http://www.environmentalhealthnews.org/ehs/news/exhaust-ing-ride-for-cyclists
Exhaust-ing ride for cyclists: Air pollutants trigger heart risk
In big cities around the world, cyclists
breathe an array of pollutants from exhaust-spewing cars. A new study
has now found a link between cycling on high traffic roads and heart
risks. Even healthy cyclists had harmful changes in their heart rates.
Experts say cyclists should stick to their two-wheels, however,
pointing to simple solutions to reduce exposure.
Illustration Omitted:
Unrelenting traffic
leaves a wake of gritty exhaust for cyclists to breathe. Enrique
Lobo/flickr
By Brett Israel
Environmental Health News
July 6, 2011
NEW YORK - Even by this city's standards, the Garment District is an
imposing place to ride a bike.
A never-ending parade of delivery trucks rumbles along 8th Avenue
between 34th and 42nd streets, leaving a wake of gritty exhaust for
cyclists to feel, smell and breathe.
After riding in the Garment District, Robert "Rocket" Ruiz,
a 13-year veteran of the bike messenger business, would often look
into the bathroom mirror and see his face covered in grime.
"I remember having to wash my face three or four times a day,"
said Ruiz, now the head dispatcher for Quik Trak Messenger Service.
"There's nothing but tar and smoke on your face." Ruiz, a
star on the Travel Channel's bike messenger show "Triple Rush,"
said he once had to miss a day of work to see a doctor because of
exhaust burning his eyes.
Pedaling behind pollutant-spewing cars and trucks may not seem as
scary as being hit by one, but scientists say it can pose invisible
dangers.
Now, for the first time, cycling in heavy traffic has been linked to a
heart health risk, Canadian researchers reported last month. A new
study found cyclists in Ottawa, Ontario, had heart irregularities in
the hours after their exposure to a variety of air pollutants on busy
roads.
Pedaling behind pollutant-spewing cars and trucks may not seem as
scary as being hit by one, but scientists say it can pose invisible
dangers."Our findings suggest that short-term exposure to traffic
may have a significant impact on cardiac autonomic function in healthy
adults," the scientists from Health Canada, Environment Canada
and the University of Ottawa wrote in the journal Environmental Health
Perspectives.
The study does not suggest that bikers would be better off driving,
experts say. Rather, the findings intensify the scrutiny on cyclists'
pollution exposure, and point to simple solutions for a cleaner ride,
such as avoiding busy roads like 8th Avenue whenever possible.
"It's something that actually concerns a lot of people that do
cycle," said Michael Brauer, a cyclist and atmospheric scientist
at the University of British Columbia who was not involved in the new
study. "People want to understand their risk. They're just
thinking all the time, 'Is this good for me? Is this bad for me? I'm
doing my part, but there's this car that's throwing this exhaust in my
face.' "
For the study, 42 healthy, non-smoking
cyclists wore heart monitors before, during and after cycling for one
hour on high- and low-traffic roads between May and September last
year. Instruments on the bikes' panniers measured exposure to air
pollution.
Illustration Omitted:
Study results point to simple solutions for a cleaner ride,
such as avoiding busy roads whenever possible.
Short-term exposure to heavy traffic significantly decreased heart
rate variability in the cyclists for up to three hours after they
finished cycling. Experts say reduced heart rate variability is
associated with a higher risk of heart attacks.
"A very healthy person is like a Ferrari," said Arden Pope,
an expert in the health effects of air pollution and professor at
Brigham Young University in Provo, Utah. "Step on the gas and it
really goes fast. Step on the brakes and it really slows down. The
human heart, you want it to be like that too."
But with lower heart rate variability, the heart is behaving more like
a minivan than a Ferrari, Pope said, meaning that it is less able to
respond to stress.
Researchers are not sure how air pollution alters heart rate
variability, Pope said. One idea is that particles in the lungs cause
inflammation, which throws off the body's ability to carry out its
automatic functions.
No respiratory effects were found in the cyclists. The researchers did
not find any significant changes in their lung function, probably
because all the cyclists were healthy, and most had no asthma or other
respiratory problems.
Around the world, researchers have found that whenever fine particles
increase in the air, deaths and hospitalizations from asthma, heart
attacks and other cardiopulmonary problems increase, too.
Hours to weeks of exposure to particles that are smaller than 2.5
micrometers in diameter, which peak during rush hours, can trigger
cardiovascular effects, according to the American Heart
Association.
Researchers are not sure how air pollution alters heart rate
variability. One idea is that particles in the lungs cause
inflammation, which throws off the body's ability to carry out its
automatic functions.For the Canadian cyclists, when their exposure to
certain pollutants, including ultrafine particles, nitrogen dioxide or
ozone, increased, their heart rate variability decreased, according to
the study.
Sheer proximity to tailpipes is one reason why cyclists have a high
exposure to the tiny particle pollutants, which are emitted by
vehicles along with thousands of other chemicals. Diesel buses and
trucks are among the worst offenders.
"The closer you are to the source of the fresh exhaust, the worse
it is," said Patrick Ryan, an environmental epidemiologist at the
University of Cincinnati, who studies the health effects of
traffic-related pollution.
Near the tailpipe, these particles are small enough to lodge deep in
the lungs, triggering heart attacks and hospitalizations from lung
diseases such as asthma. Tiny particles can also cross the blood-brain
barrier, potentially harming the nervous system. Farther away from the
tailpipe, these particles clump together, growing too large to lodge
deeply, Ryan said.
That's why even a small separation from cars, created by physical
barriers to traffic - something that's missing for most of 8th
Avenue - is important for cyclists.
Two white stripes of paint, with a few feet of cycling space between
them, is all that is reserved for bikers on this crowded street.
Trucks commonly idle on the bike lane. Heavy traffic creates a wind
tunnel that traps pollution on the road, according to a study by the
California Air Resources Board.
A 2010 study of cyclists in the Netherlands showed that hard-pedaling,
deep-breathing cyclists on busy roads inhale more of this dirty air.
In many cases, they also spend more time exposed to it compared to
someone driving the same distance.
"Those things add up and they give
cyclists that cycle in traffic a high exposure," Brauer
said.
Illustration Omitted:
Cyclists brave not only traffic, but rain and oil-slicked
roads in Portland, Ore.
But whether that exposure ups a cyclist's risk for heart or breathing
problems has been less well established. One small study of
Netherlands cyclists found a weak link between exposure to ultrafine
particles and soot and airway inflammation.
The new study of Canadian cyclists does not mean that people should
lock up their bikes and hop back into the driver's seat, said Brauer.
Another study has shown that drivers have higher respiratory problems
than cyclists because of their higher exposure to volatile organic
chemicals in vehicle exhaust.
"In stop-and-go traffic, [drivers] have more exposure than a
cyclist who stays 15 feet or more from the tailpipes," said
Rebecca Serna, executive director of the Atlanta Bicycle Coalition, a
cycling advocacy group.
The health benefits of cycling far outweigh the risks from air
pollution and traffic collisions relative to car driving, according to
one estimate by researchers in the Netherlands, where cycling is king.
Taking cars off the road also helps reduce greenhouse gas emissions
and traffic accidents.
"In general, you're better off cycling than not," Brauer
said. "The physical activity benefits outweigh negative impacts.
But you'd like there to be no impacts."
Exposure to dirty air adds to the perception problem that cycling is
unsafe, said C.H. Christine Bae, an urban planner at the University of
Washington in Seattle, who specializes in how bike facilities affect
air pollution exposure.
The Canadian study authors have a simple solution. Avoid busy
streets.
"In general, you're better off cycling than not. The physical
activity benefits outweigh negative impacts. But you'd like there to
be no impacts." - Michael Brauer, cyclist and atmospheric
scientist, University of British Columbia"When possible it may be
prudent to select cycling routes that reduce exposure to traffic
and/or to avoid cycling outdoors or exercise indoors on days with
elevated air pollution levels," the research team wrote.
Others agree.
"Our recommendations to cyclists would be to avoid busy as
streets as much as possible," said Dimitri Stanich, a spokesman
for California's Air Resources Board.
Of course, cyclists might want to avoid busy streets for a number of
reasons - fewer distracted drivers being one. But the busiest
streets also have the dirtiest air, with ultrafine particle and soot
exposure highest on busy roads, according to a recent study.
Bike routes should aim to minimize time spent on these high-traffic
roads, the Canadian researchers wrote. This would reduce exposures of
riders who may be more susceptible to the immediate health risks of
traffic-related air pollution, such as the elderly, children, and
pregnant mothers.
A study of bike lanes in Portland, Ore., showed that lanes separated
by planters, not just by white paint, actually decreased cyclists' air
pollution exposure. A Belgian study of traffic pollution found that
cycling as little as several feet off the road gave measurable
differences in exposure.
Getting cyclists out from behind the cars
helps, too. In Portland, when traffic stops at a red light, cyclists
have a designated area at the front of the line of cars, called a
bicycle box, which helps them navigate turns and flee the tailpipe
fumes.
Illustration Omitted:
Solutions like this bicycle box in Portland help cyclists flee
tailpipe fumes.
"Little things like that can help a lot to reduce exposure to
cyclists," Bae said.
If a little is good, more is better. Brauer says the preliminary
results of his lab's work suggest that bike lanes are best when built
one block from a major traffic artery. Despite the emerging research,
Bae said that she does not know of any cities that consider cyclists'
pollution exposure when designing bike lanes.
Including Vancouver, where Brauer cycles, many of the cities that
built bike lanes one block away from a major road thought about cost,
not pollution.
"Most were done by accident, because they were cheaper,"
Brauer said. "But they actually give you an air pollution
benefit."
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