Potentially hazardous bacteria and fungi catch a free ride across the Atlantic, courtesy of North African dust plumes. Government 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 June 14 in the journal 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 region generates clouds of dust. The dust, originating from fine particles in the arid topsoil, is transported into the atmosphere by winds and may be carried more than 10,000 feet high into the atmosphere by easterly trade winds. Typically, it takes 5 to 7 days for the dust clouds to 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 Vir
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Contact: Carolyn Bell
cbell@usgs.gov
703-648-4463
United States Geological Survey
13-Jun-2001