http://www.timesonline.co.uk/tol/news/environment/article7140213.ece
May 30, 2010
Toxic cities mock 'healthy' cycle riding
Jonathan Leake, Environment Editor
Illustration Omitted:
Young
Woman Riding Bicycle to Work. Cyclists inhale five times as many
toxic particles as car passengers, research found
CYCLING to work may seem the healthy option, but a study has shown
that people riding in cities inhale tens of millions of toxic
nanoparticles with every breath, at least five times more than drivers
or pedestrians.
The research involved fitting cyclists with devices that could count
the particles, mostly emitted by car exhausts, in the air they were
breathing.
It showed that urban concentrations of nanoparticles, which measure
just a few millionths of a millimetre, could reach several hundred
thousand in a cubic centimetre of air.
The particles, when inhaled, have been linked to heart disease and
respiratory problems.
Because they are exerting themselves, cyclists breathe harder and
faster than other road users. The study found that they suck in about
1,000 cubic cm with each breath, meaning they may inhale tens of
millions of the particles each time they fill their lungs, and
billions during a whole journey.
"This is the first time anyone has counted the particles while also
measuring people's breathing during city commuting. It showed that
cyclists can inhale an astonishing number of pollutant particles in
one journey," said Luc Int Panis of the transport research institute
at Hasselt University in Belgium, who led the study.
For the research, just published in the journal Atmospheric
Environment, Int Panis and his colleagues asked cyclists to pedal
while wearing a mask fitted with instruments that could measure and
count the particulates, as such particles are known. All are invisible
even in severely polluted air.
The researchers found that in Brussels the cyclists inhaled 5.58m
nanoparticles for every metre cycled, dropping to about 1.1m when they
tried the experiment in Mol, a much smaller town in Belgium.
They also found the cyclists inhaled four to five times more particles
than a car passenger driven along the same route.
Int Panis said: "The air pollution figures in a big city like London
or Birmingham are the same as or greater than in Brussels so British
city cyclists will experience similar effects."
For cyclists and other road users, the key question is what the health
impact might be of inhaling so many particles.
This has been one of the hardest questions to answer because the time
lag between exposure to pollutants and developing an illness is
usually long.
Earlier researchers had the same difficulty when studying whether
smoking was linked to lung cancer, and it took decades to confirm the
connection.
New techniques for gathering and analysing data mean, however, that
the health problems caused by particulates are emerging much more
quickly.
A study carried out in London, to be published soon in the journal
Epidemiology, is expected to show that exposures to high
concentrations of nanoparticles are associated with a higher risk of
heart disease. It will also show an association between larger
particulates and respiratory health.
Other studies have shown that exposure to particulate pollution can
have rapid short-term effects too - such as provoking asthma
attacks.
In a 2007 study, published in the New England Journal of Medicine,
researchers at Imperial College London asked 60 people with mild or
moderate asthma to walk along the western end of the busy Oxford
Street in central London, where only diesel-powered taxis and buses,
plus cyclists, are permitted. The volunteers suffered asthma symptoms
such as reduced breathing capacity and lung inflammation.
Diesel vehicles emit far higher levels of pollutant nanoparticles than
petrol engines.
What alarms health researchers is that such particles are so small
that they penetrate the lungs and circulate in the blood. They are
then thought to accumulate in organs such as the heart and brain and
cause inflammatory reactions.
Wearing a mask offers little protection as the particles are so small
that they pass straight through any shield.
Earlier this year, such fears prompted the House of Commons
environmental audit select committee to publish a report warning that
air pollution caused about 50,000 premature deaths a year in
Britain.
Int Panis's research has already annoyed cycling groups. He has
decided not to attend Velo-city 2010, a conference on cycling to be
held in Copenhagen next month, because of the hostility he faced when
announcing preliminary results of his research.
Int Panis and his colleagues point out that cycling still brings many
health benefits and hope that it may be healthier than driving a
car.
Int Panis said: "I am a cyclist and the idea that riding a bike
might be less healthy than driving is not pleasant, but I am also a
scientist, so I have to look at the data."
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