Commentary on information that can be drawn from studies of areas with high levels of natural radiation

Studies of the health of populations living in areas of high levels (HL) of natural radiation are a potentially important source of information on the effects of chronic low-dose rate exposures to ionising radiation. The current paper presents a brief overview of the status of studies in Brazil, China, India, and Iran. At present, only limited information on health risks can be drawn. Issues of concern in the interpretation of the studies are discussed, and recommendations are made to improve the informativeness of studies in the future. Where feasible, the conduct of analytical epidemiological studies-in particular, case control studies-with individual estimates of doses to specific organs from internal and external exposures and with individual information on known and possible risk factors for the diseases of interest should provide important information on health risks from low-level chronic radiation exposures. This information can be maximised by the adoption of common study protocols and common dosimetric approaches and by coordination of efforts across countries.