经口摄入土壤多溴联苯醚生物可给性变化及影响因素的体外消化模拟

Variations and Influencing Factors of Oral Bioaccessibility of Polybrominated Diphenyl Ethers in Soils Using an In-vitro Gastrointestinal Model

误食土壤是污染物(如多溴联苯醚)人体(主要是儿童)暴露的重要途径,人体消化道内污染物吸收的生物可给性是针对此种暴露方式进行定量风险评估的有效途径之一.本研究采用体外消化实验模拟3种不同有机碳含量的天然土壤中典型多溴联苯醚(BDE-28、BDE-47、BDE-99和BDE-153)在胃和小肠消化液中的释放,验证部分消化释放的多溴联苯醚因消化残留固相表面的再吸附造成低估实际生物可给性,并通过不同水土比的拟合计算予以校正.结果表明,校正后的消化率普遍高于校正前;就不同土样而言,BDE-28、BDE-47、BDE-99和BDE-153在不同初始暴露浓度条件下平均提升比例范围分别为14.3%~42.3%、11.1%~32.1%、4.9%~12.3%和0.0%~7.7%.因此,未经校正的消化率会显著低估PBDEs消化道内的生物可给性,尤其是低溴代组分及PBDEs初始浓度较高或高TOC含量的土样.校正后BDE-28、BDE-47、BDE-99和BDE-153的消化率分别维持在21.9%~54.7%、18.8%~43.1%、13.4%~27.2%和9.3%~19.9%.此外,PBDEs的消化率与其辛醇-水分配系数的对数lg KOW呈显著负相关;而与土壤TOC含量及PBDEs初始暴露浓度的相关性并不显著,尤其是高溴代组分.

Intake of contaminated soils is considered as an important exposure pathway of polybrominated diphenyl ethers( PBDEs) to humans,especially for children during their outdoor hand-to-mouth activities. Oral bioaccessibility is an essential tool to quantitatively assess the exposure risk of pollutants. In this study,we employed an in vitro digestion model to mimic the gastrointestinal digestion of typical PBDEs( BDE-28,BDE-47,BDE-99 and BDE-153 at a series of initial concentrations) in three natural soil samples with different TOC contents and to verify a previous hypothesis that the sorption of PBDE fraction mobilized from soil into digestive fluid on the surface of residual solid phase may lead to an underestimation of bioaccessibility of PBDEs. In addition,a method with multiple fluid-to-solid ratios was applied to calibrate the underestimation. The results indicated that the calibrated digestibility values were commonly higher than those without correction. For the different soil samples,the averaged increasing rates of PBDE digestibility at different initial concentrations ranged from 14. 3% to 42. 3%,from 11. 1% to 32. 1%,from 4. 9% to 12. 3% and from 0. 0% to7. 7% for BDE-28,BDE-47,BDE-99 and BDE-153,respectively. Therefore,the bioaccessibility of PBDEs in gastrointestinal gut would be significantly underestimated without calibration,especially for tri- and tetra-BDEs and soil samples with low TOC contents or high PBDEs concentrations. The corrected digestibility values of BDE-28,BDE-47,BDE-99 and BDE-153 were 21. 9%-54. 7%,18. 8%-43. 1%,13. 4%-27. 2% and 9. 3%-19. 9%,respectively. The results indicated that the PBDEs digestibility was negatively correlated with lg KOW; whereas there was no significant correlation of PBDE bioaccessibility with TOC contents in soils or with initial concentrations of PBDEs,particularly for the highly brominated components.