African Dust Storms
This is the VOA Special English ENVIRONMENT REPORT.
Researchers in the United States say dust clouds from dry African deserts may be a threat to the environment and human health. They say the dust may contain many small organisms that could be dangerous to some people.
Each year, huge dust storms form in the Sahara and the Sahel deserts of northern Africa. Winds carry the dust across the Atlantic Ocean. The movement of dust across the Atlantic Ocean has been increasing in recent years because of longer periods without rain in Africa.
From February to April, the dust settles in South America. From June to October, the winds change and transport the dust to North America, Central America and the Caribbean. The dust clouds travel several thousand meters above sea level. It takes five to seven days for the dust to cross the Atlantic Ocean.
Researchers have long known that the dust clouds could travel long distances. But they thought few microorganisms could survive the trip because of damaging ultraviolet radiation from the sun. Researchers now believe that the dust clouds block enough of the light to protect viruses, bacteria and fungi in the dust.
Researchers say these microorganisms may be a health risk to some people. About half of the bacteria and fungi that survive the trip from Africa are known to cause disease in people, animals or plants.
More than half of the dust that reaches the United States settles in the state of Florida. For many years, it has caused the skies there to turn red. Now researchers say there may be a link between the dust storms and increased health risks in Florida. They believe the dust causes higher rates of asthma, allergies and other breathing problems in people there. The dust also has been linked to a large increase in lung problems in at least one Caribbean nation.
Last year, American scientists published a study showing that the African dust is causing coral reef damage in the Caribbean. They identified organisms in the dust particles that cause coral diseases.
Scientists at the United States Geological Survey reported the latest findings. They used satellites from NASA, the United States space agency, to carry out their work.
This VOA Special English ENVIRONMENT REPORT was written by Cynthia Kirk.