Cancer risk analysis of low-dose radiation exposure

Cancer risk assessment was conducted in a population that received prolonged low dose-rate γ-irradiation for about 10 years as a result of occupying buildings containing ⁶⁰Co-contaminated steel in Taiwan. The cancer risks were compared with those populations with the same temporal and geographic characteristics in Taiwan by standardized incidence ratios, adjusted for age and gender. The standardized incidence ratios were significantly higher for all leukemia except chronic lymphocytic leukemia in men, and marginally significant for thyroid cancers in women. All cancers combined were shown to exhibit significant exposure-dependent increased risks in individuals with the initial exposure before 30 years of age, but not beyond this age. Excess relative risk at 1 Sv by Cox proportional hazard model was significantly high in all cancers combined, breast cancers and leukemia, while it was marginally significant in solid cancers combined, all solid cancers combined, stomach cancers and lung cancers. The results indicated that protracted low-dose radiation could induce higher cancer risks in the general public, especially for leukemia and the risks were comparable with those of acute radiation exposure.