Ozone-induced respiratory symptoms: exposure-response models and association with lung function.

Ozone-induced respiratory symptoms are known to be functions of concentration, minute ventilation, and duration of exposure. The purposes of this study were to identify an exposure-response model for symptoms, to determine whether response was related to age, and to assess the relationships between symptom and lung function responses to ozone. Four hundred and eighty-five healthy male volunteers (ages 18-35 yrs) were exposed to one of six ozone concentrations at one of three activity levels for 2 h. Symptoms and forced expiratory volume in one second (FEV1) were assessed at the end of 1 and 2 h. The exposure and response data were fitted by a nonlinear exposure-response model previously found to describe FEV1 response. The proportion of individuals experiencing moderate or severe cough, shortness of breath, and pain on deep inspiration were accurately described as functions of concentration, minute ventilation, and time. Response was inversely related to age for shortness of breath (p=0.0001), pain on deep inspiration (p=0.0002), and cough (p=0.0013). Controlling for exposure differences, symptom responses were significantly but weakly (correlation coefficient 0.30-0.41) related to the FEV1 response. In conclusion, the exposure-response model did accurately predict symptoms, response was inversely related to age.