Multi-Dimensional Assessment Approach to Assess Pesticide Manufacturing Industry Wastewater Toxicity

Pesticide manufacturing industry wastewater is a complex mixture of potentially harmful components. If not properly treated, discharged effluents may pose serious risks to environment and organisms. In this study, influent and effluent wastewater samples from a pesticide factory were comprehensively non-screened by liquid chromatography high-resolution mass spectrometry, coupled with zebrafish embryo toxicity testing to assess whole effluent toxicity. A total of eight chemical groups were identified, including pesticides, antibiotics, nitrogen compounds, ketones, esters, amines and derivatives, other drugs, and other organic compounds. While wastewater treatment processes reduced most of the analyzed groups of compounds, compounds (e.g., 2-aminophenol, N-Nitrosodipropylamine, and carbamazepine) increased during the treatments. The influent samples were more toxic to zebrafish than the effluent samples in terms of lethality, teratogenic effects, developmental impacts, locomotor behavior, and neurotoxicity. The results showed that locomotor behavior was the most sensitive phenotypic toxicity endpoint, with significantly higher sensitivity than traditional acute lethal or teratogenic endpoints. Through a multi-dimensional assessment approach combining chemical screening, literature-based, risk ranking, and targeted quantification, we identified three predominant pesticide residues in the wastewater samples (both influents and effluents): hexaconazole, fenobucarb and isoprocarb. All three compounds exhibited additive or synergistic toxicity in zebrafish embryos. Exposure to ≥0.08% influent or ≥2% effluent increased inflammation (interleukin-1 beta, IL-1β), oxidative stress (copper/zinc superoxide dismutase, Cu/Zn-Sod), apoptosis (tumor protein p53, p53), and significantly impaired neurodevelopment in zebrafish larvae by altering the expression of sonic hedgehog a (shha), synapsin IIa (syn2a), and glial fibrillary acidic protein (gfap). This study suggests the necessity of incorporating non-apical endpoint (locomotor behavior) into whole effluent toxicity test, as this approach is essential for reducing the environmental risks posed by pesticide factory wastewater.