ISEE 2007 CONFERENCE ABSTRACTS SUPPLEMENT: Abstracts
Terbufos is one of the most commonly used organophosphate insecticides (OPs) in the United States. OPs are classified as probable human carcinogens by IARC, although the human carcinogenicity for specific OPs is unknown. We investigated exposure to terbufos and cancer incidence in the Agricultural Health Study, a prospective cohort study of 57,311 licensed pesticide applicators.
Materials and Methods:
49,955 cohort members were included in the analysis. The average follow-up was 8.25 years. Cases included incident primary cancer diagnosed between December 1993 and December 2003 (n=2572). Self-administered questionnaires were used to obtain information about exposure to terbufos, 49 other pesticides, and other potential confounders. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated with proportional hazards models, controlling for age, sex, education, smoking (pack-years), alcohol consumption, family history of cancer, year at enrollment, state of residence (Iowa/North Carolina), and the 5 pesticides most highly associated with terbufos. Categories of lifetime exposure-days to terbufos were based on tertiles of the exposure distribution for all the exposed cancer cases combined.
Lifetime exposure-days of terbufos was positively associated with all cancer combined (P trend = 0.005). Separate analyses for each cancer site suggested that colon cancer (1st tertile HR = 0.96; 95% CI = 0.58–1.58; 2nd tertile HR = 0.76; 95% CI = 0.45–1.31; 3rd tertile HR = 1.42; 95% CI = 0.90–2.25; P trend = 0.15) and leukemia (1st tertile HR = 1.59; 95% CI = 0.79–3.22; 2nd tertile HR = 1.55; 95% CI = 0.75–3.18; 3rd tertile HR = 1.47; 95% CI = 0.68–3.18; P trend = 0.39) may be positively associated with lifetime exposure-days of terbufos. None of the other cancer sites was clearly associated with terbufos.
Although these results are preliminary and the number of cancer cases for specific sites was relatively small, they suggest that terbufos may be positively associated with colon cancer and possibly leukemia.