Commercial ships spew half as much pollution as world’s cars

February 27th, 2009 - 5:06 pm ICT by IANS  

Washington, Feb 27 (IANS) Commercial ships account for almost half as much particulate pollution as the total amount released by cars, according to a new study.
The study estimate that worldwide, ships emit about a million kilos of particulate pollution each year. Shipping also contributes almost 30 percent of smog-forming nitrogen oxide gases.

“Since more than 70 percent of shipping traffic takes place within 250 miles of the coastline, this is a significant health concern for coastal communities,” said study co-author Daniel Lack, a researcher at the National Oceanic and Atmospheric Administration (NOAA)’s Earth System Research Lab in Boulder, Colorado.

Earlier research by one of the study authors, James Corbett, of the University of Delaware, in Newark, linked particulate pollution to premature deaths among coastal populations.

Commercial ships emit both particulate pollution and carbon dioxide. Carbon dioxide from ships makes up roughly three percent of all human-caused emissions of the gas.

But particulate pollution and carbon dioxide have opposite effects on climate. The particles have a global cooling effect at least five times greater than the global warming effect from ships’ carbon dioxide emissions, Lack said.

During the summer of 2006, Lack and colleagues, aboard the NOAA ship Ronald H. Brown, analysed the exhaust from over 200 commercial vessels, including cargo ships, tankers and cruise ships, in the Gulf of Mexico, Galveston Bay, and the Houston Ship Channel.

They also examined the chemistry of particles in ship exhaust to understand what makes ships such hefty polluters.

Ships emit the same polluting particles associated with diesel-engine cars and trucks that prompted improvements in on-road vehicle fuel standards. Sulphate emissions from ships vary with the concentration of sulphur in ship fuel, the authors found.

Globally, fuel sulphur content is capped under the International Convention for the Prevention of Pollution from Ships. As a result of the cap, some ships use “cleaner” low-sulphur fuels, while others continue to use the high-sulphur counterparts, said a NOAA press release.

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