Development of new framework for evaluating the health risk variation and identifying the potential high risk group

近年来，由于暴露在环境中的微污染物造成的健康风险约为10^-5；可供日本参考。潜在的健康风险预计对所有人都是平等的，但实际的健康问题将在“环境高危群体”中的一些人身上检测到。本研究以大气核爆试验分布于世界各地的放射性尘埃、铅等重金属、滴滴涕等农用化学品、苯等化学物质为目标污染物，通过评价环境中污染物的外部暴露及其变化幅度来确定高危人群，建立了评价环境中污染物的膳食和呼吸途径的外暴露、人体内暴露于靶组织/器官的评价框架，以及癌症诱发等健康风险评价框架。以苯及其代谢物为研究对象，运用致癌风险数学评价模型，结合等效辐射风险因子，对苯及其代谢物诱发白血病的风险进行了评价；以日本S 70年代初全面禁用的农药滴滴涕为例，评价了参考日语中农药滴滴涕的膳食/呼吸暴露、胎盘在胚胎/胎儿体内的转移和蓄积以及人体负担随年龄的变化。该框架也应用于参考印度人。通过案例研究获得的估计值与环境介质和食品中的观察浓度很好地吻合，在人类血液、血脂和组织中也是如此。这些事实表明，所开发的框架在评估潜在的健康风险及其变化范围方面是有前景的。

The health risk due to the exposure to the micro-pollutants in an environment is at the level of 10^<-5> for reference Japanese these years. The potential health risk is to be expected equal to all persons, however the actual health problem will be detected at some persons in an "environmentally high-risk group". In this study, the external exposure to the pollutants in an environment is evaluated together with their variation range to specify the high-risk group.The fallout radionuclids, which were distributed throughout the world by the atmospheric nuclear detonation tests, heavy metals like lead, agrochemicals like DDT, and chemicals like benzene were selected as the target pollutants, and the framework was developed for evaluating the external exposure through dietary and respiratory pathways, the internal exposure to the target tissues/organs in a human body, and for evaluating the health risks like cancer induction. The case application study was practiced focusing on benzene and its metabolites to evaluate the leukemia induction risk by using the mathematical cancer risk evaluation model combined with the equivalent radiation risk factor.The case study was also practiced for agrochemicals DDT, which was banned thoroughly in first 70's in Japan, to evaluate the dietary/respiratory exposure, the transfer and accumulation in embryo/fetus through placenta, and the age-dependent variation of its body burden in reference Japanese. The framework was applied also on the reference Indians.The estimates obtained by the case studies fits well with the observed concentration in environmental media and foods, in human blood, lipids and tissues as well. These facts show that the framework developed is promising for evaluation of the potential health risk with its variation range.