Level of mercury in fish from the Ethiopian Rift Valley lakes: Its implications in dietary exposure

Abstract

Environmental contaminants in fish pose a potential human health hazard. The level of mercury (Hg) was investigated in three fish species, i.e., Labeobarbus intermedius, Oreochromis niloticus and Clarias gariepinus, from Lake Koka and Lake Ziway, Ethiopia. The concentrations of Hg found in C. gariepinus and O. niloticus from Lake Koka and Lake Ziway were, in general, lower than the International Marketing Limit (IML) (0.5 μg g^-1) and World Health Organization (WHO) guidelines (0.2 μg g^-1) for consumption. This finding is, in general, in agreement with most studies conducted in other African lakes. However, of the total fish samples for each species, 67% of L. intermedius from Lake Koka and 27% of L. intermedius from Lake Ziway showed Hg concentrations that exceeded WHO guidelines (0.2 μg g^-1) for consumption. Species variation in total Hg (THg) accumulation is attributed to trophic position, and therefore, consumption of fish from a high trophic level may represent a potential health hazard. Consumption of L. intermedius from both lakes may pose a special health risk to children and pregnant women. However, L. intermedius has a low preference as a food fish, and is therefore not widely used by the local people.

Key words/phrases: Fish consumption, Fish species, Hg, Rift Valley Lakes