Analysis of Pesticide Exposure and DNA Damage in Immigrant Farmworkers

ABSTRACT

In the last decade, the Comet assay has been used increasingly in studies of workers potentially exposed to genotoxic substances in the workplace or environment. Significant increases in DNA damage measured with the Comet assay has been reported in lymphocytes of agricultural workers; however, less intrusive means of biomonitoring are needed in epidemiological investigations. This study was designed to use the Comet assay to describe the association of markers of DNA damage in oral leukocytes with biomarkers of pesticide exposure in 134 farmworkers working in berry crops in Oregon compared to control populations. The authors also examined the extent of DNA damage in young workers compared to adults and the effect of work histories, lifestyle factors, and diet on markers of DNA damage. Urinary levels of organophosphate pesticides were low at the time of sampling; however, mean levels of the Captan metabolite tetrahydrophthalimide (THPI) were found to be shifted significantly higher in the farmworkers (0.14 μg/ml) compared to controls (0.078 μg/ml) (one-sided p value = .01). Likewise, the combined molar equivalent of all dialkylphosphate metabolites was marginally higher in farmworkers (p value = .05). The mean tail intensity was significantly greater for agricultural workers compared to controls (one-sided p value <.001), indicating more DNA damage in the oral leukocytes. On average, the mean tail intensity was 10.9 units greater for agricultural workers (95% CI: 6–16 units greater). Tail moment was also significantly greater for agricultural workers compared to nonagricultural workers (one-sided p value <.001). No Comet parameter was significantly associated with years spent working in agriculture, age, sex, body mass index, diet, and alcohol or tobacco use. The results of this study demonstrate the feasibility for using the Comet assay in biomonitoring studies of farmworkers. Additional studies are needed to examine the effects of different pesticide types on DNA damage and to capture the temporal relationship between exposure to agricultural chemicals and changes in Comet parameters.

KEYWORDS:

• Organophospate pesticides
• comet assay
• farmworkers
• agriculture
• genotoxicity
• occupational exposure

This publication was supported by NIOSH grant number R01 OH008057. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NIOSH.

The authors would like to thank the farmworkers in Oregon who participated in this study and to acknowledge the field technical assistance provided by Kent Anger of Oregon Health & Science University. The authors also thank R. McCauley and Eric Stern for their graphic technical support on this manuscript.