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Dust From Africa*

African dust storms send germs to America

June 18, 2001 Posted: 8:17 AM EDT (1217 GMT)

By Richard Stenger


(CNN) -- Besides painting American sunsets red when they cross over the Atlantic, colossal Saharan dust storms bring loads of potentially dangerous microorganisms to the New World, according to scientists.

Loads of bacteria and fungi, some of which could cause disease and respiratory problems, hitch rides on dust storm plumes from Northern Africa that blow westward for thousands of miles, according to researchers.

As the dust grains and their tiny stowaways settle down in the Western Atlantic, they could pose health risks to people in Florida and the Caribbean, according to scientists with the U.S. Geological Survey and NASA.

The seasonal African storms, which peak in July, transport millions of tons of fine-grained dust across the Atlantic each year, contributing to a reddish haze over much of the U.S. Southeast.

Besides painting the air red, the fine-grained dust particles serve nicely as air carriers for the upwardly mobile microbes, which ride on easterly trade winds more than 10,000 feet above sea level.

"Microbes in the cracks and crevasses of dust particles may be shielded from ultraviolet rays," said Dale Griffin, co-author of a report in the June 14 edition of the journal Aerobiologia, in a statement.

"Additionally, when dust clouds move over open water in lower latitudes, the moderate temperatures and high humidity are known to enhance microbial survival."

The dust events are cyclical. From February to April, the waves of particles descend on the Amazon Basin. The winds then shift and from June to October the Caribbean and North and Central America bear the brunt of the storms, which take 5 to 7 days to make the transatlantic trip.

Griffin and colleagues tracked the storms using a NASA satellite that monitors world ozone levels. They compared the results with airborne pollutants in the Caribbean and found corresponding high levels of microbes.

Florida receives more than half of all microbe-laden Africa dust in the United States. During major episodes, there could be a correlation with increased health risks in the state, the scientists cautioned.

Besides microbe and fungi passengers, the dust grains themselves are known to cause respiratory and allergic reactions. One study in the Caribbean revealed a 17-fold increase in asthma attacks during an increased period of dust transport.

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