Radon: a special case in radiation protection

The conversion conventions of ICRP 65 are based on equality of detriment, not on dosimetry. They are derived from epidemiological studies on miners by comparing the risk of having fatal lung cancer with the detriment associated with a unit of exposure in ICRP 60. Things have moved on since ICRP 65 and the new scientific evidence (numerator change, denominator change and also the dosimetric approach in ICRP 66) is pointing away from ICRP 65 in the direction of the long-established UNSCEAR conversion factor of 9 (nSv h(-1))/(Bq m(-3)) radon progeny exposure, which is 50% higher than the ICRP 65 conversion convention for members of the public. Anyhow, smoking, by the almost multiplicative relationship with radon, determines to a considerable extent the lung cancer risk. Although there is a fairly general consensus among health physicists that radon exposure constitutes the largest and most variable contribution to the population exposure from natural sources, they are divided between themselves on the numerical value of the risk estimates and on the need and urgency to incite the population to take action. This relaxed attitude to radon exposure is reflected in the regulatory approach, which is very much in line with the perceived risk by the population.