Climate change major cause of increased allergy prevalence
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Key takeaways:
- Increases in pollution and climate change effects escalate allergy disease.
- Researchers call for policymakers to include scientists in decision-making.
Global warming and climate change are affecting the human exposome and triggering more complex immune responses, according to a review published in Frontiers in Science.
The effects of climate change and continuing losses in biodiversity are causing an uptick in allergies along with other immune-mediated illnesses, the authors wrote.
“With climate change, there’s an increase in pollution, such as CO2, and particulate matter,” Mary Margaret Johnson, MD, PhD, principal research scientist at Harvard T.H. Chan School of Public Health and author on this paper, told Healio. “There’s an increase in wildfires and other things which increase our levels of pollution. And that’s a major source and a major risk factor impairing our immune systems.”
The review emphasizes that humans have evolved an immune system in order to protect them against environmental assaults and maintain health. However, immune dysregulation has increased in recent decades due to increased urbanization, antibiotic use, exposure to toxic chemicals, less diverse diets, a lack of physical activity and a decreased exposure to biodiverse environments.
The review also states that some of the biggest challenges to the human immune system as a result of global warming and climate change include an increased pollen burden, intensity and frequency of wildfires, sand and dust storms, thunderstorms, and heatwaves. All of these changes are having a serious impact on the prevalence of environmental allergies, Johnson said.
“The [pollen] season is starting earlier and lasting longer,” Johnson said. “People are being exposed to pollen for a longer amount of time. In addition, we have extreme weather patterns, especially in areas where there’s more precipitation, there’s more plant growth, and so there’s more pollen in general.”
The pollen that is produced also is increasing in allergenicity, Johnson continued.
“Then with climate change, you also get increases in winds. So, it’s possible that people are being exposed to slightly different pollen varieties than they have previously, depending on where they live in the world,” she said.
But pollen is not the only major contributor to allergic disease.
“With flooding, you’re going to get an increase in mold spores,” Johnson said. “That mold can be a trigger for people who have asthma and so that’s increasing their amount of asthma exacerbations. When you have a wildfire, you might get contamination of the water supply, as we’ve already seen in some of these large-scale fires. That’s going to impact a person’s health. It may challenge their immune system to function optimally.”
The epithelial barrier hypothesis is one of the theories proposed by the review as to why there is such an upward trend in allergic diseases. It proposes that increases in exposure to pollutants and other types of toxins such as food emulsifiers, pesticides, preservatives and microplastics damage the epithelial barrier.
“These types of toxins can cause the epithelial layer, which lines our guts, lungs and skin, to become leaky between cells,” Johnson said. “And that causes an inflammatory reaction, leading to more allergic disease.”
The authors called for several actions to mitigate the effects of climate change and global warming and their impact on immune-mediated illnesses. Decreasing the number of pollutants in our atmosphere and improving air quality, while also curbing wildfires, could cause a drastic change in allergy outcomes, the authors wrote. This could be mainly done by reducing the use of fossil fuels and focusing on clean energy sources.
Diversifying diets and providing access to natural spaces also can have a significant influence on immune systems, Johnson said.
“An optimal diet enhances our immune system. A diet that’s not diverse enough and perhaps missing some of the key nutrients will result in a person having nonoptimal immune functioning,” Johnson said.
“Your immune system is associated with all types of diseases. It's the basis for autoimmune disease, cancers and other chronic health outcomes. These all tie back into the functioning of your immune system,” she continued.
Improved air quality and access to green spaces can improve mental and physical health as well, Johnson said.
“If people are out in parks, walking or exercising, that’s obviously going to improve the health of the individual and the ability of the immune system to handle toxins from the environment,” Johnson said.
But in order to implement these changes, the authors emphasized that advocacy and research is not enough. Policymakers need to become involved and include scientists in their decision-making, they wrote.
Highlighting the cost-effectiveness of implementing climate change interventions compared with lifetime care costs of worsening and more prevalent allergic disease among other immune mediated illnesses needs to be at the forefront of environmental and health policy, the authors concluded.
“It’s kind of shocking that sometimes when the policies are being made, there isn’t a strong voice for health in the room,” Johnson said. “By involving scientists that know the literature and factors that can enhance the health of the occupants, it can influence a particular change such as decreasing pollutants or other things that contribute to allergic disease.”
For more information:
Mary Margaret Johnson, MD, PhD, can be reached at mjohnson@hsph.harvard.edu.