Long-Term Air Pollution Exposure And Breast Cancer

Abstract

Introduction Over the past 20 years, the incidence rates of breast cancer rose rapidly in Taiwan. Previous studies have found that incidence of breast cancer in urban area is higher than in rural areas. This finding led to speculation that urban environmental exposures may play a role in the etiology of breast cancer. We examined the association between long-term ambient air pollution exposure and breast cancer risk in Taiwan. Methods We identified 7,707 cases of newly diagnosed breast cancer (ICD-9-CM:174) in 2009 and 30,828 age-matched controls from Taiwan's National Health Insurance claims. Air pollution exposure concentrations for each criteria pollutant (including ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and particles with aerodynamic diameters less than 10 µm (PM10) and less than 2.5µm (PM2.5)) were estimated, using a Bayesian maximum entropy method based on residential township codes from 1998 to index date (i.e., date of first breast cancer diagnosis). Logistic regression models were used to estimate the effects of air pollution on breast cancer after controlling for potential confounders. Results We found that ambient PM10 and PM2.5 exposures were associated with increased breast cancer risk (ORs for PM10, 1.11, 95% CI=1.00-1.23; for PM2.5, 1.13, 95% CI=1.03-1.25 per interquartile range increased), but not for other pollutants. Results for PM10 and PM2.5 attenuated (ORs for PM10, 1.07, 95% CI=0.97 1.18; for PM2.5, 1.05, 95% CI=0.96 1.15 per interquartile range increased) when we lagged the exposure for three years (e.g., three years before index date). Conclusions Our results suggest that ambient PM exposures may be associated with increased risk for breast cancer. Further research to investigate longer-term of exposure on breast cancer risk is needed.