Great meeting last week! It was nice to hear about all the exciting work in
this area going on around the country. A couple hours after our meeting
ended, a colleague sent me this article discussing the health risks of
people cycling on busy streets -- a topic brought up by someone during the
Exhaust-ing ride for cyclists: Air pollutants trigger heart riskIn 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.
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.
"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."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.
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
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
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
"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
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
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
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.
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.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.
"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
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
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
"Our recommendations to cyclists would be to avoid busy as streets as much
as possible," said Dimitri Stanich, a spokesman for California's Air
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
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.
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."Little things like that can help a lot to reduce
exposure to cyclists," Bae said.
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."
San Francisco County Transportation Authority
In addition to our Subcommittee call for papers (posted online at
http://pressamp.trb.org/CallForPapers/CFPDetail.asp?cid=1348), there is
another TRB call for papers on the latest research or studies on the
seriousness and impacts of sleep loss, fatigue, or operator lack of
attention on transportation safety. Please visit this website to learn
Also, thank you to everyone who participated in our inaugural meeting
yesterday. We will be sure to share the minutes and any other materials
with you in the coming days. And please be sure to visit our website:
Eloisa Raynault, Subcommittee Co-Chair
Greetings friends of the TRB Health and Transportation Subcommittee,
This is a friendly reminder to join us on Monday, July 11, 2011 from
2:00-3:45 PM (EST) for our first meeting as a subcommittee.
We will meet in Boston, MA at the Seaport Hotel (Liberty Room) as a part
of TRB's Summer Meeting.
For those unable to attend in person, call 1-866-528-2256, and use pass
code 3829104. You may also link to our online web room to view the
slides (enter as a guest): HTTP://FHWA.ADOBECONNECT.COM/CERT/
The meeting slides and the meeting agenda are posted online at:
We look forward to your participation!