基于暴露人群内剂量响应机制的填埋场混苯健康风险研究

Landfill is a major treatment approach of municipal solid waste (MSW) in China. Fugitive volatile organic compounds (VOCs) emitted from MSW landfills contain a great amount of aromatic compounds (mixed benzene for short), including benzene, toluene, xylenes and styrene, which are greatly associated with carcinogenic or non-carcinogenic health risks. However, these risks to human health are not clear yet. According to the investigation of the project group, mixed benzene is major component of VOCs in landfill sites. The concentration of mixed benzene measures 10 to 100 times greater than that in the urban air, and thus, the health risk of mixed benzene in landfill can’t be negligible; Due to the complex conditions of landfill sites, emissions of mixed benzene are extremely random, and in addition, for lack of assessment parameters, the widely used dose-response assessment method is uncertain. In this study, based on the interaction between exposure and internal dose of mixed benzene exposure in landfill sites, a novel risk assessment method is carried out, in which the health risk is quantitatively analyzed. The theory of probability is introduced to solve the emission of mixed benzene in a quantitative way. What’s more, biomonitoring is applied to trace the metabolism of mixed benzene in human bodies, and the response of exposure level and internal dose is revealed. Furthermore, a risk assessment model based on exposure-internal dose-response effect is developed, and combined with Monte Carlo method, the model for the treatment of uncertainty is realized. Finally, the approach is applied to calculating exposure risks of occupational groups and residents nearby, thus benefiting the control and risk management of landfill sites.

填埋是我国生活垃圾主要处置方式。生活垃圾填埋场无组织释放挥发性有机物（VOCs）中包含大量具有高致癌或非致癌健康风险的苯系混合物（简称混苯），包括苯、甲苯、二甲苯、苯乙烯等。项目组前期发现混苯是填埋场释放VOCs的重要组成，其浓度比城市空气中高出1-2个数量级，健康风险不容忽视；由于填埋场环境复杂、混苯释放随机性强波动大，基于传统剂量-效应模式使用外暴露量进行风险评价时，存在不确定性强、准确度低的问题。本研究提出基于外暴露-内剂量响应特征的混苯暴露健康风险定量化评价模型。拟采用概率性方法量化混苯释放源强和外暴露量；追踪混苯暴露人群的生物标志物获得内剂量水平，揭示人体内剂量与外暴露水平的响应特征，以内剂量为桥梁，构建外暴露-内剂量-生物效应耦合评价模型，进而结合蒙特卡洛模拟方法实现风险评价不确定性的量化解析，最终为填埋场污染风险管理和控制决策提供科学方法和理论依据。

生活垃圾填埋场无组织释放的苯系混合物（简称混苯）包含高致癌或非致癌物质，填埋场工人的职业暴露健康风险不容忽视。基于此本项目提出，基于人体外暴露与内剂量响应的填埋场混苯暴露健康风险研究思路，通过实验室模拟与现场监测相结合的方式明确了混苯释放特征，利用概率学方法等构建了填埋场混苯外暴露特征剂量，建立了混苯生物标志物的同步检测方法，明确了职业人群混苯内剂量水平特征，解析了外暴露-内剂量响应机制，建立了基于BP神经网络的混苯外暴露-内剂量响应模型，量化了填埋场混苯职业暴露健康风险。.通过实验室模拟与为期2年的现场监测，苯是混苯中最主要的贡献物，填埋场填埋场作业区与覆盖区混苯浓度水平分别为0.07-3.55μg/m3 和0.48-67.33mg/m3，填埋场混苯释放呈现冬夏高春秋低的趋势，基于概率密度函数解析了混苯释放特征，填埋场职业人群混苯外暴露浓度典型值为255.78μg/m3。构建了混苯人体尿液生物标志物同步快速定性定量检测方法。填埋场职业暴露会导致内剂量水平显著提高，其中暴露组中苯的内剂量水平班后较班前升高了约72.59%。对比填埋场职业暴露混苯生物标志物标的内剂量水平和相关限值，tt-MA的水平约为其ACGIH的BEI限值（0.5mg/gCre）的4.66倍。相关性分析结果显示，职业暴露人群外暴露与内剂量线性相关性低，因此建立了基于BP神经网络的混苯外暴露-内剂量响应模型，仿真结果较好，并提出了填埋场混苯职业暴露限值。研究发现仅基于外暴露的健康风险评估可能会低估填埋场的职业暴露风险。研究成果可为我国生活垃圾填埋场污染污染物风险管理和控制提供政策建议和理论支撑。