*EPF407 08/17/00
Text: Report Says Climate Change May Cause Increase in Pollen
(Suspected to be troubling consequence of high carbon dioxide levels) (490)

The U.S. Department of Agriculture reports that higher carbon dioxide levels associated with global warming over the past 50 years may have doubled the amount of pollen that ragweed produces.

According to a August 15 press release, scientific studies have shown that pollen production in a laboratory setting rose almost 400 percent -- which coincided with a 200 percent increase in the amount of carbon dioxide. Another doubling of ragweed pollen is expected to occur by the end of this century. Ragweed pollen is one of the most common allergens in the United States.

Following is the text of press release:

(begin text)

Press Release
August 15, 2000
U.S. Department of Agriculture

GLOBAL WARMING'S HIGH CARBON DIOXIDE LEVELS MAY EXACERBATE RAGWEED ALLERGIES

WASHINGTON, August 15, 2000 -- The U.S. Department of Agriculture released research results today indicating higher carbon dioxide (CO2) levels associated with global warming may have doubled the amount of pollen that ragweed produces -- mostly over the past four or five decades. Another doubling could occur by the end of this century.

"This research may help us better understand the troubling impact of high carbon dioxide levels on our environment and our health," said Agriculture Secretary Dan Glickman.

In scientific studies, pollen production rose almost 400% with a 200% increase in the amount of CO2. Findings show that high CO2 levels have increased the potential production of ragweed pollen and may produce pollen earlier. The ragweed pollen season is now underway.

Lewis H. Ziska, a plant physiologist with USDA's Agricultural Research Service, did the pollen counts on ragweed grown in indoor chambers at various levels of atmospheric CO2 from about the turn-of-the-century levels of 280 parts per million (ppm) to today's levels of 370 ppm to future predicted levels of 600 ppm. Pollen production went from 5.5 grams to 10 grams to 20 grams as CO2 moved through these three levels.

This past spring, Ziska moved the experiments outside, growing ragweed at three locations in the Baltimore, Md.(Maryland), area chosen for their range in temperatures: Baltimore, typical of urban areas thought to be both heat islands and zones of high CO2 concentrations; a suburb; and a rural area.

Ziska, conducting his research in collaboration with Johns Hopkins University School of Public Health, Towson University and Multidata Corporation, says this ongoing experiment should show how global warming and higher CO2 levels might already be increasing ragweed pollen counts, especially in cities. Although less ragweed grows in cities, exposure to air pollutants such as ground-level ozone can make people more sensitive to ragweed pollen.

Scientific contact: Lewis H. Ziska, ARS Climate Stress Laboratory, Beltsville, Md., phone (301) 504-6639, fax (301) 504-6626, [email protected]

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(Distributed by the Office of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)
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