Air pollution reached dangerous levels in the Los Angeles area Wednesday as lingering fireworks smoke combined with the usual smog across the region, officials said.

The South Coast Air Quality Management District issued an air quality alert for L.A., Orange, Riverside and San Bernardino counties where particulate matter (PM2.5) readings soared into the mid-200s in some locations.

Short-term pollution, especially in Southern California’s Inland Empire, was among the worst in the world Wednesday, even topping China and India.

Fireworks air pollution map
A map showing air pollution levels in the Los Angeles area. July 5, 2023. (South Coast AQMD)

The alert extends through Wednesday evening.

“Breathing of fine particulate matter can lead to a wide variety of cardiovascular and respiratory health effects such as heart attacks, asthma aggravation, decreased lung function, coughing, or difficulty breathing and may lead to premature death in people with heart or lung disease,” South Coast AQMD said in its advisory.

Pollution levels between 101 and 150 are considered “unhealthy for sensitive groups,” meaning those with respiratory or heart disease, older adults, and children should avoid prolonged time outdoors.

Purple Air pollution map
Purple Air pollution map for Los Angeles on July 5, 2023. (Purple Air)

When the Air Quality Index exceeds 150, as they have in the San Gabriel Valley, everyone is urged to limit outdoor activity.

To help keep indoor air clean, experts recommend closing all windows and doors and running your air conditioner and/or air purifier.

“If possible, do not use swamp coolers or whole house fans that bring in outside air,” South Coast AQMD said. “Avoid burning wood in your fireplace or firepit and minimize sources of indoor air pollution such as candles, incense, pan-frying, and grilling.”

The Los Angeles skyline is seen on July 5, 2023. (KTLA)
The Los Angeles skyline is seen on July 5, 2023. (KTLA)

Experts say fireworks emit high levels of particle pollution as well as metal air pollutants, all of which can contribute to negative health effects.

Residents are encouraged to download South Coast AQMD’s mobile app for iOS and Android to receive real-time air quality alerts and weather information.