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Research paper : A strategic approach for comparing different types of health risks (A. Kishimoto)−36−Synthesiology - English edition Vol.1 No.1 (2008) Users of risk assessment, or risk managers, must convey the social demands or prescribe the methods of risk assessment to the risk assessment community to ensure that the risk assessment methodology can fulfill newest social demands. Although risk assessment is an interdisciplinary field, this does not mean that it is sufficient to combine works from different fields. We must make sure that each step of risk assessment is consistent, with the goal of fulfilling the given social demands.References[1][2][3][4][5][6]J. Nakanishi and A. Kishimoto: Shosai risuku hyokasho sirizu 3:toruen (Risk Assessment Document Series 3: Toluene), Maruzen, Tokyo (2005) (in Japanese).H. Higashino, K. Inoue, K. Mita, H. Shinozaki and H. Yoshikado: Bakuro・risuku hyoka taiki kakusan moderu (ADMER) zenkokuban no kaihatsu to kensho, kankyo kanri (Development and verification of the nationwide version of the atmospheric dispersion model for exposure and risk assessment (ADMER)), Kankyokanri, 40, 58-66 (2004) (in Japanese).Ministry of Health and Welfare: Kyojyu kankyochu no kihatsusei yuki kago butsu no zenkoku jittai chosa ni tsuite (Nationwide survey on the concentrations of volatile organic compounds in the residential environment), (1999) (in Japanese). M. Shiotsu, S. Yoshizawa, K. Ikeda, and A. Nozaki: Seikatsu jikan ni yoru okunai taizai jikanryo to katsudoryo: shitsunai kuki osen busshitsu ni taisuru bakuroryo hyoka ni kansuru kisoteki kenkyu sono 1 (Survey on human activity patterns according to time and place: basic research on the exposure dose to indoor air pollutants, Part 1), J. Archit. Plann. Environ. 511, 45-52 (1998) (in Japanese).H. Ukai, T. Watanabe, H. Nakatsuka, T. Satoh, S. J. Liu, X. Qiao, H. Yin, C. Jin, G. L. Li, and M. Ikeda: Dose-dependent increase in subjective symptoms among toluene-exposed workers, Environ. Res. 60(2), 274-289 (1993). D. Feeny, F. Furlong, M. Boyle and G.W. Torrance: Multi-attribute health status classification systems: Health utilities index, PharmacoEconomics, 7(6), 490-502(1995).Received original manuscript September 19, 2007Revisions received November 16, 2007Accepted November 16, 2007AuthorAtsuo KishimotoAtsuo Kishimoto is a senior researcher of the Research Center for Chemical Risk Management of AIST. He obtained his Ph.D. in economics from Kyoto Univerisity, and joined the National Institute for Resources and Environment as a researcher in April 1998. He is the coauthor and coeditor of “Kankyo risuku manejimento hando bukku (Handbook of Environmental Risk Management)”(Asakura, 2003) and the coauthor of “Shosai risuku hyokasyo shirizu 3 toruen (Risk Assessment Document Series 3: Toluene)”(Maruzen, 2005).Discussion with reviewers1 The relationship between QALYs and healthy life expectancyComment and question (Akira Ono)It is significant that different kinds of risks were assessed using common metric of loss of life years to enable comparison of the risks. Until now, discussions about the risk tended to be unrealistic such as, “it is absolutely safe” or “accidents never happen,” but the application of QALYs to the risk assessment will enable reasonable judgments about risks and more flexible response to risks. What is the relationship between the QALY as described in this paper and the so-called “healthy life expectancy?”Answer (Atsuo Kishimoto)“Healthy life expectancy” indicates the expected years of life in good or fairly good health, which correspond to the period when the QOL is not far from 1 in Figure 3. In other words, the QOL during period with illness or disability is considered to be virtually 0. In contrast, in the usual concept of “life expectancy,” the QOL for the entire period of life is implicitly considered to be 1. The concept of QALYs is positioned between “life expectancy” and “healthy life expectancy,” and reflects the health status most accurately. 2 Comparability with other types of risksQuestion (Akira Ono)Is it possible to apply the proposed methodology to accident risks, such as nuclear plant accidents caused by earthquakes, and compare these risks quantitatively with chemical substances? Is it possible to apply it to international risks such as for avian flu, or global risks such as climate change?Answer (Atsuo Kishimoto)Since QALYs are indicators that combine mortality effects (loss of life years) and morbidity effects (loss of QOL), it is applicable to almost all human health risks, including ones caused by nuclear plant accidents. In conventional risk assessment procedures, health risks are estimated according to worst-case scenarios. Since the extent of conservativeness in these different risks varies, it is difficult to compare them. The features of the proposed methodology are: 1) risks are expressed using the common metric of QALYs, and 2) risks are estimated as central tendency estimates, i.e. expected values. When these two conditions are satisfied, any risks are comparable to each other. Although it can also be applied to international risks, it seems to me that the issue of who will be the most affected will become the more important point than the aggregate risk values. The application of QALYs to intergenerational issues such as climate change remains to be discussed.3 Uncertainty in the number of QALYsComment (Akira Ono)I think that the work of making the scenarios for fulfilling new social demands, from top to bottom in Figure 2 was the key to this research. In doing so, it became gradually clear, that the existing elemental techniques must be revised or replaced by new Term 1.Term 2.The value is larger than 95 % of the measured values.Percent change in incidence rate of health effects due to intake of chemical substances.Terminology

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