Maine can do only so much to improve the quality of air in the state. Much of the work requires a national approach and a commitment from the federal government to reduce airborne pollution.

But Tuesday, Gov. Baldacci signed into law legislation that moves the state forward with a progressive approach to vehicle emissions that will reduce the amount of smog-producing pollution and greenhouse gases produced in the state. Cars and trucks driving on Maine roads are the largest single source for air pollution in the state, producing about a third of all greenhouse gases and about 90 percent of four other dangerous emissions. Almost 70 percent of the state’s population live in areas that do not meet health standards for smog. In addition, Maine has the highest rate of asthma in New England, a problem that is made worse by air pollution.

According to the law, automobile dealers must increase the number of hybrid and low-emission vehicles they offer for sale to about 10 percent of their stock by 2009. A broad coalition of environmental and public health organizations supported the law. Its implementation will improve public health and make sure consumers have environmentally friendly choices when they go to buy a new vehicle.

Passage of the law is a great step forward. Maine has done what it can. Now it’s up to the federal government and other states to follow the good example.