June 15, 2002
House Government Operations Committee
Re: HB 5963 – Dioxin Cleanup Standard
Dear Committee Members,
Dioxin is the most potent toxic chemical ever tested. It is a known human carcinogen. Tests on animals have result in the growth of tumors in all species tested in both sexes. Therefore, decisions regarding the amount of the chemical that can remain in our communities must be made carefully and in a manner that allows full participation from the scientific community.
Part 201 Cleanup Standards
Cleanup standard in Michigan are risk-based in nature. The amount of any contaminate that may remain in place is based on the future use of the property and exposure assumption derived from that use. The standards set forth in section 20120a(1)(a)-(d) represent cleanups that are derived from generic assumptions. Therefore, a cleanup that meets the cleanup standards for a cleanup under (1)(a) means that that property is approved for unrestricted residential use in the future. In Michigan, the cleanup standard for dioxin in soil is 90 parts per trillion (ppt).
A company can pursue a cleanup that takes into site-specific factors, or includes site-specific exposure assumptions. For example, contaminated groundwater may not have to be addressed if homes in the area use a public water supply, and the discharge of that groundwater into area rivers and streams is predicted not to be a health hazard. In that case, the company would be pursuing a cleanup under section (1)(f). It would allow for residential use, as long as no one drilled new wells into the groundwater.
One problem with the proposed change is that it attempts to replace our current dynamic system, based on risk factors, that is used to address all exposure routes (soil, water and air) with a one number fits all approach (that was derived for use in soil only).
Dioxin Cleanup Standard
The proposed change to the Part 201 standards included in HB 5963 would replace the current system of a health-based analysis with an interim policy guideline prepared by the Agency for Toxic Substances and Disease Registry (ATSDR). The ATSDR was requested in 2001 to do a health assessment of the Tittabawasee River floodplain. That assessment was conducted in cooperation with the Michigan Department of Community Health. That assessment stated:
"The level of total dioxin TEQs detected at concentrations exceeding the ATSDR action level at the Mitigation Site (7,261), the golf course (2,588 ppt), and some areas of the SNWR (1,055 ppt) would pose an urgent public health hazard if people were routinely exposed to soil at these locations." (p.10)
"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 nuerodevelopmental effects observed in the offspring of female rhesus monkeys exposed during pregnancy (ATSDR 1998). 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)."
Petitioned Health Consultation: Dioxin Contamination in the Tittabawasee River Floodplain South of Midland, Michigan (Michigan Department of Community Health, Under a Cooperative Agreement with the Agency for Toxic Substances and Disease Registry (ATSDR)
In practice, the level set by the ATSDR already mimic the Michigan program. The ATSDR states that dioxin levels below 50 ppt would be considered safe. The Michigan program uses a slightly higher 90 ppt. At levels between 50–1000 ppt the ATSDR recommends investigating site-specific factors such as bio-availability, ingestion rates, pathway analysis, soil cover, climate, other contaminants, and background exposures. These are many of the same factors the Michigan Department of Environmental Quality is authorized to take under consideration when approving a limited cleanup under sections (1)(f)-(i).
The Michigan Environmental Council opposes HB 5963 and urges the committee to vote "no". The "action level" proposed as our new cleanup standard is inappropriate. As stated above, this level of exposure would cause an "urgent public health hazard" – not a level considered safe for prolonged public exposure.