The cheap, asphalt-like diesel that oceangoing ships currently burn has a sulfur content many thousand times higher than the diesel sold for U.S. trucks, leading to unsafe sulfur oxide emissions that can aggravate asthma and cause other respiratory illnesses.
"The folks who live around ports and who work at the ports deserve to have the cleanest air possible. That fuel is available," Boxer said before the committee passed the bill on voice vote, sending it to the full Senate.
The South Coast Air Quality Management District, a Southern California air-regulatory board, has said that marine vessels are the largest uncontrolled sources of air pollution in many areas of the country and responsible for at least 2,000 to 5,000 premature deaths each year.
Republicans contended that the most polluted ports can be found in Boxer's home state, particularly the giant ports of Los Angeles and Long Beach.
"The problem is not universal. The problem is in California right now," said Sen. James Inhofe, R-Okla., top committee Republican. "Perhaps if I were a senator from California I would be supporting this, too, but I'm not."
Boxer disagreed, saying "we have nationwide impacts all across this great country."
The committee action comes as the Environmental Protection Agency has offered pollution reduction proposals for oceangoing ships to the U.N. International Maritime Organization, which is considering them. An IMO subcommittee passed the U.S. proposals in April and the full body may take them up in October, but environmental groups and some Democrats fear the IMO won't act or will end up passing a weaker rule.
Boxer's bill proposes faster reductions in fuel sulfur content than the U.S. proposals before the IMO.
Republicans said the U.S. could be put at an economic disadvantage if it has tighter pollution rules for its ports than other countries. Some 90 percent of emissions come from foreign-flagged ships, according to Boxer.
An amendment by Sen. David Vitter, R-La., meant to keep U.S. air emissions standards consistent with international ones, failed 11-8.