PUBLIC HEALTH ASSESSMENT
NEW BRIGHTON/ARDEN HILLS
(a/k/a U.S. ARMY TWIN CITIES AMMUNITION PLANT)
NEW BRIGHTON, RAMSEY COUNTY, MINNESOTA
The pathways evaluation indicates that people were exposed in the past to contaminated groundwater. Several contaminants were measured in drinking water wells on and off TCAAP. An exposure dose via ingestion can be estimated from maximum concentrations found during sampling. The exposures evaluated here represent a worst case scenario; the estimate used may reflect conditions at only one exposure point. Exposure doses at other exposure points may have been lower.
There are insufficient data with which to determine the lengths of exposures to contaminants at these exposure points. The exposure estimates in the following paragraphs are based on an exposure duration of at least one year and a body weight of 70 kilograms for an adult or 10 kilograms for a child. It was assumed that an adult drinks two liters of water a day and a child drinks one liter.
These estimated exposure doses are compared with a chronic reference dose (RfD), a minimal risk level (MRL), and a cancer slope factor. An RfD is an estimate of a daily exposure of the general population (including sensitive subgroups) unlikely to have an appreciable risk of adverse noncancer health effects during a lifetime of exposure. An MRL is an estimate of daily human exposure to a chemical that is likely to be without an appreciable risk of adverse noncancer health effects during a specified period of exposure. MRLs are discussed in detail in ATSDR's series of toxicological profiles. The EPA's cancer slope factor is an estimate of the likelihood of getting cancer from a lifetime exposure to a carcinogen (cancer-causing chemical). The carcinogen classification is based on evidence from animal and human studies. The B classification indicates that a substance is considered a probable human carcinogen, the C classification that a substance is a possible human carcinogen, and the D classification that a substance is not classifiable.
The three areas for which estimated doses will be discussed are 1) three residential wells (two wells in the North Plume and one in the South Plume), 2) tap water samples from the TCAAP water supply system, and 3) the contaminated wells that served Arden Manor Mobile Home Park in 1981. The past (early 1980s) concentrations of contaminants in the New Brighton municipal water system were not used as estimates, because there is no information on the levels of contamination at all points of exposure. The levels of contamination in the New Brighton system were measured at the wells and are assumed to be higher than levels at the taps in homes and at work locations. The current and future operation of the treatment systems eliminates any current or future exposures.
The estimated exposures associated with both residential wells in the North Plume exceeded the MRLs for 1,1-DCE and for TCE. That suggests the possibility of an increased risk of noncancer health effects in persons who used those wells. The estimated cancer risk for users of those wells, calculated using the cancer slope factor, is also slightly increased. Exposure doses associated with the well in the South Plume would have been even higher, because of the high concentration of TCE (7,000 ppb) measured in that drinking water well.
None of the dose estimates for exposures associated with the use of the other wells (other than TCAAP supply wells and Arden Manor Mobile Home Park wells) exceeded health comparison values for TCE. Estimated exposures did not exceed the EPA Lifetime Health Advisory for 1,1,1-trichloroethane (TCA).
The dose estimates discussed here do not include the interactive effects that may result from exposures to multiple compounds. Moreover, the dose estimates do not include an estimate for inhalation exposure, which, considering the concentrations of VOCs measured in the private wells, could be extensive. The exposures that may have resulted from use of the TCAAP water supply wells and the Arden Manor Mobile Home Park wells are of public health concern for noncancer effects because they exceeded health comparison values. However, no adverse health effects have been observed in humans exposed at the reported concentrations.
The following discussion describes the general types of symptoms that have been discovered in health studies of people exposed to VOCs. However, in some cases, the concentrations at which adverse health effects may occur, as described here, may be higher than the exposure concentrations identified in the area around TCAAP.
The most commonly reported symptoms have been neurologic (nervous system) and psychological effects. Electrophysiologic changes on brain scans have been described in reports of persons with high exposures to solvents. In one study, changes in the electroencephalogram (EEG, which measures brain waves) remained in some subjects for 3 to 9 years after the diagnosis (33). Another study that examined objective measures of sensory and cognitive impairments suggested the presence of minor dysfunction of the nervous system; the effects were increased by alcohol use. This study also noted mild cognitive impairments of attention processes (34). Studies have indicated that painters have an elevated risk of disability from neuropsychiatric dysfunction (35, 36). Studies of abusers of volatile substances (such as glue sniffers) have provided good evidence that neuropsychiatric impairment is often present in persons with defined neurologic abnormalities. However, there are too many shortcomings in the studies to permit conclusions about persons without neurologic abnormalities (37, 38).
Conflicting results have been reported from studies of the reproductive effects of solvents exposure. Studies in Scandinavia have suggested solvents exposure causes menstrual effects (39) and an increased risk of spontaneous abortion (40). A large study of women potentially exposed to solvents-contaminated water did not indicate an increase in adverse pregnancy outcomes associated with drinking water from a contaminated well (41).
TCE has been shown to be a liver carcinogen in certain strains of laboratory mice which ingested the substance. A controversial human study indicated that TCE in drinking water may be associated with childhood leukemia (42). However, interpreting this data is hampered by numerous problems (43). The human data and data from studies of species other than mice are inconclusive. TCE was at one time considered by EPA to be a probable human carcinogen, but that classification was withdrawn pending further review of data. It currently is not possible to quantify the possible carcinogenic risk of exposure to TCE at the TCAAP site, because there is no definitive information on durations of exposure.
1,2-Dichloroethane (1,2-DCA) is considered to be a probable human carcinogen, because it causes cancer in mice and rats. Some studies indicate that 1,2-DCA and some of its metabolites can damage genes. On the basis of this information, exposure to 1,2-DCA in groundwater is of concern because of the possible resulting increase in cancer cases.
It is not possible to draw any site-specific health outcome conclusions for TCAAP and surrounding areas because of the large difference in population characteristics, as reflected by the summary of tables of vital statistics in Appendix E. The site population varies in such characteristics as age and the number of minority residents in the counties. Those characteristics will influence the susceptibility of a population to certain diseases and adverse health effects. Data at the county level cannot be used to draw site-specific conclusions, because they draw from a broad geographic area containing many communities, such as the Minneapolis/St. Paul metropolitan area. Instead, county data are used to indicate the general health of the population in an area.
Information from the Minnesota Cancer Registry has been provided for Ramsey County for the year 1988 (the only year for which data are available). Again, the differences in population characteristics between the site population and the populations of the three counties do not permit site-specific conclusions. In addition, 1 year of cancer incidence data is not sufficient to assess differences in cancer occurrence among the populations. A summary table of the expected and observed numbers of cancers is provided in Appendix E.
The Minnesota Department of Health conducted the study "Feasibility of Community-Wide Epidemiologic Studies of Drinking Water and Health: St. Louis Park and New Brighton" in 1985 (44). The purpose of the study was to determine the usefulness of conducting a full-scale epidemiologic study in the two communities, both of which had environmental contaminants present. The study determined that the major problem associated with conducting environmental epidemiologic studies was the difficulty of determining an accurate estimate of exposure, which in turn would make it difficult to compare exposed and nonexposed persons. The study suggested that future questions about cancer in the community could be addressed through the establishment of a statewide cancer registry and that additional community-based epidemiologic investigations were not justified at the time. However, the data from a cancer registry would not provide any information on the neurologic effects described by some individuals that have been previously described as effects of exposure to VOCs.
The National Exposure Registry is a list of persons exposed to hazardous substances. The registry is composed of chemical-specific subregistries. The chemicals for which subregistries have been established were selected from a list of hazardous substances ATSDR designated as substances posing the greatest threat to public health. The TCE Subregistry was closed in June 1990; it has approximately 5,000 registrants. Those registrants include persons from 10 NPL sites and 2 non-NPL sites in 3 states.
Sites selected for inclusion in the National Exposure Registry must meet specific criteria as outlined in the Policies and Procedures for Establishing a National Registry of Persons Exposed to Hazardous Substances. In order for a site to be selected for inclusion on a subregistry, persons at the site must have been exposed or must currently be exposed to the designated chemicals of interest, i.e., there must be validated evidence that an environmental medium is contaminated, that a valid route of transmission from the medium to the person exists, and that transmission actually occurred or is occurring.
The primary purpose of the National Exposure Registry is to create a large database of similarly exposed persons. That database is to be used to facilitate epidemiologic research in determining adverse health effects of persons exposed to low levels of chemicals over a long period. A core questionnaire is administered when a person is added to the National Exposure Registry; the questionnaire is then updated annually. ATSDR keeps registrants informed of new developments related to the chemical under investigation.
As described in the Background section of this document, ATSDR attempted to recruit persons in the TCAAP area for the TCE Subregistry in 1989. The City of New Brighton and MDH declined to participate (11).
ATSDR has received depositions of physicians who examined residents of New Brighton who have filed a lawsuit against TCAAP. However, because this population is self-selected, the information from the depositions cannot be used to establish any association between exposure and health effects. Studies of self-selected people may be biased, because people already exhibit, believe they exhibit, or are more likely to remember symptoms of adverse health effects. Therefore, there is an increased likelihood that symptoms will be consistently reported by those persons. The studies of the self-selected people may not accurately represent the affected communities' number and distribution of the reported symptoms. However, self-selected studies can provide an indication of the types of complaints expressed by some members of the community. An occupational medicine physician examined a number of the plaintiffs who filed the lawsuit against TCAAP and noted that a substantial number had symptoms of emotional distress and physical dysfunction (5). The physical abnormalities were generally seen in the nervous, neuropsychiatric, and collagen-vascular systems and in the heart and liver. The most commonly reported symptoms are described in the table in Appendix D. Many of those symptoms have been associated with exposure to solvents; however, they are not specific to solvents, i.e., they also have been reported to result from many other causes.
An internist and a cardiologist interviewed 30 of the residents and reviewed their medical records and the results of physical exams (46). Additional tests were ordered on 12 of the residents. Seven were reported by the physicians to have some type of cardiac arrhythmia (abnormality of heart rate). The specific type of arrhythmia was not noted for any of the residents.
The summary reports of neurologic examinations for 25 persons (12 men, 13 women) were provided by the neurologist who conducted the examinations (47). Common complaints included difficulty with concentration, difficulty with memory, headaches, mood changes, depression, and fatigue. The neurologist noted abnormalities in neurophysiological and neuropsychological tests in several of the patients examined.
Some citizens in the communities in the vicinity of TCAAP have expressed concern that the exposure to low levels of VOCs in drinking water has adversely affected their health. They have expressed concern that their health was affected in the past and may continue to be affected in the future. They have requested that their physical health be monitored.
Will epidemiological studies will be performed and, if so, when?
No epidemiological study is planned for the communities impacted by TCAAP contaminants. However, ATSDR's Division of Health Studies (DHS) staff will evaluate the feasibility of conducting a community health investigation, focusing on neurobehavioral function, to explore the possibility of adverse health effects related to human exposure to TCAAP contaminants. If such a scientific investigation is deemed feasible, the health investigation will be implemented as resources permit.
Can birth defects result if a pregnant woman ingests contaminated water at concentrations reported for the mobile home park?
Although some solvents (toluene) have been associated with birth defects in infants whose mothers inhaled fumes (sniffed glue) during pregnancy, data on the toxicity of most solvents are not clear. As noted in the Toxicological Evaluation section, the results of previous studies on reproductive outcomes have been conflicting. More information on the number and types of birth defects seen in the area would be required before this question could be answered. Unfortunately, Minnesota does not have a birth defects registry. If sufficient health information is available, ATSDR's Division of Health Assessment and Consultation will conduct a health statistics review focusing on cancers and birth defects information.
Are citizens being exposed to toxic substances in the air?
Users of water from municipal wells are not being exposed to toxic substances in the air. Exposure to groundwater contamination was eliminated after initiation of treatment of the municipal water. However, some people may have continued to use residential or commercial wells that have some level of contamination. The types of compounds present in the wells are volatile (i.e., they tend to move into the air). If people are using contaminated water inside for activities such as cooking or showering, they could be exposed to the chemicals through the air. On the other hand, there is not much likelihood that outdoor exposures are great, because the chemicals are diluted in the air.
Is there a link between cases of leukemia in the exposed population and the use of solvent-contaminated drinking water?
No evidence is available to link leukemia with drinking water containing TCE at the concentrations found in some specific drinking water wells in the area surrounding TCAAP. MDH reports that 7 cases of leukemia occurred in New Brighton during the period 1988-1991; on the basis of incidence rates for the metropolitan area, 8.4 cases would have been expected (13). As discussed in the Toxicological Evaluation section, a controversial study has suggested an association between leukemia and TCE ingestion (42). However, this study is flawed (43). Human carcinogenicity data and data from studies of species other than mice are inconclusive. EPA at one time considered TCE a probable human carcinogen, but that classification has been withdrawn pending further review of data. It is not possible to quantify the possible carcinogenic risk of exposure to TCE at this site, because durations of the exposure have not been defined.
Could the past exposure to contaminated municipal water cause testicular cancer or other cancers noted in a New Brighton neighborhood?
Exposure to the low concentrations of contaminants that may have been present in homes served by the New Brighton municipal water system in 1982 would not be expected to cause testicular cancer or other cancers. Though the concentrations of contaminants in home tap water are not known, analysis of tap water from a restaurant using municipal water in 1982 indicated a maximum concentration of TCE of less than 10 ppb. This concentration is more than a hundred times less than concentrations that may cause adverse health affects.
Should not the families exposed to high levels of contaminants in private wells be included in a long-term medical monitoring program to determine whether there are chronic health effects?
At least two families were exposured to private well water with TCE at concentrations above 2,400 ppb. The length of exposure is unknown, but it is reasonable to assume that the wells had been contaminated for more than 1 year and possibly for as long as 10 years. Some form of follow-up medical consultation, which could include once-a-year medical monitoring, appears to be a prudent precaution.
Hazardous waste sites within the Twin Cities Army Ammunition Plant (TCAAP) are public health hazards because people were exposed in the past to TCAAP groundwater contaminants at concentrations that may result in adverse health effects. Human exposure to solvents via ingestion, inhalation, and skin contact occurred when contaminants from TCAAP migrated into private, mobile home park, commercial, industrial, TCAAP, and municipal water supply wells. Human exposure to TCAAP contaminants in municipal and TCAAP water supply wells ended with the initiation of comprehensive water treatment technology. Current municipal water supplies for the cities surrounding TCAAP and drinking water supplies on TCAAP meet all state and federal drinking water standards.
The concentrations measured in some of the contaminated private wells in the past (2,700 - 7,000 ppb TCE) are great enough that long-term exposure (more than 1 year) to these concentrations could result in adverse health effects. Exposure ended for many of the people with contaminated private wells when their homes were connected to municipal water supplies in the early 1980s.
However, unless remediation is undertaken, concentrations of TCAAP-related contaminants in the Hillside Sand and Prairie du Chien/Jordan aquifers will remain above health concern levels for many years. These chemicals continue to move and to contaminate other portions of the two drinking water aquifers.
TCAAP groundwater contaminants pose an indeterminate health hazard, because current and future human exposure to TCAAP contaminants is possible through the unreported or unidentified use of private, mobile home park, commercial, and industrial wells within the North Plume and the South Plume. However, MPCA and MDH have made special efforts to identify all wells threatened by TCAAP contaminants. In addition to the existing inventory and monitoring efforts performed by MPCA, another detailed well inventory has been conducted by the Army to determine whether any previously unidentified water supply wells are threatened by TCAAP contaminants.
The possibility of current and future exposure to TCAAP groundwater contaminants in the North Plume will be mitigated for private well users through the implementation of the selected remedy for Operable Unit 1 as proposed by the Army, MPCA, and EPA in September 1993. As described in the Background section of this document, the remedy includes implementing drilling advisories that regulate the installation of new wells within the North Plume as a Special Well Construction Area and providing alternative water supplies to residents with private wells within the North Plume. The proposed containment system will prevent future movement of the most highly contaminated portion of the groundwater contaminant plume.
MPCA has stated that the South Plume will also be contained in the Special Well Construction Area as the North Plume (48).
Groundwater contaminants are also migrating from Site A, on TCAAP, toward residential wells north of Site A. The majority of the residences north of Site A are connected to the Shoreview municipal water system. However, a few residences still rely on private wells. Contaminant concentrations that approach any health comparison value or drinking water standard have not been reported in residential wells still in use. The MPCA, EPA, and Army are closely monitoring the movement and concentrations of contaminants in residential wells.
Health concerns were expressed by several individuals living in the vicinity of TCAAP. Among the concerns discussed in the Community Concerns Evaluation section was the possible link between ingestion of TCE in drinking water and the occurrence of leukemia. The number of leukemia cases reported for the New Brighton area between 1988 and 1991 (7) is not higher than the number of leukemia cases expected (8.4) based on background rates for the Minneapolis/St. Paul area.
1. Regulatory agencies should continue their efforts to identify private, mobile home park, commercial, and industrial wells that may be contaminated and are still used for drinking water. Regulatory agencies should continue to sample such wells in a timely way. Alternative water supplies should be provided or contaminant removal systems should be added if results of the sampling indicate concentrations exceeding drinking water standards. Residences and businesses with contaminated drinking water wells should be connected to an appropriate treatment system or, after alternative water is provided, the wells should be properly plugged and abandoned.
2. To address future groundwater contamination problems, long-term institutional prohibitions (30 years or longer) should be implemented to prevent installation and operation of wells that supply water for drinking or bathing and do not have appropriate treatment systems. The Army has proposed such institutional prohibitions in the Feasibility Study for Operable Unit 1.
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended, requires ATSDR to perform needed public health actions at hazardous waste sites. To determine if public health actions are needed, ATSDR's Health Activities Recommendation Panel (HARP) has evaluated the data and information developed in the New Brighton/Arden Hills Public Health Assessment. HARP agreed that including members of this community in the TCE Subregistry, as previously recommended by ATSDR, would have been appropriate. (Please see explanatory note below.) HARP also recognizes that inclusion on the subregistry cannot occur without the cooperation of state and local officials or if the community does not wish to be included. HARP encourages the community, as well as state and local officials, to reconsider this option.
Because people may have been exposed to TCE and other VOCs that could cause illness, HARP has determined that a community health investigation focusing on neurobehavioral function is indicated. A health statistics review focusing on cancers and birth defects information (if available) is also needed. HARP also determined that continued community and health professions education is needed for this site.
NOTE ON COMMUNITY. The HARP recommendation refers to the overall community, including all human populations exposed or potentially exposed to TCAAP contaminants, and not just to the municipal well users within the city of New Brighton.
The purpose of the Public Health Action Plan (PHAP) is to ensure that this public health assessment not only identifies public health hazards but also provides a plan of action designed to initiate any needed follow-up health studies or other public health actions. Public comments received on the PHAP will be considered in planning and implementing any follow-up public health actions.
ATSDR's Division of Health Studies will evaluate the feasibility of conducting a community health investigation focusing on neurobehavioral function to explore the possibility of adverse health effects related to human exposure to TCAAP contaminants. If such a scientific investigation is deemed feasible, the health investigation will be implemented as resources permit.
ATSDR's Division of Health Education will provide environmental health education for local health care providers and the communities to assist the communities in assessing possible adverse health outcomes associated with past exposures to groundwater contaminants.
If information is available, ATSDR's Division of Health Assessment and Consultation will conduct a health statistics review focusing on cancers and birth defects information.
ATSDR will notify the communities affected in the past by TCAAP contaminants, including the City of New Brighton, of any important health findings resulting from the analysis of the TCE Subregistry data pertaining to other affected communities in other states. At this time, no registry action is planned for the communities affected by TCAAP contaminants, because the TCE Subregistry has been established with exposed populations at other hazardous waste sites. In keeping with the published policies and procedures governing addition of sites to the National Exposure Registry, sites with exceptional characteristics (such as exceptionally high levels of TCE) that will provide unique information might be added, or sites might be added if the analysis of the current registrants indicates a need for supplemental information. Should this occur, the TCAAP communities, with the exception of the city of New Brighton, will be considered for inclusion.
Preparers of Report
John H. Mann, P.G.
Division of Health Assessment and Consultation
Virginia Lee, M.D.
Division of Health Studies
Gary Campbell, Ph.D.
Environmental Health Scientist
Division of Health Assessment and Consultation
ATSDR Regional Representative
Public Health Advisor
EPA Region V
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