For years, environmentalists in Michigan have been pressuring the state to clean up what they say are dangerous levels of dioxin in the soil of Midland, where Dow Chemical Company is headquartered. Dow says there’s no danger and the state has proposed easing dioxin cleanup standards. Meanwhile, the Environmental Protection Agency is expected to soon release its long-awaited report on dioxin’s health hazards, and by most accounts, it will say that dioxin is more dangerous than current regulations assume. Living On Earth’s science editor Diane Toomey reports.
CURWOOD: Welcome to Living on Earth. I'm Steve Curwood. Years ago, soil sampling in Midland, Michigan revealed high levels of dioxin on the grounds of Dow Chemical and in nearby playgrounds and parks. Midland is Dow's world headquarters. And dioxins from its chemical plant came from making such products as saran wrap, Agent Orange, and various pesticides.
Despite the test results, little has been done by Dow or the state of Michigan to clean up these sites. But as the public learns more about dioxin contamination in Midland, a debate is heating up. How much dioxin is too much? Living on Earth's science editor, Diane Toomey, reports.
TOOMEY: Under Michigan law, dioxin soil concentrations greater than 90 parts per trillion may indicate a possible health hazard. Dioxin has been linked to a range of health effects, including cancer and reproductive damage. Many of the soil samples taken in the city of Midland tested above the state's trigger level. But environmentalists complain there was not state follow-up to those results. Regulators say that's not true. They put the onus on Dow to do more research. So the company commissioned a study to look at something called the bioavailability of the dioxin. That means the percentage of the toxin that's actually released from the soil and enters the human body if someone, say a child, ingests it. Jeff Feerer is the senior environmental projects manager for Dow Chemical.
FEERER: We essentially hired a contractor, someone who is a dioxin toxicologist, Dr. Dennis Pastenbach. And, his group essentially built a model, or a simulation, that replicated the conditions inside a human stomach and intestine. And what they found that, lo and behold, only about 25 percent of the dioxin was actually extractable in the conditions of the human stomach.
TOOMEY: This bioavailability study, Dow says, proved to the state that Midland's dioxin problem wasn't serious. Linda Birnbaum is director of the Environmental Protection Agency's Experimental Toxicology Division. A dioxin expert, she reviewed the Dow study.
BIRNBAUM: They used an in-vitro technique to estimate bioavailability. And my concern was that this technique has not yet been validated for dioxin-like compounds. It's been shown to work quite well for some other kinds of chemicals, but not for the dioxins. I was very concerned about that.
TOOMEY: Dow maintains this method replicates the human digestive tract better than any animal experiment, although the company admits this is the first time the test has been used on dioxin. And there are other ways to be exposed to dioxin in soil, including inhalation and absorption through the skin, although Dow also downplays the dangers posed by those pathways.
But a recently released federal health assessment says there's not enough data to determine if the Midland soil poses a health risk. For instance, no backyards in Midland have ever been tested for dioxin. The federal report recommends the state should carry out residential testing. But Dow doesn't agree. Again, Dow spokesperson, Jeff Feerer.
FEERER: Any time you sample residential areas, it's a tremendous upheaval and worry for the residents that are being affected. And, we're still trying to figure out whether this recommendation makes any sense to us, given all the sampling that's been done in Midland. But, think about it, that if someone came to your door and wanted to sample your property for dioxin, is that something that you'd even want to have done? It's not that we're opposed to doing more sampling. It's just that it's not really even scientifically relevant anymore.
TOOMEY: Complicating the Midland situation is a proposal by Michigan's Department of Environmental Quality to raise the dioxin concentration that requires investigation, from 90 to 150 parts per trillion. Ken Silfven is the spokesperson for the department. He says when the state recalculated how much actual soil exposure there is for Michigan residents, it became apparent that the standard should be eased.
SILFVEN: One of the exposure factors was, like if you wear shorts and sleeveless shirts and that nine months out of the year, in Michigan that just is not a reality. So I think some of those types of inputs were being adjusted.
TOOMEY: Silfven acknowledges that staff at the Department of Environmental Quality voiced descent about the change. In one email, a state toxicologist writes, "The more I think about it, the more uncomfortable I get." Nevertheless, the department went ahead with the proposal.
DEFUR: I think it's a most peculiar time to do it.
TOOMEY: Peter Defur is a professor of environmental studies at Virginia Commonwealth University. He says any changes in state regulation should wait for an impending report from the Environmental Protection Agency. The so-called dioxin reassessment has been more than a decade in the making, and could likely alter the regulatory landscape for dioxin. Defur co-chaired an outside panel that reviewed the report.
DEFUR: The conclusions are that dioxin is more carcinogenic than we had previously believed. That each one of us in the United States carries a body burden that is greater than EPA would consider to be safe. That the non-cancer effects are at least, if not more, problematic than are the cancer effects. None of these are captured in current regulations and in the way we set our current standards.
BIRNBAUM: Dioxin might be thought of as another lead.
TOOMEY: EPA toxicologist Linda Birnbaum says dioxin's most insidious effects include learning disabilities and IQ and immune system suppression that may arise from prenatal exposure.
BIRNBAUM: We believe that the most sensitive organism to the effects of dioxin is the developing embryo or fetus. And partially, it's because dioxin appears to interfere with very key developmental processes. And the kinds of effects at background levels that we're looking for are not things that are going to be picked up in a visit to the pediatrician.
TOOMEY: Peter Defur says the comparison of dioxin to lead is an analogy that can be carried into the area of regulation.
DEFUR: It means that EPA will now have to face a couple of policy decisions that are rare. And the first one is how you deal with a contaminant that covers the entire United States. The other policy problem EPA is going to have is addressing the cleanup of contaminated sites. They would be undertaking a massive effort.
TOOMEY: Given that the release of the EPA's final dioxin reassessment is already long overdue, there's no guarantee it will be made public this summer, as is now expected. For now, states have a wide berth when setting their dioxin standards and dealing with contaminated sites.
Michigan regulators are currently evaluating public comments received on its proposal to ease its dioxin standard. And as for the city of Midland, those same regulators say they've yet to determine a timeframe for sampling of residential areas near the Dow site. For Living on Earth, I'm Diane Toomey.
here for Part 1 of the Dioxin story on last week's show (Story #1 on "Saginaw").">
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