Toxicity trend of biodegradable and non-biodegradable plastic leachates during microbial exposure in seawater

Teresa Uribe-echeverría

Bioplastics are expected to complement and progressively substitute petrochemical-derived plastics, in an attempt to mitigate the environmental impacts caused by plastic pollution. Therefore,  biodegradability and ecotoxicity tests are urgently needed to understand their biodegradation mechanisms  as well as to ensure that no harmful degradation products are released. This study assessed the toxic effects of three innovative bioplastic products, polyhydroxybutyrate resin (PHB), polylactic acid cups (PLA) and a polylactic acid/polyhydroxyalkanoate 3D printing filament (PLA/PHA), together with a synthetic polyvinyl chloride (PVC) toy in Paracentrotus lividus sea urchin larvae.  Microplastics were incubated in seawater with a microbial inoculum for two months and leachate toxicity tests were carried out before, and after 8, 30 and 60 days of incubation.  Microorganisms turned out to be toxic and slightly hampered the detection of the toxicity that was due to the plastic leachates.  Still, PVC toy was the most toxic material, probably due to the added plasticizers. PHB resin showed moderate toxicity, probably influenced by the particularly tiny size of the fragments, as evidence is now emerging that nanoplastics induce worse effects. Interestingly, the toxicity seemed to disappear after 60 days. Conversely, PLA cups and PLA/PHA filament seem to be innocuous for the larvae.