African dust brings nutrients—and toxins

For centuries winds have carried dust from Africa and deposited it on islands in the Caribbean and locations in Florida and South America. The dust provides essential nutrients to the upper canopy of the Amazon rain forest and, in the Bahamas, contributes to the formation of red soils known as pineapple loam.

As early as 1846, however, Charles Darwin was complaining about the pernicious effects of African dust as he traveled through the Canary Islands. In recent years the dust has carried traces of fertilizers, pesticides, mercury, arsenic, bacteria and a fungus called Aspergillus that has devastated sea fans on Caribbean coral reefs.

According to Eugene A. Shinn, Ph.D., a geologist with the U.S. Geological Survey in St. Petersburg, Fla., the dust also has implications for human health. “It causes lung infections,” Shinn told students at the School of Forestry & Environmental Studies in November. He also believes African dust is linked to increases in asthma throughout the Caribbean.

Since the 1970s deforestation and drought in Africa have caused huge dust storms. When they reached the Caribbean, the effects were obvious. “In San Juan, Puerto Rico, people could feel it in their chests. They had headaches,” Shinn said.

Shinn is working with microbiologists and physicians to study the problem, but as he cautioned at the start of his lecture, “This is a bad-news/bad-news story.”