The investigators examined the relative contributions of indoor and outdoor sources of particulate exposures by measuring personal, indoor, and outdoor exposures to PM2.5 and its major components nitrate (NO3-), elemental carbon (EC), and various elements. These exposures were measured for 22 people with chronic obstructive pulmonary disease living in metropolitan Los Angeles. For each participant, measurements were made over consecutive seven-day periods in either or both of Winter and Summer 2000, using personal mini-samplers and mini-samplers located inside and outside of their homes.
Consistent with previous studies, the relationships between personal exposures and indoor and outdoor concentrations were strong and varied by season. Personal PM2.5 exposures were higher than corresponding indoor and outdoor concentrations in both seasons. Indoor concentrations of 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. Outdoor NO3- and EC concentrations were higher in both seasons than indoor and personal levels, reflecting the fact that their major sources are located outdoors. 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. Concentrations of most elements, however, could not be determined due to the low sampling flow rates used in this study. Several factors, including season, location and activity patterns, were shown to affect exposures to PM2.5, NO3- and EC. Results demonstrate the importance of estimating the contributions of both indoor and outdoor sources to personal PM2.5 exposures, and the need to develop better low-flow rate sampling and analysis methods for elemental concentrations.
Helen H. Suh is an Assistant Professor of Environmental Chemistry and Exposure Assessment at the Harvard School of Public Health. Her research focuses on the characterization of air pollutant exposures and their relationship to cardiovascular health. Dr. Suh has been on the faculty at Harvard since 1997. She has served on review and advisory panels for numerous governmental and research agencies, including the U.S. Environmental Protection Agency, the Longitudinal Cohort Study of Environmental Effects on Child Health and Development, the Health Effects Institute, and the Massachusetts Bay Transportation Agency. Dr. Suh received the Yaglou Prize from the International Society of Indoor Air and served as a councilor for the International Society of Exposure Assessment. She received her S.B. from the Massachusetts Institute of Technology in Biology and her M.S. and Doctoral degrees from Harvard in Environmental Health Sciences.
Li-Te Chang is a Research Fellow at the Harvard School of Public Health. Dr. Chang's research focuses on the characterization and modeling of fine particulate concentrations. He received his doctoral degree in 2001.
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