Biochemical effects of polypropylene microplastics on red tilapia (Oreochromis niloticus) after individual and combined exposure with boron

Toxicity of single pollutants or microplastics (MPs) on organisms have been widely reported. However, their combined toxicity with boron has not been investigated. This study examined effects of individual polypropylene microplastics (PP-MPs) or mixed PP-MPs and boron on biochemical biomarkers in red tilapia (Oreochromis niloticus). O. niloticus were exposed for 21 days to pristine PP-MPs concentrations (10 or 100 mg/L), concentrations of boron alone (30 or 70 mg/L), and identical concentrations of boron in the presence of PP-MPs in laboratory aquaria. Results showed that higher concentrations of individual PP-MPs lead to significantly decreased acetylcholinesterase (AChE) in the brain and malondialdehyde (MDA) in fish liver. In contrast, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GSH) were significantly increased in fish liver exposed to higher concentrations of individual PP-MPs. Mixed concentrations of boron and PP-MPs significantly decreased AChE, GSH, and MDA activity in fish. In contrast, mixed concentrations of boron and PP-MPs significantly increased CAT, SOD, and GPx activity in fish. Findings highlight that PP-MPs may increase adverse effects of boron in O. niloticus. We present evidence that individual MPs in long-term exposure have a significant impact on biomarker responses in O. niloticus.