Oxidative Stress in Painters Exposed to Low Lead Levels

Lead toxicity is a public health problem particularly to the children and to occupationally exposed adults. Evidence is mounting successively regarding the adverse health effects of lead at low levels. This study was undertaken to assess the antioxidant status of lead-exposed residential and commercial painters of Lucknow city in Uttar Pradesh, India.

Thirty-five painters aged 20 to 50 years who had blood lead levels ≤400 μg L^-1 were selected for the study from a population of 56 male painters initially screened for blood lead. The control group included an equal number of subjects of the same age group without any occupational exposure to lead.

We studied the association between low lead level exposure and antioxidant status and found that blood lead levels in painters were approximately seven times as high as in controls [(219.2 ± 61.9) μg L^-1 vs. (30.6±10.1) μg L^-1, respectively]. Among the biomarkers of lead toxicity a significant decrease in the level of delta-aminolevulinic acid dehydratase [(9.13±4.62) UL^-1 vs. (39.38±5.05) UL^-1] and an increase in the level of zinc protoporphyrin [(187.9±49.8) μg L^-1 vs. (26.4±5.5) μg L^-1] were observed in painters compared to controls. Among antioxidant enzymes, painters showed a significant decrease in catalase [(56.77±11.11) UL^-1 vs. (230.30±42.55) UL^-1] and superoxide dismutase [(0.64±0.19) UL-1 vs. (2.68±0.62) UL^-1] compared to controls. Lipid peroxidation was monitored by measuring thiobarbituric acid reactive substances (TBARS) that were expressed in terms of malondialdehyde (MDA) equivalents. Concentration of MDA in plasma was higher in painters than in controls [(7.48±1.31) nmol mL^-1 vs. (3.08±0.56) nmol mL^-1]. Significant changes were also observed in reduced and oxidised glutathione levels. The strong association between blood lead levels and oxidative stress markers in this population suggests that oxidative stress should be considered in the pathogenesis of lead-related diseases among people with low level environmental exposure to lead.