Allergies And Pollution: Understanding The Connection

The global prevalence of allergic diseases has increased, and urban air pollution has been identified as a significant environmental factor. This includes gaseous materials such as ozone and nitrogen dioxide, as well as particulate matter, which is generated by automobile traffic and industry. The effects of air pollution on human health are vast, with 7 million people dying prematurely each year. Air pollution alone causes allergic rhinitis in 40% of the world population, and it is also associated with the development of chronic allergic respiratory diseases, including asthma, chronic obstructive pulmonary disease, and inflammation of the airways.

Urban air pollution

Outdoor air pollutants, or 'irritants', are a major cause of allergies in people. These include gaseous materials such as ozone and nitrogen dioxide, as well as particulate matter, which is generated by automobile traffic and industry. The most abundant components of urban air pollution are found in areas with high levels of vehicle traffic. These include airborne particulate matter, nitrogen dioxide, and ozone. Fossil fuel combustion and greenhouse gas emissions from energy supply, transport, industry, and agriculture also contribute to climate change, which interferes with the seasonal presence of allergenic pollens in the atmosphere by prolonging these periods.

There is strong epidemiological evidence that air pollution exacerbates asthma and other allergic diseases. Recent studies have suggested that air pollutants play a crucial role in the development of asthma and allergies. Researchers have elucidated the mechanisms whereby these pollutants induce adverse effects; they appear to affect the balance between antioxidant pathways and airway inflammation. Damage to airway mucous membranes and impaired mucociliary clearance caused by air pollution may facilitate access of inhaled allergens to the cells of the immune system, thus promoting sensitization of the airway.

In addition, air pollution combines with pollen to drive allergies. Pollutants can attach to the surface of pollen grains and alter their allergenic potential, making pollen more allergenic by changing its elemental composition and increasing the total pollen count.

Climate change

The increase in global temperatures and carbon dioxide levels creates favourable conditions for plants to produce more pollen, exacerbating allergy symptoms such as sneezing, coughing, a runny nose, and itchy eyes. This phenomenon is not limited to specific regions, as initially believed, but is observed across diverse areas, including arid regions like Arizona and New Mexico, and places with less distinct seasons, such as California.

The impact of climate change on allergies is not limited to pollen and mould. Air pollution, which is exacerbated by climate change, contains fine particulate matter, a mix of solid and liquid droplets emitted from factories, power plants, and vehicles. These pollutants can directly harm cells or induce intracellular signalling pathways in sensitive individuals, increasing the severity of allergic reactions.

Furthermore, the interaction between air pollution and pollen can lead to worse health outcomes. Burning fossil fuels releases heat-trapping carbon dioxide and other air pollutants, which, in combination with pollen, can aggravate respiratory issues. This is particularly concerning for children, who are more susceptible to the effects of pollen and air pollution, and for individuals with asthma, who may experience shortness of breath, chest tightening, wheezing, and other asthma symptoms.

Pollutants and allergens

The global increase in the prevalence of allergic diseases is concerning. Urban air pollution has been identified as an important environmental and extrinsic etiologic agent. This includes gaseous materials such as ozone (O3) and nitrogen dioxide (NO2), as well as particulate matter (PM), which is generated by automobile traffic and industry.

Strong epidemiological evidence supports a relationship between air pollution and the exacerbation of asthma and other allergic diseases. Recent studies have suggested that pollutants play a crucial role in the development of asthma and other allergic disorders. Experimental studies have elucidated the cellular and molecular events that explain how these pollutants induce adverse effects in the respiratory system.

In addition, air pollution has been shown to increase exposure to aeroallergens, their concentration, and/or biological allergenic activity. For example, pollen in heavily polluted zones can express a larger amount of proteins described as being allergenic. Diesel exhaust particles (DEPs) can disrupt pollen particles, leading to the release of paucimicronic particles and their transport by air, thus facilitating their penetration of the human airways.

Furthermore, climate change can also lead to the increased output of pollen from plants. This, along with the increased duration of pollen and mould exposure, can lead to a higher risk of allergic sensitization in the exposed human population.

To manage allergies caused by air pollution, it is recommended to reduce exposure to air pollutants. If allergies are triggered, non-sedative antihistamines or nasal sprays may be used in consultation with a doctor.

Asthma and allergies

The Asthma and Allergy Foundation of America (AAFA) is a not-for-profit organisation that is the leading patient group for people with asthma and allergies. It offers a variety of educational programs, resources and tools for patients, caregivers, and health professionals.

Allergic asthma is the most common type of asthma. In the United States, about 25 million people have asthma, and of that group, approximately 60% have allergies. Allergies are one of the most common chronic diseases. An allergy occurs when the body's immune system identifies a substance as harmful and overreacts to it. The substances that cause allergic reactions are called allergens. Allergens can enter the body by being breathed in, swallowed, touched, or injected. They cause an allergic reaction because your body thinks they are harmful. The immune system releases various chemicals that cause inflammation, or swelling, and the squeezing of airways upon exposure to an allergen.

Allergens are the most common asthma trigger. Allergic asthma is most common in early childhood and steadily decreases through adulthood. Allergy-induced asthma symptoms can range from mild respiratory symptoms to severe asthma attacks. During an asthma attack, your airways will tighten, making it difficult to breathe. You may also feel chest pressure, wheeze and cough. The symptoms of an allergic asthma attack are the same as an asthma attack caused by something else. The difference between the two is the cause of the asthma attack. Possible allergens that can trigger allergic asthma include pet or animal fur, pee, saliva or dander (flakes of skin), pollen, mould, dust mites, and cockroaches. Food allergies may also trigger allergic asthma in some people.

In recent decades, the prevalence of allergic diseases has dramatically increased globally, particularly in industrialised societies. Genetic factors within populations usually do not change in such a short period, so researchers have postulated other causes for the increased prevalence of allergic diseases. These include the so-called 'hygiene hypothesis', which refers to a lack of immunological shift from Th2-dominant infantile states to Th1-dominant adult-type responses during the early period of life, as a result of decreased exposure to bacterial infection. Other researchers have focused on the role played by extrinsic agents, including air pollution. Urban air pollution has been attracting attention as an important environmental and extrinsic etiologic agent. This includes gaseous materials such as ozone and nitrogen dioxide, as well as particulate matter, which is generated by automobile traffic and industry. Strong epidemiological evidence supports a relationship between air pollution and the exacerbation of asthma and other allergic diseases.

Allergic respiratory disease

The exact mechanisms behind the rapid increase in ARD prevalence are not yet fully understood. However, urban air pollution has been identified as a significant environmental and extrinsic etiologic agent. Air pollutants such as ozone, nitrogen dioxide, and particulate matter produced by traffic and industrial activities are believed to play a crucial role in the development of ARD. Recent studies have elucidated the cellular and molecular events that explain how these pollutants induce adverse effects in the respiratory system.

The lung epithelial barrier is the first line of defence against environmental insults, and it responds to allergens by mounting a cascade of immune reactions that can lead to inflammation. Epithelial barrier dysfunction is an area of interest in researching the initial stages of allergic inflammation. Studies have found that exposure to certain inorganic mineral elements, such as nano-SiO2 particles, can exacerbate allergic inflammation by activating IgE-sensitized mast cells.

The clinical manifestations of ARD are heterogeneous, and individual airborne allergens can trigger specific clinical profiles. Aeroallergens are largely responsible for the clinical features and severity of ARD. The optimal approach to managing ARD involves a global assessment of rhinoconjunctivitis and asthma. Pharmacological treatment options for ARD include non-sedative antihistamines or nasal sprays, while Allergen Immunotherapy (AIT) is considered a valuable first-line treatment option as it can modify the prognosis of the disease.

Additionally, preventing exposure to air pollutants is crucial in managing ARD. This can be achieved through measures such as wearing disposable face masks, keeping windows closed, and using air conditioning to clear indoor air.

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