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Re: Radon Health Risks
Kai
The miner studies are not ecologic studies. We can debate the degree of
exposure misclassification in the miner studies, but variation in radon and
progeny in mines does not make the miners studies ecologic in nature.
Individual exposure information was assigned to each individual and
information on many confounders and effect modifiers were collected in many
cases for each person.
You can not compare the miners studies with the ecologic studies since each
study design has it own strengths and limitations.
Do you really think that 10 county screening radon measurements performed in
the basement (not in the living area) and not taken at random are
representative of the living area radon concentration for everyone in a
county? I know some counties with several hundred thousand residences where
the radon varies from 0.1 pCi/L to over 300 pCi/L. Do not forget in the
miner studies these exposures were also assigned to everyone so when you
compare a highly exposed group to a lesser exposed group it is a relative
process.
However, your point about the uncertainty of the measurements is well taken.
That is why most epidemiologists I know prefer the residential
case-control studies.
I don't think every post is financially or politically motivated, but many
are.
A group of us (radiation biology and epidemiology students, post docs) had a
discussion (during a journal club where we were assigned an ecologic paper
of Dr. Cohen's) about radsafe a few months ago. The radiation biology/IH
students were talking about when they joined this list for a short time,
they could not believe how much the risk of radiation exposure was played
down (I am sure most HPs will say not played down, but presented fairly)and
how just about every epidemiology study is criticized on the list unless it
demonstrates a hormetic effect. On this list, the finding of the study
outweighed the quality of the design of the study.
We looked at the archives and were really surprised that a well designed
study like the Iowa Radon study was attacked so much in the past, but an
ecologic study like Dr. Cohen's was barely criticized except possibly by a
few epidemiologist who may be on the list now and then. However, I am not
sure why any epidemiologist would stay on this list for long.
We (epidemiologist)started monitoring the list months ago and we naively
thought the Radiation Biology/IH students were wrong. We were under the
impression that HPs really would try to urge practices that would reduce
exposure to as low as reasonably achievable. We have found quite the
opposite in some cases. Lately, the discussion has even been moved to the
best place to put the radioactive materials under your bed.
At the same time, we have been monitoring other lists such as an IH list
where we found more concerns about limiting radiation and chemical exposure.
For the people monitoring this list, I can see how they come away with the
thought that HPs have moved away from the safety of the people they are
hired to protect. In the couple of Health Physics Society meetings I have
attended, the majority of HPs I met were not representative of the postings
on this list. Perhaps some of the differences on this list may be the
massive hormesis postings that drive most of the "middle of the road" HPs
off the list.
I know I will get heat for this post, but please view it from a perspective
of someone looking in from the outside. It may be worthwhile to try to get
some epidemiologist more involved with your society to discuss some basic
epidemiology and the strengths and limitations of various sample designs.
Respectfully, Don Smith
>
>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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>
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