Association Between Particulate Matter 2.5 and Breast Cancer Mortality in California—A Place-Based Cross-Sectional Study

To investigate the place-based association between BCM and air pollution in middle-aged (45–64) and older-aged women (65+) in California at the zip code level, secondary data were collected from the California Department of Public Health (CDPH) Data and Vital Statistics, CalEnviroScreen 4.0, and the American Community Survey (ACS) from the Census. Multiple linear regression was used to test the significance between air pollution and age-standardized BCM rates. The results indicate a significant association between PM2.5 and age-standardized BCM rates for both the middle-aged and older-aged groups (β = 3.73, 95% CI [2.89, 4.58]; β = 5.33, 95% CI [2.75, 8.32], respectively). Furthermore, we found evidence of effect modification by the concentration of Hispanic women (β = −6.73, 95% CI [−9.37, −4.08]. This study provides evidence of a significant spatial association between PM2.5 and BCM rates, which has policy implications for stricter air quality regulations and urban planning policies. Further research is needed to establish causality and the mechanism of action at the population level.