Dust Storms Overseas Carry Contaminants To U.S.

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Dust Storms Overseas Carry Contaminants to U.S.

Scientists Study Whether Diseases Are Also Transported

 

By Doug Struck

Washington Post Staff Writer

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.

 

Traveling for a week over the Pacific from the Gobi and Taklimakan

deserts in Asia, clouds carrying hundreds of millions of tons of dust

regularly reach the northwestern United States. From the Sahara and

Sahel deserts in Africa and the East, they roll across the Atlantic

to the Caribbean and reach the southeastern United States in three to

five days.

 

Authorities in Los Angeles estimate that on some days, one-quarter of

the city's smog comes from China.

 

" There is plenty of evidence from space observations of the Northern

Hemisphere that there is a persistent ring of industrial emission

dust and other pollutants in the air. You can actually see this

bathtub ring around the Northern Hemisphere, " said Stanley A. Morain,

who heads the Earth Data Analysis Center at the University of New

Mexico and collaborates with Sprigg.

 

" If something breaks out, it can move very quickly into other areas, "

he said.

 

Dust storms may be increasing as global warming and desertification

expand arid areas. The dust swirls into the atmosphere containing

plant pollens, fungal spores, dried animal feces, minerals, chemicals

from fires and industry, and pesticide residues.

 

Asthma in the Caribbean increased just as an African drought

increased the amount of dust washing over the islands. Asthma has

increased in Barbados 17 times since 1973, when the African drought

began, according to a national study there, and researchers have

documented an increase in pediatric hospital admissions when the dust

storms are worst.

 

Scientists previously had thought bacteria and viruses picked up by

the dust storms would die on long flights, when they are exposed to

ultraviolet radiation and extreme temperatures. But three-inch

African locusts have been found alive in the Caribbean after dust

storms.

 

In the late 1990s, Eugene Shinn, who was studying the widespread die-

off of Caribbean coral reefs for the U.S. Geological Survey in

Florida, began wondering if smaller living organisms came with the

dust. He eventually linked live microbes brought from Africa to sea

fan disease, which was infecting the coral.

 

Shinn enlisted USGS microbiologist Dale Griffin. They and other

colleagues devised a method of collecting air samples, using a

contraption built with a vacuum pump from Home Depot drawing air

through a two-inch round sterile filter.

 

In the first test, collected during a dusty day in 2000 over the

Virgin Islands, Griffin said he thought they might find evidence of

four or five different microorganisms growing colonies on the filter.

Instead, he found 30 colonies, each with billions of cells.

 

" I did not expect that many, " he said. " And we know that whatever

grows on the filter represents only about 1 percent of what's really

there. People just don't think about microorganisms moving around the

atmosphere, at least that far. "

 

Griffin said that " in Florida in the summer, when the dust storms are

pulsing across, if you walk outside and breathe, 50 percent of the

particles you breathe come from Africa, " more than 4,000 miles away.

They contain mold spores and bacteria that increase allergies and

respiratory diseases.

 

Shinn, who is now retired, said that there has not been enough

response to these findings.

 

" No one in authority really wants to hear about this problem, even

when it is known that African dust sporadically exceeds EPA air

standards in places like Miami during the summer months, " Shinn said

in a letter recently. " No government agency wants to face this

problem because no one knows what to do about it.

 

" In my opinion, nothing will change regarding either African or Asian

dust until we have a catastrophe such as a large-scale avian flu,

West Nile virus, or some other deadly outbreak that cannot be

explained away by the usual suspects, " he said. " Meanwhile we will

continue to employ agents to check for fruit in baggage and dirt on

tourists' shoes while hundreds of millions of tons of soil dust

carrying live microbes continue to be transported unchecked overhead. "

 

Unchecked, perhaps, but not unwatched. The early warning system being

devised by Sprigg will track those storms, integrating the data with

weather forecasts, so that local authorities have notice of one to

three days to take precautions. Parts of the system have already been

set up in China and Europe.

 

In addition to medical precautions, police can be warned about

deteriorating driving visibility and airports can plan to reroute

planes, Sprigg said. He said he hopes the next step will be more

aggressive medical research to determine the composition and human

health threats of what is in those dust clouds.

 

" I really see some practical applications here, " he said. " We are

just getting started. "

 

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