PUBLIC HEALTH ASSESSMENT
VERONA WELL FIELD
BATTLE CREEK, CALHOUN COUNTY, MICHIGAN
The Verona Well Field site was placed on the U.S. Environmental Protection Agency's National Priority List in September 1983. In 1981, some of the wells in the Verona Well Field, the primary source for the municipal water system of the City of Battle Creek, Michigan, and many private wells in the same area were found to be contaminated with volatile organic chemicals. The most contaminated municipal wells were taken out of service, and other appropriate steps were taken to reduce the contaminant levels in the municipal system to acceptable levels. Beginning the following year, residents with contaminated private wells were provided with bottled water and, by 1984, their homes and businesses were connected to the municipal water supply. New municipal wells were drilled in uncontaminated areas. Several of the abandoned municipal wells were put in service as purge or blocking wells to intercept contamination before it would reach the wells currently in use. There has been no detectable contamination in the municipal water system since 1984. The contamination has been traced to three sources near the well field: the Thomas Solvent Raymond Road Facility, the Thomas Solvent Annex, and the Grand Trunk Western Railroad marshalling yard.
Remediation of the Thomas Solvent Raymond Road Facility began in 1987. Construction of the remediation system at the Thomas Solvent Annex began in mid-1993. From 1984 to 1988, the Michigan Department of Public Health (MDPH) and the Centers for Disease Control (CDC) conducted a health study of individuals having used contaminated private wells in the Verona area and a representative sample of individuals using Battle Creek municipal water. The study attempted to correlate health effects with exposure to the contaminated drinking water. No health effects were found that could be associated with the contamination. The individuals studied have been included in the Agency for Toxic Substances and Disease Registry (ATSDR) National Exposure Registry, Trichloroethylene (TCE) Subregistry.
The site poses a public health hazard, due to the past history of exposure via groundwater and the potential for future exposure. Future exposures could occur if the remedial measures that have been taken to capture the contaminated groundwater plume were interrupted or if residents used contaminated water from private wells for drinking, cooking, or other household uses contrary to public health advisories. The extent of surface soil contamination in the source areas should be evaluated. Health concerns at the site have been largely addressed by the MDPH/CDC health study and the ATSDR Exposure Registry. Participants in the Exposure Registry will continue to benefit from registry follow-up and updates as new information becomes available. Community health education is recommended to remind those who have private wells of the risks associated with using contaminated groundwater.
The Verona Well Field site was listed on the United States Environmental Protection Agency (U.S. EPA) National Priorities List (NPL) in September 1983.
The U.S. EPA has designated the Verona Well Field site to include the Verona Well Field and its zone of influence, that is, the area in which pumping from the wells in the field makes a significant change in the groundwater level. The Verona Well Field serves as the primary well field for the City of Battle Creek, Michigan, municipal water supply. Three sources of groundwater contamination in the site area have been identified: the Thomas Solvent Raymond Road Facility and the Thomas Solvent Annex, both approximately 1 mile south of the well field, and a Grand Trunk Western Railroad marshalling yard adjacent to the well field on the east (see Figure 1) (1). The well field is located on the northeast side of Battle Creek, Michigan, approximately 0.5 mile north of Emmett Street, mainly east of the Battle Creek River and west of a Grand Trunk Western Railroad right-of-way. The Thomas Solvent Raymond Road Facility is located at the intersection of Emmett Street and Raymond Road, south of Emmett Street, and the Thomas Solvent Annex is on the south side of Emmett Street, west of Raymond Road, on property owned by the Grand Trunk Western Railroad adjacent to their right-of-way. Other potential sources of groundwater contamination in the site vicinity that have been investigated in connection with the site include property owned by Consumers Power near the Verona Well Field, the Raymond Road Landfill south of Emmett Road, and the site of a demolished Grand Trunk Western Railroad roundhouse south of the Thomas Solvent Annex. There is also some concern that contamination from a gas station west of the Verona Well Field may have reached some of the municipal wells. Monitoring of the threatened wells has found no contamination.
The Thomas Solvent Raymond Road Facility and the Thomas Solvent Annex were used for storage, blending, and packaging of industrial solvents. The Home Fuel and Coal Company started operations at these locations in 1939, leasing the Annex property from the Grand Trunk Western Railroad. The company name was changed to the Home Coal and Cleaning Solvent Company in 1950, and to the Thomas Solvent Company in 1963. The Thomas Solvent Company declared bankruptcy and closed in 1984. Leaks from underground storage tanks, leaking drums, surface spills, poor housekeeping practices, and direct discharges released contamination to the soil and groundwater. In 1984, it was found that 9 of 21 underground storage tanks at the Raymond Road Facility were leaking. The tanks were emptied in 1984, and removed in early 1991. Three underground storage tanks at the Annex were removed in 1990. The Raymond Road Facility is currently fenced, with a locked gate. The Annex area was fenced in early 1993 (2).
Workers in the repair and paint shops in the Grand Trunk Western Railroad marshalling yard customarily disposed of solvents used as degreasers and paint thinners by dumping them into a "drum pit," consisting of a drum partially buried in the ground with holes punched in the sides and bottom. This practice continued from the mid-1960s until approximately 1980. The drum from the "drum pit" has since been removed and the pit filled in. Access to the paint shop area is not restricted, though the presence of workers during daytime and watchmen overnight will deter unauthorized visitors.
During investigation of water quality in a church's drinking water in 1981, local health authorities found volatile organic chemical (VOC) contamination in some of the wells serving the Battle Creek municipal water supply. As the contamination was identified in the Verona Well Field, contaminated municipal wells were taken out of service. During follow-up sampling, numerous private wells located between the Verona Well Field and the source areas were also found to be contaminated with VOCs. Residents with contaminated wells were supplied with bottled water and access to showers, and, by 1984, all affected homes and businesses were connected to the municipal supply.
It has been reported that, in spite of the advisories from the various health authorities and the availability of alternative water supplies, some residents of the area have since resumed use of their private wells for lawn watering and car washing. Some area residents, again in spite of the advisories from the various health authorities, disconnected from the municipal system and resumed use of their private wells for all purposes. However, as these wells have failed due to age, Calhoun County refused to issue permits for replacement wells or repair of the old ones. The residents then reconnected to the municipal water system and abandoned the old wells. As of July 1993, one resident in the area is still using his private well (3).
In July 1983, the U.S. EPA proposed the site for listing on the NPL, and the U.S. EPA placed the site on the NPL in September 1983. By February 1984, VOC contamination had been detected in 27 of the original 30 municipal wells in the field and 80 nearby residential wells. Until new wells outside the contaminated area were brought on line, water from the less heavily contaminated wells was blended with clean water to keep the concentration of contaminants in the finished water generally below the detection limits or within an acceptable range. The U.S. EPA conducted an Initial Remedial Measure in 1984 that included conversion of 12 municipal wells to blocking or purge wells, treatment of the extracted water with an air stripper, and construction of 3 new production wells outside the contaminated area. The blocking wells are pumped continuously and the water is treated and discharged to the Battle Creek River. This process is intended to intercept and remove contaminated water before it reaches wells downgradient of the blocking wells.
From August 1983 through September 1985, the Center for Environmental Health of the Centers for Disease Control (CDC) and the Agency for Toxic Substances and Disease Registry (ATSDR) provided consultations with the U.S. EPA on health aspects of the proposed remediation (4, 5, 6, 7, 8, 9, 10, 11, 12).
With funding from the ATSDR, the Michigan Department of Public Health (MDPH) and the Centers for Disease Control (CDC) initiated a study in 1984 to investigate health effects from exposure to volatile organic chemicals. The study focused on exposed populations in the Verona Well Field area, but included smaller groups of people who had been exposed to a similar mix of chemicals in the Cities of Springfield, and Dowagiac. The Springfield and Dowagiac exposures were associated with contamination sources unrelated to the Verona Well Field NPL site. The MDPH and CDC issued a final study report in 1988 (13). Investigators for the U.S. EPA identified the three potential sources for the groundwater contamination listed above.
In 1985, the U.S. EPA signed a Record of Decision (ROD) for remediation of the Thomas Solvent Raymond Road Facility, specifying groundwater and soil vapor extraction and treatment to decontaminate soil and groundwater on the site. The groundwater remediation began at the Raymond Road Facility in 1987, the soil vapor extraction system was installed in 1988, and both systems are still in operation as of this writing.
In 1987, a Remedial Investigation (RI) concentrating on the remaining source areas was initiated. The final report for the RI was issued in August 1990 (1). A Public Comment Draft of the Feasibility Study (FS) report was circulated in February 1991 (14). On June 28, 1991, the U.S. EPA signed a ROD for further remediation at the site. This ROD calls for continued operation and expansion of the purge well system at the well field. Groundwater and soils at the Thomas Solvent Annex and the Grand Trunk Western Railroad marshalling yard paint shop are to be treated with extraction and treatment of the groundwater and with soil vapor extraction, respectively (15). The Thomas Solvent Annex property was fenced in April 1993, and the soil vapor extraction installation went into operation in late June 1993 (2).
In 1990, the City constructed four additional wells in the northern part of the Verona Well Field, away from the contaminated area.
In 1990, traces of organic chemicals were found by MDPH in residential wells along Willison Road east of the Verona Well Field site area. The State of Michigan is providing the residents using these wells with bottled water for drinking, under provisions of the Michigan Environmental Response Act (Act 307). The State is also arranging to have these residences and others in the neighborhood connected to the City of Battle Creek water system (16).
The Battle Creek River flows north to south through the site area. Most of the Verona Well Field and all of the major potential contamination source areas are east of the river. A 7-foot-high dam spans the river 500 feet north of Emmett Street and approximately 1 mile downstream from the well field. The Battle Creek River joins the Kalamazoo River approximately 3 miles southwest of the site.
The geological strata in the site area consist of the following, from the surface downward: 10 to 60 feet of glacially-deposited sand and gravel, 110 to 120 feet of Marshall Formation sandstone, and the Coldwater Shale formation which is of undetermined thickness in the site area. A fractured area of the Marshall Formation, called the Verona Structure, runs approximately parallel to the Battle Creek River under the Verona Well Field and appears to influence groundwater flow in the area.
The groundwater surface in the site area is primarily in the glacial zone, typically 8 to 28 feet below the surface. No confining layers between the surface and the Coldwater Shale have been identified in the site area (1). Thin lenses, approximately 2 feet thick, of shale in the sandstone may act as aquitards, inhibiting water flow between upper and lower layers (17). Groundwater in the glacial zone and in the underlying sandstone form essentially a single aquifer. There are slight vertical gradients, generally downward from the glacial unit to the sandstone and upward from the lower layers of the sandstone to the upper layers. The general groundwater flow in the site vicinity, outside the area of influence of the well field, is toward the Battle Creek River, and the groundwater discharges to the river below the Emmett Street dam. Above the dam, the river may recharge the groundwater. Pumping from the wells in the Verona Well Field draws groundwater to the Field from throughout the site vicinity, including both sides of the river. There are indications that groundwater flows under the river at the well field. The potential source areas of contamination are within the zone of influence of the well field. Groundwater at the Thomas Solvent Raymond Road Facility and the Thomas Solvent Annex flows north, the water under the Grand Trunk Western marshalling yard flows northwest, all flowing toward the well field.
Brendan Boyle and John Filpus of the MDPH visited the site with the Michigan Department of Natural Resources (MDNR) site manager on August 23, 1991. They examined the well field, the Thomas Solvent Raymond Road Facility, the Thomas Solvent Annex, and the Grand Trunk Western Railroad marshalling yard paint shop, and toured the surrounding neighborhood. They talked briefly with staff of the Calhoun County Health Department. Observations and information obtained during this visit are included in this Health Assessment. Numerous site visits were conducted by various Department staff during the period 1981-1984 in preparation for the health study. Staff from MDPH and CDC also participated in a public meetings held in March 1984 to discuss the proposed health study and to obtain citizen comments.
The Verona Well Field site is located on the northeast side of the City of Battle Creek, which has a population of approximately 36,000 (1980 Census). The residential population within the area bounded by the source areas and the well field is approximately 700.
The nearest residence to any of the source areas or the well field is located approximately 50 feet from the fence south of the Raymond Road facility. There are residential areas within the site area designated by the U.S. EPA, between Emmett Street and the Verona Well Field, east and west of the Grand Trunk Western Railroad marshalling yard. The area north and west of the well field, across the Battle Creek River, is also residential. There is a public park with several baseball fields and tennis courts on the west bank of the river, across from the main body of the well field. Three municipal wells are located along the north boundary of the park. Emmett Street and Raymond Road in the site area are zoned for retail and commercial use.
A Grand Trunk Western Railroad line runs from northeast to southwest across the site area. The railroad has a marshalling yard, with repair facilities, and the remnants of a former roundhouse in the site area. A Kellogg Company cereal plant is south of the site area.
The primary water source in the area is groundwater. The City of Battle Creek municipal water system, whose service area contains approximately 57,000 persons in Battle Creek and surrounding communities, obtains approximately 80 percent of its water from the Verona Well Field. Residents of the site vicinity use either municipal water or private wells for their domestic water supply. As mentioned above, municipal water hookups have been provided to residents of the site area whose private wells have been contaminated. Some residents are reported to be using their private wells again for watering lawns, washing cars, and other non-consumption purposes. Residents outside the known contamination area but not within the service area of the municipal supply, use private wells for all purposes. There also are private water systems within the municipal supply's service area.
The MDPH/CDC Battle Creek Health Study (13) included interviews, medical examinations, blood testing for chemical residues, and reviews of medical records for residents of the Verona Park area and of two other areas in the state where residents had been exposed to similar chemicals to those found in the Verona Well Field area, though from sources not related to this NPL site. The Study also included examination of mortality and hospital discharge data. No further health outcome data bases were evaluated for this assessment.
Residents of the site area have expressed concern about a perceived high rate of cancers and miscarriages. They are also concerned about skin and nervous system problems. Some individuals believe that the MDPH/CDC study lacked a valid control group because the Battle Creek municipal water supply was contaminated. They are also concerned that the municipal water supply may still be contaminated.
At a public meeting on March 12, 1991, called by the U.S. EPA to obtain public comment about the proposed remediation at the site, no questions explicitly related to public health were raised by the public. Citizens asked questions about potential exposure to chemicals. These were answered by U.S. EPA and MDNR personnel. A particular exposure route of concern to some residents was the potential for contaminants in the groundwater evaporating into the soil above the water table, and the vapors migrating into basements or to the soil surface. The proposed plan to clean up the site includes additional pumping of contaminated groundwater for treatment. Because some homes are between the source of contamination and the proposed pumping, these residents are concerned that the pumping would increase their potential exposure to volatile contaminants. Some citizens raised questions about the quality of the city water supply, and MDPH Division of Water Supply and Battle Creek Water Department personnel responded.
The MDPH released this public health assessment for public comment on May 25, 1993. The Public Comment Period lasted until June 24, 1993. Comments received by MDPH in this period and MDPH and ATSDR's responses to them are included in the Responsiveness Summary attached to this assessment.
To identify other facilities which might contribute to the environmental contamination at the Verona Well Field site, the MDPH searched the Toxic Chemical Release Inventory (TRI) data base for 1987, 1988, 1989, and 1990. The U.S. EPA compiles the TRI from reports provided by industries. The TRI contained entries for three facilities with the same postal zip code (49107) as the Verona Well Field. According to their addresses, the facilities listed are all located approximately two miles west of the Verona Well Field site. The facilities reported releases to the air of toluene and methanol. The releases from these facilities are not likely to contribute to environmental contamination at the Verona Well Field site.
Contaminants of concern at this site were selected from those chemicals for which the concentration in at least one environmental medium exceeded a health-based comparison value for that medium. Lifetime exposure to chemical concentrations at or below the comparison values should not result in more than 1 case of cancer in 1 million people exposed or any increase in non-cancer health effects. Comparison values used in this assessment include:
ATSDR Environmental Media Exposure Guides (EMEGs)
ATSDR Cancer Risk Evaluation Guides (CREGs)
Concentrations computed from the U.S. EPA Reference Dose (RfD) for chronic exposure of a child, assuming pica behavior for soil ingestion (RMEGs)(1)
U.S. EPA Drinking Water Health Advisories (Lifetime)
U.S. EPA Safe Drinking Water Act Maximum Contaminant Levels
Chemicals for which comparison values are not available are also retained as contaminants of concern. Contaminants of concern for this site include dibromochloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethylene, cis- and trans-1,2-dichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, trichloroethylene, vinyl chloride, benzene, toluene, ethylbenzene, xylenes, acetone, 4-methyl-2-pentanone, bis(2-ethylhexyl)phthalate, 2-methylphenol, 4-methylphenol, hexachloroethane, N-nitrosodi-n-propylamine, antimony, arsenic, cadmium, chromium, manganese, nickel, and zinc.
Environmental data in this section, unless cited otherwise, was taken from the RI report (1).
For this discussion, the site will be considered as the Verona Well Field, the Thomas Solvent Raymond Road Facility, the Thomas Solvent Annex, the Grand Trunk Western Railroad Paint Shop, and the area between. (Figure 1)
Concentrations of chlorinated volatile organic chemicals (VOCs) found in municipal and residential wells in the Verona Well Field area during the period from 1981 through 1988 ranged up to 3,900 parts per billion (ppb) (see Table 1).
Maximum concentrations of the VOCs found in the purge wells (or blocking wells), and abandoned municipal wells in August 1984 and April 1989 are listed in Table 2. Samples collected in 1989 from monitoring wells in the Verona Well Field, downgradient from the blocking wells, generally contained 1 ppb or less of any of the VOCs. One sample contained over 100 ppb of several different VOCs, including several that were not found in any other well. Later samples from the same well contained 2 ppb total VOCs, and a municipal well less than 100 feet from the monitoring well showed no contamination. The high results were probably due to laboratory errors. The total VOC content of the municipal water supply has been kept below 8 ppb since 1983 and below 2 ppb since 1984. The VOCs detected since 1984 have been trihalomethanes, which are usually the result of reactions between organic materials in water and the chlorine used in the purification process. None of the contaminants of concern connected with the site have been detected in the finished water supply since 1984.
Concentrations of various VOCs, metals, and semi-volatile organic chemicals (SVOCs) found in groundwater samples collected during the RI from extraction and monitoring wells at or downgradient of the contamination source areas on the site exceeded health-related comparison levels (Table 3). The downgradient wells are located between the contamination source areas and the well field. Twenty-two SVOCs were found in groundwater from the site area during the RI, although many were only found once. Bis(2-ethylhexyl)phthalate was detected in two-thirds (24 of 36) of the samples, but no other SVOC was found in more than four.
The Consumers Power area, located between the marshalling yard and the well field, was investigated during the RI as a potential source for contaminants at the site. Analysis of groundwater collected upgradient and downgradient of the Consumers Power area found no increase in contamination.
In July 1984, the RI contractors sampled soil from borings at the Thomas Solvent Raymond Road property, the Thomas Solvent Annex, and the Grand Trunk Western Railroad Paint Shop (18).
In July 1988, the RI contractors sampled soil from the Thomas Solvent Annex and the Grand Trunk Western Railroad paint shop. None of their samples can be considered representative of the surface soil, that is, the top 3 to 6 inches of soil, at these locations. They collected samples from 6 inches below the asphalt surface of the loading dock at the Annex, and from 3 to 4 feet below the surface elsewhere at the Annex and Paint Shop. They collected from soil borings samples that were composites of soils from 0 to 6 feet, 6 to 12 feet, and 12 feet below the surface to the water table. The maximum concentrations of VOCs found in sub-surface soil samples collected in the RI are listed in Table 4. The highest concentrations of VOCs were generally found in the deepest samples. Sub-surface soil samples (3 to 4 feet below the surface) collected in the Consumers Power area showed no contamination.
The MDPH sampled residential wells along Willison Street east (upgradient) of the site in 1990. Water from several of the wells contained low levels of VOCs, as much as 5 ppb cis-1,2-dichloroethylene and 1 ppb trichloroethylene (19). These concentrations do not exceed comparison values.
The site of the Grand Trunk Western Railroad roundhouse was investigated during the RI as a potential source for contamination at the Verona Well Field site. The RI investigators collected groundwater from two monitoring wells downgradient of the roundhouse. All samples were analyzed for selected volatile and semi-volatile organic chemicals. None of the target chemicals were found.
Residential wells downgradient of the Raymond Road Landfill have contained low levels of VOCs. Table 5 lists the maximum concentrations of chemicals found in the groundwater on and downgradient of the landfill during the RI investigation. The landfill appears to be a source for groundwater contamination, though it is not considered a major contributor to the contamination at the Verona Well Field site in comparison to other sources. Under provisions of the Michigan Environmental Response Act (Act 307), the MDNR is investigating the landfill separately from the U.S. EPA investigation of the Verona Well Field site.
In July 1984, the RI investigators collected soil samples from 4 locations in the residential area bounded by the Verona Well Field to the north, Battle Creek River to the west, Emmett Street to the south, and the railroad tracks to the east. None of these were surface samples according to ATSDR's consideration. Two were taken from 6 inches below the surface, the others were composites of 4 samples taken at the surface and at 1, 2, and 3 foot below the surface. Chemicals found are listed in Table 6. The RI investigators noted that all of these chemicals were also found in laboratory quality control blanks (18).
In July 1988, the RI investigators collected soil from the area of the Grand Trunk Western Railroad roundhouse, 3 to 4 feet below surface over most of the area and from the top 1 foot in the engine stalls, where the investigators could not bore through the concrete rubble. All samples were analyzed for selected volatile and semi-volatile organic chemicals. None of the target chemicals were found.
In preparing this public health assessment, the MDPH relied on the information provided in the referenced documents and assumed that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analysis and conclusions drawn for this public health assessment is determined by the reliability of the referenced information.
One sample collected from a monitoring well in the Verona Well Field during the RI contained very high levels of contaminants. These results were disregarded for purposes of this health assessment, since they were not confirmed on later sampling and were far out of the range of results found in wells a short distance from the well in question.
The Grand Trunk Western Railroad marshalling yard includes many physical hazards that are intrinsic to the yard's operations. Access is officially restricted to railroad employees and authorized visitors. The yard is fenced, though not completely, as the tracks into and out of the yard cannot be closed off and the main entrances to the yard have no gates.
The Thomas Solvent Raymond Road Facility area includes a large amount of equipment for the remediation and some debris, which may pose physical hazards to trespassers and visitors. A trespasser or visitor on the Thomas Solvent Annex property could fall off the loading dock that remains from operations at the site. Both facilities are fenced, with locked gates, the Annex since April 1993 (2).
Possible physical hazards on the well field are those posed by the terrain and by current maintenance operations in the area. The well field itself is fenced with an automatic gate. The gate was standing open at the time of the MDPH site visit in August 1991, though activities during normal business hours would discourage casual visitors. The three wells on the west side of the Battle Creek River are enclosed in locked pumphouses, though not otherwise fenced.
The primary pathway of concern at this site involves domestic use of contaminated groundwater. Chemicals used in the source areas were spilled or leaked into the soil. The chemicals could then migrate into the groundwater, with the assistance of infiltrating rain water. The chemicals would flow along with the groundwater to a well, either private or municipal. People using the water could then be exposed to dissolved chemicals by ingestion, dermal contact, or inhalation of volatile chemicals evaporating from the water during showering, washing dishes, cooking, and other uses. The primary chemicals of concern are VOCs, which are likely to evaporate during household use of water. Table 6 lists estimates for the maximum household air concentrations of selected VOCs from evaporation out of the groundwater. These estimates were calculated using Henry's Law, which assumes that, at equilibrium, the concentration in the air is proportional to that in the water, using coefficients from the literature.
This pathway was complete until 1984, when the remediation efforts were fully implemented. It is not fully known when the contamination first reached private wells in the area. Based on the history of contamination in the Verona Well Field, the MDPH/CDC Battle Creek Health Study estimated the earliest contamination of a private well to have occurred in March 1977 (Reference 13, p. 45). Abandonment of contaminated municipal and residential wells, use of purge wells to intercept contaminated groundwater, and replacement of contaminated water supplies with uncontaminated water has largely eliminated exposure through this pathway. Remediation of the contamination source areas combined with the purge well system should eventually remove the contamination. It has been reported that some residents of the affected area may have resumed use of their private wells for watering lawns, washing cars, and other non-consumption purposes. Failure of the purge well system or installation of new wells in the contaminated area, despite institutional controls, may complete this pathway again in the future.
Volatile chemicals in the groundwater can evaporate into porous soil above the water table. The chemical vapors can diffuse through the soil, migrating upwards until they reach the open air. Once the vapors reach the open air, dispersion and dilution will mitigate health concerns. A basement with relatively porous walls or floor could collect the migrating vapors, potentially reaching levels of human health concern. There is no evidence that this has occurred in the vicinity of this site. It seems probable that dispersion and dilution within the soil will keep the concentrations of the chemicals below levels of health concern.
Chemicals dumped or spilled onto the soil, as has happened in some source areas related to this site, can contaminate the surface soil. Contaminated soil may adhere to the clothing and skin of persons with access to these contaminated areas can have contaminated soil adhere to their clothing and skin. The contaminants may be absorbed from the soil into the skin. Soil that gets onto hands can also be ingested when the people eat, smoke, or otherwise brings their hand to their mouth before their hands have been washed. Volatile chemicals can vaporize from contaminated soils and a person on or near the site can inhale them. The Thomas Solvent Annex was freely accessible until it was fenced in April 1993, though there seems little to attract anyone to the site. The contaminated area in the Grand Trunk Western marshalling yard is physically accessible, though normal activity in the yard will limit public access. The Raymond Road Facility is fenced, though intrusion is still a possibility. There is no record of surface soil sampling in any of the source areas. Volatile chemicals will probably have evaporated from the surface soil in the years since the sites were in operation, but the areas should be tested for verification.
Fine soils can move as fugitive dust, spreading contaminants in surface soils to neighboring properties. People on or near an area of contaminated surface soil may breathe contaminated dust and thus be exposed to the contaminants. There are few barren areas, unpaved tracks, on the Thomas Solvent Raymond Road Facility and Annex, though most of the areas are vegetated. Dust should be only a minor problem, unless the barren areas are also highly contaminated. The Grand Trunk marshalling yard is largely covered with gravel, and dust may pose a problem, especially during dry weather. Because no surface soil sampling and analysis is on record for this site, the potential for exposure to contaminants via this pathway is not known.
The health effects of exposure to the various chemicals found at the site will be evaluated primarily by comparison with the Minimal Risk Levels (MRLs) for non-cancer health effects derived by the ATSDR and with the Reference Doses (RfDs) or Reference Concentrations (RfCs) derived by the U.S. EPA. Reference Doses are for ingestion exposure, Reference Concentrations for inhalation, and there are MRLs for both. MRLs for ingestion and RfDs are expressed in terms of milligrams of chemical ingested per kilogram of body weight per day, while MRLs for inhalation and RfCs are expressed in terms of concentration of the chemical in the air. People exposed to amounts of chemicals below the MRLs, RfDs, or RfCs are not expected to experience adverse health effects other than the potential of contracting cancer. As the MRLs, RfDs, and RfCs are usually extrapolated from animal studies, there is always some uncertainty about their accuracy in relation to humans. Cancer risks are not included in the derivation of the MRLs, RfDs, or RfCs, and will be evaluated separately, using an adult exposure for a 70-year lifetime and published slope factors to estimate the chance of contracting cancer. If this estimate indicates that among 1 million people experiencing the exposure for their lifetimes, 1 case of cancer might develop more than in a similar group that did not experience the exposure, the increased cancer risk is considered significant.
In this public health assessment, exposures to the chemicals have been based on an adult weighing 70 kilograms, drinking 2 liters of water per day and incidentally ingesting 100 milligrams of soil per day. To estimate exposures for sensitive populations, we used a child weighing 10 kilograms, drinking 1 liter of water a day, and incidentally ingesting 200 milligrams of soil per day. If an adult exposure exceeds a standard, so will the exposure for a child.
These evaluations are based on a worst case scenario, that a person's primary household water supply would contain the highest concentrations of the contaminants of concern found in groundwater in the site area. Since 1984, the Battle Creek municipal water supply has been free of organic contaminants of concern, with other contaminants within the Maximum Contaminant Levels (MCLs) promulgated by the U.S. EPA under the Safe Drinking Water Act. The MCLs are generally compatible with the MRLs and RfDs.
Chlorinated Volatile Organic Chemicals (VOCs)
Chlorinated VOCs, which include 1,1,1-trichloroethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethylene, cis- and trans-1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, dibromochloromethane, and vinyl chloride, are the most important contaminants associated with this site. They are usually found together and can produce somewhat similar health effects. They will be discussed together in the following paragraphs. Exposure to any of these chemicals by either inhalation or ingestion can cause liver and kidney damage. Breathing these chemicals at high concentrations can also have an anesthetic effect. Several of the chemicals have been linked to cancer of the liver and kidney. The U.S. EPA has classified vinyl chloride as a human carcinogen (U.S. EPA Class A), 1,2-dichloroethane, tetrachloroethylene, and trichloroethylene(2) as probable human carcinogens (U.S. EPA Class B2), and 1,1-dichloroethane, 1,1-dichloroethylene, and dibromochloromethane as possible human carcinogens (U.S. EPA Class C). A person of any age whose primary drinking water source contained any of these chemicals at the maximum concentration found at the site may have had exposures exceeding the MRLs or RfDs for non-cancer adverse health effects. These chemicals readily evaporate, and the concentrations in the air of a confined space where water containing the concentrations found at the site was being used could exceed the MRLs and RfCs. Lifetime consumption of water containing any of the carcinogenic chlorinated VOCs at the maximum concentration found on the site may be associated with a moderate to high increased risk of cancer (20, 21, 22, 23, 24, 25, 26, 27).
Not all of these chemicals have currently accepted MRLs, RfDs, or RfCs. 1,1-Dichloroethane and 1,1,1-trichloroethane have none of these. There is an RfD of 0.09 mg/kg/day listed in the ATSDR Toxicological Profile for 1,1,1-trichloroethane (25) that is apparently currently under review. A person of any age whose primary water supply contains the maximum concentration of 1,1,1-trichloroethane found in the groundwater at this site may ingest enough of the chemical to exceed this RfD. There is not enough data available to evaluate the health effects of exposure to the levels of 1,1-dichloroethane found at this site.
Volatile aromatic compounds, such as benzene, toluene, ethylbenzene, and xylenes, generally produce similar non-cancer health effects. Breathing high concentrations can have an anesthetic effect. Damage to the liver, kidneys, or blood can result from long-term exposure by either inhalation or ingestion. Benzene has been linked to cancer, specifically leukemia, while neither toluene, ethylbenzene, and xylenes have been linked to cancer. The U.S. EPA has classified benzene as a human carcinogen (U.S. EPA Class A), and toluene, ethylbenzene, and xylenes as not classifiable as to carcinogenicity (U.S. EPA Class D) (28, 29, 30, 31).
The maximum level of benzene found in groundwater at the site and the potential benzene concentration in air that has been in contact with the water exceed the MRLs via the respective media for non-cancer endpoints. People who consume water containing the maximum concentration of benzene found at the site or who breathe air that has been in contact with such water for their lifetimes may run a high increased risk of contracting cancer.
A person of any age whose primary drinking water supply contains the maximum concentration of toluene or ethylbenzene found in the groundwater at the site may ingest enough of the chemical to exceed the RfD for non-cancer health effects.
A child whose primary drinking water supply contains the maximum concentration of xylenes found in the groundwater at the site may ingest enough of the chemical to exceed the RfD for non-cancer health effects.
Other Organic Chemicals
Ingestion of large amounts of acetone, 2-butanone, or 4-methyl-2-pentanone, can cause nausea, vomiting, and liver and kidney damage. There is no evidence available as to whether any of these chemicals causes cancer. Acetone is a common laboratory chemical, and a frequent laboratory contaminant found in analysis. Though it was reported frequently at levels commensurate with a laboratory contaminant throughout the RI groundwater analysis, it was only found at significant levels in one well, one of the extraction wells at the Thomas Solvent Raymond Road Facility. 2-Butanone was detected in only one well, at the Raymond Road Landfill. 4-Methyl-2-pentanone was detected in one monitoring well, downstream of the Raymond Road Facility. It is unlikely that human exposure to significant levels of any of these chemicals will occur in relation to this site (32, 33).
No one whose primary drinking water supply contains the maximum concentration of bis(2-ethylhexyl)phthalate found in groundwater at the site is likely to ingest a dose above the RfD. Some experimental animals have developed liver cancer on exposure to the chemical, though there is no evidence that it causes cancer in humans. The U.S. EPA has classified bis(2-ethylhexyl)phthalate as a probable human carcinogen (U.S. EPA Class B2) (34). Based on the results of the animal studies, people drinking water for their lifetimes containing the maximum concentration of bis(2-ethylhexyl)phthalate found in the groundwater at the site may run a low increased risk of contracting cancer.
2-Methylphenol (also known as o-cresol) and 4-methylphenol (p-cresol) are closely related chemicals, isomers of one another and of a third chemical, 3-methylphenol (m-cresol). Consumption of water containing the maximum concentration of either methylphenol isomer found on the site, or containing both maximum concentrations, would not result in a dose in excess of the MRL. There is limited evidence from animal studies that exposure to methylphenols may increase the likelihood that exposure to other chemicals at the same time will cause cancer. Experiments have shown that methylphenols may react with genetic material, an indication of potential cancer-causing capability. The U.S. EPA has classified all methylphenol isomers as possible human carcinogens (U.S. EPA Class C). There is not enough evidence available to evaluate the cancer risk from exposure to methylphenols (35).
A child whose primary drinking water supply contains the concentration of hexachloroethane found in the groundwater at the site could ingest enough of the chemical to exceed the RfD. Hexachloroethane has caused liver and kidney damage in laboratory animals, though no chronic illness has been reported in people exposed under occupational conditions. The vapors can be irritating to the eyes, though it is highly unlikely that sufficient exposure to hexachloroethane vapors will occur at this site. There is limited evidence linking exposure to hexachloroethane to liver cancer in experimental animals. The U.S. EPA has classified the chemical as a possible human carcinogen (U.S. EPA Class C) (36, 37). Lifetime consumption of water containing the maximum concentration of hexachloroethane found in the groundwater at the site will pose no apparent increased risk of contracting cancer. The chemical was found in only one groundwater sample, so significant exposure is not likely.
The concentrations of N-nitrosodi-n-propylamine found in the groundwater at the site are below the MRL for non-cancer endpoints. Long-term exposure to the chemical has caused cancer of the liver, esophagus, and nasal cavities in experimental animals. There is no evidence available to link cancer in humans to exposure to the chemical. The U.S. EPA has classified N-nitrosodi-n-propylamine as a probable human carcinogen (U.S. EPA Class B2) (38). People who consume water containing the maximum concentration of N-nitrosodi-n-propylamine found in groundwater at the site for their lifetimes may run a moderately increased risk of contracting cancer. The chemical was found in only one groundwater sample from the site, so human exposure to the chemical is not likely to be common.
There are no published MRLs for exposure to antimony. Ingestion of water containing antimony at concentrations far above those found at this site has induced vomiting in humans. Long-term ingestion has caused liver damage in experimental animals. Breathing antimony dust, not a likely exposure pathway at this site, can cause heart, lung, liver, and kidney disorders (39).
The maximum concentration of antimony found in the groundwater at the site exceeds the proposed MCL and MCLG for the element in drinking water.
A person whose primary drinking water supply contains the maximum arsenic concentration found in the groundwater at the site could ingest enough of the metal to exceed the MRL, which is currently under review, for non-cancer health effects. Ingestion of arsenic can result in damage to the circulation system, liver, kidney, and nervous systems. Arsenic is believed to be an essential trace element in the diet, at levels far below those that cause adverse health effects. Skin changes that may develop into skin cancer can result after ingestion. Cancers of the liver, kidney, bladder, and lung have also been connected with ingestion of arsenic. The U.S. EPA has classified arsenic as a human carcinogen (U.S. EPA Class A) (40). People who consume water containing the maximum concentration of arsenic found in the groundwater at the site for their lifetime may run a moderately increased risk of contracting skin cancer. The relation between arsenic ingestion and cancer at other sites has not been adequately studied to permit an estimate of risk.
The maximum concentration of cadmium found in groundwater at the site is above the MRL for non-cancer health effects. Chronic exposure to elevated levels of cadmium has been linked to kidney damage. Ingestion of cadmium is not believed to cause cancer, though inhalation of cadmium dust has been linked to lung cancer. The U.S. EPA has classified cadmium when inhaled as a possible human carcinogen (U.S. EPA Class B1) (41). Inhalation is not a likely route for human exposure to cadmium at this site.
Chromium commonly occurs in compounds in two forms, the hexavalent oxidation state or chromium(VI) and the trivalent oxidation state or chromium(III). The toxicity of a chromium compound is strongly dependent on the oxidation state of the chromium included. Chromium(III) compounds are virtually non-toxic, and the metal in this form is an essential trace element. Chromium(VI) compounds can be caustic, and can cause liver and kidney damage. Inhalation of chromium(VI) compounds has been linked with cancer. Inhalation is not a likely route of exposure at this site. The U.S. EPA has classified chromium(VI) as a human carcinogen when inhaled (U.S. EPA Class A), but has not classified the metal by other routes of exposure or in other valence states. The concentrations of chromium found in groundwater at the site are above the MRL, which is currently under review, for non-cancer health effects if the metal is presumed to be primarily chromium(VI). The concentrations are below the MRL if the metal is mainly chromium(III). There is no information on the valence of the chromium found in the groundwater at the site. Chromium(VI) is readily reduced to chromium(III) in the environment (42).
There are no MRLs available for consumption of manganese in food or water. Consumption of water containing high levels of manganese has been linked to changes in development and neurological effects in experimental animals. Manganese is also an essential trace element. The highest concentration of manganese found in the groundwater at the site exceeds the Secondary MCL for the metal. Secondary MCLs are standards based on other criteria than health effects, such as taste, color, and odor. No health effects would be expected to be associated with the concentration levels detected at this site (43).
A child whose regular drinking water supply contains the maximum concentration of nickel found in the groundwater at the site could ingest enough of the metal to exceed the MRL for non-cancer health effects. Adults using the same water supply are not likely to exceed the MRL. Changes in the lungs and blood and reproductive and developmental effects have been seen in laboratory animals fed food or water containing high levels of nickel. Nickel refinery dust and some nickel compounds are classified as carcinogens (U.S. EPA Class A) by inhalation, though there is not sufficient information available to evaluate their carcinogenicity by ingestion. Inhalation is not a likely pathway for human exposure to nickel at this site. The highest nickel concentration found in the groundwater at this site exceeds the proposed MCL for the metal (44).
There are no MRLs published for exposure to zinc. Consumption of food containing high levels of zinc has been linked to digestive problems, changes in the immune system, and anemia. Experimental animals fed food or water containing very high concentrations of zinc have also experienced reproductive problems, pancreas, liver, and kidney damage. Zinc is also an essential trace element. The concentration of zinc found in the groundwater at the site exceeds a Draft Drinking Water Health Advisory issued by the U.S. EPA for the metal. The concentration also exceeds the Secondary MCL for the metal (45).
The groundwater samples from monitoring wells containing the highest concentrations of metals had not been filtered, most were colored brown, and were opaque with suspended solids. Because of the unattractive qualities of this water, people are not likely to drink large amounts of it. Samples that had been filtered contained much lower concentrations of these metals, indicating that the suspended solids contained a large part of the metals detected. Filtered samples or clear and colorless unfiltered samples did contain concentrations of manganese above the Secondary MCL, nickel above the proposed MCL, and zinc above the Draft Drinking Water Health Advisory and the Secondary MCL.
The MDPH/CDC Battle Creek Health Study (13) included interviews, medical examinations, blood testing for chemical residues, and reviews of medical records for 181 Verona Park residents; 16 Springfield residents; 54 Dowagiac, Cass County, residents; and 498 residents of nearby areas as a control population. The Springfield and Dowagiac residents had been exposed to similar chemicals to those found in the Verona Well Field area, though from sources not related to this NPL site. The study was a retrospective cohort study, comparing a group of people who were exposed in a contamination incident with a reference or control group who were not exposed, looking for differences in disease incidence or other health parameters during a specific time period.
The study found no excess of health disorders that could be attributed to exposure to VOCs. Diabetes, cancer (in women), miscarriages, skin rashes, and psoriasis occurred more frequently in the study group than in the control population, and gall bladder disease, hypertension, acne, and hives were less common in the study group than in the control population. Most of these health disorders are not known to be linked to VOC exposure.
The Study included examination of morbidity (hospital discharge) and mortality statistics. Standardized Mortality Ratios were calculated for Battle Creek City and Calhoun County from the period 1976 through 1980. Age-adjusted mortality rates for Calhoun County, Battle Creek, Springfield, Emmett Township, Pennfield Township, Cass County, and Dowagiac, for 1970-1984 were compared with statewide figures. Hospital discharge rate data for the Battle Creek area, Calhoun County, the Dowagiac area, and Cass County for 1982 and 1983 were compared with statewide figures. The applicability of this data was limited because the data in general was collected from relatively large areas and could not be extracted to focus strictly on the study and control areas. Increased mortality and hospital discharge rates for all cancer, leukemia, diabetes, liver diseases, and alcohol-dependency syndrome were observed for some of the study areas for one or more of the time periods studied. Where the data base allowed separation of data from Emmett and Pennfield Townships, which include the contaminated Verona area, from that from Battle Creek City, the mortality rates in the Townships were generally lower than in the City. The Study concluded that the available morbidity and mortality data could not support or refute a connection between exposure to VOCs and disease.
ATSDR's response to the health concerns voiced by the community follows.
- The community perceives an increased incidence of cancer, miscarriages, skin and nervous system disorders among themselves and their neighbors.
- The community has raised questions about the validity of the MDPH/CDC Battle Creek Health Study, specifically questioning whether there was a proper control group since the Battle Creek municipal water supply has been contaminated.
- Residents of the area are concerned that volatile chemicals may volatilize out of the groundwater and migrate through the soil to the surface or to their basements.
The MDPH/CDC Battle Creek Health Study found some variance in disease incidence between the residents of the Verona Well Field area and their control population, but no systematic increase in health effects that can be attributed to the contaminants at the site.
In addition to Battle Creek residents, the Health Study control groups included members of four communities where no contamination has ever been detected: Brownlee Park and Ceresco in Calhoun County, and Edwardsburg and Barron Lake in Cass County. As for the Battle Creek municipal water supply, the contaminant concentration in the finished water has been kept much lower than that in the private wells in the Verona Park area. There has been some concern about the presence of chloroform in the municipal water, a by-product of the chlorination process. The Health Study did address this issue by considering the combined exposure to the contaminants in the Verona Well Field and to chloroform.
As mentioned earlier, the concentrations of contaminants of concern, which may volatilize from the groundwater at the site into the unsaturated zone of the aquifer, could attain levels of health concern. However, dispersion and diffusion as the contaminants migrate through the soil are expected to reduce the concentrations at the surface or in basements below levels of health concern. The MDPH and the Calhoun County Health Department will offer to test the air in any basement in the area if the residents detect chemical odors that they believe may be associated with the site.
- The Verona Well Field site poses a public health hazard, due to the past history of exposure via groundwater and the potential for future exposure. Although use of the contaminated groundwater has been eliminated by a combination of institutional and technical controls, future exposures could occur if the remedial measures were interrupted or if residents used contaminated water from private wells for potable purposes. There are indications that some residents of the site are have resumed using private wells, for at least some purposes, in the contaminated area. No adverse health effects associated with the site contamination were identified in a health study of the site area.
- The subsurface soil in the source areas of the site contains contaminants. There is no available information on surface soil analysis for these areas.
- Until recently, there was no restriction on access to one of the source areas connected with the site.
- The MDPH/CDC Battle Creek Health Study provides a comprehensive investigation into the potential health problems relating to this site.
- Residents of the Verona Park area should be surveyed to identify any who have resumed use of their private wells. Residents of the area should be provided with information regarding the hazards of using private wells and advised strongly against doing so.
- Surface soil in the suspected contamination source areas should be analyzed for the presence of contaminants at levels of public health concern.
- Access to the Thomas Solvent Annex area should be restricted to reduce the opportunity for exposure to potentially contaminated soil and to prevent injury due to physical hazards. As of April 1993, this has been accomplished (2).
The Health Activities Recommendation Panel has evaluated the data and information developed for the Verona Well Field public health assessment for appropriate follow-up health actions. The panel determined that, because a comprehensive health study of the site area (13) has been performed, no further follow-up health activities are recommended at this time, beyond maintenance of the registry and community information and education as needed. The community health education should include information from the ATSDR Trichloroethylene (TCE) Subregistry Report. The site will be reevaluated for further health activities should evidence of further human exposure to contaminants or adverse human health effects be produced.
Public Health Action Plans (PHAP) are developed to describe actions to be taken by ATSDR and/or the Michigan Department of Public Health (MDPH) at and in the vicinity of sites subsequent to the completion of Public Health Assessments. The purpose of the PHAP is to ensure that Public Health Assessments not only identify public health hazards, but also provide a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment.
Future Health Actions:
- MDPH and ATSDR will carry out informational and educational activities related to the health assessment process at this site.
- ATSDR will maintain the Trichloroethylene Exposure Subregistry.
ATSDR and MDPH will coordinate with federal and state environmental agencies to carry out the recommendations in this assessment.
ATSDR will reevaluate and expand the Public Health Action Plan when needed. New environmental, toxicological, or health outcome data, or the results of implementing the above proposed actions and recommendations may determine the need for additional actions at this site.
John W. Filpus
Michigan Department of Public Health
Brendan T. Boyle
Health Assessment Coordinator
Michigan Department of Public Health
John L. Hesse
Michigan Department of Public Health
Michigan Department of Public Health
ATSDR Regional Representative
Regional Services, Region V
Office of the Assistant Administrator
ATSDR Technical Project Officer
Environmental Health Scientist
Division of Health Assessment and Consultation
Remedial Programs Branch
The Verona Well Field public health assessment was prepared by the Michigan Department of Public Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health assessment was initiated.
William J. Greim
Technical Project Officer, SPS, RPB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this health assessment and concurs with its findings.
Director, DHAC, ATSDR
- CH2M Hill. Remedial Investigation Report: Verona Well Field, Battle Creek, Michigan. August 1990.
- O'Brien, B., MDNR Site Manager. Personal Communication. June 25, 1993.
- Bloemker, J.W., MDPH Division of Water Supply. Personal Communication. July 9, 1993.
- Centers for Disease Control. Memo from Georgi A. Jones to Peter McCumiskey, U.S. EPA. August 1, 1983.
- Centers for Disease Control. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. August 31, 1983.
- Centers for Disease Control. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. September 15, 1983.
- Centers for Disease Control. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. March 12, 1984.
- Centers for Disease Control. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. May 1, 1984.
- Centers for Disease Control. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. July 12, 1984.
- Centers for Disease Control. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. January 25, 1985.
- Agency for Toxic Substances and Disease Registry. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. September 17, 1985.
- Agency for Toxic Substances and Disease Registry. Memo from Georgi A. Jones to Louise Fabinski, U.S. EPA. September 23, 1985.
- Freni, S.C., and Bloomer, A.W. Report on the Battle Creek Health Study. Michigan Department of Public Health, Lansing, MI. 1988.
- CH2M Hill. Feasibility Study: Verona Well Field, Battle Creek, Michigan, Public Comment Draft. February 1991.
- U.S. Environmental Protection Agency. Record of Decision, Verona Well Field Site. June 28, 1991.
- Rubitschun, C., Michigan Department of Public Health Division of Water Supply. Memorandum to Brendan Boyle, Subject: Draft Public Health Assessment, Verona Well Field, Battle Creek, Calhoun County. June 8, 1993.
- O'Brien, J.F., City of Battle Creek Public Works Department. Letter to Humphrey, H., MDPH. June 23, 1993.
- CH2M Hill. Technical Memorandum, Phase II, Drilling and Soil Sampling, Verona Well Field, Battle Creek, Michigan. May 17, 1985.
- Michigan Department of Public Health, Division of Water Supply. Files. 1990.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for 1,1-Dichloroethane. ATSDR/TP-90/12. December 1990.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for 1,2-Dichloroethane, Update, Draft for Public Comment. October 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for 1,1-Dichloroethene. ATSDR/TP-89/11. December 1989.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for 1,2-Dichloroethene. ATSDR/TP-90/13. December 1990.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Tetrachloroethylene, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry, Toxicological Profile for 1,1,1-Trichloroethane. ATSDR/TP-90/27. December 1990.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Trichloroethylene, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Vinyl Chloride, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Benzene, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Ethylbenzene. ATSDR/TP-90/15. December 1990.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Toluene, Update, Draft for Public Comment. October 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Total Xylenes. ATSDR/TP-90/30. December 1990.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Acetone, Draft for Public Comment. October 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for 2-Butanone. ATSDR/TP-91/08. July 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Di(2-ethylhexyl)phthalate, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Cresols. ATSDR/TP-91/11. July 1992.
- National Institute for Occupational Safety and Health and Occupational Safety and Health Administration. Occupational Health Guideline for Hexachloroethane. September 1978.
- North Carolina. North Carolina Toxic Substances Management Guide -- Hexachloroethane. no date (ca. 1981).
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for N-nitrosodi-n-propylamine. ATSDR/TP-89/18. December 1989.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Antimony. ATSDR/TP-91/02. September 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Arsenic, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Cadmium, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Chromium, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Manganese. ATSDR/TP-91/19. July 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Nickel, Update, Draft for Public Comment. October 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Zinc, Update, Draft for Public Comment. October 1992.
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Bromoform/Chlorodibromomethane. ATSDR/TP-90/05. December 1990.
1. Pica behavior is an abnormal consumption of non-food materials, such as soil, most often seen in children under 5 years of age.
2. The U.S. EPA has withdrawn the classification for trichloroethylene, pending review of the data on the chemical's carcinogenicity.