南方某城市大型水厂出厂水有机污染物混合暴露的健康风险评估

Health risk assessment of exposure to mixtures of organic pollutants in finished water in a large drinking water treatment plant from a city in southern China XUE Panqi1a,1b,1c,YIN

[背景]有机污染严重威胁生活饮用水水质,人群长期低剂量混合暴露于饮用水有机污染物存在极大的健康隐患。[目的]调查位于长江入海口的南方某城市某一大型水厂出厂水中多氯联苯(PCBs)、多环芳烃(PAHs)、有机氯农药(OCPs)和邻苯二甲酸酯(PAEs)这4类共69种有机物污染状况,并进行混合暴露健康风险评估。[方法]2018年9月采集水厂出厂水400 L,采用固相萃取技术富集水样中有机物,通过气相色谱质谱联用仪定量分析PCBs、PAHs、OCPs和PAEs这4类有机污染物浓度水平,采用美国环境保护署(EPA)推荐的风险评估方法对出厂水中检出的单个有机物和混合暴露进行非致癌和致癌风险评估。[结果]在出厂水中检出6种PAEs类物质、6种PAHs类物质,5种OCPs类物质和1种PCBs类物质,总质量浓度(后称浓度)为477.28 ng·L^(-1),单一物质浓度范围为0.02~278.21 ng·L^(-1),4类物质浓度排序如下:PAEs>OCPs>PAHs>PCBs。对3类11种有机物进行非致癌风险评估,在集中趋势暴露(CTE)和合理最大暴露(RME)两种暴露场景下,各年龄段的各类有机物混合暴露非致癌总风险分别处于10^(-5)、10^(-4)水平,均远低于1.0,风险处于可接受水平。PCB167、[艹屈]、萘、滴滴滴、β-六六六、邻苯二甲酸-2-乙基乙酯6种检出有机物致癌风险评估显示:CTE场景下混合暴露的终生总致癌风险(7.11×10^(-7))处于美国EPA推荐的可忽视水平(<10^(-6));RME场景下终生总致癌风险(2.18×10^(-6))超过10^(-6),介于可接受风险水平(10^(-6)~10^(-4)),其中风险最高的是β-六六六(1.67×10^(-6)),占终生总致癌风险的76.43%;经口摄入和皮肤接触是目标物致癌风险的主要暴露途径。[结论]该水厂出厂水存在一定程度的有机物污染,其中纳入美国EPA和我国饮用水水质标准的目标物均未超标。出厂水中有机物混合暴露的终生总致癌风险超过可忽视水平,有机氯农药β-六六六贡献率最高,虽处于可接受的风险范围,但不可忽视终生暴露于该水厂出厂水可能存在的致癌风险。

[Background]Serious organic pollution in aquatic environments threatens the quality of drinking water.Long-term low-dose exposure to multiple organic pollutants in drinking water poses potential hazards to human health.[Objective]This study investigates the pollution of 69 organic compounds in four categoriesincluding polychlorinated biphenyls(PCBs),polycyclic aromatic hydrocarbons(PAHs),organochlorine pesticides(OCPs),and phthalate esters(PAEs)in finished water from a large drinking water treatment plant in a southern city at the estuary of the Yangtze River,and evaluate potential health risk of exposure to mixtures of organic pollutants.[Methods]Finished water samples from selected large drinking water treatment plant were collected.Solid-phase extraction and gas chromatography-mass spectrometry(GC-MS)were used to enrich and quantify the levels of organic pollutants in water samples,including PCBs,PAHs,OCPs,and PAEs.Non-carcinogenic and carcinogenic risks of exposure to individual organic compounds and mixtures were evaluated by health risk assessment method recommended by U.S.Environmental Protection Agency(EPA).[Results]In the finished water samples,6 PAEs,6 PAHs,5 OCPs,and 1 PCB were detected.The total concentration was 477.28 ng·L^(-1),the concentrations of individual chemicals were in the range of 0.02-278.21 ng·L^(-1),and the concentrations of the four categories of chemicals were ranked as follows:PAEs>OCPs>PAHs>PCBs.This study assessed the non-carcinogenic risks of 11 detected chemicals in three categories.Under the central tendency exposure(CTE)and reasonable maximum exposure(RME)scenarios,the non-carcinogenic risks of exposure to mixtures of organic pollutants in each age group were at the levels of 10^(-5) and 10^(-4),respectively,both much lower than 1.0,indicating an acceptable risk level.The carcinogenic risk assessment was performed on 6 detected organic substances,including 2,3’,4,4’,5,5’-hexachlorobiphenyl(PCB167),chrysene(Chy),naphthalene(Nap),p,p’-dichlorodiphenyl dichloroethane(TDE),β-benzenehexachloride(β-BHC),and bis(2-ethylhexyl)phthalate(DEHP).Under the CTE scenario,the lifetime carcinogenic risk of exposure to mixtures of organic pollutants(7.11×10^(-7))was below the negligible risk level(<10^(-6))recommended by U.S.EPA.Under the RME scenario,the lifetime carcinogenic risk(2.18×10^(-6))was at the acceptable risk level(10^(-6)-10^(-4));the lifetime carcinogenic risk ofβ-BHC(1.67×10^(-6))was the highest among the 6 chemicals,accounting for 76.34%of the total lifetime carcinogenic risk.Moreover,oral ingestion and dermal contact were the two main exposure routes for the estimated carcinogenic risks of selected organic substances.[Conclusion]Organic pollution exists in the finished water in the selected water plant,and the detected chemicals do not exceed the limits in U.S.EPA and China’s drinking water quality standards.The lifetime carcinogenic risk of exposure to mixtures of organic pollutants in the finished water exceed the negligible risk level,andβ-BHC is the major contributor.Although the carcinogenic risk is at the acceptable risk level,the potential carcinogenic risk from life-long exposure to the finished water should not be neglected.