Air pollution and the aggravation of the symptoms of COPD in children

Studies conducted in Zagreb reported a short-term relation between air pollutant concentrations and emergency hospital visits due to the aggravation of symptoms of the chronic obstructive pulmonary disease (COPD). Air pollution in Zagreb is generally below the limit, and usually within the values recommended by the World Health Organization. Daily variations in the number of emergency room visits due to COPD were modeled in relation to daily variations in air pollution for the period 1995-1997. A generalized additive model for Poisson distribution was used, controlling for possible confounders, seasonality, trend, and autoregressive patterns. The effect of NO/sub 2/ was linear and significant with relative risk associated with a 50 /spl mu/gm/sup -3/ increase in NO/sub 2/ concentrations equal 1.297 (95% confidence limits 1.026-1.639). The effect of SO/sub 2/ was also linear, but not statistically significant, and that of black smoke was significantly nonlinear and of an intriguing U shape. The COPD emergency visits increased when black smoke concentrations decreased below 36 /spl mu/gm/sup -3/ (the 75th percentile) and increased above 48 /spl mu/gm/sup -3/ (the 90th percentile). This finding is attributed to possible confounding with ozone.