Long-Term Residence in Areas of High Ozone: Associations with Respiratory Health in a Nationwide Sample of Nonsmoking Young Adults

Abstract

Few studies have examined the respiratory effects of multiyear ozone exposures in human populations. We examined associations between current respiratory health status and long-term ozone exposure histories in 520 Yale College (New Haven, CT) students who never smoked. Questionnaires addressed current respiratory symptoms, respiratory disease history, residential history, and other factors. The symptoms of cough, phlegm, wheeze apart from colds, and a composite respiratory symptom index (RSI) were selected as outcome measures. Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV(1)), forced expiratory flow rate between 25 and 75% of FVC (FEF(25-75)), and forced expiratory flow rate at 75% of FVC (FEF(75)) were obtained by forced expiration into spirometers. Ozone exposure was treated as a dichotomous variable, where subjects were assigned to the high-exposure group if they lived for 4 or more years in a U.S. county with 10-year average summer-season daily 1-hr maximum ozone levels [greater/equal to] 80 ppb. Lung function and respiratory symptoms were analyzed by multiple linear and logistic regression on ozone exposure, controlling for covariates. Lung function was lower in the group with high ozone exposures: differences were statistically significant for FEV(1) [-3.1%; 95% confidence interval (CI), -0.2 to -5.9%] and FEF(25-75) (-8.1%; CI, -2.3 to -13.9%), and nearly so for FEF(75) (-6.7%; CI, 1.4 to -14.8). Gender-specific analyses revealed stronger associations for males than for females. The symptoms of chronic phlegm, wheeze apart from colds, and RSI were increased in the ozone-exposed group, with odds ratios of 1.79 (CI, 0.83-3.82), 1.97 (CI, 1.06-3.66), and 2.00 (CI, 1.15-3.46), respectively. We conclude that living for 4 or more years in regions of the country with high levels of ozone and related copollutants is associated with diminished lung function and more frequent reports of respiratory symptoms.