The rule will affect approximately 350 facilities in the area emitting more than 10 tons per year of ozone producing pollutants rather than the current threshold of 25 tons per year.

The approved action is part of an ongoing effort to improve air quality in the San Joaquin Valley, which is currently designated as an extreme nonattainment area for ozone or smog.

In addition, US EPA revised the state’s Clean Air Plan to make it consistent with state law, which requires permitting of agriculture facilities emitting more than 5 tons per year of ozone producing pollutants.

This rule change will be effective 30 days after the day of publication in the federal register.

Deborah Jordan, director of air division at EPA, Pacific Southwest region, said: ”Air quality in the San Joaquin Valley is consistently among the worst in the nation. New and modified facilities will now be subject to the most stringent requirements, which will contribute to the health of our communities.”