Risk assessment system for radiation has been well developed, so defining the radiation equivalent dose for chemical agents could place in the order of their risk. As well as the radiation, benzene causes leukemia to humans. Therefore, we evaluated the radiation equivalent dose for benzene based on its metabolites and low-dose rate radiation induced chromosome aberrations using CD34⁺ cells from human bone marrow, which is the target organ of benzene induced leukemia. As a result, we got leukemia estimates which were about thirtieth part of those evaluated by U.S.EPA based on epidemiological data. We need to accumulate much more studies in order to validate this framework, but it could be effectual as an alternative risk assessment with few animal studies.

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Probabilistic ecological risk assessment of 11 herbicides, commonly used in Japanese paddy fields was conducted. The effect assessment was based on species sensitivity distribution (SSD). The acute EC₅₀ values of standard toxicity tests for aquatic primary producers were collected from available literatures and then fitted into lognormal distributions. Predicted environmental concentration (PEC) was calculated using an environmental model defined by the Ministry of Environment, Japan. The regional variations of PEC were quantified using Monte Carlo analysis. A joint probability curve was derived by comparing SSD and PEC distribution, and the area under the curve was defined as expected potentially affected fraction (EPAF) for quantitative risk index. The highest EPAF was 6.2% for bensulfuron-methyl.

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This paper shows the relevance between concept ‘premium’ and concept ‘risk’ of the new Insurance Contract Act of Japan in the light of commercial science of insurance. First, I mention that this act has the definition clause concerning ‘insurance contract,’ which describes the ‘premium’ as ‘calculated in proportion to the probability of occurrence of such a specific cause.’ This expression may be understood to limit the insurance risk to frequency risk, but it should be understood to include severity risk. Second, I mention that the articles of this act concerning ‘risk’ should also be understood to include severity risk, because this act has the similar definition clause concerning ‘risk’ to that of ‘premium.’

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