Background: We conducted a population-based case-control study to describe the relationship between occupational exposure to estrogenic chemicals and the occurrence of breast cancer in Cape Cod, Massachusetts.
Methods: Incident cases of breast cancer (n = 261) diagnosed from 1983 through 1986 and controls (n = 753) were interviewed to gather information on breast cancer risk factors and all full-time jobs held since age 18. Blinded exposure assessments were employed using the data from the NIOSH National Occupational Exposure Survey, chemical production and usage information, and the expert judgement of a certified industrial hygienist.
Results: Overall, 29.5% of cases and 32.5% of controls had probable occupational exposure to one or more xenoestrogens. Probable exposure to nonylphenol (21.5% of cases, 21.4% of controls), butyl benzyl phthalate (10.0% of cases, 13.2% of controls), BHA (7.3% of cases, 9.6% of controls), bisphenol A (9.6% of cases, 11.6% of controls), and 4-tert-butylphenol (2.7% of cases and 5.3% of controls) were relatively commons, while probable exposure to the other xenestrogens was rare. Only PCBs and 4-octylphenol were associated with moderate increase in the odds of breast cancer (PCBs: 5 exposed cases and 6 exposed controls, adjust odds ratio: 3.2, 95% CI = 0.8-12.2, and 4-octylphenol: 6 exposed cases and 5 exposed controls, adjusted odds ratio: 2.9, 95% CI = 10.8).