Acute-chronic ratio (ACR) implicitly needs the assumptions that acute toxicity and chronic toxicity have a log linear relation and that the slope of the log linear regression model is one exactly. The aim of this study was to test whether this assumption is valid or not. Ecotoxicity datasets of algae, daphnia and fish were statistically analyzed by using log linear regression models. The validity of assumption was judged by the slope of the regression model that was selected based on the AIC of the models. The results showed that the assumption was valid for algae, while the assumption was not valid for daphnia and may not be valid for fish. Our results also showed that chemical structures and physicochemical properties can become effective factors which improve predictive ability of regression models.

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A tropical plant, Jatropha curcas is drawing attention as a feedstock for biodiesel production. This plant is known to be toxic when consumed and known to contain antinutrients/toxins such as trypsin inhibitor and phorbol esters (PE). Among such antinutrients/toxins, PE is highly toxic and is assumed to be the principle active component. We performed literature search of toxicological papers of seed, crude oil and PE contained in Jatropha curcus, and summarized toxicological findings available and discussed risk management measures which could be applied. As information on toxicity by inhalation route is completely lacking we could not suggest any practical risk management measures on this. As Jatropha PE is known to undergo degradation by high temperature, exposure assessment based on realistic scenarios might help us decide if bioassay is necessary, and if so, plan suitable bioassay to answer questions necessary for risk management.

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In Japanese, anshin means “peace of mind.” It has recently become important in Japan. Generally, it is supposed that anshin is related to safety, and railway companies are striving to advance their safety level and support users' anshin. However, the relationship between the subject of safety and the subject of anshin is not obvious. This paper investigates the correspondence for railway users based on a questionnaire with the assumption that anshin is explained by anxiety. As a result, it is shown that there are two ideas regarding anshin. One is that anshin is based on anxiety related to safety; the other is that anshin is based on anxiety related to users' expectations. It is important that railway companies recognize that there are two concepts of anshin, and then decide which concept to select.

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The definition of the term “safety” in the ISO/IEC Guide 51 has been revised for the first time in 15 years. The definition changed from “freedom from unacceptable risk” to “freedom from risk which is not tolerable”. However, its meaning seems to be same as the previous edition. It is clearly stated that the phrases “acceptable risk” and “tolerable risk” are synonymous in the footnote. In addition, several important changes were found in the new edition, such as the introduction of the perspective of consumers. This paper reports several implications of the revised edition to the risk community.

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In an increasingly interconnected world, risks with systemic nature spread over more than one country, more than one sector, and may have effects across technological, social and environmental system. For realizing good risk governance, it is important to better understand state and behaviors of risks emerging in complex social system, produce policy alternatives with holistic, anticipatory and balanced thinking, and deliberate on them with stakeholders before making a decision. This article describes some expectations for SRAJ's young members who would play a leading role in risk research and practices from the above-mentioned perception.

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