Does the elemental composition of indoor and outdoor PM2.5 accurately represent the elemental composition of personal PM2.5?

Abstract

The complex mixture of chemical and elemental constituents that comprise particulate matter (PM) is hypothesized to be, in part, responsible for its toxicity. Epidemiologic studies have identified specific components and sources of PM2.5 associated with adverse health outcomes, but the majority of these studies use the mass concentration of elements in outdoor PM2.5 at central monitoring sites as a surrogate for personal exposure. Personal exposure to PM2.5 and its elemental composition, however, may vary from stationary outdoor measurements. Here, we use concurrent indoor, outdoor, and personal sampling of PM2.5 and its elemental constituents along with personal and home characteristics, collected as a part of the Relationships of Indoor, Outdoor, and Personal Air (RIOPA) study to characterize the differences in PM2.5 among indoor, outdoor, and personal air samples. We found that personal exposure to PM2.5 and most elements were significantly correlated with, though frequently exceeded, both indoor and outdoor measurements. Principal component scores were used to determine that the mixture of elemental components in PM2.5 varies significantly across indoor, outdoor, and personal sample types. Using model-based clustering, we identified 7 clusters of RIOPA participants whose personal PM2.5 samples had similar patterns of elemental composition. Using this approach, two subsets of RIOPA participants were identified whose personal exposure to PM2.5 and elemental concentrations were significantly increased compared to both their indoor and outdoor levels. Collectively, our results suggest that the elemental composition of PM2.5 obtained at central monitoring stations do not accurately represent the overall elemental composition of personal PM2.5 exposure.