Noting a negative correlation between average radon levels and lung
cancer mortality in Montana counties, Hart (2011) “questions the notion
that radon is deadly in Montana.” Results from a much larger ecological
study of the correlation between county radon levels and lung cancer
mortality across the whole United States were published in the 1990s
(Cohen 1990, 1995). Like Hart, Cohen found an inverse correlation
between radon concentrations and lung cancer. Such ecological studies
suffer, however, from lack of individual information on radon exposures
and other lung cancer risk factors, including smoking. Indeed, there is
compelling evidence that the observed negative correlation was a spurious
one due to confounding by smoking. First, the same negative correlation
between radon and cancer mortality was observed for a variety of
smoking-related cancers, but not for cancers unaffected by smoking
(Puskin 2003). More recently, it has been found that – even using average
county radon concentrations as a surrogate for individual radon exposure
– the correlation between radon and lung cancer becomes positive,
once one controls for individual smoking habits (Turner et al. 2011).
Even more definitive is the evidence from a pooled analysis of casecontrol
studies, which were based on radon measurements in the homes
of individual lung cancer cases and controls, matched by age, sex, and
smoking history (Darby et al. 2005). These results firmly establish that
lung cancer risk increases with increasing radon exposure in homes.
Jerome S. Puskin U.S. Environmental Protection Agency