Evaluating the role of ambient air pollution in racial disparities of colorectal cancer incidence and survival in metropolitan Detroit

Abstract Colorectal cancer (CRC) is the third most diagnosed cancer in the United States and the third leading cause of cancer-related deaths. Moreover, Non-Hispanic Black (NHB) individuals have the highest rates of CRC incidence and mortality in the United States. We have become increasingly aware of the potential impact of social determinants of health (SDOH) on colorectal physiology and carcinogenesis. Other than individual and neighborhood level socioeconomic status (SES), neighborhood quality can also affect an individual’s risk of exposure to harmful environmental contaminants including ambient air pollution. Moreover, as NHB individuals are more likely to live in areas of lower area-level SES they experience these effects even further. We sought to understand whether higher exposure rates to fine particulate matter (PM2.5) played a role in racial differences in CRC incidence and survival in metropolitan Detroit. To do this, we obtained data from the Environmental Protection Agency (EPA) Environmental Justice Mapping and Screening Tool through the Georgetown University Environmental Impact Data Collective (EIDC) and patient data from the Metropolitan Detroit Cancer Surveillance System (MDCSS) registry. Incidence rates were calculated using population data from the American Community Survey. Associations between PM2.5 exposure and CRC incidence were estimated using Poisson modeling. Data were obtained for NHB (n=3778) and Non-Hispanic White (NHW) (n=9727) individuals diagnosed with invasive CRC between 2010 and 2019 in Wayne, Oakland, and Macomb counties, including their geocoded census tract at diagnosis as well as demographic and clinical features. Vital status was reported as months from the date of diagnosis to either death or last contact. PM2.5 metrics were converted to the national percentile of PM2.5 in the air utilizing the Bayesian space-time downscaling fusion model for derived estimates of air quality at the census tract level. Survival was assessed using Cox Proportional Hazards modeling. We found that an increase in the PM2.5 percentile increased the risk for CRC overall for NHB and NHW patients (Relative Risk [RR] = 1.80, 95% Confidence Interval [CI] = 1.55 - 2.08, p-value <0.0001). This association was even stronger among NHB patients (RR = 7.94, 95% CI = 5.45 - 11.52, p-value < 0.0001), but was not statistically significant among NHW patients (RR = 1.12, 95% CI = 0.95 – 1.32, p-value = 0.16). PM2.5 exposure was not associated with survival overall or stratified by race. We conclude that ambient air pollution, particularly PM2.5, increases the risk of CRC cancer and disproportionately affects NHB patients but may not play a role in mortality risk. These results highlight the importance of environmental justice research in biomedical research and the need for a better understanding of the etiology of CRC within and among differing genetic ancestries and races by evaluating the genetic and epigenetic differences in patient tumor samples. Citation Format: Natalie G. Snider, Theresa Hastert, Ed Peters, Elena M. Stoffel, Laura Rozek, Ann Schwartz, Kristen Purrington. Evaluating the role of ambient air pollution in racial disparities of colorectal cancer incidence and survival in metropolitan Detroit [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr PR019.