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 Researchers in London randomly assigned 119 men and women age 60 or
older to take two-hour walks along one of two distinct routes:
through a tranquil traffic-free expanse of Hyde Park, or along
Oxford Street, the city’s bustling shopping district that’s clogged
with diesel-powered buses and cabs.
The study team tested the air for contaminants during each walk, and
also assessed participants for lung capacity, or how easily people
could breathe, and arterial stiffness, which influences how hard the
heart works to pump blood through the body.
After walking in Hyde Park, healthy participants had better lung
capacity and decreased arterial stiffness, the study found. But when
these people walked along Oxford Street, they experienced only a
slight improvement in lung capacity and their arteries got stiffer.
“Just walking at a normal pace for a couple of hours benefits the
respiratory and cardiovascular system for up to 24 hours after the
walk,” said senior study author Kian Fan Chung of Imperial College
London.
“This in itself is a new finding, but the most interesting finding
is that being exposed during that time to environmental pollution
that one encounters on a busy roadside with a lot of traffic
virtually negates these benefits,” Chung said by email.
Exercise has long been linked to better cardiovascular health, and
the connection between air pollution exposure and a wide range of
health problems including asthma and other breathing issues is also
well established.
Black soot and fine particulate matter, as well as contaminants in
traffic fumes, can increase the risk of getting a variety of heart
and lung diseases and of dying from them.
Air pollution is responsible for around 5.5 million premature deaths
worldwide every year, researchers note in The Lancet. In the UK,
polluted air contributes to 40,000 deaths each year, nearly a
quarter of them in London.
The current study offers fresh evidence that short-term exposure to
pollution is associated with stiffening of the arteries and impaired
lung function, strengthening the case for reduced vehicle emissions
and more green space for exercise in cities, the researchers argue.
All of the participants in the study were non-smokers or had quit at
least one year earlier. While 40 of them were healthy, 39
participants had heart disease and 40 had a breathing disorder known
as chronic obstructive pulmonary disease (COPD).
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Participants were randomly assigned first to do a walk in Hyde Park
or on Oxford Street, then three to eight weeks later they were asked
to do the other walk.
The detrimental effects of walking near traffic were most pronounced
in people with COPD. These participants reported more symptoms like
cough, shortness of breath and breathing after the walk on Oxford
Street than in Hyde Park, and they also experienced increased
arterial stiffness.
For people with heart disease, however, medication mattered. Among
these participants, people only experienced increased stiffening of
the arteries on Oxford Street if they weren’t taking medication to
control their disease.
Based on air quality tests during each walk, it appeared that the
harmful effects of walking on Oxford Street were associated with
higher exposure to two byproducts of traffic exhaust: black carbon
soot and ultrafine particles in the air known as PM 2.5.
One limitation of the study is that it lacked a control group of
people who spent time on Oxford Street or in Hyde Park without
exercising, which makes it impossible to prove how much the physical
activity contributed to any changes in lung capacity or arterial
stiffness, the authors note.
Even so, the study adds to the evidence that the location of
exercise matter, said Dr. Dr. George Thurston, author of an
accompanying editorial and director of the Program in Human
Exposures and Health Effects at New York University School of
Medicine.
“Given that the elimination of fossil fuel burning will not happen
immediately, the public, and especially people who are most
susceptible should avoid exercising near roadways with heavy traffic
of diesel vehicles,” Thurston said by email.
SOURCES: http://bit.ly/2pcgYRR and http://bit.ly/2kAal6V The Lancet,
online December 5, 2017.
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