The Michigan Environmental Science Board (MESB) has released its review of the new national ambient air quality standards (NAAQS) for ozone and particulate matter (PM) recently promulgated by the United States Environmental Protection Agency (EPA) (For a more detailed description of the new NAAQS, see Michigan Environmental Compliance Update, September 1997, at 2). The MSB was formed in 1992 to advise the Governor and state agencies on matters affecting the protection and management of Michigan's environment and natural resources. In December, 1996, Governor Engler directed the MESB to review the scientific assumptions, interpretations and conclusions of the studies that served as the basis of the new NAAQS. The report, entitled "Evaluation of Air Quality and Human Health Scientific Issues Involving Particulate Matter and Ozone," which is generally critical of the new NAAQS, culminates seven months of review and analysis of the new NAAQS by the MESB.
The MESB report contains several major findings and conclusions, which include the following:
- Although most epidemiological studies that examined the health effects of air pollution containing PM found an association between measures of PM and heart and lung disease, the lack of information about the mechanism by which PM damages the lungs and the lack of information showing a reduction of adverse health effects when PM levels are reduced raises doubts as to whether PM is the cause of the harmful health effects that have been observed.
- The exposure scenarios used in laboratory animal studies that have been conducted to date on the effects of PM on health do not closely resemble human exposures and, therefore, do not support the hypothesis that ambient PM levels in air in the United States are producing toxic effects in humans.
- There is insufficient ambient air monitoring data and data correlating ambient air measurements to actual personal exposure to PM to justify a new PM standard.
- Although the MESB concludes that there are significant, adverse human health effects associated with increases in air pollution in general, the exact causes of these adverse effects are not known. In particular, the MESB noted that there is uncertainty whether the type of PM regulated under the new PM NAAQS is the cause of the reported adverse health effects. In this respect, the MESB noted that the EPA Clean Air Scientific Advisory Committee was divided over the issue of a causal relationship between PM and mortality.
- The MESB recognized that the current data indicate there is no threshold concentration for ozone below which no adverse effects would be expected. However, the MESB found that the supposed reduction in health risks associated with EPA's new ozone standard is so small as not to be statistically significant. Therefore, the MESB concluded that the selection of the new ozone NAAQS appears to be a policy decision, rather than a decision based solely on scientific data.
- The MESB also found that a claim by the Natural Resource Defense Council (NRDC) that PM concentrations in the United States cause 64,000 premature deaths each year is unreliable because of a statistical error in the NRDC calculation and the uncertainty of a causal relation between PM exposure and mortality.
A minority report that is less critical of the new NAAQS was also included in the MESB report. A complete copy of the MESB report and appendices is available on the Internet at www.great-lakes.net/partners/mesb/pubs.
This article was prepared by S. Lee Johnson, a partner in our Environmental Department, and previously appeared in the October 1997 edition of Michigan Environmental Compliance, a monthly newsletter written by Honigman Miller Schwartz and Cohn on environmental regulatory developments in Michigan and published by M. Lee Smith Publishers. To subscribe, contact the publisher by either phone at 1-800-274-6675; email at custserv@mleesmith.com; the internet at http://www.mleesmith.com; or by mail at M. Lee Smith Publishers LLC, 5201 Virginia Way, P.O. Box 5094, Brentwood, TN 37024-5094.