A satellite image of low-level smoke in Northern and Central California.
Towns in northern and central California registered some of the worst air quality in the world Thursday because of smoke from wildfires burning in the state, according to data from the federal government.
Why it matters: Microscopic particles suspended in wildfire smoke are a danger to the public and have been linked to decreased lung function, aggravated asthma, heart attacks and premature death in people with heart and lung disease, according to the Environmental Protection Agency.
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By the numbers: A monitor near Placerville, California, measured hazardous air quality at 10am PT, reporting a value of 901 on the U.S. air quality index (AQI) for particles that are 2.5 microns or less in diameter.
Other monitors reported hazardous air quality east of Folsom, southwest of Redding and around Lake Tahoe and Lake Almanor.
Screenshot from fire.airnow.gov
Our thought bubble, via Axios' Marisa Fernandez: This is historically hazardous air quality. The AQI doesn’t even have guidance on hand for residents when PM2.5 levels go beyond 500.
Even healthy people can experience symptoms if they are not inside with the windows closed, such as eye, nose and throat irritation, coughing, phlegm, chest tightness and shortness of breath.
The situation can be more dire for people with lung or heart problems.
Yes, but: The extremely unhealthy air quality in the region can change rapidly, and symptoms can be temporary once it improves.
Those in countries like China and India and even some U.S. cities have been harmed by long-term exposure to air pollution. One study found the cumulative exposures worsened lung function and were significantly associated with increasing emphysema.
The U.S. government recommends that people reduce their exposure to hazardous air by staying indoors — preferably in a room or building with filtered air — and reducing activity levels.
Go deeper: Wildfire smoke has impacts across America
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