effective dose from 222Rn-decay products to 220Rn-decay products equals 4.5 to 1; for comparison, the corresponding value for the dwellings in the United Kingdom is 7 to 1.
5.3. POTENTIAL HEALTH EFFECTS
At present an extensive discussion is ongoing in the Hong Kong media about the potentially elevated risk of residents for lung cancer induction due to high radon levels in the area,
Based on the pulmonary data from the pilot survey the average exposure to radon decay products in Hong Kong amounts to 0.22 Working Level Months per year. Two approaches are used to quantify the lung cancer risk:
a) the relative risk model with a risk coefficient ranging from 0.6 %/WLM to 2.4%/WLM. This model assumes that the risk for lung cancer induction due to radon decay product inhalation is proportional to the total baseline incidence rate of lung cancer in the Hong Kong population. Provided that this is a valid assumption about 13 % (range: 6 % to 23%) of all lung cancer deaths can be attributed to radon exposure. Since the presently reported total number of lung cancer cases is about 2500/year in the Hong Kong area, an estimated 150 to 600 cases are due to radon. This approach takes into account age- and sex dependence, as well as potential synergism between radon inhalation and cigarette smoking;
b) the ICRP-recommended risk factor for radon-induced lung cancer is 230x10-6/WLM. Using the exposure data from the pilot-type surveys and a population size of 5.9 million inhabitants, more than 300 lung cancer cases per year could be due to radon inhalation in the Hong Kong area.
6. TOPICS SUGGESTED FOR FURTHER WORK
6.1. QUALITY ASSURANCE PROGRAMME FOR RADON SYSTEMS
Currently system calibration is conducted by using reference sources for the PYLON-radon/working level meter and the E-PERM electret radon detectors. However, all analytical methods used, e.g. for radon exhalation measurements, need to be verified, preferably by participating in a regional/international
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