Distribution and ecological risk assessment of herbicide residues in water, sediment and fish from Anyim River, Ebonyi State, Nigeria

The presence of herbicide residues in water, sediment and African catfish (Clarias gariepinus) from Anyim River was investigated bimonthly from November, 2017 to September 2019. The aim of the study was to evaluate the pollution status of the river and the associated health hazard. The herbicides investigated were glyphosate-based and included sarosate, paraquat, clear weed, delsate and roundup. The samples were collected and analyzed accordingly using gas chromatography/mass spectrometry (GC/MS) based method. The concentration of herbicide residues ranged from 0.02 to 0.77 µg/gdw in sediment, 0.01–0.26 µg/gdw in fish and 0.03–0.43 µg/L in water respectively. Risk Quotient (RQ) deterministic method was used to assess the ecological risk of herbicide residue in fish and the result indicated chances of causing adverse effect on fish species in the river (RQ ≥ 1). Human health risk assessment further indicated potential health implications on humans consuming the contaminated fish on long term basis. •The detected herbicides are hydrophobic, and were more persistent in the sediment.•Herbicide concentrations in water samples were higher than the permissible limits.•It also exceeded the recommended guideline value of 0.1 µg/L by European Union.•The health index of most herbicides investigated was greater than one (HQ > 1).•Eating fish from Anyim River poses great human health risk.