Finally, this study used ecologic measures of residential radon to adjust for the potential confounding effects of residential radon exposure, rather than residential radon concentrations measured in individual homes.
However, in previous work, estimates of increased lung cancer mortality caused by environmental radon observed in the CPS-II were compatible with estimates obtained in combined analyses of residential case-control studies (17).
Mean radon concentrations were also weakly (and inversely) correlated with PM2.5, suggesting that any potential confounding effect of residential radon concentrations on PM2.5–lung cancer associations is likely small.
In conclusion, results from this large prospective study showed positive associations between mean long-term ambient PM2.5 concentrations and lung cancer mortality in lifelong never-smokers, further strengthening the evidence that ambient concentrations of PM2.5 measured in recent decades are associated with small but measurable increases in lung cancer mortality.
Results also demonstrate that the magnitude of lung cancer risk associated with exposure to PM2.5 is notably smaller than that caused by active smoking (48).