The Heat Is Online

Pollen Rise Attributed to Warming


Scripps Howard News Service, Nov. 15, 2001

The potential impacts of climate change include everything from the sinking of tiny island nations to melting glaciers to increased weather extremes such as heat waves, drought and flooding.

Now experts say a growing number of studies show that global warming is probably one of the reasons a lot more people are sneezing and wheezing.

"We're seeing some surprises we hadn't thought about in terms of direct effects of carbon dioxide on ragweed pollen,'' said Paul Epstein, associate director of the Center for Health and the Global Environment at Harvard Medical School.

For example, Epstein said he has conducted a study, not yet published, that found when the amount of carbon dioxide is doubled, the result is sharp increases in the amount of pollen emitted by a weed.

In another study, in North Carolina, when scientists doubled the amount of carbon dioxide, seed and cone production by loblolly pines tripled, Epstein said. That, in turn, would increase tree pollen.

Carbon dioxide is the main greenhouse gas that many scientists believe is responsible for climate change. The Department of Energy recently reported that U.S. emissions of carbon dioxide rose by 3.1 percent in 2000, the latest year for which data are available. That's well above the 1.6 percent annual growth average over the past decade.

The United States, with less than 5 percent of the world's population, is responsible for 25 percent of the world's annual carbon emissions.

"So the doubling of asthma [cases in the United States] in the last several decades may be partially accountable just by the rise in CO2 [carbon dioxide], as well as the prolongation of seasons and the early arrival of spring and the late arrival of fall,'' Epstein said. Longer growing seasons mean weeds and trees are producing pollen more of the year.

In addition, global warming may be contributing to increases in certain kinds of air pollutants, such as ozone, which can make asthma worse, scientists said.

"We don't know exactly why asthma is on the increase and this could be one of the reasons,'' said Jonathan Patz, director of the Program on Health Effects of Global Environmental Change at the Johns Hopkins University School of Public Health.

"Ozone does not cause asthma, but it is known to acerbate asthma," Patz said. "If you have an increase in pollen and a potential increase in ozone, that's where there may be even synergistic problems.''

About 35 million Americans suffer from stuffy noses and other symptoms associated with seasonal, airborne allergens, according to the federal Centers for Disease Control and Prevention.

For as many as 20 million allergy suffers, the allergic response will, at some point, trigger a respiratory blockage and inflammation of the lungs known as asthma. Acute asthma attacks kill about 5,000 people a year in the United States - about 40 percent more deaths annually than were typically recorded 10 years ago.