Beware distant dust

Dust storms in Africa, wild fires in Mexico, and ozone from Japanese factories can all have a negative impact on air quality and human health in other countries, including the United States and Europe, says a new report from the National Research Council.

Smokestack from a WWII production plant Image: Wikipedia, via the Library of Congress

Wind carries pollution great distances all the time, but scientists are best able to observe the phenomenon during major weather or pollution events, including dust storms or smoke plumes visible by satellite. Although scientists do not yet have the data to quantify the impact of these events, mathematical models and correlational studies help them identify some areas of concern.

"The deadliest air pollutant that we are dealing with in this report are the fine particles," atmospheric chemist Charles Kolb, lead author and CEO of Aerodyne Research in Boston, told The Scientist.

Currently, road dust is the second leading cause of particle emissions, following fires. Kolb said that the best estimate of the number of premature deaths attributable to exposure to particulates (some of which originate in other countries) comes from Europe, with about 348,000 deaths in 25 countries. "The heavy loads of fine particles we find in many large urban areas exacerbate heart problems and also cause deaths from lung cancer and emphysema."

As industrialized nations tamp down on their own air quality problems, Kolb said, they will have to cope with trans-oceanic imports drifting in from developing nations.

But while the report focuses on industrial and agricultural sources of pollution, such as mercury and pesticides, it also singles out dust storms as a natural factor that may double or triple its impact with climate change.

However, it gives short shrift to the theory that airborne pathogens in this dust may be at the root of some of the deadly conditions. "There are pathogens associated with the dust that comes from Asia and Africa," Kolb said, "but the deaths are attributed to chronic conditions, not specific diseases. The added pollution pushes people over the edge."

This interpretation does not sit well with Dale Griffin, microbiologist from the United States Geologic Survey in Tallahassee Florida, featured in last year's feature about the deadly toll of airborne microbes. "I think microorganisms cause disease," he said.

"Every gram of topsoil or desert soil that goes airborne contains 1 billion bacteria per gram," he added. "Twenty to 30 percent of organisms are pathogenic to some type of organisms. The risk of microorganisms is there and that's an important issue."

The Environmental Protection Agency requested the new report as part of its obligations related to a 1979 Convention on Long-Range Transboundary Air Pollution, signed by the United States, Canada, and countries in Europe, in the aftermath of the discovery of the causes of acid rain.


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