Daily asthma severity in relation to personal ozone exposure and outdoor fungal spores

Epidemiologic investigations of ambient ozone (O-3) effects on daily asthma status have not used personal O-3 exposures and have often lacked well-characterized allergen exposures. To address this, we studied 12 asthmatic subjects aged 9 to 16 yr, who recorded daily asthma symptoms (functional levels 0 to 5) and as-needed inhaler use during September and October 1993 in San Diego, California. Outdoor aeroallergens, O-3, and fine particle concentrations were measured at a central outdoor site, and personal 12-h daytime exposures to O-3 were measured daily. Personal O-3 differed greatly between subjects and was 27% of mean outdoor O-3. In random-effects autoregression models controlling for weekend days and fungal spores, personal O-3 was associated with asthma severity: for a 90th percentile increase in O-3 (25 ppb), symptom scores increased by 25% (95% Cl: 0 to 49%) and inhaler use increased by 26% (95% Cl: 3 to 48%) over their averages. Outdoor 12-h O-3, but not l-h maximum O-3, was associated with inhaler use (p < 0.03). Fungal spores were significantly associated with symptoms (scores increased by 0.1 to 0.3/1,000 spores/m(3)) and inhaler use (0.1 to 0.4 puffs/1,000 spores/m(3)) across speciated groups. Pollen and fine particles (low levels) were not associated with any outcomes. These findings illustrate that the epidemiologic importance of O-3 and allergenic cofactors can be underestimated by failure to account for personal O-3 and fungal exposures.