2种毒性评估方法对PAHs污染场地人体健康风险的比较研究

毒性评估是人体健康风险评价的重要部分,目前主要存在2种方法,一种基于PAHs相对于苯并a]芘(BaP)的毒性当量因子,采用Ba P致癌斜率因子参数(方法 1),另一种直接采用各PAHs致癌斜率因子和非致癌参考剂量等参数(方法 2)。然而2种毒性评估方法得到的风险及修复量是否存在差异以及引起差异的原因等问题鲜有讨论。针对苏南某焦化厂PAHs污染土壤,采用分层土壤健康风险评价模型,对比了2种毒性评估方法确定的PAHs风险、修复目标污染物及土方量的差异,并对引起差异的关键因素进行探讨。结果表明:对于0.0~1.0 m表层土壤,方法 1和方法 2确定的致癌风险最大值分别1.48E-05和1.32E-05,均超过可接受致癌风险,修复土方量分别为27 846 m~3和28 667 m3,修复目标污染物均为Ba P和二苊烃(Acy)。对于1.0~3.0 m深层土壤,方法 1确定的致癌风险最大值为3.36E-08,低于可接受致癌风险,不需要修复;而方法 2确定的致癌风险最大值为3.73E-04,非致癌危害指数最大值为6.96E+01,分别超过可接受致癌风险和非致癌危害商,需要修复,修复目标污染物为萘(NaP),修复土方量为35 944 m~3。最终,方法 2确定的总修复土方量(64 611 m~3)为方法 1确定土方量(27 846 m~3)的2.45倍,而这种差异主要是由于方法 1低估了深层土壤中高挥发性PAH单体尤其是NaP的风险所致。因此,从保守角度建议采用方法 2进行PAHs风险评价。

A Comparative Study of Two Toxicity Evaluation Methods on Human Health Risks in a PAHs Contaminated Site

Toxicity evaluation is an important part in human health risk assessment. Two methods were most used for toxicity evaluation: 1) method one (method 1) uses BaP carcinogenic slope factor as indicator after converting PAHs to BaP equivalents; 2) method two (method 2) directly utilizes parameters related to PAHs such as PAHs carcinogenic slope factors and PAHs non-carcinogenic reference doses. However, during PAHs human health risks calculation process, little study has been done about the differences between the above methods. Layered soil health risk assessment models using both method 1 and method 2 were conducted in a PAHs contaminated coking plant in the south of Jiangsu Province. PAHs risks, remediation pollutants and volumes were compared, and the key factors causing the above differences were discussed. Results showed that with methods 1 and 2, the maximum carcinogenic risks and remediation volumes for surface soils within 1.0 m depth were 1.48E-05 and 1.32E-05, 27 846 m3 and 28 667 m3 respectively, and the remediation pollutants were BaP and Acy. For soils within 1.0~3.0 m depth, the maximum carcinogenic risk calculated by method 1 was 3.36E-08, indicating no need to repair; however, the maximum carcinogenic risk and non-carcinogenic hazard index calculated by method 2 were 3.73E-04 and 6.96E+01 respectively, and the remediation volumes were 35 944 m3 with Nap as major remediation pollutant. Overall, the total remediation volumes 64 611 m3 calculated with method 1 is 2.45 times more than that of 27 846 m3 calculated with method 2, since method 1 underestimated the risks of high volatile PAHs especially NaP in deep soils. Therefore, method 2 should be recommended in PAHs health risks assessment from the conservative perspective.