Abstract:
In this study, the levels of Organochlorine pesticides (OCPs) residues in water, sediment, and fish
samples collected from the Gilgel Gibe I Dam and its tributaries were investigated, along with the
associated health risks. Prior to GC-MS analysis, Soxhlet extraction was used to extract OCPs
from sediment and fish, while homogeneous liquid-liquid microextraction (HLLME) was used for
water samples. The findings revealed that from the OCPs, gamma hexachlorocyclohexanes (γ
HCH) was the most prevalent in the reservoir and tributaries water samples, especially in Yadi
River (YR) (10.97 µg/L) and Nada Guda River (NGR) (7.04 µg/L), with lower levels in their River
mouths and reservoirs. Para, para dichlorodiphenyltrichloroethane (p’, p’-DDT) and its
metabolites dichlorodiphenyldichloroethylene (p’, p’-DDE), dichlorodiphenyldichloroethane (p’,
p’-DDD) were widely detected across sites, ranging from 5.55 µg/L to 11.70 µg/L. High pesticide
levels, particularly alpha hexachlorocyclohexanes (α-HCH), γ-HCH, heptachlor (HC), and aldrin,
were found in Nadi River Sediment (NRS), Yadi River Sediment (YRS), and Nada Guda River
Sediment (NGRS), with concentrations up to 71.93 µg/kg. Beta endosulfan (β-ES) and dieldrin
were detected at lower levels. Sediments from Nada Qala River and River mouths sites showed
lower pesticide concentrations. African catfish from Unkure had heptachlor epoxide (HCE) levels
(225.22 µg/kg) exceeding the maximum residue limit (MRL) of 200 µg/kg. Other OCPs like α
HCH, γ-HCH, HC, and p’, p’-DDT were detected in African catfish and Nile tilapia but remained
below MRLs. However, the Health Risk Index (HRI) values for both fish species remained below
the critical value of 1, indicating no significant health risks from consumption.
