 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.imagesfigure 1figure 2figure 3figure 4figure 5 
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