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Differing dioxin standards have differing purposes

By Dr. Ted Schettler and Dr. Peter OrrisMy View Column, Saginaw News, July 18, 2004

We have followed the recent controversy surrounding dioxin contamination of Midland and the Tittabawassee River flood plain with concern and a sense of déjà vu.  In the early 1990s, after contaminating Maine rivers and wildlife with dioxin for years, pulp and paper companies adopted tactics similar to those that Dow Chemical Co. is using today. Then they argued that there was no evidence of harm and that dioxin was not as toxic as previously thought. Today Dow argues that there is no evidence of harm and that the state threshold criterion for soil dioxin, 90 ppt, is too low. Those arguments deserve a response, but not before acknowledging that Dow has, regrettably, contaminated its home community and an extensive downstream watershed with hazardous amounts of dioxin-a potent toxic chemical that causes cancer, neurodevelopmental disorders, and problems in the immune, reproductive, and endocrine systems at extremely low levels of exposure.

Much of the recent controversy centers on Michigan's 90 parts per trillion (ppt) standard vs. the Federal 1000 ppt threshold for dioxin concentrations in soil. Various commentators have compared these as apples to apples. They are not. Michigan's 90 ppt soil criterion for dioxin is a level that is meant to be protective of public health in properties for unrestricted residential use. It is generally consistent with similar criteria in many other states. The Federal 1000 ppt threshold serves a very different purpose. It is a level at which there is significant concern about health effects.  In fact, the lead Federal agency for public health research and education, the Centers for Disease Control, advises that soil levels exceeding 50 ppt should be a cause of concern, necessitating a more thorough analysis.

Further, State and Federal criteria restrict their focus to cancer as the outcome of concern, though we now know that other health effects occur at lower levels of exposure and may affect the entire population.  In fact, due to the array of low-level effects, scientists today are uncertain about the threshold amount of dioxin that may begin to cause or contribute to illness in people. Moreover, dioxin-related health effects are often "hidden" in the general burden of disease and disability in the community. Trying to identify them as "caused by dioxin" is a fruitless task.

The important issues here should not be obscured by inappropriate comparisons of Federal and state criteria. These numbers, which serve two different purposes, are merely aids to understanding the magnitude of contamination and its likelihood of causing human health effects. Dow does the community a disservice by attempting to minimize the significance of their toxic contamination of the community by adjusting the ruler against which it is measured. That sleight of hand does nothing to protect public health.

It may be disruptive for owners if their property is labeled a "facility" when soil levels of dioxin exceed 90 ppt, but no one should be deceived into thinking that the problem goes away by changing some numbers. The world already knows that Midland and the downstream watershed are contaminated with Dow's dioxin. As this story unfolds, residents should be very careful to protect their own health and economic interests, and not forego remedies that will likely be welcome, including, but not limited to, access to clean up.

Ted Schettler MD, MPH Department of Internal Medicine, Boston Medical Center, Boston, MA And Science Director, Science and Environmental Health Network

Peter Orris MD, MPH Professor of Environmental and Occupational Health Sciences University of Illinois School of Public Health., Chicago, IL

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