Exposure to ambient air pollutants and short-term risk for exacerbations of allergic rhinitis: A time-stratified, case-crossover study in the three largest urban agglomerations in Poland.

Allergic rhinitis (AR) affects 10 % of the world population, with an increased prevalence in regions with substantial air pollution, but the association between exposure to air pollutants and the short-term risk of AR exacerbations is unclear. We used a time-series approach to analyze the risk of hospital admissions due to AR over 8 days from exposure to various air pollutants. Distributed lag nonlinear models were used to analyze data gathered between 2012 and 2018 in the three largest urban agglomerations in Poland. The analyses were carried out separately for the warm (April - September) and cold seasons (October - March). Overall, there were 1407 admissions due to AR. In the warm season, the rate ratio (95 % confidence interval) for admission per 10 µg/m3 was 1.202 (1.044, 1.384) for particulate matter less than 10 µm (PM10); 1.094 (0.896, 1.335) for particulate matter less than 2.5 µm (PM2.5); 0.946 (0.826, 1.085) for nitrogen dioxide (NO); 0.837 (0.418, 1.677) for sulfur dioxide (SO); and 1.112 (1.011, 1.224) for ozone (O). In the cold season, the rate ratio for admission per 10 µg/m3 was 1.035 (0.985, 1.088) for PM10; 1.041 (0.977, 1.108) for PM2.5; 1.252 (1.122, 1.398) for NO; 0.921 (0.717, 1.181) for SO; and 1.030 (1.011, 1.050) for O. In conclusion, the risk of admission due to AR increased significantly after exposure to O in the warm and cold seasons. Exposure to PM10 was associated with a significantly increased risk of AR hospitalizations in the warm season only, whereas exposure to NO was associated with a significantly increased risk of AR admission in the cold season.