Objective: Ambient air pollution is a serious public health problem in Poland - e.g. PM_2.5 levels are the highest in the EU. Numerous studies have shown that both particulate and gaseous pollutants increase airway inflammation, which may lead to an exacerbation of COPD. The aim of the study was to define the association between exposure to selected air pollutants and the risk of COPD exacerbations.

Materials and Methods: We used a case-crossover approach to analyze data on COPD hospital admissions in 3 largest urban agglomerations in Poland: Warsaw, Cracow and the Tricity in 2011-2018. A distributed lag nonlinear models were used to analyze the risk of hospital admission due to COPD exacerbation during 21 days following the exposure to PM₁₀, PM_2.5, NO₂, and SO₂.

Results: In total 26,948 admissions due to COPD exacerbations were identified. During 21 days after exposure the rate ratio (95% CI) for admissions per 10 µg/m³ was 1.028 (1.008-1.049) for PM₁₀, 1.030 (1.006-1.055) for PM_2.5, 1.032 (0.988-1.0780) for NO₂ and 1.145 (1.038-1.262) for SO₂. The risk for admission peaked at 10 days after exposure to both PM fractions, whereas for NO₂ and SO₂ it was the highest on the day of exposure. The proportions (95% CI) of hospitalizations attributable to air pollution were 9.08% (3.10%-15.08%) for PM₁₀, 7.61% (1.27%-13.49%) for PM_2.5, 9.77% (-3.63%-21.48%) for NO₂ and 7.70% (2.30%-12.84%) for SO₂.

Conclusions: Exposure to PM, NO₂, and SO₂ was associated with an increased risk hospital admission due to COPD exacerbation. The risk patterns for particulate and gaseous pollutants were different. Due to the COPD burden, air quality in Poland requires urgent improvement.