California air quality officials are poised to adopt their biggest pollution-cutting regulations in more than a decade, targeting diesel trucks and cargo ships that spew much of the state’s cancer-causing and smog-forming emissions.

The state Air Resources Board is expected to vote after a public hearing Thursday on two rules: one to establish stringent new emissions standards for heavy-duty diesel trucks and one to reduce pollution from ships docked at ports.

Together, the measures take aim at what remain the largest, most poorly controlled pollution sources in California. Diesel trucks emit nearly one-third of smog-forming nitrogen oxides and more than one-quarter of diesel particulate matter in the state. Oceangoing ships are projected to surpass trucks to become Southern California’s largest source of nitrogen oxides by 2023.

The truck standards face significant opposition from engine manufacturers, while ports and labor unions have sought to delay the ship pollution reduction measures, citing the COVID-19 pandemic. But the measures can’t come soon enough for people living in some of the nation’s worst-polluted corridors near ports, warehouses and other freight-clogged areas, largely lower-income communities of color that have long suffered from dirty air and higher rates of cancer and asthma.

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