Bad Air Day

In many parts of the country, summer has the worst air quality of any season. When the forecast says it’s a code red day for air quality, what does it mean for your health? If you’ve planned a picnic, a bike ride or even a walk with a friend, should you change your plans?

“The answer depends on a lot of factors. There’s no simple ‘yes’ or ‘no’ answer for everyone,” says Dr. Darryl Zeldin, acting clinical director of environmental health sciences at NIH. He and other NIH-supported researchers have been studying how substances in the air can affect health. Knowing more about air quality and air alerts will help you make smart decisions about spending time outside this summer.

The combination of high temperatures, few winds and breezes, pollution and airborne particles can brew up an unhealthful mixture in the air, just waiting to enter your lungs. These substances can make it hard to breathe and can sap your energy. If the air quality is especially poor, it may take a few days for your body to recover. And if you’re regularly exposed to high levels of unhealthy air, the health consequences can linger for months or even years.

One of the most-studied pollutants in summertime air is an invisible gas called ozone. It’s created when sunlight triggers a chemical reaction between oxygen-containing molecules and pollution that comes from cars, power plants, factories and other sources.

“Ozone is produced only when you have sunlight and high temperatures or stagnant air, which is why ozone is generally not a problem in the winter,” says Dr. Frank Gilliland, an expert in environmental health at the University of Southern California. “High levels of ozone reduce lung function and lead to inflammation, or swelling, in the airways. When the levels are high enough, you can get symptoms like coughing or throat irritation. Your eyes might water. Your chest might hurt when you breathe.”

Ozone is a highly reactive molecule that can irritate the lining of your airways and lungs. If you have a lung condition like asthma, the damage can be more harmful. “When people with poorly controlled asthma are exposed to just a little bit of ozone, the amount of inflammation in the lungs goes way up, and the airways become more twitchy,” says Zeldin. “As a result, air passages narrow, which makes it harder to breathe.”

Ozone’s effects can come on quickly and linger or even worsen with time. “When people hear it’ll be a bad air day, most expect their breathing will be affected that day. But in fact, they often feel the effects most strongly the next day or the day after,” says Dr. David Peden, an environmental medicine researcher at the University of North Carolina at Chapel Hill. “This is especially true for people with asthma. When there’s a bump in ozone levels, asthma usually gets worse or out of control a day or 2 after exposure. We often see an increase in emergency room visits, hospitalizations and use of asthma ‘rescue’ medications.”

Researchers have also been studying particulates—the fine and coarse particles that spew from things that burn fuel, like cars, power plants and wildfires. Particulates, unlike ozone, can cause health problems year-round. Like ozone, particulates have been linked to a worsening of lung problems, especially asthma. Particulates and ozone also are associated with increased cardiovascular events, such as stroke and heart attack.

Symptoms of Bad Air Quality

Common symptoms people may feel include:

  • Eye irritation.
  • Wheezing or difficulty breathing.
  • Irritation and inflammation of the respiratory tract (coughing)
  • Shortness of breath, especially during physical activity.
  • Aggravation of existing asthma, heart and lung conditions.

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