Modifiers of exposure-response estimates for lung cancer among miners exposed to radon progeny.

The association between lung cancer and exposure to radon decay products has been well established. Despite agreement on this point, there is still some degree of uncertainty regarding characteristics of the exposure-response relationship. The use of studies of underground miners to estimate lung cancer risks due to residential radon exposure depends upon a better understanding of factors potentially modifying the exposure-response relationship. Given the diversity in study populations regarding smoking status, mining conditions, risk analysis methodology, and referent populations, the risk estimates across studies are quite similar. However, several factors partially contributing to differences in risk estimates are modified by attained age, time since last exposure, exposure rate, and cigarette smoking patterns. There is growing agreement across studies that relative risk decreases with attained age and time since last exposure. Several studies have also found an inverse exposure-rate effect, i.e., low exposure rates for protracted duration of exposure are more hazardous than equivalent cumulative exposures received at higher rates for shorter periods of time. Additionally, the interaction between radon exposure and cigarette smoking appears to be intermediate between additive and multiplicative in a growing number of studies. Quantitative estimates of these modifying factors are given using a new analysis of data from the latest update of the Colorado Plateau uranium miners cohort.