Estimation of Target Hazard Quotients and Potential Health Risks for Metals by Consumption of African Spinach (Amaranthus hybridusl.) Grown along the Bank of River Kaduna

Heavy metals have been mostly evaluated in terms of their concentration in crops but have not been always related to the menace of ill-health they pose to the populace. There is inadequate information on human health risk index associated with the consumption of heavy metal contaminated African Spinach (Amaranthus hybridus) in relation to location of massive production in Nigeria. This study was conducted to evaluate the heavy metals; Cd, Ni, Pb, Zn, Cu, Fe and health risk associated with the consumption of Amaranthus hybridus grown along the bank of River Kaduna. Samples were collected from five (5) sampling stations within the period of January to March, 2020 and were analyzed using Atomic absorption spectrometry. About 22km was covered along the bank of the river and the average distance between the stations is about 4.4km. Data collected were analysed using descriptive statistics. The order of the heavy metal concentrations were Ni>Pb>Cd>Cu>Fe>Zn, whereby the metal concentrations in Cd (1.20–2.06mg/kg) and Pb (3.10-3.80mg/kg) in most samples exceeded the limits set by World Health Organization and the guidelines set by the Food and Agriculture Organization. A health risk analysis based on the target hazard quotient (THQ) yielded values <1 for all metals except Cadmium, while for the hazard index, all the metals exceeded the limit of 1 which indicated that the samples are likely to be of health concern. For permissible maximum tolerable daily intake in the metals studied, Cd and Pb exceeded WHO/FAO PMTDI of 0.064 and 0.210 respectively. The activities around the bank of the river and irrigation of the vegetable with water contaminated with industrial effluents may have contributed significantly in raising the concentration of Cd and Pb above the WHO/FAO set standard of 0.2mg/kg and 0.3mg/kg respectively. Actions to reduce the concentration of heavy metals in African Spinach from these stations should be carried out to avoid their health hazard on consumers.