How do oceangoing vessels harm U.S. air quality?
Ocean-going vessels dock at over a hundred ports in the U.S., including some along navigable waterways in the nations interior. More than 40 of these ports are in metropolitan areas that do not meet the National Ambient Air Quality Standards (www.epa.gov/air/criteria.html). These vessels also travel along our populated coasts and waterways. Most have, at best, very modest air pollution controls and many have no controls at all, emitting pollutants at levels (measured in grams per horsepower-hour) typical of highway trucks built before the 1980s. Furthermore, these emissions of particulate matter (PM), sulfur oxides (SOx), hydrocarbons, and NOx can degrade air quality for people living hundreds of miles downwind. We have estimated that in 2001 marine diesel engines with per-cylinder displacement of 30 liters or more (a group roughly corresponding to the engines covered by the new IMO standards) contributed 6% of the NOx coming from all mobile sources in the U.S., as well as 10% of the P
