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updated 3/31/2005 2:17:12 PM ET 2005-03-31T19:17:12

Many types of emissions have been tied to climate change and air pollution, but a new study has come up with a novel suspect: dandruff.

German researchers discovered unexpectedly large amounts of dandruff and other flaking skin, fur, pollen and similar materials known as biological aerosols. This cellular material had been thought to be only a small proportion of all aerosols, which include mineral dusts, clay and sea salt.

Ruprecht Jaenicke, of the Institute for Atmospheric Physics at Mainz University in Germany, reported a team had studied air samples and discovered that biological aerosols make up 25 percent of all aerosols on average, and as much as 80 percent in some areas and at certain times.

The findings are reported in Friday’s issue of the journal Science.

Samples taken worldwide
Aerosols, tiny particles in the air, are the right size and shape to act as nuclei for ice crystals, which in turn form clouds and rain, and thus could potentially affect weather and climate.

Jaenicke noted that the source of many aerosols has been unexplained and that this study could provide the answer.

The percentage of biological materials in aerosol pollution topped 40 percent in Mainz in September and 30 percent in October, the report said.

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.

Models underestimate?
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. Environment 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.

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

“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.

More studies urged
James 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.”

Jaenicke’s team was unable to say how much of this biological dust is actually dandruff, but presumably the largest portion would be from cellular material like pollen and plant fragments.

He urged other climate scientists to further study the components of aerosols so they can make more accurate models for predicting weather and climate change.

The Associated Press and Reuters contributed to this report.


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