[ RadSafe ] Ecological Dose-Response Studies

[Otto Raabe]

February 8, 2007

The EPA in association with BEIR VI has rejected the detailed ecological 
studies of Bernard Cohen that showed people living in regions with higher 
radon levels in air in homes tended to have lower lung cancer rates and 
demonstrating that the LNT model does not apply.

In ecological studies the concentration of a potential toxicant is measured 
in general areas where people are being exposed, but no information is 
available about the actual dose to or exposure of any particular person. 
Comparisons are made of rates of disease in people who live in areas with 
different pollutant levels.  Because the actual level of exposure of the 
people with disease is not really known, statisticians tend to give little 
weight to the results of ecological studies. Also, unknown confounders can 
badly skew the results.

Ironically, EPA has a different view for air pollutants, For about ten 
years ecological studies of air pollutants, especially particulate matter, 
have been used to show an association between concentrations in outdoor air 
and diseases in people. Often the affected people are in hospitals 
breathing clean air and the measurements of pollutants are made outdoors 
many miles away. In today's news a study from the University of Washington 
involving 65,893 women who were presumably exposed to some extent or other 
to normal outdoor levels of airborne particulate matter concluded that 
women living in areas with higher concentrations had higher levels of heart 
disease. It isn't clear what exposure anyone received since the 
measurements were presumable made of outdoor levels at centrally located 
air monitoring stations and no one knows where the women with heart disease 
were during all of their lives or what they actually inhaled.  On the basis 
of these and other similar studies the EPA in 2011 is scheduled to question 
its standards for airborne particulate matter. Presumably they will 
recommend lower ambient air concentration limits on particulate matter and 
limits on emission sources.

Otto


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Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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