title: Hydrogen sulfide and traffic-related air pollutants in association with increased mortality: a case-crossover study in Reykjavik, Iceland.
abstract: OBJECTIVE
  To study the association between daily mortality and short-term increases in air pollutants, both traffic-related and the geothermal source-specific hydrogen sulfide (H₂S).
  
  
  METHODS
  Population-based, time stratified case-crossover. A lag time to 4 days was considered. Seasonal, gender and age stratification were calculated. Also, the best-fit lag when introducing H₂S >7 µg/m(3) was selected by the Akaike Information Criterion (AIC).
  
  
  METHODS
  The population of the greater Reykjavik area (n=181,558) during 2003-2009.
  
  
  METHODS
  Cases were defined as individuals living in the Reykjavik capital area, 18 years or older (N=138,657), who died due to all natural causes (ICD-10 codes A00-R99) other than injury, poisoning and certain other consequences of external causes, or cardiovascular disease (ICD-10 codes I00-I99) during the study period.
  
  
  METHODS
  Percentage increases in risk of death (IR%) following an interquartile range increase in pollutants.
  
  
  RESULTS
  The total number of deaths due to all natural causes was 7679 and due to cardiovascular diseases was 3033. The interquartile range increased concentrations of H₂S (2.6 µg/m(3)) were associated with daily all natural cause mortality in the Reykjavik capital area. The IR% was statistically significant during the summer season (lag 1: IR%=5.05, 95% CI 0.61 to 9.68; lag 2: IR%=5.09, 95% CI 0.44 to 9.97), among males (lag 0: IR%=2.26, 95% CI 0.23 to 4.44), and among the elderly (lag 0: IR%=1.94, 95% CI 0.12 to 1.04; lag 1: IR%=1.99, 95% CI 0.21 to 1.04), when adjusted for traffic-related pollutants and meteorological variables. The traffic-related pollutants were generally not associated with statistical significant IR%s.
  
  
  CONCLUSIONS
  The results suggest that ambient H₂S air pollution may increase mortality in Reykjavik, Iceland. To the best of our knowledge, ambient H₂S exposure has not previously been associated with increased mortality in population-based studies and therefore the results should be interpreted with caution. Further studies are warranted to confirm or refute whether H₂S exposure induces premature deaths.
authors: Centre of Public Health Sciences, University of Iceland, Reykjavik, Iceland.
authors: Ragnhildur Gudrun
authors: RG
authors: Finnbjornsdottir
authors: Occupational and Environmental Medicine, Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
authors: Anna
authors: http://orcid.org/0000-0002-9876-0627
authors: A
authors: Oudin
authors: Science Institute, University of Iceland, Reykjavik, Iceland.
authors: Bjarki Thor
authors: BT
authors: Elvarsson
authors: Faculty of Medicine, University of Iceland, Reykjavik, Iceland Department of Allergy and Respiratory Medicine and Sleep, Landspitali University Hospital, Reykjavik, Iceland.
authors: Thorarinn
authors: T
authors: Gislason
authors: Department of Preventive Medicine, University of Iceland, Reykjavik, Iceland.
authors: Vilhjalmur
authors: V
authors: Rafnsson
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000517:prevention & control / Q000706:statistics & numerical data*; D018592:Cross-Over Studies; D004781:Environmental Exposure / Q000009:adverse effects* / Q000706:statistics & numerical data; D006801:Humans; D006862:Hydrogen Sulfide / Q000009:adverse effects* / Q000032:analysis; D007055:Iceland / Q000453:epidemiology; D018986:Motor Vehicles / Q000706:statistics & numerical data*; D052638:Particulate Matter; D011159:Population Surveillance; D012140:Respiratory Tract Diseases / Q000209:etiology / Q000401:mortality* / Q000517:prevention & control; D018570:Risk Assessment
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D006862:Hydrogen Sulfide
keywords: Air pollution; Cross-over studies; Geothermal; Hydrogen Sulfide; Power Plants; Registries