Research Links Allergies to Climate Change

Sept. 8, 2008— -- Ragweed season is at its peak, bringing bad news for the more than 50 million Americans who suffer from allergies to the plant.

Three out of four Americans who have allergies are allergic to ragweed. A single plant produces hundreds of millions of pollen grains that cause hay fever. Due to the grains' light weight, they can travel up to 400 miles with the breeze.

Dr. Clifford Bassett, allergy specialist at Long Island College Hospital and the American Academy of Allergy Asthma & Immunology, says ragweed allergies affect more and more people; he says that over the past three years, he has seen about 50 percent more new allergy patients.

"We're really looking at an epidemic of new patients, children and adults alike, with allergies, as well as asthma coming in for the very first time," Bassett told ABC News.

Some scientists believe they can explain why allergy season is the worst yet: climate change.

They say the planet is getting warmer, which is making weeds grow faster, causing them to produce more pollen. The increased pollen production has made allergies and asthma worse across the country.

Researchers from the American Academy of Allergy, Asthma & Immunology say in the September issue of the group's Journal of Allergy and Clinical Immunology, that they have decisively linked climate change to "longer pollen seasons, greater exposure and increased disease burden for late summer weeds, such as ragweed."

Scientists have found that increased carbon dioxide has resulted in pollen production increases of 60 percent to 90 percent in some ragweed varieties.

"We are starting to see a trend of increased plant size and the amount of pollen and other leaves and material that they produce," said Dr. Leonard Bielory, director of the Asthma and Allergy Research Center at New Jersey Medical School.

Lewis Ziska, a weed ecologist with the U.S. Department of Agriculture, researched how warmer temperatures and carbon dioxide emissions affect the growth of ragweed.

"We are seeing, with increasing CO2, the greater ability of the plant to produce pollen," Ziska said. "Initial results suggest that pollen is more allergenic; so, all of that adds up to an increase in the misery index."