PUBLIC HEALTH ASSESSMENT
NORTH BRONSON INDUSTRIAL AREA
BRONSON, BRANCH COUNTY, MICHIGAN
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 and medium-specific comparison value. Lifetime exposure to chemical concentrations at or below the appropriate comparison values for a chemical is not expected to result in more than 1 excess case of cancer in 1 million people exposed or any noncancer health effects. Comparison values used in this assessment include the following, developed by the Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA):
ATSDR environmental media exposure guides (EMEGs)
ATSDR cancer risk evaluation guides (CREGs)
ATSDR reference dose media evaluation guides (RMEGs): Concentrations computed from the EPA Reference Dose (RfD) for chronic exposure of a child, assuming pica behavior for soil ingestion4
EPA Drinking Water Lifetime health advisories (LTHAs)
EPA Safe Drinking Water Act maximum contaminant levels (MCLs)
EPA Safe Drinking Water Act maximum contaminant level goals (MCLGs)
If a chemical is found in a medium for which no comparison values exist, or for which there is no CREG available for a carcinogen, the chemical is retained as a contaminant of concern.
To identify chemicals that might contribute to the environmental contamination at the North Bronson Industrial Area (NBIA) site after industrial releases in the site area, the Michigan Department of Public Health (MDPH) searched the Toxic Chemical Release Inventory (TRI) data base for 1987 through 1993. EPA compiles the TRI from information provided by industries. The TRI contained entries for two facilities with the same postal ZIP Code as the NBIA site, the Bronson Plating Company facility and one identified as Kuhlman Plastics Group (1987-1989) or Solvay Automotive Inc. (1990-1992). Both facilities are located within the site study area.
Bronson Plating reported releases to the air of sulfuric acid, hydrochloric acid, nickel, and chromium. They released copper, nickel, and chromium to the water of Swan Creek (1987-1990) and County Drain # 30 (1991-1993). They also reported use, but no environmental releases or transfers to other disposal facilities, of phosphoric acid and sodium hydroxide (solution).
Kuhlman Plastics Group or Solvay Automotive Inc. reported releases to the air of ammonia and sulfuric acid. They also reported transfers to the Bronson Wastewater Treatment Plant, with no environmental release, of ammonium sulfate (solution) and ethylene glycol.
Chromium, copper, and nickel, released by the Bronson Plating facility, are included as contaminants of concern based on the previously mentioned criteria. The other chemicals reported as released by the facilities are highly volatile and do not tend to persist as environmental contaminants.
For this assessment, samples collected within the site study area are considered on-site samples.
Groundwater -- Private and Municipal Wells
On many occasions since 1974, various environmental and health agencies have collected samples of water from private residential wells located within the NBIA site study area. A total of four wells have been sampled (RW-1 through RW-4 in Figure 2), but not all at any one time, and the analyses performed varied from agency to agency and time to time. The chronology of the private well sampling, both within and around the site study area, is summarized in Table 2. A cross-reference list between this assessment and the numbering systems in the RI report (Reference 1) is given in Table 3.
In 1974, samples of water from a private residential well south of the western lagoon area (RW-1 in Figure 2) contained approximately 5,000 parts per billion (ppb) each of acetone and methyl ethyl ketone (MEK).5 Water from dewatering wells for construction at the Bronson municipal Wastewater Treatment Plant, southeast of the west (old) lagoons and northeast of RW-1 (Figure 2), also contained acetone and MEK, at concentrations of approximately 1,000 ppb.
In October 1984, the MDPH Division of Water Supply6 collected a water sample from a private residential well in the site study area (RW-2 in Figure 2), and analyzed the sample for bacteria, VOCs, cyanide, and metals. None of these parameters were detected in the analysis (6).
In September 1988 and September 1989, the Michigan Department of Natural Resources, (MDNR's) RI contractors collected samples from a residential well (RW-2, see Figure 2) and a municipal well (PW-3) within the boundaries of the NBIA site study area, analyzing the samples for a full range of organic and inorganic chemicals. No organic chemicals or other contaminants attributable to the site was detected in the samples from these wells. The samples did contain low concentrations of several metals that are considered contaminants of concern at the site (Table 4), but these concentrations were generally comparable to background levels.
In December 1988, the MDPH collected a water sample from a private well located within the site study area (RW-3, next door to RW-2, see Figure 2). This sample contained 457 ppb trichloroethylene, 24 ppb cis-1,2-dichloroethylene, 1 ppb trans-1,2-dichloroethylene, 6 ppb vinyl chloride, and 2 ppb 1,1-dichloroethylene.7 The residence served by RW-3 was later connected to the municipal water system, and the well abandoned (7). The residence burned down in 1992 and has not been rebuilt as of this writing.
In January 1989, the MDPH collected additional water samples from RW-1 and RW-2. They found no organic chemicals in either sample, and did not analyze them for any inorganic contaminants of concern (7). In February 1990, the MDPH collected a sample of water from Bronson Municipal Well PW-3, within the site study area. The sample contained no organic chemicals but did contain 120 ppb manganese, a concentration higher than the ATSDR comparison value (50 ppb) and higher than background levels (1). In July and October 1993, the MDPH collected samples from RW-2 and one other residential well (RW-4, see Figure 2) within the site study area. These samples contained trichloroethylene (up to 82 ppb) and traces of 1,1,1-trichloroethane (up to 0.7 ppb).8 Both residences have since been connected to the municipal water system.
Groundwater -- Monitoring Wells
In 1974, water from dewatering wells around construction at the Bronson Wastewater Treatment Plant, located adjacent to the west lagoons in the site study area, contained approximately 1,000 ppb of acetone and methyl ethyl ketone. Water samples collected in 1979 from monitoring wells around the western lagoons contained trichloroethylene (TCE) and heavy metals (Table 5). Groundwater samples collected in 1981 from monitoring wells around the eastern lagoons and Bronson Plating contained TCE, chloroform, and heavy metals (Reference 1, concentrations not cited).
MDNR's RI contractors collected samples of groundwater from monitoring wells in the site study area in 1988, 1989, and 1991. Concentrations of contaminants of concern are summarized in Table 5. They found a plume of chlorinated ethylenes (vinyl chloride, 1,1-dichloroethylene, 1,2-dichloroethylene, and trichloroethylene) under much of the site study area. The highest concentrations (up to 70,200 ppb total) were found under the former Scott Fetzer Components Corporation plant in the southern section of the area. Lower concentrations of these chemicals (100-1,000 ppb) were found in the groundwater under the lagoon areas. Elevated concentrations of metals were found in several isolated plumes, including one under each of the lagoon areas (cadmium, cyanide, manganese, and nickel under the eastern lagoons; cadmium, cyanide, lead, manganese, nickel, and zinc under the western lagoons) and a cyanide plume along Mill Street. The two private wells (RW-2 and RW-4) where trichloroethylene was found in the 1993 MDPH sampling are within the organic plume, close to the area where the maximum concentration was found in the monitoring wells.
During the RI investigation in 1991, the MDNR's contractors collected samples of surface soil, 0 to 6 inches deep, from a ball field on the east side of the site area (a background sample), the vacant L.A. Darling site, the former Scott Fetzer Components Corporation plant, and the "Cyanide Destruction" facility. The concentrations of contaminants of concern found in these samples are summarized in Table 6. Most of these contaminants were heavy metals, with the highest concentrations primarily found in samples from the former "Cyanide Destruction" Facility.
During the RI in 1988, the contractors collected samples of subsurface soil from the berms between the lagoons (Table 7). In 1989, the contractors collected soil samples from borings near the eastern lagoons, and from monitoring well borings throughout the site (metals analyses only) (Table 8). In 1991, they collected soil samples from borings located throughout the site study area (also in Table 8). The highest concentrations of polycyclic aromatic hydrocarbons (PAHs) were found in the shallowest samples (1 foot depth) from three borings located northeast of the L.A. Darling site. The arsenic, beryllium, manganese, thallium, and vanadium concentrations from 1989 listed in Table 8 were all from one sample, from 10 feet down in a boring for a monitoring well south of the western lagoons. A duplicate of this sample contained much lower concentrations of these metals (6.4 ppm vs. 95.9 ppm, not detected at 0.26 ppm vs. 157 ppm, 353 ppm vs. 5,160 ppm, not detected at 0.24 ppm vs. 19.4 ppm, and 9.2 ppm vs. 84.9 ppm, respectively) and substantially different concentrations of other metals. The 1989 concentrations of cadmium, chromium, cobalt, copper, nickel, and zinc listed in Table 8 were all from a single sample, collected 10 feet below the surface near the eastern lagoons.
Lagoon surface water and sludge
MDNR's RI contractors collected samples of surface water from the western lagoons and samples of sludge from the eastern lagoons in 1988. They collected sludge samples from the western lagoons in 1989 and an additional water sample from the western lagoons in 1991. Concentrations of contaminants of concern found in these samples are summarized in Table 9 (water) and Table 9 (sludge). The contaminant concentrations in sludge samples from the eastern lagoons were substantially higher than those in sludge from the western lagoons.
Groundwater -- Private Wells
On many occasions since 1984, various environmental and health agencies have collected samples of water from private residential wells located near the NBIA site study area. A total of 19 wells have been sampled (RW-5 through RW-23 in Figure 2), but not all at any one time and the analyses performed varied from agency to agency and time to time. The chronology of the private well sampling is summarized in Table 2. A cross-reference list between this assessment and the numbering systems in the RI report (Reference 1) is given in Table 3.
In October 1984, MDPH collected water samples from three private residential wells near the site study area, one to the west (RW-5 in Figure 2) and two north (RW-6 and RW-7). They analyzed the samples for bacteria, VOCs, cyanide, and metals. None of these parameters were detected in the analysis (6).
In September 1988 and September 1989, MDNR's RI contractors collected samples from four residential wells in the site vicinity, RW-5, RW-6, RW-7, and one south of the site study area (RW-8), and analyzed the samples for a range of organic and inorganic chemicals. No contamination attributable to the site was detected in these wells. The samples did contain low concentrations of several metals that are considered contaminants of concern at the site (Table 11), but these concentrations were generally comparable to background levels.
In January 1989, the MDPH collected water samples from RW-8 and from four other residential wells in the site vicinity (RW-9 through RW-12), analyzing the samples for VOCs and general chemical parameters. In July 1993, MDPH collected water samples from RW-8, RW-9, RW-10, and five more residential wells near the NBIA site (RW-13 through RW-17), analyzing the samples for VOCs. In July 1995, the Branch County Health Department and the MDPH collected water samples from 14 private wells near the NBIA site study area, including RW-5, RW-8, RW-9, RW-10, RW-11, RW-13, RW-14, RW-15, and 6 new wells (RW-18 through RW-23), analyzing the samples for VOCs. None of these samples contained any VOCs and they were not analyzed for any inorganic chemicals of concern at the site (7). In August 1995, MDNR collected water samples from RW-6, RW-7, and six private wells along Burr Oak Road, northwest of the site (RW-24 through RW-29), analyzing the samples for VOCs, metals, and cyanide. These likewise did not contain any VOCs. They did contain low concentrations of some metals that are contaminants of concern at the NBIA site (Table 11) (8).
Groundwater -- Monitoring Wells
MDNR's RI contractors constructed monitoring wells north and south of the site study area to provide background samples of groundwater. They sampled these wells in 1989 and 1991. No organic chemicals were found, and the concentrations of metals found are summarized in Table 12.
In 1991, MDNR's RI contractors collected four samples of surface soil (to 6 inches deep) from areas southwest and north of the site to provide background data (Table 13). These concentrations were generally within the range of concentrations found in Michigan (9) and the Eastern United States (10).
In 1989, MDNR's RI contractors collected samples of soil at 5-foot depth from the borings for the off-site monitoring wells, and analyzed the samples for metals (Table 14). Again, these concentrations were generally within the range of concentrations found in Michigan (9) and the Eastern United States (10).
Surface water and sediment
Samples of sediment collected in 1979 from County Drain #30 contained elevated concentrations of polychlorinated biphenyls (PCBs) downstream from the western lagoons (Reference 1, concentrations not cited). MDNR's RI contractors collected sediment and surface water samples from County Drain #30 upstream from the site, adjacent to the site, and downstream from the site in 1988 and 1991. Concentrations of contaminants of concern in these samples are summarized in Table 15 (sediment) and Table 16 (surface water). They found some chemicals at elevated concentrations in the samples collected adjacent to the site, but none significantly elevated either upstream or downstream. The PAH concentrations in sediment samples collected adjacent to the site were generally within the range found in urban soils (Reference 11, Table 5-2). In 1991, they also collected samples of water from several outfalls into the drain from the site area. The outfall samples contained more chromium, 1,2-dichloroethylene, TCE, vinyl chloride, and PAHs than did samples from the creek upstream of or at the site (Table 16).
In preparing this 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 regards 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.
The analysis for metals of one pair of duplicate subsurface soil samples yielded concentrations that varied by an order of magnitude or more. This suggests that there may have been some interference with the analysis, and the results for all soil samples analyzed at the same time may be questionable.
Access is not restricted at the outer perimeter of the site. Such restriction would be impractical considering the large number of residences and businesses within the site area. Individual businesses and residences are fenced for privacy and security. The lagoons areas are not fenced, though the east lagoons area is surrounded by operating industrial properties. The west lagoons area is located a substantial distance from any residences or other facilities, except for the wastewater treatment plant.
The former Scott Fetzer "Cyanide Destruction" facility is filled with debris
from collapsed buildings, and what buildings remain are in a state of imminent
collapse. The north side and part of the east and west sides of the facility
have long been fenced, but the remainder of the east and west sides and the
south side were not fenced, with free access from adjacent residential yards.
In May 1996, MDEQ removed one collapsing building from the property and installed
a new fence around the entire property.
To determine whether nearby residents are exposed to contaminants migrating from the site, the Agency for Toxic Substances and Disease Registry (ATSDR) evaluates the environmental and human components that lead to human exposure. An exposure pathway contains five major elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population.
An exposure pathway is considered a completed pathway if there is evidence that all five of these elements are or have in the past been present. A pathway is considered a potential pathway if one or more of these elements is not known to be or have been present, but could be or have been. An exposure pathway can be eliminated from consideration if one of the elements is not present and could never be present. The following sections discuss the most important exposure pathways at this site.
Groundwater -- Private wells
Residents of the site study area have used water from private wells that was contaminated with trichloroethylene, other volatile organic compounds (VOCs), and metals. Alternative water supplies were provided to these residents and the contaminated wells abandoned soon after the contamination was identified. The records show that four private wells have been contaminated. From the normal residential density of 3.8 per house, this means approximately 15 people would have been exposed.
Soil at the former "Cyanide Destruction" facility and at the former L.A. Darling property contain elevated concentrations of metals (Table 6). Access to these areas is not sufficiently restricted. There are reports that children go onto the former "Cyanide Destruction" facility property freely. There are 14 houses on the block adjacent to the "Cyanide Destruction" facility, with yards contiguous to the facility grounds and no obstruction to traffic between the facility grounds and the yards. The resident population adjacent to the facility property, the people most likely to frequently go onto the site, is estimated to be approximately 50 persons. People visiting these residences might also occasionally visit the facility property.
VOCs present in the sludge and soil at the site might volatilize into interstitial gas in the soil (soil gas), diffuse to the surface, and be carried by the wind to neighboring residential areas. Alternatively, the contaminants might migrate with the soil gas to nearby basements, diffuse through the walls or floor, and collect in the confined space of the basements. The remedial investigation report includes no results of ambient air, residential air, or soil gas sampling and analysis in the site study area. The baseline risk assessment includes the results of modeling of VOC emissions from the soils on-site, concluding that residents in the site vicinity may incur a significant risk of both noncancer and cancer adverse health effects (12). The assessors noted that the calculation of the hazard for noncancer adverse health effects includes a mathematical error that makes the hazard appear to be significant when the hazard calculated without this error would not be significant.9 Such models are only as reliable as the calculations and assumptions they are based on.
Surface water and sediment
Water and sediment in County Drain #30 contain VOCs, polychlorinated biphenyls,
polycyclic aromatic hydrocarbons, other semi-volatile organic chemicals, and
metals at concentrations in excess of the ATSDR comparison values. Access to
the drain, which is an open creek or ditch in the site area is not restricted.
The Michigan Department of Community Health has not heard any report of children
playing in the drain; however, the drain could attract children from the area
for their play.
The primary benchmarks against which exposures are evaluated for their potential for causing noncancer adverse health effects are the minimal risk levels (MRLs), developed by the Agency for Toxic Substances and Disease Registry (ATSDR), and reference doses (RfDs) and reference concentrations (RfCs), developed by the Environmental Protection Agency (EPA). It is generally accepted that a person exposed to a dose of a chemical less than an MRL, RfD, or RfC is not likely to experience non-cancer adverse health effects. The MRLs, RfDs, and RfCs are lower than the observed threshold exposures, with safety factors included to allow for different responses between species and between individuals. However, these values may not be protective for individuals who are hypersensitive to chemical exposures, including the very young, the very old, individuals whose bodies are under stress from illness, and individuals who have an allergic response to the chemical.
Threshold exposures from which MRLs, RfDs, and RfCs are derived may also be cited if none of the derived values are available. The threshold exposures include lowest-observed-adverse-effect levels (LOAELs) and no-observed-adverse-effect levels (NOAELs). In a given experiment, with exposure route, species, and health effect specified, the LOAEL is the lowest exposure at which the effect was observed, and the NOAEL is the highest exposure at which no effect was observed.
For chemicals that may cause cancer, the risk associated with an exposure is evaluated separately from noncancer health risks, using published potency factors, which relate the chance of contracting cancer to the dose of the chemical. For this assessment, the risk of cancer is considered significant if 1 extra case of cancer is likely to develop among 1,000,000 people subject to the exposure over their lifetimes.
Exposure doses for this assessment are computed using the following standard assumptions (10): an adult weighing 70 kilograms (154 pounds) who drinks 2 liters (approximately 2 quarts) of water a day and incidentally ingests 100 milligrams of soil per day; a child weighing 10 kilograms (22 pounds) who drinks 1 liter (approximately 1 quart) of water per day and incidentally ingests 200 milligrams of soil per day, or, if subject to pica behavior, deliberately ingests 5,000 milligrams of soil per day. Pica behavior is an abnormal urge to consume non-food substances, such as soil, that most commonly occurs between ages 2 and 5.
Our evaluation estimates exposures to contaminants in the groundwater from the maximum concentrations found in water from residential wells in the site study area (Table 4). Higher concentrations of some contaminants were found in water from monitoring wells closer to the source areas than the private wells (Table 5), however, since the contaminated private wells were removed from service when the contamination was detected, people are not likely to be exposed to those levels of contaminants.
The time during which a private well user might have used contaminated water from their well is difficult to estimate for three of the four contaminated private wells at the site. For RW-1, RW-3, and RW-4, the sampling that found the contamination was the first sampling of water from the well on record. Water from RW-2 contained no organic contaminants when it was sampled in September 1988, January 1989, and September 1989, but the well was found to be contaminated in July 1993. The residents were then advised to not use the water from their well. A well at a neighboring house (RW-3) had been found to be contaminated in December 1988. The documented exposure of the people who used water from RW-2 lasted for not more than 4 years.
Volatile chemicals in water tend to evaporate when the water is used for showers, washing, and other household uses. A person taking a shower using water contaminated with volatile chemicals can inhale the volatilized chemicals, and thereby can be exposed to as much of the chemicals as they would ingest while consuming the water. Calculation of inhalation exposures to VOCs during showering are estimated from the model developed by Little, specifically the results of his computations plotted in Figure 5 of his paper. The results were based on a 10 minute shower using 13.7 L/min. water (3.6 gallons/minute) (13).
Anyone drinking the water from a residential well in the site study area or using the water for showers might have ingested enough acetone to exceed the RfD for non-cancer adverse health effects, but not enough to exceed the doses at which adverse health effects have been observed in published studies on animals or humans. There is no information available that links exposure to acetone with cancer (14).
Methyl ethyl ketone
No one is likely to have ingested enough methyl ethyl ketone (also known as 2-butanone or MEK) from the water from a residential well in the site study area to exceed the RfD for noncancer adverse health effects. The MEK concentration in the air of a shower using water from RW-1 might have exceeded the RfC for noncancer adverse health effects, but would not likely have exceeded the levels at which adverse noncancer health effects have been observed. No available evidence available links exposure to MEK with cancer (15).
No one was likely to ingest enough TCE from the water from the residential wells to exceed the MRL for noncancer adverse health effects from intermediate-term exposure. The concentration of TCE in the air of a shower using residential well water from the site study area might have exceeded the MRL for noncancer adverse health effects, but not the levels at which adverse health effects have been observed. The epidemiologic data on cancer incidence in humans exposed to TCE are ambiguous. Some experimental animals whose food and water contained TCE have developed liver cancer. EPA had classified TCE as a probable human carcinogen (EPA Class B2), but has withdrawn the classification pending further review (16). A lifetime's use of water, for either drinking or showering, containing the concentrations of TCE in the residential wells at the site would result in a low increased risk of contracting cancer. The private wells were taken out of service and alternative water supplies provided to the residents as soon as the contamination was detected. The residents would not be likely to have used the wells for a long enough period to incur any increased risk of contracting cancer from the TCE by either inhalation or ingestion.
Anyone might have ingested enough vinyl chloride in water from a residential well in the site study area to exceed the MRL for non-cancer adverse health effects from chronic exposure by ingestion, but not enough of the chemical from this residential well to exceed the doses at which adverse non-cancer health effects have been observed. The concentration of vinyl chloride in the air in the shower using water from that well would exceed the MRL for intermediate-term exposure by inhalation, but would not exceed the levels at which adverse non-cancer health effects have been observed in epidemiological or laboratory animal studies. Some workers occupationally exposed to vinyl chloride developed liver cancer, and some laboratory animals whose feed contained the chemical developed liver cancer. The U.S. EPA has classified vinyl chloride as a known human carcinogen (U.S. EPA Class A) (17). As of this writing, the U.S. EPA is reviewing the cancer potency factor for vinyl chloride (18). Based on the previously available potency factor, lifetime use of water containing the concentration of vinyl chloride found at the site could result in a low increased risk of contracting cancer through either ingestion or inhalation. The one residential well that contained vinyl chloride when sampled was replaced with an alternative water supply and the well abandoned. The residents of the site study area were not likely to have used the contaminated water long enough to incur any significant increased risk of contracting cancer or to incur any noncancer adverse health effects.
No one is likely to ingest enough 1,1-dichloroethylene from the residential wells at the site to exceed the MRL for non-cancer adverse health effects. The air in a shower that used water from the site would not be likely to contain enough 1,1-dichloroethylene to exceed the MRL for non-cancer adverse health effects. Some laboratory animals who breathed air, ate food, or drank water containing 1,1-dichloroethylene contracted cancer of various organs. The U.S. EPA has classified 1,1-dichloroethylene as a possible human carcinogen (U.S. EPA Class C) (19). A person who drank water from the site area for his or her lifetime might ingest enough 1,1-dichloroethylene to incur a low increased risk of contracting cancer. He or she would not be likely to inhale enough of the chemical during his or her showers to incur any increased cancer risk. The residential well where the water contained 1,1-dichloroethylene has been replaced by a connection to municipal water. The people who used that residential well would not be likely to have ingested enough of the chemical to incur any apparent increased cancer risk.
Metals in groundwater
A child might ingest enough arsenic from the residential wells on and near the North Bronson Industrial Area (NBIA) site study area to exceed the MRL for noncancer adverse health effects, but not enough of the metal to exceed the concentrations at which adverse health effects have been observed. The scientific literature includes epidemiological studies that indicate that people exposed to high concentrations of arsenic in their food or water run an increased risk of contracting cancer of the skin. The studies also linked exposure to arsenic with increased occurrence of cancer of liver, lung, and bladder, though the linkage has not been proven. EPA has classified arsenic as a known human carcinogen (EPA Class A) (20). A person using groundwater from the site area for their drinking water source for his or her lifetime might ingest enough arsenic to incur a moderate increased risk of contracting skin cancer. The arsenic concentrations found in the groundwater in the site area are less than EPA's maximum contaminant level of 50 ppb. The arsenic is probably of natural origin, and the concentrations found are not unusually high for that part of Michigan.
No one is likely to ingest enough beryllium from the groundwater in the site vicinity to exceed the RfD for noncancer adverse health effects. Some laboratory animals whose diet contained beryllium developed lung cancer. EPA has classified beryllium as a probable human carcinogen (EPA Class B2) (21). A person whose water supply for his or her lifetime contains the beryllium concentration found in the groundwater on and near the NBIA site study area might incur a low increased risk of contracting cancer. None of the beryllium concentrations in water from the residential wells exceeded the EPA MCL for the metal (4 ppb).
No MRLs or RfDs available for exposure to lead. The lead content of water from residential wells in the site study area did not exceed the EPA proposed action level for lead in drinking water (15 ppb), though the concentration in a monitoring well did. A child whose drinking water contained the lead concentration found in that monitoring well might ingest enough of the metal to attain the dose at which people dosed with lead acetate for a period of 7 weeks experienced decreases of the activity of enzymes involved in blood synthesis. Laboratory animals whose food or water contained similar amounts of lead for their body weight suffered neurological problems. Lead is known to contribute to neurological and developmental problems in children, but the presence of other sources of the metal in the environment and the metal's tendency to accumulate in the body complicate the evaluation of a specific exposure. Some laboratory animals whose diet or water contained lead developed kidney cancer. The U.S. EPA has classified lead as a probable human carcinogen (EPA Class B2). Not enough evidence is available to evaluate the cancer risk from exposure to lead (22).
A child might ingest enough manganese from the water in the residential or municipal wells in and near the site study area to exceed the RfD, but not sufficient to exceed the doses at which non-cancer adverse health effects have been observed. There is no evidence available linking exposure to manganese with cancer (23).
Metals in surface soil
A child subject to pica behavior10 might ingest enough surface soil from the site study area to exceed the MRLs or RfDs for any of the metals present. The pica child would not be likely to ingest enough of the metals present to attain the doses at which adverse health effects have been observed in laboratory animals (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33). However, lead is a cumulative poison, and long-term exposure to low levels can result in adverse health effects. The lead concentrations found in the surface soil on the site are within the range commonly found in urban areas (22) and less than the health-based clean-up level for lead in soil (400 ppm) developed by the Michigan Department of Environmental Quality (MDEQ) under provisions of the Michigan Environmental Response Act (Public Act 451, Part 201, as amended). Lifetime exposure to the concentrations of arsenic and beryllium present on the site might result in a low increased risk of contracting cancer (20, 21). The other carcinogens present, cadmium, chromium(VI), and nickel, have primarily been recognized as carcinogens through inhalation, and there is not sufficient information to evaluate the cancer risk from other pathways of exposure (24, 25, 26). Chromium(VI) compounds tend to be reduced to chromium(III) compounds in the environment (24), though no information is available as to which chromium species are present at the site.
Contaminants in sediments in County Drain #30
A child playing in County Drain #30 near the site one day a week might incidentally ingest sediments that contain enough cadmium to exceed the MRL for chronic exposure and enough chromium to exceed the RfD for chromium(VI), but not enough of either metal to exceed the LOAELs (24, 25). Cadmium and nickel have primarily been recognized as carcinogens through inhalation, and information is insufficient to evaluate the cancer risk from other pathways of exposure (25, 26). Chromium(VI) compounds tend to be reduced to chromium(III) compounds in the environment (24), though no information is available about which chromium species are present in the sediment.
No one is likely to spend enough time in the ditch over a lifetime that incidental ingestion of sediments would result in a significantly increased risk of contracting cancer from any of the contaminants for which cancer slope factors are available.
Lead is a cumulative poison, and long-term exposure to low levels can result in adverse health effects. The lead concentrations found in the sediment are within the range commonly found in urban areas (22) but exceed than the health-based clean-up level for lead in soil (400 ppm) developed by the MDEQ under provisions of the Michigan Environmental Response Act (Public Act 451, Part 201, as amended).
Various polycyclic aromatic hydrocarbons (PAHs), including acenaphthylene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene, benzo(a)pyrene, chrysene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, 2-methylnaphthalene, naphthalene, and phenanthrene, were found in samples of sediments from County Drain #30. MRLs and RfDs for noncancer adverse health effects are not available for these PAHs. PAHs are ubiquitous in the environment, as products of incomplete combustion. The concentrations found in the sediments were generally within the range found in urban soils (Reference 11, Table 5-2), and it is not likely that any significant increase in adverse health effects would result from exposure to the sediments. EPA has classified benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, chrysene, dibenzo(a,h)anthracene, and indeno(1,2,3-cd)pyrene as probable human carcinogens (EPA Class B2). Animals whose food contained these PAHs or who had the chemicals applied to their skin for long periods developed cancer. Incidental ingestion of sediments from the creek would not result in any significant increased risk of contracting cancer (11, 34). Laboratory animals who developed cancer when PAHs were applied to their skin were exposed to either the pure chemicals or comparatively high concentrations in liquid solvents. No evidence is available that skin contact with soil containing the PAH concentrations generally found in the environment, such as those found in the sediments of County Drain #30, poses any significant increased risk of contracting cancer.
Volatile organic chemicals in basement air
No data are available on the concentrations of organic chemicals in ambient air at the site. As an upper-limit, worst-case scenario, the following discussion considers the concentrations of the various chemicals present in the water that would be present in air in equilibrium with the water. These are the concentrations that would be in the air in a closed container that also contains water containing the highest concentrations of VOCs found in groundwater in the site study area. This is the highest possible concentration of the chemicals in the air or in soil gas at the site. In the open air, those concentrations would only be found at the surface of the water. Diffusion and dispersion involved in the movement of gases through the soil and into the air will greatly reduce the concentrations encountered in the ambient air. The air of a confined space such as a basement, where the chemicals have not had the opportunity to disperse, might contain the chemicals at concentrations comparable to the equilibrium level.
The concentration of vinyl chloride in air in equilibrium with the groundwater in the site study area, as might be found in a basement, might exceed MRLs and the levels at which decreased longevity, minor changes in various organs, and increased rates of cancer were observed in laboratory animals who breathed the air for 2 weeks or more. Breathing this air for a lifetime might result in an extremely high increased risk of contracting cancer (17). The concentrations of 1,2-dichloroethylene and trichloroethylene in air in equilibrium with the groundwater might exceed available MRLs, though the concentrations would not be likely to exceed the levels at which adverse health effects have been observed (16, 35). Breathing air with this concentration of trichloroethylene for a lifetime might result in a very high increased risk of contracting cancer (16). Other VOCs present in the groundwater would not likely be in the air at concentrations above available MRLs, levels at which adverse noncancer health effects have been observed, or that would result in more than a low increased cancer risk (19, 36, 37, 38, 39). As described previously, these conclusions are based on the highest possible concentrations in the air, and dispersion through the soil and air would likely reduce the concentrations people would be exposed to. Actual data on basement air concentrations are needed to accurately evaluate the health hazard.
The baseline risk assessment in the remedial investigation (RI) includes calculations based on a mathematical model for the emission of VOCs from the subsurface soil at the site. The modeled concentration of methylene chloride, calculated for a point 100 meters downwind of the eastern lagoons as given in Table B-12 in Reference 12, exceeds the intermediate-term inhalation exposure MRL for noncancer adverse health effects, but not the concentrations at which adverse health effects have been observed (36). None of the other concentrations in Table B-12 in Reference 12 exceed available MRLs, RfCs, or levels at which adverse noncancer health effects have been observed (14, 15, 16, 36, 40, 41, 42, 43). Among the VOCs found in the soil samples, chloroform, methylene chloride, and trichloroethylene are or have been classified as probable human carcinogens (EPA Class B2) (16, 36, 40). Living 100 meters downwind of the eastern lagoons for a lifetime might result in a low increased risk of contracting cancer.
A resident of Bronson has expressed concern about a perceived high rate of cancer within the city. The Michigan Department of Community Health (MDCH) Environmental Epidemiology Division has requested cancer incidence data for the city of Bronson from the MDCH Office of the State Registrar and Division of Health Statistics.
It was reported that a resident of the site study area whose private well was contaminated has contracted cancer. A MDCH toxicologist spoke to the resident regarding the possible association between the contaminants in the groundwater and her illness. He was unable to determine if her exposure to contaminated groundwater caused her illness.
Because fewer than half a dozen private wells were affected by contaminated groundwater, it is not possible to evaluate the relationship between exposure to contaminants at this site and disease incidence with any statistical confidence in the results.
1. The Scott Fetzer "Cyanide Destruction" facility is dangerous. It should be fenced or cleaned up.
MDCH agrees that the facility is dangerous, both from the physical hazard and from the chemical contamination present. Michigan Department of Public Health (MDPH) staff present at the June 15, 1995, Michigan Department of Natural Resources (MDNR) public meeting (Brendan Boyle, Michelle Borgialli, and John Filpus) strongly supported MDNR efforts to restrict access to the "Cyanide Destruction" facility or to have it cleaned up promptly.
2. Our city water has a lot of iron in it.
MDPH Division of Water Supply personnel report that the Bronson municipal wells have had a history of elevated iron, hardness, and (occasionally) nitrate levels. High concentrations of iron in drinking water are not considered to be hazardous to human health, though the metal can make the water unsightly, give it a poor taste, discolor fixtures, or interfere with the operation of water heaters and softeners. Bronson voters had rejected a proposal to fund an iron-removal system for their water treatment plant. The occasional high nitrate concentrations have been attributed to a source near one of the existing city wells, and the city controls the nitrate level in the water system through adjusting the pumping rates of the wells. Water from the system is sampled and analyzed for nitrates every quarter (last sampled in late 1995).
Water from the system is also tested every month for bacteria, every year for lead and copper (last sampled in the summer of 1995), and every 3 years for VOCs (last sampled in 1992, a new sample should be collected soon, as of January 1996). Except for iron, hardness, and nitrates, none of the analyses have found any parameter above the EPA's Safe Drinking Water Act standards, either the MCLs, based on health concerns, or the secondary MCLs, based on other aesthetic considerations such as appearance, odor, and taste. The city's well #3, located within the boundaries of the NBIA site study area, has been abandoned and is no longer in use. Their two remaining wells are east of the town and upgradient of the contamination at the NBIA site (5).
3. Can the chemicals in the soil and groundwater affect the vegetables in our gardens?
Most garden plants rely on rain for their water needs. Their root systems are not extensive enough to reach groundwater in most places. Contamination of food plants is most likely to occur through contamination in the soil or in irrigation water. The questioner uses municipal water on the garden, which eliminates that possible route for contamination. There is no information on whether the soil in residential areas of the site study area is contaminated; however, the soil at the "Cyanide Destruction" facility is contaminated with various metals. Some contamination from the facility may have migrated to neighboring residential yards, including that of the questioner. Of the metals found in the soil of the facility, enough cadmium is known to be taken up by plants such that the concentration in the plants could reach a potentially hazardous level. The baseline risk assessment includes estimations of the health risk from eating plants that had grown in soil at the site. MDCH accepts this analysis and concurs with the conclusion that the risk is not significant, especially considering that the concentrations of the metals are likely to be much lower in gardens off the site than in the soil on the site (12).
4. What are the type of health effects that could result from the type of contamination in our well?
We are concerned about the chemical contamination found in the water from some residential wells within the site study area. The published scientific literature links exposure for long periods of time to large amounts of several of the chemicals found in the water with liver damage, anesthetic effects, and liver cancer in people or animals. The hazard to public health posed by any environmental contaminant depends upon the amount of the contaminant people are exposed to and the time the exposure lasts. As described in the Toxicological Evaluation section above, the amounts of contaminants detected in the water from those wells have generally not been seen to cause adverse health effects in people or animals in various health studies. The evaluation of cancer risks in this document assumes that there is no exposure to a carcinogen that does not increase the risk of contracting cancer. As described previously, the increased risk of contracting cancer is considered significant in this evaluation if a lifetime exposure is calculated to result in 1 excess cancer case in 1 million people exposed. This threshold is much less than the roughly 1 in 4 to 1 in 3 lifetime cancer rate for the general U.S. population. It is generally very difficult to attribute a case of cancer to a specific exposure to a carcinogen, particularly when the population exposed is small. In addition, the contaminated wells were promptly taken out of service when the contamination was discovered, which would reduce the risk incurred. For more details see the Toxicological Evaluation section.
5. Is our water safe to drink?
In general, groundwater outside the site study area is safe to drink. The only residential wells that have contained contaminants at concentrations considered to be unsafe for consumption have been taken out of service. Some residential wells have contained lead, arsenic, and other metals at concentrations that are above the comparison values ATSDR uses to select contaminants for further evaluation but below EPA's maximum contaminant levels (MCLs) or action levels established for drinking water quality. The MCLs and action levels are generally considered safe for drinking water consumption.
If you are still concerned, contact your local health department to make arrangements to have your water sampled and analyzed.
6. [I am] very concerned about water [and] live by a ditch with contaminated water.
ATSDR and MDCH share your concern about the contaminated water and sediment near your home. We support and encourage the efforts by EPA and MDNR/MDEQ to eliminate the contamination. If you are concerned about the contamination, the first step you should take is to avoid contact with the ditch. There is nothing in the water or sediments that is likely to harm you unless you ingest it or come into direct contact with it. The concentrations of the contaminants in the water and sediments are low enough that only continuous or regular contact over a long time is likely to result in adverse or harmful health effects. To reduce the chance for children coming into contact with the contaminated water and sediment, we are proposing to post warning signs at the access points to the ditch.
The MDCH released a draft of this assessment for public comment on November 6, 1996. The comment period lasted until December 6, 1996. Comments received and MDCH responses are listed in the Responsiveness Summary at the end of the document.