The 1998 Baltimore Particulate Matter Epidemiology±Exposure Study: Part 2. Personal exposure assessment associated with an elderly study population RON WILLIAMS, a JACK SUGGS, a JOHN CREASON, b CHARLES RODES, c PHIL LAWLESS, c RICHARD KWOK, b R. ZWEIDINGER a AND LINDA SHELDON a a U.S. Environmental Protection Agency, National Exposure Research Laboratory, Research Triangle Park, North Carolina 27711 b U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina 27711 c Research Triangle Institute, Research Triangle Park, North Carolina 27709 An integrated epidemiological±exposure panel study was conducted during the summer of 1998 which focused upon establishing relationships between potential human exposures to particulate matter (PM) and related co-pollutants with detectable health effects. The study design incorporated repeated individual 24-h integrated PM 2.5 personal exposure monitoring. A total of 325 PM 2.5 personal exposure samples were obtained during a 28-day study period using a subject pool of 21 elderly (65+ years of age) residents of an 18-story retirement facility near Baltimore, Maryland. Each sample represented a unique 24-h breathing zone measurement of PM 2.5 mass concentration. PM 2.5 and PM 10 mass concentrations collected from the apartments of the subjects as well as residential and ambient sites were compared to individual and mean PM 2.5 personal exposures. Daily PM 2.5 personal exposure concentrations ranged from 2.4 to 47.8 g/m 3 with an overall individual study mean of 12.9 g/m 3 . Mean PM 2.5 personal exposures were determined to be highly correlated to those representing the central indoor ( r =0.90) and ambient sites ( r =0.89). Subjects reported spending an average of 92% of each day within the confines of the retirement center. Based upon measured and modeled exposures, a mean PM 2.5 personal cloud of 3.1 g/m 3 was estimated. Data collected from these participants may be unique with respect to the general elderly population due to the communal lifestyle within the facility and reported low frequency of exposure to sources of PM. Journal of Exposure Analysis and Environmental Epidemiology (2000) 10, 533±543. Keywords: activity profile, elderly population, exposure assessment, particulate matter, personal exposures. Introduction The elderly have been described as representing a popula- tion that may be susceptible to particulate matter (PM) and related co-pollutants and have been targeted for study based upon their reported health effect risk factors (U.S. Environmental Protection Agency, 1996, 1998). In a report on national PM research priorities, the National Research Council (National Research Council Ð National Academy of Science, 1998) indicated that reducing uncertainty in exposure assessments for potentially susceptible popula- tions should be one of the U.S. Environmental Protection Agency (U.S. EPA)'s highest priorities. Reducing these uncertainties can be addressed by developing a better understanding of the frequency, duration, magnitude, and variability of the elderly's PM exposures for particle size fractions of biological significance and understanding the extent to which the elderly are exposed to PM originating from ambient sources. Little is known about the relation- ships between the elderly's daily activities and the individual and longitudinal variability of their PM expo- sures. Klepeis et al. (1996) reported in a national U.S. human activity survey that persons 65+ years of age spend more than 80% of their time indoors with limited exposures to some typical PM sources such as automotive emissions. Williams et al. (in press) observed an even higher percentage of time spent indoors for an elderly study population of 26 individuals. Results from a limited 1997 U.S. EPA pilot study conducted near Baltimore during January±February (1997 Baltimore Particulate Matter Epidemiology±Exposure Study of the Elderly) indicated that elderly subjects could be successfully enrolled and retained in a PM monitoring study using active personal monitors and detailed activity logs (Williams et al., in press). This same study also indicated that individual exposure to fine PM could vary widely between subjects living within a common residence but that fluctuations in the ambient PM concentrations still 1. Abbreviations: LPM, liters per minute; PEM, personal exposure monitor; PM, particulate matter; U.S. EPA, U.S. Environmental Protection Agency. 2. Address all correspondence to: Ron Williams, MD, U.S. Environmental Protection Agency, National Exposure Research Laboratory, MD-56, Research Triangle Park, NC 27711. Tel.: +1-919-541-2957. E-mail: williams.ronald@epa.gov Accepted 9 June 2000. Journal of Exposure Analysis and Environmental Epidemiology (2000) 10, 533±543 # 2000 Nature America, Inc. All rights reserved 1053-4245/00/$15.00 www.nature.com/jea