Air pollutants enhance rhinoconjunctivitis symptoms in pollen-allergic individuals

Background: Little is know about the relation of airborne pollen allergens to nasal and ocular symptoms in combination with air pollutants. Objective: The hypothesis was that air pollutants exacerbate allergic sympt oms of the nose and eyes during the pollen season. In addition, the use of allergen measurements instead of pollen counts should be tested. Methods: Fifteen pollen-allergic, nonsmoking subjects with weak reactivity of the airways recorded rhinoconjunctival symptoms and medication every mor ning and evening throughout the pollen season. Symptoms were compared with air pollutants (nitrogen oxide [NOx], particulate matter smaller than 10 mu m, and ozone) and birch and grass pollen counts or, alternatively, to airbo rne birch and grass allergens determined using ELISA-techniques. A multiple linear regression model was used which controlled for autocorrelation of t he residuals of the time series (Cochrane-Orcutt approach). This model was applied to each subject individually, followed by calculations of summary s cores for the group. Results: Air pollution levels were moderate, often meeting air quality stan dards. Effect estimates (increase of score with 10-fold increase of concent ration) were NOx = 1.06, P < 0.01; ozone = 1.59, P < 0.01; and pollen = 0.4 8, P < 0.001. Using allergen concentrations instead of pollen counts result ed in similar effect estimates. Using particulate matter smaller than 10 <m u>m instead of NOx gave comparable but less consistent results. Conclusions: Symptoms were related to moderate levels of pollutants, sugges ting that rhinoconjunctival tissue is very sensitive to irritant stimuli du ring an ongoing allergic inflammation, and that susceptibility toward aller gens might be increased in areas with increased levels of air pollutants. A llergen measurements seem equally usable as pollen counts to investigate rh inoconjunctivitis.