Annex E of UNSCEAR 2006: Sources-to-effects assessment for radon in workplaces and homes

Levels of radon indoors vary widely both within countries and between countries, with geometric mean concentrations of radon in indoor air ranging from less than 10 Bq/m³ in the Middle East to more than 100 Bq/m³ in several European countries. The average dose from inhalation of radon gas and its short-lived decay products represents typically about half of the effective dose received by members of the public from all natural sources of ionizing radiation. Radon and its short-lived decay products are well established as lung carcinogens. The recent pooling of residential case control studies in Europe, North America and China now provides a direct method for estimating the lung cancer risk. The excess relative risk from long-term residential exposure to radon at 100 Bq/m³ is established with reasonably good precision and is considered to be about 0.16 (after correction for uncertainties in exposure assessment) with about a three-fold factor of uncertainty higher or lower than that value. Because of the synergistic interaction between the effects of radon exposure and those of inhalation to tobacco smoke, smokers account for nearly 90% of the population-averaged risk from residential exposure to radon.