PUBLIC HEALTH ASSESSMENT
PACKAGING CORPORATION OF AMERICA
FILER CITY, MANISTEE 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 are not expected to result in more than 1 case of cancer in 1 million people exposed or any increase in non-cancer health effects. Comparison values used in this assessment include:
ATSDR Environmental Media Evaluation Guides (EMEGs)
ATSDR Reference Dose Evaluation Guides (RMEGs)
ATSDR Cancer Risk Evaluation Guides (CREGs)
U.S. EPA Drinking Water Health Advisories (Lifetime)
U.S. EPA Safe Drinking Water Act Maximum Contaminant Levels (MCLs)
ATSDR derives EMEGs from the Agency's Minimum Risk Levels (MRLs) for the chemicals and estimates of exposure to soil, water, and air. ATSDR derives RMEGs from the U.S. EPA Reference Doses (RfDs) for chronic exposure and estimates of exposure to soil, water, and air. The exposure estimates are for a child, assuming pica behavior for soil ingestion(2). Daily exposure to an environmental medium containing a chemical at concentrations below the EMEG or RMEG is not likely to result in adverse non-cancer health effects. ATSDR derives CREGs from U.S. EPA cancer potency factors and adult estimates of exposure to soil, water, and air. Lifetime daily exposure to an environmental medium containing a carcinogenic chemical at concentrations below the CREG is not likely to result in more than one additional case of cancer in an exposed population of 1 million. LTHAs are derived by the U.S. EPA and are drinking water concentrations at which adverse non-cancer health effects are not likely to occur. MCLs are enforceable drinking water standards that are protective of human health over a lifetime of daily exposure to the "extent feasible" considering technological and economic constraints.
If no comparison values for a chemical in a medium exist, or there is no CREG available for a carcinogen, the chemical is considered a contaminant of concern for further evaluation.
To identify facilities which might contribute to the environmental contamination at the Packaging Corporation of America site, the MDPH 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 contained entries from 5 facilities with the same postal ZIP code as the PCA site (49660, for Manistee and Stronach): the Martin Marietta plant between the PCA site and Manistee Lake, the Akzo Salt plant on Manistee Lake in the southeast corner of Manistee, the Morton Chemical plant on Manistee Lake in south Manistee, and two other facilities in northern Manistee. The only facility listed with ZIP code 49634, for Filer City, was the PCA plant. No facilities were listed with ZIP code 49626, for East Lake. The releases from the Martin Marietta, PCA, Akzo Salt, and Morton Chemical plants are most likely to contribute to the environmental contamination at the PCA site. The two facilities with listings in the TRI on the north side of Manistee are located too far from the PCA site to contribute significantly to the environmental contamination at the site.
The operators of the Martin Marietta plant reported releases to the air of chromium compounds in 1987 and 1988 only and releases to the air and disposal by underground injection of hydrochloric acid. The operators of the PCA plant reported releases of ammonia and chlorine to the air, to Lake Michigan, and to Manistee Lake; releases of hydrochloric and sulfuric acid to the air; land disposal of 1 pound of polychlorinated biphenyls (PCBs) in 1988; and transfers to off-site disposal facilities with no environmental release of phosphoric acid and sodium hydroxide solution. The operators of the Akzo Salt plant reported transfers of sodium hydroxide solution, phosphoric acid, zinc compounds, and manganese compounds to off-site disposal facilities with no environmental releases. The operators of the Morton Chemical plant reported air releases and underground injection of hydrochloric acid, air releases of sulfuric acid, and transfers to off-site disposal facilities with no environmental release of sodium hydroxide solution and sodium sulfate solution (9).
Chromium is a chemical of concern at the PCA site, from concentrations on the site and following the criteria listed above. Air releases of hydrochloric and sulfuric acids may produce elevated concentrations of chlorides and sulfates, respectively, in downwind areas. The underground injection of hydrochloric acid may increase the chloride concentration in the aquifer which receives the injection. The TRI reports do not identify which aquifer the underground injection wells connect with. The TRI reports only indicate that the PCBs were disposed on land by "other methods", that is, some method other than an on-site landfill, land application/treatment/farming, or surface impoundment. According to PCA personnel, this report was filed after a leak from a transformer in the plant. The leak was contained by spill-control structures and was properly cleaned up, with the PCBs disposed of in accordance with applicable regulations. No environmental contamination resulted from the incident (10).
The releases of chlorine and ammonia from the PCA plant to Manistee Lake slightly affect the chloride and ammonia concentrations in the lake. The highest reported releases of chlorine (510 lb./yr. [230 kg/yr.]) and ammonia (420 lb./yr. [190 kg/yr.]) to Manistee Lake (9) are much smaller than the water flow into the lake from the Little Manistee River (170 cfs [4,800 L/s, or 1.5 x 1011 kg/yr.]) (5). The increase in chloride and ammonia concentrations in the lake due to reported PCA releases would therefore be approximately 1 part per billion (ppb) or less. The concentrations of chloride and ammonia in the water in the lake are approximately 1,000 ppb and sometimes much higher (Table 2), therefore the increased concentrations in the lake due to reported PCA releases would be negligible by comparison. No other facility reported any discharge to Manistee Lake to the TRI.
Unless cited otherwise, environmental data in this health assessment were taken from the final Remedial Investigation Report (3).
The RI contractors collected soil or sediment samples from each of the dry lagoons and from elsewhere in the lagoons area in September 1986. The samples collected included "surficial soil" samples, "after organic litter (grass, leaves, and roots) was removed." It is not clear whether they removed organic-rich soil along with the loose litter from the "surficial soil" samples. The "surficial soil" samples may not include any material from the actual surface, and therefore may not accurately represent the material someone would come into contact with on the site. Concentrations of contaminants of concern detected in these "surficial soil" samples are listed in Table 4. Calcium concentrations were extremely high in soil from most of the lagoons, attributed to the company's practice of liming the lagoons in an attempt to control odors. Samples from lagoon 1 also contained as many as 26 tentatively identified volatile and semi-volatile organic chemicals (TICs). Six TICs had estimated concentrations over 1,000 parts per million (ppm) (maximum 3,100 ppm) in a soil sample. The RI contractors reported that residues from the wastes were not detected in lagoons 4, 5, 6, 7, and 8.
The concentrations of contaminants of concern detected in deeper subsurface soil samples are listed in Table 5. These subsurface samples were collected from depths of 4.5 to 5.5 feet. These subsurface soil concentrations are comparable to those found in background samples collected near the site. Some TICs were also detected, at lower concentrations than were found in the shallow sub-surface samples.
Surface Water and Sediment
The RI contractors collected samples of surface water and sediment from each of the two lagoons that contained water all year round (Lagoons 2 and 3). The sediment samples were grab samples. Concentrations of contaminants of concern found in these samples are listed in Table 6 (water) and Table 7 (sediment). Twenty or more TICs were found in these samples, with estimated concentrations of individual TICs as high as 490 parts per billion (ppb) in water samples and as high as 1,600 ppm in sediment samples. The contaminant concentrations found were generally higher in Lagoon 3 than in Lagoon 2. One end of Lagoon 3 was used as a landfill, and the water in the lagoon includes leachate from the landfill.
A contractor for the U.S. EPA collected water samples from monitoring wells downgradient from the lagoons in August 1981. Analysis of these samples found as much as 400 ppb arsenic and 1,100 ppb cadmium (11). The RI contractors collected groundwater samples from monitoring wells on and near the site in both the shallow and deeper aquifer in October 1987 and November 1988. The MDNR contractors collected water samples from one monitoring well on-site (in the shallow aquifer) during the Manistee Lake study in 1992. Concentrations of contaminants of concern found in all three rounds of sampling are summarized in Table 8. Some of the samples also contained as many as 18 TICs. The concentrations of individual TICs were estimated to be as high as 300,000 ppb.
The 1992 MDNR-contracted survey also included toxicity testing of the groundwater. Groundwater from an on-site monitoring well proved to be acutely toxic to the test organism, Ceriodaphnia dubia (C. dubia), a small fresh-water crustacean, one of several species commonly called water fleas. The toxicity was sharply reduced by filtration with granular activated carbon, suggesting that the toxic agent was an organic compound (5).
The infiltration of pulp mill liquors into the PCA lagoons has resulted in contamination of an upper, unconfined aquifer on the east side of Manistee Lake. The contaminant plume, according to file documents, is believed to be approximately one square mile in area, moving primarily in a southwest direction toward Manistee Lake. The groundwater in this area has a characteristic black color. The deeper aquifer has not apparently been affected by the PCA contaminant plume.
The RI contractors collected water samples in 1987 from monitoring wells on the west side of Manistee Lake, in 1988 from monitoring wells on the Martin Marietta property, and in 1988 from temporary wells drilled into the bed of Manistee Lake. In 1992, the MDNR contractors sampled monitoring wells between the site and the lake and temporary wells drilled into the lake bed. The concentrations of contaminants found in the monitoring wells in 1987, 1988, and 1992 are summarized in Table 9. The concentrations found in the groundwater under Manistee Lake are summarized in Table 10. The concentrations in the monitoring wells on the east side of the lake define the groundwater contamination plume. Sodium and chloride concentrations are higher off the site than on, forming a plume of contamination that appears to originate under the Martin Marietta plant. Except for the sodium and chloride, no significant contamination was seen in the water under or west of Manistee Lake.
In November 1988, the RI contractors collected samples from 5 private wells in the site area -- 2 in East Lake, 2 in Stronach, and 1 on the Martin Marietta plant grounds between the lagoons and Manistee Lake. The results of the analysis are summarized in Table 11. The Martin Marietta plant well is screened in the lower aquifer, the other private wells are probably screened in the upper aquifer, since the lower aquifer is not thought to extend that far. The Manistee-Mason District Health Department and MDPH have sampled various private wells near the PCA site at intervals since 1988. The most recent sampling recorded in MDPH records was in May 1991 (12). No contaminant has been found in any sample from a private well near the site at a concentration above a comparison value. Martin Marietta has had to abandon private drinking-water wells on their property three times because of contamination, typically black water from the shallow aquifer leaking into the deep-aquifer wells through failure of the well casings. There is no record of chemical analysis of water samples collected during these contamination incidents. Routine monitoring of the Martin Marietta drinking water system has never detected any contamination.
The 1992 MDNR-contracted survey also included toxicity testing of the groundwater. Groundwater from the off-site monitoring wells proved to be acutely toxic to C. dubia. Water from in-lake temporary wells was found to be toxic to C. dubia on chronic exposure. The darker water was more toxic than clearer water. The toxicity was sharply reduced by filtration with granular activated carbon, suggesting that the toxic agent was an organic compound (5).
The Michigan Water Resources Commission (MWRC) and the MDNR conducted limnological surveys of Manistee Lake in 1957, 1958, 1970, 1973, 1980, 1981, and 1983. They collected water samples from the lake and analyzed the samples for general water quality parameters. The 1957 survey found very low dissolved oxygen (as low as 0.0 ppb) and high concentrations of chloride (as high as 3,450 ppm) in the water, indications of poor water quality (13). Later sampling has found some improvement in the quality of water in the lake, though the quality is still impaired (see Table 2) (14, 15, 16, 17). None of these studies included analyses of the water for any of the other contaminants of concern at the PCA site. There are many potential sources in the lake watershed that might contribute to this degradation.
The limnological surveys of Manistee Lake in 1973 and 1981 included sampling of sediment for chemical analysis. The results of these analyses are listed in Table 12 (15, 17). Sediments from throughout the lake fit the U.S. EPA criteria for "heavily polluted" with various contaminants of concern. There are many potential sources in the lake watershed for these contaminants.
The MDNR contractors collected samples of sediment from the bottom of Manistee Lake during the 1992 survey. The water associated with the sediment, what the contractors call "pore-water", was analyzed chemically and tested for toxicity to aquatic life. The concentrations found of chemicals of concern are listed in Table 13.
"Pore-water" from the target area, directly downgradient from the PCA lagoons, proved to be acutely toxic to C. dubia, while that from a control area south of the site, generally up-current, was much less toxic. The darker water was more toxic than clearer water. The toxicity was sharply reduced by filtration with granular activated carbon, suggesting that the toxic agent was an organic compound (5).
The Michigan Water Resources Commission (MWRC) and the MDNR have conducted biological surveys of Manistee Lake in 1953, 1954, 1957, 1973, 1975, and 1983. In the 1953 sampling, the bottom was sampled in 24 locations, all deeper than 20 feet, only 6 of which contained any macroinvertebrates. The one sample with the largest number of individuals (400 per ft2) and the largest number of species (12) was the closest to where the Little Manistee River enters the lake, at the lake's south end. The majority of species found at most of the locations are considered pollution-tolerant. By way of comparison, in a 1952 sampling of White Lake, approximately 60 miles south of Manistee Lake, most of the 16 samples exceeded 2,000 individuals per ft2, with only 2 samples as low 400 individuals per ft2, the maximum density found in Manistee Lake (18). The 1954 sampling of the same locations in Manistee Lake yielded similar results to the 1953 sampling (19). In 1957, the MWRC collected 20 samples of bottom materials, 4 of which duplicated samples from the earlier samplings. Five of the samples were from deeper than 20 feet, only 1 of which, from the northern end of the lake, contained any macroinvertebrates. In shallower waters, they found a more extensive biota, limited in numbers and variety in the southern part of the lake while the northern part of the lake contained a more balanced biota. Again, the biota from the southern part of the lake consisted of pollution-tolerant species (13). The 1973, 1975, and 1983 samplings confirmed the results of earlier samplings, with some modest improvement noticed (15, 16).
The MDNR contractors surveyed the benthic (bottom-dwelling) invertebrate community of Manistee Lake in 1992. They compared the communities at two sites, a control area at the south end of the lake and a target area in the presumed zone of discharge of groundwater from the PCA site. The sediment "pore-water" from the target area was dark and highly conductive, indicative of groundwater at the PCA site. The total number of individual invertebrates found in the two areas was not significantly different. The diversity of the invertebrate community in the target area was significantly less than that in the control area, with certain contamination-resistant species more common and other species absent (5).
In June 1991, the MDNR, as part of their Fish Contaminant Monitoring Program, collected eight smallmouth bass and four walleye from Manistee Lake. An MDPH laboratory analyzed samples of these fish, fillets with the skin on, for mercury, hexachlorobenzene, various chlorinated styrenes, polychlorinated biphenyls (PCBs), various pesticides and metabolites, terphenyl, and polybrominated biphenyls (PBBs). Concentrations of the chemicals found in the fish are listed in Table 14. These concentrations are typical of those found in fish from Michigan waters, and the chemicals are probably not related to the PCA site (20).
In preparing this public health assessment, the MDPH relied on the information provided in the referenced documents and assumed that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analysis and conclusions drawn for this Health Assessment is determined by the reliability of the referenced information.
Any qualification on the data cited for this report is discussed with the data.
Access to the site is partially restricted. Trespass is occurring mainly via a power company
right-of-way to the lagoon area. The physical hazards that exist include the possibility that a
trespasser could fall into a lagoon containing water or break through the surface of the lagoon
containing 30 feet of black liquor and sludge. PCA is discussing restricting this access route
with the power company.
To determine whether nearby residents are exposed to contaminants migrating from the site, 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.
Surface Soil and Sediments On-site
As described above in the Environmental Contamination and Other Hazards section, the RI contractors did not collect any soil samples that included actual surface material. The shallow sub-surface soil samples they collected contained metals and semi-volatile organic chemicals at concentrations above ATSDR Comparison Values (Table 4). They did collect grab samples of sediment from the two lagoons that contained water at the time, which also exceeded Comparison Values for various metals (Table 7). One of the lagoons only intermittently holds water, exposing the sediments between such times. Assuming that the surface soil composition is comparable to that in the shallow sub-surface soil samples, people on the site may be exposed to the contaminants by direct skin contact, incidental ingestion, and inhalation of contaminated fugitive dust. Access to the site is only partially restricted, and signs of trespass have been seen on the site. There is considerable evidence from tracks and litter that the dewatered lagoons and surrounding areas are used for hiking, picnicking, and recreational vehicles. This evidence indicates that these pathways may be complete.
When contaminant-carrying groundwater enters Manistee Lake, the contaminants may mix into the lake water or settle into the sediments. The "pore-water" in the sediments where groundwater from the site discharges to the lake contains some unidentified substance that is toxic to certain aquatic invertebrates. Fish, plants, and other biota in Manistee Lake could then accumulate contaminants from the water and sediments. Contaminants could accumulate up the food chain to species of commercial or sport utility. It is not known whether the unidentified toxic substance in the sediment "pore-water" accumulates through the food chain. Manistee Lake supports a high quality recreational fishery for both warm and cold water fish species. People who eat the fish could ingest contaminants. There were reports of impaired flavor of panfish taken from the lake in the early 1950s, of steelhead trout and other salmonids in the middle to late 1960s, and of chinook salmon in 1969. The 1950s and 1960s taint incidence was traced to discharges from the ABBCo/PCA plant, and the company changed their practices to eliminate the discharge. That in 1969 has been attributed to sediments from past discharges. Taint tests on fish collected from the lake in 1975 found no off-flavor or taint (15). Chemical analysis of fish from the lake has not found any special contamination problem. The standard set of analyses performed for the MDNR's Fish Contaminant Monitoring Program does not include many of the major contaminants of concern at the PCA site, however.
There is potential for direct wildlife contact with the contaminants in the surface soil as the lagoon area is frequented and inhabited by numerous birds and mammals. Hunting for small game, birds, or deer, is a common recreational activity in the region around the site. There is a State Game Area approximately 2 miles north of the site, the National Forest lands east of the site are also frequented by hunters, and an occasional hunter might be found on any undeveloped land in the region, regardless of postings. There is no data available on any contamination of wildlife from the site area. There is no firm information available regarding the frequency of hunting on the site or in the area where animals that use the site might range, or what prey the hunters might seek.
Liquid and slurried wastes were pumped from the PCA plant to the lagoons from 1951 through 1974. This produced a large mass of waste material in the lagoon area, and waste water and rain water percolating through the wastes have carried contaminants into the shallow groundwater aquifer at the site. There are currently no residences in the area of the contaminant plume. If there were a house that was served by a well that taps the contaminated aquifer, the residents could be exposed to contaminants by ingestion, by dermal contact, and by inhalation of volatile contaminants. The contaminated groundwater is discolored and has a distasteful odor, which is likely to discourage any long-term household use of the water. However, these are merely deterrents to use of the water, and the pathway is potentially available for future exposure.
The Martin Marietta (MM) Plant and one of its industrial process wells are located on the east shoreline of Manistee Lake, approximately one mile downgradient from the PCA lagoons, above the contaminant plume from the lagoons. The MM plant produces refractory brick from magnesium-rich brine and draws process water from the lower aquifer using several large volume production wells. In the past, they have drawn water from the deep aquifer for potable uses for their workers. There are no indications that the MM water supply from the deep aquifer is being affected by the PCA contaminant plume, in that the wells have generally not shown the discoloration characteristic of the PCA contamination plume. There have been a few incidents reported of MM drinking-water wells drawing up black groundwater. The wells supplied the plant's drinking fountains, washrooms, and showers. These incidents were attributed to corrosion perforating the well casing, allowing water from the upper aquifer to penetrate. The affected wells were immediately taken out of service and replaced when the contamination was detected. Because of these incidents, a 1990 MDPH survey that found the MM water supply system to not be in compliance with MDPH well construction standards, and the vulnerability of their wells to contamination from the PCA lagoons, in 1990 the MDPH formally advised Martin Marietta to cease use of wells on their property for potable purposes (21). The company has obtained an alternative potable water supply from Filer City and abandoned and sealed their potable water wells in 1992 (22). During the incidents of black water in the drinking water wells, the workers were exposed to contaminants in the water by ingestion, dermal contact, and inhalation.
The municipal wells serving the City of Manistee, Oak Hill, and Filer City are all on the west side of Manistee Lake. The contaminated shallow aquifer, on the east side of the Lake, flows toward the Lake and is presumed to discharge into the Lake. The municipal wells are from 150 to 200 feet deep, drawing water from beneath clay layers (23). The wells are probably protected from any site-related contamination. The wells are also routinely sampled by the MDPH, and no contamination has been reported.
Hydrogeologic studies indicate that groundwater in the area of the PCA site either completely discharges into Manistee Lake or may flow under Manistee Lake to discharge into Lake Michigan. The upper aquifer, in which the PCA contaminant plume is confined so far as is known, is presumed to discharge into Manistee Lake. There is no currently available evidence that the plume extends under or west of Manistee Lake. Contaminants in the groundwater mix into the water of the lake. People use the lake for recreation, including swimming, boating, and fishing. In doing so, they might be exposed to contaminants by incidental ingestion and dermal contact. There is no record of analysis of lake water for site-related contaminants, though such water quality parameters as chloride and dissolved oxygen in the lake have been measured at levels indicating very poor quality water in the lake. The flow into the lake from the Little Manistee River is approximately 170 times the groundwater discharge from the site area. Therefore the lakewater concentration of any contaminant present in the groundwater would increase by approximately 1/170 of the concentration in the groundwater. For known contaminants in the groundwater, this increase is not likely to raise the concentration in the lake above a level of concern. However, the material in the groundwater that is toxic to aquatic invertebrates has not been identified, its concentration has not been reliably measured, and its potential for human toxicity has not been evaluated.
Lake Manistee Sediments
The contaminated groundwater from the site discharges to Lake Manistee. As it does, various
chemical mechanisms can cause contaminants to adhere to particles of sediments. People using
the lake for swimming, fishing, boating, and other recreational uses might come into contact with
the sediments. Contact with contaminated sediments might lead to exposure to the contaminants
through dermal absorption or incidental ingestion. The "pore water" within the sediments in the
area where groundwater from the site discharges contains the same contaminants that are present
in the groundwater. In addition, sediments from throughout the lake have contained
contaminants that might have come from any of several sources in the lake's watershed. The
population of bottom-dwelling animals in the lake has been heavily affected by the pollution in
the sediments. Sediments that were collected for analysis were generally from 20 feet deep or
deeper. There is therefore little record of analysis of sediment that people are likely to come into contact with.
The major pathway for human exposure to site-related contaminants that is reasonably expected to be complete is that for trespassers on the site exposed to surface soil and sediments in the lagoons area. Calculating an estimated exposure dose for such an individual is extremely uncertain. The most likely trespassers would be teenagers or young adults, for estimation purposes weighing 70 kilograms (154 pounds) and incidentally ingesting 100 milligrams of soil per day.
Assuming the surface soil contains the concentrations listed in Table 4 and assuming daily exposure, which is unlikely to occur, none of the estimated exposure doses for the contaminants of concern would exceed the corresponding Minimal Risk Levels (MRLs) or Reference Doses (RfDs). It is unlikely that anyone spends more than 3 hours, once a week, on the site. Therefore, it is unlikely that any trespasser on the site would be at hazard of non-cancer adverse health effects. MRLs, derived by the ATSDR, and RfDs, derived by the U.S. EPA, are levels of exposure below which it is commonly assumed that adverse health effects are not likely to occur. No trespasser is likely to ingest enough of any of the chemicals in the soil on the site to exceed the doses at which adverse health effects have been observed in laboratory studies in animals or epidemiological studies of humans. Several of the chemicals found (or potentially found) in the shallow sub-surface soil -- cadmium, hexavalent chromium, lead, nickel, and 4-methylphenol -- are carcinogens, but there is not enough information available to evaluate the cancer risk from ingestion of the chemicals.
The workers at the Martin Marietta plant west of the site were briefly, and intermittently, exposed to contaminants in the groundwater when some of the plant's drinking-water wells drew up black water from the contaminated aquifer due to corrosion of the wells' casings. There are no reports of any analyses of the contaminated water in the plant's potable water system. The incidents of contamination were also reportedly brief, lasting a matter of days. Assuming, as a conservative approximation, the contaminated water in the plant's water system contained the highest concentrations of chemicals found in the groundwater on the site (Table 8), it is not likely that any worker at the plant ingested enough of any chemical to exceed MRLs or RfDs, or to incur a significant risk of cancer. A few chemicals present in the groundwater, cadmium, hexavalent chromium, lead, and nickel, are considered potential carcinogens, but there is not enough information available to calculate the risk from ingesting the chemicals.
The concentrations of contaminants found in fish from Manistee Lake, as listed in Table 14, do not exceed MDPH Levels of Concern (generally based on U.S. FDA Action Levels), and hence, no special Fish Consumption Advisories have been issued for the Lake. There is a general advisory in effect for all inland lakes in the state, including Manistee Lake, due to a general statewide pattern of mercury contamination. At least one fish collected from approximately 70% of the inland lakes in the State where fish have been collected by the MDNR or U.S. EPA since 1980 has contained mercury at a concentration that exceeds the MDPH Level of Concern of 0.5 parts per million (ppm). This mercury generally comes from natural sources and from atmospheric deposition. The generic advisory reads as follows:
No one should eat more than one meal a week of fish of the following kinds and sizes from any of Michigan's inland lakes: rock bass, perch, or crappie over 9 inches in length; largemouth bass, smallmouth bass, walleye, northern pike, or muskie of any size. Nursing mothers, pregnant women, women who intend to have children, and children under age 15 should not eat more than one meal per month of the fish species listed above (24).
The mercury levels found in Manistee Lake fish species tested are lower than those found in other lakes in the State. As a precaution, however, Manistee Lake is included in the state-wide advisory.
A person who eats more than one 0.5-pound meal of fish from Manistee Lake every 4 weeks might ingest enough mercury to exceed the MRL for acute-term ingestion of organic mercury compounds. Mercury present in fish tends to be contained in organic compounds. The MRL is derived from an experiment in which developmental problems were seen in the offspring of rats whose food contained methyl mercuric chloride (25).
The MDPH PCB Trigger Level for fish consumption advisory purposes is 2 ppm, the Action Level used by the U.S. Food and Drug Administration (U.S. FDA). Since none of the fish from the lake exceeded this level, the MDPH has issued no advisory concerning consumption of fish from the lake because of the PCBs. However, calculating the health risks from consuming fish from Manistee Lake suggests that eating more than two meals a month of fish containing the maximum concentration of PCBs found in these fish may result in a dose that exceeds the U.S. EPA Reference Dose (RfD) for low birth weight in the offspring after exposure to Aroclor 1016 (the commercial name for a specific PCB mixture) (26). Some laboratory animals exposed to PCBs in their diet developed liver cancer. There is weak evidence linking exposure to PCBs to cancer in humans. The U.S. EPA has classified PCBs as a probable human carcinogen (U.S. EPA Class B2) (27). Using the results from experiments on animals to estimate human cancer risk, consumption of more than three meals per year of fish from the lake may result in a significantly increased risk of developing cancer. PCB concentrations similar to those found in fish from Manistee Lake are also found in fish from many other lakes in and around Michigan, and there is no evidence that the PCBs in the fish are connected to the PCA site.
People in Manistee County are concerned about what they perceive as a high rate of cancer incidence and mortality in their community. There are several known, probable or possible carcinogens present in shallow sub-surface soil at the PCA site, where trespassers might come into contact with them. In addition, PCBs have been found in fish from Manistee Lake at concentrations such that a person eating the fish may incur a significant risk of developing cancer.
Cancer mortality data for Stronach Township and Filer Township from 1980 through 1991 are summarized in Table 15, Table 16, and Table 17. Stronach and Filer Townships are sparsely populated and have very few cases of cancer each year. A variation of one or two in the number of cancer cases or deaths per year in either of the Townships in any given year would produce a large variation in the calculated incidence or mortality rates, hence the calculated rates would not yield any useful information.
Cancer incidence data for 1985 through 1990 for zip code area 49660, which includes the site area and the City of Manistee, are summarized in Table 18, Table 19, and Table 20. (This zip code area contains approximately 12,000 people, approximately 60 per cent of the population of Manistee County.) Other zip code areas near the site had either no population data available or no cancer cases reported. Ratios of observed to expected cases and deaths were calculated for zip code 49660 for each year from 1985-1990 for cancer of all sites (Table 18) and for all six years for selected cancer sites (Table 19, Table 20).(3) The numbers of "expected" cases were calculated by applying the age- and sex-specific cancer rates for Michigan to the age- and sex-specific zip code area population estimates. When the number of observed vs. expected cancer cases are identical, the ratio is 1.0. When there are more cases observed than expected the ratio is greater than 1.0. Conversely, when there are fewer cases than expected, the ratio is less than 1.0. The magnitude of the difference (higher or lower) is checked to see if it is statistically different from 1.0 taking into consideration factors such as population size, the number of cases each year, and the degree of variation from year to year.
None of the incidences in the zip code area were significantly above that for the State as a whole (Table 18). The population of the Zip Code area is not large enough for a reliable calculation of incidence rates for most specific cancer sites, even considering the entire period surveyed (Table 19). Table 20 shows that the incidences of cancers of the colon, larynx, lung, and brain were not significantly different in the Zip Code area from the State as a whole (29).
The MDPH and the Manistee-Mason District Health Department have spoken to area residents regarding their concerns about cancer incidence in the site area and wider areas. The MDPH has evaluated available cancer incidence and mortality data for Manistee County. As described in the Health Outcome Data Evaluation section above, the initial evaluation of cancer data does not show that the cancer incidence in Manistee County is greater than for the State of Michigan as a whole. This evaluation cannot be conclusive as to potential site-related effects because of the small population in the potentially affected area. MDPH and the Manistee-Mason District Health Department are available to answer any questions or concerns about disease or mortality that a resident feels may be related to this or any other environmental contamination incident.