Skip to: Content
Skip to: Site Navigation
Skip to: Search

Nearly half of North America's aerosols come from Asia, Sahara

Nearly half of the tiny particles found high in the atmosphere over North America come from foreign lands, with 88 percent of that coming from Asia.

By Wynne ParryLiveScience / August 3, 2012

Airborne particles and droplets called aerosols can make for colorful sunsets. Above, a sunset during an aerosol-ejecting Colorado wildfire in June 2012.

Brian Emory


Nearly half of the tiny droplets and particles suspended high in the atmosphere over North America comes from other continents, an examination of satellite data reveals.

Skip to next paragraph

"That is a big number: half. I wasn’t expecting anything like that," study researcher Lorraine Remer of the University of Maryland says in a video released in conjunction with the new study on aerosols.

Specifically, the research team found that 70.5 million tons (64 teragrams) of foreign aerosols — which include naturally occurring dust as well as pollution — arrive over North America every year. Meanwhile, people and natural processes in North America produce 76.1 million tons (69 teragrams) of aerosols on their own, or 52 percent of the total.

There is another surprise as well: The research team, led by Hongbin Yu of the University of Maryland and NASA’s Goddard Space Flight Center, found that most of the aerosols are naturally occurring dust, not man-made pollution such as sulfates produced by the combustion of fossil fuel.

In fact, 88 percent of the foreign aerosols is dust carried across the Pacific Ocean. The remainder, according to the researchers, is either Saharan dust that traveled across the Atlantic Ocean or man-made aerosols, mostly from Asia but some from Europe. [Earth Quiz: Mysteries of the Blue Marble]

If you are a resident of North America, it’s unlikely you are breathing much of this stuff, because it arrives high in the atmosphere, not low over the ground.

As dust travels east across the Pacific, the lowest-flying particles fall out. As a result, the elevated levels of dust show up between 1.2 and 3.7 miles (2 to 6 kilometers) above the water by the time the dust has reached the northeastern Pacific, the team writes in the Aug. 3 issue of the journal Science.

This means North Americans still have control over the air they breathe, Remer says.

"As it turns out, we should still keep focused on our own pollution in order to keep our air healthy, because the particles that come from other places come high," she says in the video released by the American Association for the Advancement of Science, which publishes Science.

Aerosols, particularly pollutants, have a cooling effect by blocking the sun’s energy. The researchers write that imported aerosols are likely to have additional effects on North American climate, or instance, by altering cloud formation and precipitation.

Follow Wynne Parry on Twitter @Wynne_ParryorLiveScience @livescience. We're also on Facebook & Google+.

Copyright 2012 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Read Comments

View reader comments | Comment on this story

  • Weekly review of global news and ideas
  • Balanced, insightful and trustworthy
  • Subscribe in print or digital

Special Offer


Doing Good


What happens when ordinary people decide to pay it forward? Extraordinary change...

Danny Bent poses at the starting line of the Boston Marathon in Hopkinton, Mass.

After the Boston Marathon bombings, Danny Bent took on a cross-country challenge

The athlete-adventurer co-founded a relay run called One Run for Boston that started in Los Angeles and ended at the marathon finish line to raise funds for victims.

Become a fan! Follow us! Google+ YouTube See our feeds!