Ecotoxicological risk assessment of metalloid contamination in the sediment and benthic fauna of a tropical lotic freshwater ecosystem in Southern Nigeria

The increasing exposure of freshwater bodies to pollutants and the bioaccumulation of heavy metals in body parts of aquatic organisms has raised concerns on the ecotoxicological and human health risk. This study evaluated the potential ecological and human health risk of heavy metal pollution in sediment and benthic fauna (Caridina africana) of the Osse River, Edo State, Nigeria. Using requisite equipment, samples of water sediment and C. africana were collected at designated stations from September 2015 to February 2017. Heavy metal concentrations in samples were determined using atomic absorption spectrophotometer. Result showed heavy metal contamination with concentration profiles of Fe > Zn > Mn > Cu > Ni > Pb > Cr > Cd > V in sediments and Fe > Zn > Mn > Cu > Ni > Cr > Pb > Cd > V in C. africana. The potential ecological risk index (PERI) values classified stations 1, 2 and 4 as of low ecological risk (PERI ≤ 150), while station 3 (PERI ≤ 300) was classified as of moderate ecological risk. Human health risk assessment for heavy metals in C. africana indicated significant non-carcinogenic health risk (HI > 1), and high carcinogenic risk to human health. The consumption of the contaminated C. africana, which is harvested in commercial quantities, portends health risk to the general public. There is need for urgent action in the abatement and regulation of identified anthropogenic activities responsible for the release of these heavy metals into the Osse River.