Autonomic effects of controlled fine particulate exposure in young healthy adults: effect modification by ozone.
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.
Fakhri
Asghar A
AA
Cardiovascular Epidemiology Research Unit, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Ilic
Ljubomir M
LM
Wellenius
Gregory A
GA
Urch
Bruce
B
Silverman
Frances
F
Gold
Diane R
DR
Mittleman
Murray A
MA
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
D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone