Dear Representative Koetje:
I am writing to comment on a proposal to change Michigan's soil dioxin criterion for unrestricted use of residential properties from 90 ppt to 1000 ppt. Such a change would be unwise. It would violate basic principles of public health and disregard what is known and unknown about the toxicity of dioxin.
Various commentators have compared Michigan's standard of 90 ppt to the Centers for Disease Control threshold of 1000 ppt as apples to apples. They are not. Michiganís 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 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 using inappropriate comparisons of Federal and state thresholds as a basis for changing the state soil criterion. These numbers, which serve two different purposes, are aids to understanding the magnitude of contamination and its likelihood of causing human health effects. The legislature would do the community a disservice by attempting to minimize the significance of contamination of the community by adjusting the ruler against which it is measured.
If, however, advocates of a higher state threshold are arguing that 1000 ppt IS protective of public health in properties for unrestricted residential use, their case should be subject to review by an appropriately constituted scientific body. I am familiar with the derivation of the 90 ppt standard and arguments that it is too low. Virtually all of those arguments are based on flawed assumptions, assumptions about which there is substantial disagreement, or data that cannot be generalized.
Midland and downstream residents must have their health and economic interests protected. Those interests are not protected by the contemplated legislative action. I would appreciate it if you would share these comments with your committee.
Ted Schettler MD, MPH (firstname.lastname@example.org)
Department of Internal Medicine
Boston Medical Center
Science and Environmental Health Network