Response to Public Comments
TEN MILE/LANGE/REVERE DRAINAGE SYSTEM
(a/k/a TEN MILE DRAINAGE SYSTEM PCB SPILL)
ST. CLAIR SHORES, MACOMB COUNTY, MICHIGAN
Testing of canal sediments prior to a dredging project in St. Clair Shores, Macomb County, Michigan, revealed high levels of polychlorinated biphenyls (PCBs). The resulting investigation found that the storm water sewer of the Ten Mile/Lange/Revere Drainage System, which discharges to the tested canal, had been contaminated by what was likely an illicit release of the chemicals into a storm drain. Water and sediment samples from the storm sewers, catch basins, sanitary sewers, and the Lange/Revere Canal had PCBs and lead at levels of concern. Water sampled from a pond that occasionally receives canal water had a high concentration of PCBs. An air sample taken near where the storm sewer discharges into the canal indicated a PCB air concentration of concern. Soil testing of residential yards irrigated with canal water did not show PCBs at levels of concern, but did reveal concentrations of arsenic above the state generic clean-up criterion.
The levels of PCBs, lead, and other chemical of interest in the sewer systems and the Lange/Revere Canal pose no apparent public health hazard. The PCBs in the air near the sewer outlet to the canal pose no apparent public health hazard. Soil levels of arsenic pose an indeterminate health hazard.
The contamination should be addressed by regulatory authorities so that further environmental degradation, which could lead to adverse public health effects, does not occur. Residents should avoid contact with the canal until the contamination has been addressed. Residential yard soils should be further evaluated, to determine if a health hazard exists, and remediated if necessary.
The purpose of this health consultation is to assess the public health implications associated with the PCB contamination of the sanitary and storm water sewer systems of, and the canal connected to, the Ten Mile/Lange/Revere Drainage System (Ten Mile Drainage System) in St. Clair Shores, Macomb County, Michigan. The US Environmental Protection Agency (EPA) and the Macomb County Health Department requested a public health assessment from the federal Agency for Toxic Substances and Disease Registry (ATSDR). The Michigan Department of Community Health (MDCH) conducts assessments for ATSDR under a cooperative agreement.
MDCH and ATSDR consider environmental data and community health concerns when forming a health opinion. Health outcome data (morbidity and mortality) might be considered as well. Based on their conclusion, the agencies then make recommendations to ensure public safety and health. This consultation will address specific health concerns in the Community Health Concerns section and its related appendix. Other non-health related questions or issues regarding the PCB contamination will not be discussed but will be referred to the appropriate agency.
In July 2001, as part of the permitting application process for proposed dredging activities, a private consultant hired by Macomb County collected for chemical analysis sediment samples from the Lange/Revere Canal (the Canal) located in the city of St. Clair Shores, Michigan (Figure 1). Elevated levels of PCBs were found in the samples. The county notified the US Army Corps of Engineers and the Michigan Department of Environmental Quality (MDEQ) of the results. Subsequent testing verified the results.
The Canal receives storm water from the Ten Mile Drainage System and empties into Lake St. Clair, which empties into Lake Erie via the Detroit River. The drainage system is bordered to the north by Bon Brae Avenue, to the east by Jefferson Avenue, to the south by Lange Avenue, and to the west by Harper Avenue (Figure 2).
In December 2001, MDEQ began an investigation of the storm water system upstream of the storm water outfall into the Canal, to determine if there was an upstream source. In addition, the Macomb County Public Works Office (PWO) hired an environmental consultant to collect samples from the Ten Mile Drainage System. Sample results confirmed that elevated levels of PCBs were present in the Canal and storm water sewer. On March 4, 2002, MDEQ notified EPA Region 5 of the presence of elevated levels of PCBs in the Canal. MDEQ requested technical assistance from the EPA in assessing the possible source and the range of contamination of the PCBs. The storm water and sanitary sewer systems and the Canal are located within a primarily residential area with small commercial businesses. According to a preliminary review of city and county records, there are no known current or historic industrial properties in the immediate area (EPA 2002a, b).
On March 5, 2002, EPA requested technical assistance to conduct an emergency site assessment of storm water sewers and the Canal to determine the scope of contamination of the PCBs and the threat to human health and the environment. On March 6, 2002, the Superfund Technical Assessment and Response Team (START) arrived at the site to assist with the investigation. START, with assistance from the City of St. Clair Shores and the US Coast Guard, began collecting samples from the storm water sewer system in order to determine the extent of PCB contamination. Sediment and water samples were collected, or when sediment was inaccessible, a wipe sample was collected. The samples were analyzed for PCBs and total Resource Conservation and Recovery Act (RCRA) metals. (1) Several sediment and water samples were analyzed for volatile and semivolatile organic compounds (VOCs and SVOCs), pesticides, and additional metals. Real-time air monitoring was performed at each sample location. START also collected water and wipe or sediment samples from the sanitary sewer system along Bon Brae Avenue as part of the drainage system investigation. The majority of samples collected in the sanitary system were wipe and water samples due to the inaccessibility of sediment at the sample locations (EPA 2002a, b).
On March 7, 2002, PWO installed a steel weir at the head of the Canal at the discharge point for the storm sewer drainpipe to prevent additional sediment from entering Lake St. Clair (EPA 2002a, b).
On March 12, 2002, START began collecting sediment samples from the Canal in order to determine the vertical and horizontal extent of sediment contamination in the waterway. Core samples were collected every six inches, to 24 inches depth, and analyzed for PCBs and RCRA metals. The investigators also collected Canal water for analysis (EPA 2002a, b).
Preliminary analytical data revealed PCB contamination of both the storm and sanitary sewer systems. The results from the storm sewer samples were much greater than those from the sanitary sewer. The data indicated an area of high levels of PCB contamination near the intersection of Bon Brae and Harper Avenues, suggesting that that area was the point of entry for PCBs into the drainage system. Dye testing was performed in the drainage system at a car wash located at the intersection. The test results indicated that the parking lot drains are connected to the storm sewer system and those in the car wash bays are connected to the sanitary sewer system. The MDEQ and START collected samples from the drains and catch basins on the car wash property and submitted them for analysis (EPA 2002a, b).
Sediment samples collected from the Canal showed elevated PCB concentrations near the storm water drainage outlet. Higher PCB concentrations were detected in the surficial sediment samples (from zero to six inches), and concentrations generally decreased with depth. High concentrations of various RCRA metals were also found in the Canal sediment. Samples collected from the outlet of the Canal, near Lake St. Clair, had much lower PCBs concentrations, indicating that the contamination in the Canal was a result of storm water discharge rather than an influx from Lake St. Clair (EPA 2002a, b).
EPA, acting on a request from the City, sampled the sanitary sewer line of one private residence on March 25 and April 4, 2002. The resident had recently hired a sanitary sewer service company to remove roots from the connection running from the house into the sanitary sewer on Bon Brae Avenue. The resident was concerned, upon hearing about the contamination in the Ten Mile Drainage System, that contaminated debris may have been introduced into the home's sewer line. Wipe samples were taken twice from the inside structure of clean-out ports for a weeping tile (drainage tile placed at the outside of the bottom of the basement foundation) and for the sanitary sewer connection line (Tetra Tech EMI 2002).
Following recommendations from the state and local health departments, EPA collected soil samples from the front and back yards and gardens of selected residences along the Canal on Ten Mile Road and Lange and Revere Avenues on July 25, 2002. Selection was based on information collected from the residents regarding use of Canal water for irrigation. Samples were analyzed for PCBs and RCRA metals to determine if any contamination in the Canal was being transferred to residential soils. Residents whose yards were sampled were notified of their individual results by the Macomb County Health Department. The county health department also notified the remaining homeowners along the Canal about the testing, indicating that some tested yards had concentrations of arsenic above the state residential clean-up criterion, that more information would be gathered, and that residents would be kept informed of the situation (Macomb County Health Department 2002a, b, c).
On March 13, 2002, a public meeting hosted by EPA was held with local residents to discuss the sampling events and preliminary analytical data. The City of St. Clair Shores, PWO, Macomb County Health Department, and MDEQ participated in the meeting as well. An information repository was established at the St. Clair Shores Public Library, and information was posted and is kept up-to-date on the city's website. Sampling location maps were also posted at City Hall (EPA 2002a, b).
On May 16, 2002, Toxic Free Shores (TFS), a coalition of concerned citizens and environmental organizations, released a statement that included nine demands for immediate action and a list of questions regarding the PCB event (Appendix A). The demands were addressed by federal, state, and local officials involved in the investigation (Appendix B). On June 5, 2002, TFS hosted a public forum in St. Clair Shores to share information with the public and gather questions and concerns for the involved agencies. On June 17, 2002, the coalition hosted a public meeting, inviting the agencies to respond to the nine demands issued in May and to dialogue with residents. Representatives from EPA, ATSDR, MDEQ, MDCH, PWO, the Macomb County Health Department, and the City of St. Clair Shores participated in the meeting.
On August 14, 2002, the City of St. Clair Shores sponsored an informational forum to update residents on the progress of the cleanup. Representatives from the agencies attending the June 17 meeting were present to speak one-on-one with residents.
On February 6, 2003, the City of St. Clair Shores hosted a public meeting to update residents on the cleanup. Representatives from the agencies attending the previous meetings were present to address community concerns and answer questions. At this meeting, the community requested an extension of the public comment period for the draft health consultation released by MDCH so that the community could have its experts review the data. The comment period was extended an additional 60 days.
Updates were and continue to be sent by the City of St. Clair Shores to the residents living near the Canal and the Ten Mile Drainage System. Appendix C is a copy of the first informational newsletter delivered to area residents. Appendices B and D contain the May/June and July/August 2002 issues, respectively, of the Inside St. Clair Shores newsletter articles, published by the city, titled "PCB Information and Investigation: Just the Facts on the 10-Mile Drainage District", copies of which were hand-delivered or mailed to homeowners and businesses in the area and available at the city's website.
Environmental samples taken by the EPA and MDEQ were analyzed by Clayton Group Services (Novi, Michigan) and AAC Trinity (Farmington Hills, Michigan), facilities enrolled in EPA's Contract Laboratory Program (CLP). This program was developed to fill the need for legally defensible results supported by a high level of quality assurance (i.e., data of known quality) and documentation. Prior to becoming CLP certified, analytical laboratories must meet stringent requirements for laboratory space and practices, instrumentation, personnel training, and quality control ( EPA 1989).
When MDCH received the data packages from START, a toxicologist reviewed the data validation reports to identify any qualifiers, or codes, associated with the data. Qualifiers are attached to certain data by either the laboratories conducting the analyses or by technicians performing data validation. These qualifiers often pertain to quality assurance/quality control (QA/QC) deviations and generally indicate questions concerning chemical identity, concentration, or both. Qualifiers typically seen in analytical reports are U, J, and UJ. "U" indicates that a compound was analyzed for but not detected in the sample at the detection limit listed. "J" indicates that the value given as a result is an estimate, because of QA/QC deviations. Data with this qualifier attached are still usable in an assessment, but they add uncertainty to the results and should be discussed if they contribute significantly to any risk. "UJ" indicates that the result is an estimated amount but, for QA/QC purposes, it is considered not detected. These three qualifiers were attached to some of the data pertaining to the PCB contamination of the Canal. As well, a fourth qualifier, R, was occasionally used. "R" indicates that, for QA/QC reasons, the result is unusable and therefore rejected (EPA 1989).
Upon review of the data validation reports, MDCH concurred with START's conclusions regarding acceptability of qualified data: results qualified with U or UJ were labeled as not detected, results qualified with J were accepted at their numerical value, and results qualified with R were rejected.
Canal and storm drain sediment and water samples taken by Environmental Consulting and Technology, Inc., the contractor for PWO, were analyzed by RTI Laboratories, Inc., and Midwest Analytical Services, Inc., which are not CLP-certified. Therefore, the validity of the data is questionable. Nonetheless, the data reported by these labs were compared to that for the EPA- and MDEQ-collected samples and found to be within the ranges reported by the federal and state agencies. These data are not discussed further.
Risk and health assessments are not exact sciences, for they rely on the most current information available and professional judgment as a basis for recommendations on which stakeholders (e.g., the community, regulatory agencies) can base informed decisions. While scientific research has increased the understanding of effects of chemicals, many unknowns remain. Uncertainty exists at each step of the assessment process and must be acknowledged.
After a no-observed or lowest-observed adverse effect level (NOAEL or LOAEL) is determined from a key research study, numbers called "uncertainty factors" are applied to that value in order to achieve an acceptable level of protection. These factors attempt to account for converting the dose from a LOAEL to a NOAEL (if none of the doses in the key study resulted in no adverse effects), extrapolating animal results to possible human health effects, accounting for a study that was less-than-lifetime (subchronic) to long-term (chronic), and protecting sensitive subgroups within a population, such as children or those whose immune system is impaired.
Analytical data results introduce uncertainty. A result represents a snapshot of a chemical in a medium at a particular time. A second sample, whether taken immediately after the first or weeks later, would not necessarily yield the same value, due to degradation or movement of the compound, or because the compound is not in a homogeneous mixture with the medium. Qualified data indicate uncertainties in analyte identification or concentration or both. Matrix interferences, such as when contaminants exist in the tested media at concentrations above the maximum reporting limit for a specific method or machine, can make the chemical picture to be drawn blurred or obscure. Identifying the specific mixtures of PCBs, called Aroclors, becomes more of an art than a science when the PCBs have aged and are not 100 percent comparable to a standard.
When estimating doses to which certain populations may be exposed, assessors must use assumptions about the behavior and characteristics of that population. Default values are used unless site-specific information is obtainable.
Two terms linked with uncertainty are accuracy and precision. "Accuracy" defines how close an obtained value is to the actual, true value. It is dependent on research dose spacing, QA/QC adherence, and the skill of the technician, among other factors. "Precision" defines how close repeated observations are to each other. Precision also is dependent on QA/QC adherence and technician skill. As well, the variability within the population being studied, whether it is a highly inbred strain of laboratory rats, a diverse human population, or environmental samples separated by time and/or distance, will affect precision. Accuracy can be controlled more easily than precision. The goal of controlling these two aspects of uncertainty is to obtain adequate, representative, quality data.
Upon review of the data collected, MDCH concluded that, while uncertainty did and does exist, there was sufficient information on which to base their conclusions and recommendations. Detailed discussion of the data follows.
Tables 1-4 show the concentrations of PCBs and metals detected in water, sewer sediment, and Canal sediment samples and the amounts of PCBs detected in wipe samples, respectively, taken by EPA or MDEQ from the Ten Mile/Lange/Revere Drainage System. Several sample locations were sampled on more than one date. In those cases, the highest analytical result is shown for that location and medium. The analytical results from the air and soil sampling are discussed in the text.
It should be noted that the water samples were not filtered. Therefore, the concentrations of PCBs detected may reflect suspended sediments and not PCBs in the water column itself.
The water concentrations in the storm and sanitary sewers and catch basins were compared to the MDEQ Groundwater Contact Criteria (GCC) for the specific chemicals. The GCC identifies a groundwater concentration that is protective against adverse health effects resulting from dermal exposures to hazardous substances in groundwater such as could be experienced by workers in subsurface excavations. The criteria are protective of only chronic, not acute, effects, and address only dermal exposure, not incidental ingestion nor inhalation of any volatiles. Although the water in the sewers and catch basins is not groundwater but rather surface-derived, the GCC is applicable for this scenario.
There were no exceedances of the concentrations of RCRA metals with corresponding GCCs in the water samples from the sewers and catch basins. However, lead does not have a GCC due to an inadequate database in this area for this chemical. The maximum concentration of lead in sewer water (270 parts per billion [ppb]) was found in the storm sewer on Harper Avenue between Ten Mile Road and Hudson Avenue (sample M4205). Qualitative discussion regarding lead in the sewers' water follows in subsequent sections.
There were exceedances of the GCC for PCBs (3.3 ppb) in samples from both sewer systems and the catch basins. The maximum concentration of PCBs in sewer water (510 ppb) was found in the storm sewer on Bon Brae Avenue, near the intersection with F Street (sample M4281). The next highest storm sewer PCB concentration, 98 ppb, occurred at the intersection of Harper and Bon Brae Avenues (sample M7178). Overall, the highest PCB concentrations in sewer water were in the storm sewers on Bon Brae Avenue. The water in the catch basins and sanitary sewers had much lower concentrations of lead and PCBs than did the storm sewers. Qualitative discussion regarding PCBs in the sewers' water follows in subsequent sections.
Full VOC/SVOC and organochlorine pesticide analyses were conducted on two of the storm sewer water samples, M4335 and M7183. None of the compounds tested for were detected in either sample except for bis(2-ethylhexyl)phthalate in sample M7183, which was detected at a concentration well below its GCC and is therefore not of interest for this assessment. Sample M7183 also underwent more extensive metal analysis. There were no exceedances of the concentrations of metals with corresponding GCCs. Calcium, lead, potassium, silicon, and titanium do not have GCCs due to an inadequate database in this area for these chemicals. The values reported for potassium and titanium (2,300 and 20 ppb, respectively) were qualified as estimates; the values for the other three metals (22,000, 11, and 2,600 ppb for calcium, lead, and silicon, respectively) were not qualified. Qualitative discussion regarding the concentrations of these five metals follows in subsequent sections. More extensive analyses were not conducted on any sanitary sewer or catch basin water samples.
The MDEQ does not generate criteria to protect residents from adverse health effects that could be caused by dermal contact with contaminated surface water. However, the GCC may be adjusted to provide an unofficial screening level to which chemical concentrations in water samples can be compared. Residents normally would not be exposed to waters in the sewer system but would be exposed to the Canal water if they were to swim in it. Appendix E shows the steps taken to calculate adjusted GCCs for PCBs and barium, the only RCRA metal detected in the Canal water with a corresponding GCC. All of the Canal water samples met or exceeded the most protective adjusted GCC for PCBs (0.1 ppb). The concentrations were highest on the west end of the Canal. The concentrations for barium in the Canal water did not exceed the adjusted GCC for that metal. Lead also was detected in the Canal water. As mentioned earlier, this metal does not have a GCC. Qualitative discussion regarding the concentrations of lead in the water of the Canal follows in subsequent sections.
All six of the Canal water samples were analyzed for VOCs and SVOCs. Only one sample, 22501L, reported any detectable analytes, those being toluene and total xylenes at 1.8 and 3.5 ppb, respectively. Appendix E shows the steps taken to calculate adjusted GCCs for toluene and total xylenes. The concentrations of toluene and total xylenes detected in the Canal water were well below the adjusted GCCs for these compounds.
Wahby Pond, in Wahby Park at the corner of Revere and Jefferson, is occasionally refilled with water from the Canal. The pond was sampled once during the investigation and analyzed only for PCBs. The sample was taken near the inlet from the Canal (2002, D. Sawicki, EPA START, personal communication). The results indicated that 52 ppb PCBs were in the sample.
Local drinking water intakes are located on Lake St. Clair, several miles away from the Ten Mile Drainage System and the Canal, and are not considered to be at risk from the isolated PCB contamination. In March 2002, water from local drinking water intakes was sampled. According to MDEQ, these water samples did not contain detectable levels of PCBs.
The sediment concentrations in the storm and sanitary sewers and catch basins were compared to the MDEQ Industrial Direct Contact Criteria (DCC) for the specific chemicals. The Industrial DCC identifies a soil concentration that is protective against adverse health effects resulting from long-term ingestion of and dermal exposure to contaminated soil in an industrial setting. The criteria are protective of only chronic, not acute, effects, and they do not address inhalation of any volatiles. Although the solids in the sewers and catch basins are sediments and not soils, the Industrial DCC is applied for this scenario in this assessment. An industrial land use scenario was used, rather than a commercial or residential one, because access to the sewer system by the general public is and will continue to be reliably restricted.
The PCB concentrations in the storm sewer were up to 2,000 times greater than those in the sanitary sewer or catch basins. The highest concentration found, 121,000 parts per million (ppm), was reported in the full chemical analysis for sample M4335, which was taken at the intersection of Bon Brae Avenue and E Street. In general, the highest PCB concentrations in the storm sewer sediment were found in samples taken along Bon Brae Avenue, with values exceeding 100 ppm. The only RCRA metal in the sediment samples from the sewers and catch basins that exceeded its corresponding Industrial DCC (900 ppm) was lead. This exceedance occurred in only one sample, the second sample of two taken for M4334, taken March 14, 2002 from the storm sewer near the intersection of Bon Brae Avenue and C Street. The concentrations of lead in the sanitary sewer and catch basins were much less than those from the storm water sewer.
Full VOC/SVOC, organochlorine pesticide, and more extensive metal analyses were conducted on three storm water sewer (samples M4281, M4335, and M7183) and one catch basin (sample CB3467) sediment samples. Other than the PCBs, no organochlorines or pesticides were detected in these samples. However, the detection limits for these compounds were greatly elevated in the storm water sewer samples, likely because of the presence of high concentrations of PCBs. It is possible that this analytical interference could mask otherwise detectable amounts of organochlorines or pesticides. Most of the VOC/SVOCs detected were below the corresponding Industrial DCCs. Sample M4335 contained benzo(a)pyrene at 20 ppm (the criterion is 10 ppm), dibenzofuran at 2 ppm (no corresponding criterion due to an insufficient database in this area for this chemical), and p-isopropyltoluene at 0.2 ppm (not included in MDEQ's criteria). The result for dibenzofuran was an estimate (J-qualified). These chemicals are discussed further under the Toxicological Evaluation section of this document. The only metals detected that are not included in MDEQ's criteria were calcium, potassium, silicon, and titanium. These were detected in all four samples and are discussed further under the Toxicological Evaluation section of this document. The remaining metals did not exceed their corresponding criteria.
The MDEQ does not generate criteria to protect residents from adverse health effects that could be caused by dermal contact with sediments. However, the Residential DCC may be adjusted to provide an unofficial screening level to which chemical concentrations in sediment samples can be compared. Residents normally would not be exposed to sediments in the sewer system, but could be exposed to Canal sediments if they should enter the Canal to perform maintenance on their boats or retaining walls. Appendix F shows the steps taken to calculate adjusted DCCs for PCBs and arsenic, one of the RCRA metals detected in Canal sediments at concentrations exceeding its corresponding Residential DCC. (Exposure to the sediments would occur much less frequently than to soils, for which the Residential DCC is derived. Therefore, the adjusted DCC would be higher than the generic Residential DCC, and those chemicals not exceeding their corresponding generic Residential DCC would not exceed their corresponding adjusted DCC.) None of the sediment samples from the Canal exceeded the adjusted Residential DCC for arsenic. However, there were exceedances of the adjusted Residential DCC for PCBs at all depths. Qualitative discussion regarding the concentrations of PCBs in the sediments of the Canal follows in subsequent sections.
Lead also was detected in Canal sediments at concentrations exceeding its Residential DCC. The MDEQ derived the Residential DCC for lead using the Integrated Uptake Exposure Biokinetic (IEUBK) Model for Lead in Children (TRW 1994), rather than the standard mathematical algorithm. The IEUBK Model attempts to predict blood lead concentrations for children exposed to multiple sources of lead in their environment. The level of lead in the body, usually expressed as blood levels, rather than an external dose in mg/kg-day, is used to determine the potential for adverse health effects. The MDEQ Residential DCC for lead is intended to be protective of children's blood lead levels. Because of complexities in and the inflexibility of the IEUBK model when adjusting for exposure frequency, the Residential DCC for lead was not adjusted for this assessment. Rather, qualitative discussion regarding the concentrations of lead in the sediments of the Canal follows in subsequent sections.
The highest sediment concentrations of lead in the Canal were located at the western-most end of the Canal. Sample LRC-S-09 was the eastern-most sample in the north canal that exceeded the criterion, with 470 ppm at the 6-to-12-inch depth. This sample location was about 400 feet east of the sewer outlet. Sample LRC-S-05 was the eastern-most sample in the south canal that exceeded the criterion, with 670 ppm at the 6-to-12-inch depth and 890 ppm at the 12-to-18-inch depth. This sample location was about 400 feet south of the sewer outlet, near where the connecting canal bends to the east. The remaining exceedances occurred between these two sample locations.
The results for the wipe samples taken from the sewers and catch basins (Table 4) were used only qualitatively, to determine the presence of PCBs where water or sediment samples could not be obtained, and were not used quantitatively.
The wipe samples taken from the residence where the homeowner had recently hired a sanitary sewer service company to remove roots from the connection running from the house into the sanitary sewer revealed that PCBs were in the line (data not shown). It is likely that PCB-containing sludge entered the sewer line when the plumbing snake was in reverse gear.
The EPA conducted ambient air sampling in areas near the locations of the highest PCB sediment concentrations in late March and mid-April. The locations were as follow: the intersections of Bon Brae Avenue and E Street; Bon Brae Avenue and F Street; Bon Brae and Harper Avenues; and Lange Avenue at the bridge over the Canal. Background samples were taken near the city offices, near Jefferson Avenue and 11 Mile Road. Analysis was done only for PCBs. The MDEQ does not generate inhalation screening levels for PCBs because of an inadequate database for that chemical in that area. However, ATSDR has set the Cancer Risk Evaluation Guide (CREG) for PCBs in air at 0.01 micrograms per cubic meter (µg/m3; ATSDR 2002a). CREGs are screening levels for carcinogens (cancer-causing chemicals). If the concentration of a carcinogen of interest exceeds its CREG, it does not necessarily mean that exposure to that concentration will result in the development of cancer. Rather, further evaluation of the exposure scenario is necessary to determine implications to public health. Only one of the eight air samples exceeded the CREG for PCBs in air, that taken at the bridge over the Canal on Lange Street, at 0.016 µg/m3. Discussion regarding the concentration of PCBs in the Lange Street air sample follows in subsequent sections.
EPA surveyed the residents along the Canal to determine the properties most likely to have any PCB contamination in the soil based on canal water usage and the concentrations of PCBs in the Canal sediment and water near those properties. Sixteen yards were sampled along Ten Mile Road and Lange and Revere Avenues, including one property west of Jefferson Avenue used as a background sample. Composite samples were taken from the front yard, the back yard, and/or the garden area and analyzed for PCBs and RCRA metals. Only one sample, taken from a back yard (i.e., adjacent to the Canal), had a detectable amount of PCBs, 0.86 ppm, which is below the MDEQ Residential DCC for PCBs (data not shown). Nine of the properties had arsenic concentrations greater than the MDEQ Residential DCC of 7.6 ppm for that metal (data not shown). The highest concentration of arsenic, 81 ppm, was found in a garden. It was subsequently discovered that the previous homeowner had used chromated-copper-arsenate treated wood to enclose the raised-bed garden, which would account for the elevated concentration of arsenic. The next highest arsenic concentration found was 74 ppm, again in a garden.
Discussion with MDEQ revealed that typical background concentrations of arsenic in soils in the eastern part of Michigan are between 18 and 20 ppm (2002, C. Wilson, MDEQ Environmental Response Division Southeast Office, personal communication). The background sample taken by EPA was not analyzed for RCRA metals. If that sample has been archived and can be analyzed for arsenic, or if MDEQ conducts sampling, and the local background concentration of arsenic is determined to be greater than the generic Residential DCC, then the background concentration becomes the clean-up criterion for this site. It is possible that some of the samples that exceeded the generic Residential DCC would not be above a site-specific Residential DCC.
Additional discussion with MDEQ, EPA, and the Macomb County Health Department revealed that a portion of the homes along the Canal are built on fill and that developments like these can experience elevated concentrations of metals in the soil (2002, C. Wilson, MDEQ Environmental Response division Southeast Office, personal communication). For this reason, it is unlikely that watering from the Canal contributed to the elevated levels of arsenic in the soil samples. Nonetheless, the arsenic concentrations will be discussed further in the Toxicological Evaluation section of this document.
Consistent with the Public Health Action Plan recommended in the draft Health Consultation (ATSDR 2002c), MDEQ conducted follow-up soil sampling of residential yards that exceeded the expected background. One yard contained arsenic concentrations at levels of concern, the highest concentration being 74 ppm. MDEQ is continuing its evaluation of these property. The remainder of the yards tested showed arsenic levels below background concentrations.
To determine whether nearby residents are, have been, or are likely to be exposed to contaminants associated with a property, ATSDR and MDCH evaluate the environmental and human components that could lead to human exposure. An exposure pathway contains five elements: (1) a source of contamination, (2) contaminant transport through an environmental medium, (3) a point of exposure, (4) a route of human exposure, and (5) an exposed population. An exposure pathway is considered complete if there is evidence that all five of these elements are, have been, or will be present at the property. Alternatively, an exposure pathway is considered complete if there is a high probability of exposure. It is considered either a potential or an incomplete pathway if there is no evidence that at least one of the elements above are, have been, or will be present at the property, or that there is a lower probability of exposure. The table below shows the exposure pathways expected for the Ten-Mile Drainage System:
|Source||Environmental Transport and Media||Chemicals of Interest||Exposure Point||Exposure Route||Exposed Population||Time Frame||Status|
|Illicit release of PCBs||Sewer water||PCBs, metals, VOCs, SVOCs, pesticides||Storm water sewers and catch basins, sanitary sewers||Dermal absorption, incidental ingestion, inhalation||Utility workers, professional or home-owner drain cleaners||Past||Incomplete|
|Illicit release of PCBs||Canal water||PCBs, metals, VOCs, SVOCs, pesticides||Lange/Revere Canal||Dermal absorption, incidental ingestion, inhalation||Swimmers, residential and visiting boaters||Past||Potential|
|Wahby Pond||Dermal absorption, incidental ingestion, inhalation||Park visitors wading in the pond||Past||Potential|
|Residential surface soils||Dermal absorption, incidental ingestion, inhalation||Gardeners, children playing on bare soil||Past||Potential|
|Garden produce||Ingestion||Consumers of produce grown in yards along the Canal||Past||Potential|
|Fish caught in the Canal||Ingestion||Local anglers||Past||Potential|
|Illicit release of PCBs||Sewer sediment||PCBs, metals, VOCs, SVOCs, pesticides||Storm water sewers and catch basins, sanitary sewers||Dermal absorption, incidental ingestion, inhalation||Utility workers, professional or home-owner drain cleaners||Past||Incomplete|
|Illicit release of PCBs||Canal sediment||PCBs, metals, VOCs, SVOCs, pesticides||Lange/Revere Canal||Dermal absorption, incidental ingestion, inhalation||Residents working on boats, docks, or retaining walls||Past||Potential|
|Wahby Pond (sediment)||Dermal absorption, incidental ingestion, inhalation||Park visitors wading in the pond||Past||Potential|
|Illicit release of PCBs||Air||PCBs, metals, VOCs, SVOCs, pesticides||Ambient air||Inhalation||Ten-Mile/Lange/-Revere Drainage District||Past||Potential|
|NOTE: THE PRESENCE OF AN EXPOSURE PATHWAY IN THIS TABLE DOES NOT IMPLY THAT AN EXPOSURE WOULD BE SUBSTANTIVE OR THAT AN ADVERSE HEALTH EFFECT WOULD OCCUR.|
It is unlikely that utility workers would be exposed to the chemicals in the sewer water if they wear the personal protective equipment required for their work. Hired professional drain cleaners or homeowners who "snake" their own drains also should not be at risk for exposure if they wear rubber gloves during the process. It is likely that such persons would choose to wear protective gloves when working with sanitary sewer lines. It is possible that a person routing a residential drain could inhale vapors from PCBs, VOCs, or SVOCs that might emerge from the drain when the plumbing snake is in reverse gear; however, the duration of that exposure would be minimal compared to that of a utility worker who would regularly be exposed to sewer water. Therefore, exposure to sewer water is considered an incomplete pathway.
Residents have raised concerns about sewer backups and potentially contaminated water and sediment entering their homes through the sanitary sewer lines (2002, C. Shoemaker, Macomb County Health Department, personal communication). Regular routing of drains should prevent backups that might occur due to tree roots penetrating the sewer system. If a basement should become flooded by a sanitary sewer backup, those persons cleaning up the water, whether they are the homeowner or a professional service, would likely be wearing protective equipment such as rubber knee boots and rubber gloves, thus minimizing or eliminating contact with the water. Even if a person were to come into contact with any contaminated water, the exposure would be brief and would not be expected to cause adverse health effects.
Recreational users of the Canal could be exposed to chemicals of interest from swimming in or splashing of the water. Visiting swimmers and boaters would have a lower frequency of exposure than residents in the immediate vicinity who would use the Canal more regularly. The frequency and location of swimming along the Canal are unknown, but MDCH assumed 60 days per year for purposes of adjusting the GCC. Boaters at the western end of the Canal would be traveling at a slow rate of speed because of limited space, and they would not likely be splashed by wake generation. Personal watercraft (jet-ski) or non-motorized boat (e.g., canoe, kayak, or rowboat) users and people in inner tubes can approach the western end of the Canal more easily and therefore might be exposed to elevated levels of PCBs in the water. The Canal is not a drinking water source. Incidental swallowing of Canal water during recreational use of the Canal is not expected to cause adverse health effects.
Wahby Pond, in Wahby Park at the corner of Revere and Jefferson Avenues, is not intended for use as a swimming area, however, children might play at the water's edge. Because PCBs tend to adhere to sediments rather than disperse in water, it is possible that the sample from that pond contained PCB-contaminated suspended solids (sediments) rather than PCBs in the water itself. Although EPA intends to pump and treat the water in the pond (2002, D. Sawicki, EPA START, personal communication), if the sediments contain PCBs, an exposure pathway still could exist. Nonetheless, it is likely that any dermal exposure to and incidental ingestion of PCBs or other, as yet unknown, chemicals of interest in the pond water would be minimal and would not cause adverse health effects. There are decorative fountains in the pond that are currently shut off. It is possible that any PCBs, VOCs, or SVOCs in the pond water could volatilize in the fountain spray, but air concentrations would not be significant because they would disperse quickly in ambient air.
Fish taken from the Canal might have elevated concentrations of PCBs or certain metals or pesticides; however, this would be attributable to historical contamination of the Great Lakes. The 2002 Michigan Family Fish Consumption Guide (MDCH 2002) lists species of fish for which MDCH recommends limited consumption. Several species of fish from Lake St. Clair are listed in the guide (2); however, these advisories cover the entire lake and are not specific to certain areas. The most recent available data on Lake St. Clair fish were gathered in 2000 (MDEQ 2001a). The MDEQ sampled carp, smallmouth bass, and walleye from the lake in 2001, and plans to sample carp and walleye in 2002, but the data are not yet available, nor would they necessarily alter the advisories. The Macomb County Health Department has cautioned against eating fish from the Canal (Appendix C). Some anglers might choose to eat the fish, but if they follow the advisories and prepare their catch in accordance with the Family Fish Consumption Guide, then any potential exposure would be reduced or eliminated.
As discussed for sewer waters, it is unlikely that utility workers would be exposed to the chemicals in the sewer sediments if they wear the personal protective equipment required for their work. Hired professional drain cleaners or homeowners who "snake" their own drains also should not be at risk for exposure if they wear rubber gloves during the process. It is possible that a person routing a residential drain could inhale any PCBs, VOCs, or SVOCs that might emerge from the drain when the plumbing snake is in reverse gear; however, the duration of that exposure would be minimal compared to that of a utility worker who would regularly be exposed to sewer sediments.
As mentioned earlier, residents have raised concerns about sewer backups and potentially contaminated water and sediment entering their homes (2002, C. Shoemaker, Macomb County Health Department, personal communication). Regular routing of drains should prevent backups that might occur as a result of tree roots penetrating the sewer system. If a basement should become flooded by a sanitary sewer backup, those persons cleaning up the water and any sediment, whether they are the homeowner or a professional service, would likely be wearing protective equipment such as rubber knee boots and rubber gloves. Even if a person were to come into contact with any contaminated sediment, the exposure would be brief and would not be expected to cause adverse health effects.
Residents performing maintenance on their boats, docks, or retaining walls might stand in the sediment of the Canal in order to work. A child might assist in this task. If waders are worn, then exposure would be reduced or eliminated. Wearing shoes and long pants would not likely decrease exposure significantly. The possibility of sediment sticking to a person's hands long enough to be unintentionally transferred to the mouth is remote.
Children playing near the edge of Wahby Pond might be exposed to the pond's sediments. The sediments in the pond were not sampled during the investigation. Because PCBs tend to adhere to sediments rather than disperse in water, it is possible that the water sample taken from the pond contained PCB-contaminated suspended solids rather than PCBs in the water itself. Although the EPA intends to pump and treat the water in the pond (2002, D. Sawicki, EPA START, personal communication), if the sediments contain PCBs, then an exposure pathway still would exist. Nonetheless, it is likely that occasional dermal exposure to and incidental ingestion of PCBs or other, as yet unknown, chemicals of interest in the pond sediment would be minimal and would not cause adverse health effects.
The CREG for a chemical in air assumes that a person is exposed continuously. While most residents living near the Canal would likely be away from the area during a portion of the day (e.g., at work or school), some retired citizens or residents who work at home and spend a substantial amount of time in the area could be exposed.
Elevated levels of arsenic were detected in soil samples taken from residential yards and gardens. While it is not likely for a person to be exposed to chemicals of interest in soil under sod, there may be bare areas of dirt such as gardens or play areas where exposure might occur. As well, garden produce might accumulate certain metals in the edible portion of the plant. The yard where samples indicated elevated levels of arsenic in the soil must be better characterized in order to determine any likely exposure scenarios and associated health implications. As stated previously, MDEQ is continuing its investigation of this property.
The potential for adverse health effects that might result from exposure to contaminated media is evaluated by estimating a dose of each chemical of interest. These doses are calculated for scenarios in which individuals might be exposed to (come into contact with) the contaminated media. In order to calculate these doses, assumptions are made about the way people behave; the amount of contaminated media they may ingest, inhale, or make skin contact with; and how long and how frequently they may make contact with the contaminated media. These calculated doses are used along with chemical-specific toxicological information to evaluate the risk of noncancer and cancer health effects.
In order to assess the potential for noncancer health effects, estimated doses are compared to an ATSDR Minimal Risk Level (MRL) or the EPA's oral Reference Dose (RfD). MRLs and RfDs are doses below which noncancer adverse health effects are not expected to occur. They are derived from toxic effect levels obtained from human population and/or occupational studies and laboratory animal studies. Toxic effect levels identified from these studies may be either a NOAEL or LOAEL. Because the NOAEL is the highest dose that does not result in any adverse health effects, this effect level is preferred as the basis for an MRL or an RfD. The LOAEL is the lowest dose at which adverse health effects were seen in a study; it is used when a NOAEL cannot be identified.
Because there is uncertainty in both human and animal studies, NOAELs and LOAELs are divided by "uncertainty factors" to derive the more protective RfD or MRL. These uncertainty factors are generally in multiples of ten, but may sometimes be less, depending on the quality of the study or the seriousness of the observed adverse effect. Given the level of uncertainty in the development of RfDs and MRLs, they should not be considered as a strict line between a safe and an unsafe dose. If a calculated dose exceeds either the RfD or the MRL, it is important to consider the magnitude of the exceedance as well as the uncertainty surrounding the calculated dose before determining if noncancer health effects are likely.
Cancer risk is estimated by calculating a dose and multiplying it by a cancer potency factor, known as the cancer slope factor (CSF). Some CSFs are derived from human population or occupational studies. Most of these studies are of individuals, such as those in occupational groups, who are exposed to higher levels than the general population would be. When no human data are available, CSFs are calculated from data obtained from animal studies in laboratories. The dose of chemical to which animals are exposed in the laboratory is generally far higher than would result from environmental exposures. Use of animal data introduces additional uncertainty into the CSF because of differences in metabolism, life span, and body size between test animals and humans.
For most carcinogens, it is generally thought that an increasingly lower dose will result in a proportionally lower cancer risk. The CSF quantitatively defines this relationship between the dose and the risk of developing cancer. In order to calculate the slope factor, it is necessary to extrapolate high doses from either human or animal studies to lower, more realistic levels of exposure. Extrapolation below the observed dose level introduces uncertainty into the CSF. Cancer risk estimates are, therefore, measures of the chance of developing cancer as a result of exposure to an estimated dose. Cancer risk estimates are generally expressed as the number of individuals in a larger population who may develop cancer (e.g., one in one million). Note that these estimates are for excess cancers that might occur as a result of exposure to chemicals at a site in addition to those cancers that would be expected to occur in an unexposed population. Cancer is a common illness. A population with no known exposure to chemical contaminants could be expected to have a substantial number of cancer cases.
PCBs were detected at various concentrations in water and sediment samples from the sewers and the Canal and in the air. As discussed in the Exposure Pathway section, it is not likely that utility workers or those routing drains would be exposed to the PCBs in either the storm or sanitary sewers. Therefore, this discussion will focus on potential health effects resulting from exposure to PCBs in the Canal and the air.
PCBs are complex mixtures of synthetic organic chemicals with no known natural source. They exist as colorless to light yellow, oily liquids or solids. They have no known smell or taste. Some PCBs are volatile and may exist as a vapor in air. Because they don't burn easily and are good insulating materials, PCBs were used widely as coolants and lubricants in transformers, capacitors, and other electrical equipment. The manufacture of PCBs stopped in the United States in 1977 because there was evidence that the chemicals build up in the environment and may cause harmful effects. Products that may contain PCBs include old fluorescent lighting fixtures, electrical devices or appliances containing PCB capacitors made before PCB use was stopped, old microscope oil, and old hydraulic oil (ATSDR 2000b).
In general, PCBs are relatively insoluble in water. Sediments that contain PCBs can release the PCBs into the surrounding water, but the nature of the chemicals causes them to attach more strongly to soil particles rather than enter the water column. PCBs are taken up into the bodies of small aquatic organisms and fish, especially those fish that are bottom-feeders, and can accumulate through the food chain. They accumulate in the body fat and can enter breast milk. The most likely source of human exposure to PCBs is through the eating of contaminated fish, although PCBs also can be absorbed through the skin and via inhalation (ATSDR 2000b).
Long-term consumption of Great Lakes sport fish has been implicated in behavioral and learning deficits detected in children born to mothers who have eaten the fish (ATSDR 2000b). However, effects seen are not consistent across populations or across specific functions, possibly because of different susceptibilities of different populations, uncertainty about the concentration, rate, and mixture of the PCBs, or other confounders. It should be noted that epidemiological (population) studies such as these show associations rather than causation. Therefore, it cannot be concluded, as yet, that PCBs are the causative agents for the effects seen.
The MRL for chronic (one year or greater) oral exposure to PCBs is 0.02 micrograms per kilogram body weight per day (µg/kg/day). For a child weighing 10 kg, the corresponding protective dose would be 0.2 µg/day. While the concentrations of PCBs in the canal sediment are, for the most part, higher than those in the water, it is unlikely that a child would ingest the sediment itself. Rather, it is more probable that some sediments could be suspended in the water column and be ingested if any canal water were swallowed. The MDEQ Surface Water Quality Division (SWQD) Great Lakes Initiative rules indicate that a person might swallow 30 ml (0.03 liters, about ¼ cup of water) per hour of recreation in a surface water body (2002, D. Bush, MDEQ-SWQD, personal communication). If a 10-kg child swimming in the Canal for one hour were to swallow that volume, the maximum amount of PCBs ingested would be 0.17 µg (0.03 liters x 5.8 µg/L [maximum Canal-water PCB concentration]). This product is slightly below the MRL, which has protection calculated into its value. Therefore, any incidental ingestion of canal water during recreational use of the Canal is not expected, by itself, to cause adverse health effects.
If a 10-kg child were to swallow 30 ml of water from Wahby Pond, the ingested dose would be 1.56 µg (0.03 liters x 52 µg/L), which is greater than the protective dose discussed. However, exposure to the pond water is expected to be minimal and would not be expected to cause adverse health effects.
Some absorption through the skin might occur if a person were to swim or stand in the Canal; however, it is difficult to estimate an absorbed amount. At the lower PCB concentrations found at most sites of environmental contamination, the chemicals tend to adhere to organic materials in the soil and migrate through the skin less easily than pure PCBs or technical-grade PCB mixtures. In order to evaluate the potential for uptake of PCBs from the sediment in the Canal, MDCH reviewed several studies of people who have come into contact with contaminated soil. These studies indicated that people who are dermally exposed to very high soil concentrations of PCBs tend to accumulate very little of the chemicals in their bodies.
In 1982, a Michigan Department of Natural Resources (MDNR) (3) investigation of soil contamination at an industrial site in Lansing, Michigan found up to 10,000 ppm of PCBs in the soil (ATSDR 1988). The Michigan Department of Public Health (MDPH) (4) analyzed blood samples from 10 workers at the company. The workers' blood contained between 7 and 16 ppb PCBs, within the range of values found in numerous epidemiological studies of populations without occupational exposure to PCBs (MDCH 1997a).
In 1986, MDPH learned that some residents of Kalamazoo, Michigan collected worms for fishing bait from a closed paper company landfill where the soil was contaminated with PCBs (up to 64 ppm). The MDPH analyzed samples of nine residents' blood; these samples contained serum PCB levels between non-detect and 14.1 ppb (MDCH 1997b).
In 1986, MDPH became aware that children were playing in the alleys near a Superfund site in Detroit where the soils were heavily contaminated with PCBs (up to 12,000 ppm in ash on the site, up to 8,800 ppm in sewer sediment from near the site [MDPH 1992]). MDPH tested the blood of 193 residents of the neighborhood. These samples contained up to 81 ppb PCBs, with an average of 10.7 ppb (MDPH 1987).
The Indiana State Department of Health has carried out two similar studies. A study in Bloomington, Indiana, where soil PCB concentrations ranged up to 9,000 ppm, found mean serum PCB concentrations of 8.1 ppb for males and 7.8 ppb for females, comparable to those in non-exposed populations (ISDH 1992). At a site in Crawfordsville, Indiana, children who had been playing in soil or sediments containing from 0.2 to 384 ppm PCBs had serum PCB levels ranging from 3 to 9.3 ppb, with an average of 3.4 ppb (ISDH 1997).
These studies indicate that dermal exposure to PCBs in the Canal is not expected, by itself, to result in adverse health effects. Prolonged exposure to high levels of PCBs via ingestion and skin contact, collectively, could result in negative health effects. However, oral and dermal exposure to the PCBs in the Canal would be intermittent and not be expected to cause adverse health effects.
There is not an MRL for PCBs in air; however, the CREG for PCBs in air, discussed earlier, was exceeded by the sample taken at the Lange Street bridge. However, only one data point out of eight samples taken is not sufficient to conclude that adverse health effects would occur. Also, because ambient conditions will cause any vapors to dissipate, it is not likely that any air concentrations of PCBs will be consistently high enough to expect adverse health effects to occur.
Arsenic was detected at levels above the MDEQ Residential DCC in soil samples taken from residential yards along the Canal. The highest level detected by EPA, 81 ppm, was likely attributable to the previous resident's using pressure-treated wood to enclose the garden. Therefore, the next highest level detected, 74 ppm, by MDEQ, was evaluated for potential adverse health effects resulting from exposure to arsenic-contaminated soil.
Arsenic is a naturally occurring element. Inorganic arsenic compounds are mainly used to preserve wood ("pressure-treated" lumber). Organic arsenic compounds are used as pesticides. The organic form of arsenic is considered to be essentially harmless to humans, whereas there is concern in the health community regarding exposure to inorganic arsenic, especially in water. Some nutritional studies indicate that arsenic may be a nutrient essential for good health (ATSDR 2000a).
The MRL for chronic oral exposure to arsenic is 0.0003 mg/kg/day. This equates to a protective dose of 0.003 mg/day for a 10-kg child or 0.021 mg/day for a 70-kg adult. If a child unintentionally eats 200 mg (0.0002 kg) of soil per day, then a soil arsenic concentration of 74 ppm (74 mg/kg) would yield a total of 0.0148 (0.015) mg of arsenic ingested per day for that child, which is five times the protective dose. It should be noted that not all the arsenic in the soil would be absorbed through the walls of the stomach and intestines and enter the child's body. The MDEQ assumes that only half the arsenic in soil will be absorbed, and the actual absorption could be much less. It should also be noted that ATSDR develops MRLs to be very protective; exceeding an MRL does not imply that adverse health effects are expected. If an adult eats 100 mg of soil per day, then a soil arsenic concentration of 74 ppm would yield a total of 0.0074 (0.007) mg of arsenic ingested per day for that adult, which is one-third of the protective dose.
EPA has classified inorganic arsenic as a human carcinogen (EPA 1988). Several studies have shown that ingestion of arsenic in drinking water can increase the risk of lung, bladder, liver, kidney, skin, or prostate cancer. Perhaps the single most common and characteristic sign of oral exposure to inorganic arsenic is the appearance of skin ailments: hyperkeratinization (thickening) of the skin, especially on the palms and soles; formation of multiple hyperkeratinized corns or warts; and hyperpigmentation (darkening, usually a speckled pattern) of the skin with some hypopigmentation (loss of pigmentation). These effects are usually the earliest observable sign of chronic (long-term) exposure to arsenic. Direct dermal contact might cause local irritation and contact dermatitis (a rash). The effects may be mild, but they might progress to papules and vesicles in extreme cases (ATSDR 2000a).
Garden plants might accumulate arsenic by root uptake from the soil, the degree of uptake being affected by the speciation of the arsenic compound. However, even when grown on highly polluted soil or soil naturally high in arsenic, plants have been shown to accumulate comparatively low levels of the metal (ATSDR 2000a). Therefore, any arsenic that might accumulate in produce grown in yards shown to have elevated levels of arsenic is not expected to be at levels that would cause adverse health effects.
Lead was detected at various concentrations in water and sediment samples from the sewers and the Canal. As discussed in the Exposure Pathway section, it is not likely that utility workers or those routing drains would be exposed to lead in either the storm or sanitary sewers. The metal was also detected in soil samples taken from residential yards, but the concentrations found were below the MDEQ Residential DCC. Therefore, this discussion will focus on potential health effects resulting from exposure to lead in the Canal.
There is no EPA RfD or ATSDR Comparison Value for lead; however, the MDEQ Residential Drinking Water Criterion for lead is 4 ppb. This criterion is applied to a person's primary drinking water source. The Canal is not a drinking water source. If a person were to swallow some water unintentionally while working or playing in the Canal, that exposure would be minimal and would not likely result in any health effects.
EPA and the Centers for Disease Control and Prevention (CDC) have determined that childhood blood lead concentrations at or above 10 micrograms per deciliter (µg/dl) present risks to children's health. Blood lead concentrations greater than this level have been associated with developmental delays in learning and cognition (ATSDR 1999). Children who frequently play in or on soil containing concentrations of lead greater than 400 ppm may exhibit blood lead concentrations greater than10 µg/dl. The MDCH Lead Hazard Remediation Program (LHRP) has not found children with elevated blood lead levels in areas of the state with high concentrations of lead in sediments (2002, M. Borgialli, MDCH-LHRP, personal communication). Also, any Canal sediment to which a child might be exposed would likely wash off in the Canal water prior to that child's having the opportunity to transfer the sediment to his or her mouth. Lead is poorly absorbed through the skin. Therefore, it is not expected that exposure to lead in the sediment in the Canal would result in adverse health effects.
Calcium, potassium, silicon, and titanium were found at various concentrations in water and sediment samples from the sewer. However, these compounds are not expected to cause adverse health effects in the Ten Mile Drainage System area since sewer workers would be wearing personal protective equipment and residents do not have access to the sewers.
Benzo(a)pyrene, dibenzofuran, and p-isopropyltoluene were found at various concentrations in sediment samples from the sewer. However, these compounds are not expected to cause adverse health effects in the Ten Mile Drainage System area since sewer workers would be wearing personal protective equipment and residents do not have access to the sewers.
Children may be at greater risk than adults from exposure to hazardous substances at sites of environmental contamination. Children engage in activities such as playing outdoors and hand-to-mouth behaviors that could increase their intake of hazardous substances. They are shorter than most adults, and therefore breathe dust, soil, and vapors closer to the ground. Their lower body weight and higher intake rate results in a greater dose of hazardous substance per unit of body weight. The developing body systems of children can sustain permanent damage if toxic exposures are high enough during critical growth stages. Even before birth, children are forming the body organs they need to last a lifetime. Injury during key periods of growth and development could lead to malformation of organs (teratogenesis), disruption of function, and premature death. Exposure of the mother could lead to exposure of the fetus, via the placenta, or affect the fetus because of injury or illness sustained by the mother (ATSDR 1998). The obvious implication for environmental health is that children can experience substantially greater exposures than adults to toxicants that are present in soil, water, or air.
Children living in the Ten Mile Drainage System area would not be expected to have access to the storm or sanitary sewers and should not be at risk to any chemicals present in those structures. Children in the area may swim in the Canal, but exposure to the chemicals in the Canal would be intermittent. Also, children may have access to Wahby Pond, though that access would be minimal. Children playing in their yards might have contact with arsenic in bare soil; however, it is unclear what areas of the yard may be of concern.
As discussed in the Toxicological Evaluation-PCBs section, long-term consumption of PCB-contaminated fish or marine mammals has been implicated in adverse effects seen in children born to exposed mothers. Any PCBs in fish residing in the Canal may have come from the Canal or from Lake St. Clair. The Michigan Family Fish Consumption Guide indicates which fish in Lake St. Clair to avoid. Following the guide would reduce or eliminate direct or indirect exposure of children to contaminants in fish.
Several meetings and forums were held in St. Clair Shores to provide citizens an opportunity to voice their concerns about the PCB investigation. Any health questions received were addressed immediately. Those questions and others received by MDCH or the Macomb County Health Department before and after the release of the Public Comment Draft Health Consultation are listed and more comprehensively answered in Appendices G and H, respectively. Non-health related questions are being addressed by the appropriate agencies.
The main chemicals of interest in the water samples from the Ten Mile Drainage System and the Canal are PCBs and lead. The other chemicals evaluated (calcium, potassium, silicon, and titanium) do not pose a health hazard primarily because these chemicals were present only in the sewers and exposure is not expected to occur.
The levels of PCBs and lead found in the storm and sanitary sewers and catch basins do not pose an apparent health hazard because only utility workers wearing appropriate personal protective equipment should have access to these areas and would not be exposed. In homes where sanitary drains are cleaned by professional drain cleaners or the homeowner, any chemicals returning up the pipe on the plumbing snake should not pose a health threat because the person cleaning the drain would likely be wearing rubber gloves, at the very least, when performing this job and would not be exposed dermally. Any inhalation exposure occurring in this scenario would be brief and insignificant.
The level of PCBs in the Canal water poses no apparent public health hazard to those persons swimming in the Canal. While combined oral and dermal exposures would increase the total dose of PCBs, the exposures would be infrequent and would not be expected to cause adverse health effects.
The concentration of PCBs in the water of Wahby Pond poses no apparent public health hazard because the likelihood of a child's having regular access to the pond water and sediments is remote.
Any PCBs in fish taken from the Canals could have originated from the contaminated sediments in the Canal or elsewhere in the Great Lakes system, as PCBs are ubiquitous in the environment. Because the fish can enter and leave the Canal at any time, it cannot be determined if or to what extent the contamination of the sediments might have contributed to a fish's contaminant load.
The level of lead in the Canal water poses no apparent health hazard.
The main chemicals of interest in the sediment samples from the Ten Mile Drainage System and the Canal are PCBs and lead. The other chemicals evaluated (benzo(a)pyrene, calcium, dibenzofuran, p-isopropyltoluene, potassium, silicon, and titanium) do not pose a health hazard because these chemicals were present only in the sewers and exposure is not expected to occur.
As discussed for water above, the levels of PCBs and lead found in the sediments of the storm and sanitary sewers and catch basins do not pose an apparent health hazard because only utility workers should have access to these areas and would not be exposed. Similarly, no apparent health hazard exists for those persons cleaning residential sanitary drains.
The concentration of PCBs in the Canal sediments poses no apparent public health hazard. Exposure would be infrequent and would not be expected to cause adverse health effects.
The lead levels in the Canal sediments pose no apparent health hazard. It is not likely that the sediments would adhere to the skin long enough to be transferred to the mouth. Dermal absorption of lead is not likely.
Only one air sample of eight taken exceeded the ATSDR CREG for PCBs. As discussed earlier, one data point is not sufficient to conclude that negative health effects will occur. Therefore, the air concentrations of PCBs pose no apparent health hazard.
The levels of arsenic found in soil samples of a residential yard along the Canal pose an indeterminate health hazard. It is possible that high concentrations are in areas where exposure is not expected to occur.
- The contamination of sediments and water in the storm and sanitary sewers, the Canal, and Wahby Pond should be addressed. At the very least, the sediments in the sewers should be removed to prevent further contamination of the Canal, in order that adverse public health effects do not become possible.
- Discrete soil samples should be collected from residential areas to determine the levels and extent of arsenic contamination.
- To reduce the likelihood of potential exposure, residents should avoid boating, fishing, or swimming in the Canal or using the Canal water for irrigation until the contamination has been addressed. If the regulatory agencies choose to remediate the Canal, disturbing of the sediments should be minimized. After any remediation of the Canal is complete, people fishing in the Canal should follow the advice provided in the Michigan Family Fish Consumption Guide.
- Information regarding the progress of the investigation and any remediation should continue to be shared with the community via the public repository and the City's website, with public meetings or informational forums being conducted as necessary.
- EPA should take measures to address the contamination, such as removing the sediments and treating the water. EPA should coordinate efforts with MDEQ, PWO, and the City of St. Clair Shores. (A removal action was begun August 14, 2002 and completed in April 2003.)
- The MDEQ should continue the Fish Contaminant Monitoring Program and provide the data collected to MDCH so that fish advisories, including that for Lake St. Clair, can be updated as necessary.
- The MDEQ should ascertain whether the soils in yards of homes built along the Canal contain levels of arsenic above the local background. If any levels exceed the local background concentration, MDEQ should address those levels, as mandated by state law. (The MDEQ has completed the first phase of its investigation and is continuing the evaluation of one yard.)
- The Macomb County Health Department and MDCH should continue to provide health-related information to the community regarding the PCBs and other chemicals in the sewers, the Canal, and the soil.
- Several concerned citizens have requested that the health department conduct a health study of people residing next to the affected canals. At the current time, there is no plan for a health study to be performed. While it is likely that persons in the Ten Mile Drainage System area have been exposed to the chemicals of interest, the likely dose, considering exposure frequency and route, is not considered to be sufficient to cause adverse health effects.
If any citizen has additional information or health concerns regarding this health consultation, please contact the Michigan Department of Community Health, Environmental and Occupational Epidemiology Division, at 1-800-648-6942.
Michigan Department of Community Health
Christina Bush, Toxicologist
John Filpus, Environmental Engineer
Robin Freer, Resource Specialist
ATSDR Regional Representative
Regional Services, Region V
Office of the Assistant Administrator
ATSDR Technical Project Officer
Division of Health Assessment and Consultation
Superfund Site Assessment Branch
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1 RCRA metals are arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver.
2 Species of concern in Lake St. Clair are bluegill, brown bullhead, carp, carpsucker, channel catfish, largemouth and smallmouth bass, northern pike, muskellunge, sturgeon, walleye, white bass, and white perch (MDCH 2002). Yellow perch samples have not contained enough of any contaminant to justify issuing an advisory for that species (2002, J. Filpus, MDCH Division of Environmental and Occupation Epidemiology, personal communication).
3 As of October 1, 1995, the environmental protection and regulation functions of the Michigan Department of Natural Resources (MDNR) were transferred to the newly-formed Michigan Department of Environmental Quality (MDEQ).
4 On April 1, 1996, the Michigan Department of Public Health (MDPH) Division of Health Risk Assessment was absorbed into the newly-formed Michigan Department of Community Health (MDCH) and the MDPH Division of Water Supply was transferred to the Michigan Department of Environmental Quality (MDEQ) Division of Drinking Water and Radiological Protection.