California's San Joaquin Valley gets new numbers for car pollution limits

US environmental regulators are proposing new limits for car pollution in California's San Joaquin Valley. These limits will dictate how much nitrogen oxides and volatile organic compounds cars can emit in the region for the next decade.

This is a technical update to how air pollution is measured and controlled in a specific region. It means local planners must now use different numbers when approving transportation projects. The change reflects updated scientific models for how vehicle emissions contribute to ozone.