Re: Deaths from fossil fuel burning air pollution

[Steven Dapra <sjd@swcp.com>]

Nov. 30

There has been a lot of electronic ink spilled here (mostly by Drs. Cohen
and Raabe) over air pollution-induced mortality.  Dr. Cohen initiated the
debate (on Nov. 17) by discussing a paper by Pope, et al. (Am J Respir Crit
Care Med 151:669-674;1995).  I would like to present a short quote from the
Pope et al. paper, and then discuss two uses of this paper elsewhere.

On page 670, Pope et al. describe their study population, writing:

"This analysis relied on data for 552,138 men and women drawn from the
American Cancer Society (ACS) Cancer Prevention Study II (CPS-II), an
ongoing prospective mortality study of approximately 1.2 million adults
[citation].  Participants were enrolled by ACS volunteers in the fall of
1982.  The resided in all 50 states, the District of Columbia, and Puerto
Rico, and were usually friends, neighbors, or acquaintances of the ACS
volunteers.  Enrollment was restricted to persons who were at least 30 yr.
Of age and who were members of households with at least one individual 45
yr of age or more."

This appears to be a self-selected study group.  It certainly is not a
statistical cross-section of the population of the United States (and
Puerto Rico), if only because it excludes everyone under the age of 30.

According to Table 1 (p. 670), the mean age at enrollment was slightly over
56 y.  Participants were 56 % female, 94 % white, and four percent black.

According to the 1998 Statistical Abstract of the United States, the mean
age of U.S. residents is 35.2 y.  The population is 51% female.  Whites
constitute 82 % of the population, and blacks 15 %.  

I am not suggesting the study is no good, I am merely saying it seems to be
self-selected and that the demographics don't reflect those of the U.S. as
a whole.  (I have omitted Puerto Rico here because its population is so
small.)

On Nov. 30, Prof. Cohen refers RADSAFERs to the book "Particles in Our Air:
 Concentrations and Health Effects," edited by Richard Wilson and John D.
Spengler (Harvard University Press, 1996).  In 1996 Wilson was in Harvard's
Department of Physics and its Center for Risk Analysis, and Spengler was in
Harvard's School of Public Health.

On October 18, 2000 Susan Gawarecki made a posting to RADSAFE ("Power Plant
Pollution Linked to 30,000 Premature Deaths Each Year") referring readers
to a report ("Death, Disease & Dirty Air") prepared by the Clean Air Task
Force.  This report (p. 4) claims there are 60,000 premature deaths per
year in the U.S. because of exposure to fine particles.  The Clean Air
authors refer readers to "Particles in Our Air" (Wilson and Spengler), page
212; however the 60,000 deaths figure is first mentioned on page 210, where
Wilson and Spengler end a general discussion of air pollution studies by
writing,  "The consistent picture that a public health authority should
consider is that 60,000 persons might be dying prematurely of air pollution
related problems in the United States each year [citation]."  The citation is:

"Shprentz, D.S. Bryner, G.C., and Shprentz J.S., (1996) "Breath Taking:
Premature Mortality due to Particle Air Pollution in 239 American Cities"
National [sic] Resources Defense Council (NRDC), New York, NY."  (This
should be "Natural" Resources, etc.)

I obtained a copy of "Breath Taking" (dated May, 1996) and began looking
for the 60,000 figure.  On page 29, "Breath Taking" begins talking about a
"landmark study . . . [that] linked ambient air pollution data with
information from an American Cancer Society [ACS] cohort of 1.2 million
adults from all 50 states."  The citation is to the Pope, et al. study that
Profs. Cohen and Raabe have been debating on RADSAFE.

On page 30, Shprentz, et al. write of the Pope, et al. study, "The
researchers concluded that modest air pollution exposures are shortening
the lives of Americans by several years."  Their source for this claim is a
Harvard School of Public Health press release dated March 9, 1995.

On page 32, Shprentz, et al. write, "Criticisms of the ACS study are that
the cohort was not drawn from a random sample of the U.S. population and
that historical pollution levels were not considered in assessing
cumulative exposures."  For this, they cite a USEPA "Air Quality Criteria
for Particulate Matter" draft, dated Nov. 24, 1995.

On page 44, Shprentz, et al. write that their analysis "is not an
epidemiological study of the relationship between particle concentrations
and mortality in U.S. cities." and, that their analysis "merely applies the
relationship observed in the study of the American Cancer Society cohort to
current particle concentrations is U.S. cities, to gauge the extent and
significance of the particle pollution problem."

So . . . everything - the Clean Air Task Force report, Wilson and Spengler,
and the American Cancer Society study - all comes back to the self-selected
cohort in the Pope, et al. study.

Steven Dapra
sjd@swcp.com



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