Transfer of POP-BFRs within e-waste plastics in recycling streams in China

Due to the rapid increase of e-waste plastics and the national policy's strong preference for mechanical recycling, a substantial amount of POP-BFRs is flowing into recycling streams in China. Therefore, confronting with the worldwide prohibition in manufacturing and consumption, identifying the transfer and inventory of POP-BFRs in recycling stage has become the key to their effective management and elimination. In this study, the level of PBDEs in e-waste housings, recycled plastics and daily-use products from recycling facilities and the commodity market was determined, and a gradual decrease of PBDEs was observed along with the downstream life cycle, indicating that recycling is a crucial medium of POP-BFRs transferred from their original use to an expansive reutilization market. Based on that, an extrusion experiment was conducted to imitate the mechanical recycling of e-waste plastics. It was found that, about 77% of PBDEs and 39% of HBCD were retained in recycled materials, with levels comparable to those in the products from recycling manufacturers and the consumer market. Mechanical recycling had no effect on the predominance of highly brominated BDE congeners, and no obvious transformation from higher to lower brominated diphenyl ethers was observed in recycled materials under thermal conditions; however, the isomerization of γ-HBCD brought about a noticeable increase in the relative abundance of α-HBCD. According to a Monte Carlo method estimation by using the transfer rate, approximately 235-687.8 tons of PBDEs have entered into recycling streams annually in the most recent five years. The field survey, laboratory findings and model evaluation results obtained in this study would not only contribute to a broader understanding of POP-BFRs sources and impact scopes posed on human health and the environment, but also provide a basis for developing effective strategies to manage POP-BFRs from the recycling perspective.