Seasonal variation and health risk indices of phthalate esters in Asa River, Ilorin

Water remains polluted due to increasing anthropogenic and industrial activities. Phthalate esters (PAEs) are one of the most frequently detected persistent organic pollutants in the environment and are of concern due to their toxic effects on health. This study investigates the distribution of PAEs and associated health risk in seven tributaries of the Asa River in Ilorin, Kwara State, Nigeria. Water samples were collected during both the dry and rainy seasons. The liquid-liquid extraction method was employed to extract the phthalates, then cleaned up in an alumina column using hexane and quantified using a Gas chromatograph-mass spectrometer. Six Phthalate esters (Dimethyl Phthalate (DMP), Diethyl Phthalate (DEP), Di-n-butyl Phthalate (DBP), Butyl Benzyl Phthalate (BBP), Butyl Ethyl Phthalate (BEP), and Di-n-octyl Phthalate (DnOP) were detected in all tributaries in both dry and rainy seasons. The probable non-carcinogenic Hazard Index (HI) and cancer risks via dermal and oral exposures were below critical thresholds in adults and children. The presence of phthalate esters in the tributaries indicates a potential public health threat to users of the water, especially for communities that rely on the tributaries for domestic activities, farm irrigation, pond-based farming, and industrial purposes. Although the current status does not pose a cancer risk, nonetheless, the risk increases over prolonged exposure. Continued monitoring of the entire phthalate in the Asa River and improved waste disposal methods are recommended.