Air quality in the Washington, D.C., region is improving Friday after the area experienced the worst air quality in the world for a time on Thursday.
The D.C. area is under a code orange ("unhealthy for sensitive groups") alert Friday and people with heart or lung disease, older adults, children and teens need to choose less strenuous activities outside or shorten the amount of time they spend outside, according to AirNow.gov.
One noticeable improvement Friday morning: the sky is visible, a stark contrast to the thick haze that nearly completely hid the Washington Monument on Thursday.
The air quality worsened from a code red ("unhealthy") on Wednesday to purple ("very unhealthy"), and then maroon ("hazardous") in parts of D.C. on Thursday as smoke from wildfires burning in Canada brought some of the most polluted air ever recorded in the region.
We're making it easier for you to find stories that matter with our new newsletter — The 4Front. Sign up here and get news that is important for you to your inbox.
The poor air quality led the Washington Nationals to postpone their Thursday game against the Arizona Diamondbacks, the National Zoo closed Thursday and schools moved recess indoors. People who worked outside reported feeling weighed down.
It’s the unseen pollution that poses the greatest health risk, health and environmental officials say.
D.C.’s Air Quality Index (AQI) for PM2.5 — teeny tiny and potentially dangerous particulate matter in the air — hit 314 on Thursday morning. Anything above 301 is considered hazardous. That number dropped to 122 Friday morning, AirNow.gov reported.
PM2.5 particulate matter is so small that it can get deep into the lungs, and possibly your bloodstream. Even short-term exposure can be dangerous, according to the American Lung Association (ALA).
“Premature deaths from breathing these particles can occur on the very day that particle levels are high, or up to a month or two afterward. Most premature deaths are from respiratory and cardiovascular causes,” the ALA said.
Coughing, wheezing, reduced lung function, asthma attacks, heart attacks and strokes are also linked to particle pollution.
Air purifiers can help reduce pollution in your home; even running an air conditioner can help — as long as it doesn't pull in air from outside, AirNow said. You can also use a box fan, cheap filter and some twine to create a DIY filter, NBC News' Jacob Ward explained on TikTok.
Poor air quality can harm your health
Dr. Bobby Mahajan with the American Lung Association recommended that people with underlying heart and lung conditions stay inside.
“People with emphysema, people with asthma — those individuals are at higher risk of getting exacerbations of their disease. So, they've got to be really careful about their symptoms," he said.
Mahajan said everyone should keep an eye out for any symptoms. Even young, healthy people may feel the effects of the smog if they walk around outside or go running.
Don’t let a lack of immediate symptoms in children fool you. Kids’ health can deteriorate as a day progresses, Dr. Shilpa Patel of Children’s National Hospital said. Look out for any irritation to the airways, particularly for a child with asthma.
More than 400 active wildfires are still burning in Canadian provinces and territories.
When will the air quality improve in the DC area?
Poor air quality will stick around Friday, but scattered showers will help to "rinse" much of the smoke out of the air, Storm Team4 Meteorologist Chuck Bell said.
Saturday and Sunday are expected to be remarkably better, with sunshine and clearer skies for weekend activities.
The Associated Press contributed to this report.
Stay with NBC Washington and Storm Team4 for updates.
