Evidence of the role of interactions between air pollution and pollen exposure in subjects with allergic asthma is limited and need further exploration to promote adequate preventive measures. The objective of this study was to assess effects of exposure to ambient air pollution and birch pollen on exacerbation of respiratory symptoms in subjects with asthma and allergy to birch. Thirty-seven subjects from two Swedish cities (Gothenburg and Umeå) with large variation in exposure to both birch-pollen and air pollutants, participated in the study. All subjects had confirmed allergy to birch and self-reported physician-diagnosed asthma. The subjects recorded respiratory symptoms such as rhinitis or eye irritation, dry cough, dyspnoea, the use of any asthma or allergy medication and peak respiratory flow (PEF), daily for five consecutive weeks during two separate pollen seasons and a control season without pollen. Nitrogen oxides (NOx), ozone (O3), particulate matter (PM2.5), birch pollen counts, and meteorological data were obtained from an urban background monitoring stations in the study city centres. The data were analysed using linear mixed effects models. During pollen seasons all symptoms and medication use were higher, and PEF was reduced in the subjects. In regression analysis, exposure to pollen at lags 0 to 2 days, and lags 0 to 6 days was associated with increased ORs of symptoms and decreased RRs for PEF. Pollen and air pollution interacted in some cases; during low pollen exposure, there were no associations between air pollution and symptoms, but during high pollen exposure, O3 concentrations were associated with increased OR of rhinitis or eye irritation, and PM2.5 concentrations were associated with increased ORs of rhinitis or eye irritation, dyspnea and increased use of allergy medication. Pollen and air pollutants interacted to increase the effect of air pollution on respiratory symptoms in allergic asthma. Implementing the results from this study, advisories for individuals with allergic asthma could be improved, minimizing the morbidities associated with the condition.

中文翻译：

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桦树花粉、空气污染及其对花粉季节过敏性哮喘患者气道症状和呼气峰值流量的交互影响——瑞典北部和南部的一项小组研究

空气污染和花粉暴露在过敏性哮喘患者中相互作用的证据有限，需要进一步探索以促进适当的预防措施。本研究的目的是评估暴露于环境空气污染和桦树花粉对哮喘和对桦树过敏的受试者呼吸道症状恶化的影响。来自瑞典两个城市（哥德堡和于默奥）的 37 名受试者参与了这项研究，这些城市对桦树花粉和空气污染物的暴露程度差异很大。所有受试者均已确认对桦木过敏并自报医生诊断为哮喘。受试者记录了呼吸道症状，例如鼻炎或眼睛刺激、干咳、呼吸困难、使用任何哮喘或过敏药物和呼吸流量峰值 (PEF)，在两个单独的花粉季节和一个没有花粉的对照季节，每天连续五周。氮氧化物 (NOx)、臭氧 (O3)、颗粒物 (PM2.5)、桦树花粉计数和气象数据来自研究中心的城市背景监测站。使用线性混合效应模型分析数据。在花粉季节，所有症状和药物使用量都较高，受试者的 PEF 降低。在回归分析中，延迟 0 到 2 天和延迟 0 到 6 天的花粉暴露与 PEF 的症状 OR 增加和 RR 降低有关。在某些情况下，花粉和空气污染相互作用；在低花粉暴露期间，空气污染与症状之间没有关联，但在高花粉暴露期间，O3 浓度与鼻炎或眼睛刺激的 OR 增加有关，PM2.5 浓度与鼻炎或眼睛刺激的 OR 增加、呼吸困难和过敏药物的使用增加有关。花粉和空气污染物相互作用增加了空气污染对过敏性哮喘呼吸道症状的影响。实施这项研究的结果，可以改善对过敏性哮喘患者的建议，最大限度地减少与该病症相关的发病率。