Biomonitoring of genotoxic risk in workers in a rubber factory: comparisonof the Comet assay with cytogenetic methods and immunology

Several substances used in rubber processing are known to be genotoxic. Wor kers in a rubber tyre factory, exposed to a broad spectrum of contaminants such as benzo[a]pyrene, benzo-fluoranthene, naphthalene, acetonaphthene, al kenes and 1,3-butadiene have been regularly examined for several years; chr omosomal aberrations in lymphocytes, mutagenicity of urine (by use of the A mes test) and various parameters of blood and urine were assessed. An eleva ted level of mercapturic acid derivatives was found in the urine of employe es, which is indicative of environmental exposure to toxicants with alkylat ing activity. We have now extended this study by examining genotoxicity wit h the modified Comet assay in parallel with chromosomal aberrations and mic ronucleus formation as well as immunological endpoints. Twenty-nine exposed workers from this factory were compared with 22 non-exposed administrative staff working in the same factory, as well as with 22 laboratory workers. The absolute numbers of peripheral leukocytes were significantly higher in the exposed group than in either of the control groups (p < 0.001). The ery throcyte mean cell volume was significantly higher in exposed workers in co mparison with laboratory controls (p < 0.05). Percentages of lymphocytes, p olymorphonuclear leukocytes, monocytes and eosinophils were not altered. Th e proliferative response of T- and B-cells to mitogen treatment when calcul ated per number of lymphocytes and adjusted for smoking, age and years of e xposure did not differ between exposed and control groups. Endogenous stran d breaks (including alkali-labile sites) and altered bases (formamidopyrimi dine glycosylase- and endonuclease In-sensitive sites) were measured by the Comet assay in lymphocyte DNA. Exposed workers had significantly elevated levels of DNA breaks compared with office workers (p < 0.00001) or with lab oratory controls (p < 0.00001). Micronuclei occurred at significantly highe r frequencies in the exposed group than in controls(p < 0.00001), though th e frequencies were all within the normal range. Significant correlations we re seen between individual values of strand breaks, micronuclei and chromat id/chromosome breaks and certain immunological parameters. (C) 1999 Elsevie r Science B.V. All rights reserved.