Air Pollution: A Toxic Path To Diseases

Air pollution is a major cause of disease and premature death worldwide. In 2019, the World Health Organization (WHO) reported that 99% of the global population breathes air that exceeds healthy levels, with low- and middle-income countries suffering the highest exposures. Both short- and long-term exposure to air pollution can lead to a wide range of diseases, including lung cancer, asthma, chronic obstructive pulmonary disease, cardiovascular disease, metabolic disorders, and neurological conditions. Certain groups, such as children, older adults, pregnant women, and people with pre-existing health conditions, are more susceptible to the health risks associated with air pollution. The sources of air pollution are diverse, including household combustion, motor vehicles, industrial facilities, and forest fires, and the health impacts depend on the types, sources, and concentrations of pollutants in the air.

Air pollution and respiratory diseases

Air pollution is a major risk factor for respiratory disease. It affects lung function and can trigger asthma and COPD exacerbations. Outdoor and indoor air pollution, including that from diesel-powered vehicles and heavy equipment, contributes to respiratory issues. People near high-density traffic or industrial sources, such as low-income and minority communities, are at higher risk. Air pollution can cause respiratory symptoms like coughing, wheezing, and shortness of breath, and it can aggravate pre-existing conditions like asthma and COPD.

COPD, or chronic obstructive pulmonary disease, is the most common cause of preventable respiratory deaths and the burden of disease attributable to air pollution exposure. Long-term exposure to air pollutants, including PM2.5, PM10, and NO2, increases the risk of COPD, especially in individuals with a high genetic risk and an unhealthy lifestyle. COPD is characterised by an enhanced chronic inflammatory response in the airways and lungs to noxious particles or gases.

Asthma is another respiratory disease strongly linked to air pollution. Air pollution can trigger asthma symptoms and flare-ups, particularly in children, who are more susceptible to particle pollution than adults with asthma. This may be due to anatomical factors leading to higher particle deposition in the tracheobronchial region of the lung in children. Increased exercise and time outdoors are also behavioural factors that contribute to children's heightened risk.

In addition to triggering symptoms, air pollution can also cause respiratory diseases. Studies have shown that long-term exposure to air pollution increases the risk of developing asthma and COPD. Certain air pollutants, such as nitrogen oxides, which primarily come from vehicle emissions, can irritate the airways and cause asthma. Other pollutants, such as sulphur oxides, which come from the combustion of fossil fuels, can inflame the airways and increase the risk of chronic bronchitis.

To mitigate the health impacts of air pollution, regulatory and technological innovations are necessary to enhance air quality. Additionally, policies and interventions aimed at improving healthcare access and social support can help reduce the vulnerability of populations to the adverse health effects of air pollution.

Air pollution and lung diseases

Air pollution is a major global public health problem, affecting both developing and developed countries. It is a growing threat to public health, with nine out of ten individuals living in urban areas affected by it. Exposure to air pollution has been linked to a variety of respiratory health effects and lung diseases.

Particle pollution, also known as particulate matter (PM) or soot, is a significant contributor to air pollution and has been linked to adverse effects on the respiratory system. These particles are a mixture of tiny bits of solids and liquids in the air we breathe and can be produced by factories, power plants, and vehicles. The most damaging particles are the smaller 'fine' particles (PM10 and PM2.5) and ultrafine particles, which can reach the breathing sacs in the lungs and even cross into the bloodstream. These particles can carry toxic chemicals linked to cancer. Exposure to PM has been associated with a decrease in pulmonary function, an increase in respiratory infections, and a higher prevalence of childhood asthma.

Ozone pollution is another concern, as it can cause lasting damage to respiratory health. Short- and long-term exposure to ozone can lead to inflammation and oxidative stress, not only damaging the lungs but also impacting other parts of the body, including the central nervous system and reproductive functions. High ozone levels are associated with an increased risk of pneumonia and bronchitis, and more people with asthma are admitted to hospitals during these times.

Air pollution has also been linked to an increased risk of lung cancer, with ambient air pollution, specifically PM and NO2, showing a positive correlation. Additionally, research has found somatic genomic mutations attributed to household air pollution in patients with lung cancer.

Certain groups are more vulnerable to the effects of air pollution, including children, older adults, and people with pre-existing lung conditions such as asthma and chronic obstructive pulmonary disease (COPD). Lower-income individuals and people of color are also disproportionately affected by air pollution, putting them at higher risk for illness.

Overall, air pollution has significant detrimental effects on lung health, contributing to respiratory issues, exacerbating lung diseases, and increasing the risk of lung cancer.

Air pollution and cardiovascular diseases

Air pollution is a major environmental health risk and the leading cause of death worldwide, with over 20 million deaths each year. It is responsible for several million premature deaths globally every year, and in 2015, outdoor air pollution was ranked as the fifth biggest risk factor for all-cause disease. Cardiovascular disease (CVD) is the leading cause of death globally, with 17.9 million deaths annually.

There is a clear link between air pollution and cardiovascular disease. Both short and long-term exposure to air pollution has been shown to increase hospitalizations for serious cardiovascular events, particularly in people with pre-existing heart disease. People with chronic heart disease may experience symptoms such as impaired vascular function, raised blood pressure, alterations in cardiac rhythm, blood clotting disorders, coronary artery disease, and stroke following exposure to fine particulate matter. The risk of death is greater from long-term exposure.

The sources of air pollution that lead to these health issues include traffic, factories, power generation, wildfires, and cooking with a wood stove. One of the most common indoor sources is smoking, which is dangerous both to the smoker and those exposed to secondhand smoke. Secondhand smoke has been linked to cardiovascular disease, heart disease, stroke, and sudden infant death syndrome.

The impact of air pollution on cardiovascular health is particularly prominent in certain regions. The Western Pacific region saw the highest number of deaths from heart disease and stroke due to outdoor air pollution, with nearly 1 million deaths in 2019. In Southeast Asia, Africa, and the Eastern Mediterranean, air pollution concentrations are nearly ten times higher than the recommended levels.

While the respiratory effects of air pollution have been recognized for decades, cardiovascular disease has recently been cemented as a significant consequence of air pollution. Scientific evidence indicates that populations exposed to high levels of PM2.5 may be at an increased risk of health effects, including cardiovascular outcomes.

Pharmacological interventions may be able to prevent or reverse the cardiovascular effects of air pollution. However, the fundamental approach to this problem is prevention, and initiatives to limit harmful substances and reduce air pollution are essential to mitigate the risk.

Air pollution and neurological development

Air pollution is a major cause of disease and premature death. In 2019, exposure to PM2.5 led to 175,702 years lived with disability (YLDs) due to chronic obstructive pulmonary disease in 30 European countries. The same year, 12,253 people across 23 European countries were hospitalised due to lower respiratory infections caused by acute exposure to ozone.

Air pollution is also associated with an increased risk of neurological disorders, including neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. The link between air pollution and neurological diseases lies in the interplay between oxidative stress and inflammation. Pollutants, including particulate matter (PM), nitrogen oxides (NOx), and polycyclic aromatic hydrocarbons (PAHs), are known to generate reactive oxygen species (ROS), which trigger an immune response that can harm cellular structures. This oxidative stress plays a pivotal role in the development of neurodegenerative disorders.

Prolonged exposure to air pollution can also alter gene expression related to the integrity and functionality of the blood-brain barrier (BBB), increasing its permeability. Research indicates that PM can induce apoptosis in neuronal cells and hinder the differentiation of neural stem cells, which are essential for neuron development and brain function. Animal studies suggest a link between air pollution exposure and brain damage, including neuron death and the formation of neurofibrillary tangles, a hallmark of Alzheimer's disease.

In addition, air pollution has been linked to cognitive decline and mental health issues, such as depression and anxiety disorders. Components of air pollution, such as nitrogen oxides, PM, and sulfur dioxide, can induce oxidative stress, leading to inflammation in the brain and subsequent structural changes that may cause depressive symptoms.

The effects of air pollution on neurological development are particularly concerning in children, as their brains are still developing. Studies have shown that children living in areas with high levels of air pollution exhibit adverse short and long-term health outcomes, including detrimental effects on brain development.

Air pollution and pregnancy

Air pollution is a major environmental health risk and cause of premature death and disease. It is associated with oxidative stress, inflammation, and impaired lung function, which can lead to a range of diseases, including respiratory illnesses, cardiovascular disease, and cancer.

Pregnant women and their infants are particularly vulnerable to the effects of air pollution due to their unique physiology. During pregnancy, physiological changes occur, including increased oxygen consumption, ventilation, and cardiac output, which increase the amount of pollutants inhaled and circulated, thereby increasing exposure.

Maternal exposure to air pollution has been associated with adverse birth outcomes, such as low birth weight, pre-term birth, small for gestational age births, and infant mortality. It can also impact the mother's health, with links to maternal hypertensive disorders and postpartum depression.

The health risks are influenced by the types, sources, and concentrations of pollutants, as well as individual factors such as genetics, comorbidities, and sociodemographic factors. The worst pregnancy outcomes attributed to air pollution exposure include stillbirth and spontaneous abortion (miscarriage).

There is also growing evidence that air pollution may affect the long-term health of the child, with potential links to diabetes and neurological development. The Developmental Origins of Health and Disease hypothesis suggests that a fetus's early experiences and susceptibility to environmental elements can impact how diseases manifest later in life.

Urgent action is required to reduce air pollutants and protect the health of pregnant women and their infants, both currently and for future generations.

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