ALLERGIES, CLIMATE CHANGE LINKED
More carbon dioxide means more pollen, researchers believe
MELROSE PARK, Ill. — From the roof of Gottlieb Memorial Hospital in the Chicago suburbs, an 83-yearold retired doctor finds troubling evidence of why so many people are sneezing and itching their eyes.
Joseph Leija counts the pollen and mold spores that collect on slides inside an air-sucking machine atop the six-story building.
“There’s been an increase, no doubt about it,” he says of the 5 a.m. weekday counts that he’s been doing as a volunteer for 24 years.
Scientists see a link to carbon dioxide, a heat-trapping greenhouse gas emitted by burning coal, oil and other fossil fuels. Tests show that the more carbon dioxide in the atmosphere, the more plants generally grow — and the more pollen they produce.
Though some plants grow more food or flowers as a result, more pollen can spell trouble.
Doctors say it’s contributing to a rise in seasonal hay fever and allergic asthma in the U.S., where the pollen season has lengthened up to 16 days since1995. If carbon dioxide emissions continue to increase, they expect allergic conditions will worsen.
“We’ve definitely seen a big increase in patients,” says allergist Brian Rotskoff, whose Clarity Allergy Center has offices a half-hour drive from where Leija counts pollen.
He says some kids are coming in at younger ages, and some adults are having worse symptoms or problems for the first time.
“The severity is affecting their quality of life,” he says, noting they’re having trouble sleeping and focusing at work or school.
Carbon connection
“The link between rising carbon dioxide and pollen is pretty clear,” says Lewis Ziska, a weed ecologist at the U.S. Department of Agriculture and a top researcher in the field.
His lab tests show that pollen production doubled from 5 grams to 10 grams per plant when carbon dioxide in the atmosphere rose from 280 parts per million in 1900 to 370 ppm in 2000.
He expects it could double again, to 20 grams, by 2075 if carbon emissions continue to climb. The world’s carbon dioxide concentration is about 400 ppm.
A 2011 study by Ziska and Leonard Bielory, an allergy and immunology expert at Rutgers University, found that the ragweed season, which peaks in the fall (trees peak in spring and grass in summer), got longer the farther north you go — where temperatures have risen more.
So in Oklahoma City, the season increased only one day from 1995 to 2009, but it jumped 16 days in Minneapolis and Fargo, N.D., and 27 days in Saskatoon, Canada.
Asthma is an ‘epidemic’
A new Centers for Disease Control and Prevention report suggests pediatric rates of hay fever, more common than drug or food allergies, remained stable from 1997 to 2011, based on interviews with parents.
As for asthma, doctors say it’s caused by many factors and exacerbated by pollen for the majority of asthmatics with allergic conditions. Federal data report a 17 percent increase in U.S. asthma prevalence from 2001 through mid-2012.
Asthma has become a “national epidemic” that affects 1 of every 12 people, or 56 million, the U.S. Environmental Protection Agency said this month. Most pediatric cases involve allergies, primarily hay fever.
Aside from pollen, the U.S. government’s third National Climate Assessment says climate change could increase other factors that contribute to respiratory allergies and asthma.
It points to higher summertime ozone concentrations, which make it more difficult to breathe, as well as more heavy downpours and rising air temperatures, which foster the growth of indoor fungi and molds.
‘‘
LEWIS ZISKA Weed ecologist at the U.S. Department of Agriculture and a top researcher in the field