The cancer risk from low-level radiation.

INTRODUCTION. It is commonly stated that " any radiation dose, no matter how small, can cause cancer ". The basis for that statement is the linear-no threshold theory (LNT) of radiation carcinogenesis. According to LNT, if 1 Gy (100 rads) of exposure gives a cancer risk R, the risk from 0.01 Gy (1 rad) of exposure is R/100, the risk from 0.00001 Gy (1 millirad) is R/ 100,000, and so on. Thus the cancer risk is not zero regardless of how small the exposure. However, over the past several years, a strong sentiment has developed in the community of radiation health scientists to regard risk estimates in the low-dose region based on LNT as being grossly exaggerated or completely negligible. For example, the 6000 member Health Physics Society, the principal organization for radiation protection scientists, issued a position paper (HPS 1996) stating " Below 10 rad ….risks of health effects are either too small to be observed or are non-existent ". A similar position statement was issued by American Nuclear Society. When the Health Physics Society Newsletter asked for submission of comments on validity of LNT, there were about 20 negative comments submitted and only a single comment supportive of LNT. In a worldwide poll conducted by the principal on-line discussion group of radiation protection professionals (RADSAFE), the vote was 118 to 12 against LNT A 2001 Report by the French Academy of Medicine concluded that LNT is " without any scientific validity, and an elaborate joint study by the French Academy of Medicine and the French Academy of Sciences (Aurengo et al 2005) strongly condemned the use of LNT. " Few experimental studies and essentially no human data can be said to prove or even provide direct support for the [LNT] concept " , and in NCRP Publication No.136 (NCRP-2001) stated " It is important to note that the rates of cancer in most populations exposed to low level radiation have not been found to be detectably increased, and in most cases the rates appear to be decreased ". A group of scientists opposing use of LNT (Radiation Science and Health) submitted several hundred papers supporting their position to National Research Council. Beyond failure of LNT, there is substantial evidence that low level radiation may be protective against cancer; a view known as " hormesis ". There is an International Hormesis Society which sponsors an annual International Scientific Conference …