Blowin' in the Wind--Jonathan Samet and Air Pollution

Breath-Taking: Premature Mortality Due to Particulate Air Pollution in 239 American Cities Natural Resources Defense Council, May 1996

This study estimates that 64,000 people may die prematurely from heart and lung disease each year due to particulate air pollution. This estimate is based on two epidemiologic studies: Harvard's 1993 "Six City Study" (New Engl J Med 1993;329:1753-1759) which followed over 8,000 people in six small cities for a period of 14 to 16 years, and a 1995 American Cancer Society Study of a half a million people in 151 cities (Amer J Resp Crit Care Med 1995; 151:669-674). Both studies are the "ecologic" variety of epidemiology--i.e., studies that examine the association between disease occurrence in groups and the guessed exposure of the groups. Ecologic studies contrast with, for example, case control studies where exposures in cases of disease are compared with exposures in controls without disease.

One of the more interesting aspects of this study is that one of its reviewers is none other than Jonathan M. Samet. Samet is a staunch defender of the radon epidemiology (and we all know that radon is such a public health problem that no one noticed it until the 1980s!). When the link between radon and lung cancer risk came under attack because published ecologic studies were finding no and even negative associations between radon and lung cancer risk, Samet moved to head off the attack.

As Defender of the Radon Realm, Samet published an article which was highly critical of ecologic epidemiology (Health Phys 1993;65(3):234-251). Samet concluded that

The methodologic limitations inherent in the ecologic method may substantially bias ecologic estimates of risk... In fact, further ecologic studies of indoor radon and lung cancer are to be discouraged.

Now, Samet has reversed his position on ecologic studies for the NRDC air pollution study. Has ecologic epidemiology been healed? For Samet, it probably depends on the circumstances. While ecologic studies are bad for radon grant grubbing and fearmongering, they're clearly good for particulate air pollution grant grubbing and fearmongering.

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