Research Projects

Project at a Glance

Project Status: complete

Title: Characterization of the composition of personal, indoor, and outdoor particulate exposures.

Principal Investigator / Author(s): Suh, Helen

Contractor: Harvard School of Public Health

Contract Number: 98-330


Research Program Area: Health & Exposure

Topic Areas: Indoor Air Quality, Toxic Air Contaminants


Abstract:

A study entitled “Characterization of the Composition of Personal, Indoor, and Outdoor Particulate Exposures” was conducted to characterize the chemical composition of personal, indoor, and outdoor fine particulate (PM2.5) exposures for individuals with chronic obstructive pulmonary disease (COPD) living in the Los Angeles, CA region. This study was conducted in conjunction with a study funded by the U.S. Environmental Protection Agency (EPA). In the first study phase, mini-speciation samplers to measure fine particle nitrate (NO3 - ) and EC were validated in field experiments, which showed that both mini-samplers performed well. These mini-samplers were subsequently used with our multi-pollutant sampler to characterize fine particulate exposures for 22 individuals with COPD. For each individual, 24-hr personal, indoor and outdoor PM10, PM2.5, and fine particle NO3 - , elemental carbon (EC) and elemental concentrations were measured. [O3, SO2, and NO2 were measured as well as part of our companion EPA study as were PM10 and PM2.5.] Measurements were made for each individual over seven days during either or both summer of 1999 and winter of 2000. Personal, indoor, and outdoor PM2.5, NO3 - and EC concentrations varied by season, with the exception of outdoor NO3 - concentrations for which no seasonal difference was observed. Personal PM2.5 exposures were higher than corresponding indoor and outdoor concentrations in both seasons. In contrast, outdoor NO3 - and EC concentrations were in general higher than indoor and personal levels in both seasons, which may be due to the fact that motor vehicles are their major source and the high reactivity of NO3 - , which may result in losses of NO3 - indoors. Indoor concentrations for all three particulate measures were more strongly associated with personal exposures as compared to outdoor concentrations, which may be attributed to the facts that individuals spent most of their time indoors at home. Correlations among personal, indoor, and outdoor concentrations, however, generally varied by season and by particulate measure. In addition, the individual-specific correlations and longitudinal relationships were consistent with those observed in other studies conducted in Western U.S. and Canada. For PM2.5 and EC, for example, the effective penetration efficiency and the indoor source contribution varied by season, with a greater effective penetration efficiency in the summer and a greater indoor pollutant source contribution in the winter. The average contribution of NO3 - and EC to PM2.5 varied by season and by sample type. For personal, indoor, and outdoor samples, both NO3 - and EC comprised a relatively small proportion of the overall PM2.5 mass, demonstrating the need to measure concentrations of other particle components to account for more of the PM2.5 mass. Analysis of the PM2.5 filters showed limited ability of ICP-MS to detect elemental concentrations at the low sampling flow volumes used in our study. Of the detectable elements (Al, B, Ba, Cr, Mn, Ni, Pb, Zn), personal, indoor, and outdoor concentrations varied seasonally. Except for Al, significant and positive correlations between personal exposures and corresponding indoor and outdoor concentrations were observed in both seasons. Of the elements, Ba and Ni displayed the strongest associations between personal exposures and indoor and outdoor concentrations, and Al the weakest associations. The magnitude and strength of the associations generally differed by element and also differed from those observed for PM2.5. Despite this, significant positive correlations between mass and elemental concentrations were found, with associations strongest in both seasons for indoor and outdoor samples as compared to personal samples.


 

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