| Cytogenetic Effects from Exposure to Mixed Pesticides and the Influence from Genetic Susceptibility William W. Au, Carlos H. Sierra-Torres, Nohelia Cajas-Salazar, Bryan K. Shipp, and Marvin S. Legator Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, Galveston, Texas, USA Abstract
Exposure to pesticides remains a major environmental health problem. Health risk from such exposure needs to be more precisely understood. We conducted three different cytogenetic assays to elucidate the biological effects of exposure to mixed pesticides in 20 Costa Rica farmers (all nonsmokers) compared with 20 matched controls. The farmers were also exposed to dibromochloropropane during the early employment years, and most of them experienced sterility/fertility problems. Our data show that the farmers had consistently higher frequencies of chromosome aberrations, as determined by the standard chromosome aberration assay, and significantly abnormal DNA repair responses (p < 0.05) , as determined by the challenge assay, but no statistically significant differences in the tandem-probe fluorescence in situ hybridization (FISH) assay (p > 0.05) . Genotype analysis indicates that farmers with certain "unfavorable" versions of polymorphic metabolizing genes (cytochrome P4502E1, the glutathione S-transferases mu and theta, and the paraoxonase genes) had significantly more biological effects, as determined by all three cytogenetic assays, than both the farmers with the "favorable" alleles and the matched controls. A unique observation is that, in individuals who had inherited any of the mentioned "unfavorable" alleles, farmers were consistently underrepresented. In conclusion, the Costa Rican farmers were exposed to genotoxic agents, most likely pesticides, which expressed the induction of biological and adverse health effects. The farmers who had inherited "unfavorable" metabolizing alleles were more susceptible to genotoxic effects than those with "favorable" alleles. Our genotype data suggest that the well-recognized "healthy worker effect" may be influenced by unrecognized occupational selection pressure against genetically susceptible individuals. Key words: chromosome aberrations, cytogenetic effects, FISH, pesticide exposure, susceptibility. Environ Health Perspect 107:501-505 (1999) . [Online 10 May 199] http://ehpnet1.niehs.nih.gov/docs/1999/107p501-505au/ abstract.html Address correspondence to W.W. Au, Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, Room 2.102 Ewing Hall, 700 Harborside Drive, Galveston, TX 77555-1110 USA. Telephone: (409) 772-1545. Fax: (409) 772-9108. E-mail: william.au@utmb.edu We gratefully acknowledge the assistance from M. Stewart (subject recruitment) , S. Szucs (cytogenetic analyses) , S. Abdel-Rahman (genotype analyses) , and J. Grady (review of manuscript) . The study was supported by Miller and Associates, P30 ES 06676, for genotype analyses, the COLCIENCIAS-Fulbright-LASPAU Fellowship Program, and the T32 ES 07254 training grant. Received 27 July 1998 ; accepted 2 October 1998.
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