Genotoxicity effect of chronic lead exposure assessed using the comet assay

BACKGROUND: Lead, an important xenobiotic, is globally well distributed. The IARC has classified inorganic lead compounds as possibly carcinogenic to humans. The study was designed to assess genotoxic effects in workers occupationally exposed to Pb. MATERIALS AND METHODS: The study comprised 62 male workers with chronic exposure to lead and 22 matched non-exposed men. DNA damage was assessed by single cell gel electrophoresis (known as comet assay) using peripheral blood lymphocytes. The level of DNA damage was determined as the percentage of cells with comets. RESULTS: Mean blood Pb (PbB) concentrations in workers exposed to lead were significantly higher than in controls (422.6 +/- 181.2 microg/l vs. 81.0 +/- 37.84 microg/; p< 0.01). The level and the grade of DNA damage were significantly higher in workers exposed to lead (total--12.55 +/- 7.93%; grade 1--9.05 +/- 5.78%; grade 3--1.05 +/- 1.28%; p < 0.05) than in controls (total--6.63 +/- 3.05%; grade 1--5.68 +/- 2.32%; grade 3--0.35 +/- 1.04%; p < 0.05). The highest level and the degree of DNA damage were observed in workers with PbB over 500 microg/l and the lowest in workers with PbB lower than 200 microg/l. CONCLUSIONS: Our results suggest that lead, particularly in people with chronic occupational Pb exposure and high PbB may induce DNA damage in peripheral lymphocytes detected by the comet assay, and thus should be regarded as a potential agent harmful to the human chromosome. The comet assay can be used to monitor and evaluate biological toxic effects in humans occupationally exposed to lead.