Headline: Asthma and COPD exacerbation in relation to outdoor air pollution in the metropolitan area of Berlin, Germany

Background: Ambient air pollution poses a major risk for the development and aggravation of respiratory diseases. Evidence suggests that even in low-level air pollution environments there is a risk for an increase in adverse respiratory symptoms. We examined whether variations in daily air pollution levels of nitrogen dioxide, ozone, or particulate matter in Berlin, Germany were associated with hospital admissions of chronic obstructive pulmonary disease (COPD) and asthma patients in a time series analysis. Methods: We calculated single and multi-pollutant models, investigated possible lags in effect, and analysed the influence of meteorological variables on the results. Data from January 2005 through December 2015 were used to quantify the concentration–response. Results: The risk ratio for asthma patients to be hospitalised on the same day of NO2 exposure was 1.101 per 10 µg/m3 NO2 increase (95% CI: 1.013 to 1.195), for COPD patients 1.123 (95% CI: 1.081 to 1.168). Neither the exposure to ozone (95% CI: 0.904 to 1.020), PM10 (95% CI: 0.990 to 1.127), nor PM2.5 (95% CI: 0.981 to 1.148) was associated with an increased risk ratio for asthma patients to be hospitalised. Risk ratios for the hospital admission of COPD patients were also not increased due to ozone (95% CI: 0.981 to 1.033), PM10 (95% CI: 0.988 to 1.032), or PM2.5 (95% CI: 0.966 to 1.019) exposure. The presented risk ratios and confidence intervals relate to the day of exposure. We found no increased hospitalisation risks with a delayed occurrence on subsequent days. Conclusions: A quantifiable, statistically significant increase in risk for asthma and COPD exacerbations owing to NO2 exposure at levels well below European regulatory limit values was observed.