Exposure to indoor pollutants is a significant asthma trigger, and recent guidelines from the European Academy of Allergy and Clinical Immunology assess the effects of key indoor air pollutants on the development of asthma and on asthma-related outcomes. Here, Professor Ioana Agache, one of the lead authors, discusses how asthma management can be improved by following these recommendations, while emphasising that broader action is also necessary to achieve meaningful progress in enhancing indoor air quality and asthma prevention and control.
Allergies and asthma are diseases influenced by environmental factors, both in their onset and progression. Among the many triggers for asthma, indoor exposure to pollutants is particularly significant, as people often spend a large part of their time indoors. Approximately 2.4 billion people, especially in low- and middle-income countries, are exposed to dangerous levels of indoor air pollutants.
Environmental control plays a vital role in asthma management. Given the complexity of the indoor exposome, an intervention approach that targets multiple indoor aggressors is likely to be an effective strategy.
Incorporating the evaluation of indoor exposure along with personalised adaptation and mitigation measures into the asthma management plan is highly recommended. Particular attention should be given to the most vulnerable groups: children, pregnant women, the elderly with multiple comorbidities, individuals with disabilities and those who are socio-economically disadvantaged.
Environmental-driven asthma endotypes – that is, individuals susceptible to environmental factors rather than genetic influences – could also benefit from this approach.
Rationale for the new EAACI guidelines
The 2025 European Academy of Allergy and Clinical Immunology (EAACI) Guidelines on Environmental Science For Allergy And Asthma emphasise management in the context of indoor pollution.
Previous guidelines have a broader focus on general health or respiratory health and are, therefore, not particularly specific for managing patients with asthma. Additionally, this guideline is evidence-informed, adhering to the GRADE system – the highest-quality framework for guideline development – unlike many documents based on expert opinion.
The 2025 guideline highlights the importance of distinguishing between different types of exposure that can occur over the course of a lifetime:
- Early life exposure, with abundant literature demonstrating that environmental stressors in early life are major contributors to allergic diseases and asthma
- Linear incremental exposure (e.g. the ageing effect)
- Repetitive school, recreational and occupational exposure
- Chronic low-level exposure
- Multiple-hit exposure, reflecting a combination of intermittent and persistent exposures with variable doses and lengths such as weight gain/loss, diet, exercise, pollution, microbiome, habitat change, etc.
Strategies to minimise exposure
The EAACI guidelines recommend reducing exposure to indoor pollutants through frequent indoor air monitoring and the use of smart ventilation systems. They advise preparedness for adverse asthma-related outcomes, such as loss of control, exacerbations and lung function decline, in settings with high levels of indoor pollution. For healthcare professionals, the evidence suggests incorporating environmental measures into their clinical advice for patients with asthma.
Adaptation measures to reduce the impact of indoor air pollutants on asthma-related outcomes at an individual level include:
- Reduction or removal of the sources of indoor pollutants
- Ventilation with clean outdoor air
- Use of air cleaners to filter the air
- Use of personal monitors and alert systems.
Guidance from healthcare professionals in applying and monitoring the efficacy of these measures is warranted.
Major and emerging indoor pollutants
The guideline provides recommendations on the risk provided by exposure to major indoor pollutants, such as volatile organic compounds, cleaning agents, dampness/mould and pesticides, on developing asthma, asthma symptoms, impaired lung function, deterioration of asthma control and exacerbations, together with adaptation and mitigation measures, thus facilitating both asthma prevention and control.
Additionally, the guideline discusses indoor pollutants of emerging concern, including phthalates, microplastics, lead, radon, asbestos and emissions from particulate matter such as cooking stoves, indoor fireplaces and heaters. It also mentions perfluorocarbons, UV filters, synthetic musk, parabens, siloxanes, neonicotinoids and drug residues.
Assessing exposure and patient vulnerability
The EAACI guideline advocates for assessing each patient’s vulnerability to environmental aggressors and, where possible, for improving resilience to these aggressions. Three key pillars to enhancing resilience are a healthy diet, a healthy microbiome and a healthy immune system.
The guidelines recommend concomitant assessment of exposure and of the patient’s vulnerability to environmental aggressors in judging the risk of adverse outcomes and in planning the adaptation and mitigation measures. The potential for adaptation should be individually evaluated in each patient with asthma and a personalised plan should be co-created together with the patient and their family.
The guideline provides a checklist for healthcare professionals managing patients with asthma, recommending that all indoor settings be evaluated: home, school, work and indoor recreational areas. Furthermore, we provide information on advanced ventilation techniques contributing to optimal indoor air quality.
Lastly, the EAACI guideline highlights the importance of integrating all individual exposures into the complex configuration of the indoor exposome, by including indoor allergens and infectious agents that interact synergistically with pollutants. This configuration is continuously influenced by outdoor pollution levels, human activities and the characteristics of the building.
The broader context
The combined effects of outdoor and indoor air pollutants are linked to seven million premature deaths each year. Vulnerable populations are disproportionately impacted.
There is a significant transgenerational effect of pollutants, impacting the foetus during pregnancy and continuing throughout an individual’s lifetime, as well as being transmitted to offspring. In fact, allergies are among the first environmentally driven chronic diseases that arise during a person’s life, highlighting the impact of environmental factors that may lead to other chronic diseases in adulthood.
The epidemic rise in allergies reported in recent decades parallels an increase in autoimmune disorders, cancer and metabolic disorders. All are chronic diseases arising from excessive environmental aggression along with a dysregulated resilient response of the human body.
Climate change intensifies the impacts of both outdoor and indoor pollution. There is a clear synergy between pollutants and heat or cold stress, as well as extreme weather events, that undermines the body’s resilient response. Due to extreme weather conditions, people are more likely to remain indoors, thus increasing their exposure to indoor pollution.
A multidisciplinary approach for managing allergic diseases and asthma
The traditional method of monitoring indoor pollutants involves air and dust analysis. Therefore, the range of analytical techniques must be continuously expanded. It is highly recommended to combine classical indoor analytics with human biomonitoring to promptly detect indoor pollutants using the exposome approach.
Continuous indoor air quality monitoring offers the best way to obtain real-time data on indoor air pollutant levels, while air cleaners and smart ventilation systems are vital tools for achieving optimal indoor air quality. However, challenges persist regarding the maturation of technologies, data mining and their interpretation. Therefore, healthcare professionals recommending adaptation and mitigation plans must collaborate closely with environmental health professionals, engineers, architects and others.
Furthermore, to develop an effective intersectoral model of the public health system, governments must collaborate with academia, media, business, community-based organisations and local communities.
What’s needed next?
We hope the evidence provided by these EAACI guidelines supports the establishment of legally binding standards and goals for indoor air quality at international, national and local levels.
Asthma management recommended by the current EAACI guidelines can improve asthma-related outcomes, but community and governmental measures to enhance indoor air quality are necessary to achieve a significant impact.
Policies aimed at promoting greater adaptation, such as reducing adaptation costs or enhancing indoor air quality, can deliver immediate benefits. There is an urgent need for increased awareness of the risks associated with poor indoor air quality and for the implementation of suitable regulations for public spaces.
Public health policies must undergo significant changes to adapt to the new understanding of the ecology of health and the interconnectedness of the biological, behavioural and physical domains. Therefore, it is essential to transform national health policies by incorporating the principles of environmental health.
Author
Ioana Agache MD PhD
Professor of allergy and clinical immunology, Transylvania University of Brasov, Romania
