Environmental exposure to air pollution and allergens and peak flow changes

Laboratory-based studies have shown that ozone and nitrogen dioxide can pot entiate the effect of allergen in sensitized asthmatic subjects, but it Is not known whether this interaction is important under natural exposure cond itions. Thirty-five subjects with clinical diagnoses of asthma or chronic obstructi ve pulmonary disease and with a provocative dose causing a 20% fall in forc ed expiratory volume In one second methacholine <12.25 mu mol (using the Ya n method) kept peak expiratory flow (PEF) records for a 4-week period durin g late summer, with concurrent measurement of spore and pollen counts and p ollution levels. Multiple regression analysis was then used to determine th e effect on PEP of aeroallergen, and of the interaction between aeroallerge n and pollutant levels. A statistically significant interaction was demonstrated between total spor e count and ozone, but not nitrogen dioxide. Mean PEF fell in association w ith increasing spore count (same-day and 24-h lag level) and PEF variabilit y increased with increasing spore count (24-h lag level only); both changes were greater the higher the prior ozone level, These results suggest that ozone can potentiate the effect of aeroallergens in subjects with bronchial hyperreactivity under natural exposure conditio ns. However, the effect was small, and the clinical significance of the int eraction requires further study.