Release behaviors of hexabromocyclododecanes from expanded polystyrene microplastics in seawater and digestive fluids

Abstract The pollution and adverse effects of microplastics in the marine environment have been widely reported. However, the information on the transfer of chemical additives from microplastics to the environment or organisms is quite limited. This study investigated the release of hexabromocyclododecanes (HBCDs) from expanded polystyrene (EPS) microplastics in seawater and digestive fluids. The results showed that both the particle size of EPS microplastics and environmental parameters (temperature, salinity, and pH) play crucial roles in the release of HBCDs. The release rates of ΣHBCD (sum of α-, β- and γ-HBCD) from EPS microplastics in seawater ranged from 8.64 to 33.3 ng·g-1·d-1 under different conditions. Compared with the seawater control, a slight but not significant increase in the release of HBCDs was observed in the digestive fluids. The diastereoisomer profiles of HBCDs released from EPS microplastics both in seawater and digestive fluids were similar. The proportions of α-HBCD and β-HBCD released from EPS in seawater and digestive fluids were higher than those in the original EPS microplastics, especially for β-HBCD. The diffusion model explained the release data of HBCDs from EPS microplastics apparently better than the other two models, suggesting that the diffusion within the matrix of microplastic is a rate-limiting step. Based on the mass of EPS microplastics and release rates of HBCDs, the annual release of HBCDs from EPS microplastics into the global ocean was estimated to be 9.29 to 115 kg. These HBCDs would have profound impacts on marine organisms and even endanger human health and safety. Considering the abundance of microplastics in the ocean, the release of chemical additives from microplastics deserves more attention in the future.