HUMAN HEALTH IMPLICATIONS OF POTENTIALLY TOXIC ELEMENTS (PTES) IN OGUN RIVER WATER SAMPLES

Abstract

The presence of potentially toxic elements (PTEs) in water sources poses significant risks to human health. PTEs are sourced from many routes and they have tendencies to bio-accumulate, thereby hampering human metabolic and/or endocrinal processes. This study assessed the concentrations of PTEs in water samples of Ogun river and the potential human health risks of these contaminants.  Water samples were collected seasonally to assess eight widely reported PTEs (Cu, Zn, Ni, Pb, Mn, Fe, Cr and Cd) using Atomic Absorption Spectrophotometry (AAS). The water physico-chemical parameters were determined using standard methods. Highest water pH value (7.86) was recorded during dry season while the lowest value (6.10) in wet season. The Electrical Conductivity (EC) ranged from 13.84 ± 4.38 μS/cm to 36.67 ± 29.51 μS/cm and 13.84 ± 4.67 μS/cm to 47.21 ± 32.86 μS/cm in dry and wet seasons respectively.  Total dissolved solids (TDS) showed slight positive correlation with the electrical conductivity. The mean TDS ranged from 53.50 ± 10.21 mg/L to 57.25 ± 9.74 mg/L and 23.00 ± 4.62 mg/ L to 40.00 ± 2.58 mg/L in wet and dry seasons respectively.  Water samples were analyzed for Cd, Cr, Pb, Zn, Ni, Mn, Fe and Cu contaminations, then compared with NIS, FEPA and WHO standards. The Fe levels were highest in all the samples while Cu level was the least. Cd, Cr, Ni, Fe, Mn and Pb levels exceeded the NIS, FEPA and WHO’s limits.  The largest contributor to non-carcinogenic risks in both adults and children is Pb, while the rest followed the order Cd > Mn > Fe > Ni > Cu > Cr > Zn for children and Fe > Cd > Mn > Ni > Cr > Cu > Zn for adults. Hence, Ogun river is found to have appreciable levels of metal toxicity especially at Lafenwa and Alagada points.