- WASHINGTON (AP) - Dust from
the African deserts is bringing germs and fungi across the Atlantic. Researchers
who tested samples of the dust collected last summer warn that "pathogenic
microbes associated with dust clouds may pose a risk to ecosystem and human
health."
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- "You can transport a lot of stuff through the atmosphere."
- Joseph M. Prospero
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- Cooperative Institute for Marine and Atmospheric Studies
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- While windborne transport of African dust to North and
South America long has been known, scientists thought few microbes would
survive the trip because of exposure to ultraviolet radiation in the atmosphere.
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- Researchers now believe the dust clouds themselves block
enough light to protect bacteria and other microbes during the five- to
seven-day journey.
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- The findings of the group, led by Dale W. Griffin of
the U.S. Geological Survey, are reported in the June issue of the journal
Aerobiologia.
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- About 10 percent of the microbes identified were "opportunistic
pathogens," Griffin said in a telephone interview.
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- They are organisms that do not cause disease in healthy
humans but could affect someone with a compromised immune system, such
as AIDS patients, the very old or young, and transplant or cancer patients
with suppressed immune systems, he said.
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- "For most healthy individuals, I don't think it's
a problem," said Griffin, a public health and environmental microbiologist.
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- PLANTS AFFECTED
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- In addition, he said, 25 percent of the microbes were
known plant pathogens that affect elm trees or such crops as peaches, cotton
and rice.
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- Joseph M. Prospero, director of the Cooperative Institute
for Marine and Atmospheric Studies at the University of Miami, said his
research in Barbados also had seen fungi and bacteria associated with African
dust.
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- He said there had been a "very clear association"
of sharply increased incidence of viable fungi and bacteria in African
dust arrivals.
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- "There's no question you can transport a lot of
stuff through the atmosphere," Prospero said in a telephone interview.
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- When the trajectories of the dust are traced backward,
the dust clouds with the bacteria come only from Africa, while dust arriving
from Europe or North America does not include bacteria, said Prospero,
who was not associated with Griffin's team.
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- The movement of African dust across the ocean has been
increasing in recent years with the growing drought in Africa. It peaks
in June through October. Large dust arrivals have been measured over roughly
30 percent of the United States, with about half the volume settling on
Florida.
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- "The high concentration of dust impacting the Caribbean
may pose a significant public health threat, particularly as it pertains
to respiratory disease," the researchers wrote.
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- GROWING SENSITIVITY
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- They noted that once a person was sensitized to fungi,
exposure to even small amounts could trigger an allergic reaction.
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- They cited a 17-fold increase in the prevalence of asthma
in Barbados from 1973 to 1996. "This increase corresponds to the observed
increase in African dust flux impacting Barbados," they said.
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- The dust also has been implicated in coral reef damage
in the Caribbean.
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- Griffin collected dust samples in St. John, U.S. Virgin
Islands, and sent them for testing to Virginia Harrison at the agency's
laboratory in St. Petersburg, Fla.
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- Using NASA satellites to track the African dust clouds,
they were able to take air samples both on clear days and on days with
dust plumes affecting the region.
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- On the dusty days, there averaged 158 bacteria, 213 viruses
and 201 fluorescent bacteria in about a quart of air. By comparison, the
same volume of air on a clear day averaged 18 bacteria, 18 viruses and
none of the fluorescent bacteria.
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- Other members of the research team included Jay R. Herman
of NASA and Eugene A. Shinn of the Geological Survey.
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- © 2001 Associated Press. All rights reserved.
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