Measurement of ambient benzene and human health assessment

对整个日本人口的环境苯致癌风险进行了评估。为了预测环境苯含量，使用了在日本各地设置的大量监测站测量的氮氧化物（NOx）含量。1997年5月至1998年11月在横滨国立大学进行了连续监测实验，研究了环境苯与氮氧化物浓度之间的关系。作为监测结果，在NOx水平（X以ppb为单位）和苯水平（Y以μ g/m^3为单位）之间获得了具有高相关系数（R^2 = 0.73）的回归方程Y = 0.18 X 0.81。这一结果表明，环境NOx监测数据可以用于可靠的预测环境苯水平在日本，环境中的NOx水平已被精确地监测，并在全国1461个一般空气污染监测站和382个汽车尾气监测站附近的主要道路上记录了其小时平均值。对每个监测站代表的人口进行了暴露分析，估计整个人口的人口加权平均苯含量为3.2微克/立方米，估计47%的人口暴露于高于环境质量标准3微克/立方米的苯。根据EPA癌症单位风险，确定了环境苯暴露导致的过量癌症风险的分布。我们的研究结果表明，整个人口中约有79%的人一生中暴露于1 × 10^或更高的癌症风险水平<-5>，由于一年暴露于苯而导致的额外终生癌症风险估计约为30例。通过降低汽油中苯含量的对策，每年每挽救一个生命的成本估计约为30亿日元。

The population cancer risk due to ambient benzene was evaluated for the entire Japanese population. For predicting ambient benzene levels, nitrogen oxide (NOx) levels measured at a large number of monitoring stations set throughout Japan were used. The relationships between ambient benzene and Nox levels were investigated by continuous monitoring experiment at the Yokohama National University from May, 1997 to November, 1998. As a result of monitoring, the regression equation, Y = 0.18 X 0.81, was obtained between NOx levels (X in ppb) and benzene levels (Y in mu g/m^3) with a high correlation coefficient (R^2 = 0.73). This result indicates that ambient NOx monitoring data can be used for reliable prediction of ambient benzene levelIn Japan, NOx levels in the ambient environment have been precisely monitored and their hourly average values have been recorded at 1461 general air pollution monitoring stations nationwide and at 382 automobile exhaust monitoring stations adjacent to major roads. Exposure analysis was performed considering the population represented by each monitoring station.The population weighted average benzene levels were estimated to be 3.2 mu g/m^3 for the entire population, and 47 percent of the entire population was estimated to be exposed to benzene at a level above the Environmental Quality Standard level of 3 mu g/m^3. The distribution of excess cancer risk due to exposure to ambient benzene was established based on the EPA cancer unit risk. Our results indicated that about 79 percent of the entire population was exposed to a lifetime cancer risk level of 1 x 10^<-5> or greater, and the excess lifetime cancer risk due to one-year-exposure to benzene was estimated to be about 30 cases. The cost per one life saved per year by countermeasure that reduces benzene content in gasoline was estimated to be bout 3 billion yen.