Vol.1 No.1 2008

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Research paper : A strategic approach for comparing different types of health risks (A. Kishimoto)−35−Synthesiology - English edition Vol.1 No.1 (2008) 3 (HUI 3), a multiple attribute utility scale which is often used in the medical field [6]. HUI3 has eight attributes: vision, hearing, speech, ambulation, dexterity, emotion, cognition, and pain. Each attribute has five or six levels. This means that, theoretically, total 972,000 health conditions can be assessed using HU13. The health risks for all residents in Japan from exposure to toluene were finally quantified as the loss of 197 years per annum, as shown in Table 1. If similar procedures were applied to other chemical substances or other kinds of risks, we could quantitatively compare their amounts of risk and would be able to allocate resources more rationally.3.6 Cost effectiveness of risk reduction measuresSince atmospheric modeling and dose response functions clarified the linkage from emission sources to human health risks, we could simulate the health benefits of introducing emission control measures at the sources and express them as “QALYs gained”. By estimating the annual costs of emission control measures, “cost per QALY gained” could be calculated by dividing costs by the QALYs gained. In this study, we calculated the cost-effectiveness in the case where 10 % of the total emission volume of toluene reported to the PRTR was reduced by installing Regenerative Thermal Oxidizers (RTOs). The cost per QALY gained was calculated to be approximately 1.6 years. Since it costs about JPY 33,000 to 100,000 to reduce 1 ton of toluene using RTOs (100,000 to 7,500 Nm3/hr), it costs JPY 430 million to 1.3 billion annually to reduce 13,000 tons (10 % of emission volumes reported to the PRTR). Therefore, the “cost per QALY gained” was estimated to be approximately JPY 270 to 810 million. This indicator of cost-effectiveness can be used to prioritize risk reduction measures for various types of hazards other than chemical substances, such as infectious diseases, accidents, and natural disasters.4 DiscussionThe conventional method of risk assessment was originally created by combining elemental techniques that were developed by casting back from social demands to set environmental standards or to conduct screening-level risk assessment. These elemental techniques were established as standard techniques of risk assessment practices, and were respected as academic fields with their own experts. Therefore, when new social demands for risk assessment arise, experts of each elemental technique are expected to apply the existing methods without modification. Since the users of risk assessments are usually not experts, they cannot examine the methodologies of each elemental technique. Once the technology is established as a discipline, it evolves independently. However, leading-edge research does not necessarily satisfy new social demands. There is no guarantee that a necessary elemental technique that may fulfill new social demands will emerge endogenously from academic fields.In this research, we sought the most suitable methods and revised each elemental technique to fulfill new social demands, i.e. different types of risks were compared and priorities were set based on cost effectiveness. We are aware that some of the assumptions lack firm foundations from an expert standpoint. Although these issues must be resolved, it is also important to accurately explain future research requirements to experts of the disciplines. We must also demonstrate that the methodology presented in this paper can be applied to other chemical substances and other types of risks. Fig. 5 Dose response relationships of subjective symptomsTable 1. Annual loss of QALYs resulting from exposure to toluene in JapanInability to concentrateLoss in hearing capacityDifficulty in speechReduced sense of smellReduced sense of tasteRough skinReduced muscle strengthin extremitiesUnusual feeling in throat18080100120140160020406002010515253035Exposure level [mg/m3]Incidence rate [%]1592810197Indoor sourcesMobile and low-emission sourcesHigh-emission facilities TotalLoss of QALYs (years)

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