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Recent research suggests that cyclists inhale more air pollutants
than motorists in traffic, mainly due to faster, deeper breathin
- this suggests that town planners should carefully consider
cycle routes.
Promoting commuting by bicycle instead of by car would reduce
traffic pollution, improve physical health and provide a healthier
environment with better air quality. However, there is evidence
to suggest that particulate emissions from fossil-fuel powered
vehicles and traffic are more toxic than a general mixture
of pollutants. Commuters experience short periods of high
exposure to exhaust emissions and are, therefore, potentially
at greater risk of health problems from traffic pollution.
Three main factors affect exposure of cyclists to air pollution
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- Faster and deeper breathing, which increases the total
amount of air inhaled
- Increased amounts of particulate matter reaching the lungs
during exercise - and
- Potentially longer times to complete a trip, compared
with travelling by car.
In this study, researchers in Belgium compared the exposure
to traffic emissions for cyclists and car passengers. Fifty-five
healthy, non-smoking participants were driven by car along
a test route with the windows closed, air conditioning off
and fan mode set at '1'. Air in the breathing zone (about
30cm from the mouth) was sampled for each trip to measure
PM concentrations. Each person then cycled the same route
immediately afterwards.
Three test routes were selected in different regions of Belgium
- one in Brussels, one in Louvain-la-Neuve - a new town -
and one in Mol, a small rural town. During each trip, the
breathing frequency, depth, oxygen uptake and heart rate were
measured. These measurements were used to calculate the volume
of air breathed in and out per minute, the amount of PM inhaled
and the estimated amount of PM that would be deposited in
the lungs for each participant.
Compared with more stable concentrations inside cars, particle
number concentrations (PNCs) fluctuated more for cyclists
in traffic, reaching peaks of 100,000 particles per cubic
centimetre. PNC values were about three times higher in Brussels
than the other two sites.
Cyclists breathed more frequently and took more deep breaths
than car passengers. They breathed in and out about 4.3 times
more air per minute than car passengers. In addition, cyclists
inhaled 400 to 900 per cent more emission particles than car
passengers on the same route. The fraction of particles that
remain deposited in the lungs after being inhaled was significantly
higher for cyclists than car passengers.
These results suggest that transport planners should take
the physical effort of cyclists into account and aim to reduce
exposure to traffic emissions in addition to considering emission
concentrations. Cycle routes should be designed to increase
the distance between vehicle tail pipes and cyclists.
Cyclists should be aware that, while some studies suggest
short bursts of exposure to PM could potentially contribute
to cardiovascular health problems, the evidence for this is
not as strong as the evidence that regular physical activity,
such as cycling, helps prevent chronic conditions (including
cardiovascular disease) and reduces the risk of premature
death.
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