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Re: Source of cancer data
John,
Epideiologists who would choose Field's Iowa incidence in 431 over Cohen's
mortality in 100,000 plus (showing such consistent results), must be
inexperienced.
This exchange with Professor Cohen may interest you.
Howard Long MD MPH, Family Doctor and Epidemiologist
363 St. Mary St., Pleasanton CA, 94566
(925) 846-4411, Fax 4524, Page 787-0253 hflong@pacbell.net
12/17/01
Dear Professor Field,
To answer,
1. My epidemiology background comes from a, UCB PH, Professors Wm Reeves
(later Dean) and Reuel Stallones (later Dean at UTexas PH), b, critical
analysis of Quality of Medical Care, NC GP 1953-54 (showing selective misuse
of statistics by Harvard professors), c, my examination of 91% of all 640
3,4,5th graders in Dublin in 1965 (used by LLNL here as controls for normal
rate of palpable thyroid after above-ground tests), d, ongoing skeptical
observations of medical literature and of presentations at Doctors for
Disaster Preparedness by Luckey, Pollycove, Muckerhide, B Cohen, Teller and
many others known all too well to you.
2. Forum critique (as previous at DDP) of what you mischaracterize as “Cohen’s
Fallacy”, leaves me agreeing with a burgeoning majority of scientists.
“Cohen’s Discrepancy” shows clear association of LESS lung cancer mortality
with mean residential radon levels between 1.3 pCi/l and 4.5 pCi/l, than below
1.0 pCi/l. The LNT (linear, no threshold hypothesis) is inconsistent with this
data and numerous other studies. Your observation that quantity does
substitute for quality is valid, of course. I believe it does not apply here.
a, 100,000 nationwide county death certificates of lung cancer seem little
subject to error and selection (vs Iowa diagnoses of lung cancer during one
year with just 431 cases). b, the 12, SD error bars for each ¼ pCi/l from 1 to
4 are very consistent, with smooth slope and none near NOAEL until 5 pCi/l for
a smaller number of females.
Iowa women may have not only more exposure to radon but also to farm silo or
kitchen carcinogens, sleep deficiency, or other of the thousands of cancer
immune factors. I assume you corrected for age (I did not see your raw data).
Older women, more subject to cancer, would tend to live in houses more tightly
closed against the cold and thus incidentally retaining more radon. I believe
that radon would mitigate the larger factor of age “causing” lung cancer.
I am happy that you agree that your Iowa case-control study could not show,
“Radon causes lung cancer”. I know that many health physicists on radsafe will
have renewed respect on seeing your letter to CA, Journal of the American
Cancer Society, correcting its overreaching conclusion from your study.
I did not see your specific answers to these problems, yet:
Problems with the Iowa Radon and Lung Cancer Case-Control Study
1. Selection of Location:
”More than 60% of the basements of both cases and controls [had radon levels
>4 pCi/l]”.
This suggests that the study area selected, Iowa, was among < 1% of USA with
lung cancer mortality not clearly LESS with more radon. (See B. Cohen, Mean
Residential radon level for 1601 US counties vs Lung cancer mortality, 1995).
2. Small numbers:
“The researchers found that 33% of living area for the lung cancer cases and
28% - for the control group exceeded the EPA’s action level of 4 pCi/L.”
This suggests that the relatively few cases, 413, (vs over 100,000 in B
Cohen’s study) with small differences (33% vs 28%), with other factor large
(smoking 10x as big) may result in an unacceptably high probability of chance
association.
3. Over-reaching conclusion:
“Radon causes lung cancer” cannot be concluded from any case control study,
any more than from any ecologic study. Nor could either type of study claim,
“Radon prevents lung cancer”. Only reproducible, double-blind, prospective
experiments can show cause-effect. I am contemplating feasible design for such
a study.
Full disclosure of data for independent analysis is required for scientific
credibility.
(See 1,2,3 above). Many conflicts of interest are inherent in funding,
position and hidden agenda. This should humble us all.
Respectfully,
Howard Long MD MPH
John Williams wrote:
> Jim,
>
> I am not talking about the Iowa Radon Study, which most
> epidemiologist believe is the state-of-the-art Radon Study. It is
> even highlighted on the EPA web site: http://www.epa.gov/iaq/radon/
> Rather, I am talking about Smith using Cohen's own data and just
> inserting more valid lung cancer incidence information then the
> mortality data he used. Read the paper by Smith et al. instead of
> just the abstract.
>
> Health Phys 1999 Sep;77(3):328-9 Related Articles, Books, LinkOut
>
> Comment on:
> Health Phys. 1999 Apr;76(4):439-40
>
> Cohen's paradox.
>
> Health Phys 1998 Jul;75(1):11-7 Related Articles, Books, LinkOut
>
> Comment in:
> Health Phys. 1998 Jul;75(1):23-8; discussion 31-3
> Health Phys. 1999 Mar;76(3):316-9
>
> Comment on:
> Health Phys. 1995 Feb;68(2):157-74
> Health Phys. 1997 Apr;72(4):623-8
>
> Residential 222Rn exposure and lung cancer: testing the linear no-
> threshold theory with ecologic data.
>
> Smith BJ, Field RW, Lynch CF.
>
> College of Medicine, Department of Preventive Medicine and
> Environmental Health, University of Iowa, Iowa City 52242, USA.
> bill-field@uiowa.edu
>
> In most rigorous epidemiologic studies, such as case-control and
> cohort studies, the basic unit of analysis is the individual. Each
> individual is classified in terms of exposure and disease status.
> However, in ecologic epidemiologic studies, the unit of analysis is
> some aggregate group of individuals. Summary measures of exposure and
> disease frequency are obtained for each aggregate, and the analyses
> focus on determining whether or not the aggregates with high levels
> of exposure also display high disease rates. The ecologic study
> design has major limitations, including ecologic confounding and
> cross level bias. Cohen has attempted to circumvent these limitations
> by invoking the linear no-threshold theory of radiation
> carcinogenesis to derive aggregate "exposures" from individual-level
> associations. He asserts that, "while an ecologic study cannot
> determine whether radon causes lung cancer, it can test the validity
> of a linear-no threshold relationship between them." Cohen compares
> his testing of the linear no-threshold relationship between radon
> exposure and lung cancer to the practice of estimating the number of
> deaths from the person-rem collective dose, dividing the person-rem
> by the number of individuals in the population to derive the
> individual average dose, and then determining individual average risk
> by dividing the number of deaths by the number of individuals in the
> population. We show that Cohen's erroneous assumptions concerning
> occupancy rates and smoking effects result in the use of the wrong
> model to test the linear no-threshold theory. Because of these
> assumptions, the ecologic confounding and cross level bias associated
> with Cohen's model invalidate his findings.
>
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> Furthermore, when more recent Iowa county lung cancer incidence
> rates are regressed on Cohen's mean radon levels, the reported large
> negative associations between radon exposure and lung cancer are no
> longer obtained.
>
> ..................................
> Cohen does not even attempt to provide discrete analytical proof that
> they are wrong.
>
> John Williams
>
> Sent by Law Mail
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