Subclinical responses in healthy cyclists briefly exposed to traffic-related air pollution: an intervention study

Environ Health. 2010 Oct 25:9:64. doi: 10.1186/1476-069X-9-64.


Background: Numerous epidemiological studies have demonstrated adverse health effects of a sedentary life style, on the one hand, and of acute and chronic exposure to traffic-related air pollution, on the other. Because physical exercise augments the amount of inhaled pollutants, it is not clear whether cycling to work in a polluted urban environment should be encouraged or not. To address this conundrum we investigated if a bicycle journey along a busy commuting road would induce changes in biomarkers of pulmonary and systematic inflammation in a group of healthy subjects.

Methods: 38 volunteers (mean age: 43 ± 8.6 years, 26% women) cycled for about 20 minutes in real traffic near a major bypass road (road test; mean UFP exposure: 28,867 particles per cm3) in Antwerp and in a laboratory with filtered air (clean room; mean UFP exposure: 496 particles per cm3). The exercise intensity (heart rate) and duration of cycling were similar for each volunteer in both experiments. Exhaled nitric oxide (NO), plasma interleukin-6 (IL-6), platelet function, Clara cell protein in serum and blood cell counts were measured before and 30 minutes after exercise.

Results: Percentage of blood neutrophils increased significantly more (p = 0.004) after exercise in the road test (3.9%; 95% CI: 1.5 to 6.2%; p = 0.003) than after exercise in the clean room (0.2%; 95% CI: -1.8 to 2.2%, p = 0.83). The pre/post-cycling changes in exhaled NO, plasma IL-6, platelet function, serum levels of Clara cell protein and number of total blood leukocytes did not differ significantly between the two scenarios.

Conclusions: Traffic-related exposure to particles during exercise caused a small increase in the distribution of inflammatory blood cells in healthy subjects. The health significance of this isolated change is unclear.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Air Pollutants / analysis
  • Air Pollutants / poisoning*
  • Belgium
  • Bicycling / physiology*
  • Bicycling / statistics & numerical data
  • Blood Cell Count
  • Blood Platelets / drug effects
  • Blood Platelets / physiology
  • Exhalation / drug effects
  • Female
  • Humans
  • Inflammation / chemically induced
  • Inhalation Exposure / adverse effects*
  • Inhalation Exposure / analysis
  • Male
  • Middle Aged
  • Neutrophils / drug effects
  • Nitric Oxide / analysis
  • Particulate Matter / analysis
  • Particulate Matter / poisoning
  • Vehicle Emissions*


  • Air Pollutants
  • Particulate Matter
  • Vehicle Emissions
  • Nitric Oxide