Allergies and Asthma Prevalence Rise With Climate Change Extremes and Pollutants

Increasing environmental events driven by climate change and human activity exacerbate allergy and asthma conditions, further compounded by exposure to persistent pollutants like per-and polyfluoroalkyl substances and microplastics. | Image Credit: Habibur - stock.adobe.com

Allergy and asthma were linked with environmental events that are increasing in prevalence alongside natural disasters and other extreme weather events, including algal blooms, floods, heat stress, wild­fires, and thunderstorms that are coinciding with emissions of per-and polyfluoroalkyl substances (PFAS) and microplastics as downstream outcomes of these environmental events, according to a study published in Current Allergy and Asthma Reports.1

Human activities, primarily the burning of fossil fuels, are largely responsible for the greenhouse gas emissions driving these environmental changes. Weather intensity like droughts and floods have experienced dramatic rises over the past 5 years, based on data from NASA.2 Extreme weather is occurring more frequently, becoming longer-lasting, and more severe.

The respiratory tract is highly vulnerable to these environmental stressors.1 Asthma, a common chronic disease, affects nearly 25 million Americans and is exacerbated by air pollutants and extreme weather. Similarly, allergic rhinitis, eczema, and food allergies, reported by 1 in 3 adults and 1 in 4 children in the US, are worsened by conditions like high temperatures and thunderstorms. As environmental threats increase respiratory contaminant exposure, continued investigation into these intertwined health outcomes is crucial.

Extreme heat events, or heat waves, are becoming more frequent, intense, and prolonged. This poses a higher risk of premature death from respiratory diseases, especially for vulnerable populations such as children, older adults, pregnant individuals, and those with chronic conditions. Heat stress commonly exacerbates asthma by increasing inflammation, activating sensory fibers, and disrupting epithelial barriers, leading to bronchoconstriction.

High temperatures can also alter cytokine expression and T helper cell ratios, affect mucus production, and disrupt airway structural proteins. The interplay between environmental substances and extreme heat requires further research to understand additive, synergistic, or antagonistic health effects. Additionally, longer pollen seasons are introducing new allergenic species, likely worsening asthma and allergy cases.

Warmer weather, earlier snowmelt, and hotter spring and summer temperatures are escalating the intensity, frequency, and duration of wildfires. These fires release harmful emissions like carbon monoxide, carbon dioxide (CO2), nitric oxide, ozone, particulate matter, volatile organic compounds, and polycyclic aromatic hydrocarbons.

Exposure to wildfire smoke is directly linked to more emergency department visits for respiratory issues, as well as increased respiratory illness and mortality. Perinatal wildfire smoke exposure can lead to earlier use of upper respiratory medications and a higher risk of respiratory birth defects in children. Wildfire smoke also worsens asthma symptoms and increases asthma-related hospitalizations, particularly for young children. Epigenetic changes may contribute to these health outcomes, requiring further research.

The expansion of the wildland-urban interface, where human development meets wildlands, increases the risk of human-ignited wildfires. Fires in these areas are unique because they burn not only biomass but also homes, vehicles, and other synthetic materials, creating a distinct and poorly understood pulmonary toxicity profile. According to the authors, a key goal is to develop effective interventions to prevent adverse wildfire smoke exposure outcomes for communities, especially vulnerable populations like those with asthma and allergic rhinitis.

Changing temperatures, weather patterns, and water acidi­fication from increased CO2 emissions have altered aver­age surface water conditions, which in turn increases the risk of harmful algal blooms by expanding both the geographic range and seasonal growth windows of the different marine and freshwater phytoplankton species that comprise harmful algal blooms. While harmful algal blooms may seem like a niche public health burden, 15% of global asthma cases in coastal regions can be attributed to aerosol­ized harmful algal blooms toxins. Pulmonary exposure to harmful algal blooms has linked toxins to rapid onset of respiratory irri­tation symptoms such as cough and congestion, along with increases in hospital admission rates for respiratory diseases. The distance harmful algal blooms aerosols can travel is also unclear, especially as it relates to the size of the at-risk population and the mix­tures of aerosolized harmful algal blooms toxins amongst other atmospheric copollutants.

Floods, whether from sea or freshwater, heighten the risk of respiratory diseases, infections, and asthma exacerbations. This is primarily due to mold and microbial growth in flooded buildings. The sensitization to mold and fungi spores creates a proinflammatory environment, triggering conditions like allergic asthma and allergic rhinitis. Further research is needed to understand chronic flood-induced pulmonary issues and identify the specific mold and fungal strains responsible.

Thunderstorm asthma is a global phenomenon characterized by an increase in asthma attacks after thunderstorms. It's likely caused by a combination of high aeroallergen concentrations like ryegrass pollen, rain, and storm conditions that bring pollen to ground level. During a storm, pollen grains can rupture into smaller, more easily aerosolized subparticles due to physical disturbances. While fungal spores are abundant aeroallergens, their link to asthma exacerbations and thunderstorm asthma is not yet firmly established.

PFAS are pervasive, persistent organic compounds used in consumer goods for their nonstick properties. Their strong carbon-fluorine bonds make them extremely difficult to degrade, posing a significant threat to environmental and human health. Humans are exposed through ingestion, absorption, and inhalation. PFAS exposure can alter inflammasome function in the lung, impacting immune response. Further research is needed to establish comprehensive limits, legislation, and public awareness regarding these chemicals.

Microplastics are expected to increase in the environment and human bodies due to climate change impacts like increased precipitation and melting glaciers. Once released, microplastics do not easily degrade, persisting in environmental media. Inhaled microplastics, with their hydrophobic surfaces, may carry other pollutants and are linked to adverse respiratory outcomes such as irritation, interstitial lung disease, wheezing, and inflammation. More research is needed to understand their biological effects on pulmonary health, exposure routes, internal transport, and overall impact.

“In the future, meta-anal­yses to quantify the health effects of natural disasters could be an important tool to inform public health measures. It is thus especially relevant for the scientific community also to begin exploring prevention and mitigation techniques in preparation for future disasters,” the authors concluded.

References

1. Chou CK, Winker R, Rebuli ME, et al. Respiratory health impacts from natural disasters and other extreme weather events: the role of environmental stressors on asthma and allergies. Curr Allergy Asthma Rep. 2025(25);3-19. doi:10.1007/s11882-025-01206-9
2. Harrabin R. Nasa data reveals dramatic rise in intensity of weather events. The Guardian. June 17, 2025. Accessed June 30, 2025. https://www.theguardian.com/world/2025/jun/17/nasa-data-reveals-dramatic-rise-in-intensity-of-weather-events