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ASSESSMENT OF INDOOR, OUTDOOR, AND PERSONAL PM DIFFERENCES
Citation:
LaRosa, L., T J. Buckley, C HowardReed, AND L A. Wallace. ASSESSMENT OF INDOOR, OUTDOOR, AND PERSONAL PM DIFFERENCES. Presented at PM 2000 AWMA Conference, Charleston, SC, January 24-28, 1999.
Description:
Epidemiological studies have consistently demonstrated that a correlation exists between daily ambient particle concentrations and health effects.' One major area of concern with respect to particulate matter (PM) is the relationship between indoor and outdoor particle concentrations- Indoor particle concentrations are greatly affected by human activities, often resulting in poor correlations between indoor and outdoor PM concentrations. Z Indoor particle concentrations are of concern because it has been shown that people spend the majority of their time indoors. The Particle Total Exposure Assessment Methodolody (PTEAM) study/ detected an unexplained increase in personal exposure to PM10 when compared to concurrent stationary monitoring concentrations. This phenomenon has been termed the "personal cloud". The main objectives of this study were to: 1) compare personal, indoor, and outdoor PM concentrations; 2) further characterize the personal cloud - specifically, does wearing clothes elevate personal PM concentrations; and 3) determine the contribution of pets and other sources to indoor PM levels. In order to measure these effects, real-time continuous monitoring was conducted in an occupied home. In addition, a series of experiments were conducted to measure personal PM concentrations.
Methods. Four MIE Personal Data RAM nephelometers (MIE, Bedford, MA) and two to four Climet 500-i optical counters (Climet Instruments, Redlands, CA) were used to measure real-time indoor and outdoor PM concentrations at a Maryland residence for approximately two months. Particle concentrations were measured every five minutes by the Climet monitor, and every minute by the A41E monitor. The Climet monitors also measured temperature and relative humidity. The monitors were placed side-by-side whenever possible during data collection to allow for instrument comparison. To study the personal cloud, an MIE monitor was worn during home office work activities indoors.
Eight experiments were conducted to determine if clothes affect the magnitude of the personal cloud. In order to measure the differences between different levels of clothing, the experiments were conducted with the subject wearing either a bathing suit or light summer clothes.
Results. Median outdoor particle concentrations were 75 particles/cm3 compared to median indoor concentrations of 36 particles/cm 3 for particles ranging in size from 0.3 pm to 0.5 pm. Median outdoor particle concentrations for particles ranging in size from 5 -10 um were lower than median indoor levels. However, the mean indoor concentration of particles more than 10 um. was approximately twice the outdoor values.
Outdoor particle concentrations of 0.3 - 0.5 ~im particles had the highest correlation (Spearman r = 0.46, N = 25,280, p < 0.0001) with indoor concentrations in the living room. For particles > 5 fin, the outdoor concentrations were not adequate predictors of indoor concentrations.
Average personal PM concentrations at both levels of clothing were approximately 70% higher than concurrent stationary concentrations in the same room (p < 0.0001). A 6.2 p.g/m3 difference was detected between wearing summer clothes and a bathing suit for the personal PM concentrations (p <0.0014).
Average particle concentrations for particles in the 5 - 10 pm, and > 10 pan categories were calculated in three situations: when two Dalmatian dogs and two people were sleeping, when the dogs were alone in the house during the day, and when people and dogs were alone in the house during the day. The dog activities increased the levels of coarse particles (>5 pm) in the kitchen by 409%, living room by 48%, and outside near the monitor by 128%.
Conclusions. The average outdoor particle concentrations of 0.3 - 0.5 pm particles significantly exceeded average indoor concentrations. The observed increase in personal particle concentrations re-affirms the presence of the personal cloud. Furthermore, the PM difference observed between wearing light summer clothes and a bathing suit indicates that wearing clothes significantly increases the magnitude of the personal cloud. The presence of dogs significantly elevated PM levels (5 - 10 um, and > 10 um size ranges).
This work has been funded wholly or in part by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.