Interaction of Low-Dose Radiation and Chemicals in Cancer Risk

Abstract Accurate prediction of radiation-induced cancer risk at low doses is key to addressing considerable public concern. Epidemiology data show overall cancer risk increases linearly with dose, but there is considerable heterogeneity by organ site, with some tissues refractory to cancer induction or showing an apparent threshold. The small risk posed by low-dose radiation is difficult to estimate above high background cancer rates and should be considered in the context of exposures with other environmental carcinogens, such as tobacco smoke, known to modify the relative effect of radiation on lung cancer. Animal experiments demonstrate synergy, additivity, or antagonism between radiation and other carcinogens depending on the tissue, the dose, and timing of exposures. We review here the combined effect of radiation and chemical carcinogens, focusing on low doses and our recent study on T-cell lymphoma after exposure to X-rays and N -ethyl- N -nitrosourea (ENU).