Novel Insights into the Dermal Bioaccessibility and Human Exposure to Brominated Flame Retardant Additives in Microplastics

In this study, we optimized and applied an invitro physiologically based extraction test to investigatethe dermalbioaccessibility of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane(HBCDD), incorporated as additives in different types of microplastics(MPs), and assess human dermal exposure to these chemicals. The dermalbioaccessibility of PBDEs in polyethylene (PE) MPs was significantlyhigher (P < 0.05) than in polypropylene (PP) MPs.Both log K (ow) and water solubility influencedthe dermal bioaccessibility of PBDEs. For HBCDDs in polystyrene MPs,the dermally bioaccessible fractions were 1.8, 2.0, and 1.6% of theapplied dose for & alpha;-, & beta;-, and & gamma;-HBCDDs, respectively.MP particle size and the presence of cosmetic formulations (antiperspirant,foundation, moisturizer and sunscreen) influenced the bioaccessibilityof PBDEs and HBCDDs in MP matrices at varying degrees of significance.Human exposure to n-ary sumation PBDEs and n-ary sumation HBCDDs via dermal contactwith MPs ranged from 0.02 to 22.2 and 0.01 to 231 ng (kg bw)(-1) d(-1) and from 0.02 to 6.27 and 0.2 to 65 ng (kgbw)(-1) d(-1) for adults and toddlers,respectively. Dermal exposure to PBDEs and HBCDDs in MPs is substantial,highlighting for the first time the significance of the dermal pathwayas a major route of human exposure to additive chemicals in microplastics. There are no data on dermal exposureto microplastics orassessment of the risk arising from such exposure. This study reportsthe bioaccessibility of brominated flame retardants in various typesof microplastics upon contact with human skin surface film liquidwith implications for human dermal exposure.

Automated summary

In this study, an invitro physiologically based extraction test was used to investigate the dermalbioaccessibility of PBDEs and HBCDDs in different types of microplastics. The dermal bioaccessibility of PBDEs was significantly higher in polyethylene MPs compared to polypropylene MPs. The size of MP particles and the presence of cosmetic formulations influenced the bioaccessibility of PBDEs and HBCDDs. Human exposure to these chemicals via dermal contact with MPs was found to be substantial and the dermal pathway was identified as a major route of exposure.