title: Autonomic effects of controlled fine particulate exposure in young healthy adults: effect modification by ozone.
abstract: BACKGROUND
  Human controlled-exposure studies have assessed the impact of ambient fine particulate matter on cardiac autonomic function measured by heart rate variability (HRV), but whether these effects are modified by concomitant ozone exposure remains unknown.
  
  
  OBJECTIVE
  In this study we assessed the impact of O(3) and particulate matter exposure on HRV in humans.
  
  
  METHODS
  In a crossover design, 50 subjects (19-48 years of age) were randomized to 2-hr controlled exposures to filtered air (FA), concentrated ambient particles (CAPs), O(3), or combined CAPs and ozone (CAPs + O(3)). The primary end point was change in HRV between the start and end of exposure. Secondary analyses included blood pressure (BP) responses, and effect modification by asthmatic status.
  
  
  RESULTS
  Achieved mean CAPs and O(3) exposure concentrations were 121.6 +/- 48.0 microg/m(3) and 113.9 +/- 6.6 ppb, respectively. In a categorical analysis, exposure had no consistent effect on HRV indices. However, the dose-response relationship between CAPs mass concentration and HRV indices seemed to vary depending on the presence of O(3). This heterogeneity was statistically significant for the low-frequency component of HRV (p = 0.02) and approached significance for the high-frequency component and time-domain measures of HRV. Exposure to CAPs + O(3) increased diastolic BP by 2.0 mmHg (SE, 1.2; p = 0.02). No other statistically significant changes in BP were observed. Asthmatic status did not modify these effects.
  
  
  CONCLUSIONS
  The potentiation by O(3) of CAPs effects on diastolic BP and possibly HRV is of small magnitude in young adults. Further studies are needed to assess potential effects in more vulnerable populations.
authors: Cardiovascular Epidemiology Research Unit, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
authors: Asghar A
authors: AA
authors: Fakhri
authors: Ljubomir M
authors: LM
authors: Ilic
authors: Gregory A
authors: GA
authors: Wellenius
authors: Bruce
authors: B
authors: Urch
authors: Frances
authors: F
authors: Silverman
authors: Diane R
authors: DR
authors: Gold
authors: Murray A
authors: MA
authors: Mittleman
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000633:toxicity*; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D019570:Inhalation Exposure; D008297:Male; D008875:Middle Aged; D010126:Ozone / Q000633:toxicity*; D052638:Particulate Matter / Q000633:toxicity*; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone