Environmental advocates, on the other hand, have called for even stricter rules that would consider a higher risk of cancer from the chemical compound.
The proposed new PRGs are 72 parts per trillion of dioxin for residential land uses and 950 ppt for commercial and industrial land uses. That would lower the allowed levels from 1,000 ppt for residential soil and a range from 5,000-20,000 ppt in commercial and industrial soil.
The Michigan Department of Environmental Quality has considered 90 ppt safe for residential properties, and the figures vary widely across the United States.
The EPA’s new interim levels were developed using estimates for the toxicity of dioxin and generic exposure assumptions, such as the how frequently people come in contact with the chemical.
The Dow Chemical Co. is engaged in an ongoing dioxin investigation in the Tittabawassee River, Saginaw River and Saginaw Bay. The soil in some residential areas along the Tittabawassee exceeds the 72 ppt and 90 ppt levels. Some areas with soil levels above 1,000 ppt have seen cleanup action in recent years.
According to the EPA, the preliminary remediation goals are not meant to act as site-specific cleanup levels but as initial guidelines for use in deciding the scope of characterizing pollution and cleanup options.
In comments filed with the EPA, Dow stated that the agency has ignored recent scientific studies that demonstrate that dioxin levels in human blood have declined and that elevated levels of dioxin in soil do not result in elevated levels of dioxin in blood.
“That’s troublesome to us,” Dow spokeswoman Mary Draves said.
Draves said the EPA relied on outdated science to come up with the new figures and she questioned the timing of the release of the numbers when the EPA is already undergoing a more in-depth review of dioxin.
“It’s out of sequence,” she said. “You’re issuing a report on science you haven’t reviewed yet or made a final decision on.”
Jim Collins, Dow’s director of epidemiology, said the EPA might seek to further restrict levels to 3.7 ppt, which would be below typical background levels found in Michigan that he said are about 7 ppt.
“This would be the most stringent cleanup level in the world,” he said.
The company called on the EPA to withdraw the proposed new figures until the agency implements recommendations from the National Academy of Science expert panel and revises its dioxin reassessment. Among other actions, Dow also wants the EPA to use the best science available to determine if the PRGs are adequately protective.
Local organizations have also shared comments with the EPA. Scott Walker, CEO of Midland Tomorrow, wrote urging the EPA to postpone updating the numbers. He wrote that the economic development group is concerned that the draft numbers would amplify uncertainty in the community, and increase the negative consequences of that uncertainty on economic development and property values in Midland County.
“Midland County communities invest significant resources in attracting and maintaining businesses and especially in supporting small businesses,” Walker wrote. “The draft PRGs will unnecessarily create uncertainty and fear that will depress property values and discourage businesses from setting up shop in Midland County, hindering economic development. This uncertainty and fear arise because the draft PRGs do not clearly explain why a revision is needed at this time or how the public should react to them.”
The Michigan Chamber of Commerce, Midland Area Chamber of Commerce and other groups expressed concerns about the EPA’s approach in joint letter, saying that changes could cause confusion and introduce a de facto standard that has yet to be fully vetted by the scientific community.
“Therefore, EPA’s approach could dramatically create a negative impact upon the economic health of our businesses and communities without enhancing the protection of human health and the environment,” the letter stated.
Midland City Manager Jon Lynch wrote that the dioxin issue is a source of continuous uncertainty for residents.
“Midland residents worry about whether their health is at risk from the dioxin in their neighborhoods, and they fear that dioxin contamination will depress property values and prevent them from selling their homes,” he wrote. “The draft PRGs, like any change to the federal exposure standard or state cleanup criteria, will trigger additional worries for Midland residents and fears of the unknown.”
The city’s top priority is to ensure the health and safety of its population, but the Midland has serious concerns about the draft PRGs and their potential impact on the public, Lynch wrote. He said those concerns include that the draft numbers create unnecessary uncertainty and fear for the public, the numbers do not adequately explain how the new values should be applied to existing and future remedial activities, the timing of the draft PRGs is inconsistent with the transparent process that EPA has promised to communities dealing with dioxin cleanups and some of the factual assumptions underlying the draft PRGs are not sufficiently explained or rationalized in the guidance document.
Nationally, General Electric Co., BASF, Georgia Pacific, U.S. Chamber of Commerce, The Vinyl Institute, Soil Science Society of America, American Forest & Paper Association, Texas Commission on Environmental Quality and other companies and groups have also written with concerns about the changes.
David Fischer, assistant general counsel for the Chlorine Chemistry Division, a business council of the American Chemistry Council, said the PRGs have been used as basis for actual cleanup levels. He said stricter requirements could boost cleanup costs.
“These costs will balloon if EPA finalizes the much lower alternative PRGs,” he said. “Yet recent studies have concluded that there is no connection between dioxin soil levels and intake, meaning there is no more public health benefit to be gained.”
Fischer also said the EPA didn’t use all available science in its decision and should complete its own reassessment of dioxin before setting new levels.
“As we noted in our comments, EPA should abandon the draft interim PRGs,” Fischer said. “At a a minimum, EPA should complete its dioxin reassessment, consistent with the (National Academy of Science) Report, and then evaluate the protectiveness of current PRGs for dioxin in soil. Moreover, EPA should rely on the best available science and fully comport with all applicable EPA and OMB guidelines.”