Tainted African Dust Clouds Harm U.S., Caribbean Reefs

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(Related: " Coral Reefs Vanishing Faster Than Rain Forests" [August 7, 2007].)

These contaminants were highest in Mali and lower in the downwind areas of the Americas. Six pesticides were found at each one of the test sites, Garrison said.

"And there's been very, very little work that has been done on the concentrations of any of these pesticides or PCBs [and how] that would impair coral or coral reef organisms," she added.

Andrew Negri, of the Australian Institute of Marine Science in Townsville, co-authored one of the few previous studies on pesticides and coral.

"The pesticides associated with African dust are primarily insecticides. These can affect the coral host directly," Negri said.

"We have found that two of the identified insecticides, chlorpyrifos and endosulfan, can reduce the settlement and attachment of coral larvae to the ocean floor at very low concentrations.

"I would be particularly concerned if storms containing insecticide-contaminated dust were to occur upwind of coral reefs around spawning time," he said.

Winds of Change

Atmospheric systems such as the Africa-Americas pathway have functioned for thousands of years.

A similar system delivers Asian dust to the western United States, where it accounts for up to an estimated 40 percent of local air particles.

In recent times, however, humans have caused some significant changes.

Desertification and changing land-use patterns can put more dust into the air. Industrialization, pesticide use, waste burning, and other practices have produced air pollutants that ride with that dust to far-flung locales.

(Related: "Warming, Disease Causing Major Caribbean Reef Die-Off" [April 6, 2006].)

But the question of just where air "originates" is tricky, experts say. Traceable substances such as pollen can provide clues to where contaminants come from.

But in Garrison's view, mass mixing around the globe means that we all experience a single, large air system.

"I can watch a dust air mass [via] satellite coming out of Africa, across the Caribbean, and into the eastern U.S., and all of a sudden it peters out," she explained.

"But the air mass is still moving with some dust into the northeast[ern] U.S., where it mixes with a pollution cloud. Then it goes over the North Atlantic to Europe, picks up a bit of their pollution cloud, and then goes back to Africa. So where did this stuff come from?"

Garrison believes that while certain contaminants may be linked to specific areas, such as the African pesticides, no one region is entirely to blame for air-quality issues.

"We're all responsible," she said. "We all have to watch what we're putting into the air."

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