In the report, the authors review data on the methodological background and results from the 1987-88 California Air Resources Board (CARB) time activity study and from a similar 1985 national study of Americans' Use of Time conducted at the University of Maryland, College Park. In order to facilitate comparisons, data from the study were recorded to be as compared as possible to the CARB code categories. In general, the data on average distributions of time in activities matched up rather well across the two samples. Despite some differences, the two data sets overall showed remarkably similar patterns of activity. That was less true for the locations codes, however. Several sources of discrepancy were found in the comparison of these data. A recording of location data from the national study provided some resolution of the differences that were found, but several differences remained. The strong similarities of the average time for the activity data indicate that the California data could be used to generate a better set of location codings for the national data. A major reason for analyzing time-diary data is to estimate time spent in various microenvironments. Microenvironments refer neither solely to activities nor solely to locations but to the combination of activities and locations that yield potential exposures of which 16 were defined for comparison. The analysis confirms Californians spent more time in transit and in outdoor environments.

On cover: Project report. "February 1991." "EPA 600-4-91-006." Cover title. "Project officer, Joseph V. Behar." "Contract no. 68-01-7325, delivery order 12." Includes bibliographical references.