Effects of low doses and low dose rates of external ionizing radiation.

This letter refers to a recent study reported in Radiation Research on the above subject by Cardis et al. (1). In view of the uncertainties and wide differences of opinions on the possible health effects of low-level exposures, the analysis of the pooled data from three countries is a very timely and commendable effort. However, we feel that there is a significant discrepancy between the data presented and the conclusions therein for the reasons given below. 1. A plot of the data given in Table III of the paper by Cardis et al. (see Fig. 1) does not indicate an increasing trend for any cancer including leukemia up to 200+ mSv except for multiple myeloma. The positive trends mentioned in their paper for all leukemia and all except chronic lymphatic leukemia (CLL) have come about only because of the data for 400+ mSv. If one excludes these