Characterization of Indoor Particle Sources Using Continuous Mass and Size Monitors

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 24-hr 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 PM2.5 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 < or = 0.1 micron) and coarse (2.5 < or = da < or = 10 microns) 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.

Elevated personal exposure to particulate matter from human activities in a residence

“…By comparison, dancing on a rug produced stationary indoor concentrations only 2.4 times as high as similar activities on wood flooring. This result agrees with Long et al (2000), who found that activities on a carpet produced indoor PM 2.5 concentrations 2 times as high as similar activities on wood or linoleum. For this study, peak 3-min PM 5 concentrations during 15-min activities of vacuuming the first floor, vacuuming the bedrooms, walking on the first floor, and walking in the basement were 81, 69, 98, and 165 mg/m 3 , respectively.…”

“…This study found that the dry dusting and one person walking around contributed 32 and 15 mg/m 3 , respectively, to indoor PM 2.5 concentrations. In a study of nine homes in the Boston area, Long et al (2000) found that dusting and vigorous walking contributed 23 (SD ¼ 23) and 12 (SD ¼ 9.1) mg/m 3 , respectively, to indoor PM 2.5 concentrations. Also, this study found that dancing on a rug produced personal PM 2.5 concentrations 6 times as high as dancing on a wood floor.…”

“…Investigating indoor sources of PM will improve our understanding of what humans are actually exposed to and how to reduce this exposure. Long et al (2000) found that indoor sources of PM are typically short-term, high-concentration events that emit primarily ultrafine (particle diameter D p r0.1 mm) and coarse mode (2.5rD p r10 mm) particles. Although the health effects of short-term PM exposures are not well understood, several recent studies have correlated disease symptoms with increased ambient short-term PM.…”

“…A few studies have directly examined the effect of specific human activities on indoor PM concentrations (Thatcher and Layton, 1995;Long et al, 2000). These studies found that walking, dusting, vacuuming, and general cleaning dramatically increased indoor concentrations of PM greater than 1 mm.…”

Predictors of concentrations of nitrogen dioxide, fine particulate matter, and particle constituents inside of lower socioeconomic status urban homes

“…The current study also identified resuspension activities as affecting PM exposure. These activities, often treated as episodic events increasing short-term indoor particle concentrations, (Thatcher and Layton, 1995;Abt et al, 2000;Long et al, 2000) in our study seemed to also affect longer-term indoor levels. The additional significance of resuspension factors in our study may be associated with the smaller volumes and greater crowding (higher occupant densities) among our participants, as opposed to the single-family homes generally sampled in other studies.…”