Three California cities no longer have to monitor carbon monoxide levels

US environmental regulators have removed carbon monoxide monitoring requirements for three urban areas in California. This means the cities of Chico, Modesto, and Stockton no longer have to track air quality for this specific pollutant.

For decades, cities had to prove they were cleaning up their air. This rule change means these three cities have now officially met their targets for carbon monoxide. They no longer need to report on it. This frees up local resources and signals that air quality has improved enough in these areas to remove federal oversight.