Air Pollution: How It Enters Our Bodies

Air pollution is a mix of hazardous substances from both human-made and natural sources. It is a major threat to global health, with 99% of the global population breathing air that exceeds WHO guideline limits. Air pollution can enter the body through the respiratory tract, with pollutants entering the lungs and, in some cases, the bloodstream. This can lead to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells throughout the body, impacting the lungs, heart, and brain, ultimately leading to disease. The health impacts of air pollution depend on the types, sources, and concentrations of pollutants, with certain groups being more susceptible to the effects of air pollution than others.

Pollutants enter the body through the respiratory tract

Air pollution is the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities and durations that can be harmful to human health. The main pathway of exposure to air pollution is through the respiratory tract.

When pollutants are inhaled, they can induce inflammation and irritation, which has been demonstrated in both animal and controlled human exposure studies. The extent of pulmonary inflammation depends on the particle dose and composition. For example, organic carbon particles and transition metals from combustion sources can elicit a strong inflammatory response. This inflammation increases the airways' responsiveness to irritants, such as allergens, and may reduce lung function by causing bronchoconstriction.

Particles with a diameter of 10 microns or less can lodge deep inside the lungs, causing irritation, inflammation, and damaging the lining of the respiratory tract. Smaller, more harmful particles, with a diameter of 2.5 microns or less, can penetrate the lung barrier and enter the bloodstream, affecting all major organs of the body. These tiny pollutants increase the risk of heart and respiratory diseases, lung cancer, and strokes. They can also cause asthma, bronchial symptoms, and lung inflammation, particularly in children and those with pre-existing asthma.

Constant exposure to elevated particle pollution will contribute to reduced respiratory function, even in healthy individuals. This is due to the gradual decline in physiological defences that occurs as a person ages, making older adults more susceptible to the effects of air pollution. Additionally, children, people with diabetes, and those of lower socioeconomic status are at greater risk of particle pollution-related health effects.

Pollutants can enter the bloodstream via the lungs

Air pollution is the presence of contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour. These contaminants are present in quantities that can be harmful to human health. The main pathway of exposure to air pollution is through the respiratory tract.

When we breathe in air pollutants, they can enter our bloodstream via the lungs and circulate throughout the body. This can lead to systemic inflammation and carcinogenicity. Some pollutants are large and coarse, and our body's natural defences help us to cough or sneeze these out. However, smaller particles, known as fine or ultrafine particles, can get trapped in the lungs. The smallest particles are so minute that they can pass through the lungs and directly enter the bloodstream, just like the essential oxygen molecules we need to survive.

These fine particles are an especially important source of health risk. They can penetrate deep into the lungs and travel to organs, causing systemic damage to tissues and cells. Fine particles are produced by mechanical and chemical processes that break down larger particles into smaller, more dangerous bits. Dust storms, construction and demolition, mining operations, and agriculture are among the activities that produce such particles.

Fine particulate matter in the air can aggravate lung disease, trigger asthma attacks and acute bronchitis, and may also increase the risk of respiratory infections. Over time, breathing in fine particles increases the chances of developing chronic obstructive lung disease (COPD), chronic bronchitis, cardiovascular disease, or lung cancer. Short-term exposure to high levels of particulate matter can lead to reduced lung function, respiratory infections and aggravated asthma.

Pollutants can cause inflammation and oxidative stress

Air pollution is the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities and durations that can be harmful to human health. The main pathway of exposure to air pollution is through the respiratory tract.

Oxidative stress can also trigger redox-sensitive pathways, leading to biological processes such as inflammation and cell death. In the early phase of inflammation, oxidative stress does not directly cause cell damage but can induce the transcription of stress defense genes, including antioxidant genes. However, the additional release of cell contents can amplify the inflammatory process and lead to tissue injury.

The health impacts of air pollution exposure depend on the types, sources, and concentrations of the pollutants. Vehicle emissions, particularly diesel exhaust particles (DEPs), are a major source of pollutants that can penetrate indoors and cause long-term and short-term health effects. Long-term exposure to high levels of these particles can increase the risk of cancer, respiratory diseases, and arteriosclerosis. Short-term exposure can exacerbate bronchitis, asthma, and other respiratory diseases, as well as cause changes in heart rate variability.

It is important to note that almost every organ in the body can be impacted by air pollution. Some pollutants are small enough to penetrate the bloodstream through the lungs and circulate throughout the entire body, leading to systemic inflammation and an increased risk of cancer. Maternal exposure to air pollution has also been associated with adverse birth outcomes, such as low birth weight and pre-term birth.

Pollutants can worsen respiratory conditions like asthma

Air pollution is a growing problem, with nine out of ten people now breathing polluted air, which kills around 7 million people annually. Almost every organ in the body can be affected by air pollution, and pollutants can enter the body in various ways. The primary route of exposure is through the respiratory tract, with pollutants inhaled from the atmosphere, including dust, fumes, gases, and smoke.

Additionally, nitrogen dioxide (NO2), a product of emissions from vehicles and power plants, can irritate the airways, making them more inflamed and increasing the risk of asthma attacks and COPD flare-ups. Sulphur dioxide (SO2), released from burning fossil fuels, transportation, and industrial processes, can cause coughing, tightness in the chest, and breathing difficulties. High levels of SO2 are linked to increased hospital admissions for asthma attacks. Fine particulate matter, a critical component of both ambient and household air pollution, can also trigger asthma symptoms.

The impact of air pollution on asthma is evident in studies conducted in areas with high particle pollution emissions. For example, in Utah Valley, hospital admissions for asthma decreased by nearly 50% when a steel mill, the primary source of local particle pollution, ceased operations for a year. When the mill resumed operations, hospital admissions for asthma increased. Similarly, indoor air pollution can also pose risks for people with asthma. Indoor sources of pollution include mould spores, cockroaches, dust mites, and poorly filtered air systems, which can spread allergens and irritants.

Pollutants can cause systemic inflammation and carcinogenicity

Air pollution is defined as the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities and durations that can be harmful to human health. The main pathway of exposure to air pollution is through the respiratory tract.

Air pollution can cause systemic inflammation. A growing body of research is showing how breathing polluted air impairs the immune system's ability to regulate inflammation, which can lead to other serious health conditions. Studies have shown higher levels of inflammatory molecules circulating in the blood of people with long-term exposure to different kinds of air pollution.

Due to their small size, some air pollutants can penetrate into the bloodstream via the lungs and circulate throughout the entire body, leading to systemic inflammation. A study in the Tel-Aviv Metropolitan area in Israel showed that healthy individuals with greater exposure to air pollution had higher levels of inflammatory biomarkers.

Air pollution can also cause carcinogenicity. Studies have shown that exposure to air pollution is linked to an increased risk of lung cancer. Maternal exposure to air pollution is also associated with adverse birth outcomes, such as low birth weight, pre-term birth, and small for gestational age births.

Overall, air pollution is a serious issue that can lead to a variety of health problems, including systemic inflammation and carcinogenicity. It is important to reduce air pollution and protect people from exposure to improve public health.

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