Wildfire season is in full swing, with more than 100 blazes burning across the United States.
The largest, California's Park Fire, has covered more than 562 square miles of Northern California and is only 12% contained. Fueled by gusty winds and hot weather, dozens of fires are also burning in Oregon, Idaho, Nevada, Washington, Utah, Wyoming, New Mexico, Montana, Arizona and Colorado.
Nearly 1,000 fires are also actively burning in Canada, sending smoke down over the U.S.
Thick smoke from the wildfires is causing dangerous air quality conditions, triggering air quality alerts for millions of people across the northwestern U.S. and parts of western Canada, according to the U.S. Air Quality Index's Fire and Smoke Map, which tracks current conditions.
Studies have shown even short periods of exposure to elevated levels of fine particulate (PM2.5), which is in wildfire smoke, can trigger asthma attacks requiring emergency medical treatment. Particles in the PM2.5 size range are able to penetrate deeply into the respiratory tract, reaching the lungs and bloodstream, according to IQAir, which reports real-time air quality conditions around the globe. Exposure to fine particles can cause short-term health effects such as eye, nose, throat and skin irritation, coughing, sneezing, runny nose and shortness of breath. It can also affect lung function and worsen medical conditions such as asthma and heart disease.
"It's the fact that you're breathing in such a concentrated amount of that smoke, and we don't normally see that," said KYW Newsradio medical editor Dr. Brian McDonough. "It can make anybody — even really healthy people's lungs — hyperactive. In other words, they start getting twitchy, they spasm. If you have asthma, it can trigger things that obviously put on stress, if you have heart disease or other issues."
While wildfire smoke may present a risk to everyone, there are those who are more at risk because of preexisting conditions. Older adults aged 65 and older, pregnant people, children, and people with lung and heart conditions may be more likely to get sick if they breathe in wildfire smoke.
There are a number of steps you can take to reduce your exposure to smoke, such as limiting outdoor activity and going indoors to cleaner air.
The most protective option when air is unhealthy is to stay indoors with air conditioning, reduce strenuous activities and limit outdoor activities. If you must be outside, keep activity levels low; N95 masks offer enhanced protection.
"This is not the time to play that tennis match or go golfing," said McDonough. "I know it's disappointing, but it's not worth the risk. That continued exposure — even for people who are out for a short period of time — they'll talk about how they feel their throats are a little irritated, they smell like smoke. That's how bad it is."
You can check on the current air quality status to know when it is and isn't safe to be outside by visiting the Environmental Protection Agency's Air Quality Index.
To keep your air as clean as possible while indoors, the CDC says to run an air conditioner and ensure that the fresh-air intake option is closed and the filter is clean.
"If you do not have an air conditioner and it is too warm to stay inside with the windows closed, go to a designated shelter away from the affected area," the CDC said.
The CDC also warns that people should avoid burning candles, using fireplaces, vacuuming, and operating gas stoves, as they can increase indoor pollution or stir up pollutants.
If you find that you're struggling to breathe or that you just don't feel right, seek emergency care as soon as possible. Call 911 or contact a health care provider.