Pollen season 2019: why allergies worsen every year

The weather is warming up. The flowers are in bloom. The noses are running. The eyes water.

It's still the allergy season, already severe in states like Georgia and Tennessee. It is announcing itself brutal in cities like Chicago, where the harsh winter has delayed the appearance. Forecasters from other parts of the country are expecting 2019 to be worse than usual, if not the worst year of all time, in terms of allergies. Just like 2018, the year before and the year before.

The allergy season has become so predictable that nighttime comedians have begun to announce warnings about "pollen tsunami" and "pollen vortex" or a "perfect storm for allergies".

But it turns out that the truth lies behind this explosion: Pollen, a trigger of allergies for one in five Americans, soars year after year. And climate change is one of the main drivers of this increase.

For example, the rise in average temperatures leads to a longer ragweed pollen season, as you can see here:

Environmental Protection Agency

A recent study in the journal Planetary Lancet Health found that the number of pollen suspended in the air was increasing worldwide as average temperatures climbed. The majority of the 17 sites studied showed an increase in the amount of pollen and longer pollen seasons over 20 years.

And the faster the climate changes, the more it gets worse. That's why Alaska residents, who are warming twice as fast as the global average, are now facing particularly high risks of allergies.

Over a long period of time, seasonal allergies are one of the most robust examples of how global warming increases health risks. Allergies are already a heavy burden on health and will weigh more heavily on the economy.

"It's very strong. In fact, I think there is irrefutable data, "said Jeffrey Demain, director of the Alaska Allergy, Asthma and Immunology Center. "It has become the model of the impacts of climate change on health."

And since so many people are afflicted – according to estimates, nearly 50 million Americans have nasal allergies – scientists and health officials are now trying to understand the climatic factors behind these risks in hope to bring some relief after pollen avalanches.

Here's what scientists have figured out so far about the relationship between climate change and seasonal allergies.

Pollen becomes impossible to avoid

Allergies occur when the body's internal radar system locks on the wrong target, resulting in an overreaction of the immune system to an otherwise harmless substance.

This can cause mild discomfort such as hives or itchy eyes, or life-threatening problems such as anaphylaxis, where the drop in blood pressure and the airway begin to swell.

About 8% of American adults suffer from hay fever, also called allergic rhinitis, caused by pollen allergies. Most cases can be treated with antihistamines, but they cost the United States between $ 3.4 and $ 11.2 billion a year in direct medical costs, with a significantly higher cost due to lost productivity. Complications such as pollen – induced asthma attacks have also proven fatal and have led to more than 20,000 emergency room visits each year in the United States.

Pollen is a fine powder produced in the context of sexuality reproductive cycle of many plant varieties, including elms, ryegrass and ragweed.

Karl-Josef Hildenbrand / Photo Alliance / Getty Images

It is released in response to environmental signals such as temperature, precipitation, and sunlight. The size of the pollen grains varies from 9 microns to 200 microns. Thus, certain types of pollen can penetrate deep into the lungs and cause irritation, even in non-allergic people. High concentrations of pollen in the air trigger allergic reactions and can spread for miles, even indoors if the structures are not sealed.

Pollen production is experiencing three peaks of activity throughout the year. Trees like oak, ash, birch and maple see the pollens increase in the spring. The pollen of timothy, bluegrasses and orchards peaks in summer and ragweed pollen in autumn. For people sensitive to multiple varieties of pollen, this means there will be less relief in hot weather because these seasons overlap.

We already see a strong signal of climate change in pollinating plants

In general, the pollen emerges earlier in the year and the season is growing longer, especially ragweed pollen.

Ragweed is convenient for studying the effects of climate on pollen and allergies as it is an annual plant, unlike trees or perennials. This allows scientists to distinguish the effects of variables such as winter temperatures and precipitation from the previous season on ragweed pollen.

Lewis Ziska, plant physiologist at the US Department of Agriculture, told me that altering carbon dioxide concentrations from a pre-industrial level of 280 parts per million to current levels of over 400 ppm resulted in a doubling of pollen production per year. ragweed plant.

How can this happen? If you've looked at a bag or a bottle of plant fertilizer, you may have noticed three numbers that represent the phosphorus-nitrogen-potassium ratio inside. Different ratios encourage different aspects of plant growth, such as flowering or seed production. Carbon dioxide is also an important nutrient for plants, although it is not included in fertilizers (because it is a gas). It turns out that higher carbon dioxide concentrations encourage plants to produce more pollen.

For ragweed, a direct response of pollen to increased concentrations of carbon dioxide in the atmosphere can be observed:

American Foundation Against Asthma and Allergies

More pollen usually means more seeds, which means more ragweed in the next season. And warmer average temperatures mean that spring starts earlier and that winter comes later, giving pollen producers more time to vomit their sneezing particles.

We can also see the effects of CO2 on smaller scales. The researchers found that herb and ragweed plants increased their pollen production in response to localized increases in carbon dioxide, especially from cars' exhaust gases along a highway.

However, for other sources of allergens such as trees, the basics of a severe pollen season may be asked more than one year before the current season.

"What happens is that if the tree from the previous year had a" good season ", it tends to get loaded with carbohydrates, so in the spring it has a lot of carbohydrates to use for the production of flowers, "said Ziska. "When that happens, you can get a great bloom, and the consequences of that are inherent in the amount of pollen produced."

Far North hits the hardest

Alaska is warming up so fast that computer models have struggled to believe the results. This has huge consequences for people with allergies in the state, not just for pollen.

Tomorrow, from the Alaska Allergy, Asthma and Immunology Center, explained that rising temperatures melted permafrost beneath the cities of Alaska, causing moisture to penetrate homes. This moisture then lets the mold grow, causing more people to seek treatment for mold allergies.

Biting insects are also a growing concern. Warmer winters mean that more yellow wasps and wasps survive the cold months, which increases the risk of Alaskan bites. In 2006, Anchorage recorded an increase in the number of these insects and experienced its first two deaths due to insect bite allergies.

"It was so bad that they were canceling community events in the open air," said Tomorrow.

Tomorrow observed that population increases were seeking medical treatment following insect bites, while increases were more pronounced in northern Alaska. 1999 and 2001.

Nevertheless, pollen remains a major concern in Alaska as well, although the main source is birch, not ragweed. The birch pollen around Anchorage can get so bad that even non-allergic people get bogged down.

Stephen Nowers / Anchorage Daily News / MCT / Getty Images

"For a" high "count of pollen, it takes more than 175 grains per cubic meter," said Tomorrow. "In Alaska, we get peaks ranging from 2,000 to 4,000 grains per cubic meter."

In addition to the amount of pollen, Tomorrow noted that increasing concentrations of carbon dioxide increases the allergenic peptides present on the pollen. Peptides are the molecular signal that triggers the body's immune system. Therefore, more peptides present on a given pollen grain increase the severity of the allergy.

So it's not just more pollen; the pollen itself becomes more powerful by inducing an immune response.

Allergies will become worse, much worse

Researchers estimate that the pollen count of all varieties will double by 2040 in some parts of the country, depending on the path the world takes for greenhouse gas emissions. Scientists predict that the risk of tree pollen allergy will change in the eastern United States under a "high" scenario of greenhouse gas emissions:

American Foundation Against Asthma and Allergies

Here is the path of ragweed:

Central climate

And here's what to expect for grass pollen:

Central climate

This means that whatever pollen of your choice, the future holds more suffering for allergy sufferers.

For now, keep the handkerchiefs handy.