March 12, 2004 REVISED
Mr. Karl Tomion
333 West Ellsworth Street
Midland, Michigan 48640
Dear Mr. Tomion:
Thank you for taking the time out of your busy schedule on February 12, 2004, to meet with me to discuss the city of Midland’s concern pertaining to actions that are required by The Dow Chemical Company (Dow) to fulfill their obligations under corrective action. The purpose of this letter, in part, is to confirm that a meeting has been scheduled between Midland representatives and Department of Environmental Quality (DEQ) staff for March 23, 2004, at 3:30 p.m., in the Great Lakes conference room, 6th floor, South Tower of Constitution Hall, Lansing. This meeting is intended to provide the city of Midland with an opportunity to comment on the scopes of work and proposed interim response actions.
When we met, most of your concern appeared to be centered on the use of Michigan’s generic residential direct contact criteria (DCC) for dioxin of 90 parts per trillion (ppt) that has been promulgated in rules pursuant to Part 201, Environmental Remediation, of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended. In particular you raised concerns as that number relates to a value that has been identified by the Agency for Toxic Substances and Disease Registry (ATSDR).
I would like to share with you the following information pertaining to the 90 ppt standard. The current, promulgated Part 201 residential DCC for dioxin is based on toxicity information and exposure assumptions that existed as of 1995. A decision was made by the previous DEQ administration to postpone updating the dioxin criteria until the U.S. Environmental Protection Agency (U.S. EPA) completes their dioxin reassessment. The U.S. EPA has been in the process of reassessing dioxin risk for over ten years. The draft U.S. EPA reassessment document has gone through two peer review processes and federal interagency review, and based on our latest information is headed to the National Academy of Sciences for review.
The additional information available since 1995 in the scientific literature indicates that an updated toxicity assessment would include the following information:
Let me also touch on the confusion surrounding the ATSDR action level. In 1997, the ATSDR issued an interim policy guideline for dioxin and dioxin-like compounds in soil. This interim policy guideline includes three categories: a screening level of 50 ppt, an evaluation range of 50 to 1,000 ppt, and an action level of 1,000 ppt. All levels are presented as Toxicity Equivalents (TEQ) of 2,3,7,8-TCDD. An action level is defined as: "A concentration of chemicals at which consideration of action to interdict/prevent exposure occurs, such as surveillance, research, health studies, community education, physician education, or exposure investigations." Alternatively, based on the evaluation by the health assessor, none of these actions may be necessary. Soil concentrations between 50 and 1,000 ppt warrant a site-specific evaluation with consideration given to the following factors: bioavailability, ingestion rates; pathway analysis; soil cover; climate; other contaminants; community concerns; demographics; and background exposures. The guideline concludes: "The ATSDR concludes that the action level of 1,000 ppt for dioxin and dioxin-like compounds, when coupled to a site-specific context of evaluation for the range > 50 ppt to < 1,000 ppt TEQs in residential soil, is protective of public health and continues to represent a level at which consideration of health action to interdict exposure, including cleanup, should occur."
The ATSDR action level for dioxin was originally developed by the Centers for Disease Control and Prevention (CDC) in reaction to a release of dioxin in Times Beach, Missouri. The action level appears to have been strongly influenced by the analytical capabilities of the time. An evaluation of the risk associated with 1,000 ppt dioxin in soil was conducted and published in 1984 by Renate Kimbrough, et al. This evaluation indicated that exposure to this level in soil would exceed the calculated virtually safe dose for 1 in 1,000,000 and 1 in 100,000 cancer risk for residential areas. The report concludes that "in residential areas, levels at or above 1,000 ppt of dioxin in soil cannot be considered safe and represent a level of concern."
Although the more recent ATSDR guideline concludes that the 1,000 ppt action level is still protective, that determination was made on the basis of it being an action level combined with a site-specific evaluation. Based on this, use of the ATSDR action level of 1,000 ppt as a cleanup criterion is inappropriate. This level was never intended to represent a concentration in soil that is acceptable for long-term, residential exposure without any further type of evaluation. As a result, the action level does not satisfy the statutory requirements of Part 201 cleanup criteria pursuant to §324.20120a(4).
On April 13, 1998, the U.S. EPA also issued OSWER Directive 9200.4-26, entitled "Approach for Addressing Dioxin in Soil at CERCLA and RCRA Sites." This directive recommends using 1,000 ppt as a starting point for setting cleanup levels at CERCLA andRCRA sites pending the release of the U.S. EPA dioxin reassessment and an evaluation of how the reassessment impacts various programs at the U.S. EPA and other agencies. The directive adds that these levels are recommended "unless … a more stringent state requirement applies at RCRA sites." The usual caveats are also provided indicating that the directive "cannot impose legally-binding requirements on EPA, states, or the regulated community, and may not apply to a particular situation based upon the circumstances."
Finally, it may help to place the 90 ppt in context if we consider other state dioxin standards. Some states have begun the process of establishing new criteria for cleanups that are associated with the direct contact with soil contaminated with dioxin. For example, the states of Arizona (3.8 ppt), Florida (7.0 ppt), Massachusetts (4.0 ppt), Oregon (3.9 ppt), and Washington (6.7 ppt) have all established residential DCC that are less than the number currently promulgated for Michigan. Upon the release of the dioxin reassessment, it is likely that additional states will revise their cleanup criteria to reflect the most current information. The above states continue to maintain a one-in-one million risk criteria, so in reality their criteria are one-tenth of the number identified in Michigan rule. Michigan, in 1995, went to a one-in-one hundred thousand risk standard which generated the 90 ppt generic residential DCC. In other words, to be equivalent to Michigan’s one-in-one hundred thousand risk standard, Arizona’s dioxin standard would be 38 ppt, Florida’s dioxin standard would be 70 ppt, Massachusetts’ dioxin standard would be 40 ppt, Oregon’s dioxin standard would be 39 ppt, and Washington’s dioxin standard would be 67 ppt.
At the same time DEQ does acknowledge that these criteria are intended to be generic in nature and that a site-specific risk assessment can be conducted to establish alternative criteria for residential soil cleanups. Site-specific criteria are proposed to be established by Dow to address the known releases in Midland as well as the Tittabawassee River flood plain, however, to prepare an alternative, additional information on soils will be needed.
In sum, let me assure you that the basis for the corrective actions that are required for Dow to maintain their operating license are based upon sound science and supported by the U.S. EPA, Region 5. I hope that this has been responsive to some of your concerns, and I look forward to working with the city of Midland to achieve our common mission of protecting the health and safety of all Michigan residents.
Steven E. Chester
cc: Mr. Tom Phillips, Miller Canfield Paddock and Stone PLC
Mr. Jim Lancaster, Miller Canfield Paddock and Stone PLC
Mr. Ron Waybrant, FTCH
Mr. Jim Sygo, Deputy Director, DEQ
Mr. George Bruchmann, DEQ
Mr. Andrew Hogarth, DEQ