title: Hydrogen sulfide and particle matter levels associated with increased dispensing of anti-asthma drugs in Iceland's capital.
abstract: BACKGROUND
  Air pollutants in Iceland's capital area include hydrogen sulfide (H2S) emissions from geothermal power plants, particle pollution (PM10) and traffic-related pollutants. Respiratory health effects of exposure to PM and traffic pollutants are well documented, yet this is one of the first studies to investigate short-term health effects of ambient H2S exposure.
  
  
  OBJECTIVE
  The aim of this study was to investigate the associations between daily ambient levels of H2S, PM10, nitrogen dioxide (NO2) and ozone (O3), and the use of drugs for obstructive pulmonary diseases in adults in Iceland's capital area.
  
  
  METHODS
  The study period was 8 March 2006 to 31 December 2009. We used log-linear Poisson generalized additive regression models with cubic splines to estimate relative risks of individually dispensed drugs by air pollution levels. A three-day moving average of the exposure variables gave the best fit to the data. Final models included significant covariates adjusting for climate and influenza epidemics, as well as time-dependent variables.
  
  
  RESULTS
  The three-day moving average of H2S and PM10 levels were positively associated with the number of individuals who were dispensed drugs at lag 3-5, corresponding to a 2.0% (95% confidence interval [CI] 0.4, 3.6) and 0.9% (95% CI 0.1, 1.8) per 10 μg/m3 pollutant concentration increase, respectively.
  
  
  CONCLUSIONS
  Our findings indicated that intermittent increases in levels of particle matter from traffic and natural sources and ambient H2S levels were weakly associated with increased dispensing of drugs for obstructive pulmonary disease in Iceland's capital area. These weak associations could be confounded by unevaluated variables hence further studies are needed.
authors.affiliation: Centre of Public Health Sciences, School of Health Sciences, University of Iceland, Stapi v/Hringbraut, 101 Reykjavik, Iceland. hkc1@hi.is
authors.forename: Hanne Krage
authors.initials: HK
authors.lastname: Carlsen
authors.forename: Helga
authors.initials: H
authors.lastname: Zoëga
authors.forename: Unnur
authors.initials: U
authors.lastname: Valdimarsdóttir
authors.forename: Thórarinn
authors.initials: T
authors.lastname: Gíslason
authors.forename: Birgir
authors.initials: B
authors.lastname: Hrafnkelsson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use*; D001249:Asthma / Q000139:chemically induced* / Q000188:drug therapy; D004363:Drug Utilization / Q000706:statistics & numerical data; D006801:Humans; D006862:Hydrogen Sulfide / Q000032:analysis / Q000633:toxicity*; D007055:Iceland; D019570:Inhalation Exposure / Q000009:adverse effects* / Q000032:analysis; D008173:Lung Diseases, Obstructive / Q000139:chemically induced* / Q000188:drug therapy; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity; D010126:Ozone / Q000032:analysis / Q000633:toxicity; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D016012:Poisson Distribution; D012042:Registries; D012044:Regression Analysis; D012306:Risk; D012621:Seasons; D014505:Urban Population; D014887:Weather
chemical_list: D000393:Air Pollutants; D018927:Anti-Asthmatic Agents; D052638:Particulate Matter; D010126:Ozone; D009585:Nitrogen Dioxide; D006862:Hydrogen Sulfide