DDT and related compounds and risk of pancreatic cancer.

BACKGROUND: A cohort mortality study among 5886 chemical manufacturing workers was completed in 1987 and showed increased mortality due to pancreatic cancer.
PURPOSE: We conducted a nested case-control study of pancreatic cancer among these chemical manufacturing workers to identify risk factors for this disease.
METHODS: Twenty-eight verified cases of pancreatic cancer and 112 matched controls were studied. Next of kin of each subject were interviewed to determine lifestyle factors, including tobacco, alcohol, and coffee consumption. Written work records and interviews with co-workers were used to determine chemical exposures at the plant under study.
RESULTS: DDT was associated with pancreatic cancer (risk ratio [RR] for ever exposed compared with never exposed = 4.8; 95% confidence interval = 1.3-17.6). Among subjects who had a mean exposure to DDT of 47 months, the risk was 7.4 times that among subjects with no exposure. Two DDT derivatives, Ethylan and DDD, were additionally associated with pancreatic cancer (RR = 5.0 and 4.3, respectively); exposures to these two chemicals were correlated, and it was not possible to determine whether each acted independently of the other. Smoking was identified as an independent risk factor, but controlling for smoking (and other potential confounders) in the analyses did not appreciably alter the risks seen for DDT, DDD, or Ethylan.
CONCLUSIONS: Exposure to DDT was associated with pancreatic cancer. The association was not explained by exposure to lifestyle factors or other chemicals, and risk increased with both duration of exposure and latency since first exposure. IMPLICATIONS: These results may indicate that DDT can cause pancreatic cancer in humans under circumstances of heavy and prolonged exposure.