Toxicological effects of spent engine oil from automechanic workshops on the gills and liver of <i>Clarias gariepinus</i>

Abstract

Engine oil, a major lubricant in automobile engines is often discharged in its spent form into the environment during engine servicing and repairs, from where it may be leached into adjoining surface water bodies during precipitation, with adverse effects on fish and other aquatic biota. The effect on the gills and liver of juvenile Clarias gariepinus exposed to lethal and sub-lethal concentrations of spent engine oil was assessed in this study. A range finding test was first carried out to determine the concentrations for the acute test. Based on the results, an acute toxicity bio-assay was conducted to determine the 96-hr LC₅₀ value. Subsequently, fractions of the LC₅₀ value (1/8^th, 1/6^th and ¼) representing 0.54%, 0.72%, and 1.08% respectively including control (0.00%) were used for the chronic test. The 96hr LC₅₀ was 4.30mg/l. Gills and liver of fishes in the control group showed little or no histological abnormalities. The abnormalities in the gills ranged from moderate to severe thickening and sloughing off of the epithelium and necrosis. The liver tissues of C. gariepinus exposed to the spent engine oil showed moderate to severe cytoplasmic vacuolation and peripherally placed nuclei. The indiscriminate discharge of spent engine oil into water bodies poses a threat to aquatic organisms such as fish resulting in adverse behavioral responses, histological abnormalities in the gills and liver and eventually death. Proper treatment and disposal of the spent oil is therefore necessary to ensure adequate protection of aquatic resources.

Keywords: Clarias gariepinus, Spent engine oil, Histopathology, Gills, Liver