NOAEL was 50 mg/kg body weight/day. EPA used that study to calculate a Lifetime HA. The HA level is 0.35 mg/L, or rounded off to 400 µg/L. HMX is classified as a Class D chemical (not classified as to human carcinogenicity) because no studies have been performed to address its carcinogenicity.

1,3-DINITROBENZENE (DNB)

Data about health effects after exposure to DNB are limited. Six workers exposed to an unknownconcentration of 1,3-DNB dust developed cyanosis that began within one day of exposure and lastedtwo weeks (55). Health effects also included anemia accompanied by palpitations, dizziness, andfatigue. Anemia persisted an average of 3 days. Follow-up examinations over a 10-year period did notreveal any adverse health effects. Well-documented health effects in animals include toxic effectsresulting in death and pathological effects on the liver, spleen, and testes. These effects resulted inweight loss, anemia, and decreased reproductive capacity (56-59). Some evidence of increased toxicityin older (as compared to younger) animals was noted (58). A 16-week study of ingestion by rats of 1,3-DNB in drinking water used doses of 0.4-1.14 mg/kg body weight/day (59). Based on splenic andtesticular effects, a dose of 0.4 mg/kg body weight/day was established as the NOAEL. From thatvalue, EPA developed a lifetime H A of 1 µg/L (60). High uncertainty factors were included becauseof lack of long-term studies. DNB is considered a Class D chemical (not classified as to humancarcinogenicity) because of lack of information about its carcinogenicity.

1,3,-TRINITROBENZENE (TNB)

No information is available on the health effects of TNB. Because of its structural similarity to DNB, assumptions are made that its health effects might be similar to those caused by DNB. Using the experiment described for DNB (59), EPA has developed a Lifetime H A for TNB. Because of the uncertainty of using DNB studies to develop guidelines for TNB, additional safety assumptions were included in the calculations. As a result, the livetime H A for TNB is 0.1 µg/L, which is 10 times less than that for DNB (61).

1,1-DICHLOROETHENE (DCE)

The scientific literature contains information about human and laboratory animal exposure to DCE. DCE is toxic to both humans and laboratory animals (62). Human exposure to DCE occurs primarily in the industrial work environment and at areas in and around hazardous waste sites. Most available information on adverse health effects associated with DCE exposure in humans comes from reports of accidental exposure to high concentrations for short periods. Repeated exposure to high levels may be associated with liver damage. Exposure by breathing DCE appears to be more harmful than exposure by way of food or water. EPA has established a long-term drinking water health advisory of 7 µg/L, below which DCE in water may not cause health effects. DCE is classified by EPA as a group C chemical agent (a possible human carcinogen) because information about its carcinogenicity is not complete.

1,2-DICHLOROETHANE (DCA)

Acute exposure to DCA occurs primarily by inhalation or by ingestion (63). Exposure to high levels can cause irregular beats which may lead to heart damage. Liver, lung, and CNS damage may also occur after acute exposure. Exposure to lower levels can result in eye irritation, cough, and bronchitis. Little information is available about long-term, low-dose exposure. In animal experiments, exposure to DCA has been associated with tumors of the liver, pancreas, adrenal glands, stomach, breast, and lung. EPA has established a child longer term health advisory for drinking water of 700 µg/L. DCA is classified by EPA as a probable carcinogen.

TRICHLOROETHYLENE (TCE)

Trichloroethylene is a man-made chemical used primarily as a solvent to remove grease, or for production of other chemicals. Animal studies of TCE in drinking water have shown health effects that include liver and kidney toxicity and fetal damage (64). Using animal studies, EPA has established a drinking water standard of µg/L for TCE. No determination about the carcinogenicity of TCE has been made.

NITRATES

Nitrates are not considered to be directly toxic at concentrations less than 1000 mg/L. In some people,however, nitrates can be reduced in the body to nitrites (65). Nitrites are known to causemethemoglobinemia in infants (66). Methemoglobinemia is the condition in which hemoglobin bindsinefficiently with oxygen and can result in cyanosis, which is a bluish discoloration of the skin and lips.Methemoglobinemia in infants rarely occurs when the concentration of nitrates in drinking water is lessthan 10 mg/L. The region where CAAP is located has a problem with nitrates in drinking water;occasionally, levels of nitrates greater than the MCL of 10 mg/L are found in Grand Island city wells.

B. Health Outcome Data Evaluation

ATSDR reviewed existing cancer rates for Hall County. No significant differences between cancer ratesin Hall County and Nebraska as a whole were seen (see Appendix). No information is available oncancer rates in the specific population of interest (persons living in residences around CAAP who areexposed to contaminated drinking water). Therefore, the crude rates may not reflect an accurate pictureof the incidence in the area. Demographics information on that population at the level needed todetermine whether there is a health impact from hazardous wastes at CAAP is not available. Specificdemographic information will be obtained through future health studies as determined by the HealthActivities Recommendation Panel of ATSDR (see Recommendations section).

C. Community Health Concerns Evaluation

Following are ATSDR's responses to each of the community concerns about health:

What are the health effects of RDX, and what is a safe level of RDX in drinking water? Whatis the risk of getting cancer from drinking RDX-contaminated water?

Most of the information available about the health effects of RDX in humans concerns exposure ofmunitions plant workers to RDX by way of inhalation of powdered explosive. Severe health effects ofthe central nervous system (CNS) resulting in seizures have been seen. The approximate amount ofRDX that caused seizures in a small child after accidental ingestion was more than 3,000 times theamount of RDX found in a liter of drinking water (the highest amount found) in the CAAP area. Noscientific information is available concerning the long-term effects on humans drinking RDX-contaminated water. EPA has estimated safe drinking water levels using information on the observedeffects of RDX in experimental animals. That amount has been calculated to be 2 µg/L.

Liver carcinomas and adenomas have been seen in RDX-exposed laboratory animals. Otherexperiments, however, clearly show no carcinogenic potential of RDX. Because of the lack ofconclusive information, EPA has classified RDX as a possible carcinogen.

What are the health effects of TNT and other contaminants that may be in the contaminateddrinking water? What are safe levels for those contaminants in drinking water?

The situation with TNT is much the same as with RDX. Information about human health effects causedby TNT is primarily available from documented health effects in ammunition plant workers. Severeliver disease and anemia have been seen; however, most symptoms cleared after removal of the exposuresource. Because those effects resulted from inhalation of explosive powder, they may or may not berelevant to the question about health effects associated with long-term ingestion through drinking water. Animal studies have been used to determine long-term drinking water effects. Anemia and liver diseasewere the primary effects. EPA has used those studies to determine guidelines for safe drinking waterstandards; the estimated amount is 2 µg/L (based on 70 years' exposure). Few data are available aboutVOCs in the groundwater. Further analysis for VOCs will be included in future sampling periods. Health effects of other contaminants, such as VOCs, are discussed in the Toxicologic Evaluation section.

Does RDX accumulate in cattle that drink contaminated water?

No experimental information is available about the accumulation of RDX or other explosivescontaminants in the meat of cattle. Studies in rats that have ingested high levels of RDX have shownminimal accumulation in fat (40). Calculations using those studies and assuming various otherparameters suggest that the levels of explosives in the drinking water of cattle around CAAP are nothigh enough to be of concern (20). That type of information, however, is not as useful as would be awell-designed study to determine actual amounts of contaminants in selected animals from the feedlotadjacent to CAAP. Using present information, however, and considering that contaminants in meatwould not all be consumed by a single person for an extended amount of time, the exposure of cattle tocontaminated drinking water probably does not pose a threat to human health. However, CAAP hasmade the city's water supply available to the feedlots. Using the city water supply for watering livestockwould eliminate the possibility of accumulation of contaminants in cattle.

Does RDX accumulate in crops irrigated with contaminated water?

In terms of human health, the accumulation of RDX in crops is probably more crucial thanaccumulation in cattle. Commercial crops, even if they do accumulate RDX, would not pose much ofa threat because they would be distributed to various feedlots or to different human markets. Oneperson would not be continuously exposed to a concentrated source of RDX. On the other hand, if RDXaccumulated in plants in a private garden, a greater threat would exist. Plants would be eaten by thesame people over an extended period of time. Two research studies have been performed to address thequestion of accumulation of RDX and TNT in plants (28, 29). TNT has been found to absorb to the soilas well as be taken up by plants. Plants can assimilate TNT from the soil, however, TNT is then brokendown into several metabolic products by the plants. The health effects of those compounds are notknown. The majority of TNT remains in the root of the plant. Findings by the same research groupwere different for RDX. RDX was shown to accumulate in the soil much less readily than TNT, butwas also not broken down as rapidly. Plants, including bush bean and wheat efficiently absorbed RDX. RDX was also more mobile in plants than was TNT. The highest concentrations of RDX were foundin the seeds of the bush bean plants; concentrations as high as 600 µg/g (ppm) of seeds were found. Those findings are surprising compared to plant accumulation rates of some other chemicals. In August,1991, CAAP began sampling vegetables and soil from residential gardens as well as soil from yardsirrigated with RDX- and TNT-contaminated water. Results from the vegetable sampling indicate thatRDX and TNT were not detected above the 0.19 ppm health risk detection limit (see EnvironmentalContamination and Other Hazards section) (19). The number of samples and the design of the studywere limited; no highly contaminated vegetables were found. Because of remaining uncertainties,however, ATSDR recommends that vegetable gardens be watered only with city water (or some othersource of uncontaminated water).

Should private well water be used in swimming pools?

Although exposure to RDX through skin at concentrations detected in private well samples in the areais unlikely, good practice would be to use only city water for swimming pools. That practice would alsocut down on incidental ingestion of contaminants while swimming.

What is the extent and exact location of the contaminated water plume? Does more than one plume exist?

To define a contamination plume, appropriate numbers and types of sampling wells must be placed atthe leading edge of the movement of the groundwater. Currently, the number and type of monitoringwells are not adequate for complete mapping of the plume. Although most of the contaminationprobably originated from the load lines, not enough information about the hydrogeology of the area isknown to evaluate individual plumes. Additional monitoring wells will be installed to further definethe movement of the contamination plume. Definition of the plume will help determine the need formonitoring drinking water wells used in the area.

Is the drinking water at Northwest High School contaminated?

The drinking water at Northwest High School was sampled in 1991 and tested for RDX, TNT, andother explosives. No contamination above EPA's 2 µg/L lifetime health advisory was seen. However,because Northwest High School is near areas with documented contamination, and the water hasnaturally high nitrate levels, school officials are in the process of obtaining water from the city.

Have all residential drinking water wells been tested?

A great number of water samples have been tested over the past few years. The Nebraska Departmentof Environmental Control has also completed a well survey to determine the location of all drinkingwater wells and those wells have now been included in a sampling plan. A comprehensive list andsampling results of all wells sampled, has not been completed. That information, presented in a mannerthat accurately places residential, monitoring, and agricultural wells, on a map is critical forunderstanding the human health implications of the contaminated groundwater.

Was the incineration of soil at CAAP successful in removing all the contamination?

The incineration program was successful in removing much of the explosives contamination in the targetareas. Because of the interference of high water tables during excavation, the extent of removal is notcertain. Further sampling to confirm any remaining contamination in those areas is needed.

What is the extent of contamination of buildings and soil on the installation itself?

The process of determining the extent of contamination in many of the study areas listed in Table 1 iscurrently in preliminary stages. Contaminants have been found in some soil samples, but not others;and the study is far from complete. To be certain that some areas do not contain hazardous materialsthat could contaminate the environment, a more comprehensive sampling program is underway as partof the RI/FS investigation.

D. Summary of Public Health Implications

This discussion has addressed specific health effects that may result from exposure (primarily byingestion) to specific chemicals, including explosives and volatile organic chemicals. In most cases, theeffects of long-term ingestion of those compounds are not known. The potential for adverse healtheffects, however, does exist. Government agencies have developed values to provide estimates of levelsat which no long-term adverse health effects would be expected. Because of the nature of thoseestimates (based on limited animal studies), conservative safety factors are included in the calculations. Therefore, consumption of contaminates in water at levels higher than the advisory values for someperiod of time will not, with certainty, result in adverse health effects. On the other hand, the avoidanceof contaminated water sources, regardless of the concentration of the contaminant, is the best way toprotect health.

The ability to detect health effects that might have occurred because of past exposure to chemicals inthe groundwater around CAAP is limited. Statistical databases that consider pertinent health anddisease information are not available.

The removal of contaminated soil at CAAP that was contributing to groundwater contamination wasan initial step in reducing spread of the contamination. Awareness of the public about health issuessurrounding the contamination and the ability to obtain uncontaminated water are important aspects of protecting of human health.


CONCLUSIONS

ATSDR considers contamination from CAAP a public health hazard because of long-term human exposures to hazardous substances. Evidence exists that exposures have occurred and are occurring. The estimated exposures are to a substance or substances at concentrations in the environment that, uponlong-term exposure, could cause adverse health effects to any segment of the nearby population. Thoseadverse health effects might be the result of either carcinogenic or noncarcinogenic toxicity from a chemical exposure.

  1. Environmental sampling of on-site soil has indicated contamination with explosives, metals, andvolatile organic compounds (VOCs). Sampling conducted to date is not adequate to determinethe extent of contamination around all areas of the post. Proposed sampling during the RI/FSincludes screening a large number of samples with field techniques. A percentage of thosesamples will be quantified for the same compounds using laboratory techniques. Furthersampling, using a more complete analyte list, will be performed on selected samples from the field sampling.
  2. Magazine storage areas are leased to the public, primarily for storage of household goods;families have access to the area. If the relatively limited access to the remainder of the postchanges as a result of increased tenant or other activity, concern for a public health threat wouldincrease. No sediment sampling has been conducted, but it is unlikely that large volumes orhigh concentrations of contaminants were discharged via surface runoff to off-site areas becausethe waste was originally concentrated in sumps. Sediment sampling and further soil samplingwill be conducted during the RI/FS. In addition to potential soil and sediment contamination,buildings contain asbestos and chipping lead paint. Further environmental sampling, to beperformed during the RI/FS, is necessary to determine the state of on-post property beforechanges in land use occur.

  3. Contamination of groundwater with explosives and possibly other undetermined compounds offpost has in the past and continues to pose a public health hazard. Groundwater, which is usedfor drinking and irrigation downgradient of CAAP, is contaminated, and the contaminationcontinues to spread. Groundwater on and off site is contaminated with explosives, nitrates, andpossibly VOCs. Past sampling analyses did not include all of the potential contaminants ofconcern. The proposed sampling includes VOCs, heavy metals, pesticides, and explosives. However, all of the biotransformation products and/or impurities associated with the explosivesare not currently listed for screening samples. Some of these compounds will be detected, however, as tentatively identified compounds.

  4. Neither the number of residents exposed nor the concentration of explosives and othercontaminants to which they were exposed by way of groundwater ingestion over time can beestimated with great accuracy. The groundwater samples were not analyzed for all of thecontaminants of concern; the sampling techniques varied; and the detection limits historicallywere too high. The problems with those evaluations have been partially alleviated by recently increased technical capability.

  5. Ingestion of contaminated meat or vegetables might represent a food chain pathway. A cattlefeedlot and a well are adjacent to CAAP in the area of groundwater contamination. No directscientific evidence is available to demonstrate at what concentrations explosives mightaccumulate in the fat or meat of cattle. Available information from laboratory animal studiesshows little accumulation occurs. No evidence exists supporting the idea that corn or cattlewould accumulate concentrations of explosives that would cause an acute toxic effect in peopleingesting those foods over a short periods. On the other hand, no sampling studies or controlledlaboratory experiments in cattle have been performed to show whether or not explosivesaccumulation may occur when cattle drink water containing explosives at the concentrations found in groundwater in the CAAP area.
  6. Vegetables from a garden irrigated with contaminated water (especially RDX-contaminated)eaten by a single family over an extended period of time are a potential health threat. A recentlaboratory study has shown RDX accumulation in plants, including distribution, withoutmetabolic breakdown, into seeds. Concentrations may not be expected to be high enough tocause acute toxic effects after short-term ingestion, but may be a cause for concern over anextended period. Discussions took place among ATSDR, USATHAMA, EPA, NDEC, andNDH concerning possible vegetable contamination, and, in August, 1991, CAAP begansampling vegetables and soil from residential gardens, as well as soil from yards irrigated withRDX- and TNT-contaminated water. Results from the vegetable sampling indicate that RDXand TNT were not detected at levels above the 0.19 ppm health risk value established forconsumption of vegetables.

    If lawns are watered with contaminated water, any potential health effects would be related tosoil exposure. Analyses of soil samples taken in September, 1991, indicated no contaminationwith RDX.

  7. Inconsistencies in groundwater sampling procedures, frequency, QA/QC, and parameters rendersome results questionable. Limited information about well construction adds to the conclusionthat extent of contamination has not been adequately defined.

  8. Available sampling data were poorly organized and difficult to interpret. Groundwater plumemaps do not depict contamination in relation to stationary objects, such as roads or buildings. The available maps are confusing and would be difficult to use for decision making. Wellsurvey information failed to adequately determine which residents are currently drinking fromprivate wells in or near the contamination plume. Most residents have accepted connection tocity drinking water, but a recent survey indicated that some residents may still be drinkingcontaminated water. CAAP sampled 10 residences on O'Flannagan, O'Grady, and North Webbstreets in July, 1991, as part of the periodic check on groundwater plume movement. Theanalyses showed that six of the 10 were above or close to the 2 ppb action limit. CAAP willprovide those residents with an alternative water supply and will periodically check other areasto determine if alternative water supplies are necessary. Information has not been obtained about other uses of private well water, such as for swimming pools, gardens, or lawns.

  9. Findings indicate that groundwater contamination from nitrates originates from various sources,including animal waste, nitrogen-based fertilizers, and, possibly, sources at CAAP. Accordingto the CAAP RI/FS workplan, private wells and monitoring wells will be monitored for nitrate contamination.

RECOMMENDATIONS

  1. Currently, magazine areas at CAAP are leased to individuals for storage. Access to those areasis not limited, and visitors may include families with children. Because of the potential foringestion of contaminated soil, ATSDR recommends limiting the public's access (especiallychildren) to the areas until the extent of contamination is further characterized during the RI/FS.

  2. Currently, potential exposure of workers or others to contaminants in most areas of the post islimited. If human activities at CAAP increase, health concerns will increase. RI/FS fieldworkat CAAP began in December, 1991, to characterize the extent of contamination around thenitrate production area, shop area, and load lines. Although the proposed sampling plan isextensive, ATSDR recommends that the analyte list proposed for the final phase two samplingbe applied during the laboratory confirmation phase of the field-tested samples. Selectedadditional analytes from Table 5 should also be considered for inclusion.
  3. Determining contaminant concentrations in the top three inches of soil is important forevaluating the potential for human exposure by way of ingestion, inhalation, and dermalcontact. ATSDR recommends evaluating the results of sampling before changes in land use orhuman activity take place at CAAP.

  4. ATSDR recommends continued monitoring of wells used for drinking water. Monitoringshould be systematically conducted at drinking water wells close to currently defined areas ofgroundwater contamination. Continued, systematic surveillance of private well use and ofdevelopment of new wells in locations adjacent to the affected area should be established. Institutional controls should be implemented to prevent future well construction in affected areas.

  5. Information should be obtained about accumulation of RDX, TNT, and HMX in cattle thatdrink water containing those contaminants. That information could be obtained from controlledlaboratory experiments or field feedlot studies. CAAP has made the city's water supplyavailable to the feedlots; that supply should be used for watering livestock to eliminate thepossibility of contaminant accumulation in cattle until additional studies show thataccumulation of those contaminants is not likely.
  6. Additional sampling of vegetables, including crops grown at CAAP, is planned during the RI/FSprocess and should be carried out to further define uptake of explosives in plants. Until thatsampling is complete, and the results evaluated, vegetable gardens previously watered withcontaminated well water should only be watered with city water (or some other source ofuncontaminated water). Future sampling of vegetables and soils should be performed (becauseof the possibility of residual soil contamination) to further ensure the safety of vegetables fromgardens even after use of city water for gardens begins.

    ATSDR recommends monitoring currently used on- and off-site irrigation wells.

    The use of explosives-contaminated water for on-site crop irrigation should be discontinueduntil additional studies show that crops are not affected.

  7. Although adverse health effects resulting from dermal (skin) exposure to RDX at concentrationsdetected in private well samples in the area are unlikely, a cautious approach would be to useonly city water in swimming pools. That approach would also eliminate incidental ingestion of contaminants while swimming.

  8. Data, both past and current, should be organized in a concise format that can be used by thepublic, including owners of private wells and elected officials, to understand current and futuredrinking water issues. That organization is crucial so that individuals can make their own decisions about issues that have a direct effect on health.

  9. Private well users should be informed that a regional nitrate contamination problem exists andthat, although water samples may not show contamination from explosives or other CAAP-related contaminants, nitrate levels above 10 ppm exceed EPA's MCL.

  10. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of1980, as amended, requires ATSDR to perform public health actions needed at hazardous wastesites. To determine if public health actions are needed, ATSDR's Health ActivitiesRecommendation Panel (HARP) has evaluated the data and information developed in theCornhusker Army Ammunition Plant Public Health Assessment. Community health educationhas been conducted by the Nebraska Department of Health, the Nebraska Department ofEnvironmental Control, and the U.S. Army through various public meetings andcommunications. To assist in evaluation of health effects caused by exposure to RDX, HARPhas requested a technical consultation on RDX biomarkers. Because people might have beenexposed to RDX or other contaminants at levels that could cause illness, HARP determined thatsite-specific surveillance and disease- and symptom-prevalence studies are needed as follow-up health activities.

PUBLIC HEALTH ACTIONS

The public health action plan (PHAP) for the Cornhusker Army Ammunition Plant NPL site containsa description of actions to be taken by ATSDR and/or other governmental agencies at and in the vicinityof the site subsequent to the completion of this public health assessment. The purpose of the PHAP isto ensure that this public health assessment not only identifies public health hazards, but provides a planof action designed to mitigate and prevent adverse human health effects resulting from exposure tohazardous substances in the environment. Included is a commitment on the part of ATSDR to followup on this plan to ensure that it is implemented. The public health actions to be implemented are asfollows:

A. Actions Undertaken

  1. CAAP has provided the area community with alternate water supplies (bottled water andconnections to municipal water supplies) for potable use when contamination was detected in residential wells.

  2. CAAP, USATHAMA, EPA, NDEC, NDOH, and ATSDR held discussions concerningincorporation of explosives into plants. Those discussions resulted in the notification of thecommunity of the concern and the sampling of vegetables and soils in the plume area. Althoughdata did not indicate acute public health concern, NDEC, NDOH and ATDSR recommendedcontinued use by residents of city water for yards and gardens.

B. Actions Planned

  1. CAAP, USATHAMA, EPA, NDOH, NDEC, and ATSDR will continue to provide pertinentinformation to the community about exposure to hazardous substances associated with the site.

  2. ATSDR will conduct a symptom and disease study, biological medical testing and site-specific surveillance in the community living near the site.

  3. CAAP will perform further field studies to evaluate the potential for uptake of contaminants into plants from contaminated irrigation water. This will be carried out during the RI/FS process.

  4. ATSDR will provide an annual follow-up to this PHAP, outlining the actions completed and those in progress. That report will be placed in repositories that contain copies of this public health assessment, and will be provided to persons who request it.

ATSDR will reevaluate and expand the PHAP when needed. New environmental, toxicological, orhealth outcome data, or the results of implementing the above proposed actions may determine the need for additional actions at the CAAP site.


PREPARERS OF REPORT

Environmental Assessor:
Diane Jackson
Chemical Engineer
Defense Facilities Assessment Section
Federal Programs Branch

Health Effects Assessor:
Gary H. Campbell, Ph.D.
Environmental Health Scientist
Defense Facilities Assessment Section
Federal Programs Branch

ATSDR Regional Representatives:
David Parker
ATSDR, EPA Region VII, Kansas City, MO

Roberta Erlwein
ATSDR, EPA Region VII, Kansas City, MO


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  38. Hart ER. Two-year feeding study in rats. 1977; AD A040161. Litton Bionetics, Inc.,Kensington, MD. Office of Naval Research, Contract No. N00014-73-C-0162.

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  40. U.S. Environmental Protection Agency, Criteria and Standards Division, Office of DrinkingWater, 1988; Health Advisory for Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX).

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FIGURES

General Location of Cornhusker Army Ammunition Plant
Figure 1. General Location of Cornhusker Army Ammunition Plant

Environmental Study Areas, Cornhusker Army Ammunition Plant
Figure 2. Environmental Study Areas, Cornhusker Army Ammunition Plant

Soil Map of Hall County, Nebraska
Figure 3. Soil Map of Hall County, Nebraska

RDX Area Map
Figure 4. RDX Area Map


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