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Asthma Center

Ozone, Air Quality, and Asthma

If your child has asthma, you probably understand triggers — those substances or activities that bring on breathing problems.

But what if the asthma trigger is in the air your child breathes? Ground-level ozone and other air pollutants can trigger worsening symptoms and asthma flare-ups. But you can help minimize your child’s exposure.

About Ozone

Ozone is a gas that’s found in both the Earth’s upper and lower atmospheres. The protective ozone in the upper atmosphere is very different from the harmful ozone in the lower atmosphere. Ozone that exists naturally 10 to 30 miles (16 to 48 kilometers) above the Earth protects us all from the sun’s ultraviolet (UV) rays.

But ground-level ozone is different. It’s found close to Earth’s surface and is a serious pollutant. It’s produced when sunlight combines and reacts with chemicals produced by cars, power plants, and factories. That’s why ground-level ozone, a main component of smog, tends to be higher in sunnier climates or during hot, still weather.

Ground ozone levels have declined somewhat since 2000, but according to the American Lung Association, 38% of the population of the United States live in areas with unhealthy ozone levels. This includes 2.5 million kids with asthma who live in towns or cities with very high levels of ozone.

Other Pollutants

Although ozone gets a great deal of press, it’s not the only pollutant that causes poor air quality. In 2004, for the first time, the American Lung Association included not only ozone but particle pollution levels in its annual “State of the Air” report for the United States.

Particle pollution refers to tiny particles of acids (such as nitrates and sulfates), dust, dirt, smoke, soot, and droplets from aerosols that are suspended in the air we breathe. The smaller the particles, the deeper they can get into the lungs, where they cause problems.

Particle pollution data are graded by both year-round and short-term levels:

  • More than 44 million U.S. residents, including more than 125,000 kids with asthma, live in areas with levels of particle pollution that are unhealthy year-round.
  • More than 47 million Americans live in areas that experience too many days with short-term spikes (from several hours to several days) in particle pollution, including more than 940,000 kids with asthma.

In addition to ozone and particle pollution, other pollutants include gases such as carbon monoxide, sulfur dioxide, and nitrogen dioxide. High levels of these gases can also affect lung function.

How Poor Air Quality Affects People With Asthma

Air pollution is a problem for everyone — not just people with asthma. Studies have shown that high levels of air pollution can be associated with decreased lung function and more frequent reports of respiratory symptoms. This is especially true for people who spend a lot of time outdoors.

Kids may be particularly affected by pollution levels because they:

  • play outdoors
  • have faster breathing rates
  • have lungs that are still developing

But although high levels of pollution affect everyone, people with asthma are more sensitive and experience the effects more quickly and severely. Additional studies have shown that ozone, particle pollution, and other forms of air pollution worsen asthma and increase hospital visits for people with asthma. And again, it’s kids with asthma who are especially vulnerable to these effects.

Pollutants in the air have the same effect on people with asthma as other triggers. They reduce lung function by inflaming the lining of the lungs. Exposure to pollutants in the air can cause flare-ups and may increase the chance of upper respiratory infections, which can worsen asthma symptoms. If allergens in the air are an asthma trigger, pollutants can make the lungs even more sensitive to them.

What You Can Do

An important aspect of managing your child’s asthma is avoiding triggers. That means you should pay attention to pollution levels and plan accordingly when they’re going to be high.

The Air Quality Index (AQI) was created by the Environmental Protection Agency (EPA) to monitor outdoor air quality. In more than 900 counties across the United States, it measures levels of five major air pollutants regulated by the Clean Air Act:

  1. ground-level ozone
  2. particle pollution
  3. carbon monoxide
  4. sulfur dioxide
  5. nitrogen dioxide

Using a color-coded system, the Air Quality Index indicates when air quality is dangerous. Green or yellow are acceptable colors; orange, purple, or maroon mean people with asthma should limit their time outdoors.

The Air Quality Index varies from season to season, from day to day, and even from morning to evening. In cities larger than 350,000 people, state and local agencies are required to report the index to the public daily. But many smaller communities also report the AQI. In many places, the next day’s index is reported, so you can make plans.

You can get Air Quality Index information:

  • from weather reports
  • in the newspaper
  • at

On days when air quality is poor, run the air conditioning and limit your child’s time outside. Plan any outdoor activities for early in the day — when air quality tends to be better — and avoid spending time in areas with a lot of traffic.

If your child participates in a sport that practices outside during hot weather, talk to the coach about other arrangements, such as working out in an air-conditioned gym. Also, make sure your child always has rescue (fast-acting) medication on hand.

Improving the air quality in your home is also wise. You can do this by using an air cleaner, venting all gas appliances to the outside, and avoiding wood fires in your house.

Talk to your doctor about increasing medication during times when air pollution is high. This can be included as part of your child’s asthma action plan.

And although you can’t single-handedly solve air pollution, you can take these important steps to help improve it when the air quality is poor:

  • Don’t drive — share a ride, take public transportation, ride a bike, or walk.
  • Don’t put gas in your car until after 7 p.m.
  • Avoid using outboard motors, off-road vehicles, or other gasoline-powered recreational vehicles.
  • Avoid mowing your lawn or using other gasoline-powered gardening equipment until the late evening or until the air quality improves.
  • Don’t use paints, solvents, or varnishes that produce fumes.
  • If you’re barbecuing, use an electric starter instead of charcoal lighter fluid.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: January 2014