基于污染场地土壤中重金属人体可给性的健康风险评价

Health Risk Assessment Based on Bioaccessibility of Heavy Metals in Contaminated Sites

模拟测试土壤中重金属在人体胃肠系统中的溶解量(即人体可给量),并以此作为暴露剂量进行健康风险评估,能在一定程度上克服基于总量评估导致结果过于保守的问题.该文综述了国内外目前已有的可给性测试方法,着重介绍了PBET(physiologically based extraction test)、SBET(simplified bioaccessibility extraction test)、RIVM(rijksinstituut voor volksgezondheid en milieu)及UBM(the unified bioaccessibility method)这4种常用方法的原理及主要参数取值;对目前测试方法在参数(pH、提取时间、提取液组分)取值、模拟过程与环境(消化过程、模拟环境、食物、微生物)存在的问题进行了分析;进一步介绍了基于重金属人体可给性的健康风险评估方法.建议应在以下4个方面进一步开展研究:①基于我国人体胃肠生理特征建立土壤中重金属可给性的标准测试方法;②研究影响重金属可给性的关键因素并建立经验预测模型;③结合in vivo测试,验证方法的准确性,耦合结肠癌细胞跨膜转运测试模型,研究测试重金属的人体有效性的标准方法;④建立基于重金属可给性的层次化风险评估方法,完善现有风险评估技术导则.

The health risk calculated based on site-specific bioaccessible fraction of heavy metals （HMs） is more realistic than the one based on the total concentration of HMs in soil. Bioaccessibility can be measured by simulating the digestive processes of HMs desorption in human gastrointestinal system. The test methods used currently were introduced with details during the simulation process and values of key parameters of the four wildly applied methods （PBET, SBET, RIVM and UBM）. The problems were analyzed in the values of parameters （e. g. , pH, extraction time, components of simulated gastrointestinal solution） and the simulated processes and environments （e.g., digestive process, environment, impact of food and microorganism in the digestive tract）. Further, the acceptance of risk assessment incorporating HMs bioaccessibility to the environmental administrative staff and the public in the USA and EU were also discussed. Finally, based on the review of the research development in China, four research areas were suggested： （ 1 ） standardizing of bioaccessibility test of HMs in soil based the digestive characteristic of Chinese people ; （ 2 ） finding out the key influence factors that control HMs bioaccessibility in soil and development of an empirical model to predict HMs bioaccessibility based on them; （3） verifying the bioaccessibility test methods by in vivo test and developing a bioavailahility test method by combining Caco-2 transportation model to the current in vitro methods; （4）developing a tiered risk assessment framework to incorporate HMs bioaccessibility and refine the ＇guidelines currently in use.