Environmental tobacco smoke and lung cancer: Uncertainties in the population estimates but not in the causal association — a rejoinder to gross

This article is a rejoinder to the article by Gross in this issue, in which he claims that 'any range [of estimates of lung cancer deaths attributable to environmental tobacco smoke (ETS)] must encompass an estimate of zero deaths, and that the uncertainties are so great as to cast serious doubt on the use of any quantitative estimate'. The U.S. Environmental Protection Agency's (EPA) conclusion that ETS is a human lung carcinogen was based on the total weight of evidence, not just the 11 U.S. epidemiology studies of ETS and lung cancer that Gross discusses with respect to the population risk estimates. This conclusion was unanimously endorsed by the Agency's independent Scientific Advisory Board and is in concurrence with the conclusions of other organizations. As for the population risk estimates, the EPA report acknowledges uncertainties in these estimates. However, we maintain that the estimate of 3000 lung cancer deaths per year in U.S. non-smokers is a reasonable point estimate. Furthermore, we have relatively high confidence in this estimate compared to cancer risk estimates for other environmental pollutants, because it is based on human data from actual environmental exposure levels.