title: Short-term effects of carbon monoxide on mortality: an analysis within the APHEA project.
abstract: OBJECTIVE
  We investigated the short-term effects of carbon monoxide on total and cardiovascular mortality in 19 European cities participating in the APHEA-2 (Air Pollution and Health: A European Approach) project.
  
  
  METHODS
  We examined the association using hierarchical models implemented in two stages. In the first stage, data from each city were analyzed separately, whereas in the second stage the city-specific air pollution estimates were regressed on city-specific covariates to obtain overall estimates and to explore sources of possible heterogeneity. We evaluated the sensitivity of our results by applying different degrees of smoothing for seasonality control in the city-specific analysis.
  
  
  RESULTS
  We found significant associations of CO with total and cardiovascular mortality. A 1-mg/m(3) increase in the 2-day mean of CO levels was associated with a 1.20% [95% confidence interval (CI), 0.63-1.77%] increase in total deaths and a 1.25% (95% CI, 0.30-2.21%) increase in cardiovascular deaths. There was indication of confounding with black smoke and nitrogen dioxide, but the pollutant-adjusted effect of CO on mortality remained at least marginally statistically significant. The effect of CO on total and cardiovascular mortality was observed mainly in western and southern European cities and was larger when the standardized mortality rate was lower.
  
  
  CONCLUSIONS
  The results of this large study are consistent with an independent effect of CO on mortality. The heterogeneity found in the effect estimates among cities may be explained partly by specific city characteristics.
authors.affiliation: Department of Hygiene and Epidemiology, University of Athens Medical School, Athens, Greece. esamoli@med.uoa.gr
authors.forename: Evangelia
authors.initials: E
authors.lastname: Samoli
authors.forename: Giota
authors.initials: G
authors.lastname: Touloumi
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Hugh Ross
authors.initials: HR
authors.lastname: Anderson
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.forename: Bertil
authors.initials: B
authors.lastname: Forsberg
authors.forename: Maria Angela
authors.initials: MA
authors.lastname: Vigotti
authors.forename: Judith
authors.initials: J
authors.lastname: Vonk
authors.forename: Mitja
authors.initials: M
authors.lastname: Kosnik
authors.forename: Jiri
authors.initials: J
authors.lastname: Skorkovsky
authors.forename: Klea
authors.initials: K
authors.lastname: Katsouyanni
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D002248:Carbon Monoxide / Q000032:analysis / Q000633:toxicity*; D002318:Cardiovascular Diseases / Q000401:mortality*; D004784:Environmental Monitoring; D062665:Epidemiological Monitoring; D005060:Europe / Q000453:epidemiology; D006801:Humans; D009026:Mortality / Q000639:trends*; D013997:Time Factors; D014505:Urban Population / Q000706:statistics & numerical data
chemical_list: D000393:Air Pollutants; D002248:Carbon Monoxide