Abstract :
A great deal is known about the cancer risk of high radiation doses from studies of Japanese A-bomb survivors, patients exposed for medical therapy, occupational exposures, etc. But the vast majority of important applications deal with much lower doses, usually accumulated at much lower dose rates, referred to as ʹlow-level radiationʹ (LLR). Conventionally, the cancer risk from LLR lias been estimated by the use of linear no-threshold theory (LNT). For example, it is assumed that tile cancer risk from 0.001 Sr (100 mrem) of dose is 0-001 times the risk from I Sv (100 rem), in recent years, the former risk estimates have often been reduced hy a ʹdose and dose rate reduction factorʹ, which is taken to he a factor of 2. But otherwise, the LNT is frequently used for doses as low as one hundredthousandth of those for which there is direct evidence of cancer induction hy radiation. It is the origin of the commonly used expression ʹno level of radiation is safeʹ and the consequent public fear of LLR. The importance of this use of the LNT can not he exaggerated and is used in many applications in the nuclear industry. The LNT paradigm lias also been carried over to chemical carcinogens, leading to severe restrictions on use of cleaning fluids, organic chemicals, pesticides, etc. If the LNT were abandoned for radiation, it would probably also he abandoned for chemical carcinogens. In view of these facts, it is important to consider the validity of tlie LNT. That is the purpose of this paper.
