title: Exposure to air pollution near a steel plant is associated with reduced heart rate variability: a randomised crossover study.
abstract: Epidemiological studies have shown that as ambient air pollution (AP) increases the risk of cardiovascular mortality also increases. The mechanisms of this effect may be linked to alterations in autonomic nervous system function. We wished to examine the effects of industrial AP on heart rate variability (HRV), a measure of subtle changes in heart rate and rhythm representing autonomic input to the heart.
  
  
  
  Sixty healthy adults were randomized to spend five consecutive 8-h days outdoors in one of two locations: (1) adjacent to a steel plant in the Bayview neighbourhood in Sault Ste Marie Ontario or (2) at a College campus, several kilometers from the plant. Following a 9-16 day washout period, participants spent five consecutive days at the other site. Ambient AP levels and ambulatory electrocardiogram recordings were collected daily. HRV analysis was undertaken on a segment of the ambulatory ECG recording during a 15 min rest period, near the end of the 8-h on-site day. Standard HRV parameters from both time and frequency domains were measured. Ambient AP was measured with fixed site monitors at both sites. Statistical analysis was completed using mixed-effects models.
  
  
  
  Compared to the College site, HRV was statistically significantly reduced at the Bayview site by 13% (95%CI 3.6,19.2) for the standard deviation of normal to normal, 8% (95%CI 0.1, 4.9) for the percent normal to normal intervals differing by more than 50 ms, and 15% (95%CI 74.9, 571.2) for low frequency power. Levels of carbon monoxide, sulphur dioxide, nitrogen dioxide, and fine and ultrafine particulates were slightly, but statistically significantly, elevated at Bayview when compared to College. Interquartile range changes in individual air pollutants were significantly associated with reductions in HRV measured on the same day. The patterns of effect showed a high degree of consistency, with nearly all pollutants significantly inversely associated with at least one measure of HRV.
  
  
  
  The significant associations between AP and changes in HRV suggest that ambient AP near a steel plant may impact autonomic nervous system control of the heart.
authors.affiliation: Population Studies Division, Environmental Health Science Research Bureaum Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada. robin.shutt@hc-sc.gc.ca.
authors.forename: Robin H
authors.initials: RH
authors.lastname: Shutt
authors.affiliation: Population Studies Division, Environmental Health Science Research Bureaum Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Lisa Marie
authors.initials: LM
authors.lastname: Kauri
authors.affiliation: Air Health Sciences Division, Water and Air Quality Bureau, Health Canada, 269 Laurier Ave W, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Scott
authors.initials: S
authors.lastname: Weichenthal
authors.affiliation: Mechanistic Studies Division, Environmental Health Science Research Bureau, Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Premkumari
authors.initials: P
authors.lastname: Kumarathasan
authors.affiliation: Hazard Identification Division, Environmental Health Science Research Bureau, Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Renaud
authors.initials: R
authors.lastname: Vincent
authors.affiliation: Hazard Identification Division, Environmental Health Science Research Bureau, Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Errol M
authors.initials: EM
authors.lastname: Thomson
authors.affiliation: Population Studies Division, Environmental Health Science Research Bureaum Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.affiliation: Population Studies Division, Environmental Health Science Research Bureaum Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Mamun
authors.initials: M
authors.lastname: Mahmud
authors.affiliation: Population Studies Division, Environmental Health Science Research Bureaum Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Sabit
authors.initials: S
authors.lastname: Cakmak
authors.affiliation: Population Studies Division, Environmental Health Science Research Bureaum Health Canada, 50 Colombine Driveway, Ottawa, ON, K1A 0 K9, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Dales
mesh_terms: D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D002248:Carbon Monoxide / Q000009:adverse effects / Q000032:analysis; D004781:Environmental Exposure / Q000009:adverse effects; D004784:Environmental Monitoring; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D009589:Nitrogen Oxides / Q000032:analysis; D009864:Ontario; D010126:Ozone / Q000032:analysis; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D013232:Steel; D013458:Sulfur Dioxide / Q000009:adverse effects / Q000032:analysis; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D052638:Particulate Matter; D013458:Sulfur Dioxide; D013232:Steel; D010126:Ozone; D002248:Carbon Monoxide
keywords: Air pollution; Environment; Epidemiology; Heart rate variability; Industrial air pollution; Steel production