Effects of urban ozone pollution on hospitalizations for exacerbation of chronic obstructive pulmonary disease

Abstract

Background: There are epidemiological data of adverse outcomes for COPD from urban ozone and related photochemical oxidants, but their relationship may be complex. The aim of this study was to investigate the associations between O3 and NO2 and daily COPD hospitalizations, adjusting for acute respiratory infections, weather and seasonality. Methods: Daily hospitalizations for COPD were regressed on pollutants and potential confounding variables using an autoregressive Poisson model. The relative risks of COPD hospitalization were calculated for the 25th to 75th percentile and 95th to 99th percentile increase in each of the selected pollutant concentrations. Results: The risk for COPD hospitalizations was significant both for 25th to 75th percentile and 95th to 99th percentile increase in concentrations of NO2 (RR=1.09; 95% CI: 1.02, 1,17 and RR=1,12; 95% CI: 1.03, 1.22, respectively) and O3 (RR=1.19; 95% CI: 1.05, 1.35 and RR=1.09; 95% CI: 1.03, 1,17). At the lower percentile change in ambient levels, the risk for ozone paradoxically increased whereas for NO2 decreased. A comparison among the standardized regression coefficients indicates that the most important risk for COPD hospitalizations was associated with ozone. Conclusion: The current results indicate the most important risk for COPD exacerbations to be associated with ozone supporting reduction in ambient ozone levels. However, in urban area the improvement in health outcomes for ozone cannot be completely achieved by reducing NO emissions although benefit may be expected in suburban areas.