photo: Daniel Ramirez via flickr
Commercial shipping (which includes much more than container ships, but also cruise ships, ferries, tankers, etc.) has a dirty little secret: Its effect on air pollution. A new study by the National Oceanic and Atmospheric Administration and the University of Colorado, Boulder shows that the amount of particulate emissions caused by commercial shipping is equal to about half of all the world's cars:The study's authors say that this is the first global estimate of air particle pollution based on direct measurement of emissions. That estimate: Globally, ships emit 2.2 million pounds of particle pollution into the air every year.
"Since more that 70% of shipping traffic takes place within 250 miles of the coastline, this is a significant health concern for coastal communities," Daniel Lack, lead author of the study pointed out.
Half of Ships' Emissions Not Covered Under Existing Regulations
Here's why ships are such powerful polluters: In addition to organic pollutants and sooty, black carbon, which make up half of the emissions and are not covered under existing regulation,
Ships emit sulfates, the same particles associated with diesel-engine cars and trucks which motivated improvements in on-road vehicle fuel standards. Sulfate emissions from ships vary with the concentration of sulfur in ship fuel, the authors found. Globally, fuel sulfur content is regulated under the International Convention for the Prevention of Pollution from Ships. As a result, some ships use "cleaner," low-sulfur fuels, while others continue to use the high-sulfur counterparts.
The thing though with these low-sulfur fuels, the study also found, is that while they do reduce total particle emissions, the particles that do remain tend to remain in the air longer... Which is where they post a threat to human health and affect climate.
Particle Pollution's Cooling Effect...Plus Death
Interestingly, this particle pollution has the opposite effect on the climate as does the ship's carbon emissions: The particles have a cooling effect that is at least five times greater than the warming effect of the CO2 emissions. Too bad this particulate emission is also linked to premature deaths among coastal populations...