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Study: Global shipping pollution ain't pretty

Researchers estimate worldwide commercial shipping puts out almost half as much particle pollution as cars.

Tugboat in the Panama Canal locks Urs Hauenstein/

Cars might get a lot of the press surrounding air pollution, but commercial shipping puts out a hefty amount of pollution as well. Cargo ships, tankers, and cruise ships spew almost half as much particle pollution as the world's cars, according to a study published Wednesday by the American Geophysical Union.

Researchers analyzed the exhaust of more than 200 commercial ships in the Gulf of Mexico and shipping channels near Galveston, Texas, in the summer of 2006. Specifically, researchers focused on sulfates, a kind of particulate pollution produced by diesel-fueled cars and trucks, but which is also found in ship exhaust.

Ships likely release 0.9 teragrams (about 2.2 million pounds) of particulate pollution globally each year, according to the study, which is the first to give an estimate for particle pollution emissions produced by the world's shipping fleets.

The effects of this pollution can be felt more acutely by people who live along coastlines, according to Daniel Lack, a National Oceanic and Atmospheric Administration researcher. Lack, who was the study's lead author, notes that more than 70 percent of shipping traffic takes place within 250 miles of the coastline. Earlier research by another of the study's authors found a correlation between particle pollution and premature deaths in coastal populations.

Sulfates from shipping are capped under global regulations. But the AGU's statement notes that other elements of ship exhaust, including soot, or black carbon, are not. A joint study by NOAA and the University of Colorado in 2008 found tugboats to be major culprits in that type of pollution. Shipping exhaust also contributes almost 30 percent of smog-forming nitrogen oxide gases, according to the AGU.

The study was published Wednesday in the Journal of Geophysical Research, an AGU publication.