ADULT MYELOID-LEUKEMIA, GEOLOGY, AND DOMESTIC EXPOSURE TO RADON AND GAMMA-RADIATION - A CASE-CONTROL STUDY IN CENTRAL ITALY

Objectives-To investigate whether indoor radon or gamma radiation migh t play a part in myeloid leukaemia as suggested by studies based on cr ude geographical or geological data for exposure assessment. Methods-F or six months radon and gamma radiation was measured with solid state nuclear track detectors and thermoluminescent dosimeters in dwellings of 44 adult male cases of acute myeloid leukaemia and 211 controls (al l subjects deceased). Conditional logistic regression ORs (ORs) and 95 % confidence intervals (95% CIs) were estimated for quartiles of radon and gamma radiation and for municipality and dwelling characteristics . Results-The risk of leukaemia was associated with an increasing urba nisation index (p value for trend=0.008). An increased OR was found am ong those Living in more modern houses (OR 3.0, 95% CI 1.4 to 6.6). Co nfirming the findings of a previous study in the same area, geological features bore a positive association with myeloid leukemia, even by a djusting for level of urbanisation. Contrary to expectations from the previous study, however, no association appeared between myeloid leuka emia and radon and gamma radiation; for the highest quartiles of expos ure, ORs were 0.56 (95% CI 0.2 to 1.4) and 0.52 (95% CI 0.2 to 1.4), r espectively. Considering only subjects who had lived greater than or e qual to 20 years in the monitored home and adjusting for urbanisation, there was still no effect of exposure to radiation. Conclusions-In vi ew of the limited numbers, the results do not in general refute a poss ible risk of myeloid leukaemia from exposure to indoor radon or gamma radiation, but decrease the credibility of such a relation in the area studied and also of other studies suggesting an effect without monito ring indoor radiation. Some other fairly strong determinants have appe ared-that is, level of urbanisation and living in modern houses-that m ight need further consideration.