Pay attention to pollution to combat asthma symptoms: case study

By Kathryn Doyle

NEW YORK (Reuters Health) - For a 38-year old professor who cycled to work every day, asthma symptoms tended to be worst in midmorning and early afternoon on weekdays, but improved noticeably on weekends.

Her doctor suspected the air pollution on her commute was provoking her asthma, so he mapped a new route further from major roadways. Within a month, her wheezing and other symptoms had decreased dramatically, according to the authors of a review of her case.

“It has long been suspected that avoiding air pollution is a good idea for people with asthma,” said senior author Dr. Chris Carlsten of Vancouver General Hospital in British Columbia.

But it’s not clear if people with asthma are at greater risk from pollution than people without asthma, or exactly what levels of air pollution should prompt strict avoidance, he told Reuters Health by email.

There’s enough evidence to say that air pollution exacerbates existing asthma, Carlsten and his colleagues write in the Annals of Allergy, Asthma and Immunology. And there’s growing evidence that exposure to pollution can cause new cases of asthma, the researchers say.

It’s estimated that 120 million people in the U.S. live in areas where air pollution regularly exceeds levels considered safe, they note.

Asthma is an inflammation of airways that causes them to swell and constrict, and can be triggered by dust mites, animal dander, molds or pollen. The condition affects about one in 12 Americans, according to the Centers for Disease Control and Prevention.

The professor had not suffered from asthma symptoms since childhood but she reported that she had just moved from a rural to an urban area and her bike commute now took her along streets with heavy traffic.

As directed, she used a peak flow meter to measure her maximum speed of exhalation four times daily for a month. The lower the reading, the more airways are obstructed.

Her readings were above 500 liters per minute on the weekend and in the early mornings, but around midday on weekdays they dipped to 400 L/min as she complained of wheezing.

Her doctor examined her daily biking route, 70 percent of which took her within 1,000 feet (300 meters) of major roadways. He helped her design a new route with only 15 percent of her time in close proximity to heavily traveled streets.

She reported much less wheezing over the next month, according to the case review.

“We have quite a bit of evidence that admissions to hospital for respiratory illness tend to go up during periods of high air pollution,” said Michael Jerrett, professor and chair of Environmental Health Sciences in the School of Public Health at the University of California, Berkeley, who was not involved in the professor’s case.

“The novelty here is that they’re making the argument that they were able to use public health messages to make a change for an individual patient,” Jerrett told Reuters Health.

Pollution levels can be much higher in areas of heavy vehicle traffic, and your lungs are especially vulnerable while biking or otherwise exercising since you are inhaling more air, he said.

Anyone who actively commutes should try to avoid major arterial roads or highways, he said. Repeated exposure to air pollution can bring on asthma, cardiovascular disease and chronic obstructive pulmonary disease.

“While we can’t say one ride on a bicycle is going to affect your health, if you repeatedly take the same route, there is a reasonable likelihood that you are going to experience an adverse effect,” Jerrett said.

“Today, most urban regions regularly measure air pollution levels and make them easily available on the Internet and, often, in newspapers,” Carlsten said. “A caution, however, is that these data typically represent an average for a rather large geographic area, and we know that there are microenvironments - with varying pollution levels - within such large areas.”

Rural areas have different sources of pollution than those in urban environments, but the basic principle of avoiding the worst pollution for airway health holds true, he said.

A primary care physician may not have information on local pollution levels readily available, Jerrett noted.

Air pollution aside, the best things people with or without asthma can do are maintain cardiovascular fitness, a healthy diet and otherwise sound general health practices, Carlsten said.

“These fundamentals are unfortunately all too often overlooked as we point, quite reasonably, to the hazards of our environment,” he said.

SOURCE: Annals of Allergy, Asthma and Immunology, online August 16, 2014.