十溴二苯乙烷的人群暴露评估及长期暴露的肝脏毒性效应研究

As a novel brominated flame retardants (BFRs), decabromodiphenyl ethane (DBDPE) has become the most popular novel BFR in China after the legacy BFRs (i.e. PBDEs) were listed as persistent organic pollutants and phased out. In our former study, levels of DBDPE in foods collected from various areas of China were found to be higher than those of the legacy BFRs, indicating that contamination levels of DBDPE has outperformed the other currently used BFRs in China. However, the exposure characteristics of DBDPE are still unknown. Previous studies found that liver is the major target organ of DBDPE, whereas the liver toxicity of DBDPE need to be further investigated. In this project, three research sites, including DBDPE manufacturing plant, high polluted area and background area, will be included into investigation. Cohort studies will be employed to evaluate the exposure characteristics of Chinese population to DBDPE. Three cohorts, occupational population cohort, highly exposure population cohort and background exposure population cohort, will be established, and annual follow-up field studies will be performed by three years. During the field studies, serum and urine of the participants, air of workplace, foods, indoor and outdoor dust will be collected and tested. Based on DBDPE levels in these samples, the internal exposure level and external exposure level (via air of workplace, foods and dust) of the target cohorts can be assessed. In addtion, the correlation between exposure level of DBDPE and liver dysfunction parameters of the participants will also be studied. Furthermore, in order to evaluate the liver toxicity upon long-term exposure of DBDPE, a cell model and experimental animal model will be developed to simulate the exposure mode of the three cohorts. The exposure dose in cell experiment and animal experiment will be calculated by the exposure levels of the cohorts. Based on the results of the cohort study, cell experiment and animal experiment, the body burden, exposure estimation and health effect of DBDPE for Chinese population would be evaluated. The result of this project will benefit the prevention and control of pollution of DBDPE.

十溴二苯乙烷（DBDPE）作为新型溴系阻燃剂，在多溴联苯醚等传统溴系阻燃剂作为持久性有机污染物禁用后被迅速推广。现有研究表明肝脏是其主要靶器官，但肝毒性效应有待深入研究。课题组前期则发现DBDPE在食品等基质中含量已超过传统溴系阻燃剂，但人群暴露状况尚未明确。本课题拟以DBDPE生产厂、高污染地区和背景污染地区为研究现场，建立职业暴露人群、高污染区人群和背景区人群队列，开展连续三年现场研究，监测血清、尿液等人体基质，以及生产车间空气、食物、室内外灰尘等外暴露基质中DBDPE含量，明确各类人群的DBDPE内暴露水平及外暴露（经车间空气、膳食等途径摄入）水平，并开展与肝功能指标的关联分析。同时依据人群暴露评估结果推算染毒剂量，通过细胞染毒实验及动物染毒实验进一步探索DBDPE长期持续暴露的肝脏毒性效应，结合人群研究结果评估DBDPE的人群暴露状况及长期暴露的健康风险，为其污染防治提供依据。

本课题着重开展了十溴二苯乙烷（DBDPE）的人群暴露评估、肝脏毒性效应与毒作用机制研究。首先，在国内外率先建立了DBDPE生产厂工人队列，发现工人经车间空气每日吸入DBDPE在0.804至27.5μg/kg bw/day，平均为11.5 μg/kg bw/day，该均值已超过美国环保署设定的10μg/kg bw/day的健康阈值，表明DBDPE职业工人长期处于DBDPE高暴露状态，其暴露水平可能引发不良健康效应，需加强职业防护。同时，本课题发现职业人群血清中DBDPE含量均值高达7219 ng/g lipid，该值远高于其他人群，与DBDPE工人的高外暴露相匹配。本课题同时建立了高污染物普通人群队列和背景污染人群队列，发现DBDPE生产地的普通人群血清中DBDPE含量均值为144.5 ng/g lw，该值虽明显小于职业人群，但依然远高于背景污染区人群，说明大量的DBDPE生产可带来显著环境污染。本课题随后依托职业人群队列探索了DBDPE内暴露与肝脏功能的相关性，发现DBDPE工人血清中DBDPE含量与白蛋白球蛋白比值A/G存在显著正相关关系（r=0.247，p=0.003），提示白蛋白和球蛋白可作为指示DBDPE引发的肝脏毒性效应的早期预警指标。依据获得的DBDPE外暴露水平，本课题开展了大鼠染毒实验，发现与对照组相比，DBDPE染毒大鼠出现明显的肝脏组织病变，且血清、肝组织匀浆液中一系列生理生化指标，如葡萄糖（Glu）、丙二醛（MDA）、超氧化物歧化酶（SOD）、CYP3A2 mRNA等也呈现显著差异，表明DBDPE染毒可损害肝结构和功能、诱导氧化应激和炎症反应。为进一步探索DBDPE引发肝损伤的毒作用机制，本课题以人正常肝细胞（LO-2）为模型开展体外染毒实验，发现DBDPE染毒可造成肝细胞超微结构损伤，引起LDH、AST、ALT、GSH、SOD、ROS等一系列指标显著升高，还能引起L0-2细胞线粒体膜电位显著升高，以及内质网应激相关蛋白如PERK、IRE-1α表达量的显著升高。DBDPE染毒还可显著升高细胞凋亡率，显著抑制CYP3A蛋白的表达。据此本课题总结认为DBDPE暴露可导致肝脏细胞内质网应激途径被激活及线粒体功能障碍，使肝脏代谢外源化学物的能力下降，进而造成肝脏损伤。本课题研究成果为DBDPE污染的管控提供了基础数据和科学依据。