Source apportionment of volatile organic compounds in a Philadelphia fenceline community: results from THRIVEair.

BACKGROUND: Urban exposure to volatile organic compounds (VOCs) is associated with several adverse health outcomes, including cancers and respiratory outcomes. We conducted a year-long VOC monitoring campaign in South Philadelphia to evaluate the impacts of traffic and redevelopment of a former oil refinery site on local air quality. Benzene was the community's primary pollutant of concern, but we measured a broader suite of VOCs to enable source apportionment, as presented here. METHODS: In partnership with Philly Thrive, a Philadelphia-based environmental justice organization, we developed a community-responsive monitoring design and collected one-week integrated samples of 38 VOCs at 20 sites from July 2023 to June 2024 using passive thermal desorption tubes. We summarized concentrations of VOCs by land use and traffic density, and identified potential sources using toluene:benzene (T/B) ratio and (m,p)-xylenes:ethylbenzene (X/E) ratios. We employed positive matrix factorization (PMF) to apportion VOC sources. RESULTS: VOC concentrations were generally higher in industrial vs. non-industrial and high- vs. low-traffic areas. Benzene, the compound of greatest community concern, occurred at low concentrations overall (median 1.21 µg/m³; range: 0.31-9.05 µg/m3), while (m,p)-xylenes emerged as a pollutant of concern in industrial areas. T/B and X/E ratios were higher among industrial and high-traffic sites, suggesting fresh (less photochemically aged) emissions of benzene derivatives. PMF identified five VOC sources: (1) vehicular exhaust, (2) gasoline evaporation, (3) industrial solvents, (4) background pollution, and (5) mixed industry suggestive of auto repair. SIGNIFICANCE: Using a community-responsive study design, we characterized ambient VOCs in a pollution-burdened area of Philadelphia. Source apportionment confirmed traffic as a primary VOC source and identified the former refinery site as a source of gasoline and petroleum evaporative emissions, with industrial solvent use as an additional contributor. IMPACT: THRIVEair was a spatially saturated, community-responsive volatile organic compound (VOC) monitoring campaign during the decommissioning and redevelopment of a former refinery site in an industrialized urban area in South Philadelphia. Leveraging data on 38 VOCs, we identified five major VOC sources: (1) vehicular exhaust, (2) gasoline evaporation, (3) industrial solvents, (4) background pollution, and (5) a mixed industrial source suggestive of auto repair. Our study documents air quality impacts of rapid changes in industrial land use at a spatial and temporal scale not previously available in this under-resourced urban community.