The American Lung Association has released its annual State of the Air report chronicling air pollution throughout the country - and Valley cities still receive failing grades, despite some improvements.
The report ranks pollution levels for the years 2014-2016. Thanks to the Clean Air Act and lower vehicle emissions, particle pollution overall has dropped. Most cities, including those in the San Joaquin Valley, saw fewer days of unhealthy particle pollution compared to previous years.
Ozone pollution, however, worsened. During a press conference, Janice Nolen of the American Lung Association explained: It has to do with changing climate and rising temperatures, globally and in California.
"As you may know, ozone doesn’t come out of a tailpipe or smokestack - the emissions that create it do," Nolen said. "It cooks in the atmosphere in the presence of sunlight and heat. And the more heat, the more likely ozone is to form."
Valley cities still remain some of the most polluted in the country. The Bakersfield area ranks the worst for short-term particle pollution while the metro areas of Fresno, Merced, Visalia and Bakersfield rank in the top 10 worst for both particle pollution and ozone.
The report also raises alarm about changes to the Clean Air Act being considered by the Trump administration.