Traffic air pollution and hospital admission for asthma: a case–control approach in a Turin (Italy) population

Objectives: This study investigated the relationship between traffic air pollution and asthma, using a case–control design applied to routinely collected data. Methods: Subjects resident in Turin during the period 1997–1999 and admitted for asthma were defined as cases; patients admitted for causes other than respiratory diseases or heart diseases were defined as controls. Nitrogen dioxide and total suspended particulate were considered as indicators of traffic air pollution. Statistical analysis were performed, separately for young (0–14 years), adult (15–64 years) and elderly (>64 years) patients, with a logistic regression model; results are expressed as percentage of risk modification for a 10 g/m3 increase in exposure to pollutants. Results: The risk of emergency admissions for asthma rose significantly with increased exposure to nitrogen dioxide [2.4%, 95% Confidence Interval: 0.5%; 4.3%], and total suspended particulate [2.3%, 95% Confidence Interval: 1.1%–3.6%]. The significant association was evident, in particular, among young and elderly patients for both pollutants. Conclusion: Using a case–control design both easy to use and manage, the study confirms the significant association between hospital emergency admissions for asthma and exposure to nitrogen dioxide and total suspended particulate pollutants.