HEALTH CONSULTATION
Tittabawassee River Floodplain Dioxin Contamination
TITTABAWASSEE RIVER
MIDLAND, MIDLAND COUNTY, MICHIGAN
A Midland resident and two Michigan-based environmental organizations petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a public health assessment of dioxin and dioxin-like compound (DLC) contamination in Midland, Michigan, and adjacent communities. The present public health consultation addresses floodplain soil contamination in the Tittabawassee River watershed downstream from the city of Midland. A draft of this health assessment was released for public comment. The data necessary to determine if DLC-contaminated floodplain soil in the Tittabawassee River watershed poses a public health risk are not available; therefore, the site poses an indeterminate public health hazard.
DLCs were detected at concentrations exceeding the ATSDR action level for residential soils (1 part per billion dioxin toxic equivalents) at several locations in the floodplain near the confluence of the Tittabawassee and Saginaw Rivers. Additional soil sampling is necessary to determine if nearby residential properties are similarly contaminated with DLCs.
A soil sampling study conducted by the Michigan Department of Environmental Quality (MDEQ) indicates that floodplain soil in Tittabawassee River watershed near and upstream of the confluence of the Tittabawassee and Saginaw Rivers is contaminated with DLCs. These data, along with DLC levels detected in fish, indicate that DLC contamination may be widespread throughout the Tittabawassee River watershed below Midland. Additional soil sampling is necessary to determine the extent and severity of DLC contamination in these areas.
The Michigan Department of Community Health (MDCH) recommends that the MDEQ implement sampling plans to determine if DLC contamination is present in the Tittabawassee River watershed between the city of Midland and the confluence of the Tittabawassee and Saginaw Rivers. MDCH specifically recommends soil sampling at residential properties in closest proximity to previously identified areas of concern. These plans should include contingencies for potential public health actions if DLCs are detected at concentrations greater than the ATSDR action level, and a comprehensive evaluation of site-specific exposure factors if DLCs are found at concentrations greater than the ATSDR screening level. The MDCH will request ATSDR collaboration and support for health education and an Exposure Assessment for affected communities if indicated by the results of soil studies.
PURPOSE AND STATEMENT OF HEALTH ISSUES
On May 1, 2001, a Midland resident and two Michigan-based environmental organizations petitioned the federal Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a public health assessment of DLC contamination in communities adjacent to Midland, Michigan, where contamination originating from the Midland area has been "transported...via air and water" (Attachment A). The petitioners stated that the "likely source of this contamination is the Dow Chemical Company" (Petitioners for the Dow Midland site 2001). The petitioners specifically noted that DLC contamination found in fish in the Tittabawassee River below Midland has been and continues to be chronically high.
ATSDR and the Michigan Department of Community Health (MDCH) have a cooperative agreement for conducting assessments and consultations for potential health hazards at sites of environmental contamination within the state of Michigan. On July 30, 2001, MDCH staff and a representative from the ATSDR Region 5 office visited the Midland area and toured both the Tittabawassee River floodplain and the Dow Chemical Company (Dow) plant site. The MDCH completed a "Petition Scoping Report" and provided the information obtained from these activities to ATSDR on August 31, 2001. A copy of the report is provided in Attachment B. MDCH met with the petitioners on October 3, 2001, to discuss the health assessment process and to provide an opportunity for exchange of additional information.
ATSDR responded in writing (Attachment C) to the petitioners on November 2, 2001, stating that, "After reviewing the public health issues and community concerns about potential DLC contamination and the Dow Midland facility, ATSDR has found a reasonable basis to prepare public health consultations to address the concerns associated with the Dow facility"(ATSDR 2001). MDCH has agreed to prepare these public health consultations. ATSDR will review MDCH's work and provide technical support as needed.
The present consultation addresses concerns related to DLC contamination found in soil samples taken from the floodplain of the Tittabawassee River below Midland. Additional consultations for Midland and affected adjacent communities that address other contaminated media may be developed in the future with the ultimate goal of providing a full multimedia, multipathway public health assessment.
The Dow Chemical Company, founded in 1897, operates a chemical manufacturing plant in the city of Midland, Michigan. The Dow plant encompasses approximately 1,900 acres on the southern perimeter of the city (Figure 1). The Tittabawassee River forms the southern boundary of the plant site and flows east to the Saginaw Bay of Lake Huron.
Chemicals that have been produced at the Dow plant include: styrene, butadiene, picric acid,
mustard gas, Saran Wrap, Styrofoam, Agent Orange, and various other chemicals including
chlorpyrifos (i.e., Dursban) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Chlorophenol
production began in 1915. Wastes generated from this process were initially disposed of in 600
acres of on-site waste ponds. During high flow periods in the early 1900s, wastes from these ponds
would be intentionally released to the Tittabawassee River (Brandt 1997). Dow currently operates
its own on-site wastewater treatment plant 
.
In 1986, the State of Michigan experienced a significant flood event that incapacitated the Dow wastewater treatment plant and flooded areas of the plant where soils were contaminated with DLCs. Run-off from 10 feet of floodwaters overwhelmed containment systems, overflowed dikes, and entered the river (Wilkerson 1986). Untreated or partially treated chemical wastes entered the Tittabawassee River before plant operations were shut down (Schmidt 1986). Chemical odors associated with the Dow plant were noticed 7 miles downstream from the Dow plant site.
DLC Contamination in Floodplain Soil
In April 2000, soil samples were collected under the direction of the Michigan Department of Environmental Quality (MDEQ) in an area near the confluence of the Tittabawassee and Saginaw Rivers (Figure 2) as part of a wetland mitigation project (MDEQ 2001a). This project was required by the United States Army Corps of Engineers to replace the shallow water habitat that would be lost through implementation of proposed fill and containment response activities at a site of environmental contamination located downstream on the Saginaw River in Bay City.
Soil samples were collected by the responsible party to ensure that the selected mitigation site on the
north side of the Tittabawassee River did not contain contaminant concentrations that would pose
an unacceptable risk to terrestrial and aquatic organisms that would be expected to inhabit the new
wetland resource. A sampling grid was established over the entire sample area, and surface soil was
composited from nine locations located from within each grid area. At the request of the MDEQ,
two of the composite samples were randomly selected for DLC analysis and concentrations of 1,474
and 2,199 parts per trillion (ppt) total dioxin toxicity equivalents (see box) were detected (Table 1).
Table 1. Total Dioxin Toxic Equivalent (TEQ) Concentrations Detected in Soil Samples Collected from the Mitigation Site
| Soil Samples Location | Date Sampled | Number of Samples | Range of TEQ Detected (ppt) | DEQ Residential Cleanup Criterion (ppt) | ATSDR Screening Level (ppt) | ATSDR Action Level (ppt) |
| Mitigation Site Composite Samples | April 2000 | 9 | 1,474 - 2,199 | 90 | 50 | 1,000 |
| Mitigation Site Discrete Samples | Dec. 2000 | 5 | 338 - 7,261 | 90 | 50 | 1,000 |
De Rosa et al. 1997a ; MDEQ 2000, 2001a.
No immediate local source could be identified to explain the presence of the high concentrations of DLCs at the mitigation site. The only known upstream source of significant concentrations of DLCs is the Dow plant in the city of Midland, approximately 20 miles upstream of the mitigation site.
To further define the extent and level of DLC contamination, the MDEQ developed a Phase I soil sampling program to achieve the following:
In December 2000, MDEQ staff collected and analyzed five discrete surface soil samples from the mitigation site. Concentrations of DLCs ranged from 338 to 7,261 ppt total dioxin TEQs (Table 1). These data confirmed the previous composite sample results and also indicated that DLC contamination was present throughout mitigation site soils at concentrations exceeding the MDEQ Residential Cleanup Criterion.
Based on the sampling results for the mitigation site, three upstream locations were selected to assess whether other areas of the Tittabawassee River floodplain in the near vicinity contained DLCs (Figure 2):
Four discrete surface soil samples were collected near the site of environmental contamination upstream of the mitigation site, two were collected upstream of the site from an adjacent farm field and two downstream from an adjacent golf course. All sample results identified total dioxin TEQ concentrations above the MDEQ Residential Cleanup Criterion of 90 ppt (Table 2).
Table 2. Total Dioxin TEQ Concentrations Detected in Soil Samples Collected in the Tittabawassee River Floodplain Upstream from the Mitigation Site.
| Soil Samples Location | Date Sampled | Range of TEQ Detected (ppt) | Number of Samples | DEQ Residential Cleanup Criterion (ppt) | ATSDR Screening Level (ppt) | ATSDR Action Level (ppt) |
| Farm field | May 2001 | 180 - 424 | 2 | 90 | 50 | 1,000 |
|
|
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| Golf course | May 2001 | 2,529 - 2,588 | 2 | 90 | 50 | 1,000 |
|
|
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| SNWR Forested Area | May 2001 | 10 | 90 | 50 | 1,000 | |
| < 6 inches | 35 - 134 | 90 | 50 | 1,000 | ||
| < 12 inches | 57 - 1,055 | 90 | 50 | 1,000 | ||
|
|
||||||
| SNWR Upland Area | June 2001 | 15 | 90 | 50 | 1,000 | |
| 0-3 inches | 386 - 765 | 90 | 50 | 1,000 | ||
| 3-6 inches | 424 - 663 | 90 | 50 | 1,000 | ||
| 12-15 inches | 58 - 275 | 90 | 50 | 1,000 | ||
De Rosa et al. 1997a ; MDEQ 2000, 2001a.
Five locations were sampled at two depths from within the forested area of the SNWR. Sample depths varied somewhat from one location to another due to root mass, leaf litter, and other location-specific factors. Five of the 10 samples contained total dioxin TEQ concentrations above the MDEQ Residential Cleanup Criterion (Table 2).
Five locations were sampled at three depths from within the SNWR Upland Area. Samples were collected from the 0-3 inch, 3-6 inch, and 12-15 inch soil strata. The five sampling locations were selected from the higher ground elevations found within the open upland area. Thirteen of the 15 samples contained total dioxin TEQ concentrations above the MDEQ Residential Cleanup Criterion (Table 2).
Based upon the soil sampling results described above, the MDEQ proposed a Phase II sampling plan in October 2001 (MDEQ 2001b). Phase II soil samples were collected from three locations within the 12-mile stretch of the Tittabawassee River located between the city of Freeland and Center Road in Saginaw Township (Figure 3). The selected sampling locations were Freeland Festival Park, Imerman Park, and West Michigan Park. The Freeland Festival Park is located approximately 7 miles downstream of the city of Midland and is operated by the community of Tittabawassee Township. Imerman Park is located 4˝ miles downstream of the Freeland Festival Park. Imerman Park is a large, heavily utilized park that is operated by Saginaw County. West Michigan Park is operated by the community of Saginaw Township and is located just over 6 miles downstream of Imerman Park and approximately 4 miles upstream of the confluence of the Tittabawassee and Saginaw Rivers. The objectives of the Phase II sampling program were to:
The Phase II sampling plan has been implemented (Phase II sampling data will be discussed in a future health consultation). More data are necessary to determine if floodplain soils throughout the Tittabawassee River floodplain pose a public health risk. No additional information concerning DLC concentrations in the Tittabawassee River floodplain is available at this time.
The Tittabawassee River flows southeast from Midland to the confluence of the Saginaw and Shiawassee Rivers near the mitigation site. From there, the Saginaw River flows northeast to the Saginaw Bay of Lake Huron. The MDCH has issued fish advisories for the Tittabawassee River below Midland based on detected levels of DLCs and polychlorinated biphenyls (PCBs). The advisories recommend no consumption of carp, channel catfish, or white bass, and limited consumption of smallmouth bass and all other species (one meal per week for the general population and one meal per month for children and women of childbearing age). Similar advisories have been issued for the Saginaw River. Advisories for the Saginaw Bay recommend no consumption of carp and channel catfish based on detected DLC levels. The advisory for Lake Huron, based on detected DLC levels, recommends that women of childbearing age and children limit consumption of rainbow and steelhead trout to one meal per month, smaller whitefish (less than 18 inches in length) to one meal per week, and recommends no consumption of larger whitefish (MDCH 2001).
To determine whether people are or could be exposed to contaminants associated with a property, ATSDR and MDCH evaluate the environmental and human components that lead to human exposure. An exposure pathway contains five major 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) a receptor population. An exposure pathway is considered a complete pathway if there is evidence that all five of these elements are, have been, or will be present at the property.
Table 3. Exposure Pathway for DLC-Contaminated Soil in the Tittabawassee River Floodplain
| Source | Environmental Transport and Media | Chemicals of Concern | Exposure Point | Exposure Route | Exposed Population | Time Frame | Status |
| The Dow Chemical Company, Midland | Deposition of river sediments in the Tittabawassee River Floodplain | Chlorinated Dioxins and Furans | Soil in residential yards, farm fields, and public access sites | Incidental ingestion, Dermal contact, Inhalation |
Residents in the Tittabawassee Floodplain, farmers, recreational visitors | Past | Complete |
| Current | Complete | ||||||
| Future | Complete |
The MDEQ Phase I sampling program has conclusively shown that elevated levels of total dioxin TEQ concentrations are present in the Tittabawassee River floodplain near the confluence with the Saginaw River. Human use of the floodplain increases upstream of the Phase I sampling area. Numerous residential properties are located within the floodplain. The majority located in the city of Shields and in Saginaw Township, but are also scattered along the stretch of the river. Some agricultural operations are also located within the floodplain and as are several public parks.
The likely source of these contaminants is chemical manufacturing activities at the Dow plant site in Midland. The likely mechanism of transport is deposition of contaminated river sediments in the Tittabawassee River floodplain. People living within the floodplain, farmers, and recreation users of the Tittabawassee River could be exposed to dioxins and furans in floodplain soil through incidental ingestion, direct dermal contact, and inhalation of soil and dust. Chlorinated dioxins and furans are very persistent in soil, therefore, exposure is likely to have occurred in the past and will continue in the absence of any remedial action.
Human use of the Tittabawassee River floodplain increases upstream of the Phase I sample area. Numerous residential properties are located within the floodplain, the majority being within the communities of Shields and Saginaw Township. Of particular concern are approximately 12 homes located adjacent to the river less than half a mile upstream from the mitigation site where total dioxin TEQs were detected at concentrations up to 7,261 ppt. Agricultural operations also occur within the floodplain as well as a variety of public recreational facilities including parks, boat launches, and public access sites.
Health Effects
Dioxins and dioxin-like compounds are a group of over 210 chlorinated chemicals with similar structures and chemical properties. This group of chemicals, which includes chlorinated dioxins, furans, and some polychlorinated biphenyls, is often referred to collectively as simply "dioxins" or "dioxin-like compounds (DLCs)." When found in the environment, DLCs are usually a mixture of several of these chemicals. DLCs are not intentionally produced and have no known use. Not all DLCs have the same toxicity or ability to cause illness and adverse health effects. However, it is assumed that dioxins and dioxin-like compounds cause adverse health effects through a similar biological mechanism of action. Further, the available science indicates that the health effects resulting from exposure to multiple dioxin-like compounds are additive.
The most toxic chemical in the group is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Toxic equivalency factors (TEF) have been developed to compare the relative toxicity of other dioxins and dioxin-like compounds to that of 2,3,7,8-TCDD. The levels of other dioxin-like compounds measured in the environment are multiplied by a TEF to produce a 2,3,7,8-TCDD toxic equivalent or TEQ concentration. The resulting TEQs for all dioxin-like compounds measured in a sample are then added together to determine the total dioxin TEQ concentration for that sample.
People who have been exposed to high levels of DLCs (such as those found in an industrial setting or due to a significant industrial explosion) have developed chloracne, a skin disease with severe acne-like pimples. Chloracne can persist for years, sometimes clearing only to recur several years later. Changes in blood and urine that may indicate liver damage have also been seen in some people. Exposure to these high concentrations of DLCs may cause long-term alterations in glucose (blood sugar) metabolism and slight changes in hormone levels (ATSDR 1998).
Exposure to lower levels of DLCs in laboratory animals has resulted in a wide variety of adverse health effects, such as cancer, liver damage, and disruption of the endocrine system. In many species of animals, DLCs weaken the immune system and cause a decrease in the system's ability to fight infection. In other animal studies, exposure to DLCs has caused reproductive damage and birth defects. Some animal species, including monkeys, exposed to DLCs during pregnancy had miscarriages. The offspring of animals exposed to DLCs during pregnancy often had birth defects including skeletal deformities, kidney defects, weakened immune responses, and neurodevelopmental effects (ATSDR 1998).
It is not known whether people exposed to low levels of DLCs will experience the same health effects seen in animal studies. However, based on the available information, DLCs are believed to have the potential to cause a wide range of adverse effects in humans, including cancer. The U.S. Environmental Protection Agency (EPA) (EPA 2000) has characterized the mixture of DLCs to which people are commonly exposed as "likely human carcinogens." The EPA has also characterized 2,3,7,8-TCDD as a "human carcinogen" (EPA 2000). The U.S. Department of Health and Human Services, National Toxicology Program 9th Report on Carcinogens (NTP 2001) lists 2,3,7,8-TCDD as a substance "known to be a human carcinogen."
ATSDR Interim Guidance
Because of the potential for adverse health effects in human populations exposed to environmental levels of DLCs, the ATSDR has developed interim policy guidelines to assist health assessors in identifying soil concentrations of potential concern (Attachments D and E). The guidelines recommend the tiered approach shown in the table below to evaluate DLC concentrations in soil.
Table 4. ATSDR's Decision Framework for Sites Contaminated with Dioxin and Dioxin-Like Compounds.
| Screening Level
< 50 ppt TEQs |
Evaluation Level
> 50 ppt but < 1,000 ppt TEQs |
Action Level
> 1,000 ppt TEQs |
| Health effects are unlikely and further evaluation is not necessary, unless there are community health concerns. | Evaluation of site-specific factors, such as
|
Potential public health actions considered, such as
|
(De Rosa et al. 1997a)
The screening level of 50 ppt total dioxin TEQ is the environmental media evaluation guide (EMEG) for 2,3,7,8-TCDD. The EMEG was developed from the ATSDR minimum risk level (MRL) based on neurodevelopmental effects observed in the offspring of female rhesus monkeys exposed during pregnancy (ATSDR 1998). EMEGs are very conservative and protective values. Generally, if soil concentrations do not exceed the EMEG, ATSDR assumes that exposure is not likely to result in adverse health effects. However, if soil concentrations exceed the EMEG, this does not mean that adverse human health effects will always occur. Instead, soil concentrations greater than 50 ppt total dioxin TEQ indicate further site-specific evaluation is necessary (De Rosa et al. 1997a).
The action level of 1,000 ppt TEQ is a concentration of DLCs in residential soil at which various actions may be considered to prevent or limit exposure. The action level is based on the analysis by Kimbrough et al. (1984) of the carcinogenic potential of 2,3,7,8-TCDD. ATSDR recommends that the action level for residential soil be used in full consideration of site-specific factors that may affect total exposure to DLCs through all media and exposure pathways (De Rosa et al. 1997b).
ATSDR recommends that the action level be compared with the "maximum concentrations identified at the site" (De Rosa et al. 1997b). Residential soil levels were not available for this health consultation. However, total dioxin TEQ concentrations greater than 1,000 ppt have been detected at several locations in the Tittabawassee River floodplain including: the mitigation site (up to 7,261 ppt), an upstream golf course (up to 2,588 ppt), and the forested area of the SNWR (up to 1,055 ppt). MDCH has taken a conservative approach of using ATSDR's residential action level as a comparison for these non-residential areas.
Soil concentrations of dioxin TEQs that fall between the screening level and the action level warrant further site-specific study (De Rosa et al. 1997b). Many factors, such as those shown in the table above, can affect how much DLC people are exposed to, how much is absorbed into the body, and whether or not adverse health effects will result. All of the soil samples collected from the mitigation site, the upstream golf course and farm field, the upland area of the SNWR, and some of the samples from the SNWR forested area fall within 50 and 1,000 ppt.
Background Exposure to DLCs
An important consideration when evaluating DLC levels in soil is the level of exposure from all sources of DLCs, or the "background exposure." People can be exposed to DLCs from many sources other than contaminated soil. The general population is mainly exposed to DLCs through their diet by eating plants and animals that contain DLCs. People who live near or work at hazardous waste sites containing DLCs, waste incinerators, or manufacturing facilities that produce DLCs as a by-product may have additional DLC exposures beyond their diet. When people are exposed to and absorb DLCs, they are stored in fatty body tissues where they may persist for months or years. The half-life (the time needed for the body to rid itself of half the contaminants absorbed) for DLCs in humans is 5 to 14 years. Because they remain for a long time, DLCs accumulate in the body and can cause health effects long after exposures have ended. The amount of DLCs accumulated over time is referred to as the "body burden." The best available science suggests that body burden levels of DLCs are closely associated with the likelihood of health effects. Therefore, many scientists recommend comparing DLC body burden levels in at-risk populations with those associated with health effects observed in animal and human studies (EPA 2000, De Rosa et al. 1997b).
Because people may be exposed to DLCs from a variety of sources, and because all these exposures contribute to the body burden of DLCs accumulated over time, ATSDR recommends evaluation of the contribution of soil exposures to total exposures from all sources (De Rosa et al. 1997b). Evaluation of soil exposures would require sufficient knowledge of DLC concentrations in soil, bioavailability of DLCs in site soils, and human behaviors that can affect exposures. Additionally, evaluation of all other sources of DLC exposure would be required to evaluate the incremental contribution of soil exposures to the total body burden of DLCs in the at-risk population. This information is not currently available for residents, farmers, and recreational users of the Tittabawassee River floodplain area.
Community Involvement
This document was released for public comment in March 2002. The comment period lasted for 90 days. A public meeting was held to solicit comments. The comments that were received during the comment period are addressed in Attachment F.
ATSDR Child Health Considerations
Children may be at greater risk than adults from certain kinds of exposure to hazardous substances at sites of environmental contamination. They engage in activities such as playing outdoors and hand-to-mouth behaviors that increase their exposure to hazardous substances. They are shorter than adults, which means they breathe dust, soil, and vapors close to the ground. Their lower body weight and higher intake rate result 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. Prenatal exposures and those that occur in the first few years of life are more likely to cause permanent damage.
Fetuses, infants, and children may be especially sensitive to DLC exposure because of their rapid growth and development. In animal studies, exposure to DLCs has caused reproductive damage and birth defects. Some animal species exposed to DLCs during pregnancy had miscarriages. The offspring of animals exposed to DLCs during pregnancy often had birth defects including skeletal deformities, kidney defects, weakened immune responses, and neurodevelopmental effects (ATSDR 1998).
Evaluation of all other sources of DLC exposure would be required to evaluate the incremental contribution of soil exposures to the total body burden of DLCs in the at-risk population. The data necessary to determine if floodplain soil throughout the Tittabawassee River floodplain poses a public health risk are not available; therefore, the site poses an indeterminate public health hazard. ATSDR classifies sites of environmental contamination into the indeterminate category when the data to make a final decision are lacking.
The levels of total dioxin TEQs detected at concentrations exceeding the ATSDR residential action level at the mitigation site (7,261 ppt), the golf course (2,588 ppt), and some areas of the SNWR (1,055 ppt) might pose a public health hazard if these levels are widespread and people are routinely exposed to soil at these levels at residential locations. The level of exposure on these properties is currently not known. In addition, soil sampling is necessary to determine if nearby residential properties are contaminated with DLCs.
The results of the MDEQ Phase I sampling study indicate that floodplain soil samples collected from the confluence of the Tittabawassee and Saginaw Rivers at the mitigation site, the upstream golf course and farm field, and the forested and upland areas of the SNWR are contaminated with DLCs. These data, along with DLC levels detected in fish, indicate that DLC contamination may be widespread throughout the Tittabawassee River watershed below Midland. Additional soil sampling is necessary to determine the extent and severity of DLC contamination.
If any citizen has additional information or health concerns regarding the Tittabawassee River Floodplain consultation or the Dow Chemical Company Midland petitioned health assessment, please contact the Michigan Department of Community Health, Division of Environmental and Occupational Epidemiology at 1-800-648-6942.
ATSDR (Agency for Toxic Substances and Disease Registry). 1998. Toxicological Profile for Chlorinated Dibenzo-p-Dioxins. December 1998.
ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Letter to Petitioners for Dow Midland site dated November 2, 2001.
Brandt, E. N., 1997. Growth Company: Dow Chemical's First Century, Michigan State University Press, East Lansing, MI.
De Rosa, Christopher T. et al. 1997a. Dioxin and Dioxin-Like Compounds in Soil, Part 1: ATSDR Interim Policy Guideline. Toxicology and Industrial Health, Vol. 13, No. 6, 1997. pages 759-768.
De Rosa, Christopher T. et al. 1997b. Dioxin and Dioxin-Like Compounds in Soil, Part 2: Technical Support Document for ATSDR Interim Policy Guideline. Toxicology and Industrial Health, Vol. 13, No. 6, 1997. pages 769-804.
EPA (United States Environmental Protection Agency). 2000. Draft Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. September 2000.
MDCH (Michigan Department of Community Health). 2001. Michigan 2001 Fish Advisory.
MDEQ (Michigan Department of Environmental Quality). 2000. Part 201 Generic Cleanup Criteria Tables. June 7, 2000.
MDEQ (Michigan Department of Environmental Quality), Environmental Response Division. 2001a. Unpublished: Greenpoint - Tittabawassee River Dioxin Study Area, Phase I Sampling Study Report. October 2001.
MDEQ (Michigan Department of Environmental Quality), Environmental Response Division. 2001b. Unpublished: Greenpoint - Tittabawassee River Dioxin Study Area Phase II Sampling Program. October 2001.
NTP (National Toxicology Program). 2001. 9th Report on Carcinogens. U.S. Department of Health and Human Services. Public Health Service. January 2001.
Petitioners for Dow Midland site. 2001. Petition letter to ATSDR. May 1, 2001.
Schmidt, Wayne. Pollution rising to dangerous levels, experts say. Bay City Times. September 13, 1986.
U. S. Census Bureau (United States Census Bureau). 1990. Census of Population and Housing.
Wilkerson, Isabel. 1986. Tainting of Fish Feared After Michigan Floods. The New York Times. September 23, 1986.
Figure 2. Phase I Sampling Locations
Figure 3. Phase II Sampling Locations
Michigan Department of Community Health
Linda D. Dykema, Ph.D.
Toxicologist, Principal Investigator
Robin Freer, M.S.
Geographic Information System Specialist
ATSDR Regional Representative
Mark Johnson
Office of Regional Operations, Region V
ATSDR Technical Project Officer
Alan W. Yarbrough
Division of Health Assessment and Consultation
Superfund Site Assessment Branch
This Tittabawassee River Floodplain Health Consultation was prepared by the Michigan Department of Community Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.
Alan W. Yarbrough
Technical Project Officer, CAT, SSAB, DHAC, ATSDR
The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.
Sven E. Rodenbeck
for Roberta Erlwein
Chief, Cooperative Agreement Team, SSAB, DHAC, ATSDR
ATTACHMENT A: PETITION LETTER TO ATSDR DATED MAY 1, 2001
Click here to view Attachment A in PDF format (PDF, 2.7MB)
ATTACHMENT B: PETITION SCOPING REPORT FOR DOW CHEMICAL COMPANY MIDLAND
Click here to view Attachment B in PDF format (PDF, 2.7MB)
ATTACHMENT C: ATSDR LETTER TO PETITIONERS FOR DOW MIDLAND SITE DATED NOVEMBER 2, 2001
Click here to view Attachment C in PDF format (PDF, 2.7MB)
ATTACHMENT D: DIOXIN AND DIOXIN-LIKE COMPOUNDS IN SOIL, PART 1: ATSDR INTERIM POLICY GUIDELINE
Click here to view Attachment D in PDF format (PDF, 2.7MB)
ATTACHMENT E: DIOXIN AND DIOXIN-LIKE COMPOUNDS IN SOIL, PART 2: TECHNICAL SUPPORT DOCUMENT FOR ATSDR INTERIM POLICY GUIDELINE
Click here to view Attachment E in PDF format (PDF, 2.7MB)
ATTACHMENT F: RESPONSE TO PUBLIC COMMENT SUMMARY
Responsiveness Summary
MDCH provided an initial 60-day comment period that was extended an additional 30 days at the request of several commenters. The comment period closed on June 14, 2002. Comments received after this date will not be addressed here.
Some commenters expressed concerns related to comments made by other individuals, companies, or organizations. These comments are not germane to the public health consultation and will not be addressed further here.
Several commenters provided journal articles, research papers, and other reference materials, and the MDCH thanks the contributors for this information.
1. Comment: We are in support of and encourage the MDCH and the MDEQ to move forward with the recommendations contained in the petition, assess the health of the community with a properly designed survey, and collect soil samples in accordance with the Phase II sampling plan.
Response: The MDCH with the assistance of the ATSDR is developing a protocol for an Exposure Investigation (EI) in the Tittabawassee River flood plain. When this protocol is sufficiently developed, the draft will be shared with citizens, local government agencies, and other State of Michigan agencies. Recommendations for a "health study" - an epidemiological study of disease rates among people living in the flood plain or other similar assessment - will be considered after the results of the EI are known.
The MDEQ has completed Phase II soil sampling and has issued a report of the findings. These results will be discussed in a future health consultation.
2. Comment: The survey design for the health assessment should be forwarded to the Saginaw County Department of Public Health (SCDPH) for review and comment before implementing the survey.
Response: See response #1 above.
3. Comment: The sampling strategy should be forwarded to the SCDPH for review and comment.
Response: The MDEQ is responsible for developing sampling strategies. SCDPH should make this request to the MDEQ.
4. Comment: The identification of the study population should be forwarded to the SCDPH for review and comment.
Response: See response #1 above.
5. Comment: Provide a timeline on the health assessment survey.
Response: See response #1 above.
6. Comment: Notify the SCDPH before any contact is made with the study population, media, public officials, or others and before an information relative to the survey results, whether a preliminary or final report is released to the petitioners, study population, media, public officials or others.
Response: The SCDPH will be kept informed of the progress of any studies conducted in the Tittabawassee River flood plain. However, the SCDPH may not always receive this information before other stakeholders. For example, the property owners whose property has been sampled are entitled to receive information without undue delay.
7. Comment: Collect "control" samples to identify potential sources of dioxins in the Flint, Saginaw, and Shiawassee Rivers. These samples may identify (or eliminate) pesticide application, manufacturing processes, or other activities that could have elevated the levels of dioxin along the floodplain of the Tittabawassee River. Provide a timeline on the Phase II sampling.
Response: The MDEQ has conducted extensive sampling in their Phase II Floodplain Sampling Program and these results have been disseminated to the public. A comprehensive report was available in 2003. The MDCH will produce a revised public health consultation based on these new data.
8. Comment: Notify the SCDPH before the collection of soil samples occur, before contact is made with the media, public officials, or others regarding the collection of the soil samples, and before any information relative to the sample results, whether preliminary or final report, is released to the petitioners, study population, media, public officials or others.
Response: Requests regarding notification about soil sampling should be directed to the MDEQ as the agency responsible for sampling.
9. Comment: Why were the public meetings scheduled in Saginaw for May 1st and Midland for May 2nd cancelled for unknown reasons?
Response: MDCH had some difficulty identifying an available and appropriate location to hold a public meeting in Saginaw. When a location was identified, MDCH postponed the meeting for a few days to allow the public adequate notification time.
10. Comment: How can we determine the number of Multiple Sclerosis (MS) cases reported in the area of dioxin contamination?
Response: Diseases like MS are very difficult to study. MS is insidious in onset, difficult to diagnose, and chronic but not usually fatal. There are no registries of MS sufferers as there are for cancer or birth defects: therefore, cases are not reported. While there are some crude MS prevalence estimates at the regional and national levels, there are no existing registries that would enable us to easily estimate the prevalence of cases among people living in the Tittabawassee River flood plain.
11. Comment: Could the Thomas Township wells that supplied water to the township before Saginaw water became available have become contaminated?
Response: It is unlikely that these wells were contaminated. Dioxin binds tightly to soil and is almost insoluble in water unless there is an organic solvent present. The MDEQ has conducted well water sampling at several locations with the flood plain and has not detected dioxin concentrations above federal drinking water standards in any well. In most of the well water samples, no dioxins were detected.
12. Comment: Could dioxin contamination have had an effect on public health before the Labor Day flood in 1980s?
Response: It cannot be known with certainty what levels of total dioxin TEQs were present in the flood plain soils in the 1980s or what health effects could have resulted from exposure to historical levels. However, it now appears that repetitive annual flooding, rather than a single flood event, is responsible for depositing dioxin-contaminated sediments on the upland areas. The MDEQ has found elevated levels of dioxin 3 and 4 feet below the current ground surface and, in many cases, levels increase in deeper samples.
13. Comment: Can dioxin contribute to or cause multiple sclerosis?
Response: The MDCH is not aware of any literature or study suggesting a link between dioxin exposure and multiple sclerosis.
14. Comment: In 1985 the EPA said the Tittabawassee fish had the highest national levels of dioxins in fish. What are the current levels? What is the risk?
Response: In general, the levels of dioxin in fish taken from the Tittabawassee are declining. Further studies are ongoing and will be made public when the results are available. In the interim, follow the recommendations in the Michigan Fish Advisory for consumption of sport-caught fish.
15. Comment: Given the known pollution of the Pine River (upstream from the Tittabawassee and Dow), would it not be essential to sample upstream to fairly establish the effect of Dow's Midland plant?
Response: The MDEQ has conducted this sampling, and a comprehensive report of the findings was available in 2003. MDCH will discuss this data in a future health consultation.
16. Comment: Your own stated health action criteria were met at the outset with the results of the Phase I tests and have been ignored (4 of 5 samples exceeded the action level criteria of 1,000 ppt). How can this be explained?
Response: The State of Michigan criterion has not been ignored; however, further investigation is needed before the extent of contamination and the public hazard can be determined. MDCH remains committed to work with the MDEQ and other stakeholders to address the situation through appropriate public health actions.
17. Comment: Did DEQ issue directives or guidelines on the Phase 1 or Phase 2 testing in this matter? If so, what were they?
Response: The MDEQ is the lead agency on Phase I and II sampling and directs all these investigation efforts. MDCH provides technical support upon request.
18. Comment: Who was informed of the Phase 1 tests results and when?
Response: This question should be directed to the MDEQ. The MDCH became aware of the Phase I test results in December 2000.
19. Comment: When was Michigan's 90 ppt residential clean-up standard established and by whom?
Response: The 90 ppt standard was calculated by the MDEQ in 1995 when all the cleanup criteria were revised consistent with amendments to Part 201 of the Natural Resources and Environmental Protection Act, Act 451 of 1994, as amended. MDEQ standard exposure assumptions used for all chemicals, and the cancer slope factor developed by the U.S. EPA for dioxin were used to derive the 90 ppt value.
20. Comment: Has that 90 ppt standard been changed, is it currently under review, and if so what is the review process? On what basis can the 90 ppt be changed?
Response: The MDEQ has decided to maintain the 90 ppt criterion pending finalization of the U.S. EPA Dioxin Reassessment. When this document is final, the MDEQ will incorporate new toxicity information into the criterion.
21. Comment: Given the 20 or so soil samples taken in 2001 as part of the Taylor and McCabe Baseline Characterization of Saginaw Bay Watershed Sediments, shouldn't these be used to supplement the Phase I test results?
Response: The results of the MDEQ Saginaw Bay Watershed Sediment Study will be incorporated into future health consultations
22. Comment: Do all mammals have essentially the same dioxin uptake receptors?
Response: All vertebrates (animals with backbones) including mammals have aryl hydrocarbon (Ah) cellular receptors that bind dioxins. When vertebrate animals absorb dioxin into their bodies, the dioxin is believed to bind to the Ah receptor and set off a series of cellular events that could lead to adverse health effects. The effects that can result from activation of the Ah receptor vary significantly from one animal species to another. It is important to remember that human beings are animals too; and while humans may not be as sensitive to dioxin as some other species, there is no evidence to suggest that humans are insensitive to these effects.
23. Comment: What is the highest known level of dioxin found in a human (where, when)?
Response: One individual, a 30-year old woman believed to be intentionally poisoned with dioxin, showed concentrations of 2,3,7,8-TCDD of 144,000 picogram per gram of blood lipids upon admission to a hospital at the University of Vienna. This person experienced severe chloracne that covered her entire body. Besides chloracne, the patient had experienced gastrointestinal symptoms including nausea, vomiting, epigastric pain, loss of appetite, and had not menstruated since she had started a new job at a textile research facility in 1997.
24. Comment: Does a baby "inherit" its mother's dioxin level? If so, would it be through the blood supply as well as through breast milk?
Response: Babies are exposed to dioxin before birth if the mother has elevated levels of dioxin in her blood stream. Dioxin will accumulate in the baby's body just as it does in the mother, although the rate of elimination could be higher due to the baby's more rapid metabolism. Research in laboratory animals and in human populations suggests that the prenatal period (i.e., before birth) is the most sensitive time for dioxin exposure. Babies are also exposed to dioxin if they are breast-fed and dioxin intake at this time can make a significant concentration to a child's body burden of dioxin.
25. Comment: I want to register my support of the Michigan Department of Community Health's efforts to further assess the health affects of dioxin contamination in …affected areas along the Tittabawassee River.
Response: The comment is gratefully noted.
26. Comment: The data in the draft consultation from the confluence must be supplemented by data from the full Saginaw River watershed and evaluated by considering all that data.
Response: MDCH agrees that data from the Saginaw River watershed must be acquired and evaluated to determine the full impact of dioxin contamination on both the Tittabawassee River flood plain and that of the Saginaw River. MDCH is aware of the other potential sources of contamination in the watershed and supports MDEQ's efforts to fully characterize the source of the dioxin contamination. These data will be evaluated in subsequent documents.
27. Comment: Data on health effects likely to be experienced by residents of Midland and downriver areas are generally not reliably collected or not collected at all (with the exception of genital malformations). Most would be impossible to measure at the clinical level and are only measurable at the population level. Yet they represent the most important risk to area residents.
Response: MDCH agrees with the comment and will consider ways to acquire the necessary data to assess these health effects.
28. Comment: Levels of dioxin in indoor dust must be considered as part of the health consultation.
Response: MDCH agrees and is compiling information to conduct dust sampling.
29. Comment: Both the ATSDR and the MDCH have a role to play in accurate characterizations of the public health issues raised by contamination of the Midland and downstream areas, as with any public health concern. We strongly urge ATSDR and MDCH to provide accurate public communications to the community about dioxin and its hazards.
Response: MDCH agrees and, along with the MDEQ, is taking a proactive approach to community involvement.
30. Comment: ATSDR 1 ppb standard is flawed. The level, derived more than 15 years ago, has been referred to as a policy-based level, rather than a risk or health-based level. The number does not incorporate the newest synthesis of dioxin science in the dioxin reassessment.
Response: ATSDR does not set standards but does set media specific comparison values to assist in evaluation of hazardous waste sites and releases. These comparison values identify those contaminants for which further evaluation is performed. This consists of a more detailed examination of exposure pathways and available toxicological information. Based on the results of these evaluations, recommendations are made for public health actions and appropriate remedial actions, but again, these recommendations depend upon exposure-specific considerations.
ATSDR's Policy Guidance on Dioxin in Soil concludes that "the action level of 1 ppb (TEQ) for dioxin and dioxin-like compounds, when coupled to a site-specific context of evaluation for the range >50 ppt to < 1 ppb TEQs in residential soils, is protective of public health and continues to represent a level at which consideration of health action to interdict exposure, including cleanup should occur." While ATSDR is aware of the scientific debate over the health-related impacts of low level non-occupational exposures to dioxin and dioxin-related compounds, based on our experience at other sites, we find ATSDR's action level for residential soils to be protective of public health. These guidelines are applicable only to scenarios involving human exposure via direct ingestion of dioxin-contaminated soils in residential areas and are not appropriate for other exposure scenarios.
31. Comment: Michigan residential and industrial soil cleanup levels compared with some EPA Regions are not protective.
Response: The authority to develop Michigan clean up criteria rests with the MDEQ. MDCH will forward this comment to the appropriate MDEQ staff.
32. Comment: Midland and downriver soils are significantly elevated compared to state and national averages.
Response: MDCH concurs with this comment.
33. Comment: No reviews of the epidemiological data have been conducted for the potentially most exposed population along the Tittabawassee and Saginaw Rivers.
Response: MDCH concurs with this comment and is considering methods to conduct such a review. The public will be asked to participate in planning any such data review.
34. Comment: It has been suggested that dioxin congeners found downriver indicate dioxin-contaminated PCBs as the source.
Response: During Phase II sampling, the MDEQ initially analyzed soil samples for PCBs. It soon became apparent that PCBs were present in only very low concentrations and contributed very little to the total dioxin-like toxicity of the samples. PCB analysis was discontinued on later samples. However, if biomedical sampling of the human population is conducted in the future, these samples will be analyzed for the co-planar PCBs to determine the contribution of these compounds to the total dioxin-like toxicity.
35. Comment: Wildlife data must be considered in the health consultation, as often this data provides important information about extent of the contamination, historical trends, and potential health effects in humans.
Response: The MDCH concurs with the comment. The MDEQ is conducting an ecological study of the flood plain, and this information will be incorporated into future consultations.
36. Comment: Area residents may have elevated rates of PCB's in their bodies because of major PCB contamination in the Saginaw area.
Response: The MDCH concurs with the comment. Please see the response to Comment 34 above.
37. Comment: In order to be complete and accurate, all dioxin-like compounds must be considered when assessing potential health impacts, not only those likely to be present in the general population, but also those specific to this region.
Response: The MDCH concurs with the comment. Please see the response to Comment 34 above.
38. Comment: Numerous reports have surfaced from surgeons, pediatricians, and other health professionals about the anomalous health effects from Midland area residents. One report from a surgeon in Saginaw suggested more surgery for cleft palate (associated with dioxin exposure) in the area than he had ever encountered in a practice that spanned a number of regions.
Response: The MDCH will be following up on these reports as part of the on going public health assessment process.
39. Comment: We urge biological sampling of wildlife and humans to determine if area residents have elevated levels of dioxin.
Response: The MDCH in collaboration with the MDEQ is developing plans for biological sampling in both wildlife and human populations. This information will be presented in future health consultations.
40. Comment: If biological sampling reveals elevated levels of dioxin, further public health interventions should be considered.
Response: Comment noted. The MDCH welcomes suggestions for specific health actions in the flood plain.
41. Comment: Conduct soil, water, sediment, and indoor dust sampling (and water where relevant.
Response: The MDEQ is developing plans to further characterize the contamination in the Tittabawassee and Saginaw River watersheds. The MDCH continues to participate in these planning efforts to ensure that the data acquired is useful for public health assessment.
42. Comment: Dramatically improve availability and monitoring of health data for humans and wildlife. A comprehensive, community approved new monitoring system should be set up to collect data on relevant health effects for the Midland and downriver communities. A special form should be designed for health practitioners specific to this region to collect data.
Response: The comment is noted. Such a monitoring system may be considered as MDCH and ATSDR progress through the public health assessment process.
43. Comment: A comprehensive, community-approved wildlife and farm animal monitoring plan should also be put in place.
Response: As stated above in Comment 35, the MDEQ is conducting an ecological assessment of the Tittabawassee River flood plain. The Michigan Department of Agriculture is responsible for monitoring farm animals and has conducted some limited testing of farm products in the area.
44. Comment: Develop proactive public education plan and materials.
Response: Comment noted. The MDCH is developing such a plan.
45. Comment: I do not think enough is being done to let the public know about health risks associated with dioxin.
Response: See the response to Comment 44 above
46. Comment: Is there not a cumulative effect of dioxin?
Response: Yes, dioxin accumulates in the body if exposure is on going. Dioxin is stored in fatty tissues and is only slowly eliminated from the body. After even a single high exposure, dioxin will persist in the body for many years.
47. Comment: The meeting held on May 13, 2002, at Swan Valley High School was a sham! What a cover up!
Response: Comment noted.
48. Comment: I ran a day care in my home. How safe are these children and my children? I have almost 2 acres and we are flooded many times a year. Also, in the flood of '86, my home was flooded. How safe are we in our home?
Response: It is not possible to answer this question with the limited data currently available. This is why the MDCH and the ATSDR have recommended further study in the Tittabawassee River flood plain and a comprehensive exposure investigation that includes all potentially contaminated media and routes of exposure. In order to help prevent possible exposures, prudent public health practices should be followed such as washing one's hands before eating, removing shoes when coming indoors, and maintaining a grass cover throughout the yard.
