Exposure to Industrial Air Toxics and Risk of Breast Cancer in California: The Multiethnic Cohort Study

OBJECTIVE: Estimate breast cancer risk associated with residential industrial air pollutant exposure. METHODS: We analyzed 53,313 women in the California Multiethnic Cohort (1993-1996) for associations between 15 industrial pollutants and breast cancer incidence. Using Environmental Protection Agency Toxic Release Inventory data, sites were linked to geocoded residential histories via quadratic decay models to estimate 5-year lagged exposures. Cox models calculated risk per interquartile range increase, stratified by race/ethnicity and hormone receptor status. RESULTS: Increased risk was associated with dichloromethane (hazard ratio [HR] = 1.17, 95% confidence interval [CI]: 1.05-1.29), tetrachloroethylene (HR = 1.53, CI: 1.39-1.69), 1,1,1-trichloroethane (HR = 1.77, CI: 1.65-1.91), diethanolamine (HR = 1.06, CI: 0.98-1.15), lead (HR = 1.02, CI: 1.00-1.03), and methyl ethyl ketone (HR = 1.27, CI: 1.15-1.41). Formaldehyde was associated only with hormone receptor-negative tumors (HR = 1.44, CI: 1.15-1.73). CONCLUSIONS: Residential exposure to certain industrial pollutants may increase breast cancer risk.