Abstract
Fine particulate matter (PM(2.5)) is a ubiquitous air pollutant with known socioeconomic disparities in exposure related to both ambient and indoor sources. Understanding how common indoor behaviors such as smoking, cooking, candle or incense burning, and air freshener use contribute to indoor PM2(.5) exposure in public housing can inform interventions to protect residents' health. PM2(.)5 data were collected via PurpleAir monitors for one week within 138 units of a single public housing development in New England, United States and corrected via an additive relative humidity model. Study participants completed a pre-monitoring survey and a post-monitoring survey of in-unit PM(2.5)-related behaviors. Participants' weekly average in-unit PM(2.5) levels were variable, ranging from 3.6 μg/m(3) to 142.0 μg/m(3), with a mean of 19.7 μg/m(3). Two-thirds (65.9%) of households' average levels exceeded the EPA annual outdoor standard of 9 μg/m(3), a heuristic reference given the lack of national indoor guidelines. A multivariable model predicting in-unit average PM2(.5) based on resident behaviors found significant associations between elevated PM2(.)5 and past-week tobacco smoking (121% higher PM2(.)5), weekly or more cannabis use (56% higher), and living in an apartment building rather than a townhome (26% higher). Cannabis use, which is studied here for the first time in an uncontrolled residential setting, may represent an underappreciated risk factor for exposure. Interventions directed at mitigating indoor smoking of both tobacco and cannabis may be effective at reducing average in-unit PM(2.5) exposure in multifamily housing, as compared to combatting other known indoor sources of PM(2.5).