Some considerations for comparing risk of radiation and chemicals

Some basic concepts, used in radiation protection, are tried to be applied to the assessment of risks of environmental chemicals with the necessary variations. Dioxins may serve as an intermedium for the comparison of radiation and other chemicals. The death risk of dioxin induced cancers in life is 4.7x10-4, based on the intake of 1 pg/kg/day by using additive model and extrapolating linearly the results of the epidemiological study. And the risk is 2.6x10-4 in life by multiplicative model. The death risk of radiation induced cancer is 4x10-5/a to the effective dose of 1 mSv/a for adult. Ingestion of 1 Bq of 239Pu will give rise to a committed effective dose of 2.5x10-7 Sv, therefore, yearly ingestion of 1.47x10-6 g of 239Pu is corresponding to 1 mSv/a. A definition of risk per year over mass ingested per year (1/μg) may be suitable for the comparison of yearly risk of yearly-ingested masses of dioxins and 239Pu. The life expectancy and a reference body weight (averaged weights of man and woman adults) are chosen as 70 years and 64 kg respectively. The risks caused by ingestion of unit mass dioxin and 239Pu are given as follows: 2.87x10-4/μg (2,3,7,8-TCDD, additive model), 1.69x10-4/μg (2,3,7,8-TCDD, multiplicative model) and 2.3x10-5/μg (239Pu). These results show that dioxins are even riskier. The comparison among dioxins and other chemicals may be relatively easier. (author)