Characterization of Indoor Particle Sources Using Continuous Mass and Size Monitors

TLDR

Exposure to indoor-generated particles, especially large short‑term peaks, may be linked to adverse health effects, but this link will become clearer as biological mechanisms are better understood. The study aimed to characterize indoor PM sources by conducting a comprehensive particle characterization in nine Boston‑area homes in 1998. Using state‑of‑the‑art continuous PM₂.₅ and size‑distribution sampling, the authors monitored nine homes—five over two seasons—for week‑long periods, collecting 24‑hour EC/OC data, semi‑continuous air‑exchange rates, and time‑activity information. The data revealed that indoor particle events are brief, intermittent, and highly variable, dramatically raising PM₂.₅ concentrations and altering size distribution and composition, with pronounced effects in ultrafine and coarse modes driven in part by indoor ozone/terpene reactions and organic carbon emissions.

Abstract

ABSTRACT A comprehensive indoor particle characterization study was conducted in nine Boston-area homes in 1998 in order to characterize sources of PM in indoor environments. State-of-the-art sampling methodologies were used to obtain continuous PM2.5 concentration and size distribution particulate data for both indoor and outdoor air. Study homes, five of which were sampled during two seasons, were monitored over week-long periods. Among other data collected during the extensive monitoring efforts were 24hr elemental/organic carbon (EC/OC) particulate data as well as semi-continuous air exchange rates and time-activity information. This rich data set shows that indoor particle events tend to be brief, intermittent, and highly variable, thus requiring the use of continuous instrumentation for their characterization. In addition to dramatically increasing indoor PM25 concentrations, these data demonstrate that indoor particle events can significantly alter the size distribution and composition of indoor particles. Source event data demonstrate that the impacts of indoor activities are especially pronounced in the ultrafine (da < 0.1 um) and coarse (2.5 < da < 10 |um) modes. Among the sources of ultrafine particles characterized in this study are indoor ozone/terpene reactions. Furthermore, EC/OC data suggest that organic carbon is a major constituent of particles emitted during indoor source events. Whether exposures to indoor-generated particles, particularly from large short-term peak events, may be associated with adverse health effects will become clearer when biological mechanisms are better known.