The Harvard Southern California Chronic Ozone Exposure Study: assessing ozone exposure of grade-school-age children in two Southern California communities.

The Harvard Southern California Chronic Ozone Exposure Study measured personal exposure to, and indoor and outdoor ozone concentrations of, approximately 200 elementary school children 6-12 years of age for 12 months (June 1995-May 1996). We selected two Southern California communities, Upland and several towns located in the San Bernardino mountains, because certain characteristics of those communities were believed to affect personal exposures. On 6 consecutive days during each study month, participant homes were monitored for indoor and outdoor ozone concentrations, and participating children wore a small passive ozone sampler to measure personal exposure. During each sampling period, the children recorded time-location-activity information in a diary. Ambient ozone concentration data were obtained from air quality monitoring stations in the study areas. We present ozone concentration data for the ozone season (June-September 1995 and May 1996) and the nonozone season (October 1995-April 1996). During the ozone season, outdoor and indoor concentrations and personal exposure averaged 48.2, 11.8, and 18.8 ppb in Upland and 60.1, 21.4, and 25.4 ppb in the mountain towns, respectively. During the nonozone season, outdoor and indoor concentrations and personal exposure averaged 21.1, 3.2, and 6.2 ppb in Upland, and 35.7, 2.8, and 5.7 ppb in the mountain towns, respectively. Personal exposure differed by community and sex, but not by age group.

Initial field evaluation of the Harvard active ozone sampler for personal ozone monitoring.

Assessing personal exposure to ozone has only been feasible recently with the introduction of passive ozone samplers. These devices are easy to use, but changes in air velocity across their collection surfaces can affect performance. The Harvard active ozone sampler (AS) was developed in response to problems with the passive methods. This active sampler has been tested extensively as a microenvironmental sampler. To test for personal sampling, 40 children attending summer day-camp in Riverside, California wore the active ozone sampler for approximately 2.6 h on July 19 and 21, 1994, when ozone concentrations were about 100 ppb and 140 ppb, respectively. The children spent 94-100% of the sampling period outside, staying within a well-defined area while participating in normal camp activities. Ambient ozone concentrations across this area were monitored by two UV photometric ozone monitors. The active sampler was worn in a small backpack that was also equipped with a passive ozone sampler. Device precision, reported as the percent difference between duplicate pairs of samplers, was +/- 3.7% and +/- 4.2% for the active and passive samplers, respectively. The active sampler measured, on average, 94.5 +/- 8.2% of the ambient ozone while the passive samplers measured, on average, 124.5 +/- 18.8%. The samplers were worn successfully for the entire sampling period by all participating children.