Traffic-related air pollution and acute changes in heart rate variability and respiratory function in urban cyclists

Environ Health Perspect. 2011 Oct;119(10):1373-8. doi: 10.1289/ehp.1003321. Epub 2011 Jun 14.


Background: Few studies have examined the acute health effects of air pollution exposures experienced while cycling in traffic.

Objectives: We conducted a crossover study to examine the relationship between traffic pollution and acute changes in heart rate variability. We also collected spirometry and exhaled nitric oxide measures.

Methods: Forty-two healthy adults cycled for 1 hr on high- and low-traffic routes as well as indoors. Health measures were collected before cycling and 1-4 hr after the start of cycling. Ultrafine particles (UFPs; ≤ 0.1 μm in aerodynamic diameter), particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5), black carbon, and volatile organic compounds were measured along each cycling route, and ambient nitrogen dioxide (NO2) and ozone (O3) levels were recorded from a fixed-site monitor. Mixed-effects models were used to estimate associations between air pollutants and changes in health outcome measures relative to precycling baseline values.

Results: An interquartile range increase in UFP levels (18,200/cm3) was associated with a significant decrease in high-frequency power 4 hr after the start of cycling [β = -224 msec2; 95% confidence interval (CI), -386 to -63 msec2]. Ambient NO2 levels were inversely associated with the standard deviation of normal-to-normal (NN) intervals (β = -10 msec; 95% CI, -20 to -0.34 msec) and positively associated with the ratio of low-frequency to high-frequency power (β = 1.4; 95% CI, 0.35 to 2.5) 2 hr after the start of cycling. We also observed significant inverse associations between ambient O3 levels and the root mean square of successive differences in adjacent NN intervals 3 hr after the start of cycling.

Conclusions: Short-term exposures to traffic pollution may contribute to altered autonomic modulation of the heart in the hours immediately after cycling.

Publication types

  • Clinical Trial

MeSH terms

  • Adult
  • Air Pollution / adverse effects*
  • Cross-Over Studies
  • Environmental Monitoring
  • Female
  • Forced Expiratory Volume / drug effects
  • Heart Rate / drug effects*
  • Humans
  • Male
  • Maximal Midexpiratory Flow Rate / drug effects
  • Middle Aged
  • Nitrogen Dioxide / toxicity
  • Ozone / toxicity
  • Particulate Matter / toxicity
  • Respiration / drug effects
  • Respiratory Function Tests
  • Vehicle Emissions / toxicity
  • Vital Capacity / drug effects
  • Young Adult


  • Particulate Matter
  • Vehicle Emissions
  • Ozone
  • Nitrogen Dioxide