Objective: We previously reported that total suspended particulates exposure (a measure of air pollution) at the time of birth was related to increased postmenopausal breast cancer risk. In this study, we examined breast cancer risk in relation to exposure to air pollution from traffic emissions throughout life.
Methods: We conducted a case-control study of breast cancer. Participants were women, aged 35-79, residents of Erie and Niagara Counties. Cases had incident, primary, histologically confirmed breast cancer. Controls were randomly selected from the population, frequency-matched on age and race. Using lifetime residential histories, exposure to traffic emissions was modeled for each woman using her residence as a proxy. Estimates were calculated for residence at menarche, her first birth, and 20 and 10 years before interview. Unconditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI).
Results: Higher exposure to traffic emissions at the time of menarche was associated with increased risk of premenopausal breast cancer (OR 2.05, 95% CI 0.92-4.54, p for trend 0.03); and at the time of a woman's first birth for postmenopausal breast cancer (OR 2.57, 95% CI 1.16-5.69, p for trend 0.19). Statistically significant associations were limited to lifetime non-smokers; there was a significant interaction between exposure at time of menarche and smoking for premenopausal women.
Conclusion: Our findings add to accumulating evidence that early life exposures impact breast cancer risk and provide indication of potential importance of traffic emissions in risk of breast cancer.