Abstract:
Arsenic (As), mercury (Hg), Cadmium (Cd) and lead (Pb) are toxic heavy metals that naturally occur in the
ecosystem. Their levels are on the rise due to anthropogenic activities posing threat to aquatic wildlife and
humans. In Ghana, pollution of some water bodies has led to unsafe consumption of riverine fishes as well as a
shortage of treated potable water principally because the cost of treating polluted water has become expensive
across the country. This study aimed to assess the As, Hg, Pb and Cd concentrations in water and fishes from
rivers Pra and Ankobrah where activities of artisanal gold mining were carried out resulting in gross pollution of
the water bodies.
An experimental study was performed to ascertain the levels of As, Hg, Pb and Cd in fish species of Nile tilapia
(Oreochromis noliticus) and mudfish (Clarias anguillaris) and aquatic media (water) from the Pra and River
Ankobrah basins using the Atomic Absorption Spectrophotometer (AAS) (Varian AA240FS).
Both river water samples recorded ranges of 0- 0.0040, 0.0060- 0.0387, 0 - 0.0020, 0.006-0.0093 mg/l for
Cadmium, Lead, Arsenic and Mercury respectively. For Cadmium and Arsenic, their levels were comparable
(p > 0.05). However, detected values for Lead and Mercury were no comparable (p < 0.05). Toxic metals
concentrations in the rivers decreased in the order of Hg > Pb > Cd > As. For the fish samples, values ranged
0-0.08, 0.04-0.42, 0-0.04, and 0.40- 0.60 mg/kg for Cadmium, Lead, Arsenic and Mercury respectively.
Generally, appreciably high values were obtained for Mercury. Toxic metals concentrations in the rivers decreased
in the order of Hg > Pb > Cd > As.
Human health risk assessment from heavy metal exposure through fish consumption from the Rivers for both
children and adults showed no significant non-carcinogenic adverse health risk to humans since all calculated
values for Hazard Quotient (HQ) were<1. Nonetheless, Target Hazard Quotient (THQ) values calculated for
children and adult exposure to Cadmium and Mercury were>1 which implied a likely cause of adverse effects
during a person's lifetime.
