Dust Storms Overseas Carry Contaminants to U.S.
Wednesday, February 6, 2008
Seventy-five years ago, aviator Charles Lindbergh turned the controls of his pontoon plane over to his co-pilot, wife Anne Morrow Lindbergh, while flying above Iceland. He thrust a makeshift metal arm holding a sticky glass plate from the cockpit. He wanted to see if the winds high aloft the Earth were as clean as they seemed.
They were not.
Now, with NASA satellites and sampling by researchers around the world, scientists know that great billowing clouds of dust waft over the oceans in the upper atmosphere, arriving in North America from deserts in Africa and Asia.
Researchers have also found that the dust clouds contain not only harmful minerals and industrial pollutants, but also living organisms: bacteria, fungus and viruses that may transmit diseases to humans. Some say an alarming increase in asthma in children in the Caribbean is the consequence of dust blown from Africa, and predict they will find similar connections in the Southeast and Northwest United States.
Scientists are beginning to look at these dust clouds as possible suspects in transcontinental movement of diseases such as influenza and SARS in humans, or foot-and-mouth disease in livestock. Until recently, epidemiologists had looked at people, animals and products as carriers of the diseases.
"We are just beginning to accumulate the evidence of airborne dust implications on human health," said William A. Sprigg, a climate expert at the University of Arizona. "Until now, it's been like the tree falling in the forest. Nobody heard, so nobody knew it was there."
The World Meteorological Organization, a science arm of the United Nations, is alarmed enough to set up a global warning system to track the moving clouds of dust and to alert those in the path. Sprigg is heading the project.
He foresees a system soon in which forecasters can predict "down to the Zip code" the arrival of dust clouds. That forecast could prompt schools and nursing homes to keep their wards inside, and help public health doctors predict a surge of respiratory complaints.
Analysis of soil samples has long shown that minerals picked up from barren deserts reach distant shores, for good or bad. The Amazon rain forest in South America, for example, gets phosphate nutrients from dust blown in from northern Africa's Sahara Desert.
Industrial development has added heavy metals and toxic chemicals to that airborne mix. Korea and Japan periodically chafe as storms of "Yellow Dust" wash over from China, bringing a caustic mix of sand and industrial pollutants.
Even natural minerals can be harmful to humans, and dust-borne particles have been linked to annual meningitis outbreaks in Africa and silicosis lung disease in Kazakhstan and North Africa. The Dust Bowl storms of the 1930s in the United States brought graphic descriptions of choking sediment getting into the lungs of people and felling livestock.
But the advent of satellite images gave scientists a sobering look at how even faraway storms can reach us.