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MICROBES AND
THE DUST THEY RIDE IN ON POSE POTENTIAL HEALTH RISKS
Potentially hazardous bacteria
and fungi catch a free ride across the Atlantic, courtesy of
North African dust plumes. NASA-funded researchers who made
the discovery believe the stowaway microbes might pose a
health risk to people in the western Atlantic region.
Dale Griffin, Virginia
Garrison, and Eugene Shinn of the U.S. Geological Survey (USGS)
and Jay Herman of NASA’s Goddard Space Flight Center outline
their findings in a paper titled "African Desert Dust in
the Caribbean Atmosphere: Microbiology and Public
Health." The paper will be published on June 14 in the
journal of Aerobiologia.
"The National
Institute of Health’s National Institute of Allergy and
Infectious Diseases identifies airborne dust as the primary
source of allergic stress worldwide," stated Shinn.
"The identification of microbes in transported dust is
important as they may be a source of respiratory stress and
disease above and beyond that caused by exposure to
particulate matter."
African dust has produced
red-tinged sunsets in south Florida for years. The dust comes
every year during northern Africa’s dry season, when storm
activity in the Sahara Desert and Sahel generate clouds of
dust. The dust originating from fine particles in the arid
topsoil is transported into the atmosphere by winds and may be
carried in excess of 10,000 feet high into the atmosphere by
easterly trade winds. Typically, it takes 5 to 7 days for the
dust clouds cross the Atlantic Ocean and reach the Caribbean
and Americas.
"The dust events are
cyclical," Griffin said. "Studies by other
researchers have shown that from February to April, the winds
bring an estimated 280,000 tons per event to 13 million tons
per year to the Northeastern Amazon Basin. From June to
October the winds shift and typically bring dust to north and
Central America and the Caribbean."
During the peak of the dust
season in July 2000, Garrison collected samples of airborne
pollutants and dust daily on the island of St. John in the
Virgin Islands and sent them to the USGS laboratory in St.
Petersburg, Florida, for microbial analysis by Griffin. He
compared his results with satellite observations tracking dust
clouds from North Africa. The air samples with high levels of
microbes were collected on the days that NASA’s Total Ozone
Mapping Spectrometer (TOMS) satellite instrument observed the
African dust sweeping into the region, indicating that the
microbes had been transported from Africa.
"In the week it
takes for North African dust to cross the Atlantic some of the
microbes die because of exposure to ultraviolet (UV) rays of
the sun," said Griffin. "However, microbes in the
cracks and crevasses of dust particles may be shielded from
UV. We also believe that the upper altitudes of the dust
clouds deflect harmful UV rays, shielding microbes at lower
altitudes as they are transported across the Atlantic Ocean.
Additionally, when dust clouds move over open water in
lower latitudes, the moderate temperatures and high humidity
are known to enhance microbial survival."
Florida receives more than 50
percent of all microbe-laden African dust that reaches the
United States. Over the last 25 years, dust quantities
reaching Miami have increased during periods of African
drought. The U.S. Environmental Protection Agency says these
tiny dust particles can penetrate deep into your airways and
react with lung tissue. "During major dust episodes
reaching Florida, there could be a correlation with increased
respiratory problems," Herman said.
In addition to the dust itself,
even small concentrations of fungal spores can trigger
allergic reactions. A study by M.E. Howitt of the Queen
Elizabeth Hospital in Barbados documented a
17-fold increase in asthma attacks in Barbados between 1973
and 1996, corresponding with the increase in African dust
transport to the region.
Fungi and bacteria that
survive the trans-Atlantic journey in dust include bacterial
or fungal cultures that do not produce disease mixed with
species that do produce disease in both humans and plants. A
fungus, which has been isolated in African dust, Aspergillus
sydowii, has been determined to cause Sea Fan disease in
coral reefs throughout the Caribbean. Desert dust exposure has
also been identified as a source of terrestrial disease
outbreaks including: Aspergillosis in animals, and
Coccidioidomycosis.
Aspergillosis is a mold-like
infection of the lungs that affects animals and birds.
Coccidioidomycosis presents a more direct hazard to humans and
has affected inhabitants of the arid southwestern U.S.
Coccidioidomycosis is caused by Coccidioides immitis, which
causes pulmonary illnesses in humans that range from
flu-like illnesses to pneumonia.
Since 1979 TOMS has been used
to identify atmospheric conditions such as dust events and
other aerosols. Such satellite images could enable scientists
to notify localities of approaching African dust clouds so
that precautions can be taken for those with respiratory
problems.
This research was funded by
NASA’s Earth Science Enterprise Environment and Health
Program at Goddard Space Flight Center, a cooperative program
with local, state, federal, and international institutions.
The initiative uses NASA remote-sensing satellites and other
data to investigate the connections between the world’s
environmental conditions and human health. The program hopes
to generate information that may be used in the future to help
guide public policy and respond to health issues and potential
disease outbreaks.
More information about this
research and images can be found at: http://coastal.er.usgs.gov/african_dust
The accompanying video-file
will air on NASA-TV and can be seen on Direct TV or the Dish
Network. The video files air at noon, 3pm, 6pm, and 9pm
(Eastern Time). On the C-band satellite, NASA-TV coordinates
are GE-2, transponder 9C, C-Band, 85 degrees W longitude,
vertical polarization, 3880.0 Mhtz.
For more information contact:
Deanna Kekesi, Associate NASA-TV Producer, kekesi@pop100.gsfc.nasa.gov,
Tel. 1-301-286-0041.
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