But air quality can vary on a hyperlocal scale, meaning the network of official sites is "fairly sparse," says Michael Jerrett, an air pollution expert at the University of California, Los Angeles.

Mesquite, for instance, had an air quality index of 225 on Wednesday evening. That's considered "very unhealthy," according to AirNow , a government tool tracking air quality.

More than 125 million people live in counties with F grades for ozone pollution, the lowest grade possible and reflective of a poor score that involves the Air Quality Index.

More than 125 million people live in counties with F grades for ozone pollution, the lowest grade possible and reflective of a poor score that involves the Air Quality Index.

The Air Quality Index, or AQI, is the primary system used to warn the public when air pollution is dangerous. It’s based on data collected from 5,000 air monitors across the country.

Air quality levels across large swathes of California have deteriorated as fires, such as the newly ignited Hughes Fire, continue to burn in and around Los Angeles. While air quality in Southern ...

Air quality is a big concern for everyone in Southern California, even for those who don't live near fire zones. Here are answers to some of your top questions. 24/7 Live Los Angeles Orange County ...

What the Air Quality Index doesn’t tell us about the air This moment demands more than headlines In a time of noise, confusion, and spin, we’re committed to clarity, truth, and depth — even ...

The U.S. Environmental Protection Agency (EPA) issues an Air Quality Index (AQI) for five pollutants, including fine particle pollution, (PM2.5) and ozone. The rates are as follow: Good: 0-50 ...

The South Coast Air Quality Management District issued a smoke advisory through Monday night due to the Line and Roblar Fires in Southern California. The Roblar Fire in San Diego County has burned ...

KTLA’s Air Quality Map of Southern California shows wide swaths of the area have air quality that is unhealthy — meaning the air quality index is between 151 and 200 — with some areas listed ...