Air Pollutants: Asthma Triggers And How To Avoid Them

Air pollution is a serious issue that has been linked to the development and exacerbation of asthma, a chronic respiratory disease that affects over 23 million Americans. Outdoor air pollution, which comes from both human activity and natural sources, can trigger asthma attacks and worsen symptoms in those already suffering from the condition. Ground-level ozone, a common air pollutant, is particularly harmful, as it irritates the lungs and airways, causing inflammation and respiratory issues. Other pollutants, such as nitrogen dioxide (NO2), sulphur dioxide (SO2), and carbon monoxide (CO), also contribute to asthma development and exacerbation. Studies have shown that air pollution can cause oxidative injury to the airways, leading to inflammation and an increased risk of sensitisation to allergens. Additionally, indoor air pollution, caused by allergens and volatile organic compounds (VOCs), can also trigger and worsen asthma symptoms. Understanding the link between air pollution and asthma is crucial for developing effective preventive strategies and reducing the health burden associated with this disease.

Ground-level ozone

Ozone (O3) is a highly reactive gas molecule composed of three oxygen atoms. While the ozone layer in the upper atmosphere protects us from harmful ultraviolet radiation, ground-level ozone is harmful to human health. It irritates and damages the airways and lungs, exacerbating respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD). People with asthma are particularly vulnerable to the effects of ozone exposure, and high ozone levels can trigger asthma attacks and worsen symptoms.

Studies have found that on days with elevated ozone levels, hospital admissions for asthma and related emergencies increase, especially during the warmer seasons. This is particularly concerning for children with asthma, as they tend to spend more time outdoors and engage in physical activities, increasing their exposure to ground-level ozone. Research also suggests that long-term exposure to ozone may contribute to the development of asthma, even at low levels.

The impact of ground-level ozone pollution is not limited to respiratory health. Long-term exposure to ozone has been linked to various adverse health effects, including increased respiratory and cardiovascular mortality, metabolic disorders, nervous system issues, and reproductive problems. Additionally, certain indoor pollutants can increase the lungs' responsiveness to ground-level ozone, further exacerbating its harmful effects.

To mitigate the health risks associated with ground-level ozone, it is essential to monitor air quality and take proactive measures to reduce ozone pollution. This includes reducing emissions from vehicles, industries, and power generation, as well as implementing measures to protect vulnerable individuals, such as children and people with pre-existing respiratory conditions.

Nitrogen dioxide

NO2 is harmful to the respiratory system and can cause a range of adverse health effects. It can irritate the airways and lungs, leading to respiratory problems such as asthma. Exposure to NO2 can trigger asthma attacks and worsen existing asthma symptoms, particularly in children and individuals with pre-existing respiratory conditions. Studies have found associations between elevated NO2 levels and adverse health outcomes, including respiratory issues, lung and heart harm, and increased risk of asthma.

Indoor sources of NO2, such as unflued gas heating appliances and natural gas stoves, can also contribute to harmful levels of NO2 exposure. Inadequate ventilation can cause NO2 levels to build up indoors, posing a risk to respiratory health, especially for children and individuals with asthma.

While air quality has improved in recent years due to stricter regulations and cleaner technologies, many people still breathe unhealthy levels of NO2. Reducing NO2 emissions and exposure is crucial for protecting public health, especially for vulnerable populations susceptible to the harmful effects of air pollution, including individuals with asthma.

Sulphur dioxide

Asthma is a serious and life-threatening chronic respiratory disease that affects the quality of life of over 23 million Americans. People with asthma are at greater risk from breathing in small particles and irritating gases. Air pollution can make asthma symptoms worse and trigger asthma attacks.

One of the main air pollutants that cause asthma is sulphur dioxide (SO2). Sulphur dioxide is a harmful gas emitted during the burning of fossil fuels, transportation, and industrial processes. It is also released by natural sources such as volcanoes. Sulphur dioxide causes a range of issues for the lungs, including wheezing, shortness of breath, and chest tightness. These symptoms are especially prominent during exercise or physical activity when rapid breathing helps SO2 reach the lower respiratory tract. Long-term exposure to high levels of SO2 increases respiratory symptoms and reduces lung function.

Even short exposures to peak levels of SO2 in the air can trigger breathing difficulties for people with asthma when they are active outdoors. This leads to an increased risk of hospital admissions, especially among children, older adults, and people with asthma. Individuals living or working near ports, smelters, and other sources of sulphur dioxide are at the highest risk of exposure to SO2.

The impact of sulphur dioxide on asthma is a significant health concern. While levels of SO2 have improved over time due to policies promoting cleaner fuels and pollution controls on power plants, it remains a critical issue. High levels of SO2 can still occur due to malfunctioning equipment or during the start-up and shutdown of polluting sources such as power plants.

It is important for individuals to be aware of days with unhealthy levels of air pollutants and to take necessary precautions. Additionally, advocating for the cleanup of air pollution and the implementation of policies to reduce sulphur dioxide emissions is crucial for improving air quality and protecting the health of those affected by asthma.

Oxidative injury to airways

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodelling. There is a strong link between asthma and air pollution, with pollutants causing and exacerbating asthma symptoms.

Oxidative injury to the airways is a key mechanism by which air pollutants cause asthma. This occurs when there is an imbalance between the reducing and oxidizing systems, favouring a more oxidative state. Endogenous and exogenous reactive oxygen species (ROS), such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, play a significant role in airway inflammation. These ROS interact with biological systems, forming compounds that can damage proteins, lipids, and other molecules in the airways. For example, the reaction between superoxide anion and nitric oxide (NO) forms peroxynitrite, a potent ROS that can damage enzymes and proteins. Higher levels of NO are associated with a higher risk of asthma and increased severity.

Additionally, ROS can react with lipids, releasing isoprostane and ethane. Consequently, 8-isoprostane, a biomarker of lipid peroxidation, is often elevated in the exhaled breath condensate of individuals with asthma. This indicates ongoing oxidative stress and injury to the airways. Furthermore, studies have shown that urinary levels of bromotyrosine and F2-isoprostanes are also elevated in patients with asthma, further supporting the role of oxidative injury in the development of asthma.

Oxidative stress in the airways is not limited to adults; there is evidence of its presence in children with asthma as well. A study on children with mild to moderate asthma found that malondialdehyde, an indicator of oxidative stress, was present in their exhaled breath condensate. This suggests that oxidative injury to the airways occurs across all ages in individuals with asthma.

The imbalance between oxidizing and reducing systems also results in decreased antioxidant defences in individuals with asthma. Antioxidants such as superoxide dismutase, catalase, and glutathione are reduced, further contributing to the oxidative state and subsequent airway inflammation. This decrease in antioxidant defences is a crucial factor in the development and severity of asthma.

Air pollution and childhood asthma

Air pollution is a mix of solid particles and gases in the air. It can occur indoors and outdoors, and it can be caused by both natural and human-made factors. Outdoor air pollution is often caused by primary pollutants emitted directly into the atmosphere, such as from traffic and power generation, as well as secondary pollutants formed by chemical reactions in the air.

Several studies have found a link between air pollution and asthma, a serious and life-threatening chronic respiratory disease. Air pollution can worsen asthma symptoms and trigger asthma attacks, particularly in the estimated six million children in the United States with asthma, who are especially vulnerable to air pollution.

Ground-level ozone, a common air pollutant, is a known asthma trigger. Ozone is helpful in the upper atmosphere, but it causes problems when found at ground level, as it is irritating to the lungs and airways. Ground-level ozone is often found in cities with more cars and the use of fossil fuels, and during the summer when there is more sunlight, heat, and low winds. Other air pollutants that can trigger asthma include nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), and methane (CH4).

Research has also found a link between air pollution and the development of asthma. A large population-based birth cohort study found a positive association between perinatal exposure to air pollution and asthma incidence during preschool years. Additionally, two independent meta-analyses showed a connection between prenatal exposure to air pollutants and the later development of childhood asthma. Furthermore, air pollution may impact DNA associated with asthma, as evidence suggests that air pollutants can suppress genes that regulate the immune system, leading to an increased risk of developing asthma.

To minimize the impact of air pollution on children with asthma, it is recommended to pay attention to pollution levels and limit outdoor activities when air quality is poor. Running the air conditioning can also help reduce exposure to outdoor pollutants. Parents can also talk to their doctors about adjusting their child's asthma medication during periods of high air pollution.

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