Characterization of indoor particle sources using continuous mass and sizemonitors

A comprehensive indoor particle characterization study was conducted in nin e Boston-area homes in 1998 in order to characterize sources of PM in indoo r 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 colle cted during the extensive monitoring efforts were 24-hr elemental/organic c arbon (EC/OC) particulate data as well as semi-continuous air exchange rate s and time-activity information. This rich data set shows that indoor particle events tend to be brief, inte rmittent, and highly variable, thus requiring the use of continuous instrum entation for their characterization. In addition to dramatically increasing indoor PM2.5 concentrations, these data demonstrate that indoor particle e vents can significantly alter the size distribution and composition of indo or particles. Source event data demonstrate that the impacts of indoor acti vities are especially pronounced in the ultrafine (d(a) less than or equal to 0.1 mu m) and coarse (2.5 less than or equal to d(a) less than or equal to 10 mu m) modes. Among the sources of ultrafine particles characterized i n this study are indoor ozone/terpene reactions. furthermore, EC/OC data su ggest that organic carbon is a major constituent of particles emitted durin g indoor source events. Whether exposures to indoor-generated particles, pa rticularly from large short-term peak events, may be associated with advers e health effects will become clearer when biological mechanisms are better known.