Occurrence, seasonal distribution and probabilistic source-specific health risk assessment of dissolved trace metals in southwestern rivers, Nigeria.

Abstract

The presence of trace metals (TMs) in river systems at certain levels can cause toxicity and pose significant risks to human health. In this study, nine TMs (Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) in water samples collected from six major rivers from southwestern Nigeria during both dry and wet seasons. Across both seasons, the mean concentrations (mg/L) ranged from 0.463 to 5.611, 0.121-0.438, 0.016-0.393, 0.122-1.193, 0.005-5.950, 0.924-8.547, 0.026-3.339, 0.001-0.138, 0.022-0.151, and 0.036-0.853 for Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, respectively. Almost 100 % of Cd, Cr, and Pb were above the maximum admissible and desirable limits recommended by WHO. Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) indicate that the TMs are mostly derived from anthropogenic activities with partial contribution from natural sources. In either children or adults, dermal pathways accounted for not <78 % of the total contribution to carcinogenic risks. Source-specific health risk assessment revealed Cr and Cd as major contributors to CR via dermal and ingestion pathways, respectively. A probabilistic health risk assessment via hazard quotient and index indicated potential non-carcinogenic health risks (HI > 1) and high carcinogenic risk levels; children were more vulnerable than adults in both seasons.