Abstract
An ozone exposure assessment study was conducted in a Southern California community. The Harvard ozone passive sampler was used to monitor cohorts of 22 and 18 subjects for 8 weeks during the spring and fall of 1994, respectively. Ozone exposure variables included 12-hr personal O3 measurements, stationary outdoor O3 measurements from a continuous UV photometer and from 12-hr Harvard active monitors, and time-activity information. Results showed that personal O3 exposure levels averaged one-fourth of outdoor stationary O3 levels, attributable to high percentages of time spent indoors. Personal O3 levels were not predicted well by outdoor measurements. A random-effect general linear model analysis indicated that variance in personal exposure measurements was largely accounted for by random error (59-82%), followed by inter-subject (9-18%) and between-day (9-23%) random effects. The microenvironmental model performs differently by season, with the regression model for spring cohorts exhibiting two times the R2 of the fall cohorts (R2 = 0.21 vs. 0.09). When distance from the stationary monitoring site, elevation, and traffic are taken into account in the microenvironmental models, the adjusted R2 increased almost twofold for the fall personal exposure data. The low predictive power is due primarily to the apparent spatial variation of outdoor O3 and errors in O3 measurements and in time-activity records (particularly in recording the use of air conditioning). This study highlights the magnitude of O3 exposure misclassification in epidemiological settings and proposes an approach to reduce exposure uncertainties in assessing air pollution health effects.
Highlights
Standard (NAAQS) for ozone (03), 0.12 ppm, is based on the health effects due to acute exposures of 1 hr as measured by continuous monitors
Using the 12-hr personal measurements significantly reduces the magnitude of expected exposure misclassification in studies that have relied solely upon 03 measurements from outdoor stationary site monitors to represent personal exposure to 03
Deposition of 03 on clothes may result in a reduced personal measurements on the passive sampler [12], the analysis on time-activity pattern suggests that the low personal exposure is not an artifact but a manifestation of the low fraction of time spent outdoors
Summary
Standard (NAAQS) for ozone (03), 0.12 ppm, is based on the health effects due to acute exposures of 1 hr as measured by continuous monitors. Epidemiological research on the acute and adverse respiratory effects of 03, on the other hand, generally involves repeated daily measurements over several weeks or months in larger cohorts (panel studies). This study involved daytime (12-hr) personal 03 monitoring in cohorts of 23 and 18 subjects for two 8week periods during the spring and fall of 1994, respectively. The purpose of this study was to investigate personal 03 exposures among subjects during both spring and fall seasons in the Alpine area and to investigate the feasibility of using ambient 03 measurements from one outdoor fixed site as well as the activity patterns from the subjects to predict personal 03 exposures. The extent of the effects of outdoor 03 spatial variation on the predictive power of personal exposure models was investigated
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.