Contribution of traffic emissions to PM2.5 concentrations at bus stops in Denver, Colorado

Sustainability
By: , and 

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Abstract

Individuals are routinely exposed to traffic-related air pollution on their commutes, which has significant health impacts. Mitigating exposure to traffic-related pollution is a key urban sustainability concern. In Denver, Colorado, low-income Americans are more likely to rely on buses and spend time waiting at bus stops. Evaluating the contribution of traffic emissions at bus stops can provide important information on risks experienced by these populations. We measured PM2.5 constituents at eight bus stops and one background reference site in Denver, in the summer of 2023. Source profiles, including gasoline emissions from traffic, were estimated using Positive Matrix Factorization (PMF) analysis of PM2.5 constituents collected at a Chemical Speciation Network site in our study region. The contributions of the different sources at each bus stop were estimated by regressing the vector of species concentrations at each site (dependent variable) on the source-profile matrix from the PMF analysis (independent variables). Traffic-related emissions (~2.5–6.6 μg/m3) and secondary organics (~3–5 μg/m3) contributed to PM2.5 at the bus stops in our dataset. The highest traffic-related emissions-derived PM2.5 concentrations were observed at bus stops near local sources: a gas station and a car wash. The contribution of traffic-related emissions was lower at the background site (~1 μg/m3).

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Publication type Article
Publication Subtype Journal Article
Title Contribution of traffic emissions to PM2.5 concentrations at bus stops in Denver, Colorado
Series title Sustainability
DOI 10.3390/su17177707
Volume 17
Issue 17
Publication Date August 27, 2025
Year Published 2025
Language English
Publisher MDPI
Contributing office(s) Geosciences and Environmental Change Science Center
Description 7707, 14 p.
Country United States
State Colorado
City Denver
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