Chronic toxicological impacts of tire rubber nanoparticles on hematobiochemical, oxidative stress, and immunological responses in Nile tilapia (Oreochromis niloticus).

Tire rubber nanoparticles (TRNPs, ≤ 1 µm) have recently raised concerns about their potential environmental toxicity. Given the lack of research on their impact on aquatic life, this study aimed to investigate the overall effects of this pollutant on the physiological factors of Nile tilapia (Oreochromis niloticus) (10.2 ± 1.7 cm in length and 51.1 ± 10.6 g in weight). To simulate natural exposure conditions, the fish were divided into three groups: group 1 (control): no exposure to any concentration of TRNPs; group 2: exposure to different concentrations of TRNPs in water (5, 10, and 30 mg/L); and group 3: exposure to different concentrations of TRNPs mixed with feed (100, 150, and 300 mg/kg feed) for 15 days. After the experiment, microbial counts were performed on the tank water, and an increase was observed in the groups exposed to TRNPs and in all hematological parameters (red blood cells, white blood cells, hemoglobin, etc.) except for lymphocytes at most concentrations in both groups. Similarly, increases were observed in total protein, liver enzymes, triglycerides, cholesterol, creatinine, urea, immunoglobulins, and lysozyme activity, whereas antioxidant enzyme activities decreased at most concentrations. This provides clear evidence of the danger of TRNPs to fish, gives officials a comprehensive picture to make decisions on mitigating their arrival in aquatic environments, and paves the way for researchers to conduct further studies.