Verification of the effect on risk due to reduction of benzene discharge

The time course of ambient benzene level and benzene discharge was investigated. Data obtained by continuous monitoring and monthly monitoring showed a decreasing trend of ambient benzene level. The rate of decrease was around 22–25% per two years from FY 1997 to FY 1999. The discharge data of benzene reported by several organizations were collected and re-arranged to estimate the total discharge in Japan. The total amount of benzene discharged decreased by 25% from 1997 to 1999. Risk reduction due to the regulation of benzene content in gasoline as predicted in our previous report was verified by the obtained data.