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Radon Health Risks
Radsafers, I just signed back on Radsafe for a very short period to post a
message or two.
Don Smith has been sending me a lot of emails and asking my opinion on
various topics. I sent him my previous view (which he sent to Radsafe)
that briefly presented my view on Dr. Cohen's work. He has sent me some
more posts concerning the miner studies.
As for the recent postings concerning miners, I would urge all to consider
the following observations. In any examination of the health risks posed
by radon, there are uncertainties. Suppose for example there is a lung
carcinogen that is highly correlated with radon exposure but
unmeasured. Then any estimation of radon risk would be enhanced by the
effects of the unmeasured factor. This is classical confounding. With
clinical trials randomization prevents any unmeasured factors from
confounding the observed effect, at least in expectation. Obviously, we
can not perform clinical trials to determine the long term risk of
prolonged residential radon exposure. However, this sort of possibility
is ALWAYS a limitation with observational studies. It is used all the time
by industry to attack occupational studies -- they suggest the potential
for an unmeasured confounder. I think that those that suggest that an
unmeasured confounding factor(s) caused the observed effects must present
some real data supporting the possibility. I would urge Duport or others
to demonstrate that any such (unmeasured) factor: (1) causes a comparable
level of lung cancer risk (actually it must be a substantially greater risk
since it won't be perfectly correlated); (2) was present in the mines; (3)
is sufficiently correlated with radon exposure to induce the
effect. Finally and very importantly, Duport or others must demonstrate
that this confounding occurred in virtually all miners studies, including
uranium miners, fluorspar miners, iron miners and tin miners.
If we take a closer look at his suggested factors, silica, nickel dust,
arsenic dust, diesel soot, and NOx. Risk of lung cancer from silica is
very small in general -- a larger risk occurs only in silicotics. There is
no strong evidence that silicosis is a huge issue in the various
mines. During the years covered in most of the miner studies, I do not
think diesel engines were used yet underground. Arsenic did occur in some
mines, but not in all mines. In addition, arsenic in dust is more
associated with dry-drilling, as opposed to wet-drilling, technology than
with ventilation. It is also sensitive to the ore body, and not all that
correlated with radon concentrations. Is NOx not really a problem , I was
not aware there was that much combustion. However, my area of expertise is
focused more on the residential radon studies than of studies of miners.
The residential radon studies were funded to directly examine the risk
posed by residential radon exposures (without the need for linear
extrapolations) and to limit confounding from occupational sources.
Regards, Bill
***************************************************************************************
R. William Field, M.S, Ph.D.
College of Public Health
Research Scientist - Department of Epidemiology
Adjunct Professor - Department of Occupational and Environmental Health
Graduate Faculty - College of Public Health
N222 Oakdale Hall
University of Iowa
Iowa City, Iowa 52242
319-335-4413 (phone)
319-335-4748 (fax)
mailto:bill-field@uiowa.edu
College of Public Health http://www.pmeh.uiowa.edu/index.html
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