Created: 19 February 2026
by Lana Radchenko
Introduction
Respiratory allergies and asthma are distinctive conditions, but symptoms of both could be triggered by similar allergens such as pollen, dust, mould or animals. For some individuals, allergies could cause asthmatic symptoms: between 20%–30% of patients with allergic rhinitis also have asthma [1]. In the UK, according to Asthma + Lung UK, asthma affects approximately 7.2 million people. Common respiratory allergy, such as hay fever, or allergic rhinitis affects between 10-30% of adults and up to 40% of children. In some cases, these diseases are not just about daily discomfort - they are life-threatening conditions: approximately 250,000 people die prematurely each year from asthma; almost all of these deaths are avoidable [2].
Over the past two decades, the number of people affected by allergies has doubled. It is already the most common chronic disease in Europe and the UK is the leader in this list, with registered 10 million people suffering from, at least, one allergy. AllergyUK's statistics show that this is an issue for the young population - 50 % of people who have allergies are young adults under 35. While numbers are big, allergologists and doctors still do not have a clear understanding of how to protect the population from these diseases. This essay is an attempt to learn about the cause of respiratory allergies from an urban design perspective and review sustainable approaches to mitigating consequences and improving conditions for patients.
The rise of respiratory allergies and diseases in urban areas
Asthma and allergies are chronic diseases, which are more common across urban populations. The urban environment has a greater prevalence of asthma in comparison to rural populations [3], and recent data suggest that people living in urban areas are 20% more likely to suffer airborne pollen allergies than people living in rural areas [4]. The reasons for that tendency are poorly understood, because it is a result of complex environmental, biological and social factors [3]. It could be said that these numbers are a result of more accessible medical assessment, but there is a series of evidence that it is connected with a lack of vegetation diversity, poor ecological conditions and higher concentration of stress triggers.
The triggers could be anthropogenic, natural or a complex compilation of both, for example, dense planting of allergen trees in urban environments: trees are a natural resource of pollination, but their location and amount of species are artificially controlled by humans. This condition could worsen the allergic reaction - hay fever is caused by the sensory organs' reaction to pollen mostly happening in blooming seasons. Trees are the primary trigger of allergy reactions, but the organism's reaction depends on the concentration of pollen in the air. In that case, the cause of the respiratory reaction is pollen, but it is a human-made landscape.
The degraded and polluted air in urban areas is making the pollen remain in the air for longer, and diesel particles simplify the penetration of allergens into the airways and aggravate the reaction. Urban air consists of pollutant emissions and other hard contaminants such as grain, wood and construction dust, which are dangerous for asthmatics. In addition to primarily external unavoidable triggers, mould is an indoor threat, which is common in dwellings with poor ventilation, insulation, maintenance and heating. All these invisible but harmful elements for asthmatics constantly remain in the air, gradually accumulating their concentration.
With the rapid urbanisation and the increase of construction sites to meet future demand, the amount and concentration of this invisible industrial waste will grow proportionally. The atmospheric pollution emission will contribute to this process by sticking the triggers in the air. These conditions get worse on dry days and in areas with less humid air. The heat island effect, as a consequence of impermeable built-up areas rising, strengthens the spreading of particles and causes struggles for affected people. Knowing the forecasts and the health complications triggers, it could be concluded that the conditions for the population with respiratory diseases will degrade – the air pollution issues are expected to significantly increase in the next decades.
The future perspectives and trends
Global urbanisation is continuing, and it is expected that the current 4.4 billion people living in cities will double by 2050, according to the World Bank Group. Consequently, it will aggravate the current state. These risks are associated not only with more human-made pollutants, increased density and possible lowering of living standards, but also with socio-economic, ecological and political migration. 'Migration involves exposure to a new set of pollutants and allergens and changes in housing conditions, diet and accessibility to medical services, all of which are likely to affect migrants' health' [5].
The conditions could also be worsened by climate change, which refers to long-term shifts in temperatures and weather patterns. Since the 1800s, human activities have been the main accelerator of climate change, primarily due to the burning of fossil fuels like coal, oil and gas. These activities cause Global warming of 1.1°C above pre-industrial levels and, this has led to an increase in the frequency and intensity of extreme weather events, which have caused dangerous impacts on nature and people worldwide. 'Each increment of warming results in rapidly escalating hazards, such as more intense heatwaves, heavier rainfall, and other weather extremes that increase risks for human health and ecosystems' [6]. In 2022, the Intergovernmental Panel on Climate Change Sixth Assessment Report evidenced the connection between climate change and the threat to respiratory health [7].
Climate change causes the appearance of unpredictable natural shocks and disasters such as sandstorms, hurricanes and drying of air, which potentially could rapidly make the ecological situation worse and trigger allergic or asthmatic reactions in the population with respiratory diseases [8]. For instance, during the sandstorm in the Middle East in 2015, the number of people were hospitalised with respiratory problems, and some of the cases led to deaths caused by this extreme climate event [9]. The example shows that the consequence is reaching not only the individual level, but also leads to additional economic and operational pressure on the health care system. The most challenging part is the waving pattern of those emergency scenarios: more than the average number of patients need health care services urgently and at the same time. The indirect cost of allergies and respiratory diseases is a lower population productivity and activity caused by medical conditions, worsening quality of life and well-being conditions.
Respiratory diseases tend to become more common health conditions in the future. Hard waste products, pollution and climate change as a consequence of urbanisation and the air pollution will contribute to this process. The inevitable degradation of the state brings the question of how it could be mitigated in urban areas. In comparison between health conditions in urbanised and rural settlements, the main difference is obvious - the green infrastructure is denser and accessible. This information brings the question of what could be learned from ecosystems for the mitigation of hostile urban environments. And how the enhancement of urban ecology and ecosystems could systematically and fundamentally shift from degradation to, at least, a stable condition for human beings' health.
Mitigation by nature-based solutions
'The term 'ecosystem services' refers to the benefits human populations derive from ecosystems' [10]. They are conditionally categorised in four groups: provisioning, cultural, regulating and supporting. Provisioning services are all vital goods, such as food, materials, fresh water and medicinal resources, which could be harvested or extracted from nature. Non-material natural benefits are cultural services responsible for human well-being, leisure and education. Regulating services control the balance of ecosystems and their foundation. Adequate livelihood, health and clean air are the benefits of the natural regulatory processes. Supporting services are "glueing" all other services together by managing fundamental processes necessary for ecosystem formation. Human beings are the direct beneficiaries of the services, and their thriving is crucial for supporting human existence.
Most ecosystem services are free for users: clean air, safe drinking water, the ability to grow crops, and a comfortable climate. However, in the absence of healthy, full-fledged ecosystems, states are forced to provide ecosystem services through expensive technologies and additional measures, such as installing treatment facilities, planting mature trees, or restoring animal populations. The economic value of ecosystem services in an urban context is especially high: constant anthropogenic pressure on natural complexes threatens their balanced functioning, while the cost of alternative, artificial methods of providing ecosystem services is expensive and the economic benefit is not obvious. That argument advocates for the conservation of existing ecosystem services due to their contribution and necessity.
Green infrastructure and tree networks are the main contributors to air filtration. The introduction of green infrastructure elements in urban environments is one of the most effective measures to improve air quality [11]. 'Trees can reduce atmospheric CO2 mixing ratios by converting it into carbohydrates through photosynthesis and assimilating it into plant biomass. For that, green space in urban and peri-urban areas played a pivotal role in mitigating atmospheric CO2 in these settings [12]. Whilst urban trees can undoubtedly contribute towards long-term goals to reduce atmospheric carbon levels, it is important to set their value in context.
For example, Greater London’s 8.4 million trees are estimated to store 2.4 million tonnes of carbon and sequester about 77,200 tonnes of carbon each year. This is approximately 3% of Greater London’s annual carbon emissions, or to put it another way, enough to cover its carbon emissions for about 12 days. Therefore, in the grand scheme of things, urban forests make fairly modest contributions to the global challenge of reducing carbon emissions. Dust mitigation is another beneficial characteristic of trees. Urban plantations have proved to be low-cost sensors and monitors for monitoring urban dust aerosols in many studies worldwide. Leaves of plants act as filters for polluted air and can thus be used for both monitoring and mitigation of urban dust aerosols.
In the context of respiratory allergies, it is important to mention the controversy of the fact that trees are a cause of seasonal hay fever and at the same time providers of fresh air. Some trees, notably wind-pollinated species, can release copious amounts of pollen. This problem can be particularly acute with male cultivars of dioecious species. In some cases, such as Betula spp., this pollen also carries an allergy-causing risk that should be considered in planting specifications. When planting in proximity to vulnerable groups, such as the elderly (e.g. close to care homes) and young children (e.g. close to primary schools) the selection of species with a high allergy-causing potential should be avoided. 'In a more general sense, species diversity is crucial to reducing the dose potential of any single problematic species' [13].
The ecosystem services play a critical role in mitigating air pollution and neutralising hard waste particles. They contribute to freshening the air and mitigate climate change consequences. Providing quality green spaces and a diverse non-allergenic vegetation assortment, a more sustainable and friendlier environment could be achieved. Rapid economic growth and urban expansion have to be balanced with providing sufficient proportion and equal accessibility of green infrastructure. Looking back at history, it is not the first time when this dilemma has taken place. The importance of green infrastructure in human health and well-being is not a recent understanding. This narrative appeared during the Industrial Revolution - a driver of the first wave of urbanisation.
History of understanding the green infrastructure importance
In the nineteenth century, mechanisation led to the emergence of factories, which resulted in a rapid migration of people to cities and increased the density of urban areas. For example, between 1801 and 1851, the population of England more than doubled, from 8.3 million to 16.8 million, and by 1901 nearly doubled again to 30.5 million. London’s population grew from approximately 1 million in 1801 to nearly 2.4 million in 1851, and to over 6.5 million by the turn of the twentieth century. As a result, overcrowding, a mix of incompatible land uses, poor housing, urban sprawl, pollution, unsanitary conditions, lack of green spaces and congestion were common aspects of industrial cities. The consequences were not long in coming: in the first half of the nineteenth century, public health issues became obvious. Epidemics, particularly cholera, typhoid and tuberculosis were causes of an unprecedented death rate. These losses made an impact on society and led to the emergence of public health movements and initiatives.
The first big-scale modernisation of an existing urban environment was in Georges-Eugene Haussmann’s programme of public works in Paris between 1854 and 1873. The driver for these changes was the cholera epidemic that arrived in France in 1832. The cholera outbreak demonstrated the necessity of the hygienists’ proposed statistical public health model [14]. Haussmann initiated the demolition of overcrowded medieval neighbourhoods and the construction of wide, straight boulevards, new parks and squares, and public works like sewers, fountains, and aqueducts. The aim of the programme, as instructed by Napoleon III, was to bring air and light to the city, unify its neighbourhoods, and enhance its beauty. Almost immediately, this became an example followed by other cities across the world.
Today, urbanisation is experiencing a renaissance and facing new waves of pandemics. COVID-19 showed the vulnerability of urban environments to respiratory diseases, lack of open spaces and unequal access to green infrastructure. As a result, governments initiated programmes, which were created to adapt cities to similar challenges and mitigate the consequences of the shock. For example, Anne Hidalgo, the Mayor of Paris, was reelected in 2020 with her campaign focused on turning Paris into a 15-minute city offering parks and other everyday amenities within a short walk or bike distance. It is a marker that people recognise the importance and impact of a pedestrianised and green urban environment. At the same time, these initiatives could be interpreted as a 'fire-fighting' and human-centric approach rather than a sustainable and proactive one.
One of the fundamental misconceptions of modern urban planning's practical approach might be a continuation of twentieth-century planning traditions. The borders between different ecosystems are often diffuse, which does not correlate with urban physical and administrative boundaries. For example, natural habitats, species migration routes and ecosystem boundaries are more organic and complex. The existing settlement boundaries and areas of ecosystems are conflicting and non-intersecting definitions.' The borders between different ecosystems are often diffuse, it is both possible to define the city as one single ecosystem or to see the city as composed of several individual ecosystems, e.g. parks and lakes [15]. In other words, the legacy of Haussmann's rectified plan, as a reference point of the modern town planning approach to the issue, disclaims ecosystems' existence, and conflicts with its uncompromising orthogonal grids.
Modern approach for green infrastructure enhancement
In recent decades, a trend towards the mutual integration of urban and natural environments has been noticeable. The opposition between city and nature is gradually losing relevance: large natural areas are becoming a necessary part of the urban structure, and cities are striving to be more natural and “green”. Natural areas are considered not only as a valuable heritage that needs to be protected, but also as an important element of global environmental sustainability. Green areas in the city play a special role: they help reduce the heat island effect and neutralise harmful atmospheric emissions, and for city residents, access to natural and recreational areas is a significant factor influencing individual health and high quality of life [16].
In practice, the understanding does not find a needed level of implementation and action, especially if it is taken into account that the revelation of green infrastructure importance in urban environments was discussed and justified at the beginning of the 20th century. For instance, the Olympic Park in London is named the largest new park created in Europe in over 150 years. Its richly biodiverse and attractive green and blue infrastructure covers 45 hectares in total [17] with more than 6,000 new trees. In comparison with the closest city park - Victoria Park, opened to the public in 1845, which covered over 86 hectares with 4,500 trees and was surrounded by a lower population density. This example highlights the fact that despite constant population growth, the proportion of built-up areas and green infrastructure is not in favour of ecosystem services.
The green infrastructure is shrinking in favour of tackling housing crises and infrastructure extension. In-fill development is a normal practice in megalopolises, and that practice rarely takes into account investments in quality green infrastructure. The narrative of building on the green belt to meet delivery promises from mayors of Greater London has appeared in the last three decades. The ideas of private car usage are still politically risky initiatives, which demand large investments in alternative mass transit and transportation modes. The radical and even fundamental change of approach to urban development seems inevitable in hyper-urbanised areas.
Conclusion
The future forecast of respiratory diseases is not optimistic. Climate change, urbanisation and ecosystem degradation challenges are threatening populations with respiratory allergies and asthma, provoking the increase of patients in the future. This tends to put additional pressure on the health care system and will have economic consequences. However, the investment in quality green infrastructure could mitigate the respiratory disease development and reduce the amount of reaction triggers. Conservation and increase of ecosystem services presence in urban environments play a crucial role not only in improving the health conditions of individuals with asthma or respiratory allergies. Recognising the importance, in practice, the approach to respiratory challenges has not experienced radical changes since the 'birth' of urbanisation. The future forecast of exacerbation of climate and ecological conditions, and urban population growth demands a new approach for designing, governing and implementing the measures.
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