A Comparison of Time-Activity Pattern in Four Cities and the Implication of Environmental Exposures. Lee-Jane Sally Liu, Dept. of Environmental Health Sciences, University of South Carolina, Columbia, SC 29208; and Ralph Delfino, Epidemiology Division, Dept of Medicine, University of California, Irvine, and Graduate School of Public Health, San Diego State University, 6505 Alvarado Rd, Suite 110, San Diego, CA 92120
It is known that time-activity (T/A) pattern affects the levels of individual environmental exposures. However, few studies investigated the impact of differences in T/A patterns on individuals’ integrated environmental exposures. Previous large-scale T/A studies have involved in examining the variation of T/A patterns reported over a short period (one to three days), which does not allow for examining of seasonal variation and within subject variability. This paper examines T/A patterns reported by diverse volunteers in four cities and different seasons from previous and ongoing exposure assessment studies. These volunteers included young students (aged 10 to 22), adult workers, retirees, and housewives. Subjects reported T/A for up to 5 weeks. Since environmental exposures (O3 and/or NO2 and/or aerosol acidity) were monitored in most of the studies, the impact of the T/A patterns on exposure levels can be estimated. A total of 204 subjects participated in these studies, conducted in State College, PA (in the summer of 1991), Toronto, Ontario (winter and summer 1992), Alpine, CA (summer, fall 1994 and 1995), and Rock Hill, SC (spring 1995). Subjects reported T/A for periods of 5 days (summer Toronto and State College), 2 weeks (Rock Hill), 3 weeks (winter Toronto), and 5 weeks (Alpine), respectively. This paper compares the usefulness of the information obtained by different diary formats; examines variation of T/A (time outdoors, in transit, at work outdoors or indoors, indoors at home, and indoor at other places) within and among individuals in different geographic regions; investigates factors that may affect T/A pattern, including age, gender, education, day-of-week, season, and income; and estimates the impact of the differences in T/A patterns on actual environmental exposures of individuals.