Air Pollution's Asthma-Inducing Effects

Air pollution is a major contributor to asthma, a chronic respiratory disease characterised by variable airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. Both outdoor and indoor air pollution can increase the risk of developing asthma and worsen symptoms for those already affected. Pollutants in the air irritate the airways, causing swelling and tightening, and making it difficult to breathe. People with asthma are particularly vulnerable to the effects of air pollution, and certain groups, such as children and African American adolescents, are at an even higher risk of adverse health outcomes.

Ozone and particulate matter

Ozone is a gas that is helpful in the upper atmosphere, but when it is found closer to the ground in the air we breathe, it becomes a common air pollutant. Ground-level ozone is part of "smog" or haze and is most common in cities with more cars and higher fossil fuel usage. It is also more prevalent in the summer due to more sunlight, heat, and low winds. Ground-level ozone is created by chemical reactions between emissions of burning fuel and volatile organic compounds (VOCs), heat, and sunlight.

Ozone is an air pollutant that irritates the lungs and airways, triggering asthma and worsening respiratory diseases such as chronic obstructive pulmonary disease (COPD). People with asthma are advised to avoid outdoor activities, especially strenuous ones, on days with high ozone levels. Long-term exposure to ozone may also play a role in the development of asthma, according to some epidemiological studies.

Particulate matter, or PM, refers to small airborne particles found in haze, smoke, soot, and airborne dust, which can lead to serious air quality problems. The smallest particles, known as PM2.5, are the most harmful as they can penetrate deep into the lungs and even enter the bloodstream. PM10, which includes particles with a diameter of less than 10 μm, is also of concern, especially for individuals with asthma, who should ideally reside at least 300 meters away from major roadways to avoid exposure.

Transition metals, polycyclic aromatic hydrocarbons, and environmentally persistent free radicals are constituents of PM that may trigger phenotypic changes associated with asthma. Exposure to PM has been linked to increased inflammation, mucus hypersecretion, and asthma-like symptoms. Several studies have found a positive relationship between PM exposure and asthma incidence, especially in children. Prenatal exposure to particulate matter has also been associated with an increased risk of childhood asthma.

Nitrogen dioxide

NO2 is harmful to the respiratory system and can cause a range of adverse health effects, particularly for people with asthma. Exposure to NO2 can irritate the airways and worsen asthma symptoms, leading to more frequent coughing and wheezing, increased medication use, and a higher risk of hospital admissions. Evidence suggests that NO2 exposure is a significant risk factor for asthma development, especially in children. Higher levels of indoor NO2, such as from unflued gas heating, have been associated with an increased prevalence of respiratory symptoms and adverse effects on lung function in children with asthma.

Outdoor air quality has improved in recent years due to stricter standards and cleaner power plants, industrial sites, and vehicles. However, indoor NO2 levels can also build up to unhealthy levels, particularly from appliances that burn natural gas, liquefied petroleum gas, or kerosene without proper ventilation. People with pre-existing medical conditions, such as asthma, and those living near emission sources, are at higher risk of experiencing the harmful effects of NO2 pollution.

Studies have found associations between NO2 exposure and alterations in genes related to immune tolerance, providing insights into the epigenetic effects of air pollutants and potentially informing the development of preventative treatments for asthma. Overall, reducing NO2 exposure, especially indoors, is crucial for improving respiratory health and reducing the burden of asthma.

Carbon monoxide

Air pollution is a major public health problem, and it can have a significant impact on asthma outcomes. Asthma is a chronic respiratory disease characterised by variable airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. Evidence suggests that air pollution negatively impacts asthma in both adults and children.

Several studies have linked carbon monoxide exposure to asthma exacerbations, particularly in adults. Research has shown that short-term and long-term exposure to carbon monoxide can alter genes involved in immune tolerance, and these alterations are significantly associated with asthma. These genetic changes may suppress the immune system's ability to differentiate allergens from dangerous foreign substances, triggering an inflammatory response that leads to asthma.

Additionally, carbon monoxide exposure can irritate the airways, making asthma symptoms worse. People with asthma are at greater risk from breathing in irritating gases like carbon monoxide, especially when the Air Quality Index (AQI) is high. On high air pollution days, individuals with asthma should limit their time outdoors and avoid strenuous activities to minimise their exposure to harmful pollutants.

While the exact mechanisms are still being studied, the available evidence highlights the urgent need to establish prevention strategies and improve air quality to reduce the health burden of asthma caused by carbon monoxide and other air pollutants.

Genetic susceptibility

While the exact causal relationship between air pollution and asthma remains controversial, there is increasing evidence that air pollution contributes to the onset and exacerbation of asthma. Furthermore, it has been established that people with asthma are at greater risk from breathing in small particles and irritating gases found in air pollution.

In addition to genetic factors, prenatal and early postnatal stages are critical periods of susceptibility to environmental exposures that may contribute to the development of asthma later in life. Maternal smoking during pregnancy and exposure to indoor air pollution, particularly particulate matter (PM), have been associated with reduced lung function in infants and an increased risk of respiratory issues. The impact of genetic susceptibility may also vary depending on ancestry, with infants of Black African ancestry showing higher susceptibility to the negative effects of prenatal exposure to air pollution.

To reduce the burden of asthma, it is essential to identify genetically susceptible individuals and implement strategies to decrease their exposure to air pollution. Dietary interventions, such as antioxidant supplementation, have been proposed as a potential approach to reducing susceptibility to air pollution. Additionally, public health measures and policy changes aimed at improving air quality, especially in highly polluted areas, are crucial for protecting vulnerable individuals.

While the interaction between genetics and environmental factors is complex, ongoing research continues to enhance our understanding of genetic susceptibility to air pollution in the context of asthma. By integrating genetic knowledge with environmental considerations, we can better prevent and manage asthma, particularly in susceptible individuals.

Air quality and asthma management

Asthma is a chronic respiratory disease characterised by variable airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. It is the most common chronic respiratory disease and a major public health problem.

The causal relationship between air pollution and asthma remains controversial, but an increasing number of studies have provided consistent evidence of the involvement of air pollutants in the onset and exacerbation of asthma. Air pollution can increase the risk of developing asthma and worsen symptoms for those who already have it. Small airborne particles, found in haze, smoke, soot, and airborne dust, can lead to serious air quality problems. These small particles are called "particulate matter" or PM, with the smallest particles (PM2.5) being the most dangerous as they can penetrate deep into the lungs and even enter the bloodstream.

Ozone, a common air pollutant, is particularly problematic when found in the lower atmosphere, where it is a major component of smog. Ground-level ozone is more common in cities with more vehicles and greater fossil fuel usage. It is extremely irritating to the lungs and airways, triggering asthma symptoms. Nitrogen dioxide (NO2), another pollutant, is associated with a higher risk of developing asthma, especially in children. Other pollutants such as sulfur dioxide (SO2), carbon monoxide (CO), and methane (CH4) also negatively impact health.

To manage asthma and reduce the impact of air pollution, several measures can be taken. These include:

• Using close-fitting N95 facemasks when air pollution levels are high
• Opting for active travel, such as cycling or walking, instead of motorised transport
• Choosing low-traffic routes or those with open spaces
• Keeping car windows closed and maintaining the vehicle's air filtration systems
• Staying indoors and limiting outdoor activities during periods of poor air quality, especially from 11 a.m. to 8 p.m.
• Running the air conditioning when indoors to improve air quality
• Improving indoor air quality by using air cleaners, venting gas appliances, and avoiding wood fires
• Increasing medication during periods of high air pollution
• Removing or reducing allergens, preventing mould growth, and avoiding scented products at home
• Smoking cessation, especially for patients with asthma, to improve symptom control and lung function

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