Abstract:
The present study was conducted to assess the levels of selected organochlorine
pesticide (OCP) residues in water, sediments and Nile tilapia, as well as the potential
health risks to humans who consume the fish of Lake Nakuru. Nine composite water and nine sediment samples, as well as 30 fish specimens, were collected from five representative sampling sites within Lake Nakuru. The OCPs targeted in the present study included p,p′-Dichlorodiphenyl dichloroethane (p,p′-DDD), p,p′ dichlorodiphenyldichloroethylene (p,p′-DDE), p,p′-dichlorodiphenyltrichloroethane
(p,p′-DDT), heptachlor, heptachlor epoxide, α endosulfan (1), β endosulfan (2), endosulfan
sulphate, endrin, lindane, aldrin, dieldrin, methoxychlor and hexachlorocyclohexanes
(alpha; beta; gamma; delta). Except for aldrin, all 16 OCPs targeted in the present
study were detected. The OCP residue levels ranged from below detection limit (BDL)
to 7.44 ± 0.66 μg/L, BDL to 6.39 ± 1.10 μg/kg ww and BDL to 319.74 ± 66.94 μg/kg
ww in water, sediment and fish samples respectively. Some OCP concentrations exhibited
significant differences across the sampling sites (p < .05). The residue level
of endosulfan was above the European Union standard, whereas the target hazard
quotient of heptachlor epoxide was above 1, therefore being unsafe for human consumption. The present study results indicate that most of organochlorine pesticides
though banned in Kenya are still detected in the environment, posing potential long-term
health hazards to humans. Accordingly, environmental monitoring programme and mitigation strategies of reducing pollutant inputs into the lake is recommended,
as well as an immediate ban on harvesting and consumption of fish from Lake Nakuru.
