Abstract 3456: The role of particulate matter exposure in racial differences in colorectal cancer mortality in metropolitan Detroit
Authors: Snider Natalie Gail , Hastert Theresa , Dyson Gregory , Gronlund Carina , Stoffel Elena M. , Peters Ed , Rozek Laura , Schwartz Ann , Purrington Kristen 
Published: March 2024

Abstract
Colorectal cancer (CRC) is the third most diagnosed cancer in the United States and the third leading cause of cancer-related deaths. Non-Hispanic Black (NHB) individuals have the highest rates of CRC incidence and mortality in the United States. These disparities are highly influenced by social determinants of health (SDOH). Neighborhood quality, a well-established SDOH, has been shown to influence cancer outcomes, oftentimes more heavily in minorities. Additionally, neighborhood quality is known to influence an individual’s risk of exposure to harmful environmental contaminants including ambient air pollution as a result of systemic racism such as segregation and historic redlining, leading to environmental injustices. Fine particulate matter (PM2.5) exposure has been shown to increase the risk of CRC mortality, however, its effects by race have not yet been examined. We sought to understand whether higher rates of exposure to PM2.5 played a role in racial differences in CRC survival in metropolitan Detroit. Patient data including census tract at diagnosis, demographics, and clinical features were obtained from the metropolitan Detroit cancer surveillance system registry. Ambient PM2.5 concentration data at the census tract were obtained from the Environmental Protection Agency (EPA) Remote Sensing Information Gateway (RSIG) and converted to annual averages to use in an interval-censored Cox proportional hazards regression model. We found that PM2.5 exposure partly attenuated the effect of race on overall mortality in all patients (NHB vs NHW: Hazard Ratio (HR) = 1.24, 95% Confidence Interval (CI) 1.20 - 1.27, p &lt; 0.0001, NHB vs NHW after accounting for PM2.5: HR = 1.19, 95% CI = 1.16 - 1.23 p &lt; 0.0001) and the effect was stronger among patients under 50 than over 50, though still significant in both models. Additionally, the effect of PM2.5 on mortality was much stronger among NHB patients than NHW patients (NHB HR = 1.30, 95% CI = 1.17 - 1.45, p &lt; 0.0001; NHW HR = 1.06, 95% CI = 1.02 - 1.11 p = 0.008) and especially strong among NHB patients under 50 (HR = 2.51, 95% CI = 2.38 - 3.38, p &lt; 0.0001) compared to any other group. We conclude that ambient air pollution, particularly PM2.5, disproportionately affects mortality risk in NHB CRC patients. These results highlight the importance of environmental justice research in biomedical research, and the need for a better understanding of environmental impact on tumor biology to prevent tumor progression and mortality among all patients.
Citation Format: Natalie Gail Snider, Theresa Hastert, Gregory Dyson, Carina Gronlund, Elena M. Stoffel, Ed Peters, Laura Rozek, Ann Schwartz, Kristen Purrington. The role of particulate matter exposure in racial differences in colorectal cancer mortality in metropolitan Detroit [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3456.