The Effect of Specific Ambient Air Pollutants on Breast Cancer Incidence Across US Counties

Abstract: Objectives: Air pollution is an insufficiently studied carcinogenic factor for breast cancer. This assertion is supported by studies that have underscored the necessity for more precise exposure models and larger study populations to better understand the relationship between air pollutants and the risk of breast cancer. Despite the existing body of research examining air pollution as a potential carcinogenic factor for breast cancer, the complexity and variability of this issue necessitate continued exploration. Previous studies have shown that ambient air pollutants such as NO2 could increase breast cancer incidence in small-scale analysis. The goal of this study is to examine the relationship between air pollutant concentrations and Age-Standardized Incidence Rates (ASIR) of breast cancer in various counties across the United States. Methods: The data set analyzed, composed of data from 128 counties, was constructed from publicly available data from the National Cancer Institute, the Environmental Protection Agency, and the US Census Bureau. Air pollution factors examined include NO2, O3, particulate matter (PM2.5 and PM10), and AQI, controlling for socioeconomic factors. Two separate time periods of predictive data were examined: the five-year period before (2011-2015) and the five-year period during the breast cancer data set (2016-2020). A multiple regression analysis was performed for each time frame as well as simple linear regressions for specific variables. Results: The multiple regression analysis found that on average, each 1% increase in uneducatedness is associated with a decrease of 1.647 breast cancer cases per 100,000 for the 2011-2015 model (p < 0.01) and with a decrease of 1.308 cases per 100,000 for the 2016-2020 model (p < 0.001). The 2016-2020 model found that on average, each 1 ppb increase in NO2 concentration is associated with an increase of 0.455 cases per 100,000 (p < 0.01), and each 1 ppm increase in O3 concentration is associated with a decrease of 742.27 cases per 100,000 (p < 0.01). Conclusion: Current air pollutant concentrations of NO2 were positively associated with breast cancer incidence, verifying past literature. O3 concentrations, a less studied pollutant, were unexpectedly negatively associated with breast cancer incidence. This study serves to understand the effect of ambient, low-concentration, and likely traffic-influenced air pollution on breast cancer incidence in the United States. It contrasts and expands upon previous cohort and case-control studies, which focus on groups of individuals, on a larger countrywide scale utilizing recent, specific, and county-by-county incidence and air pollution data in multiple linear regression to focus on the general population.