UNSCEAR recommends a reference value of 9 nSv (Bq·h/m).
For example, a person living (7000 h/year) in a concentration of 40 Bq/m receives an effective dose of 1 mSv/year.
Studies of miners exposed to radon and its decay products provide a direct basis for assessing their lung cancer risk. The BEIR VI report, entitled Health Effects of Exposure to Radon, reported an excess relative risk from exposure to radon that was equivalent to 1.8% per megabecquerel hours per cubic meter (MBq·h/m) (95% confidence interval: 0.3, 35) for miners with cumulative exposures below 30 MBq·h/m. Estimates of risk per unit exposure are 5.38×10 per WLM; 9.68×10/WLM for ever smokers; and 1.67×10 per WLM for never smokers.
According to the UNSCEAR modeling, based on these miner's studies, the excess relative risk from long-term residential exposure to radon at 100 Bq/m is considered to be about 0.16 (after correction for uncertainties in exposure assessment), with about a threefold factor of uncertainty higher or lower than that value.
In other words, the absence of ill effects (or even positive hormesis effects) at 100 Bq/m are compatible with the known data.
The ICPR 65 model follows the same approach, and estimates the relative lifelong risk probability of radon-induced cancer death to 1.23 × 10 per Bq/(m·year). This relative risk is a global indicator; the risk estimation is independent of sex, age, or smoking habit. Thus, if a smokers chances of dying of lung cancer are 10 times that of a nonsmokers, the relative risks for a given radon exposure will be the same according to that model, meaning that the absolute risk of a radon-generated cancer for a smoker is (implicitly) tenfold that of a nonsmoker.
The risk estimates correspond to a unit risk of approximately 3–6 × 10 per Bq/m, assuming a lifetime risk of lung cancer of 3%. This means that a person living in an average European dwelling with 50 Bq/m has a lifetime excess lung cancer risk of 1.5–3 × 10. Similarly, a person living in a dwelling with a high radon concentration of 1000 Bq/m has a lifetime excess lung cancer risk of 3–6%, implying a doubling of background lung cancer risk.
The BEIR VI model proposed by the National Academy of Sciences of the USA is more complex. It is a multiplicative model that estimates an excess risk per exposure unit. It takes into account age, elapsed time since exposure, and duration and length of exposure, and its parameters allow for taking smoking habits into account.
In the absence of other causes of death, the absolute risks of lung cancer by age 75 at usual radon concentrations of 0, 100, and 400 Bq/m would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong nonsmokers, and about 25 times greater (10%, 12%, and 16%) for cigarette smokers.
There is great uncertainty in applying risk estimates derived from studies in miners to the effects of residential radon, and direct estimates of the risks of residential radon are needed.
As with the miner data, the same confounding factor of other carcinogens such as dust applies.