Evaluating the environmental justice dimensions of odor in Denver, Colorado.

Background: Odors are a documented environmental justice challenge in Denver, Colorado. Complaints are an important modality through which residents express their concerns.

Objective: We investigated disparities in environmental justice related-variables, such as home and workplace census block groups (race/ethnicity, education levels, renter-occupied housing, median income and median home values, gentrification) by locations of odor complaints as well as that of potential malodorous facilities. We report key themes identified in complaints.

Methods: We obtained odor complaints for 2014-2023 and the locations of facilities required to submit an odor management plan as of 2023 from the Denver Department of Public Health and Environment. We downloaded residential census block group-level socioeconomic data from the 2016-2020 American Community Survey and workplace-based socioeconomic data from the Longitudinal Employer-Household Dynamics dataset for 2020. We assessed exposure to potential malodorous facilities and complaints within each census block group. We investigated exposure disparities by comparing distributions of environmental justice-related variables based on whether a complaint has been made against a facility, and census block group-level odor intensity categories. We used unsupervised machine learning to identify themes from the odor complaints.

Results: Less privileged census block groups were more likely to contain a potential malodorous facility. Importantly, our study also reveals disparities in the location of facilities, not just in traditional residence/-based environmental justice-related variables, but in workplace/-based factors as well. Our work points to the need to broaden our understanding of the structural racism forces that shape disparities from residential-based forces such as segregation to others such as access to transportation that result in workplace disparities. We did not observe similar disparities for odor complaints. Specific facilities were mentioned repeatedly in the complaints received.

Impact: Our study adds to the growing literature on disparities observed in exposure to odor using locations of potential malodorous facilities and complaints as a proxy.