Planet Allergy: Climate Change Fuels Allergies

in Outdoor Allergies
Published: July 2, 2010

Simulations performed by the University of Alaska Fairbanks foresee a shift from a forest dominated by conifers to one in which deciduous trees are twice as prevalent as conifers by 2050. “It’s also projected that 90 per cent of the historic tundra in Alaska, over the next century, will be forested because of melting permafrost,” says Demain.

“We’re going to start sustaining an ecosystem that’s going to support trees and grasslands that’s not there now.” In Canada’s northern territories, scientists have observed the tree line moving to higher altitudes and farther north. As the world warms up, the flora is changing and people are introduced to allergens not before seen in their environment.

Compound Pollution

Smog is driving more people with asthma to emergency rooms.

Pollution, as we all know, has repeatedly been shown to be the driver of climate change. Carbon dioxide emissions from automobiles, factories and power plants get trapped in the upper atmosphere, not allowing heat to escape. Pollution from those same sources, on the ground level, becomes ozone (commonly called smog) when it’s struck by sunlight.

“As the temperatures warm, ozone production goes into overdrive,” says Solomon.

The worst smog days can make anyone feel ill. “Even healthy people find smog burns their chest when they breathe and cough, and can cause pain when they exercise,” says Solomon. “But people with asthma can end up in the emergency room or [admitted to] the hospital.”

It’s also become clear in recent years that ragweed grows larger and is more allergenic with higher CO2 levels. Epstein was involved in a study at Harvard where he and other researchers grew ragweed in greenhouses. They found that when CO2 levels were doubled, the plants grew thicker, taller and greener – and produced 61 per cent more pollen.

(There is also new research showing that CO2 has a similar effect on some other plants and trees, such as poison ivy and the loblolly pine.)

Solomon and her colleagues, aware that both ozone and ragweed were going to be significant players in the allergy assault from climate change, wondered: where are people going to be walloped by both? They began to map out the areas of the United States where ozone and ragweed are prominent. They discovered that people along the Atlantic seaboard, in Midwest states such as Missouri, Illinois and Indiana, in the Great Lakes
region, and in southern and central California are looking at an itchy, sneeze-y, wheezy future.

“Those are the areas that will most likely have a hard time with global warming because we’re expecting that we’ll have both worse air quality and worse pollen,” she says. They may already be experiencing some of the effect: 13 of the Asthma and Allergy Foundation of America’s top 15 worst cities for asthma are located in one of the “overlap zones.”

The forecast is for more to come since “the ozone season will get longer and the ragweed season will get longer,” explains Solomon. “The smog season and the ragweed season will increasingly overlap.”

Insects On The Move

From our urban cities, overrun with smog and ragweed, we move to the British Columbia interior, where Vancouver allergist Stark has been investigating a new allergen: the mountain pine beetle. The population of this notorious pest began exploding in 1993. Ever since, it has been ravaging B.C. forests because winter temperatures no longer dip low enough to kill off the insects.

Stark became suspicious about the beetle’s health impact when a number of people in the regular visiting clinics he offers up in Prince George began testing positive for allergies to cockroach. Because cockroaches are unheard of in north-central B.C., but pine beetles had become prevalent, Stark asked one of his patients, an entomologist, to bring him some pine beetle extract.

Sure enough, while only 7 per cent of people in the Vancouver area were sensitized to pine beetle, 32 per cent of people in the north-central part of the province were.

However, the allergist gives two reasons why it’s difficult to pinpoint whether those who are sensitized have actually experienced allergy symptoms from the pine beetle. For one, pine beetles undertake a mass migration to new feeding grounds in early June, and it’s then that Stark believes people are being exposed to the allergen, because “there are literally millions of them in the air.”

But early June is also grass allergy season, so it’s been hard to tell whether people with respiratory symptoms are reacting to the beetles or to grass pollen. It’s also tough to track pine beetle symptoms because the insects move to new ground once they’ve killed all the trees in one area. So the newly sensitized are quickly no longer exposed to the allergen. Still, Stark calls it an “interesting phenomenon” – and a clear example of how climate change is altering the world of allergies.

Next: Wildfires and Mold