Climate change (CC) refers to large-scale climate changes resulting from global warming, the rapid increase in Earth’s surface temperature over the past few centuries. Children are an extremely vulnerable population, particularly with regard to their respiratory system, which is in direct contact with the atmosphere, but also with regard to the increased risk of infectious diseases and malnutrition.

Climate Change and Respiratory Health

Compared to adults, children are more exposed to pollutants, allergens, and infectious agents, as they have a higher respiratory rate, more frequent mouth breathing, and greater exposure to airborne particles (they spend more time outdoors and breathe at a lower height). Furthermore, the respiratory system in early life is more vulnerable to environmental factors due to the smaller diameter of the airways, resulting in a greater risk of obstruction and respiratory distress, and therefore long-term damage. Furthermore, the respiratory system is sensitive to extreme temperatures: exposure to cold, dry, or hot air can promote bronchial constriction. In fact, an increase in the relative risk of asthma exacerbations was observed in case of exposure to extremely hot or cold temperatures of 1.07 and 1.20 respectively

Climate Change and Respiratory Infections

Respiratory infections are known to be a major cause of morbidity and mortality in childhood. The long-term role of respiratory infections on the incidence of bacterial and viral respiratory infections remains uncertain. In temperate countries, respiratory viral infections occur predominantly in autumn and winter with lower temperatures, but it would be wrong to think that rising temperatures could lead to a reduction in these infections, as many other factors contribute. For example, before the SARS-CoV-2 epidemic and the introduction of nirsevimab prophylaxis, hospitalization rates for respiratory syncytial virus had remained stable, despite global warming and rising average temperatures. Even with regard to bacterial infections, it is difficult to predict the risk of infection for pathogens that are typically seasonal and favored by cold climates, such as Streptococcus pneumoniae.

Regarding Mycoplasma pneumoniae, a Japanese study that included 13,056 cases of Mycoplasma pneumonia between 1999 and 2007 reported a 16.9% weekly increase in Mycoplasma pneumonia cases for every 1°C increase in average temperature and a 4.1% increase for every 1% increase in relative humidity. In contrast, a study conducted in Europe between 2011 and 2016 did not report this association. Collaco et al., in a study conducted on 4 independent samples of patients with cystic fibrosis residing on two different continents, observed an association between mean annual temperature and the prevalence of Pseudomonas aeruginosa colonization and lung function, hypothesizing that temperature could impact lung function and Pseudomonas colonization through independent mechanisms.

Climate Change, Pollution and Respiratory Infections

CC also influences exposure to environmental pollutants such as ozone and PM 2.5. Global warming leads to increased ozone production; during drought periods, reduced rainfall prevents the washout of suspended PM 2.5, and CC promotes air stagnation, causing the accumulation of ozone and other pollutants. A systematic review reported an increased risk of pneumonia of 1.7% for every 10 mcg/m3 increase in ozone concentration and 1.8% for every 10 mcg/m3 increase in PM 2.5 concentration. A study conducted in the USA on 112,567 children under 2 years of age and 17,828 children between 3 and 17 years of age also observed a 15% increase in the risk of lower respiratory tract infections in children under 2 years of age and a 32% increase in children between 3 and 17 years of age for each additional 10 mcg/m3 increase in PM 2.5 concentration.

Climate Change, Pollen and Respiratory viruses

CC have caused an increase in the prevalence and severity of pollen-related allergic diseases. Rising temperatures have led to longer and earlier pollen seasons with higher pollen concentrations. Furthermore, CC may favor the spread and adaptation of pollen-producing plants to new geographic areas. In recent years, evidence of a synergistic effect of exposure to pollen and respiratory viruses emerged. Some studies have highlighted a positive correlation between viral infection rates and pollen concentrations. For example, a 2022 study reported an association between the autumn and spring pollen seasons and common viral infections in childhood. In 2021, Damialis et al. reported a correlation between the rate of SARS-CoV-2 infections and pollen concentrations. In another study, Gilles et al. observed that pollen exposure compromised some immunological mechanisms used against viruses, such as rhinovirus, by reducing the expression of antiviral genes. In another in vitro study, researchers observed that pollen exposure of respiratory cells altered their morphology, particularly the ciliary component. Other studies, however, have reported that pollen exposure was associated with a reduction in the risk and severity of influenza virus infections. Therefore, although a respiratory epithelium damaged by pollen may also be more susceptible to viral infections and a synergistic effect between pollen and viruses may be possible, the studies conducted to date are still heterogeneous and more data are needed.

Conclusions

Although further studies are needed to fully elucidate the impact of CC on respiratory infections, it is possible to hypothesize that CC may alter the geographic distribution of viruses and other pathogens, transmission patterns, and seasonality, which could lead to the development of new emerging infections and more frequent and severe pandemics.

Bibliography

• Camille Bignier, Lucile Havet, Margot Brisoux, Céline Omeiche, Swati Misra, Apolline Gonsard, David Drummond. Climate change and children’s respiratory health. Paediatric Respiratory Reviews 53 (2025) 64–73
• Maria-Viola Martikainen, Tarleena Tossavainen, Noora Hannukka, Marjut Roponen. Pollen, respiratory viruses, and climate change: Synergistic effects on human health. Environmental Research 219 (2023) 115149
• Onozuka D, Hashizume M, Hagihara A. Impact of weather factors on Mycoplasma pneumoniae pneumonia. Thorax 2009;64:507–11. https://doi.org/10.1136/thx.2008.111237.
• Collaco JM, McGready J, Green DM, Naughton KM, Watson CP, Shields T, et al. Effect of temperature on cystic fibrosis lung disease and infections: a replicated cohort study. PLoS One 2011;6:e27784.
• Nhung NTT, Amini H, Schindler C, Kutlar Joss M, Dien TM, Probst-Hensch N, et al. Short-term association between ambient air pollution and pneumonia in children: A systematic review and meta-analysis of time-series and case-crossover studies. Environ Pollut 2017;230:1000–8. https://doi.org/10.1016/j.envpol.2017.07.063.
• Horne BD, Joy EA, Hofmann MG, Gesteland PH, Cannon JB, Lefler JS, et al. Short-Term Elevation of Fine Particulate Matter Air Pollution and Acute Lower Respiratory Infection. Am J Respir Crit Care Med 2018;198:759–66. https://doi.org/10.1164/rccm.201709-1883OC
• Choi, Y.J., Lee, K.S., Lee, Y.S., Kim, K.R., Oh, J.W., 2022. Analysis of the association among air pollutants, allergenic pollen, and respiratory virus infection of children in guri, korea during recent 5 years. Allergy, Asthma Immunol. Res. 14 (3), 289–299
• Damialis, A., Gilles, S., Sofiev, M., Sofieva, V., Kolek, F., Bayr, D., et al., 2021. Higher airborne pollen concentrations correlated with increased SARS-CoV-2 infection rates, as evidenced from 31 countries across the globe. Proc. Natl. Acad. Sci. 118 (12).
• Gilles, S., Blume, C., Wimmer, M., Damialis, A., Meulenbroek, L., Gokkaya, M., et al., 2020. Pollen exposure weakens innate defense against respiratory viruses. Allergy Eur. J. Allergy Clin. Immunol. 75 (3), 576–587
• Van Cleemput, J., Poelaert, K.C.K., Laval, K., Impens, F., Van den Broeck, W., Gevaert, K., et al., 2019. Pollens destroy respiratory epithelial cell anchors and drive alphaherpesvirus infection. Sci. Rep. 9 (1), 1–15

Table 1 — Air quality thresholds: WHO 2021 vs EU 2030

Table 2 — Effects of climate and pollutants on pediatric respiratory diseases (SIMRI data + cited studies)

Table 3 — How to use these numbers in a medical-scientific article

FAQ (clinician-focused)

1) How does climate change affect pediatric respiratory health?
Children inhale more air per kilogram, breathe closer to ground level, and have smaller airways—so exposure to pollutants/allergens is higher and obstruction risk is greater. The airways are also sensitive to hot/cold/dry air, which can trigger bronchoconstriction. Simri

2) Do rising global temperatures reduce respiratory viral infections in children?
No. Pediatric respiratory viruses in temperate regions still peak in autumn–winter; multiple factors drive transmission. Pre-pandemic RSV hospitalizations remained stable despite warming, so a simple “warming → fewer infections” assumption is not supported. Simri

3) How do extreme temperatures influence pediatric asthma exacerbations?
Exposure to extremely hot or cold temperatures is associated with higher risk of asthma exacerbations (reported relative risks ~1.07 for heat and 1.20 for cold). Simri

4) What is the relationship between air pollution and pediatric pneumonia/ALRI?
Short-term increases of +10 µg/m³ are linked with higher risk: pneumonia +1.7% (ozone) and +1.8% (PM₂.₅); ALRI rises +15% in children <2 years and +32% in 3–17 years for PM₂.₅. Simri

5) What is known about pollen–virus interactions under climate change?
Warming is linked to earlier/longer pollen seasons and higher concentrations. Multi-country data show positive correlations between airborne pollen and SARS-CoV-2 infection rates; lab studies suggest pollen can dampen epithelial antiviral responses. However, findings across viruses and settings are heterogeneous. Simri

6) Is there evidence that weather factors influence Mycoplasma pneumoniae?
A Japanese study reported +16.9% per week M. pneumoniae cases per +1 °C increase (and +4.1% per +1% relative humidity), but this association was not replicated in Europe (2011–2016). Simri

7) How might climate relate to cystic fibrosis (CF) outcomes?
Across replicated cohorts, higher mean annual temperature was associated with Pseudomonas aeruginosa colonization prevalence and changes in lung function, suggesting temperature may influence CF morbidity via multiple mechanisms. Simri

8) Which air-quality thresholds are most relevant for clinicians?
The page summarizes WHO 2021 air-quality guideline values and EU 2030 limits (Directive 2024/2881) for PM₂.₅, PM₁₀, NO₂, and O₃ to frame counseling/anticipatory guidance. Simri

9) What are the main clinical/public-health implications?
Climate change may shift the geographic distribution, transmission patterns, and seasonality of pathogens—implying potential emergence of new infections and a higher likelihood of more frequent/severe pandemics. Anticipatory care and surveillance matter. 

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