French population exposure to radon, terrestrial gamma and cosmic rays.

In France, natural sources account for most of the population exposure to ionising radiation. This exposure varies widely with area. Radon and gamma-ray exposure data come from national measurement campaigns; cosmic doses were calculated from city altitude. These data were corrected for season of measurement, housing characteristics and population density to study their relationship with health indicators. The crude average of indoor radon concentrations was 89 Bq m(-3), and the average corrected for season and housing characteristics was 83 Bq m(-3) (range over districts: 19-297). Weighting by district population density yielded a national average of 63 Bq m(-3). Gamma-ray dose rates averaged 55 nSv h(-1) (23-96) indoors and 46 nSv h(-1) (25-85) outdoors; corrections did not change the means. Corrected cosmic annual doses averaged 0.28 mSv (0.27-0.38). These corrections estimated the radiation exposure of the French population more accurately and represented its distribution well, thereby allowing its study as a cofactor in ecological studies.