PUBLIC HEALTH ASSESSMENT
BAY CITY MIDDLEGROUNDS
BAY CITY, BAY 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 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 case of cancer in 1 million people exposed or any non-cancer health effects. Comparison values used in this assessment include:
- ATSDR Environmental Media Exposure Guides (EMEGs): Concentrations computed from the
ATSDR Minimum Risk Level (MRL) for chronic exposure of a child, assuming pica behavior for
ATSDR Cancer Risk Evaluation Guides (CREGs): Concentrations calculated so that lifetime adult baseline exposure would result in not more than 1 additional case of cancer per 1 million people exposed(5)
ATSDR Reference Dose Evaluation Guides (RMEGs): Concentrations computed from the U.S. EPA Reference Dose (RfD) for chronic exposure of a child, assuming pica behavior for soil ingestion(6)
U.S. EPA Drinking Water Health Advisories, Lifetime (LTHAs)
U.S. EPA Safe Drinking Water Act Maximum Contaminant Levels (MCLs)
U.S. EPA Safe Drinking Water Act Maximum Contaminant Level Goals (MCLGs)
If no comparison values for a chemical in a medium exist, or there is no CREG available for a carcinogen, the chemical is retained as a contaminant of concern for further evaluation.
To identify chemicals which might contribute to the environmental contamination at the BCM site due to industrial activities in the site area, the MDCH searched the Toxic Chemical Release Inventory (TRI) data base for 1987 through 1993. The U.S. EPA compiles the TRI from information provided by industries. The TRI did not contain any entries for the Bay City Middlegrounds Landfill or that cited the landfill as an off-site disposal facility, because the landfill closed in 1984, three years before the TRI began collecting data. The TRI did contain entries for five facilities with the same postal zip code as the BCM site (48706, covering Middleground Island and Bay City west of the Saginaw River) and three more facilities with postal zip code 48708, covering Bay City east of the Saginaw River.
The Prestolite (now Allied Signal) plant located on the west shore of the Saginaw River across from the BCM site filed TRI reports in 1987, 1988, and 1989, reporting releases of 1,1,1-trichloroethane to the air (1987 and 1988) and to the water of the Saginaw River (1987 only) and transfers to off-site disposal facilities, with no environmental release, of copper (1987-89). A Stackpole/Ultra Carbon facility located on the east shore of the Saginaw River east of the BCM site reported transfers to off-site disposal facilities, with no environmental release, of sodium hydroxide solution in 1987 and 1988. An electroplating company located 1 mile northwest of the BCM site reported transfers to off-site disposal facilities, with no environmental release, of sulfuric acid in 1991 and 1992.
One of the other facilities on the TRI list is located approximately 2 miles northeast of the BCM site and the remaining four are located approximately four miles or more northeast of the site. The releases from these facilities are not likely to contribute to the environmental contamination at the BCM site.
The 1,1,1-trichloroethane released at the Prestolite plant is the only environmental release listed in the TRI that was close enough to the BCM site to have a potential effect at the site. The reported releases were in 1987 and 1988, and the chemical is not likely to remain in the area from those releases, having more likely evaporated and dispersed in the air soon after the releases. Because it was released into the environment around the site in the recent past, 1,1,1-trichloroethane will be retained as a contaminant of concern for further evaluation.
Contaminants of concern for this assessment are listed in Table 2.
A. On-Site Contamination
For this assessment, the site is considered to be the Bay City government-owned property including the former Middlegrounds landfill. This covers the area within the fence line shown in Figure 2, including both phases of the former landfill and the sediment settling basin.
An MDNR contractor installed 13 monitoring wells around the site in 1987, when the landfill was capped, and analysis of water samples collected from the wells documented an extensive pattern of groundwater contamination with volatile organic chemicals, PCBs, and metals (Table 3) (14). In 1988, the MDNR collected more groundwater samples from their monitoring wells at the site which further delineated the pattern found the previous year (also in Table 3) (15).
During the RI in 1989 through 1991, Bay City's contractors collected samples of groundwater from the MDNR monitoring wells and additional wells they installed on the site (Table 3). Bay City's contractors found high concentrations of PCBs in the groundwater, primarily in a relatively small area on the west side of the landfill, in one monitoring well (MW-8, see Figure 2 for location) that was constructed within the landfill and in wells that were constructed near MW-8. A second well drilled into the landfill was dry. Bay City's contractors found a layer of organic solvents in this area, and the extremely high concentrations of organic chemicals, including PCBs, were found in samples from this layer. Contamination has only been found in the shallower aquifer (1, 7).
During Phase III of the RI in September and October 1992, Bay City's contractors collected more samples of groundwater from monitoring wells near MW-8. These samples were filtered before analysis, and contained much lower concentrations of PCBs than in samples from the same wells collected during earlier phases of the RI (also in Table 3). This was attributed to the filtering process used in the Phase III analysis, which would remove particulate matter to which PCBs tend to adsorb (8).
In 1985 and 1988, the MDNR collected and analyzed samples of leachate from the landfill (Table 4) (2, 15). The concentrations of contaminants of concern found in the leachate samples were generally lower than those in the groundwater samples.
Surface Water - Site Ditches
In 1985, the MDNR collected samples of water from each of the ditches adjacent to the landfill. The only contaminant of concern detected in either of the ditch water samples was 535 ppb of manganese (RMEG 50 ppb) in the sample from the south ditch. PCBs were not detected (14).
During Phase II of the RI in 1991, Bay City's contractors collected samples of soil samples from borings on the site, but did not include any surface soil samples. The MDNR ESI of the site in April 1992 did include collection and analysis of samples of surface soil. The ESI results are summarized in Table 5 (3). These surface soil samples included the top 3 to 6 inches of soil, depending on the sample. The concentrations of polycyclic aromatic hydrocarbons (PAHs) found in these samples are comparable to the concentrations typically found in urban surface soils (Reference 16, Table 5-2). The concentrations of various metals, including arsenic, beryllium, cadmium, chromium, cobalt, copper, manganese, nickel, vanadium, and zinc, are above ATSDR comparison values and notably above the concentrations in off-site samples (compare with Table 11). The chromium, copper, lead, manganese, nickel, and zinc concentrations are substantially (more than 1 standard deviation) above the background concentrations in clay soils from the area (17).
During Phase III of the RI in September and October 1992, Bay City's contractors collected four surface soil samples, analyzing them for physical characteristics and standard soil parameters. The analysis did not include any of the contaminants of concern that have been selected for this assessment (8).
In 1991, the MDNR collected and analyzed two samples of surface soil from the sediment dewatering lagoons at the north end of the site, and analyzed the samples for PCBs and pesticides. One sample contained 0.9 ppm of PCBs, the other no detectable PCBs (detection limit 0.55 ppm), and neither sample contained any pesticides (2).
Contractors for Bay City and the MDNR have collected samples of soil from borings on the site during in Phase II of the RI in 1990 and 1991 (7), the ESI in April 1992 (3), and Phase III of the RI in September and October 1992 (8) (Table 6). The analyses found high concentrations of PCBs in the soil, primarily in a relatively small area near MW-8.
During field work for the RI, Bay City's contractors collected samples of air on the site on four days, August 8, August 11, August 17, and August 18, 1989. The air samples collected on August 8 were used to determine background levels because no other field work was being done on the site. The other three days, drilling and sampling were underway on the site. The air samples were collected from locations at the corners of the landfill. The August 8 samples were collected from three of the four corners, the northeast, northwest, and southeast corners. On August 11, Bay City's contractors collected samples from the southwest, northwest, and northeast corners, and from a point "downwind" from a boring near MW-8. The RI report (Reference 1) does not report the wind direction during the sampling periods, other than to say, "Due to interference from the landfill mound, wind direction varied considerably at each distinct monitoring location." Bay City's contractors collected samples from all four corners of the landfill on the other two days. The August 8 samples contained low concentrations of methylene chloride and toluene, when no excavation was in progress on the site, and samples collected on August 11 contained lower concentrations (Table 7) (1). The sample collected downwind of the boring contained the highest concentration on that day. Bay City's contractors found higher concentrations of methylene chloride and toluene, plus ethylbenzene, trichloroethylene, and xylenes in the air samples collected during their excavations on August 17 and 18 (Table 7) (1). On August 18, the concentrations in the samples from the northeast and southwest corners of the landfill were much higher than those in the samples from the other corners. This spatial distribution, with high concentrations on opposite sides of the landfill, is consistent with either an off-site source for the chemicals or a shift in the wind during the 4-hour sampling period. Again, the RI report contained no information on the wind direction during the sampling.
During an attempt to collect samples of gas from the landfill vents on November 10, 1992, the MDNR Air Quality Division (AQD) collected four ambient air samples from the site vicinity, two each upwind and downwind of the site. Each sample was collected for approximately 2 hours. An upwind sample and a downwind sample were collected between 10:00 A.M. and 1:00 P.M., followed by a second pair between 1:00 P.M. and 3:00 P.M. The second downwind sample contained a much higher concentration of methylene chloride than the upwind samples or the first downwind sample did. Other contaminants of concern were also present in that sample at higher concentrations than in the others (Table 8). The AQD did not offer any explanation for the changes in concentrations between the two downwind samples (18).
During Phase III of the RI in October 1992, Bay City's contractors collected 5 samples of soil gas from the BCM site, below the clay cap in the vicinity of MW-8 (Table 9). All five samples contained benzene, chloroform, and 1,1,2-trichloroethane, with the lowest concentrations and fewest chemicals in the sample collected furthest (55 feet south-southeast) from MW-8. The chemicals found in the soil gas were also found in the soil samples from the borings and in the groundwater in the same area. Two of the gas samples were collected relatively close to soil borings dug at the same time. The relative numbers and concentrations of VOCs in the soil samples roughly paralleled the numbers and concentrations of VOCs in the soil gas samples collected in the same areas (8). On several occasions, including in November 1992, the MDNR has attempted to sample the gas from the vents in the cover of the landfill without success. They were not able to collect any gas from the vents (6, 18).
B. Off-Site Contamination
Groundwater Private Wells
In 1988, the MDPH collected water samples from a private well and a cistern located north of the landfill site on Middleground Island. The samples contained no organic chemicals. The samples did contain cadmium and manganese at concentrations above comparison values (Table 10) (19). The MDPH Water Supply Division did not consider these concentrations to be of concern. The cadmium concentration is below the U.S. EPA MCL (5 ppb) and there is no primary MCL for manganese. As mentioned above, this well and cistern were not used for human drinking or other household uses.
Shallow Sub-Surface Soil
During the ESI, the MDNR collected 4 samples of soil from designated background areas near the BCM site, two from a park on the north end of Middleground Island and two from a field across Hotchkiss Street from the southwest corner of the landfill. These samples were collected between 2 and 4 inches beneath the surface and hence are not strictly surface samples. Concentrations of contaminants of concern found in these samples are listed in Table 11 (3). The low concentrations of VOCs listed in the Table were found in one of the samples from the park north of the site. The analysis found low but detectable concentrations of PCBs in both samples from the park. The polycyclic aromatic hydrocarbons (PAHs) concentrations listed in Table 11 were found in one of the samples from the field south of the landfill. The concentrations of PAHs found are comparable to concentrations typically found in urban soils (Reference 16, Table 5-3). The concentrations of metals, except for lead, were generally within the ranges found in background areas in Michigan (17) or the Eastern U.S. (Reference 20, Table 5.1).
Surface water Saginaw River
In 1985, the MDNR collected samples of surface water from the river adjacent to the landfill. None of the contaminants of concern were found in the samples. In 1988, the MDNR collected more surface water samples from the river near the site and some contaminants of concern were found in these samples (Table 12) (15). In August 1989, the MDNR Surface Water Quality Division collected water samples from six sites along the Saginaw River from above Saginaw (approximately 15 miles upstream from the BCM site) to the river mouth and from two locations within Saginaw Bay, and analyzed the samples for PCBs. Two samples were collected from each location, and one was filtered before the analysis so the result would indicate the PCBs dissolved in the water. The other sample was not filtered before analysis to give the total PCBs, including particulate matter suspended in the water (Table 13). The sample collected closest upstream of the BCM site, approximately 7 miles upstream, contained 0.0015 parts per billion (ppb) dissolved PCBs, and 0.0032 ppb total PCBs. The sample collected closest downstream of the BCM site, approximately 2 miles downstream, contained 0.0029 ppb dissolved PCBs and 0.0104 ppb total PCBs. Both dissolved and total PCB concentrations generally increased with distance down the river. The concentrations increased sharply in the vicinity of the BCM site and of a General Motors plant further downstream that has had a history of discharging PCBs to the river. The concentrations in water from Saginaw Bay were similar to those in the river upstream of Saginaw (0.001-0.002 ppb dissolved, 0.004-0.006 ppb total) (21).
During the RI in 1989 through 1991 and the ESI in April 1992, contractors for Bay City and the MDNR collected additional samples of surface water from the river upstream and downstream of the site (also in Table 12) (1, 3). The analyses did not find any PCBs in the samples, though their detection levels (0.1 ppb, 1 ppb) were much higher than the concentrations found in the 1988 sampling.
Sediment Saginaw River
In 1988, the MDNR Surface Water Quality Division collected sediment samples from the Saginaw River, from Saginaw to the mouth, and from Saginaw Bay, and analyzed the samples for PCBs (Table 14, Table 15) (21). They collected samples from borings into the sediment at selected locations downstream from Middleground Island, and the PCB concentrations were generally higher in the subsurface samples than in shallower ones (Table 15). The deepest samples often contained very low concentrations of PCBs. This pattern of distribution with depth reflects the history of PCB use, with the deepest layers deposited before PCBs came into wide use and the shallowest layers after the chemicals were banned. The PCB concentrations in surface sediments from the river generally increase with distance downstream, though the bay sediments have much lower concentrations from mixing with sediments from other sources.
The highest concentration from the west channel was collected immediately downstream from the BCM site. The highest concentration from the east channel was collected near a cooling water outlet from the Prestolite facility. That sample also contained an unusual composition of PCBs. A subset of the family of PCBs that provided between 2 and 9% of the total PCBs in the other samples (averaging 4%), provided 75% of the total PCBs in this sample. The other PCB subset compositions reported in this sample were in the same proportions as those in the other samples.
During the RI in 1989 through 1991, Bay City's contractors collected samples of sediment from the river adjacent to the site. The MDNR ESI of the site in April 1992 included collection and analysis of more samples of sediment from the river. Most contaminants of concern were found at higher concentrations in samples collected downstream of the site than in those collected upstream (Table 16) (1, 3).
Saginaw River fish
In June 1986, the MDNR collected 9 walleye (16 to 22 inches long) and 15 carp (18 to 30 inches long) from the Saginaw River approximately 3 miles downstream from the BCM site. Six of the walleye were combined into two composite samples of three fish each, using the entire fish. The remaining three walleye were filleted, the skin left on, and samples of each fish were analyzed separately. Ten of the carp were combined into two composite samples of five fish each, taking the entire fish. The remaining five carp were filleted, the skin removed, and samples of each fish were analyzed separately. All samples were analyzed for metals and PCBs (Table 17) (22). In July 1992, the MDNR collected 10 carp (18 to 30 inches long) from the river at Crow Island, approximately 8 miles upstream from the site. These fish were filleted, the skin removed, and a sample from each fish was analyzed for mercury, PCBs, and pesticides (also in Table 17) (24). All of the 1986 carp samples, whole fish or edible-portion fillets, exceeded the U.S. FDA Action Level of 2 ppm PCBs. Eight of the 10 carp collected in 1992 exceeded 2 ppm PCBs, and one also exceeded the U.S. FDA Action Level for chlordane. The PCB concentrations in the carp fillets from the two collections were similar. Both whole-fish composite walleye samples from 1986 exceeded 2 ppm PCBs, but none of the edible-portion fillets collected that same year did. The contamination in these fish cannot be attributed solely to the BCM site. There are many other sources that have contributed PCBs to the Saginaw River watershed. Although the Crow Island collection site is upstream of the site, walleye and carp are both species which migrate widely within the water system.
C. Quality Assurance and Quality Control
In preparing this Health Assessment, the MDCH 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 Health Assessment is determined by the reliability of the referenced information.
D. Physical and Other Hazards
The BCM site poses the same physical hazards that can be found at any location of similar terrain. The mound and the settling pond both have steep banks, where trespassers might fall. There are also reports of trash exposed on the older part of the landfill north of the mound, which was not covered by the cap (2). The trash may make walking difficult or present sharp or jagged edges that might injure a trespasser who steps or falls on them.
All old landfills pose the potential hazard of methane gas generated in anaerobic decomposition of organic material. Under certain conditions, methane generated in a landfill can migrate through the soil to neighboring subsurface structures such as basements, where the gas might accumulate to flammable or explosive concentrations. The final cap over the BCM landfill contained vents to release to the atmosphere any gas that might be generated. However, attempts to sample the gas from the vents found that no gas was reaching the vents, possibly due to improper vent design and location. Air monitoring for worker health and safety during drilling operations in the landfill did detect methane gas (2).
Lateral migration of gas from a landfill is most likely when the landfill contents are in contact with a porous layer of soil under a non-porous layer of soil. The geology of the island features a layer of clay over a layer of sand, and the pits and trenches of the first, in-ground phase of the landfill cut through the clay into the sand layer, reaching below the water table. It is not clear from the information available whether the pits and trenches were lined with clay to prevent the waste from coming into contact with the sand layer and the aquifer. It is also not recorded in the available information how far the clay layer over the sand extends. Because of the shallow water table, houses on the island are not likely to have basements. One island resident told Bay City's RI contractors that his or her house, approximately 0.5 miles south of the landfill, had a basement in the past, but the basement had been filled with sand after a flood (1).
To determine whether nearby residents are exposed to contaminants migrating from the site, ATSDR evaluates the environmental and human components that could 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.
A. Completed Exposure Pathways
Surface soil, direct contact
The surface soils on the site are contaminated with metals, pesticides, polynuclear aromatic hydrocarbons (PAHs), and other semi-volatile organic chemicals (Table 5). Site subsurface material is contaminated with these substances and PCBs (Table 6) and future erosion or excavation might expose the subsurface material for direct contact. In addition, a large area of the landfill was never covered, and waste and trash is on the surface in the north end of the landfill. The site is fenced on three sides. The side of the site along the west channel of the river is not fenced at all and it is possible for someone to walk around the ends of the fence. A group of PRPs for the site is planning to install a fence along the river side of the site in the Summer of 1996 (5). Snowmobile tracks were seen on the site during a February 10, 1994, site visit. MDEQ staff have reported seeing hunters on the site and children using the various slopes in the site for sledding in the winter, having bypassed the existing fence (2). Access to the site around the existing fence would be easier in the winter, when the Saginaw River freezes and provides a wider pathway around the ends of the fence. On the other hand, snow cover during the winter would provide a barrier between the contaminated soil and waste and any trespassers.
Surface soil, fugitive dust
Contaminated surface soil in areas without vegetative cover might be lifted by the wind, particularly in dry seasons, and be transported off the site as fugitive dust. People living downwind of the site might inhale the contaminated dust or after it settles, come into dermal contact with it or incidentally ingest it. There isn't enough information available on surface contamination or airborne dust near the site to fully evaluate the potential hazard. According to the ESI, the site is well-vegetated, though there are some barren, eroded areas. North of the mound marking the bermed landfill, the trenched landfill was not covered and trash and waste is visible on the surface (2).
It is not clear how large a receptor population there might be for this pathway. The prevailing winds in the area are from the west or southwest, though wind might come from any direction. As mentioned in the Demographics, Land Use, and Natural Resource Use section above, there are 34 houses on the south end of the island, including two along Hotchkiss Street, facing the south end of the site. The closest residences east of the site (downwind by the prevailing winds) are on the east shore of the Saginaw River beyond a marina and other commercial enterprises along the river bank. On Middleground Island, across Evergreen Road east of the landfill are commercial properties, including a marina, boat storage, and a now-closed restaurant. Further development in this area has been proposed and State and federal environmental agencies issued a wetlands/floodplains permit on September 8, 1995 (4). The north end of the island includes several ball fields, the Bay City Boys and Girls Club, and a rowing club. The west shore of the river is undeveloped near the island, except for the Prestolite factory (now owned by Allied Signal) across from the north end of the landfill.
There are reports of leachate seeping out of the landfill and flowing into the ditches along the landfill's perimeter. As seen in Table 4, chemicals have been found in the leachate at concentrations potentially of health concern. People on the site could come into contact with the leachate either on the landfill surface or in the ditches. Children living on the island may be playing in the ditches around the landfill, and their parents have asked the MDEQ whether it is safe for their children to do so.
Saginaw River sediment and surface water
Site material contaminated with metals, PCBs, pesticides, polynuclear aromatic hydrocarbons (PAHs), and other semi-volatile organic chemicals has been transported by groundwater discharge, leachate seepage, and surface erosion into the adjacent Saginaw River. River sediments at the site are contaminated with these chemicals (Table 16), though the RI and ESI found no significant difference in the chemistry of the water between upstream and downstream of the site (Table 12). The RI and ESI did not detect PCBs in the water, though an MDNR study with lower detection limits at the same time as the RI found PCB concentrations in the water increased downstream of the site compared to upstream (also in Table 12). PCBs have been found in the sediment adjacent to the site, with MDNR studies before the RI indicating an increase in concentrations downstream of the BCM site (Table 14, Table 15). It is difficult to establish how likely sustained human exposure to the contaminated sediments would be. MDEQ staff report that people fish, waterski, jetski, and swim in the west channel (2, 6). The Bay City Rowing Club is located on the west side of the north end of the island, approximately 0.5 miles north of the site.
The Bay City and Bay County public water supplies share an intake on Saginaw Bay in Lake Huron, approximately 15 miles north of the BCM site. The Saginaw River empties into Saginaw Bay, and the currents in the bay may carry water from the river to the intake. Samples of surface water collected from Saginaw Bay in 1989 contained PCBs at total concentrations (combined dissolved and particulate) in excess of the ATSDR CREG. Routine sampling of the city and county water by MDPH/MDEQ(7) has not detected any contamination (25). The concentration of dissolved PCBs in water from the bay did not exceed the CREG, and filtering during treatment of the municipal water supply should remove any particulate PCBs, reducing the potential exposure.
Biota in the river might absorb PCBs from the water and sediment, and the chemicals can be passed up the food chain as one species consumes another. The best documented pathway for human exposure to PCBs in the biota is through fish, which we discuss in the next section. Other animals, including mammals, birds, reptiles, and amphibia, can also be adversely affected by PCBs in the environment. There is no information available on PCB contamination of these other animals in the area of the BCM landfill nor on the consumption rates of these animals by the area residents.
Saginaw River fish
Some fish collected from Saginaw River contained concentrations of PCBs and dioxins at levels potentially of human health concern. The MDCH maintains an advisory recommending that no one eat large quantities of fish of any species taken from the Saginaw River, and that no one consume any carp or catfish from the river, because of contamination with PCBs and dioxins (26). There are many other sources for PCBs in the watershed of the Saginaw River besides the BCM site. The sediment in the river serves as a reservoir for PCBs from historic discharges, and fish might continue to take up PCBs from the sediments for decades after the discharges have ceased. Many species of fish tend to migrate over a range of area, making it difficult to isolate a specific source's contribution to the contaminant load in the fish. There is an active sport fishery on the river. Many anglers eat their catch, and so do friends and families of anglers. Their consumption patterns may violate the MDCH fish consumption advisories. The advisories are not compulsory, and there is no enforcement mechanism in place.
B. Potential Exposure Pathways
The groundwater in the shallowest aquifer at the site is contaminated with metals, PCBs, pesticides, polynuclear aromatic hydrocarbons (PAHs), and other semi-volatile organic chemicals. Use of this water for household consumption could result in exposure to the chemicals potentially of public health concern. The extremely high concentrations of certain organic chemicals listed in Table 3 were found in samples collected from wells drilled into the west side of the landfill itself during the RI. The water in these wells contained sufficient organic chemicals to form separate layers floating on and at the bottom of the water.
Water in the shallow aquifer tends to flow outward in all directions from the landfill. The aquifer connects directly to the Saginaw River. The groundwater in the area of the highest contaminant concentrations flows to the west, and discharges into the river. Any contamination of the shallow aquifer originating on the island would discharge to the river and would not likely affect the groundwater on the mainland beyond the river. See above under Saginaw River sediment and surface water and Saginaw River fish for further discussion of these pathways.
As mentioned in the Demographics, Land Use, and Natural Resource Use section above, during Phase I of the RI in 1989, Bay City's contractors carried out a door-to-door survey on Middleground Island, asking about private wells. All residents interviewed reported that their homes were served by the Bay County public water system (whose source is in Lake Huron, 15 miles north of the site, and which has been available on the island since the 1960s ), and there had never been wells on the island that were dedicated to human consumption use. Two wells were located on the island at the time of the survey, one at a residence north of the site that was only used for summer watering of domestic animals and one at a restaurant east of the landfill that was not in use at that time (1). The residence has since been demolished (4).
The domestic animals who drank water from the private well north of the site might have accumulated contaminants from the water. If the animals or their products were then consumed by people, the consumers might thereby have been exposed to the contaminants. There is no information available on what species of animals were kept at the residence with the well. The residence has been demolished (4). There is not space on the island for a commercial animal-raising operation, but a family might raise a few animals and use them to supplement their diets.
The mainland area off the island north (downgradient) of the site, within the Bay City City Limits, is also served by Bay City municipal water, whose primary intake is in Saginaw Bay on Lake Huron, approximately 15 miles north of the site (27). The Phase 1 RI report includes well logs for approximately 60 domestic wells within a 3-mile radius of the site. Most of these wells were located southeast of the site, south of Bay City. The nearest well listed was 1 mile south of the site, on the west side of the Saginaw River (1). The ESI Report includes an additional 37 well logs from the area, mainly northwest of Bay City. The nearest wells to the site in the ESI list were a cluster of monitoring wells on an industrial property on the west bank of the Saginaw River, across the west channel from the north end of the BCM site. The next nearest wells listed that were downgradient from the site were industrial wells on the north side of the city, at least 3 miles from the site on the west shore of the river (3). There is no indication that any of the site investigations have included a door-to-door survey on the mainland proximate to the site to locate private wells that were not included in the compilations of well logs. As mentioned above, groundwater contamination in the shallow aquifer on Middleground Island would most likely discharge to the Saginaw River and would not likely reach mainland wells. There is no evidence available that contamination from the BCM site has affected deeper aquifers.
Traces of several volatile organic chemicals were detected in the air at the site, both before and during investigative work for the RI (Table 7, Table 8). Methylene chloride was detected under background conditions and in upwind samples at concentrations of human health concern for long-term exposure. The detected concentrations of other chemicals were generally not of health concern for short-term exposure, even those detected when drilling and sampling were being done. However, under some circumstances, residents in the houses south of the site might be exposed to gases from the landfill for long periods, because of their proximity. Extensive excavation during remediation of the landfill may liberate higher concentrations of these volatile organic chemicals, therefore appropriate precautions to minimize these releases should be considered in the design of the site remediation. The existing landfill cap has vents installed to liberate gases that might be generated in the waste, however, several attempts to collect samples of gas from these vents have not been successful, so there is no information available on what gases are generated in the landfill and escaping to the environment (6).
Under certain conditions, volatile contaminants either generated by decomposing wastes or volatilizing from the waste in a landfill can migrate through the soil to neighboring basements, where the gas might accumulate to harmful, flammable, or explosive concentrations. As seen in Table 9, soil gas extracted from within the landfill contained volatile organic chemicals, including benzene, chloroform, 1,2-dichloroethane, 1,1-dichloroethylene, and 1,1,2-trichloroethane, at concentrations of health concern for chronic exposure.
The final cap over the BCM landfill contained vents to release any gas that might be generated into the atmosphere. However, attempts to sample the gas from the vents have not succeeded, so there is no information available on what gases are generated in the landfill and escaping to the environment (6). Lateral migration of gas from a landfill is most likely when the landfill contents are in contact with a porous layer of soil under a non-porous layer of soil. The geology of the island features a layer of clay over a layer of sand, and the pits and trenches of the first, in-ground phase of the landfill cut through the clay into the sand layer, reaching below the water table. It is not clear from the information available whether the pits and trenches were lined with clay to prevent the waste from coming into contact with the sand layer and the aquifer. It is also not recorded in the available information how far the clay layer over the sand extends. Because of the shallow water table, houses on the island are not likely to have basements, though a survey to identify houses with basements on the island has not been completed (4). One island resident told Bay City's RI contractors that his or her house, approximately 0.5 miles south of the landfill, had a basement in the past, but the basement had been filled with sand after a flood (1).
A. Toxicological Evaluation
The primary benchmarks against which exposures are evaluated for their potential for causing non-cancer adverse health effects are the Minimal Risk Levels (MRLs), developed by ATSDR, and Reference Doses (RfDs) and Reference Concentrations (RfCs), developed by the U.S. 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 derivation of MRLs, RfDs, and RfCs from the observed threshold exposures includes safety factors 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 which may cause cancer, the risk associated with an exposure is evaluated separately from non-cancer 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 (20): 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.
The completed pathways of exposure to contaminants on the site are direct contact with contaminated surface soil during trespass, air transport of vapors and contaminated fugitive dust, consumption of PCB-contaminated fish from the Saginaw River, and contact with the water and sediment of the site perimeter ditches and the Saginaw River. The PCBs in the fish arise from many sources in the river watershed, including the BCM site.
Although access to the BCM site is not fully restricted, the fence along the land sides does discourage trespass. The people who come into contact with surface materials on the site are most likely to be older children to young adults, and access to the site will be infrequent. Children of the age subject to pica behavior are not likely to be on the site itself. As appropriate, pica children will be considered as a possible population that might be exposed to soils near the site.
There are two kinds, or isomers, of 1,2-dichloroethylene, referred to as cis-1,2-dichloroethylene and trans-1,2-dichloroethylene, which have slightly different properties and toxicity. The chemical analysis in the published studies of the site area did not distinguish between the two isomers. No one is likely to ingest enough 1,2-dichloroethylene from the soil near the site to exceed published RfDs, MRLs, or the doses at which adverse health effects have been observed in human studies or experimental animals for exposure to either isomer of 1,2-dichloroethylene. There is no evidence linking exposure to 1,2-dichloroethylene with cancer (28).
1,1,1-Trichloroethane was not detected in any surface soil, air, water, or sediment sample collected on or near the site. The chemical was found in subsurface soil near the site, which might be exposed during future excavation. Should this occur, no one is likely to ingest enough of the chemical to incur an exposure dose equal to those at which adverse health effects have been seen in humans or laboratory animals. There are no MRLs or RfDs available for ingestion of 1,1,1-trichloroethane. There is no evidence available linking exposure to 1,1,1-trichloroethane with cancer (29).
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment, as products of incomplete combustion of hydrocarbons, cellulose, and other organic materials. The concentrations of PAHs found in surface soil samples collected on and near the site are comparable to the concentrations typically found in urban surface soils (Reference 16, Table 5-2). Adverse health effects attributable to the PAHs on and near the site are not likely to occur at a rate that would be noticeable against the normal incidence.
No one is likely to incidentally ingest enough gamma-BHC (also called gamma-hexachlorocyclohexane or lindane) from the surface soil on the site to exceed the RfD for non-cancer adverse health effects. The U.S. EPA has classified gamma-BHC as a probable human carcinogen (U.S. EPA Class B2), because laboratory mice whose feed contained the chemical developed liver cancer. There is no data available on cancer rates in humans exposed to gamma-BHC. As noted in the footnotes to Table 5, there is no officially accepted cancer potency factor for gamma-BHC. From a potency factor for gamma-BHC calculated from the experimental results in mice cited above, and published potency factors for other isomers of BHC and the commercial mixture of isomers, it is not likely that anyone coming into contact with the soil on the site would suffer any significant increased risk of cancer from the gamma-BHC present (30).
If the shallow-subsurface soil in the park north of the site were exposed, a pica child might ingest enough PCBs from the soil to exceed the MRL for non-cancer adverse health effects. However, the child would not be likely to exceed the levels at which adverse health effects were observed in laboratory animals. The U.S. EPA has classified PCBs as probable human carcinogens (U.S. EPA Class B2) because some laboratory animals whose food contained PCBs developed liver cancer (31). No one is likely to incur any significant increased risk of cancer from exposure to the PCBs in the soil near the site. People living near other sites of PCB-contaminated soil in Michigan have not been found to have elevated concentrations of PCBs in their bodies, even where the concentrations in the soil are several orders of magnitude higher than those found near the BCM site. The PCB concentrations in Saginaw River sediment at the site would not be considered to pose a health threat from direct contact even if the sediments were on shore where contact might be much more frequent.(8) An adult would have to drink 0.75 liters of water a day from the Saginaw River for his lifetime to incur any significant increased cancer risk from the PCBs in the water. There are no drinking water intakes on the River downstream from Saginaw. The PCB concentrations in the water of Saginaw Bay would not likely pose any apparent significant increased risk of contracting cancer to anyone who consumes the water.
There are no MRLs or RfD currently available for ingestion exposure to 1,4-dichlorobenzene. No one is likely to ingest enough 1,4-dichlorobenzene from the surface soil on the site to exceed the doses at which adverse health effects were seen in laboratory animals. The U.S. Department of Health and Human Services National Toxicology Program has classified 1,4-dichlorobenzene as "Reasonably Anticipated to be a Carcinogen" because some laboratory rats and mice whose food contained the chemical developed kidney and liver cancers. From the highest potency factor found in these experiments, no one is likely to incur any significant increased risk of cancer from the 1,4-dichlorobenzene in the soils on the site (32).
The U.S. EPA has withdrawn the RfD for 4-methylphenol, pending further review. No one would be likely to consume enough 4-methylphenol from the soil on the site to exceed the RfD that has been withdrawn, an acute-exposure MRL, or any of the doses at which adverse non-cancer health effects have been observed. The U.S. EPA has classified 4-methylphenol as a possible human carcinogen (U.S. EPA Class C) because some laboratory mice experienced an increased incidence of skin cancer when 4-methylphenol and another carcinogen were applied to their skin. The 4-methylphenol increased the incidence over the rate with the carcinogen alone. There is not enough information available to evaluate the risk of developing cancer from exposure to the 4-methylphenol in the soils at the site (33).
Data is lacking on possible health effects from exposure to carbazole, dibenzofuran, or 1,3-dichlorobenzene (33). The very low concentrations of these chemicals found in the surface and shallow subsurface soil on and near the site should pose no threat of adverse health effects.
A child subject to pica behavior might ingest enough arsenic, barium, manganese or vanadium from the soil near the site to exceed the MRLs or RfDs for non-cancer health effects.(9) A child subject to pica behavior might ingest enough cadmium or zinc from the soil on the site to exceed the MRL for non-cancer health effects, but children of the age subject to pica behavior are not likely to be on the site. The pica child would not be likely to exceed the doses of these metals at which adverse health effects have been observed. No one is likely to incidentally ingest enough of these metals, beryllium, or nickel from the soil on or near the site to exceed the MRLs or RfDs (34, 35, 36, 37, 38, 39, 40, 41, 42). The concentrations of these metals were generally within the ranges found in background areas in Michigan (17) or the Eastern U.S. (Reference 20, Table 5.1). No health effects from exposure to these metals in the soil in areas near the site are likely to occur above background rates.
Lead is a cumulative poison, and exposure can result in neurological damage and developmental difficulties. Experimental animals who were fed lead compounds in their diet developed cancer, though there is no evidence linking exposure to lead with cancer in humans. Although the U.S. EPA has classified lead as a probable human carcinogen (Class B2), there is not sufficient information available to estimate the cancer risk from exposure to lead. Neither the U.S. EPA or ATSDR has issued a RfD or MRL for non-cancer adverse health effects from ingestion of lead or lead compounds. The concentrations of lead found in the surface soil on the site (Table 5) and shallow subsurface soil near the site (Table 11) are comparable to those commonly found in urban soils (43). They are less 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 201, as amended).
The only chemical present in the ambient air when no excavation was going on at the site at concentrations above comparison values was methylene chloride. The concentration exceeded the CREG and an MRL for intermediate-term exposure for non-cancer adverse health effects. The concentration did not exceed the levels at which adverse non-cancer health effects have been observed. The U.S. EPA has classified methylene chloride as a probable human carcinogen (U.S. Class B2), because laboratory mice who breathed the chemical developed liver and lung cancer. There is no evidence linking exposure to methylene chloride with cancer in workers using the chemical (44). The concentrations of methylene chloride in the background air at the BCM site might pose a low increased risk of cancer to nearby residents on lifetime exposure.
The concentrations of other chemicals detected in the ambient air at the site do not exceed the available MRLs, RfCs, or levels at which adverse non-cancer health effects have been observed. The concentrations also did not exceed the background ranges found in urban areas (32, 45, 46, 47, 48, 49, 50, 51, 52, 53). Exposure to these concentrations is not likely to result in a greater rate of adverse health effects than normally occurs.
Trichloroethylene and xylenes and increased concentrations of methylene chloride were detected in the air at the site perimeter at concentrations above comparison values during boring and sampling operations on the site. None of the concentrations approached the MRLs for acute- or intermediate-term exposure for non-cancer adverse health effects. The trichloroethylene and methylene chloride concentrations exceeded the CREGs, but the duration of any exposure is not clear (44, 45, 54). The erratic pattern of detection, in the absence of information on wind direction, does not exclude the possibility that these chemicals in the air on the site may have come from an off-site source. Any further remedial work on the site should include all appropriate precautions to minimize the escape and transport of volatile chemicals from the site.
Anyone whose water supply contains the concentration of manganese found in the water from the private well on the island north of the landfill might ingest enough of the metal to exceed the RfD for drinking water.(10) A child who drank the water might ingest enough manganese to attain the dose at which chronic, long-term exposure has resulted in mild neurological changes (34, 35). However, as mentioned above, the well was not used as a primary household water supply, and it is not likely that anyone would have drunk enough water from that well to experience any adverse health effects from the manganese. The residence the well served has since been demolished (4).
Manganese does bioaccumulate in algae, plankton, and some fish, but mammals tend to maintain a constant level of manganese in their bodies (34). Therefore, it is not likely that animals drinking water from the private well north of the site would have accumulated manganese in their bodies and consumption of the animals or their products would not likely have posed any increased health risk from exposure to manganese.
No one whose drinking water supply contains the amount of cadmium found in the water from the private well north of the site is likely to ingest enough of the metal to exceed the MRL for non-cancer adverse health effects. It is not possible to evaluate the risk of cancer from drinking the water due to its cadmium content (36). Again, the well was not used as a household water supply, and the residence it served has been demolished (4).
Cadmium is known to bioaccumulate, primarily in the liver and kidneys in vertebrates. An animal drinking the water from the private well north of the site might have accumulated enough cadmium in its liver and kidneys that a person who consumes those organs might have exceeded the MRL for non-cancer adverse health effects from exposure to the metal. However, this level of exposure was not very likely. Though cadmium is excreted from the body very slowly, only a small fraction of the metal that is ingested is absorbed through the intestines. The cadmium burden in the animal's body would increase very slowly, and would not be likely to attain hazardous levels in the short lifetime of most animals raised for food. The animal's kidneys would be impaired by cadmium poisoning at metal concentrations in the organ well below the concentrations that would cause harm to humans eating the kidney at typical American consumption rates (36). Organ meats such as liver and kidneys are not a major component of the most common American diet, with consumption averaging 2 grams per day (equivalent to one 0.5-pound [225 g] meal every 4 months) (Reference 20, Appendix E), however, dietary habits vary widely among subcultures within the larger society. The residence served by the well has been vacated and demolished (4).
Water in ditches and leachate
The only contaminant of concern detected in the one sampling on record of water from the on-site ditches (in 1985) was manganese. It is not likely that anyone would ingest enough water from the ditch, either deliberately or incidentally, to incur a dose of manganese in excess of the RfD for non-cancer adverse health effects through drinking water.(11) It is extremely unlikely that anyone would ingest enough manganese from the water in the ditch to equal the LOAEL. Leachate from the site has contained benzene, 1,4-dichlorobenzene, chromium, nickel, and zinc at concentrations above comparison values. The leachate would have to provide a major fraction of a person's drinking water, ten per cent or more, for the person to risk any adverse non-cancer health effects or a significant increased risk of contracting cancer. This is not likely to occur.
PCBs in Fish
A U.S. Department of Agriculture food consumption survey established that the average American consumes an average of 12 grams of fish and shellfish a day, or a serving of 0.5 pounds (225 grams) of fish approximately every 3 weeks (Reference 20, Appendix E). Surveys of sport anglers and their families in Michigan have found that they eat fish much more often, averaging about one meal every nine days, an average consumption rate of 26.5 grams of fish per day (about 2/3 of this, 16.7 grams/day, is sport-caught fish) (55). Using the latter consumption rate, a person who consumes carp from the Saginaw River near the BCM site might ingest enough PCBs to exceed the dose at which adverse health effects were seen in experiments with laboratory animals (suppression of an immune response in monkeys). The PCB concentration in walleye taken from the Saginaw River downstream from the site was enough that a consumer might exceed the MRL, though the dose is not likely to exceed the levels at which adverse non-cancer health effects have been observed in epidemiologic or laboratory animal studies. The U.S. EPA has classified PCBs as probable human carcinogens (U.S. EPA Class B2), because some laboratory animals whose feed contained the chemicals developed liver cancer. Studies of cancer rates in humans whose food contained PCBs have been inconclusive. Based on the cancer rates seen in animal studies, regular consumption of carp from the Saginaw River could result in a high increased risk of contracting cancer and regular consumption of walleye from the river could result in a moderate increased risk of contracting cancer (31).
A person who consumes carp from the river might ingest enough chlordane to exceed the RfD for non-cancer adverse health effects, though not enough to attain the MRLs or the doses at which adverse health effects have been observed. There is no evidence available that links ingestion of chlordane to cancer in humans, but some experimental animals whose food contained chlordane have developed liver cancer. The U.S. EPA has classified chlordane as a probable human carcinogen (U.S. EPA Class B2) (56). Lifetime consumption of carp from the river could result in a low increased risk of contracting cancer from the chlordane in the fish.
The MDCH has issued an advisory that people restrict their consumption of fish of any species taken from the Saginaw or Tittabawassee Rivers, and that they should not consume any carp or catfish taken from either river, due to contamination with PCBs and dioxins(12) (26). There are many other sources for PCBs in the watershed of the Saginaw River besides this site. Many species of fish tend to migrate over a range of area, making it difficult to isolate a specific source's contribution to the contaminant load in the fish.
Saginaw River water and sediment
The most probable human exposure to contaminants in the water and sediment of the Saginaw River near the BCM site is during recreation, including swimming, boating, and fishing. People using the river for recreation will be exposed to the water and sediment through dermal contact and incidental ingestion. Exposure through these routes is likely to only occur occasionally and absorption of PCBs from soils or sediment through the skin is very slight. The PCB concentrations in Saginaw River sediment at the site would not be considered to pose a health threat from direct contact even if the sediments were on shore, where contact might be much more frequent.(13) A person using the river for recreation is not likely to drink enough water from the Saginaw River to incur any significant increased cancer risk from the PCBs in the water. The concentrations of PAHs found in sediment samples collected from the river near the site are comparable to the concentrations typically found in urban surface soils (Reference 16, Table 5-2). Metals concentrations in the water and sediments are within background ranges. There is not likely to be any significant health impact from recreational use of the river other than those described above from consumption of sport-caught fish.
B. Health Outcome Data Evaluation
Trespassers on the site have been exposed to chemical contaminants, but the exposure is not likely to have been extensive enough to result in adverse health effects. A resident of Bay City has expressed concern about the incidence of cancer in his community. The MDCH Division of Health Risk Assessment has obtained cancer incidence data for the area from the MDCH Office of the State Registrar and Division of Health Statistics.
MDCH-published statistics for 1990-1992 show no statistically significant difference in cancer incidence or mortality between Bay County and Michigan as a whole (Table 18) (57). Cancer incidence statistics for the Zip Code area including the site and Bay City west of the Saginaw River (48706) and that including Bay City east of the Saginaw River (48708) for 1990 through 1993 show a slight, statistically significant (at a probability level of 5 percent) elevation in incidence and rate for the entire period 1990-1993 in Zip Code 48706, though the elevations in incidence and rate were not statistically significant in individual years. None of the incidences and rates for Zip Code 48708 were statistically significantly increased (Table 19) (58).
C. Community Health Concerns Evaluation
When residents of the island inquired whether it was safe for their children to play in the ditches around the landfill, MDNR personnel responded that the children should not do so, and referred the residents to the local and state health departments if they had further questions (13). MDCH concurs with the recommendation that the children not play in the ditches. Although, as mentioned in the Toxicological Evaluation section above, the recorded contaminants in the ditches and leachate are not present at concentrations of urgent human health hazard, these chemicals and others are present in much higher concentrations elsewhere on the site. It is prudent to reduce one's potential for contact with hazardous chemicals as far as is possible. The MDNR did not record the names or addresses of the inquiring residents.
At the public meeting on September 8, 1994, John Filpus of the MDPH responded to the expressed concern about their city water supply by saying that MDPH regularly samples and tests water from all public water supplies. Municipal water systems are required to perform remedial actions to reduce any contamination in the finished water going to the system to levels below the U.S. EPA MCLs. There has been no contamination found in MDPH/MDEQ monitoring of the Bay City or Bay County public water supplies(14) (25). The MDNR did find PCBs in water samples collected from Saginaw Bay in 1989, though not at concentrations of human health concern for treated water (21).
MDCH responses to health-related concerns and questions about the site received from the public during the public comment periods for the draft health assessment follow.
1. Soil and water contamination on surrounding property.
Based on limited evidence, there is no evidence of significant soil and water contamination on property surrounding the site. Samples of soil were collected from two areas near the site to provide information on background concentrations. One of these samples did contain PCBs, but at a concentration that is not uncommon in urban areas and below the U.S. EPA recommended clean-up level for residential properties. If you are concerned about contamination on your property, please discuss the situation with the MDEQ, U.S. EPA, or MDCH.
MDCH staff contacted one of the citizens who made this comment, and assured him that, as far as is known, the contamination is limited to the landfill area. The citizen was specifically concerned about foodstuff from a garden next to the landfill. MDCH staff assured him that there should not be any problem. The foodstuffs should be well washed, though, as a precaution.
2. Are there any health hazards from living in the area of the landfill? I am concerned about radioactive contaminants, airborne contaminants, and any substances that may be surfacing that are harmful to health. Will traveling to and from my home on the Middlegrounds and passing the dump site daily put me and my family at an increased health risk? If so, what risks? (A consolidation of comments from several residents of the south end of Middleground Island.)
There are few health hazards from living near the landfill. As described above, surface soil on the landfill cap does contain slightly elevated concentrations of various contaminants, but transfer by fugitive dust from the landfill to neighboring areas is not likely to occur to the point where the soil on the neighboring areas will pose a health hazard. When the landfill is not being disturbed by excavation or borings, the concentrations of volatile organic chemicals in the air are generally within the range found in urban areas. There is no record of radioactive material being disposed of in the landfill, though no survey for radioactivity has been done. There are few records of what was disposed of in the landfill, so no one knows what might surface in the uncovered northern parts of the trenches. That is a matter that the MDEQ, U.S. EPA, and MDCH will continue to monitor and respond appropriately to.
3. Does swimming and boating in the waters of the Saginaw River near the Middlegrounds increase my (our) risk of health problems? If so, how?
People swimming and boating in any body of water come into dermal contact with the water and sediments and will incidentally ingest small quantities of the water and sediments. If the water or sediments contain chemical contaminants, as in the Saginaw River around Middleground Island, people recreating on and in the water body will be exposed to some degree to the contaminants. As described above in the Toxicological Evaluation section, the amounts of contaminants that people are likely to be exposed to during recreation on the river are not likely to result in adverse health effects.
4. Should we be buying bottled water? Could our drinking water be contaminated?
All residences on the island (including the commentor's) are connected to the Bay County public water supply. The County public water supply, taken from Lake Huron 15 miles north of Middleground Island, is regularly monitored by the MDEQ, and no contamination has ever been detected in the water supply. There is no need based on contamination to buy bottled water at this time.
5. I wish that you would let people know that there are no proven PCB-related health risks instead of scaring everyone unnecessarily.
Evaluation of the health risks from exposure to PCBs is extremely difficult. The only adverse health effect in humans that has definitely been shown to be caused by exposure to PCBs is chloracne, from occupational exposure to commercial PCB formulations (31). People in Japan and Taiwan who inadvertently consumed rice oil contaminated with PCBs, chlorinated dibenzofurans (CDFs), and other chemicals developed severe acne, anemia, bronchitis, transient liver changes, and other adverse health effects, though these effects are primarily attributed to the CDFs (59). There have also been studies that link maternal consumption of PCB-contaminated fish to developmental problems in their children, though there are problems with the studies that cast doubt on their conclusions. A range of other adverse health effects, including liver cancer and developmental problems, have been seen in laboratory animals exposed to PCBs (31). We admit that there is uncertainty in extrapolating from results in laboratory animals to safe levels for human exposure. The standard methods used for this extrapolation are conservative, and following the methods minimizes the threat to public health.
6. (From a resident of Middleground Island): It is rumored that there is a high incidence of cancer in families that have lived on Evergreen [Road, on Middleground Island] for a long time. (From a Bay City resident, not living on Middleground Island): We here in Bay City have a very high cancer rate. Four of my peers (age 50s) are presently struggling with cancer. Two others are already deceased. Some doctors are now saying it's the environment.
We at MDCH understand your concern about the incidence of cancer you perceive in your community. However, cancer is more prevalent than most people realize. One out of three people will develop cancer in their lifetime. Mutations as a result of aging are a major factor in cancer, and therefore the more advanced age we achieve the more likely we are to develop cancer. Most causes of cancer are as yet unknown, but any link between the environment and cancer is very weak, and is disputed within the scientific community. MDCH has a policy to investigate perceived increases of cancer incidence in areas of Michigan. Please contact the MDCH to discuss your concerns in greater depth. Information on cancer, its known causes, and ways to reduce your likelihood of contracting cancer is also available through your local chapter of the American Cancer Society.
The MDCH Division of Health Risk Assessment has obtained cancer incidence data for the Bay City area from the MDCH Office of the State Registrar and Division of Health Statistics. The most recent published Cancer Incidence and Mortality Data (for 1990-1992) shows no substantial difference between Bay County and Michigan as a whole (Table 18) (57). Cancer incidence data from 1990 through 1993 on the Bay City Zip Code area 48706 (west of the Saginaw River, including Middleground Island) does show a slight, statistically significant at a probability of 5 percent, elevation of cancer incidence and rate over the 4 year period. The data for individual years from that Zip Code were not statistically significantly elevated (Table 19) (58). It is not possible to relate this slight elevation in cancer rate to any specific cause.
7. Are there any documented health problems that have been reported that could be directly linked to the Middlegrounds? Historic health impact and effects on Bay City residents during the 1950s through current.
There are no reports of health problems that can be directly linked to the Middlegrounds Landfill.
8. How will notification be made to the public regarding not eating the Great Lakes fish? I don't think it is well known.
Each year, the MDCH publishes their fish consumption advisories in the MDNR's Fishing Guide, which each angler should receive when he or she obtains a fishing license. The MDCH also issues a press release each year when the advisories are finalized. MDCH is investigating additional methods to increase public awareness of and compliance with the advisories.