Ecological and human health risk of heavy metals in Nubui River: a case of rural remote communities

Abstract

The Nubui River is a primary source of water for drinking purposes and other domestic activities in the rural communities dotted along its riparian zone, with agriculture being the major activity occurring in this important ecotone. The river has become a potential sink for agrochemical residue, including heavy metals, and has apparent aesthetic water quality issues, with associated health consequences. This study, therefore, assessed the health risks of heavy metals within the rural populations in the catchment areas, who have limited sources of improved water supply.The concentration of iron (Fe), lead (Pb), cadmium (Cd), mercury (Hg), and zinc (Zn) was assessed on cumulatively 275 water samples, using a Perkin Elmer PINAAcle 900 T atomic absorption spectrophotometer for 11 months. A cross-sectional survey was conducted amongst 338 community members, following field observations on utilisation types, aesthetic appeal, and perceived quality of water from the Nubui River. To determine the potential human and ecological risks of heavy metals, the hazard quotient, chronic daily intake, contamination factor, and health pollution indices of heavy metals were computed. STATA version 16 was used to analyse the survey results.Descriptive statistics of average concentrations of heavy metals in surface water at all sampling stations showed the pattern Hg < Pb < Cd < Zn < Fe, with relatively low concentrations, between 0.001 and 0.004 mg/L for Hg, 0.0011 and 0.0019 mg/L for Pb, 0.0461 and 0.0739 mg/L for Zn, and 0.2409 and 0.377 mg/L for Fe. The findings, however, showed relatively high cadmium levels between 0.0215 mg/L and 0.0383 mg/L in two of five sampling stations in comparison with the World Health Organisation (WHO) drinking water guideline values in some months. Hazard quotient values indicate that the population is safe from the non-carcinogenic health risks of exposure to heavy metals through oral routes. The contamination factor and heavy metal pollution indices for cadmium exceed recommended guideline values of 1 and 100, respectively. Meanwhile, 73.1% of community members evidently preferred the Nubui River for various domestic activities with 86.1% of them utilising it for drinking purposes. This occurrence results in exposure to associated health risks.