Micro- and nanoplastics released from biodegradable and conventional plastics during degradation: Formation, aging factors, and toxicity.

The use of biodegradable plastics may solve the pollution caused by conventional plastics in the future. However, microplastics and nanoplastics are produced during the aging process of biodegradable plastics. This work evaluated the formation of secondary microplastics and nanoplastics and the effects of aging factors (UV radiation and mechanical forces) during the degradation processes of various biodegradable plastics (poly(butylene adipate co-terephtalate) (PBAT), poly(butylene succinate) (PBS), and polylactic acid (PLA)) and conventional plastics (polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC)). This study also assessed the combined toxicity of secondary microplastics and Triclosan (TCS) on Tigriopus japonicas. The results showed that PLA and PBS could produce many microplastics. Most secondary microplastics were smaller than 50 μm. Primary pellets were more likely to generate microplastics through mechanical degradation than via photooxidation. In contrast, PBAT/PLA and PE bags were more likely to form microplastics through photooxidation than mechanical degradation. The secondary microplastics did not affect the survival of T. japonicas and the toxicity of TCS. This study highlights that risk assessment of biodegradable plastics, especially secondary microplastics, and nanoplastics, should be assessed in future studies.