How harmless are alternative bioplastics? A review of their toxicological outcomes in aquatic organisms.

Plastic pollution is one of the major global concerns. The replacement of traditional synthetic polymers by "greener" alternatives (i.e., biodegradable and/or bio-based plastics) with lower toxicity and environmental impact has been identified as a key strategy to reduce the environmental hazards posed by plastics. Despite the improvements brought by bioplastics from the environmental degradability and overall life-cycle standpoint, a few recent studies have reported that these new polymers have similar (or, even, higher) toxicity to conventional plastics (such as PET), primarily due to their high biodegradability and the subsequent leaching of additives that compose them. Hence, the present review aims to summarize the ecotoxicological effects of some currently used bioplastics and green plasticizers on aquatic organisms, and to compare them with those reported for conventional fossil-fuel-based plastics. The adverse effects observed upon exposure to bioplastics and their additives include impaired survival rates, as well as development and histopathological alterations in various organs (liver, gills, digestive system, and gonads), biochemical and molecular evidence of oxidative stress, altered immunity, and impaired reproduction. The scarcity of empirical toxicological studies and the current lack of human exposure recommendations urgently call for further research efforts on commercially available bioplastics (and their additives). Such efforts are needed to determine whether these materials represent a real eco-friendly alternative, as well as to develop new ones that meet both the industrial, environmental and toxicological requirements. This review aims to help identifying the most promising biopolymer alternatives from an ecotoxicological perspective, while highlighting on the current research gaps.