Re: PR Scientists in recent years have confirmed that dust plumes

[Guest guest]

http://www.shns.com/shns/g_index2.cfm?action=detail & pk=DUSTGERMS-05-

24-06

Unwelcome microscopic hitchhikers ride trade winds

By LEE BOWMAN

Scripps News Service

24-MAY-06

New research presented Wednesday adds to evidence that desert dust

carried across the Atlantic by trade winds can transport bacteria,

viruses and fungi into the Americas.

Scientists in recent years have confirmed that dust plumes from

northern Africa, worsened by an extended drought in the region,

regularly ride trade winds into the Caribbean and the Gulf of

Mexico, with Florida and the islands of the basin bearing the brunt

of the microscopic particles. A grain of dust is typically less than

2 microns in size, about a hundred times smaller than the diameter

of a human hair.

That means that the tiny particles are easily inhaled, but rarely

breathed out, resulting in the chemicals, organic materials and

microbes attached to them staying put in the lungs.

While earlier studies have focused on samples taken in the Virgin

Islands and Florida, the new study reported before the American

Society for Microbiology in Orlando, Fla., involved dust collected

aboard a research vessel cruising the mid-Atlantic.

Microbiologist Dale Griffith and colleagues tested air samples over

40 days in May and June of 2003 to determine the level of microbes

and to see if they increased with the presence of airborne desert

dust.

" Desert dust storms move an estimated 2.2 billion metric tons (a

metric ton is 2,204 pounds) of soil and dried sediments through the

Earth's atmosphere each year, " said Griffith, who has been studying

microbes in dust plumes for the U.S. Geological Survey lab in St.

sburg, Fla., for the past five years. " Since a gram of desert

soil may contain as many as 1 billion bacterial cells, the presence

of airborne dust should correspond with increased concentrations of

airborne microorganisms. "

Viable bacterial and fungal populations were collected on 24 days.

The three days when the highest populations of microbes were

collected matched up with the two most intense periods of dust

activity, as determined by using satellite measurements and a U.S.

Navy model that analyzes and predicts dust-storm patterns, Griffith

said.

DNA analysis matched two of the microbes exactly to two dust-borne

organisms that had been previously collected from air samples in

Mali in West Africa, whose Sahel region is known for its dust

storms. One of the organisms, known to cause illness in humans, has

also been found in air samples taken in the Virgin Islands when

African desert dust was present.

Further analysis found a number of other bacteria and fungi that can

cause disease in animals and plants, including one that causes

Florida sycamore canker.

The dust storms typically reach heights in excess of 10,000 feet and

take five to seven days to cross the Atlantic. Other researchers

have linked them to problems ranging from coral diseases to an

increase in asthma and other respiratory problems in the populations

of Trinidad and Barbados, and perhaps even red-tide outbreaks in

Florida and other areas along the Atlantic seaboard.

Although the prevailing wind patterns mostly bring the dust to the

tropics, some researchers have traced dust from Africa as far west

as the Rocky Mountains.

Griffith said the trans-Atlantic transport may act to renew

reservoirs of some plant and animal diseases in North America and

could also be the source of new infections.

On the Net: http://coastal.er.usgs.gov

(Contact Lee Bowman at BowmanL(at)SHNS.com. Distributed by Scripps

News Service, http://www.shns.com)