Real-time indoor PM2.5 monitoring in an urban cohort: Implications for exposure disparities and source control

Fine particulate matter (PM2.5) concentrations are highly variable indoors, with evidence for exposure disparities. Real-time monitoring coupled with novel statistical approaches can better characterize drivers of elevated PM2.5 indoors. We collected real-time PM2.5 data in 71 homes in an urban community of Greater Boston, Massachusetts using Alphasense OPC-N2 monitors. We estimated indoor PM2.5 concentrations of non-ambient origin using mass balance principles, and investigated their associations with indoor source activities at the 0.50 to 0.95 exposure quantiles using mixed effects quantile regressions, overall and by homeownership. On average, the majority of indoor PM2.5 concentrations were of non-ambient origin (>= 77%), with a higher proportion at increasing quantiles of the exposure distribution. Major source predictors of non-ambient PM2.5 concentrations at the upper quantile (0.95) were cooking (1.4-23 mu g/m(3)) and smoking (15 mu g/m(3), only among renters), with concentrations also increasing with range hood use (3.6 mu g/m(3)) and during the heating season (5.6 mu g/m(3)). Across quantiles, renters in multifamily housing experienced a higher proportion of PM2.5 concentrations from non-ambient sources than homeowners in singleand multifamily housing. Renters also more frequently reported cooking, smoking, spray air freshener use, and second-hand smoke exposure, and lived in units with higher air exchange rate and building density. Accounting for these factors explained observed PM2.5 exposure disparities by homeownership, particularly in the upper exposure quantiles. Our results suggest that renters in multifamily housing may experience higher PM2.5 exposures due to a combination of behavioral and building factors that are amenable to intervention.

Automated summary

Indoor concentrations of fine particulate matter (PM2.5) are highly variable, with different sources such as cooking and smoking playing a major role in contributing to elevated PM2.5 levels indoors. Renters in multifamily housing are more likely to be exposed to higher PM2.5 levels from non-ambient sources, such as cooking and smoking, compared to homeowners in single and multifamily housing. These disparities in PM2.5 exposure by homeownership can be explained by a combination of behavioral and building factors.