[Application and benefit evaluation of tiered health risk assessment approach on site contaminated by benzene].

The procedures of implementing tiered health risk assessment approach were introduced in detail, and took a large-scale site polluted by benzene in Beijing as an example, the difference on the remediation target of benzene in soil, as well as the corresponding soil remediation volume and costs, were compared. The results indicate that the benzene concentration in soil within 1.5 m in depth and the one below should be remediated to 0.26 mg x kg(-1) and 0.15 mg x kg(-1), respectively, in order to keep the cumulative carcinogenic health risk below 1 x 10(-6) based on tiered II assessment. However, according to tiered III assessment result, which is based on the benzene in soil gas within the contaminated areas in the investigated site, the soil in the corresponding depth should only be remediated to 2.6 mg x kg(-1) and 1.5 mg x kg(-1), respectively. That means the soil remediation volume delimited on tiered III assessment result is less than the one on tiered II by 139 537 m3 and the corresponding remediation costs will be reduced by 57 million Yuan, meaning the enormous economic benefits compared to the costs (around 100 thousands Yuan) spent to carry out tiered III assessment in the site.