Large trucks are a big source of air pollution near roads, according to a study of air in Vancouver and Toronto.

California and 22 other states sued Friday to stop the Trump administration from revoking the authority of the nation's most populous state to set emission standards for cars and trucks.

The most populous U.S. state and Canada said they will work together "to accelerate the adoption of zero-emission vehicles like electric cars" and share technical information and best practices in regulating cleaner fuels, as California does today though its Low-Carbon Fuel Standard.