Abstract
For low LET radiations, the cancer risk has been estimated mainly based on the epidemiological data of the atomic bomb survivors in Hiroshima and Nagasaki. However, the risk from neutrons cannot be directly estimated from human data since no epidemiological data is available. For the cancer risk from neutrons, the RBE of neutrons has been investigated based on experimental data by comparing with the dose response of gamma radiation. The risk estimate using such a method is influenced by uncertainty of risk estimates of gamma radiation in low dose region because the slope of the dose response curve from gamma irradiation decreases to zero. The most important issue in the neutron risk estimate is inverse dose-rate effects that show a reduced risk as dose rate increases. There are some evidence for inverse dose-rate effects in endpoints such as mutations and transformations, but mechanistic explanations are needed to estimate how carcinogenic effects are dependent upon dose and dose rate. We examined how mutagenic effects depending upon dose rate have an influence on multistage process in carcinogenesis. [J Radiat Res 44:374 (2003)]
