Co-occurrence of biodegradable and conventional microplastics in marketed marine fish and implications for human dietary exposure.

While the ecological and toxicological impacts of petroleum-based conventional microplastics (CMPs) are well documented, biodegradable plastics (BPs) are increasingly promoted as sustainable alternatives to mitigate plastic pollution. However, degradation of BPs under natural aquatic conditions is mostly incomplete, leading to the formation of biodegradable microplastics (BMPs). Growing experimental evidence suggests that BMPs are bioavailable to aquatic organisms and may cause biological effects comparable to those of CMPs. This study for the first time, reports the co-occurrence with CMPs in both edible and inedible tissues of commercially important marine fish and also reports BMP presence in marine fish for the first time in India. A total of 11.2% of fish exhibited co-occurrence in the gastrointestinal tract (GIT), while in edible tissues, co-occurrence was detected only in S. indicus. The co-occurrence of CMPs and BMPs in fish reveals a dual exposure risk, indicating that BPs do not replace conventional plastics but instead coexist with them, collectively intensifying potential food safety and human health concerns. The estimated daily dietary exposure indicates that children may experience relatively higher potential intake of microplastics, suggesting a possibility of associated health implications. Overall, this study emphasises that concurrent exposure through fish consumption may represent a significant pathway of human microplastic intake. It also signifies the necessity for targeted risk assessment frameworks and informed policy interventions to address this co-exposure through fish consumption.