title: Chronic ambient hydrogen sulfide exposure and cognitive function.
abstract: BACKGROUND
  Exposures to hydrogen sulfide gas (H2S) have been inconclusively linked to a variety of negative cognitive outcomes. We investigated possible effects on cognitive function in an urban population with chronic, low-level exposure to H2S.
  
  
  METHODS
  Participants were 1637 adults, aged 18-65 years from Rotorua city, New Zealand, exposed to ambient H2S from geothermal sources. Exposures at homes and workplaces were estimated from data collected by summer and winter H2S monitoring networks across Rotorua in 2010/11. Metrics for H2S exposure at the time of participation and for exposure over the last 30 years were calculated. H2S exposure was modeled both as continuous variables and as quartiles of exposure covering the range of 0-64 ppb (0-88 μg/m(3)). Outcomes were neuropsychological tests measuring visual and verbal episodic memory, attention, fine motor skills, psychomotor speed and mood. Associations between cognition and measures of H2S exposure were investigated with multiple regression, while covarying demographics and factors known to be associated with cognitive performance.
  
  
  RESULTS
  The consistent finding was of no association between H2S exposure and cognition. Quartiles of H2S exposure had a small association with simple reaction time: higher exposures were associated with faster response times. Similarly, for digit symbol, higher H2S exposures tended to be marginally associated with better performance.
  
  
  CONCLUSIONS
  The results provide evidence that chronic H2S exposure, at the ambient levels found in and around Rotorua, is not associated with impairment of cognitive function.
authors.affiliation: Department of Neurology, University of California, Davis, CA, USA; Alzheimer's Disease Center, Veterans Administration Northern California Health Care System, Martinez, CA, USA.
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Reed
authors.affiliation: School of Medicine and Health Sciences, University of Otago, Wellington, New Zealand.
authors.forename: Julian
authors.initials: J
authors.lastname: Crane
authors.affiliation: Faculty of Health, Auckland University of Technology, New Zealand.
authors.forename: Nick
authors.initials: N
authors.lastname: Garrett
authors.affiliation: Department of Neurology, University of California, Davis, CA, USA; Human Cognitive Neurophysiology Laboratory, Veterans' Administration Northern California Health Care System, Martinez, CA, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Woods
authors.affiliation: School of Public Health, University of California, Berkeley, CA, USA. Electronic address: m_bates@berkeley.edu.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Bates
mesh_terms: D000293:Adolescent; D000328:Adult; D000339:Affect / Q000187:drug effects; D000368:Aged; D000393:Air Pollutants / Q000633:toxicity*; D001288:Attention / Q000187:drug effects; D003071:Cognition / Q000187:drug effects*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D006862:Hydrogen Sulfide / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D008568:Memory / Q000187:drug effects; D008875:Middle Aged; D009048:Motor Skills / Q000187:drug effects; D009483:Neuropsychological Tests; D009520:New Zealand; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D014505:Urban Population; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D006862:Hydrogen Sulfide
keywords: Cognitive function; Cross-sectional study; Geothermal; Hydrogen sulfide; Neuropsychological tests; New Zealand