April 1, 2005

Expert Finds Dandruff in Air Pollutants

WASHINGTON (AP) -- A researcher has discovered unexpectedly large amounts of dandruff and other flaking skin, fur, pollen and similar materials in air pollutants known as aerosols.

Aerosols, tiny particles in the air, are widely studied because they are an important factor in regulating climate, variously absorbing heat to warm the air and reflecting sunlight to cool it. They are also important in forming rain and snow.

But the amount of cellular material - bacteria, plant fragments, spores, fungi and so forth - had been thought to be only a small proportion compared with mineral dusts, clay and sea salt.

Now, Ruprecht Jaenicke of the Institute for Atmospheric Physics at Mainz University in Germany has studied air samples and discovered that biological materials can range up to 25 percent of aerosols in some areas, and as high as 40 percent in others.

His findings are reported in Friday's issue of the journal Science.

The source of many aerosols has been unexplained and this could provide the answer, Jaenicke said.

Jaenicke reported that the percentage of biological materials in aerosol pollution topped 40 percent in Mainz in September and 30 percent in October. And a study at Lake Baikal, Russia, showed more than 30 percent in September.

He said he did similar studies of the air over ocean environments, on mountains and in ice cores. There was no strong annual cycle, he said, although pollen was more abundant in spring while decaying cellular matter was more common in fall and winter.

He estimated that the amount of biological particles in the air, worldwide, annually is 1,000 teragrams. A teragram is somewhat more than a million tons.

By comparison, the Intergovernmental Panel on Climate Change, established by the World Meteorological Organization and the U.N. Environmental Program, estimated biological particles at 56 teragrams, compared with 3,300 teragrams of sea salt and 2,000 teragrams of mineral dust.

The new finding means researchers should take biological materials seriously in climate modeling, in cloud physics and in hygienic questions such as allergies, Jaenicke said.

"Don't regard that as a minor contribution," he said.

The implications for the global climate are unclear, said Murray V. Johnston, a chemistry professor at the University of Delaware.

"The number concentrations of (biological particles) reported here are much higher than previously thought and merit follow-up research," said Johnston, who did not participate in Jaenicke's research.

James J. Schwab, an atmospheric chemistry research professor at the State University of New York at Albany, isn't so sure Jaenicke's figures are correct.

"He may very well be right. His paper does not convince me that I should believe his estimate, however. He needs to present a more detailed and convincing argument first," said Schwab.

If Jaenicke's estimate is right, Schwab said, "It will have small but important effects on global climate change. It will have a bigger effect on air pollution and air quality for regions of the country and the globe that are out of compliance with air quality standards."

The research was funded by the German Science Foundation.


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Mainz University

Science: http://www.sciencemag.org/