Toxicological Evaluation of Microplastic Extracts in Zebrafish Behavior by Light–Dark and Startle Response Assays

Pollution of the environment by plastics and their degradation products has become a global environmental concern, with microplastics (MPs) being one of the most resilient and most toxic pollutants. In the present work, microplastic powders obtained from a pyrolysis plant in Chennai were treated using saline leaching, and the extracts obtained were evaluated for toxicological effects in zebrafish (Danio rerio.). The light–dark preference test and startle response assay were used as behavioral assays to evaluate anxiety, stress, and neuromotor activity after exposure to graded concentrations of the extract. Zebrafish given elevated doses (12.5% and 25%) showed elevated time in the dark compartment, reflecting increased anxiety levels, and startle responses declined with increasing doses progressively, verifying impaired neuromotor and cognitive abilities. The extract caused negative behavioral effects even at low doses, reflecting its toxicity. These results indicate that pyrolysis-derived microplastic leachates have significant neurobehavioral toxicity in zebrafish, highlighting their potential environmental and public health concern.