Biochemical and histopathological effects of kerosene-contaminated soil on Eisenia fetida

Abstract

Kerosene contamination poses a persistent threat to terrestrial ecosystems, yet its biological effects on soil invertebrates remain poorly characterized. This study investigated the biochemical and histopathological responses of the earthworm Eisenia fetida exposed to soils amended with 0.4, 1.0-, and 1.6-mL kerosene kg⁻¹ dry soil for 28 days. Activities of key antioxidant enzymes—superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)—declined significantly (p<0.05) with increasing kerosene concentration, indicating oxidative stress and disruption of redox homeostasis. Interestingly, malondialdehyde (MDA) levels decreased in exposed worms, suggesting possible metabolic inhibition under sustained oxidative pressure. Mortality rose sharply with both concentration and duration of exposure (p < 0.001). Histopathological analysis of the clitellum revealed progressive tissue degeneration, necrosis, inflammation, and pigment deposition, with severity increasing in a concentration-dependent manner. The combined biochemical and morphological evidence links kerosene exposure to oxidative stress–mediated reproductive impairment. These findings reinforce E. fetida as a sensitive biomarker of hydrocarbon-induced soil toxicity and provide a mechanistic basis for assessing the ecological risks of petroleum contamination in terrestrial environments.