The effect of secondary inorganic aerosols, soot and the geographical origin of air mass on acute myocardial infarction hospitalisations in Gothenburg, Sweden during 1985–2010: a case-crossover study

BACKGROUND: The relative importance of different sources of air pollution for cardiovascular disease is unclear. The aims were to compare the associations between acute myocardial infarction (AMI) hospitalisations in Gothenburg, Sweden and 1) the long-range transported (LRT) particle fraction, 2) the remaining particle fraction, 3) geographical air mass origin, and 4) influence of local dispersion during 1985–2010. METHODS: A case-crossover design was applied using lag0 (the exposure the same day as hospitalisation), lag1 (exposure one day prior hospitalisation) and 2-day cumulative average exposure (CA2) (mean of lag0 and lag1). The LRT fractions included PM(ion) (sum of sulphate, nitrate and ammonium) and soot measured at a rural site. The difference between urban PM(10) (particulate matter with an aerodynamic diameter smaller than 10 μm) and rural PM(ion) was a proxy for locally generated PM(10) (PM(rest)). The daily geographical origin of air mass was estimated as well as days with limited or effective local dispersion. The entire year was considered, as well as warm and cold periods, and different time periods. RESULTS: In total 28 215 AMI hospitalisations occurred during 26 years. PM(10), PM(ion), PM(rest) and soot did not influence AMI for the entire year. In the cold period, the association was somewhat stronger for PM(rest) than for urban PM(10;) the strongest associations were observed during 1990–2000 between AMI and CA2 of PM(rest) (6.6% per inter-quartile range (IQR), 95% confidence interval 2.1 to 11.4%) and PM(10) (4.1%, 95% CI 0.2% − 8.2%). Regarding the geographical air mass origins there were few associations. Days with limited local dispersion showed an association with AMI in the cold period of 2001–2010 (6.7%, 95% CI 0.0% − 13.0%). CONCLUSIONS: In the cold period, locally generated PM and days with limited local dispersion affected AMI hospitalisations, indicating importance of local emissions from e.g. traffic.