Chronic Exposure to Toluene and Heavy Metals and Changes in Indices of Liver Function, Inflammation and Oxidative DNA Damage among Automobile Workers

Oxidative stress (OS), oxidative DNA damage and inflammatory response induced by chronic exposure to volatile organic compounds and heavy metals (HM) have been implicated in multiple organ dysfunction. The liver enzymes (alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma glutamyl transferase (GGT)), biomarkers of OS (nitric oxide (NO), glutathione (GSH), total antioxidant capacity (TAC), total plasma peroxides (TPP), malondialdehyde (MDA)) oxidative stress index (OSI)), oxidative DNA damage (8-hydroxy-2-deoxyguanosine (8-OHdG)), and inflammation marker (tumor necrosis factor alpha (TNF-α)); heavy metals (cadmium (Cd), lead (Pb)) and urine hippuric acid (uHA) levels were assessed in automobile workers.

Fifty automobile workers and 50 controls aged 18-60 years were enrolled into this study. The MDA, GSH, NO, TAC, TPP, ALT, ALP and GGT were estimated by colorimetry, 8-OHdG and TNF-α by enzyme linked immunosorbent assay, Cd, Pb by atomic absorption spectrophotometry and uHA by high performance liquid chromatography. Data were analyzed using t-test and correlation analysis at p <0.05.

Automobile workers had significantly higher liver enzymes, lipid peroxidation, oxidative stress, oxidative DNA damage, nitric oxide, HM, uHA and lower total antioxidants relative to controls. Heavy metals were positively associated with MDA, TPP and OSI; TPP with duration of exposure; ALP with number of working hours; and liver enzymes with OSI only in automobile workers.

Association of exposure to toluene and heavy metals with increased liver enzymes activity, lipid peroxidation, oxidative stress, oxidative DNA damage, and depressed antioxidants in automobile workers suggest increased risk of hepatotoxicity and hepatocellular carcinogenesis.