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Re: Radon Health Risks
Bill,
Most of the so called "cohort" miner studies are really ecological studies,
since there is as much or more variation in radon readings within a mine
than among mines. There is no hope of assigning a reasonably accurate
individual dose by taking one reading per mine every few years. At least in
a well designed ecological study you use an average reading to assign to a
group, in a lot of the miner studies the ONLY reading in a particular mine
was used to assign to all miners. Most of the miner studies did not
adequately control for confounders, never mind cross-confounders.
What Philippe has done, is to propose several specific mechanisms which all
bias the miner results in the same direction. This is something no one has
been able to do with the ecological radon in homes data.
The calculated ERR/WLM differ by a factor of 30 among the 11 miner studies.
That means that any postulated confounder does not need to be very strongly
associated with radon. It could even be different confounders in different
mines or no confounders at all in the low ERR/WLM mines.
I don't think anyone is suggesting that the miner data should be thrown out.
Any theory must be able to explain ALL data without the use of the deus ex
machina of "cross level confounders". Philippe's work of suggesting and
quantifying the effect of confounders is adding credibility to the miner
studies, rather than detracting from it. It might change the results of the
studies, but it makes the data more believable.
Finally (this is not directed at you, Bill): I make the equipment that is
used in most Canadian uranium mines to measure radon progeny concentrations.
This equipment is also used by our federal and provincial governments. I
also make equipment that is used in the most modern uranium mine to trouble
shoot high radon gas levels. I have absolutely nothing to gain by minimizing
the risk due to radon/radon progeny. Some people on this list think that
every post regarding radon has to be politically or financially motivated.
It is sad that they cannot conceive of the idea that someone can formulate a
thought that is not connected with ulterior motives.
Best Regards,
Kai
http://www.eic.nu
----- Original Message -----
From: "Field, R. William" <bill-field@UIOWA.EDU>
To: <pduport@uottawa.ca>; <sonterm@EPA.NSW.GOV.AU>;
<radsafe@list.vanderbilt.edu>
Sent: Friday, January 18, 2002 5:36 PM
Subject: 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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