Trace metal concentrations, fluxes, and potential human health risks in West Africa rivers: a case study on the Bia, Tanoe, and Comoe rivers (Cote d'Ivoire)

Downstream water pollution resulting from anthropogenic pressures on upstream water can cause conflicts, especially in transboundary rivers basins. This study assessed trace metals cadmium, lead, copper, and iron total concentrations, fluxes, and the potential human health risks through ingestion or dermal contact of waters at the mouth of three West African transboundary rivers: the Comoe, Bia, and Tanoe rivers. The results showed highest total concentrations during the months of May and October and statistically comparable concentrations in the rivers. The fluxes discharged to the Atlantic Ocean through the Aby and Ebrie Lagoons are as high as average values found elsewhere in the World. Trace metals lead, copper, and iron fluxes were highest during the month of October in the Bia, Tanoe, and Comoe rivers. The cadmium flux was highest during the month of October in the Bia and Comoe rivers, and during the months of February and December in the Tanoe River, indicating that contamination came mainly from upstream waters and the draining of the river basins. The Pearson correlation analysis showed that the trace metals were mainly from anthropogenic sources including gold mining and agriculture. The total concentrations were lower than international guidelines set by the World Health Organization (WHO). However, the potential human health risk assessment results suggest a significant likelihood of community exposure to harmful effects but not to cancers through water ingestion. This work recommends including small rivers when assessing global river metal fluxes to the ocean and also reducing upstream inputs from human activities to mitigate downstream river water pollution.

Automated summary

This study assessed the concentrations, fluxes, and potential health risks of trace metals in the waters at the mouth of three transboundary rivers in West Africa. The results showed that the metals mainly came from anthropogenic sources and although the concentrations were lower than international guidelines, there was still a significant risk of community exposure to harmful effects.