IMPACT OF OIL AND GAS–RELATED HEAVY METAL EXPOSURE ON ANTIOXIDANT ENZYME ACTIVITY IN HUMAN POPULATIONS OF KARAK, PAKISTAN

Abstract

Chronic exposure to heavy metals released from oil and gas operations poses a serious risk to human health through the induction of oxidative stress. This study quantified blood concentrations of arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), cobalt (Co), and copper (Cu) in residents living near the Nashpa oil and gas plant in Karak, Pakistan, and evaluated their effects on antioxidant enzyme activity. Blood samples were collected from 63 individuals residing within a 6 km² radius of the facility and analyzed using atomic absorption spectrophotometry. Antioxidant defense and oxidative stress biomarkers were assessed by measuring catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), reactive oxygen species (ROS), and lipid peroxidation (LPO). Mean blood concentrations of Cd (5.65 µg/L), Pb (306 µg/L), Hg (8.38 µg/L), Co (5.78 µg/L), and Cu (1963.75 µg/L) exceeded World Health Organization (WHO) permissible limits. Correspondingly, mean activities of CAT (5.13 U/ml), POD (9.33 U/ml), and SOD (35.35 U/ml) were markedly reduced, while ROS (0.17 U/ml) and LPO (16.19 U/ml) levels were elevated, indicating enhanced oxidative stress. Elevated heavy metal exposure was inversely associated with antioxidant enzyme activity, confirming oxidative imbalance in the exposed population. These findings highlight the potential health risks faced by communities residing near oil and gas facilities and underscore the urgent need for continuous biomonitoring and stricter environmental regulation in petroleum-producing regions.