A new study says the world's 106,000 large ships are among the planet's worst air polluters. The study by Carnegie-Mellon University in Pittsburgh found that ships spew 5 percent of the globe's sulfur oxides. Sulfur emissions are an ingredient in acid rain. The study also said that ships pump out 14 percent of the world's nitrogen oxide emissions. Put another way, that's equal to the nitrogen emissions from all the cars, trucks and other vehicles in the United States.
Nitrogen oxide can form ozone, an irritating substance in smog.
Nearly 95 percent of the world's large vessels have diesel engines. Bunkers are fuels leftover from the refining process. It's the fuel nobody wants. Nobody but ship owners. But it's a dirty fuel.