Toxic effects of co-exposure to polystyrene nanoplastics and arsenic in zebrafish (Danio rerio): Oxidative stress, physiological and biochemical responses.

The issue of nanoplastics (NPs) in the aquatic environment has recently received considerable attention. Arsenic (As) is a relatively abundant and toxic metalloid element in aquatic environments. However, the potential toxic effects of As on aquatic organisms under the influence of NPs remain uncertain. In this study, zebrafish were divided into five different groups: a control group, a single As(V) (10 μg/L) treatment group and three As (10 μg/L) + polystyrene nanoplastics (PS-NPs) treatment groups (NPs at concentrations of 1, 5 and 10 mg/L, respectively) for a period of seven days using a semi-static method. The findings demonstrated that the presence of PS-NPs facilitated the accumulation of As in zebrafish liver, gill and intestine with the following promoting efficiency: liver > gill > intestine. The presence of PS-NPs enhanced the oxidative stress effects of As on the aforementioned tissues. Furthermore, the activities of glutathione-S-transferase and glutathione peroxidase in the liver and intestine were found to be instrumental in mitigating oxidative stress during co-exposure. Furthermore, the presence of PS-NPs led to a further reduction in As-induced acetylcholinesterase activity in the liver and intestine of zebrafish. The combined exposure of zebrafish to PS-NPs and As resulted in an increase in lactate dehydrogenase activity in the liver, intestine and gills. This subsequently led to a reduction in the activity of acid phosphatase and alkaline phosphatase in the aforementioned tissues, thus affecting immune dysfunction in zebrafish. The integrated biomarker response indexes indicate that combined exposures result in greater toxic effects compared to single As exposures. The findings provide a fundamental basis for the assessment of the toxic effects of combined nanoscale plastic and As pollution on aquatic organisms.