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Risk rises within hours of exposure
Date: 2/13/2012
BIDMC Contact: Jerry Berger
Phone: 617-667-7308
Email: jberger@bidmc.harvard.edu
BOSTON – Air pollution, even at levels generally considered safe by federal regulations, increases the risk of stroke by 34 percent, Beth Israel Deaconess Medical Center researchers have found.
Writing in the Feb. 14, 2012 issue of the Archives of Internal Medicine, researchers who studied more than 1,700 stroke patients in the Boston area over a 10-year period found exposure to ambient fine particulate matter, generally from vehicle traffic, was associated with a significantly higher risk of ischemic strokes on days when the EPA’s air quality index for particulate matter was yellow instead of green.
Researchers focused on particles with a diameter of 2.5 millionths of a meter, referred to as PM2.5. These particles come from a variety of sources, including power plants, factories, trucks and automobiles and the burning of wood. They can travel deeply into the lungs and have been associated in other studies with increased numbers of hospital visits for cardiovascular diseases such as heart attacks.
“The link between increased stroke risk and these particulates can be observed within hours of exposure and are most strongly associated with pollution from local or transported traffic emissions,†says Murray A. Mittleman, MD, DrPH, the study’s senior author, a physician in the CardioVascular Institute at Beth Israel Deaconess Medical Center and an Associate Professor of Medicine at Harvard Medical School. “Any proposed changes in regulated pollution levels must consider the impact of lower levels on public health.â€
“Considering that almost everyone is exposed to air pollution and is at risk for stroke, that’s actually a pretty large effect,†adds Gregory Wellenius, ScD, the study’s lead author and an Assistant Professor of Community Health at Brown University.
Researchers analyzed the medical records of more than 1,700 patients who went to the hospital for treatment of confirmed strokes between 1999 and 2008. They matched the onset of stroke symptoms in each patient to hourly measurements of particulate air pollution taken at the nearby Harvard School of Public Health’s environmental monitoring station.
The team was able to estimate the hour the stroke symptoms first occurred, rather than relying on the more coarse measure of when patients were admitted to the hospital. They also included only strokes confirmed by attending neurologists, rather than relying on more vague insurance billing codes.
Meanwhile, Harvard’s hourly measurements of pollution within 13 miles of 90 percent of the stroke patients’ homes allowed for close matching in time of exposure and stroke onset.
“We think that this study is novel in that it has high-quality data on both air pollution exposure and stroke diagnosis,†Wellenius says.
The team was able to calculate that the peak risk to patients from pollution exposure occurs 12-14 hours before a stroke. That information may be useful to researchers who want to trace how PM2.5 might be working in the body to increase the likelihood of stroke.
They also found that black carbon and nitrogen dioxide, two pollutants associated with vehicle traffic, were closely linked with stroke risk, suggesting that pollution from cars and trucks may be particularly important.
Stroke is a leading cause of long-term disability and the third leading cause of death in the United States. An estimated 795,000 Americans suffer a new or recurrent stroke every year, resulting in more than 135,000 deaths and 829,000 hospital admissions.
The finding that days of moderate air quality substantially elevate stroke risk compared to days of good air quality suggest that the Environmental Protection Agency may need to strengthen the language it uses to describe the health consequences of moderate air quality, researchers say.
“In partnership with NIEHS, EPA funded this research advancing our understanding of air pollution and health effects,†said Dan Costa, ScD, DABT, Interim National Program Director for Air Climate & Energy Research in U.S. Environmental Protection Agency Office of Research and Development Research.
“In 2009, EPA published an Integrated Science Assessment concluding a causal relationship exists between PM2.5 and cardiovascular impacts, including strokes. Dr. Wellenius and colleagues’ study is the first to show that the onset of stroke can occur with less than a day’s exposure to fine PM. Highly relevant research such as this informs the PM2.5 standards and protects human health.â€
Researchers estimate reducing PM2.5 pollution by about 20 percent could have prevented 6,100 of the 184,000 stroke hospitalizations in the northeastern United States in 2007.
While researchers acknowledge results need to be replicated in other cities, they note that Boston is considered to have relatively clean air.
“The levels of PM2.5 in Boston are lower than those seen in many in other parts of the country, yet we still find that within these moderate levels the risk of stroke is higher on days with more particles in the air,†Mittleman says.
In addition to Wellenius and Mittleman, co-authors include Mary R. Burger, MD, and Gottfried Schlaug, MD, MPH of BIDMC, Brent A. Coull. PhD, Joel Schwartz, PhD, Helen Suh, ScD, Petros Koutrakis, PhD, of the Harvard School of Public Health and Diane R. Gold, MD, of Brigham an d Women’s Hospital.
The study was supported by National Institute of Environmental Health Sciences and the Environmental Protection Agency. One or more of the authors are currently receiving or have received funding from the Health Effects Institute of Boston; the Electric Power Research Institute of Palo Alto, CA; the EPA and the National Institutes of Health.
Beth Israel Deaconess Medical Center is a major patient care, teaching and research affiliate of Harvard Medical School, currently ranks third in National Institutes of Health funding among independent hospitals nationwide. The medical center is clinically affiliated with the Joslin Diabetes Center and is a founding member of the Dana-Farber/Harvard Cancer Center. BIDMC is the official hospital of the Boston Red Sox. For more information, visit www.bidmc.org.
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.
Unrelenting traffic leaves a wake of gritty exhaust for cyclists to breathe.
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.
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.
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 Campaign, 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, aspokesman 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.
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.”
Article Date: 20 Jun 2011 – 16:00 PDT
People with asthma exposed to higher levels of ozone and particulate matter are much more likely to have poorer asthma control, researchers reported in the Journal of Epidemiology and Community Health. Long-term ozone exposure raises an asthma patient’s likelihood to have uncontrolled asthma by 69%, while long-term exposure to particulate matter raises the risk by 35%, the authors added.
Even after taking into account known risk factors linked to poorly controlled asthma, such as obesity, inhaled corticosteroid use, and smoking, the findings still held true.
The researchers explained that prior studies had established a link between air pollution and worsening respiratory symptoms, more hospitalizations and increased use of prescription drugs. However, none had examined what the impact of long-term air pollution might be on asthma control.
The investigators gathered data from the follow-up to the Epidemiological study on the Genetics and Environment of Asthma (EGEA), involving 501 adult participants in five French cities, all with active asthma. They had filled in a questionnaire on respiratory health between 2003 and 2007.
Using data from the Institut Francais de l’Environnement (French Institute of the Environment), they calculated levels of O3 (ozone), NO2 (nitrous oxide) and PM10 (particulate matter) that each participant had been exposed to where they lived.
They measured asthma control according to data gathered on symptoms, asthma attacks, and lung function or FEV1 (forced expiratory volume in 1 second).
Data on pollutant levels were available for 481 patients. 44% of them had well-controlled asthma, 29% had partially controlled asthma, but 27% had poorly controlled asthma.
Calculated average levels of pollutants during the study period were:
Nitrous oxide – were 32 ug/m3
Ozone – 46 ug/m3
Particulate matter – 21 ug/m3
Both ozone and particulate matter levels were strongly linked to poorer asthma control. Long-term ozone exposure increased poor asthma control risk by 69%, and by 35% for particulate matter long-term exposure.
Females and older individuals of both sexes were more likely to experience poorly controlled asthma.
The authors concluded:
“Our results indicate that both ambient O3 and PM10 concentrations jeopardise asthma control in adults. The results are robust.”
Source: Journal of Epidemiology and Community Health
Researchers exposed mice to traffic pollution for five hours a day, three days a week, for 10 weeks. They eventually found out the test subjects’ brains showed signs of inflammation similar to premature ageing and Alzheimer’s disease.
Moreover, the neurons involved in learning and memory loss showed significant damage, and the brain neurons of developing mice did not grow as well as those not subjected to traffic particles.
The study’s senior author, Dr Caleb Finch, said these air contaminants – about 1,000th the width of a human hair – were too small to be captured by vehicle filtration systems. Humans are just as likely to inhale them, which raises the possibility of long-term brain health consequences.
Switching to electric cars would be an easy solution, although Dr Finch cautions that ”electrical generation still depends upon other combustion processes – coal – that in a larger environment contribute nanoparticles anyway”.
Moreover, this study for the first time also shows that a level of ozone below the current safety standard causes people’s airways to become inflamed. This can trigger respiratory attacks in susceptible people, including asthmatics. Increased inflammation also increases response to things to which one is allergic.
What might this study mean to parents whose children are younger than the study participants?
“Even though this study was done in healthy adults ages 19 to 35, the findings clearly have public health implications for asthmatics and others with lung disease of all ages,†said co-author David B. Peden, MD, MS, director of the UNC Center for Environmental Medicine, Asthma and Lung Biology. He is also professor of pediatrics and medicine, and chief of the Division of Pediatric Allergy, Immunology, Rheumatology and Infectious Diseases in the Department of Pediatrics.
To minimize the effect of ozone, Peden said, one should be alert to forecasts of increased ozone exposure in newspapers and on local weather forecasts. This usually occurs in the summer. “If at all possible, people with asthma should not be heavily exercising outdoors in afternoons on days that ozone will be increased,†he advises. “Also, using controlled asthma medications, which are important for asthma control in general, may be especially helpful at times when ozone will be elevated.â€
According to the EPA, variations in weather conditions play an important role in determining ozone levels. Ozone is more readily formed on warm, sunny days when the air is stagnant. Conversely, ozone production is more limited when it is cloudy, cool, rainy, and windy (see: http://www.epa.gov … s/ozone.html).
Peden and co-authors point out that more than 100 million people in the US now live in counties that do not meet the current ozone standard “and [the] public health consequences are enormous.â€
More information: A report of the research appears online in the January issue of the American Journal of Respiratory and Critical Care Medicine.
guardian.co.uk, Wednesday 23 February 2011 18.37
Air pollution is a bigger trigger of heart attacks in the population than physical exertion, alcohol and taking cocaine, a study has shown. On an individual basis, cocaine raises the risk of a heart attack 23 times, says a study published in the Lancet.
But far more people are exposed to traffic fumes and factory emissions than cocaine so air quality is a far more important population-wide threat.
Scientists looked at “final straw” risk factors for triggering heart attacks, rather than underlying causes of heart disease. The highest risk factor was traffic exposure (7.4%), followed by physical exertion (6.2%) and alcohol (5%), coffee (5%), and higher levels of small air pollutant particles known as PM10s (4.8%).
Other risk factors included negative emotions, with a PAF of 3.9%, anger (3.1%), eating a heavy meal (2.7%), positive emotions (2.4%) and sexual activity (2.2%).
Air pollution triggers 5-7% of heart attacks in the population, they say. Cocaine accounts for just 0.9% of all heart attacks.
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