不同评估方法得出的五氯酚的PNEC值的比较研究

Comparison of Aquatic Predicted No-Effect Concentrations ( PNECs ) for Pentachlorophenol Derived from Different Assessment Approaches

预测的无效应浓度(PNEC)是进行风险污染物水生态安全管理的重要依据,一直是水环境风险管理者研究的热点.为了比较不同评估方法对PNEC计算结果的影响,以五氯酚(PCP)的PNEC值评估为例,使用点评估、统计评估和区间评估进行PCP的PNEC值研究,并对这几种方法进行比较,同时对控制PNEC值大小的主要影响因素进行了分析.结果表明,由点评估通过急慢性毒性数据和评估因子获得的PCP的PNEC值分别为0.420μg·L-1和0.500μg·L-1,相差不大;由统计评估的probit和logit单位法获得的PCP的PNEC值分别为10.1μg·L-1和8.10μg·L-1;由区间评估获得的PNEC-L95%和PNEC-L50%的值分别为6.00μg·L-1和11.8μg·L-1,可见由统计评估和区间评估获得的PNEC值比较接近,而点评估获得的PNEC值比其它两种方法低一到两个数量级;并且毒性数据类型和统计模型对毒性数据量丰富的PCP的PNEC值的得出影响不大.因此统计评估和区间评估可以被选为数据量较丰富的化合物如PCP的PNEC值的计算方法,其结果比点评估计算出的PNEC值更具有可信度.

Predicted no-effect concentration（PNEC） is the key for ecological risk assessment and has become a focus of the study.Generally,extrapolation was used to derive PNEC values by different evaluation approaches according to results of single species toxicity test.However,PNEC values were different for the same toxicity data for the same chemicals if extrapolation methods were different.To evaluate PNEC values derived by different assessment methods,PNEC values of pentachlorophenol（PCP） were calculated using three different approaches,i.e.point estimation,statistical evaluation as well as interval evaluation.At the same time,the main factors controlling PNEC values were analyzed.The results showed that PNEC values for PCP by different assessment factors were 0.420 μg.L-1 for acute toxicity data and 0.500 μg.L-1 for chronic toxicity data,respectively.The PNEC values for PCP by statistical evaluation were 10.1 μg.L-1 for probit unit and 8.10 μg.L-1 for logit unit.The values derived by interval evaluation were 6.00 μg.L-1 for PNEC-L95%and 11.8 μg.L-1for PNEC-L50%,respectively.PNECs obtained by the point estimation were the lowest and lower one order of magnitude than the PNEC values obtained by the other two methods.The PNEC values derived by the statistical assessment and interval evaluation were very similar.In addition,toxicity data type and statistical models have little effect on PNEC value for PCP with a great body of toxicity data.The results indicated that statistical evaluation and interval evaluation methods should be selected to derive PNEC values for well-studied substances like PCP,while point estimation should be used in preliminary screening assessment of chemicals to determine whether the effect is of concern.