Relationship between Climate Change, Air Pollution and Allergic Diseases Caused by Ambrosia artemisiifolia (Common Ragweed)

Abstract

Objective: Influence of climate change and outdoor air pollution (through anthropogenic factors, including heavy traffic, industry and other human activities polluting the environment), which contribute to global warming and increase the allergenicity of some plants (common ragweed) on allergenic patterns, with a direct negative impact on human health, causing or exacerbating allergic respiratory diseases such as bronchial asthma and allergic rhinitis, changing the pattern of respiratory tract infections and premature deaths in Europe. The present study aims to highlight the link between climate change, outdoor air pollution, altered allergenicity of palms and possible behavioural risk factors in the environment.

Methods:The clinical studies selected in this research highlighted the links between climate change, air pollutants and the occurrence/exacerbation of aeroallergen-induced respiratory disease; climate change (as an inducer of allergic respiratory disease), increasing global mean ambient air temperature and aeroallergens; climate change, global warming, [CO₂] concentration and aeroallergens; climate change, atmospheric humidity, dust storms and aeroallergens; urbanisation (anthropogenic influence), air pollution and aeroallergens; potential of different plant species (common ragweed) for Ni accumulation and possible effects on the human body.

Results:The medical implications of increased atmospheric [CO₂] concentration are either direct (effect of [CO₂] on human physiology and pathophysiology) or indirect (alteration of plant physiology associated with human disease). In an urban area with high [CO₂] concentrations, ragweed grows faster, flowers earlier and more intensively, which will lead to increased pollen production compared to rural areas. Over time, climate change leads to changes in allergen (common ragweed) patterns, followed by effects on human health (causing or exacerbating allergic respiratory diseases such as bronchial asthma and allergic rhinitis and changing the pattern of respiratory tract infections).

Conclusion:Climate change is changing air pollution patterns, particularly in urbanised areas of the world, with a significant effect on human health. Allergen patterns are also changing in response to climate change. Lifestyle adjustments are important to mitigate the health effects of air pollution and reduce the occurrence and progression of respiratory diseases.

Keywords:climate change, air pollutants, climatic conditions, global average temperature, atmospheric humidity, aeroallergens, respiratory diseases, allergic rhinitis, bronchial asthma.

INTRODUCTION

Climate change and outdoor air pollution (from heavy traffic, industry and other human activities) contribute to global warming, increase allergenicity of some plants and have a direct negative effect on human health, contributing to the burden of disease and premature death in Europe (including Romania) (1, 2).

The EU Air Quality Directive aims to protect human health, vegetation and natural ecosystems by setting target limit values for air pollutants. In recent years, most epidemiological studies on air quality have focused on the possible links between exposure to polluted air and the occurrence of respiratory diseases and related morbidity and mortality (air pollutants and allergens are considered to have a significant impact on human health). Reduced exposure to plant allergens and lifestyle adjustments could mitigate the effects of air pollution on human health and reduce the occurrence and progression of aeroallergen- induced respiratory diseases (1-3).

The World Health Organization (WHO) has identified climate change as the major environmental risk factor affecting human health: "Exposure to environmental pollution reduces quality of life as people live with associated health conditions (e.g., bronchial asthma); the number of healthy life years lost in EU-28 countries due to environmental pollution is estimated at over 20 million annually, rising to over 25 million for EEA countries." (WHO, 2016c) (2).

MATERIAL AND METHOD

Selected clinical studies in the first part of this research have highlighted links between climate change, air pollutants and the occurrence/ exacerbation of aeroallergen-induced respiratory diseases. The second part includes results on climate change (as an inducer of allergic respiratory diseases), increasing global mean ambient air temperature and aeroallergens. The third part includes results from clinical studies on climate change, global warming, [CO₂] concentration and aeroallergens. The fourth part includes results on climate change, atmospheric humidity, dust storms and aeroallergens; urbanisation (anthropogenic influence), air pollution and aeroallergens. The fifth part comprises findings reported by clinical studies on the potential of different plant species (common ragweed) for Ni accumulation and effects on the human body, urbanisation (anthropogenic influence), air pollution and aeroallergens.

Literature review was the method chosen by the authors of the present research. We performed an electronic search of scientific databases widely available on the internet by using the following search terms: climate change, air pollutants, climatic conditions, global mean temperature, atmospheric humidity, aeroallergens, respiratory diseases, allergic rhinitis, bronchial asthma, respirable dusts, different accumulation potential.

Searching scientific databases such as Google Scholar, Web of Science, Scopus and PubMed returned results but not all were relevant. In the next step, an exhaustive search using the Google search engine was required. This new search returned a large number of results, clinical studies, manuals, guidelines and recommendations from internationally recognised institutions or organisations, such as WHO, from which only published texts containing both general information and specific quantifiable information on climate change and air pollutants and their effects on health were selected.

RESULTS

Climate change, air pollutants, respiratory diseases and aeroallergens

Climate change, air pollutants, respiratory diseases and aeroallergens Climate change causes or exacerbates respiratory diseases, respiratory tract infections and allergic diseases. Allergic rhinitis (AR) and bronchial asthma (BA) are allergic respiratory diseases with a growing prevalence, with a significant pathophysiological impact on the human body, which also reflects the influence of anthropogenic factors and lifestyle changes (3-6).

Allergic diseases are defined as hypersensitivities initiated by specific immunological mechanisms (abnormal adaptive immune responses). They are a major public health problem in European countries (including Romania). In recent decades, the frequency of both allergies and associated allergic diseases (AR, BA, atopic dermatitis and food allergies) has been increasing (4-8).

Climate change and air pollutants influence physiological processes and the immune system towards the development of allergies (through oxidative stress and inflammation, disruption of epithelial protective barriers and/or related microbial disruption/modification) (7-9). The seasonality and severity of both AR and BA are influenced by the growth patterns of allergen species, which can act synergistically with air pollutants, and by exposures to a high-temperature environment, which can affect respiratory mucosal homeostasis (Figure 1).

Climate change alters the pattern of respiratory tract infections linked to pollen allergy and causes or exacerbates allergic respiratory diseases by increasing the growth rate of plants and the amount of pollen produced by each plant, increasing the amount of allergenic proteins contained in pollen, changing the timing of the start of plant growth and the start of the pollen season (pollen production and seasons start earlier in spring and are longer in autumn) (5-7, 11, 12) (Figure 2).

Intense and prolonged periods of pollen as well as possible changes in pollen have led to changes in allergen patterns, increased severity of respiratory tract infections and altered seasonality of allergy, AR and BA symptoms (5-9, 11, 12).

Climate change (as an inducer of allergic respiratory diseases) and the consequences on allergic rhinitis and bronchial asthma, increasing global average ambient air temperature and aeroallergens

Over the past eight years (2015–2022), the global mean ambient air temperature (GATMa) over the Earth's surface has been increasing at a much faster rate than in the pre-industrial period, but more so than in the past 50 years, making this the 'warmest' period on record in history so far. Basically, according to the recorded data, Europe "warmed" faster than the global average and 2022 was considered "one of the six warmest years" on record (with anomaly ranges of 1.13°C to 1.18°C above pre-industrial levels) (1, 10, 13-21). In 2022, particularly large warming was observed in Eastern Europe (including Romania), Scandinavia and the Eastern part of the Iberian Peninsula.

For a long time, global warming was not considered to be directly related to increased plant allergenicity, unlike air pollution. However, studies show that higher atmospheric air temperatures and increased frequency of heat waves, which are largely influenced by anthropogenic factors (in particular through greenhouse gas emissions – by absorbing solar energy and redirecting it back to the earth's surface, greenhouse gases have become overabundant in some very hot periods, trapping an excessive amount of heat in the atmosphere, and thus, leading to further overheating of the atmospheric air), have led to increased morbidity rates from respiratory diseases over time. Of these, allergic diseases (allergic rhinitis, allergic bronchial asthma, atopic dermatitis) have a significant socio-economic burden and affect a considerable segment of the population (1, 10, 13-21).

According to WHO, half of the world's population will have an allergic disease by 2050 (1). Currently, at least 300 million people are thought to be diagnosed with BA and more than 300 million people with AR worldwide (1). Thus, all signatories to the United Nations Framework Convention on Climate Change (UNFCCC), through the 2015 Paris Agreement, committed to continue efforts to limit global temperature increase to no more than 1.5°C and to limit global temperature increase to <2°C above pre-industrial levels by 2050 (1, 10, 13-21) (Figure 3).

Climate modelling has been used to estimate future climate change for different emission scenarios and the underlying socio-economic pathways (Shared Socioeconomic Pathways, SSP). Without significant efforts to reduce gas emissions, global temperature rise will be rapid in the coming period. The only scenarios that are likely to fall within the limits set by the Paris Agreement are those that propose and assume a drastic reduction in gas emissions and a decrease in [CO₂] emissions to zero and, at net negative emissions, in 2050 (SSP1-1.9 scenario) or around 2080 (SSP1-2.6 scenario) (1, 10, 13-21).

Climate change, global warming and the concentration of [CO₂]

Ambient air temperature and atmospheric [CO₂] concentration are the two main environmental parameters that are expected to continue to increase in the coming years with local, regional and/or global climate change. Both are also increasing in response to changes in the level of urbanisation (anthropogenic influences), to which they appear to be closely linked. Research in recent years has shown that urbanisation increased the daily average [CO₂] concentration by about 30% over a 24-hour period. In typical climate change scenarios, both ambient air temperature and [CO₂] concentration increase concomitantly, also leading to increased pollen production. Increases in [CO₂] concentration stimulate photosynthesis, vegetative growth and pollen production (22-29) (Table 1).

A change in the metabolic mechanism of pollen proteins comes with profound vegetative changes. The nitrogen content of the soil does not explain the differences between the amount of allergen in urban and rural areas. Ragweed is influenced by the concentration of [CO₂]; thus, it has been shown that ragweed pollen from rural areas contains more allergen compared to pollen from urban areas in response to urbanisation (22-29).

Data from research to date indicate that urban environments are already subject to higher ambient temperatures and increased concentrations of atmospheric [CO₂], which are projected to increase for the entire planet, consistent with short-term (~50 years) projections by the Intergovernmental Panel on Climate Change. Differences in ambient air temperature and [CO₂] concentration increases between urban and rural areas have been shown to affect plant growth and fecundity (22-29).

Increased atmospheric [CO₂] concentration affects plant biology and physiology by providing more carbon for photosynthesis, biomass production and increased [CO₂] fertilisation. These factors can influence the spread of invasive plants, the onset, duration and intensity of pollination, allergen content and allergenicity of pollen grains, biological aerosol particles (22-29).

Some air pollutants have a direct effect on the respiratory system, but also interact with plants, leading to increased production and allergenicity of the respective pollen e.g., common ragweed). In an urban area with high [CO₂] concentrations, common ragweed grows faster, flowers earlier and more intensively, leading to increased pollen production, compared to rural areas where pollen production is lower, but also [CO₂] concentrations are lower. Phenological events are also influenced by environmental changes induced by urbanisation e.g., seed germination and floral initiation occur earlier) (22-29).

Changes in climate and land use influence the composition and spread of microbial surface communities, from which allergens can be emitted into the atmosphere. The molecular mechanisms by which air pollutants and climatic parameters can influence allergic diseases are complex. Risk factors for the development of allergic diseases include genetic predisposition of the individual (atopy), outdoor as well as indoor environmental pollution (tobacco smoke, ozone, nitrogen oxides, diesel exhaust particles, etc), low childhood exposure to pathogens and parasites, poor diet/nutrition, psychological/social stress (22-29).

Global warming alters local vegetation patterns, causes plants to grow at different rates, accelerates growth rates and alters plant phenology, leading to increases in air pollen concentration and geographical changes in plant distribution. Regarding floral development, data showed small but measurable phenological differences depending on ambient temperature and [CO₂] concentration; thus, shedding of pollen grains occurs earlier in urbanised areas and a higher amount of allergen is present in the air in urbanised areas (the number of common ragweed pollen grains in the atmosphere has increased in recent years and the allergen content was found to be a higher in urban compared to rural areas) (22-29).

The genus Ambrosia, which includes the type Ambrosia artemisiifolia (common ragweed), has long been recognised as a significant cause of AR. According to clinical studies, common ragweed causes more cases of seasonal AR than all other plants combined. In addition, the total pollen production per plant appears to have significantly increased due to rising concentration of [CO₂] (22-29).

The effects of climate change on allergenic plants can alter the general characteristics of the pollen season. For common ragweed, which releases aeroallergens into the environment, there are direct effects of climate change, including increased pollen production and allergen quantity, plant migration and spread, changes in the allergenic potential of common ragweed pollen, and changes in the transcriptome of common ragweed pollen. The differential response of common ragweed to the effects of climate change in urban environments has also been shown to have important medical implications (22-29).

Above-ground biomass is increasing, with environmental changes being induced by accelerated urbanisation (10) (Figure 4).

This has led to the observation of more atmospheric pollen, establishing for the first time a relationship between climate change and human exposure to pollen. Laboratory investigations which were suggesting a greater potential for seasonal AR resulting from increased atmospheric [CO₂] concentration also included increases in pollen production by common ragweed (30). Urbanisation appears to act as a surrogate for global environmental change, demonstrating in recent years the likely strong links between changes in global ambient air temperature, increased [CO₂] concentration and influence on public health. The health implications of increased atmospheric [CO₂] concentration are either direct (effect [CO₂] on human physiology and pathophysiology) or indirect (alteration of plant physiology associated with human disease) (10, 22-30).

Climate change, atmospheric humidity, dust storms and aeroallergens

Climate change influences the amount and type of pollutants in the air that interact with aeroallergens. Thus, the individual and/or combined effects of these environmental parameters on human health with respiratory effects are very difficult to predict. A recent European Economic Area report showed that a large proportion of European citizens and ecosystems are exposed to concentrations of air pollutants exceeding the legal limit values according to EU Guidelines and WHO Guidelines (1, 2, 10, 31-41).

Environmental allergens, such as common ragweed pollen allergens, are plant-derived proteins that can trigger cascades of chemical and biological reactions in the immune system and lead to allergic sensitisation and IgE antibody formation. In addition to allergens, adjuvants (substances that promote pro-allergic immune responses) and their interaction with the immune system also play an important role in the development of allergies (10, 22, 30-41).

Air pollution has altered the allergenic potential of pollens in the presence of specific weather conditions (the mechanisms underlying all these interactions are not yet well understood). In various European clinical studies, climate change has been associated with an increased duration of the common ragweed pollen season, demonstrating that changes in atmospheric humidity and precipitation were very likely to affect plant growth and distribution (10, 22, 30-41).

In recent years, a direct link between increased humidity and/or heavy rainfall and increased proliferation of aeroallergenic plants (such as common ragweed) has been found. Increased exacerbations of asthma attacks and hospitalisations, as well as episodes of bronchial asthma following storms, have been documented in clinical studies. Changes in local vegetation patterns, through changes in geographical distribution (colonisation of geographical areas with new species) and plant 'migration', have led to increased prevalence and severity of AR and BA due to sensitisation and cross-reactivity with other pre-existing species (10, 22, 30-41).

Dust particles from thunderstorms carry within them biological and organic components with allergenic and pathogenic activity. Clinical studies have shown that the frequency and intensity of thunderstorms have potentially increased, causing and aggravating respiratory diseases, including AR and BA. Air pollutants can act as adjuvants during storms, altering the immunogenicity of allergenic proteins (10, 22, 30-41).

Extreme climatic events (rain, storms, wet weather conditions) can be considered to be the cause of acute exacerbations of BA, such as 'storm asthma', possibly caused by the dispersion of inhalable allergic particles from plant pollen through osmotic breakdown. During these episodes, if they also occur during the allergen season, a large number of patients rapidly develop asthmatic symptoms (within the first 20-30 minutes of a major storm), which arise from a sudden release of massive amounts of aeroallergens, which are causative factors of pollen allergy. Allergenic proteins can be released from pollen after cell injury and osmotic breakdown of pollen grains contained in fine airborne particles [PM10/PM2.5], and/or under conditions of increased humidity (after heavy rainfall and in wet weather conditions) (10, 22, 30-41).

Interactions of the above-mentioned changes with the photoperiod of common ragweed will alter the migration pattern of these aeroallergenic plants. Both atmospheric pollutants and climatic changes can influence the environmental abundance of allergenic bioparticles and lead to the release of allergenic proteins and biogenic adjuvants, can agglomerate allergenic proteins and act as adjuvants inducing epithelial injury and inflammation. Case studies on the occurrence of storm-induced episodes of bronchial asthma have been documented over time. The largest such episode described in the literature occurred in Melbourne, Australia, on 21 November 2016, when ~4000 patients presented to area hospitals with post-storm asthmatic respiratory symptoms.

Urban-induced climate change (anthropogenic influence), air pollution and aeroallergens

Anthropogenic influence 'shapes' the environment: anthropogenic emissions affect air quality and climate at local, regional and/or global scales. Changes in atmospheric aerosol composition, oxidant concentrations and climatic parameters can induce chemical changes in allergens, increase oxidative stress in the human body and incline the immune system towards allergic reactions (10, 22, 42-44).

The results of clinical studies have shown that allergic diseases (AR, BA and atopic dermatitis) are associated with exposure to traffic-related air pollution, with results varying from study to study.

Air pollution in urban areas with high levels of car traffic is characterised by increased air concentrations of inhalable particulate matter (PM), nitrogen dioxide [SO2] and ozone [O3]. The effects of these air pollutants on the lungs depend on: the type of pollutant, concentration of the pollutant in the environment, duration of exposure to the environment and total lung ventilation of exposed individuals, etc. Aeroallergens from the outdoor environment e.g., pollen grains of the common ragweed plant), can induce bronchial obstruction in atopic subjects (10, 22, 42-44).

Fine particulate matter [PM10/PM2,5] is considered to be the most serious urban air pollution problem and is consistently associated with adverse effects on human health. [PM10/PM2.5] are a mixture of solid and liquid particles of different origin, size and composition. They may also contain pollen grains as well as other allergen-carrying plant particles and mould spores. [PM10/PM2.5] are inhalable and can enter the lower airways, in the lung parenchyma (10, 22, 44-49).

Although the relationship between air pollution and the development of bronchial asthma in adults has been uncertain for years, recent data suggest that passive smoking and pollutants from primary emissions (combustion and non-combustion sources) may be linked to the development of BA in adults. The mechanisms of how pollutants induce respiratory disease are varied and recent evidence indicates that epigenetic changes in the respiratory epithelium and alterations in airway microbiota may explain some of the effects [PM2.5] at the alveolar level (10, 22, 44-49).

Pollen grains generally belong to the coarse fraction of fine airborne particles (ϕ ≤10 μ, [PM10]). Fragments of pollen grains are also found in fine airborne particles (ϕ ≤2.5 μ, [PM2.5]), which can penetrate deep through the respiratory tract into the lung alveoli.

Diesel exhaust particulate matter accounts for the bulk of particulate matter (up to 90%) in ambient air in the urban atmosphere. Anthropogenic pollutants, fine particulate air chemicals [PM10/PM2.5] and diesel exhaust particulate matter increase sensitisation to inhaled allergens.

Road traffic, with its emissions of gases and particles is currently – and is likely to remain for many years to come – the main contributor to air pollution in most urban areas, with negative effects on mortality from respiratory and cardiovascular diseases. In many geographical areas, fine particulate air pollution is significantly associated with increased mortality from respiratory diseases, exacerbation of allergic asthma, chronic bronchitis, respiratory tract infections and hospital admissions (10, 22, 45-49).

The WHO estimates that inhalation of particulate matter is responsible for 500,000 excess deaths each year worldwide (1). Seaton et al hypothesized that fine particles found in urban areas, by penetrating deep into the airways, are capable of inducing alveolar inflammation which is responsible for variation in blood coagulability and the release of mediators that promote acute episodes of respiratory and cardiovascular disease. This observation has been validated through research and clinical studies in the past but also more recently (10, 22, 45- 56).

In Air quality in Europe – 2020 report, the European Environment Agency reported that, in 2019, the majority of urban dwellers were exposed to concentrations of fine particulate matter with O. 2.5 μ [PM2.5] and ϕ ≤10 μ [PM10] with increased values above the WHO recommendations (74% and 42%, respectively) (Figure 5). Air pollutants interacting with epithelial surfaces can act as adjuvants promoting innate and adaptive pro-allergic immune reactions (57).

In Air quality in Europe – 2020 report, the European Environment Agency has also reported changes in concentrations (%) [PM10], which were attributed to lockdown restrictions in April 2020 (57) (Figure 6).

Climate change, atmospheric air pollution with trace elements from soil and aeroallergens

In an attempt to find an explanation for the acute respiratory effects associated with inhalable fine airborne particles, clinical studies have suggested the transition of heavy metals (including nickel) from airborne fine particles to the airways, thereby generating free radicals. Heavy metals (chromium, cobalt, copper, manganese, nickel and zinc) derived from various air samples from crowded urban areas or heavy road traffic have been linked to their activation in the airways as well as to lung damage (58).

Investigating the chemistry of heavy metals (including nickel) present in pollen grains was an important and necessary step to validate their impact on human health, on the prevalence and intensity of allergy, AR and BA symptoms in adults and children. Clinical studies have shown a direct link between air pollution and the loading of aeroallergenic plants such as common ragweed, with trace elements such as [Ni] (nickel). The uptake of [Ni] depends on plant species, and some of those, including aeroallergenic plants, show hyperaccumulation effects. Nickel, as an essential trace element for plants, animals and humans, belongs to a group of heavy metals. In the air quality guidelines for Europe, WHO describes [Ni] as a very hazardous residual metal for air, soil, plants and the human body, in addition to other heavy metals. Amounts of [Ni] exceeding the optimum values are toxic to the human body. The sum of the effects exerted by [Ni] and pollen grains in the airways makes allergic diseases, including AR and BA, more intense and more difficult to control medically (58).

In a clinical study, concentrations of nine heavy metals (Ni, Pb, Zn, Ba, Cd, Cr, Cu, Mn) were measured in common ragweed (as a pollen grain carrier plant) and the transfer of these trace elements from the soil to the roots of the plant (common ragweed), and subsequently to the pollen grains, was analysed. Soil, roots and pollen grains collected from this plant were taken from 26 urban sites. Soil pH, soil organic carbon and soil heavy metals were measured (58).

In the course of the determinations, trace element allocation within the common ragweed plant was always higher in the roots and less increased in the pollen grains. However, there were some exceptions at the urban site level, where a reverse pattern was observed, especially for [Ni], [Zn] and [Cu]. The data obtained showed that total Ni deposition in air was <60 μg/m². However, soil [Ni] content exceeded the maximum tolerated concentrations, ranging from 42 ìg/g to 150 ìg/g. The average [Ni] content in plants, measured per locality, ranged from 0.13 μg/g to 10.72 μg/g. Hyperaccumulation of [Ni] was obtained in common ragweed (10.72 ìg/g) (58).

Significant predictive models of heavy metal concentrations of pollen grains were obtained using soil or root properties of the common ragweed plant only for Ni, Cd and Pb. All of these involved positive relationships between heavy metal concentrations in pollen grains, their concentrations in soil and/or in plant roots. Estimates of short-term human exposure to increased heavy metal concentrations in pollen grains indicate an uptake of <50 ng, which is well below air quality criteria thresholds (58).

The role of monitoring heavy metal pollution is impressive, given the toxicity and accumulation events. Calculated per year, the harmful effects of heavy metals exceed the total damage from radionuclides and organic waste produced each year. Similar to other heavy metals, excessive concentrations of [Ni] disrupt Fe uptake and metabolism. Various natural processes and also human impact can increase [Ni] concentration. Anthropogenic activity, including the burning of fossil fuels, the operation of smelters and the frequency of traffic (Disel emissions), is the main source of [Ni] emissions. Exhaust gases from the combustion of fuel for a diesel engine contain more than 40 air pollutants, including nickel oxide, nickel sulphate and nickel subsulphide. All those compounds have a harmful effect on vegetation, while their genotoxicity and malignancy effects are also recorded. Of the total [Ni] present in the atmosphere, 20% has been associated in the past with road traffic in particular. There is evidence that people living near heavily trafficked roads show associated health deterioration also through allergic respiratory diseases. Air pollution is associated with exacerbation of bronchial asthma, increased hyper-responsiveness, increased use of medication, increased presentations to emergency services and increased hospital admissions due to respiratory allergic diseases (58). q

DISCUSSION

Lifestyle adjustments

Given the explosive global growth in urbanisation, heavy road and air traffic with significant gas emissions, industrial production, [CO₂] production and climate change, maintaining good air quality is, and will become, increasingly difficult. Outdoor air pollution and climate change are implicated in the increasing prevalence and severity of allergic respiratory diseases (AR and BA) (1-3, 10, 13, 22-24, 30-33, 42-45, 58). Unlike the action of outdoor pollutants, climate change affects the pollen grains of aeroallergenic plants by increasing their availability rather than by changing their chemical structure. Some of the harmful effects of climate change on respiratory health could also arise from this increased availability.

Exposure to environmental allergens is a risk factor for allergic respiratory diseases (AR and BA) in both adults and children, inducing more severe airway allergy phenotypes. In urban areas, people living in urban areas are more affected by respiratory allergic diseases than inhabitants of rural areas. People with atopy in these areas have been found to have increased airway responsiveness to aeroallergens (1-3, 10, 13, 22-24, 30-33, 42-45, 58).

Thus, lifestyle adjustments are important not only to mitigate the effects of air pollution and climate change on human health but also to reduce the occurrence and progression of respiratory allergic diseases.

Air quality alerts, pollen season calendars and allergic disease diaries represent good health monitoring tools which can be useful in planning outdoor activities and better managing exposure to common ragweed allergens.

On the one hand, a sensible approach to limiting outdoor time and outdoor exercise during pollen season (e.g., for patients allergic to common ragweed pollen), in time intervals with heavy traffic or on hot and very hot days is recommended. On the other hand, outdoor exercise is still recommended as its benefits are expected to outweigh the negative impact of exposure to ragweed allergens and outdoor pollutants, at least in most European cities.

Other measures aimed at reducing air pollution and its effects on human health include planting non-allergenic trees in urban areas; promoting public transport and reducing private transport in big cities (especially during periods of high aeroallergenicity of plants, such as June-October); controlling vehicle emissions, especially diesel.

In addition to outdoor air pollution and climate change, indoor pollution, particularly in urban dwellings (with the associated loss of biodiversity), can significantly influence exposure to a polluted environment. Adequate and regular ventilation of living spaces and indoor air filtration can prevent mould growth and reduce indoor [NO2] concentrations. Preventing high humidity and limiting the number of carpets can reduce mould in the living environment. People with an atopic predisposition should carefully consider the choice of keeping a pet. In countries around the world (including Romania), under pandemic restrictions for almost two years, some people with atopy have experienced an exacerbation of symptoms of respiratory illnesses (BA and AR) due to prolonged time spent in their homes due to isolation.

CONCLUSION

Further research is a step towards measures that can protect the population from exposure to a polluted environment and reduce the number of respiratory tract infections and allergic diseases and their treatment costs.

Conflict of interests: none declared.

Financial support: none declared.

FIGURE 1.

Interaction between climate change, air pollution, vegetation changes, abundance of pollutants, allergens and environmental adjuvants, which can lead to allergies and associated diseases (allergic rhinitis, atopic bronchial asthma, atopic dermatitis, food allergies), influencing the immune system and having a direct impact on human health (10)

FIGURE 2.

Relationship between anthropogenic factors, global climate change (increasing atmospheric [CO₂] concentration, increasing ambient air temperature and increasing frequency of heat waves), prevalence and severity of atopic allergic asthma and allergic rhinitis through impact on plant growth and pollen counts – schematic diagram. Adapted from "Is the Global Rise of Asthma an Early Impact of Anthropogenic Climate Change?", Paul John Beggs and Hilary Jane Bambrick (10)

FIGURE 3.

Observed annual mean temperature trend from 1850 to 2022 – global (left panel) and European (right panel) annual mean surface temperature anomalies from pre-industrial 1850 to 2022 (13-21) (https://www.eea.europa.eu/en/analysis/indicators/global-and-european-temperatures)

TABLE 1.

Effects of atmospheric air temperature and air pollutants on allergenicity and onset of pollen season (22)

FIGURE 4.

Change in total plant biomass as a function of days after sowing (DAS) for ragweed grown and changed at increased atmospheric [CO₂] concentrations in the pre-industrial period, the current period and in the 21st century to 2050. Relative growth rate (RGR) was determined between the 21st and 29th DAS. No other change in RGR was observed in [CO₂] concentration after 35 DAS indicating a significant increase in plant biomass. Taken from "Is the Global Rise of Asthma an Early Impact of Anthropogenic Climate Change?", Paul John Beggs and Hilary Jane Bambrick (10)

FIGURE 5.

Exposure of European urban dwellers to increased concentrations of fine particles with ϕ ≤2.5 μ [PM2.5] and O . 10 ƒÊ [PM10] in 2019 (57)

FIGURE 6.

Exposure of European urban dwellers to increased concentrations of fine particles with ϕ ≤2.5 μ [PM2.5] and ϕ ≤10 μ [PM10] in 2020 (57)