GENOTOXICITY IN WORKERS EXPOSED TO METHYL-BROMIDE

To address the genotoxicity of in vivo methyl bromide (CAS 74-83-9) ex posure in humans, we collected blood and oropharyngeal cells as part o f a cross-sectional morbidity study of methyl bromide-exposed fumigati on workers and their referents. Micronuclei were measured in lymphocyt es and oropharyngeal cells, and hypoxanthine-guanine phosphoribosyl tr ansferase gene (hprt) mutations were measured in lymphocytes. A total of 32 workers and 28 referents provided specimens. Among current non-s mokers, mean hprt variant frequencies (Vfs) were found to be elevated among workers compared to referents (geometric mean: workers = 4.49 x 10(-6), referents = 2.96 x 10(-6); two-sided p = 0.22); this differenc e was more pronounced among workers with 4 h or more of recent methyl bromide exposure compared to referents (geometric mean: workers = 6.56 x 10(-6), referents = 2.96 x 10(-6); two-sided p = 0.06). Mean oropha ryngeal cell micronuclei were higher among workers compared to referen ts (mean: workers = 2.00, referents = 1.31; two-sided p = 0.08); the r esults were similar when workers with 4 h or more of recent methyl bro mide exposure were compared to referents (mean: workers = 2.07, refere nts = 1.31; two-sided p = 0.13). No consistent differences between wor kers and referents were observed for frequencies of kinetochore-negati ve lymphocyte micronuclei, or kinetochore-positive lymphocyte micronuc lei. The study was limited by a sample size sufficient only for detect ing relatively large differences, absence of a reliable method to meas ure the intensity of workplace methyl bromide exposures, and relativel y infrequent methyl bromide exposure (e.g., the median length of expos ure to methyl bromide during the 2 weeks preceding the survey was 4 h) . In conclusion, our findings provide some evidence that methyl bromid e exposure may be associated with genotoxic effects in lymphocytes and oropharyngeal cells. Further study on the genotoxicity of methyl brom ide exposure in humans is warranted. (C) 1998 Elsevier Science B.V. Al l rights reserved.