S-ethyl-N,N-dipropylthiocarbamate (EPTC) exposure and cancer incidence among male pesticide applicators in the Agricultural Health Study, a prospective cohort Free

B128

EPTC (S-ethyl-N,N-dipropylthiocarbamate) is a member of a major class of herbicides known as thiocarbamates used in the agricultural industry. Little is known about the potential human carcinogenicity associated with routine use of EPTC. In a prospective cohort of licensed pesticide applicators in Iowa and North Carolina enrolled between 1993 and 1997 we examined the association between self-reported EPTC exposure and cancer incidence. Cancers diagnosed from enrollment through December 2004 were identified by linkage to state cancer registries. Among the 9,878 EPTC pesticide applicators, 470 cancer diagnoses were made compared to 1,824 among the 38,500 participants reporting no use. The rate ratio (RR) and 95% confidence intervals (95% CI) were estimated using Poisson regression. EPTC exposure was evaluated using two quantitative metrics: lifetime exposure days and intensity-weighted lifetime exposure days, a measure that takes into account application factors that modify personal exposure likelihood. EPTC was associated with an increased risk for colon cancer (RR=2.09, 95% CI: 1.26, 3.47) in the highest tertile of both lifetime exposure days (p-trend = 0.008) and intensity-weighted lifetime exposure days (RR=2.05, 95% CI: 1.34, 3.14 (p-trend=0.010)). No other cancer site was found to have a statistically significant association between increasing exposure to EPTC and cancer risk using either exposure metric. These analyses are based on a relatively small number of cases in the highest exposure tertile, limiting the statistical power to detect associations. Nevertheless, the potential association between EPTC exposure and an increased risk for developing colon cancer warrants further investigation.