Public Health Risk Assessment of Heavy Metal Contamination in Abattoir Wastewater-Irrigated Soil and Edible Crops in Agbor, Delta State, Nigeria

Abstract

Abattoir wastewater is often discharged untreated into the environment, posing a significant public health risk when used for irrigation. This study assessed the concentration and human health risks of heavy metals in abattoir wastewater as well as irrigated soils and crops cultivated in Agbor, Nigeria. Effluent, soil, and crop (maize, okra, cowpea) samples were collected from sites irrigated with abattoir wastewater. Heavy metals Pb, Cd, Cr, Ni, Zn, Cu, Fe, Mn, As, and Hg were analyzed using atomic absorption spectrophotometry. Transfer factors (TF), estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) were computed to evaluate human health risks. Mean concentrations of Pb (0.33–0.84 mg/kg), Cd (0.21-0.56 mg/kg), and Cr (0.22-0.49 mg/kg) in crops exceeded WHO/FAO permissible limits. The order of metal accumulation in crops was Fe > Zn > Pb > Cu > Cd > Cr > Mn > Ni > As > Hg. TF values were highest in okra (TF_Pb = 1.88), indicating bioaccumulation potential. EDI and THQ values for Pb and Cd surpassed safety thresholds for adults and children consuming these crops. The combined hazard index (HI) values were above 1 in all tested crops, signaling potential non-carcinogenic risks. Crops irrigated with abattoir wastewater in Agbor accumulate hazardous levels of heavy metals, posing dietary health risks to local consumers. Urgent interventions are required to regulate wastewater reuse in agriculture and safeguard public health. Keywords: Abattoir wastewater management, Agroecology, Food safety, Heavy metals, Nigeria, Public health risk