What is the most polluted city in California?

The most recent data available indicates that the most polluted city in California based on air quality is Bakersfield, as reported by the American Lung Association's "State of the Air" report for 2021.

Bakersfield has consistently been ranked as one of the most polluted cities in the United States due to several factors, including its location in a valley that traps air pollution, agricultural activities, and emissions from transportation and industry.

The report assessed ozone, particulate matter (PM2.5), and year-round particle pollution (PM2.5 annual mean) levels in cities across the country. Bakersfield had some of the highest annual average concentrations of these pollutants among all cities in California.

It's important to note that air quality can change over time, and rankings may vary based on specific timeframes and the pollutants being considered. For the most up-to-date and localized air quality information, it is recommended to refer to official sources such as the California Air Resources Board (CARB) or the local air quality management district.