Encapsulation and release of tetrabromobisphenol A in microplastics: Trade-off in their individual toxicity to Xenopus tropicalis tadpoles.

The toxicity of microplastics (MPs) to aquatic animals is closely related to the presence and release kinetics of contained additives, as most plastic products contain various additives. However, the relationship between the occurrence and release of additives from MPs, and their individual or combined toxicity remains unclear. In this study, the nanoscale distribution and release of tetrabromobisphenol A (TBBPA, a common flame retardant with endocrine-disrupting effect) in polystyrene (PS) MPs, and the long-term (60 days) toxicity of TBBPA and MPs containing TBBPA (at doses of 0 %, 1 %, 10 %, w/w) to Xenopus tropicalis tadpoles were investigated. Exposure to 10 μg/L TBBPA alone was the most toxics, while the encapsulation of TBBPA in MPs significantly delayed its lethal toxicity to tadpoles by inhibiting the rapid and extensive release of TBBPA. PS MPs alone and MPs containing 10 % TBBPA exhibited delayed survival toxicity compared to TBBPA alone, whereas PS MPs containing 1 % TBBPA did not show this effect but inhibited growth. These findings suggest that chronic toxicity assessments should be based on long-term (months or even years) exposure experiments due to the encapsulation-controlled slow release of toxic additives.