title: Associations of ambient hydrogen sulfide exposure with self-reported asthma and asthma symptoms.
abstract: BACKGROUND
  Whether long-term, low-level hydrogen sulfide (H2S) gas is a cause of health effects, including asthma, is uncertain. Rotorua city, New Zealand, has the largest population exposed, from geothermal sources, to relatively high ambient levels of H2S. In a cross-sectional study, the authors investigated associations with asthma in this population.
  
  
  METHODS
  A total of 1637 adults, aged 18-65 years, were enrolled during 2008-2010. Residences and workplaces were geocoded. H2S exposures at homes and workplaces were estimated using city-wide networks of passive H2S samplers and kriging to create exposure surfaces. Exposure metrics were based on (1) time-weighted exposures at home and work; and (2) the maximum exposure (home or work). Exposure estimates were entered as quartiles into regression models, with covariate data.
  
  
  RESULTS
  Neither exposure metric showed evidence of increased asthma risk from H2S. However, some suggestion of exposure-related reduced risks for diagnosed asthma and asthma symptoms, particularly wheezing during the last 12 months, emerged. With the maximum exposure metric, the prevalence ratio for wheeze in the highest exposure quartile was 0.80 (0.65, 0.99) and, for current asthma treatment, 0.75 (0.52, 1.08). There was no evidence that this was caused by a "survivor effect".
  
  
  CONCLUSIONS
  The study provided no evidence that asthma risk increases with H2S exposure. Suggestions of a reduced risk in the higher exposure areas are consistent with recent evidence that H2S has signaling functions in the body, including induction of smooth muscle relaxation and reduction of inflammation. Study limitations, including possible confounding, preclude definitive conclusions.
authors: School of Public Health, University of California, Berkeley, CA 94720-7367, USA. m_bates@berkeley.edu
authors: Michael N
authors: MN
authors: Bates
authors: Nick
authors: N
authors: Garrett
authors: Julian
authors: J
authors: Crane
authors: John R
authors: JR
authors: Balmes
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006862:Hydrogen Sulfide / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D012135:Respiratory Sounds / Q000209:etiology; D055815:Young Adult
chemical_list: D006862:Hydrogen Sulfide