Outdoor Pollution and Lung Function Effects

Experts explain air pollution's impact on health and the steps you can take to protect your lungs.

Medically Reviewed by Brunilda Nazario, MD on August 04, 2009

In 1996, the city of Atlanta took dramatic steps to improve the city's air quality for the summer Olympics. In the process, it showed how reducing air pollution can improve lung function.

What city officials did -- switching to rapid transit and buses that ran on natural gas instead of diesel -- decreased asthma attacks by up to 44% in children and ozone concentrations by 28%, the CDC reported in a study in 2001 in The Journal of the American Medical Association.

"It seemed easier to breathe," recalls Carol Lincoln, 44, who attended the summer games. The skies were "bright and blue" instead of "the sooty gray we're so used to," she says. "Things seemed cleaner. It was so obvious that we talked about it."

Study author Michael Friedman, MD, of the CDC says the results showed that reducing air pollution improves lung health. Here's what we know about how the two affect each other:

What are the different types of pollution?

Ozone, the primary component of smog, is created by a chemical reaction that occurs when sunlight interacts with particulates (soot) from motor vehicle exhaust, gasoline vapors, and dust from power plants.

Particulate matter, also known as particle pollution, includes nitrates, sulfates, organic chemicals, metals, and soil or dust particles; it is a complex mixture of tiny particles and liquid droplets.

Nitrogen dioxide, or NO2, is one of a group of highly reactive gasses. NO2 forms quickly from emissions from cars, trucks, buses, power plants, and off-road equipment. According to the Environmental Protection Agency (EPA), this compound reacts with ammonia, moisture, and other compounds to form small particles. These small particles penetrate deeply into sensitive parts of the lungs and can cause or worsen respiratory disease, such as emphysema and bronchitis, and can aggravate existing heart disease, leading to increased hospital admissions and premature death.

Carbon monoxide, or CO, is an odorless, colorless gas formed when carbon in fuel isn't completely burned. Higher levels of CO occur in areas with heavy traffic congestion. It is a component of motor vehicle exhaust, which contributes about 56% of all CO emissions nationwide. Other sources are cigarette smoke, wood and gas stoves, and industrial emissions.

Sulfur dioxide gases are formed when fuels containing sulfur, like oil and coal, are burned, or when metals are extracted from ore. It interacts with other pollutants and can be harmful.

Lead is now mostly found near waste incinerators, utilities, and battery manufacturers. Lead emissions from gasoline have declined by 95% since the EPA began regulating clean air standards more than three decades ago.

Pollutants are regulated by the EPA.

How do the different types of pollutants in air pollution affect lung function?

Dennis Ownby, MD, chief of allergy-immunology at the Medical College of Georgia, tells WebMD that it's difficult to separate the negative effects of the various pollutants because they all damage the lungs, kill protective cells, and can cause cardiovascular disease and heart attacks.

But in particular, ozone, particulates and sulfur dioxide "inflame the linings of the lungs," which makes them work harder and can cause heart attack, he says. Sulfur dioxide and ozone react chemically with surfaces inside the lungs, causing inflammation that produces mucus, coughing, and serious breathing trouble.

Perhaps most is known about ozone, which increases susceptibility to respiratory infections and causes flare-ups in people with chronic lung problems and stresses the arteries and heart. Michael Jerrett, PhD, associate professor of environmental health at the University of California-Berkeley, reported in a recent New England Journal of Medicine study that long-term exposure to the sooty gas at ground level increases the risk of death from respiratory problems by more than 30%.

"Our study showed us that ozone is more harmful than we thought," Jerrett tells WebMD.

Among particulate matter, small particulates stay in the lungs longer and get picked up by white blood cells. But the more pollution of any kind, the harder this becomes, which is why the lungs of smokers and people who live in polluted cities are dark gray or black. "There's no way for the body to get the junk out again," Ownby says.

Cherry Wongtrakool, MD, a pulmonary specialist at Emory University, says people with lung problems like asthma and chronic obstructive pulmonary disease are more susceptible than others to ozone and particulate matter, which can result in coughing, wheezing, and shortness of breath. Long-term exposure may lead to atherosclerosis, or hardening of the arteries, she says.

For people who live in cities, it's an ongoing battle, and the lungs gradually lose the ability to clear the pollution and fight back, Ownby says.

Wongtrakool says air pollution not only can worsen lung function in people with breathing problems but also can decrease lung function in those with healthy lungs. Inhaling pollution makes healthy lungs sick over the long term, causing coughing, wheezing, irritation, and dangerous stress on the cardiovascular system.

Are there certain parts of the country where pollution is worse than others?

Without doubt, Jerrett says. He says his recent study examined 18 years' worth of data from 96 metropolitan areas and nearly 450,000 people. The highest concentrations of ozone and highest death rates due to ozone are in southern California; the lowest in the Northwest and parts of the Great Plains. In general, cities in the Northeast had lower ozone than California, though some have dangerously dirty air. People in New York had a 25% increased risk of dying from lung disease, compared to 43% in Los Angeles. Among the most ozone-rich cities were Washington, D.C.; Richmond, Va.; Chattanooga, Tenn.; and Charlotte, N.C. Low concentrations were recorded in places like San Francisco, where dirty air is blown away by ocean winds.

How can I protect myself and my family from the effects of pollution?

"If you live in a big city, you can reduce your exposure to air pollution by limiting time in the car, remaining indoors during the heat of the day, typically afternoon and early evening, [and] reducing time spent doing outdoor activity," says Wongtrakool of Emory.

Edward Postlethwait, PhD, of the University of Alabama, Birmingham, and his colleague, Michelle Funucchi, PhD, advise exercising in the mornings, and if you have a choice, not to live within 500 feet of busy highways.

"Have a well-ventilated kitchen," Funucchi adds. "Pay attention to air quality alerts. At the highest levels, don't exercise outdoors and minimize your time outdoors."

Postlethwait points out that this can post a catch-22 situation. Riding a bicycle, for instance, is very good exercise, but not when pollution levels are high.

"Wearing masks is not the answer," he says. "In the Olympics in Beijing you saw folks riding bikes wearing facial masks that didn't fit very well. A true respiratory mask might protect you, but not some dorky kind of surgical mask."

Other suggestions for reducing pollution:

  • Don't burn wood in your fireplace.
  • Use HEPA air filters; usually these filters or electronic air cleaners trap a large amount of circulating dirty particles.
  • Stay well nourished; there's evidence that fish oil and vitamin C can help damage caused by pollutants.
  • Carpool to work or take public transportation.
  • Lobby for schools to replace their diesel buses, or at least to prohibit them from idling while waiting to pick up children.
  • Put a fan or low-speed vent circulator in your garage.

Are there any warning signs that my lung function may be affected by pollution?

Yes. People with asthma and chronic bronchitis are prone to cough and wheeze, and they experience chest pain and shortness of breath during periods of high pollution, says Stan Fineman, MD, of the Atlanta Allergy and Asthma Clinic.

Pollution makes lungs more vulnerable to respiratory infections, causes headaches, even triggers heart attacks, says Janice Nolen of the American Lung Association.

"People with chronic diseases like chronic obstructive pulmonary disorder and asthma are going to have a harder time breathing," she says. "The Atlanta study shows this clearly, when fewer kids had to go to the emergency room."

Other signs of potential problems include:

Show Sources


Edward Postlethwait, PhD, University of Alabama-Birmingham.

Michael Friedman, MD, CDC.

Michael Jerrett, PhD, University of California, Berkeley.

Dennis Ownby, MD, Medical College of Georgia.

Cherry Wongtrakool, MD, Emory University.

Janice Nolen, American Lung Association.

Stan Fineman, MD, Atlanta Allergy and Asthma Clinic.

Carol Lincoln, Smyrna, Ga.

Friedman, M. The Journal of the American Medical Association, Feb. 21, 2001; vol 285: pp 897-905.

Jerrett, M. New England Journal of Medicine, March 12, 2009; vol 360: pp 1085-1095.

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