Health Risk Assessment and Levels of Toxic Heavy Metals in Oreochromis niloticus and Clarias gariepinus from Alwero and Abay River Basin

Abstract

This study investigated concentrations of toxic heavy metals (Cr, Pb, Hg, Sn, As, Co, Cd) in the muscle and gill tissues of Oreochromis niloticus and Clarias gariepinus from Ethiopia’s Alwero and Abay Rivers, alongside the associated human health risks. Eighty fish samples (20 per species per river) were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). Metal accumulation was significantly higher in gills than in muscle across all samples (p < 0.05). In muscle tissue, species-specific metal accumulation patterns varied by site. Notably, while target hazard quotient (THQ) and hazard index (HI) values remained below 1, indicating no significant non-carcinogenic risk, the carcinogenic risk (CR) for inorganic arsenic in C. gariepinus from the Abay River (1.36 × 10⁻⁴) exceeded the acceptable threshold of 10⁻⁴. Furthermore, chromium, lead, and arsenic levels in the Abay River frequently exceeded global safety limits established by the European Commission and the FAO/WHO. Conversely, fish from the Alwero River generally fell within safe consumption limits, despite elevated tin levels in gills. These findings underscore an urgent need for pollution source control and regular biomonitoring to safeguard public health and ensure food security in these critical Ethiopian fisheries, as unchecked exposure to carcinogenic metals may pose serious long-term health risks.