Health Risk Assessment of some Heavy Metals and Nitrate in Surface Water of River Kaduna, Nigeria

Abstract

Surface water, which is the most available source of water used for domestic purposes, is greatly impacted by various pollutants with serious health risks  to the human population. In this study, health risk assessment of some metals (Cu, Cd, Cr, Zn, Pb, and Fe) and NO₃ - in River Kaduna was carried out by  calculating the chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI) and carcinogenic risk (CR), while statistical analysis was carried out using  correlation, cluster analysis, and principal component analysis (PCA). The mean concentrations of the pollutants were in the following decreasing  order: Fe > NO₃- > Pb > Cr > Cu > Cd > Zn. Cluster analysis identified four distinct clusters namely (1) Pb and Fe, (2) Nitrate, (3) Cu, Cr, and Cd, and (4) Zn,  while PCA yielded 3 components which explained 78.83 % of the total variance in the data set. Cu, Zn, and NO₃ - did not constitute a non-carcinogenic  risk to the population through oral and dermal contacts (HQ < 1), while Cd, Cr, Pb, and Fe posed varying degrees of non-carcinogenic risks. The  percentage contribution of each of the pollutants to the total non-carcinogenic risk is in the following order: Pb > Cr > Cd > Fe > Cu > NO₃ - > Zn. While Pb,  Cr, and Cd are the major contributors to total non-carcinogenic risk and accounted for 96.27 % of the total risk, CR due to Pb, Cr, and Cd also  exceeded the threshold, suggesting that lifetime exposure to these metals poses a cancer risk to the adult population in the area. The study showed that  Cd, Cr, and Pb pollution in River Kaduna poses both non-carcinogenic and carcinogenic risks to the population.