[ RadSafe ] Indoor Radon

Wed May 18 19:33:58 CEST 2005

	I am writing about an article in the April 2005 Health Physics Journal entitled "ESTIMATED RISKS OF RADON-INDUCED LUNG CANCER FOR DIFFERENT EXPOSURE PROFILES BASED ON THE NEW EPA MODEL" by Jing Chen.  I would simply like to comment on its implications, suggest an extension, and start a (hopefully flame-free) dialogue.
	Table 1 of the article gives Estimated Lifetime Relative Risk (LRR) of lung cancer from different levels of radon exposure for a 110-year lifetime.  These are relative to the baseline values for persons of the same sex and smoking status and no radon exposure.  The baseline risks are given in footnote (a) as 0.0676, 0.0907, and 0.00695 for male population, smokers, and non-smokers respectively.  The female risks are likewise given as 0.0253, 0.0618, and 0.00538.  I would like to concentrate on the LRR values for the highest radon levels presented (1000 Bq/m3) for non-smokers: 7.387 for males and 6.901 for females.
	For a 110-year exposure to an indoor radon concentration of 1000 Bq/m3 (27 pCi/l if I've done the conversions correctly) the male non-smoker risk would be 7.387*0.00695 = 0.0513 and the female non-smoker risk would be 6.901*0.00538 = 0.0371.  Note that these are each approximately one half of the baseline values given in footnote (a) for smokers with no indoor radon exposure at all!
	The first conclusion I draw is that I am justified in my statement that if you are concerned about the radon levels in your home the most cost effective fix is to stop smoking.  Indoor radon, in my humble opinion, is a non-problem for non-smokers.
	The next follows closely on the heels of the first.  As a society, we would get more bang for our buck if we took a lot of the money spent testing and mitigating indoor radon exposures and a good chunk of the radon budget for the EPA and instead spent it on genuine efforts to stop smoking in the current but especially future population.  As a bonus, we would get the additional benefits from reducing the costs from other diseases exacerbated by smoking.  Now I know that pigs have a much higher probability of flying to the moon using their own power than this conclusion has of being implemented but it is an interesting hypothetical one anyway.  At the very least, implementing the suggestion at the end of this letter would allow the money now spent to be used more effectively.
	I imagine some might be thinking "Well, maybe I'll give you your conclusions for non smokers but certainly not for those long term smokers who have just quit."  This leads me to my suggestion for extending the article.
	I thank Dr. Chen for this article, which has already proven useful to me, but have a suggestion for an additional effort.  The article refers to the group as "ever smokers" as opposed to the other category of "never smokers."  It is clear that the group "ever smokers" could use some refining.  A person who smokes one pack per day for only one year and then quits for 29 years obviously has a lower lung cancer risk than a three pack per day 30-year smoker who never quits.  Also, if smoking risk were only based on "ever smoked," doctors wouldn't be after people to quit or cut back; their risk would already have been established as the "ever smoked" value.
	I would think it would be useful to expand the tables in the article to include the smoking habits of the "ever smokers."  It might then need to become a spreadsheet because of the complexity but it is easy to imagine.  Put in smoking and indoor radon exposure histories and out pops the LRR.  The information that would need to be folded in is the risk of lung cancer by smoking history (packs per day, smoking duration, time since quitting if applicable, and maybe age while smoking).
	The expanded tables (or spreadsheet) would then make possible informed decisions about whether or not a particular indoor radon exposure level is in need of mitigation for a particular individual's (or family's) smoking situation.
	One way it could be used is as follows:  The EPA action level of 4 pCi/l is approximately 150 Bq/m3.  Take the lifetime general population male or female LRR for 150 Bq/m3 and multiply it by the baseline risk for that sex and get an absolute lifetime risk for exposure at EPA's action level for the general population of each sex.  Now divide that absolute risk by the baseline risk for either smoker or non-smoker for that sex to determine what Lifetime Relative Risk it must have to give that same absolute risk.  Then look at the tables to find what radon concentration gives that Lifetime Relative Risk.  One problem is that when you do that you have to extrapolate from the tables to higher concentrations in the case of non-smokers.  I made the simplifying assumption that the LRRs were linear even when extrapolating.  For smokers, I made the assumption that the LRRs were linear between the values for 0 (LRR = 1) and 100 Bq/m3.  After doing those calculations with the above assumptions, I determined the indoor radon concentrations that would yield the same risk for each sub-group as 4 pCi/l would yield for the general population.  For male and female smokers, the concentrations were 1 pCi/l and 0 pCi/l respectively.  For male and female non-smokers, the concentrations were 58 pCi/l and 29 pCi/l respectively.  The zero value for female smokers reflects that their baseline risk with no radon exposure [0.0618] is already larger than the absolute lifetime risk for the female general population at EPA's action level [0.0253*1.544 = 0.0391].  That is: female smokers should live outdoors, male smokers should mitigate their houses when the levels are above about 1 pCi/l, female non-smokers above about 30 pCi/l, and male non-smokers above about 60 pCi/l.  That would yield the same risks as the general population mitigating above 4 pCi/l.
	These values are not meant as suggestions for implementation but only presented to illustrate the concept.  A more refined spreadsheet would enter the smoking history of either the current occupants or potential buyers and thus be able to better determine whether that particular house's radon level should be mitigated for those particular individuals.  This would result in the same overall risks as the current EPA policy but would only mitigate those houses that really need it.  The current broad-brush policy doesn't call for mitigation of some houses that really should be mitigated (occupied by smokers) and does call for mitigation of some houses that really needn't be (occupied by never-smokers).
	One final observation is that the cost of mitigating smokers' houses to essentially outdoor levels would probably be astronomical and there would be few homes of never smokers that would ever need any mitigation.  That leads quickly back to the conclusion that the best way for society to deal with indoor radon levels is to turn the population into never smokers.

Patrick Glennon
Philadelphia

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