A Review on Co-Occurrence of Microplastics and Flame Retardants in Global Aquatic Environment with A Focus on Microfibers: Sources and Impacts on Their Toxic Effects

Microplastics (MPs) and flame retardants (FRs) are ubiquitous in the aquatic environment. They coexist and jointly pose impacts on the both aquatic environment and organisms. Among MPs, microfibers are of particular concern due to their relative abundance as compared to other shapes of MPs, and their greater potential to carry and absorb pollutants. Microfibers are mainly released into the aquatic environment through the washing of textile products. FRs are widely used in the textile industry for the production of synthetic fibers to enhance fire resistance. Consequently, microfibers released from the textile industry could serve as a potential source of FRs in the aquatic environment. In addition to their concurrent release from textile sector, microfibers also absorb FRs from the surrounding aquatic environments, acting as a vector to transfer FRs between mediums. However, to the best of our knowledge, no study has thoroughly investigated the relationship between microfibers and FRs, and explained the sorption/desorption behavior of FRs on microfibers. Moreover, the insufficient scientific literature addressing their combined toxicity and environmental behavior in the aquatic environment. Owing to the coexistence, environmental, and toxicological behavioral concerns of microfiber and FRs, this review is an attempt to disseminate the valuable insight by considering the coexistence of MPs and FRs to encourage further research on these critical topics.