Climate change cited as cause of recent increases in asthma, allergy prevalence
The effects of climate change may be responsible for recent increases in asthma and allergy disorder prevalence, spectrum and severity, according to an editorial published in The Journal of Allergy and Clinical Immunology.
Allergic diseases now affect nearly 30% of the world’s population, with the largest growth in low- and middle-income countries, Marc E. Rothenberg, MD, PhD, director of the division of allergy and immunology at Cincinnati Children’s Hospital, wrote in the editorial.
Genetic predisposition is a contributing factor to disease susceptibility, yet the rise of these diseases has occurred too quickly to be explained by a genetic shift in the population, said Rothenberg, who also is director of the Cincinnati Center for Eosinophilic Disorders.
“Over the past several decades, the hygiene hypothesis has been the dominant view of the cause of allergies. While I am by no means rejecting the hygiene hypothesis, I am putting forth a parallel hypothesis that I think has merit,” Rothenberg told Healio.
The hygiene hypothesis says that declining microbial exposure due to clean food and water, sanitation, antibiotic and vaccine use, modes of birth delivery and migration from rural to urban areas are major causes of the increasing incidence of allergic diseases.
However, Rothenberg noted in his editorial that this theory focuses on hygiene instead of host-commensal microbe interactions, which he called “likely primary contributors” to allergy development. Also, he wrote, there is little convincing evidence that cleaning local or personal environments protects against allergies.
In his editorial, Rothenberg additionally pointed out increases in other immunologic diseases over the past half century that have emerged with improvements in hygiene. He further noted dangers in the hypothesis’ potential to be used to justify opposition to measures designed to prevent infectious disease.
Meanwhile, he wrote, climate change has led to glacier recession, arctic ice melting, flooding, sea level rises, heat waves, wildfires, dispersal of plant and animal geographic ranges, food supply disturbances and increases in extreme weather — all changes that can impact allergic diseases.
“We have seen exacerbation of asthma during heat waves, especially in patients with lower socioeconomic status who cannot get ready access to air conditioning or environmental control measures,” Rothenberg told Healio.
“Although we have not seen this directly, I have cited the documented increase in asthma attacks with thunderstorms, especially reported events in Melbourne, Australia,” he continued.
The byproducts of burning fossil fuels contribute to air pollution as well, Rothenberg said, as ozone induces bronchial hyperresponsiveness, while particulate matter measuring less than 2.5 µm (PM2.5) is proinflammatory and penetrates the lungs.
Additionally, according to Rothenberg, early life exposure to air pollution increases sensitization to aeroallergens and food allergens, promotes eczema, worsens asthma, increases the permeability of the respiratory tract and decreases antiviral host defense mechanisms.
When taken together, Rothenberg said, the health impacts of climate change are affecting the allergy epidemic via cooperative mechanisms that accelerate disease development.
The next steps
Despite these data, further research is needed to link climate change with the allergy epidemic, particularly in the causal mechanisms and in the interaction between air pollution and climate change.
In the meantime, doctors can place a greater focus on environmental measures, Rothenberg said.
“Give these patients more attention, especially focused on environmental control measures such as the reduction of damp environments and reduced exposure to allergens that may be increased due to climate change including molds and other indoor allergens such as cockroaches,” he said.
He also recommended reducing exposure to PM2.5 particles such as cigarette smoke that are additive with stimuli associated with climate change. Patients should remain indoors, especially during thunderstorms. And, Rothenberg said, there should be a focus on compliance with medical management.
Also, he said, doctors can work to reduce climate change itself.
“Doctors are in a special position to influence the climate change crisis, including by educating about its impact and the imperative to modify its course,” he said, noting that the health sector in the United States is responsible for nearly 10% of the nation’s carbon emissions due to building operations such as energy usage, cooling and heating.
“Doctors and other health care workers can help reduce national carbon emissions by asking hospitals to have green policies and by reducing our own carbon emissions, such as by walking more or carpooling,” he said. “Doctors also can advocate for more research into the health effects of climate change and mitigation strategies, now focused on allergic diseases.”
For more information:
Marc E. Rothenberg, MD, PhD, can be reached at email@example.com.