California air quality officials have passed two new measures aimed at reducing pollution from diesel trucks and ships. One rule introduces new emissions standards for heavy-duty diesel trucks, while the other requires more ships docked at ports to either plug into electric power or use other technology to reduce harmful emissions. The state has the worst-polluted air in the country, The Los Angeles Times reported.

The “Heavy-Duty Low NOx Omnibus Regulation” requires truck manufacturers to comply with tougher emissions standards, revamp engine testing procedures, and further extend engine warranties to ensure emissions are reduced, according to a statement from the California Air Resources Board. The rule targets nitrogen oxides, which are a major component of smog. Once the rule is fully phased in by 2031, CARB expects it will reduce nitrogen oxide emissions in the state by more than 23 tons per day.