The American Lung Association has given failing grades for air quality to multiple California cities and counties. San Bernardino and Riverside have again been ranked as the worst for ozone pollution.

According to the organization's annual State of the Air report, which was released earlier today, 34 million Californians live in a county with a failing grade. The report shows that San Bernardino County remains one of the smoggiest areas in the state. The county experienced about five months, or 152 days, worth of unhealthy ozone pollution. Riverside County had 84 bad smog days.

Other Southern California counties, including Los Angeles, Orange, Imperial and San Diego, received ‘F’ grades for ozone.

During a Tuesday press conference held by the American Lung Association, clean air advocates raised concerns about the Environmental Protection Agency under the Trump Administration, warning that their proposed rollback of federal regulations could reverse decades of air quality progress in California.

Mary D. Nichols, UCLA law professor and former chair of the California Air Resources Board, said the rollbacks would jeopardize long-standing improvements in reducing pollution across the state.

“We'll have more people going to hospitals with asthma attacks,” said Nichols. “We'll have more workers losing days of work because of poisoning by particulates from coal and diesel fuels, and we'll see people dying sooner than they should have, just because of the poison in the air.”

Ana Gonzalez, the executive director at the Jurupa Valley-based Center for Community Action and Environmental Justice, attributes the poor smog to increased truck traffic attracted by warehouses in the Inland Empire. The worsening air quality continues to be a significant concern for parents and educators across the region, shared Gonzalez.

“Our kids are going to be missing school or be sick for some time,” she said. “And that's really sad…it's almost like they're adapting to it.”

Some air advocates say there’s still reason for hope. About 12 cities reported their lowest ever results for ozone and particle pollution, according to the report. Between 2021 and 2023, Fresno recorded some of its lowest levels of ozone and particle pollution.

Dr. Alexander Sheriffs, a board member with the San Joaquin Valley Air Pollution Control District, says these improvements have been possible because industry and regulators have worked together to fulfill the promise of the Clean Air Act.

“We can make progress, meaningful progress, in one of the most challenged air basins in our state and nation,” said Sheriffs.

Read the full report on the American Lung Association’s website.