Annual ragweed in bloom close-up view with selective focus on foreground
The growing season in Detroit has extended by approximately 28 days since the 1970s due to climate change, meaning a whole month more of pollen production, according to a March report from Climate Central. (istock photo)

Sneezing, itchy throat and eyes, and congestion caused by seasonal allergies is occurring earlier in the year and becoming more severe due to climate change. 

Since the 1970s, the growing season in Detroit has extended by approximately 28 days due to climate change, meaning a whole month more of pollen production, according to a March report from Climate Central, an independent science research and communication organization. In the annual report, titled “Seasonal allergies: pollen and mold,” the authors state that the increases in heat, precipitation, and carbon dioxide emissions associated with climate change all mean more pollen and mold, which cause seasonal allergies. 

And, it’s projected to get even worse. 

“The pollen season is shifting earlier and earlier over the United States,” said Yingxiao Zhang, a University of Michigan researcher unaffiliated with the report. In 2022, Zhang published original research that showed the link between climate change and increased pollen production. 

“The total pollen production will increase by 18% at the end of the century over southeastern Michigan with temperature and precipitation effects,” Zhang said. 

And it’s not just longer growing seasons that are causing pollen to increase — it’s the increased carbon in the atmosphere itself. Studies suggest that atmospheric CO2 concentration may increase pollen production on its own. 

Allergies Map of America
Climate change is causing an increase in the number of frost-free days across the country, and as a result, allergies are getting worse. Graphic from Climate Central’s 2023 “Seasonal allergies: pollen and mold” report.

“If we also include the CO2 effect, the changes can be up to 136%,” Zhang said, although noting the effect of carbon dioxide is “very uncertain.” 

In Southeast Michigan, pollen from the oak and cypress trees will become more dominant, according to Zhang. In one study, oak trees under controlled conditions exposed to higher CO2 levels produced significantly higher amounts of pollen than trees exposed to lower concentrations.

More than a quarter of adults and 19% of children in the United States have seasonal allergies. And they’re not just annoying. Allergies are costly: The annual cost of allergies is more than $18 billion per year, according to the American College of Allergy, Asthma, and Immunology. But quantifying how the percentage increases of pollen directly result in economic losses and the health impact, requires more research, Zhang said. 

chart for climate change
A graphic from the Intergovernmental Panel on Climate Change report showing the impact of climate change on current and future generations.

Allergies can also trigger asthma. Allergic asthma is the most common type of asthma, causing approximately 60% of cases. Detroit’s asthma rate is 46% higher than the state average and the city was named asthma capital of the United States in a 2022 Asthma and Allergy Foundation of America report

Alexander Rabin, a pulmonary and critical care physician at the University of Michigan, said patients are reporting asthma issues are happening earlier in the spring than normal, and lasting longer. 

“Pollen seasons are more intense and are lasting longer,” he said, resulting in increased exposure to allergens like ragweed which causes runny nose, rhinitis, sinusitis, and allergic asthma.

Specific to Michigan, Rabin said increasing thunderstorms tied to climate change are of concern because they tend to stir up pollen and increase exposure. 

“After a thunderstorm there are increased levels of allergens in the air, specifically pollen and mold spores. Wet conditions at the beginning of the thunderstorm cause these pollen grains to rupture, open up, and increase pollen in the air. This can get into your lungs, into your windpipe, into your lower airways, and cause increased asthma,” he said. 

Other parts of the country have it much worse for allergies. Detroit ranks “better than average” out of 100 U.S. Metro areas, coming in at 94 on the AAFA 2023 Allergies Capital Report, which is based on total pollen, medication use, and the number of allergy specialists. 

To minimize symptoms, experts recommend reducing exposure by keeping windows closed, washing your clothes and hair after coming in from outside, and avoiding going outside during peak times of the day. Medications like over-the-counter antihistamines and immunotherapy shots are other options as well. Rabin advises that patients take advantage of the advanced medicine available to control asthma symptoms ahead of time. 

But to avoid a drastically worsening allergic future, severe cuts in carbon dioxide emissions need to be made — and quickly. 

Zhang said in the past the temperature changes were the main driver of pollen increases. In the future, she said carbon dioxide itself could be the main cause. 

“The carbon dioxide concentration in the atmosphere is increasing exponentially,” she said. 

In 2022, global carbon dioxide emissions were at record highs, despite promises from nearly 200 countries that signed the 2015 Paris Agreement, agreeing to limit a global increase in temperatures to 1.5 degrees Celsius (2.7 degrees Fahrenheit), to avoid the worst impacts of climate change. 

Already, the world has warmed an average of 1.1 C, compared to preindustrial temperatures. 

“Climate change is considered a medical emergency,” said Lisa DelBuono, president of Michigan Clinicians for Climate Action, a coalition of Michigan health professionals committed to reducing the health impacts of climate change.

DelBuono noted that The Lancet, one of the world’s most prominent medical journals, calls climate change “the number one public health threat today.”

In 2020 DelBuono retired from her medical practice as a diagnostic pathologist to found the Michigan Clinicians for Climate Action. 

“I thought it was so critical that we address climate change,” she said. “The number one way in which climate change impacts health is it takes pre-existing conditions and exacerbates them,” she said, pointing to Detroit’s high asthma rates. 

“As air pollution worsens, you actually irritate the lining of your breathing tubes, such that you’re more sensitive to the exposure to the allergens,” she said “You’re more likely to react.” 

And the impact of climate change on health is disproportionately felt by people of color and children, DelBuono said. 

On Monday, leading climate experts from the Intergovernmental Panel on Climate Change, or IPCC, released the final part of its climate science report it issues periodically. Report authors established a new benchmark goal, calling for global greenhouse gas emission to be cut by 60% by 2035 to avoid a 1.5 C increase in average global temperature. 

Not quite reaching that goal, Michigan’s Gov. Gretchen Whitmer released a plan last year to cut emissions 52% by 2030 by phasing out coal-fired power plants, increasing electric vehicle infrastructure, improving energy efficiency in homes and buildings, and reducing greenhouse-gas causing waste.  

The IPCC authors said it’s likely the world will soon pass the 1.5 C threshold by the early 2030’s, but it’s still possible to avoid, requiring “a quantum leap in climate action.”

Jena is a BridgeDetroit's environmental reporter, covering everything from food and agricultural to pollution to climate change.

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