title: Exposure error masks the relationship between traffic-related air pollution and heart rate variability.
abstract: OBJECTIVE
  We examined whether more precise exposure measures would better detect associations between traffic-related pollution, elemental carbon (EC), nitrogen dioxide (NO2), and heart rate variability (HRV).
  
  
  METHODS
  Repeated 24-hour personal and ambient PM2.5, EC, and NO2 were measured for 30 people living in Atlanta, GA. The association between HRV and either ambient concentrations or personal exposures was examined using linear mixed effects models.
  
  
  RESULTS
  Ambient PM2.5, EC, NO2, and personal PM2.5 were not associated with HRV. Personal EC and NO2 measured 24 hours before HRV were associated with decreased RMSSD, PNN50, and HF and with increased LF/HF. RMSSD decreased by 10.97% (95% confidence interval: -18.00 to -3.34) for an inter-quartile range change in personal EC (0.81 microg/m3).
  
  
  CONCLUSIONS
  Results indicate decreased vagal tone in response to traffic pollutants, which can best be detected with precise personal exposure measures.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA 02215, USA. hsuh@hsph.harvard.edu
authors.forename: Helen H
authors.initials: HH
authors.lastname: Suh
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis*; D002244:Carbon / Q000009:adverse effects / Q000032:analysis; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis*; D005260:Female; D005845:Georgia; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000139:chemically induced / Q000503:physiopathology; D009585:Nitrogen Dioxide / Q000009:adverse effects / Q000032:analysis; D010126:Ozone / Q000009:adverse effects / Q000032:analysis; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D013431:Sulfates / Q000009:adverse effects / Q000032:analysis; D014630:Vagus Nerve / Q000187:drug effects* / Q000503:physiopathology; D001335:Vehicle Emissions / Q000032:analysis* / Q000633:toxicity
chemical_list: D052638:Particulate Matter; D013431:Sulfates; D001335:Vehicle Emissions; D010126:Ozone; D002244:Carbon; D009585:Nitrogen Dioxide