The Puskin Paper on radon and smoking

[Kai Kaletsch <eic@shaw.ca>]

Friends,



Now that some time has passed after the reward silliness, perhaps we could

have a serious discussion on what I think is an important paper. Following

is my take on the paper and Dr. Cohen's response. I hope there are other

radsafers who also have thoughts on the technical aspects of this debate.



The Puskin Paper:



I think Dr. Puskin's paper (Smoking as a confounder in ecologic

correlationsof cancer mortality rates with average county radon levels.

Health Phys. 2003;84:526-532) is a very important work in steering this

debate back to a rational level.



Puskin states that an inverse relationship exists between lung cancers in a

county and the average radon level. He also notes that errors such as

mobility, changes in housing construction over time, etc. would reduce the

expected slope of the lung cancer vs radon graph, but they could not turn

the slope negative.



Puskin then offers what he believes could be an explanation. To me, that is

an indication that he believes that we live in a rational universe and that

data is explainable. This is a major deviation from the entrenched position

of the people who have argued the LNT side of the debate. Essentially, they

have said that ecological data can not be explained and does not need to be

explained.



Puskin shows that other smoking related cancers, notably cancer of the oral

cavity, are negatively associated with radon concentrations. Puskin's

conclusion is that radon and smoking must be more strongly negatively

correlated than Cohen assumes and that the excess lung cancers in low radon

areas are due to this fact.



There are at least two conditions that must be met for Puskin's conclusion

to logically follow from his observation:



1) there can be no DIRECT influence of radon on oral cancers, otherwise that

direct influence could be used to explain the observed correlation between

radon and oral cancer and smoking doesn't enter the picture. Cohen points

out that this assumption has not been validated. See below under "Cohen's

Response".

2) There can be no INDIRECT association of radon with oral cancers OTHER

THAN SMOKING. Otherwise that association could be used to explain the

observed correlation between radon and oral cancer and smoking doesn't enter

the picture. To do that, Puskin would have to treat other possible

confounders in a manner similar to what Cohen has done. Puskin does not do

that. It only takes one plausible alternate explanation for the data to

invalidate the author's conclusion. Here, I'll offer one such explanation:



Suppose that oral health is strongly associated with socioeconomics

(stronger than the relationship between non-smoking and socioeconomics).

This is not a far-fetched idea. You just have to go downtown and look at the

people asking for spare change. They usually don't have very good oral

health. If general oral health is related to oral cancers (also not an

outrageous assumption) and radon is related to socioeconomics (which we know

it is) then we can explain a relationship between oral cancer and radon,

without ever mentioning smoking and Puskin's conclusion is not valid.



Cohen's Response:



Cohen correctly points out that Puskin has not offered any explanation why

he believes that smoking can influence the rate of oral cancers and radon

can not. After all, the carcinogens in cigarette smoke would have a very

similar pathway to the mouth as radon progeny.



Cohen also offers a "test" of the Puskin hypothesis (and I don't agree with

it). It goes like this:



Cohen admits that there is a negative correlation between radon

concentration and smoking, but claims that the correlation is not strong

enough to account for the excess lung cancers found in low radon areas.



He goes on to say that, even if he ordered the counties according to smoking

prevalence and assumed a perfect negative correlation with the average radon

concentration, that would not be sufficient to explain the negative

correlation between average radon concentration and lung cancer. In other

words, there is not that much difference in smoking prevalence between

counties to explain the differences in lung cancer, regardless if the low

radon counties happen to be at the top or the bottom of the smoking scale.



This does not make any sense to me: Either you have good smoking data, then

your ranking will be pretty good and you don't have to reorder the counties,

or your data is bad and then your ranking may or may not be correct, but the

width of the distribution is certainly biased toward the null. Consider the

following example:



There are two counties. County 1 has 100% non-smokers and county 2 has 100%

smokers. You decide to determine smoking status by asking everyone to

complete a survey. Half of everyone in each county does a good job filling

out your survey. The other half randomly checks off yes or no, without

reading your question. Your survey will then show county 1 has 75%

non-smokers and 25% smokers while county 2 has 75% smokers and 25%

non-smokers. Your ranking is still correct (county 1 has more non-smokers)

but the measured width of your distribution is only half of the correct

width. The true width of the distribution might be enough to account for

differences in lung cancer incidence, while the measured width might not be.



Cohen also explains the sources of his smoking data and points out that all

3 independent methods of estimating smoking produce similar results. To me,

that is more convincing than the reordering "test". It is also impressive

that no one has yet proposed a reasonable smoking distribution, which would

make Cohen's results compatible with LNT.



Conclusion:



I hope that more people follow Puskin's example and offer new input into the

debate. Far too few people are involved in the scientific part of the radon

debate. (There are plenty of people on the standard setting side of the

debate.)



I hope that no one (including the NCRP) will consider the findings of the

NCRP or any other group as final, until the theory is shown to be compatible

with the data. I have no problem with NCRP or ICRP recommendations being

used for setting standards, however. After all, the purpose of committees is

not to do any science, but rather to build consensus by applying reasonable

and conservative principles. (Remember what the RP stands for!). They are on

the standard setting side of the debate.



Kai

http://www.eic.nu



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