Re: Cohen's Observation

[BERNARD L COHEN <blc+@PITT.EDU>]

On Sat, 14 Jun 2003 epirad@mchsi.com wrote:



> ----------------------------

> We addressed the validity of Cohen's mortality data before.  For the SEER

> states, his mortality data had only mediocre agreement with good incidence

> data.  See our papers in Health Physics.  Cohen used mortality data while

> incidence data is more appropriate. We showed in Iowa (a SEER state) that when

> more valid lung cancer incidence data was used, the inverse association

> disappears. An analyses limited to SEER states

> http://seer.cancer.gov/registries/index.html  would be an vast improvement

> over the mortality data that Dr. Cohen uses.



     --I used the mortality data for 1970-1979 and for 1979-1994. These

are the only sets of data for which lung cancer mortality rates are

available for anywhere nearly all of the counties. I did not use the SEER

data because it is not available for most counties, because I don't

understand why it is better than mortality data, and because entering it

into my files would require a lot of time and effort and I doubt if the

results would be publishable.



>

> Radon Measurements

>

> Look at a county map of the United States.

> http://www.epa.gov/iaq/radon/zonemap.html    Look at the variation in county

> sizes per state.  Imagine how poorly a few short-term (2-7 days tests) radon

> tests represent the radon progeny exposure for individuals in any county, let

> alone huge counties as can be seen on the map.  In fact, many of the

> measurements were made in basements where people spend limited time.



	--My radon data are derived from 3 sources, our own 350,000

measurements, EPA measurements, and measurements sponsored by individual

states. If either of these 3 were used alone, the same results would be

obtained. The correlations between the 3 sets is very good. These things

are discussed in more detail in my 1995 paper in Health Physics, and

elsewhere.





> We showed that if we would have used year long basement measurements in the

> Iowa Study, we would have found a protective effect from radon for lower

> exposures.   http://www.aarst.org/news_pdf/2002_IowaU_Follow-up_Study.pdf

> I think most people would agree that short-term screening or long term

> basement measurements do a poor job of predicting radon exposure for an

> individual let alone a county.



	--The validity of our measurements is discussed extensively in

published papers that have not been disputed -- references available on

request.



> In a paper we published in American Journal of Public Health. 80(8): 926-30,

> Aug 1990 showed Dr. Cohen's LSC radon detector had very poor precision.

> However, I would hope that this spot check was not reflective of the overall

> performance of this detector.



	--We always passed the EPA quality assurance tests without

difficulty. To the best of my knowledge, they are highly respected in the

radon measurement community.





> A better question then the one you posed may be why is there an inverse

> association between Cohen's county radon concentrations and his county

> estimated smoking rates.  Smoking is correlated with so many other factors

> that also affect lung cancer incidence so adjustment is needed for the total

> combined effects of smoking related factors.



	--Uncertainties in our smoking data are discussed extensively in

our papers, and reviewed in Sec $ of Item #7 on my web site





> Remember, we already showed that Cohen's summary smoking information alone

> does a poor job of explaining the lung cancers within the counties.



	--On the contrary, it does an excellent job of inndicating that

the great majority of lung cancers are caused by smoking.



 There is

> little surprise that residual confounding exists in his data.  The proof of

> that confounding has been pointed out by Drs. Gilbert and Puskin who clearly

> showed that the inverse association is found for other smoking related cancers.



	--They claim that the Puskin observation would be resolved by a

stronger negative correlation between smoking and radon. My response to

Puskin (on my web site) shows that this is not true. The stronger negative

correlation do a poorer job of explaining the smoking vs lung cancer

correlation.



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