Effect of Polyvinyl Chloride and Polystyrene Micro-Plastics on Growth, Digestive Enzymes, Oxidative Stress, and DNA Damage in Ctenopharyngodon idella.

Micro-plastics (MPs) have become a constant source of pollution in freshwater bodies and increasingly becoming a threat to aquatic life. Chronic exposure to MPs has been linked to the inhibition of growth, deformations in digestive physiology, oxidative stress, and cellular injury. Current study was conducted on fish (Ctenopharyngodon idella) acclimatizing and exposing them to a 90-day dietary exposure to MPs. The growth performance indicators, that is, digestive enzymes, oxidative stress biomarkers, and DNA damages were measured in the pre- and post-dietary exposure to the MPs. There was a progressive decrease in the growth performance indicators such as highest increase in weight as found in 30% PVC group (6.95 ± 2.69 g) and the 30% PS group (2.91 ± 3.28 g) was far less as compared to the corresponding controls (18.8 ± 5.86 and 16.07 ± 5.32 g, respectively). The levels of catalase activity in the control fish kidney, skin, heart, brain, and gill tissues were significantly higher than in the exposed groups (p < 0.05), whereby superoxide dismutase activity were increased, an indication to the increased oxidative stress. Digestive enzyme reactions were tissue-specific, where lipase was the most sensitive, mainly in the stomach and liver, at the increased dosage. The frequency of micronuclei also increased in the erythrocytes of exposed fish, which proves that polymers caused concentration-dependent genotoxic damage. Hence, PVC and PS MPs had negative effects on C. idella whereby growth was affected, antioxidant status was disturbed, genotoxicity was augmented, digestive enzyme biomarkers were affected, and micro-nucleus frequency was increased. Further research is required on chronic exposure, histopathological changes, and the mechanisms of MPs toxicity at the molecular level.