SAN
JUAN, Puerto Rico, Friday August 30, 2013 – Clouds of African dust have been
sprinkling their contents across the Caribbean for as long as there's been sand
in the Sahara Desert. The phenomenon is nevertheless attracting increasing
attention from regional scientists who believe that the clouds have grown, even
if there's no global consensus on the issue.
Recently,
an unusually large cloud dusted the Eastern Caribbean, generating hazy skies
and vivid sunsets before drifting over Mexico's Yucatan Peninsula and moving on
to be detected as far away as Wyoming in the United States.
Satellite
images from NASA show these huge, smoky clouds wafting westward from Africa and
blanketing hundreds of square miles.
Although
the microscopic dust particles sent aloft by African sandstorms have hitherto
been accorded little more than moderate interest, experts are now saying that
the particulate matter may be cause for health concerns and merit more study to
understand their potential impact.
According
to Braulio Jimenez-Velez, a specialist in molecular and environmental toxicology
at the University of Puerto Rico at Mayaguez, "It is a matter of great
magnitude, interest and importance for health."
So
far this year, Sahara dust has prompted two health alerts in Puerto Rico for
asthma sufferers and people with allergies. The Dominican Republic also issued
a warning.
Many
Caribbean territories, including Puerto Rico, have high asthma rates, but no
direct link has been established between African dust and higher rates of
asthma or lung cancer.
Over
time, human activity has changed the composition of the clouds, with scientists
saying that they now contain trace amounts of metals, microorganisms, bacteria,
spores, pesticides and faecal matter, although no evidence exists that the
quantities are sufficient to pose a threat.
African
dust sampled in Barbados also had elevated levels of arsenic and cadmium,
according to Joseph M. Prospero, professor emeritus of marine and atmospheric
chemistry at the University of Miami.
"The
specific impact on health is not known here or anywhere else. It has been
extremely difficult to link specific particle composition to health
effects," said Prospero, who is lead author of a paper on the dust to be
published in September by the bulletin of the American Meteorological Society.
"So
it cannot be said what effect all this dust has, but there is reason for some
concern," the expert added.
Eugenio
Mojena of Cuba's Institute of Meteorology said the particles are believed to
originate in the semi-arid Sahel region south of the Sahara Desert, where farmers
raise livestock and employ chemical fertilizers and pesticides.
Experts
also worry that chemicals in the clouds may pose a threat to coral, although
the theory is still a subject of debate.
The
dust clouds can also complicate air traffic by reducing visibility to less than
3 miles, said Jason Dunion, a researcher at the National Oceanic and
Atmospheric Administration (NOAA).
On
a more positive note, the dust-laden clouds may inhibit the formation of
hurricanes and other tropical weather systems in the Caribbean.
According
to Prospero, lower rainfall in West Africa presumably causes more dust, which
reduces sunlight, lowers water temperatures and cuts evaporation, all factors
in cyclonic formation
SOURCE:
http://www.caribbean360.com/
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