Climate Change, Air Pollution, and Allergic Respiratory Diseases: A Call to Action for Health Professionals
Allergic respiratory diseases, including asthma, rhinitis, and hay fever, are common chronic conditions caused by immune system disorders. These diseases are influenced by a variety of environmental factors, such as indoor and outdoor allergens, tobacco smoke, air pollution, cold air, and rapid urbanization. The prevalence of these conditions has been rising globally, with more than 272 million people suffering from asthma and millions affected by allergic rhinitis. In China, the overall prevalence of asthma among individuals over 20 years old is estimated at 4.2%, with higher rates observed in southeastern regions compared to northwestern areas. The global increase in asthma prevalence, which rose by 19.3% from 2007 to 2017, compared to an 8.0% increase from 1997 to 2007, may be an early signal of anthropogenic climate change.
Climate change and air pollution are significant drivers of the increased prevalence of respiratory allergies. The Intergovernmental Panel on Climate Change (IPCC) has concluded that the warming of the climate is unequivocal and is primarily attributed to the growing emission of greenhouse gases (GHGs). This warming has led to more intense and frequent heat waves, storms, floods, wildfires, and dust storms. These changes, in turn, affect the production and release of allergenic pollens and increase the growth of mites and spore formation. The relationships among climate change, air pollution, aeroallergens, and allergic respiratory diseases are complex and interactive.
Temperature extremes and variation are significant factors in the exacerbation of respiratory allergies. Extreme heat can increase airway resistance rapidly and trigger asthma symptoms by stimulating thermosensitive bronchopulmonary C-fiber nerves. Studies have shown that high temperatures lead to increased hospitalizations and emergency department visits for asthma. For instance, in Hong Kong, the relative risk for asthma hospitalizations increased when the daily mean temperature rose above 27°C during the hot season. Conversely, cold temperatures can induce bronchial hyper-reactivity, contraction of the tracheal smooth muscle, and decreased pulmonary circulation, leading to increased asthma admissions and pediatric outpatient visits. Temperature variation, such as diurnal temperature changes, also increases the risk of asthma and the aggravation of asthmatic symptoms.
Extreme weather events, including thunderstorms, floods, wildfires, and dust storms, have become more frequent and intense due to climate change. Thunderstorms, in particular, have been associated with asthma outbreaks, a phenomenon known as “thunderstorm asthma.” Thunderstorms can concentrate pollen grains at ground level and provoke the release of allergenic particles, leading to high atmospheric concentrations of inhalable allergen-carrying fine particles that penetrate the lower respiratory tract and cause an inflammatory response. Floods increase levels of microbes and mold growth in houses and the atmosphere, which are linked to significant increases in asthma admissions and emergency department visits. Wildfires generate various pollutants, including particulate matter (PM), ozone (O3), and organic compounds, which are consistently associated with respiratory symptoms, particularly asthma. Dust storms, which are expected to increase due to drought and desertification, carry allergens such as dust mites, pollen, and fungal spores, enhancing allergic reactions within atopic asthmatics.
Climate-driven human and plant migration also contribute to the rise in allergic respiratory diseases. Rising sea levels and water degradation force human migration, exposing individuals to different sets of allergens and changes in socio-economic backgrounds, housing conditions, diet, and indoor and outdoor contamination. Plant migrations due to global warming introduce new plant types and aeroallergens to regions where they did not previously exist, potentially aggravating respiratory symptoms and concomitant anaphylaxis.
Air pollution, particularly concentrations of PM and secondary pollutants like O3, is projected to increase with climate warming and changing patterns of atmospheric circulation. Climate change enhances the severity and frequency of air pollution episodes, which indirectly affect allergic respiratory diseases. Elevated temperatures and solar irradiation enhance photochemical reactions, generating O3 at ground level. Wildfires and dust storms increase natural emissions of PM, while rising energy demands for cooling or heating increase anthropogenic emissions. Exposure to high levels of O3 and PM has been linked to epidemics of asthma and exacerbations of asthmatic symptoms. The interaction between extreme heat and air pollution exacerbates physiologic dysfunction and respiratory symptoms in patients with chronic lung disease, leading to excess mortality and hospital admissions for respiratory conditions.
Aeroallergens, including pollen, molds, and spores, are increasing in many countries due to climate change, resulting in a greater likelihood of asthma development. Increased temperature and CO2 levels affect the onset and duration of pollen seasons and the concentration of aeroallergens. Elevated CO2 levels and temperatures increase the major allergenic peptide content in ragweed pollen, enhancing its allergenicity. Air pollutants, particularly O3, PM, and diesel exhaust, increase the permeability of allergens in the respiratory mucous membranes and strengthen the allergen-induced inflammatory effect on airways. The synergistic effects of aeroallergens and air pollution intensify the allergic response, leading to increased risk of allergic respiratory diseases.
Certain groups are more vulnerable to the effects of climate change and air pollution on respiratory allergies. Urban residents, who are exposed to synergistic exposures of air pollutants, high temperatures, and allergens, have a greater risk of allergic respiratory diseases. Children, who have higher asthma prevalence than adults and are more sensitive to environmental exposures, are particularly vulnerable. Prenatal and perinatal exposure to air pollutants has been linked to increased respiratory symptoms and the risk of developing childhood asthma.
Health professionals play a crucial role in addressing the impact of climate change on allergic respiratory diseases. There is an urgent need to transform societies to achieve a 45% reduction in GHG emissions by 2030 and near-zero emissions by 2050 to limit warming to below 1.5°C relative to pre-industrial levels. Health professionals should advocate for GHG mitigation, air pollution, and allergen reduction. Clinical interventions should be considered to minimize climate change-related risks in allergic respiratory diseases. Reducing atmospheric allergens through public approaches and urban planning, such as creating buffer zones between high-traffic areas and residential spaces and implementing the “Allergy Safe Tree Decalogue” model, can significantly decrease toxic exposures. Building climate-resilient health systems with consistent monitoring and early warning systems of weather-related events can help mitigate air pollution and aeroallergen health effects.
In conclusion, climate change, air pollution, and aeroallergens have complex and interactive effects on allergic respiratory diseases. The synergistic effects of heat, air pollution, and aeroallergens cause excess mortality and hospital admissions for these conditions. Health professionals must promote effective strategies to cope with the health effects of global environmental changes, undertake research on climate change and respiratory health, and apply these findings to disease prevention and control. By addressing these challenges, health professionals can help mitigate the impact of climate change on respiratory health and improve the quality of life for individuals affected by allergic respiratory diseases.
doi.org/10.1097/CM9.0000000000000861
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