RADON UPDATE - FACTS CONCERNING ENVIRONMENTAL RADON - LEVELS, MITIGATION STRATEGIES, DOSIMETRY, EFFECTS AND GUIDELINES

The risk from environmental radon levels is not higher now than in the past, when residential exposures were not considered to be a signific ant health hazard. The majority of the radon dose is not from radon it self, but from short-lived alpha-emitting radon daughters, most notabl y Po-218 (T-1/2 3 min) and Po-214 (T-1/2 0.164 msec) along with beta p articles from Bi-214 (T-1/2 19.7 min). Radon gas can penetrate homes f rom many sources and in various fashions. Measuring radon in homes is simple and relatively inexpensive and may be accomplished in a variety of ways. Although it is not possible to radon-proof a house, it is po ssible to reduce the level. In high radon areas, if the average level is higher than 4-8 pCi/liter (NCRP recommended level is 8 pCi/liter; E PA recommended level is 4 pCi/liter), appropriate action is advised. T he shape of the dose response curves for miners exposed to alpha-emitt ing particles in the workplace is consistent with current biologic kno wledge. It is linear in the low dose range and saturates in the high d ose range. No detectable increase in lung cancer frequency is seen in the lowest exposed miners (those with exposures <120 WLM, the relevant dose interval for most homes). Evidence for a health effect from rado n exposure is based on data from animal studies and epidemiologic stud ies of mines. Extensive radiobiologic data predict a linear dose-respo nse curve in the low dose region due to poor biological repair mechani sms for the high density of ionizing events that alpha particles creat e. However, no compelling evidence for increased cancer risks has yet been demonstrated from ''acceptable'' levels (<4-8 pCi/liter).