PUBLIC HEALTH ASSESSMENT
CORNHUSKER ARMY AMMUNITION PLANT
GRAND ISLAND, HALL COUNTY, NEBRASKA
To determine whether nearby residents are exposed to contaminants migrating from a site, ATSDR evaluates the environmental and human components that lead to human exposure. This pathways analysis consists of five elements: source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure (for example, dermal contact or ingestion), and an exposed population.
ATSDR identifies exposure pathways as completed, potential, or eliminated. For a completed pathway to 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 one of the five elements is missing, but could exist. Potential pathways indicate that exposure to a contaminant could have occurred, could be occurring, or could occur in the future. Pathways are eliminated when at least one of the five elements is missing and will never be present.
A. Completed Exposure Pathways
Past, current, and future exposure pathways are possible by way of ingestion of contaminated groundwater from private wells. Waste sources at the site appear to be responsible for contamination of groundwater near CAAP and Capital Heights. A major waste source was removed and remediated in 1987, when approximately 44,000 tons of soil were incinerated. However, the groundwater contamination plume is moving northeasterly at approximately 75 to 827 ft/year. Historically, between 464 and 800 household drinking water supplies were affected or potentially affected (1). CAAP began sampling in 1982 and detected high concentrations of explosives in groundwater. Because local soils are highly permeable, it is likely that groundwater contamination began when the installation initiated surface discharge of contaminants. In January, 1984, CAAP provided bottled water to approximately 264 residents whose well-water contained RDX concentrations greater than 35 ppb. CAAP then extended the Grand Island water supply line to the Capital Heights area and offered residents the opportunity to use that drinking water source. The Grand Island water supply is not (and likely never will be) considered a potential pathway.
A recent survey conducted by the City of Grand Island Utilities Department reported that five residences chose 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 private wells have been sampled recently. In addition, some residents live outside the area accessible to the city water connection, but near the contaminated groundwater plume. CAAP sampled private well water from 10 residences on O'Flannagan, O'Grady, and North Webb streets in July, 1991. The analyses showed that water from six of the ten wells contained concentrations of RDX greater than or close to the 2 ppb action limit. The six concentrations ranged from 1.92 to 4.63 ppb. CAAP provided those residents with an alternative water supply and planned to periodically check other areas to determine if an alternative water supply is necessary (12). Further study of the area resulted in a proposal to extend permanent water supplies (26). The proposal and public comment period (August 24-September 24, 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, and swimming pools. In addition, commercial irrigation wells used for crop irrigation and animal watering are still operating. Recent information indicates that plants can efficiently absorb RDX. ATSDR discussed that information with USATHAMA, EPA, NDEC, and NDH and recommended stopping use of contaminated water for irrigation of private vegetable gardens. On July 30, 1991, NDEC and NDH advised residents not to eat vegetables grown in gardens irrigated with water from private wells. In addition, NDEC and NDH recommended that residents stop using private wells for garden irrigation and stop using as compost grass clippings from lawns irrigated with private well water. ATSDR attended a public meeting sponsored by the state agencies on August 5, 1991, to discuss the new information 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 water samples historically have not included all potential contaminants; therefore, ATSDR is unable to evaluate all of the contaminants to which people could have been exposed. Groundwater plume location and 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 to determine. Capital Heights is approximately two miles from the CAAP boundary. Estimating the plume migration at an average 400 ft/yr up to 800 ft/yr, the first contaminants could have taken between 13 and 26 years to reach the affected private wells. CAAP began operating in the 1940s and the Capital Heights subdivision was developed in the early 1960s. The contamination might have already reached the private wells when the subdivision was developed. Residents using those wells could have been exposed 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 CAAP continued 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 is available on numbers of persons who might be exposed to contaminants.
Until more information becomes available, ATSDR cannot further assess those pathways or their importance.
Air releases probably occurred from the 1940s until the mid 1970s, during open burning of waste explosives, solvents, oils, and other debris. Particulates and vapors associated with the burning represent a past completed pathway to workers and nearby residents by way of inhalation. Prevailing winds are from the south in the summer and from the northwest in the winter. Summer winds are usually moderate to strong (1). The closest housing area is approximately one-half mile northwest and three miles east. Although it is unlikely that critical concentrations of hazardous materials reached those areas, no air sampling data were available from that period to thoroughly evaluate the pathway.
Past, current, and future exposure pathways are possible because of contamination present in surface soils on site. Former employees, current tenants, and remedial workers could have been or are being exposed to some level of contaminants by way of ingestion, inhalation, or skin contact with contaminated surface soils. Limited surface soil sampling has been conducted, and current employees and tenants have access to many of the potentially contaminated on-site areas. A major remediation effort to remove contaminated soil took place in 1987. The extent of the remaining contamination has not 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 as 1,460 ppm. That area has not been thoroughly characterized and hazardous substances may be in or around individual magazine areas. Many current tenants use those areas and sometimes bring their children on post; thus, a possible exposure pathway exists. Restricting access would eliminate the exposure.
The eastern channel, western channel, and the railroad ditch accumulate runoff from the site, and, when flowing, eventually discharge to Silver Creek. Those three primary collectors of surface runoff could have transported contaminants into sediments and surface waters. No sampling has been conducted to verify that exposure pathway. Access to Silver Creek is unrestricted. Sampling is planned for the ditches as part of the RI/FS. Because most of the contamination was discharged into collection sumps and transferred to the leach pits, large volumes or high concentrations of waste probably were not transported off site by the ditches.
Past, current, and future exposure pathways are possible by way of ingestion of contaminated cattle and crops. Irrigation wells are used to water animals and crops both on and off site. Several irrigation wells contain 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 vegetable contamination, and, in August 1991, CAAP began sampling vegetables and soil from residential gardens as well as soil from yards irrigated with RDX- and TNT-contaminated water. As described in the 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 not been 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 enough to cause acute adverse health effects after eating meat or vegetables for a short period. For significant exposure to occur over a long period, the food source would have to continuously contain contaminants at concentrations above health-based risk levels. Generally, families eat meat obtained from several suppliers rather than from a single source. Therefore, the chances that a family would ingest contaminated meat over an extended period would be low. If a family regularly obtained their meat from 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 long period of time a family relied on its own gardens (watered with contaminated water), or on a roadside vegetable stand that sold vegetables from the same source (watered with contaminated water), the amount of exposure might be of concern. CAAP has made the city's water supply available to the feedlot areas. Using the city water supply for watering livestock would eliminate the possibility of contaminant accumulation in cattle.
C. Summary of Pathways Analysis
The private well pathway is considered complete because exposure to some level of contaminants has occurred via ingestion and skin contact. People exposed include residents drinking contaminated private well 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 to contaminants could result from ingestion of contaminated food. Past inhalation of contaminants might have 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. |
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 specific community health concerns.
To understand health effects that may be caused by a specific chemical, several factors related to the interaction of the chemical with the individual must be considered. Health effects caused by a specific chemical 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 severity of health effects. Health effects are related not only to the dose to which the person is exposed, but to the amount of chemical that the body actually absorbs. The manner in which a specific chemical is absorbed, metabolized or otherwise broken down by natural body mechanisms also determines the type of health effects that may result.
To determine the possible health effects produced by specific chemicals, ATSDR considers the previously discussed factors as described in the scientific literature. Compilation by ATSDR of this information has resulted in a number of chemical-specific ATSDR documents called toxicological profiles. Toxicological profiles are used for guidance in determining concentrations of specific chemicals in 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, or chronic). When toxicological profiles are not available for a certain chemical, we review various sources, 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 people have been exposed or are now being exposed. This section will discuss the health effects that may be caused by those chemicals. Those chemicals have been found on post in soil and groundwater as well as in groundwater off post. Because little human exposure to contaminated soil is believed to be taking place 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 plant workers exposed to RDX dust by way of inhalation. Effects have included insomnia, restlessness, irritability, disorientation, epileptiform seizures (convulsions), and unconsciousness (30). Workers in the report were exposed to finely powdered RDX dust; absorption was probably by inhalation. All generally recovered within one day. No abnormalities were observed in workers' blood or urine. When exposure was prevented by hygienic measures, no further adverse effects were seen. Health effects from exposure to smoke when RDX-containing plastic explosives were burned to heat food were also seen in U.S. soldiers in Vietnam (31, 32). Symptoms of central nervous system (CNS) toxicity, ranging from confusion 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 determine abnormalities of the hematologic, hepatic, and renal systems. Of 93 workers with varying degrees of exposure, no abnormal findings or presence of autoimmune disease were observed. No symptoms of acute central nervous system toxicity were seen (33).
Acute CNS toxicity has also been seen after ingestion of RDX-containing material. Reports of soldiers in Vietnam eating RDX for purported hallucinogenic effects document generalized convulsions and states of consciousness varying from coma to lethargy. Moderate changes in liver and kidney function were observed. No fatalities resulted, and mental capacity and other changes returned to normal within 10-30 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 resulted in convulsive CNS symptoms, but no long-lasting liver or kidney damage (36). The child ingested RDX from plastic explosive brought home on the contaminated clothing of his mother, who worked in a munitions plant.
The reports described here provide information about severe health effects after acute inhalation or ingestion of RDX. However, because the routes of exposure and the doses vary from the situation found at CAAP, the data do not adequately address possible chronic health effects of long-term exposure to RDX in drinking water. When adequate studies in humans are not available, studies in animals must be 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 highest doses 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 inflammation of the prostate. Inflammation of the prostate was seen at 1. mg/kg body weight/day, but not at 0.3 mg/kg body weight/day (39). Testicular degeneration was seen in mice receiving 35 mg/kg body weight/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 found no evidence of carcinogenicity (38, 39). The combined incidence of hepatocellular carcinomas and adenomas was significantly increased compared to control animals in female mice receiving 7, 35, and 100 mg RDX/kg body weight/day over a two-year period (37). No significant increases were found at the 1.5 mg/kg body weight/day dose level. The increased rates of carcinomas and adenomas were not significant when considered separately.
Based on various criteria of sensitivity and completeness in animal studies, EPA has used certain studies to 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. For RDX, 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. An initial EPA guideline called the No Observed Adverse Effect Level (NOAEL), for RDX is the dose of 0.3 mg/kg body weight/day.
The next guideline is the EPA Reference Dose (RfD). A RfD is an estimate of a daily exposure to humans that is likely to be without appreciable risk of deleterious effects over a lifetime. The RfD starts with the NOAEL and modifies it through consideration of uncertainty factors derived from the EPA Office of Drinking Water guidelines which consider variations in experiments or species of animals used in 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 which adverse noncarcinogenic health effects would not be expected to occur. The DWEL considers the assumed body weight (70 kg) and the assumed daily water consumption (2 L/day) of an adult. The DWEL 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 HA represents that portion of an individual's total exposure attributed to drinking water and is considered protective of noncarcinogenic adverse health effects over a lifetime exposure. The HA for a chemical is a concentration in drinking water at which adverse health effects would not be anticipated and which includes a margin of safety to protect the most sensitive members of the population at risk (40). An HA is calculated from the DWEL with the consideration that drinking water may not be the only source of exposure. If data are not available, a factor of 20% is used. For chemicals, such as RDX, that have been 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 are considered, the EPA Lifetime Health Advisory for RDX is 0.002 mg/L or 2 g/L (i.e., 2 parts per billion [ppb]). Similar water quality criteria for RDX have been calculated by others and compared to the 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 TNT intoxication (43-45). With application of hygienic precautions (such as periodic hand-washing, routine changes of protective clothing, and respiratory protection) to prevent inhalation exposure, fatalities decreased. Liver disease and aplastic anemia were the primary causes of death. Absorption of TNT through the skin or lungs can produce cyanosis (lack of oxygen-carrying capacity of the blood), severe liver damage, anemia, cataract formation, CNS manifestations, and kidney damage. Although those effects of TNT are well documented, they primarily result from exposure by way of inhalation and not through 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). At higher 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, or 32 mg/kg body weight/day) over 26 weeks, liver damage was noted at all dosage levels (48). Increased incidence 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 showed similarities 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 studied in explosive plant workers, but results were inconclusive because HMX was a contaminant of other products, e.g., TNT and RDX (see RDX discussion and 33). Some dermal toxicity following exposure to 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 unknown concentration of 1,3-DNB dust developed cyanosis that began within one day of exposure and lasted two weeks (55). Health effects also included anemia accompanied by palpitations, dizziness, and fatigue. Anemia persisted an average of 3 days. Follow-up examinations over a 10-year period did not reveal any adverse health effects. Well-documented health effects in animals include toxic effects resulting in death and pathological effects on the liver, spleen, and testes. These effects resulted in weight loss, anemia, and decreased reproductive capacity (56-59). Some evidence of increased toxicity in 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 and testicular effects, a dose of 0.4 mg/kg body weight/day was established as the NOAEL. From that value, EPA developed a lifetime H A of 1 µg/L (60). High uncertainty factors were included because of lack of long-term studies. DNB is considered a Class D chemical (not classified as to human carcinogenicity) 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 cause methemoglobinemia in infants (66). Methemoglobinemia is the condition in which hemoglobin binds inefficiently 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 less than 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 rates in Hall County and Nebraska as a whole were seen (see Appendix). No information is available on cancer rates in the specific population of interest (persons living in residences around CAAP who are exposed to contaminated drinking water). Therefore, the crude rates may not reflect an accurate picture of the incidence in the area. Demographics information on that population at the level needed to determine whether there is a health impact from hazardous wastes at CAAP is not available. Specific demographic information will be obtained through future health studies as determined by the Health Activities 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? What is 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 of munitions plant workers to RDX by way of inhalation of powdered explosive. Severe health effects of the central nervous system (CNS) resulting in seizures have been seen. The approximate amount of RDX that caused seizures in a small child after accidental ingestion was more than 3,000 times the amount of RDX found in a liter of drinking water (the highest amount found) in the CAAP area. No scientific 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 observed effects 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. Other experiments, however, clearly show no carcinogenic potential of RDX. Because of the lack of conclusive information, EPA has classified RDX as a possible carcinogen.
What are the health effects of TNT and other contaminants that may be in the contaminated drinking 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 caused by TNT is primarily available from documented health effects in ammunition plant workers. Severe liver disease and anemia have been seen; however, most symptoms cleared after removal of the exposure source. Because those effects resulted from inhalation of explosive powder, they may or may not be relevant 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 disease were the primary effects. EPA has used those studies to determine guidelines for safe drinking water standards; the estimated amount is 2 µg/L (based on 70 years' exposure). Few data are available about VOCs 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 explosives contaminants in the meat of cattle. Studies in rats that have ingested high levels of RDX have shown minimal accumulation in fat (40). Calculations using those studies and assuming various other parameters suggest that the levels of explosives in the drinking water of cattle around CAAP are not high enough to be of concern (20). That type of information, however, is not as useful as would be a well-designed study to determine actual amounts of contaminants in selected animals from the feedlot adjacent to CAAP. Using present information, however, and considering that contaminants in meat would not all be consumed by a single person for an extended amount of time, the exposure of cattle to contaminated drinking water probably does not pose a threat to human health. However, CAAP has made the city's water supply available to the feedlots. Using the city water supply for watering livestock would 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 than accumulation in cattle. Commercial crops, even if they do accumulate RDX, would not pose much of a threat because they would be distributed to various feedlots or to different human markets. One person would not be continuously exposed to a concentrated source of RDX. On the other hand, if RDX accumulated in plants in a private garden, a greater threat would exist. Plants would be eaten by the same people over an extended period of time. Two research studies have been performed to address the question of accumulation of RDX and TNT in plants (28, 29). TNT has been found to absorb to the soil as well as be taken up by plants. Plants can assimilate TNT from the soil, however, TNT is then broken down into several metabolic products by the plants. The health effects of those compounds are not known. The majority of TNT remains in the root of the plant. Findings by the same research group were different for RDX. RDX was shown to accumulate in the soil much less readily than TNT, but was 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 found in 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 yards irrigated with RDX- and TNT-contaminated water. Results from the vegetable sampling indicate that RDX and TNT were not detected above the 0.19 ppm health risk detection limit (see Environmental Contamination and Other Hazards section) (19). The number of samples and the design of the study were 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 other source 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 area is unlikely, good practice would be to use only city water for swimming pools. That practice would also cut 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 at the leading edge of the movement of the groundwater. Currently, the number and type of monitoring wells are not adequate for complete mapping of the plume. Although most of the contamination probably originated from the load lines, not enough information about the hydrogeology of the area is known to evaluate individual plumes. Additional monitoring wells will be installed to further define the movement of the contamination plume. Definition of the plume will help determine the need for monitoring 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, and other 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 has naturally 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 Department of Environmental Control has also completed a well survey to determine the location of all drinking water wells and those wells have now been included in a sampling plan. A comprehensive list and sampling results of all wells sampled, has not been completed. That information, presented in a manner that accurately places residential, monitoring, and agricultural wells, on a map is critical for understanding 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 target areas. Because of the interference of high water tables during excavation, the extent of removal is not certain. 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 is currently 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 materials that could contaminate the environment, a more comprehensive sampling program is underway as part of the RI/FS investigation.
D. Summary of Public Health Implications
This discussion has addressed specific health effects that may result from exposure (primarily by ingestion) to specific chemicals, including explosives and volatile organic chemicals. In most cases, the effects of long-term ingestion of those compounds are not known. The potential for adverse health effects, however, does exist. Government agencies have developed values to provide estimates of levels at which no long-term adverse health effects would be expected. Because of the nature of those estimates (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 some period of time will not, with certainty, result in adverse health effects. On the other hand, the avoidance of contaminated water sources, regardless of the concentration of the contaminant, is the best way to protect health.
The ability to detect health effects that might have occurred because of past exposure to chemicals in the groundwater around CAAP is limited. Statistical databases that consider pertinent health and disease information are not available.
The removal of contaminated soil at CAAP that was contributing to groundwater contamination was an initial step in reducing spread of the contamination. Awareness of the public about health issues surrounding the contamination and the ability to obtain uncontaminated water are important aspects of protecting of human health.
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, upon long-term exposure, could cause adverse health effects to any segment of the nearby population. Those adverse health effects might be the result of either carcinogenic or noncarcinogenic toxicity from a chemical exposure.
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 post changes as a result of increased tenant or other activity, concern for a public health threat would increase. No sediment sampling has been conducted, but it is unlikely that large volumes or high concentrations of contaminants were discharged via surface runoff to off-site areas because the waste was originally concentrated in sumps. Sediment sampling and further soil sampling will 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 be performed during the RI/FS, is necessary to determine the state of on-post property before changes in land use occur.
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 recent laboratory study has shown RDX accumulation in plants, including distribution, without metabolic breakdown, into seeds. Concentrations may not be expected to be high enough to cause acute toxic effects after short-term ingestion, but may be a cause for concern over an extended period. Discussions took place among ATSDR, USATHAMA, EPA, NDEC, and NDH concerning possible vegetable contamination, and, in August, 1991, CAAP began sampling vegetables and soil from residential gardens, as well as soil from yards irrigated with RDX- and TNT-contaminated water. Results from the vegetable sampling indicate that RDX and TNT were not detected at levels above the 0.19 ppm health risk value established for consumption of vegetables.
If lawns are watered with contaminated water, any potential health effects would be related to soil exposure. Analyses of soil samples taken in September, 1991, indicated no contamination with RDX.
Determining contaminant concentrations in the top three inches of soil is important for evaluating the potential for human exposure by way of ingestion, inhalation, and dermal contact. ATSDR recommends evaluating the results of sampling before changes in land use or human activity take place at CAAP.
Additional sampling of vegetables, including crops grown at CAAP, is planned during the RI/FS process and should be carried out to further define uptake of explosives in plants. Until that sampling is complete, and the results evaluated, vegetable gardens previously watered with contaminated well water should only be watered with city water (or some other source of uncontaminated water). Future sampling of vegetables and soils should be performed (because of the possibility of residual soil contamination) to further ensure the safety of vegetables from gardens 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 discontinued until additional studies show that crops are not affected.
The public health action plan (PHAP) for the Cornhusker Army Ammunition Plant NPL site contains a description of actions to be taken by ATSDR and/or other governmental agencies at and in the vicinity of the site subsequent to the completion of this public health assessment. The purpose of the PHAP is to ensure that this public health assessment not only identifies public health hazards, but provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. Included is a commitment on the part of ATSDR to follow up on this plan to ensure that it is implemented. The public health actions to be implemented are as follows:
ATSDR will reevaluate and expand the PHAP when needed. New environmental, toxicological, or health outcome data, or the results of implementing the above proposed actions may determine the need for additional actions at the CAAP site.
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
FIGURES
Figure 1. General Location of Cornhusker Army Ammunition Plant
Figure 2. Environmental Study Areas, Cornhusker Army Ammunition Plant
Figure 3. Soil Map of Hall County, Nebraska
Next Section Table
of Contents
