Seasonal variation and health risk assessment of selected pesticide residues in shallow groundwater water in Gokwe-Nemangwe, Zimbabwe

Abstract

While pesticides application has caused improved agricultural yields, their use has raised concerns of potential harm to the health of humankind. This study focused to assess seasonal variability of health risk linked with pesticide residues to humans through shallow groundwater. To assess water quality, samples were collected from shallow groundwater sources once in each of the rain and dry spells of 2020 and analyzed for five pesticide residues including amitraz, dimethoate, omethoate, endosulfan and endosulfan sulphate. Liquid chromatography tied with tandem mass spectrometry was used to assess residues of pesticides in water samples. Health risk evaluation was achieved using the Human Health Risk Assessment model for children and adults on the residues through ingestion. All the pesticide residues tested were detected in the shallow groundwater samples in both spells. Endosulfan had the greatest concentration, with an average concentration of 0.009 mg/L varying from 0.005 mg/L to 0.012 mg/L, in the wet season. Dimethoate and omethoate highest mean concentration was 0.007 mg/L in the wet period, which exceeded the maximum allowable limit advised by the World Health Organization. The least concentration level was 0.006 mg/L for amitraz and endosulfan sulphate. Dimethoate and omethoate contributed to non-carcinogenic risks for children in both the wet and the dry seasons, calculated at the level of 3.5 and 2.5 respectively. The same pesticide residues were also a risk to adults in the wet season with a similar HQ value of 1.17. Pesticide residues contamination of groundwater is imminent and results in human health risk via ingestion. There is a need therefore to assess health risks through well-planned preventive measures, including risk assessment, thorough monitoring, and regulating shallow groundwater wells.