RESUMEN
BACKGROUND: Air pollution is a severe problem in Poland, with Kraków area being among the regions with the worse air quality. Viral croup or pseudocroup is a common childhood disease that may manifest with severe upper respiratory tract obstruction. Our aim was to evaluate the associations between incidence and severity of viral croup symptoms among children living in Kraków area, Poland, and air pollution. METHODS: The retrospective cross-sectional study included Kraków area residents <18 years of age admitted to the Emergency Department of St. Louis Children Hospital in Kraków, Poland over 2-year period. Daily mean concentrations of air pollutants: particulate matter (PM10 and PM2.5), nitric oxides (NOx), carbon oxide (CO), sulfur dioxide, ozone, and benzene were retrieved from public database of measurements performed at three local stations. Numbers of cases of viral croup per week were correlated with weekly mean concentrations of air pollutants. Mean air temperature was treated as a cofactor. RESULTS: During the studied period, mean concentrations of PM10, PM2.5, and NOx exceeded the allowable levels (yearly means) specified by Polish law regulations. Significant positive correlations of moderate strength were observed between weekly mean concentrations of most air pollutants, especially PM10, PM2.5, CO and benzene, and numbers of cases of viral croup recorded per week, confirmed in the analysis restricted to non-holiday period and to winter months only. The correlations between NOx, CO, benzene and croup prevalence were independent of temperature in non-holiday period. CONCLUSIONS: Our results support adverse impact of air pollution on children's respiratory health.