POTENTIAL LUNG-CANCER RISK FROM INDOOR RADON EXPOSURE

The contribution of radon daughter exposure to excess lung cancer inunderground miners is universally accepted. These miners received exposuresfrom tens to thousands of WLM in a relatively few years. Although theminers were also exposed to other noxious agents in mines, the appearanceof the excess lung cancer mortality in several types of mines and theincrease with increasing exposure provide convincing evidence of the roleof radon as the carcinogen. It is conceivable that exposures to radon at anaverage concentration of one to two pCi/liter, the levels for a majority ofhomes, might not produce excess lung cancers. This would require that alifetime exposure at low concentrations produce a different response fromthat of a few years at higher levels for the miners. This is unlikely butnot impossible. The current environmental epidemiology is of varyingquality. The better studies may give some answers in a few years. Thesestudies are more likely to establish an upper limit of risk than to providean exposure‐response model. Present risk estimates cannot be usedaccurately in estimating the overall lung cancer risk to the US population, since there are no good data on average exposure and exposure distribution.For example, the number of homes above the EPA guideline of four pCi/litermay range from two million to 10 million. An estimate of the actual radonexposure in the US may be forthcoming from a planned EPA survey, but thesedata will not be available for a few years. In the conservative traditionof radiation protection, indoor radon exposures in homes are estimated toproduce a number of excess lung cancers in the population. One estimate bythe NCRP is about 10,000 deaths per year in the US, for an average annualestimated exposure of 0.2 WLM (about one pCi/liter). The National Academyof Sciences (BEIR IV) estimates 13,000 deaths for the same exposure, andthe EPA's estimate is 5,000 to 20,000. Copyright © 1990 American Cancer Society