Air Pollution: Health Hazards And Risks

Air pollution is a major threat to global health and prosperity, causing more than 6.5 million deaths each year. It is a mix of hazardous substances from both human-made and natural sources, including vehicle emissions, fuel oils, natural gases, manufacturing by-products, and fumes from chemical plants. The main pathway of exposure is through the respiratory tract, leading to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells, impacting the lungs, heart, and brain, among other organs. The pollutants with the strongest evidence for public health concerns include particulate matter (PM), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2). Exposure to these pollutants has been linked to a range of health problems, including respiratory infections, heart disease, stroke, lung cancer, asthma, and adverse pregnancy outcomes.

Ozone, a powerful lung irritant, can cause respiratory issues, including asthma

Ozone, a colourless gas, is a powerful lung irritant and a major air pollutant. When inhaled, ozone reacts with the lining of the airways, causing inflammation and other damage that can impact multiple body systems. Ozone exposure can cause serious short-term and long-term health effects, including respiratory issues such as asthma.

Ozone pollution is particularly harmful to people with asthma, a chronic respiratory disease. Asthma is a condition characterised by reversible airway obstruction and immunologic sensitivity to allergens. Ozone exposure can worsen asthma symptoms and increase the probability of asthma exacerbations, leading to more frequent hospital admissions. Studies have found that children with asthma experience increased asthma symptoms and medication use on days with high ozone levels.

Ozone exposure is also associated with an increased risk of developing asthma. Children who play outdoor sports and live in high-ozone communities are more likely to develop asthma. This is particularly concerning as children are more likely to be active outdoors when ozone levels are high, increasing their exposure. Additionally, children with developing lungs are more susceptible to the harmful effects of ozone, which can cause long-term respiratory damage.

The harmful effects of ozone are not limited to asthma. Ozone exposure can cause respiratory issues in healthy individuals as well, including chest tightness, coughing, and shortness of breath. These symptoms can occur within hours of exposure and may lead to emergency department visits. Long-term exposure to ozone is linked to an increased risk of respiratory disease mortality.

Overall, ozone is a significant air pollutant that poses a serious threat to respiratory health. Its powerful irritant effects on the lungs can cause and exacerbate respiratory issues, including asthma. Certain groups, such as children and people with pre-existing respiratory conditions, are especially vulnerable to the harmful effects of ozone pollution.

Air pollution is linked to an increased risk of cancer, including lung cancer

Air pollution is a mix of hazardous substances from both human-made and natural sources. It is a major threat to global health and prosperity, causing more than 6.5 million deaths each year. The main pathway of exposure from air pollution is through the respiratory tract. Breathing in these pollutants leads to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells throughout the body, impacting the lungs, heart, and brain, among other organs, and ultimately leading to disease.

In 2013, the International Agency for Research on Cancer of the World Health Organization (WHO) classified air pollution as a human carcinogen. Studies have established that short-term exposure to higher levels of outdoor air pollution is associated with reduced lung function, asthma, cardiac problems, and hospital admissions. Mortality rates related to air pollution are a significant concern. Exposure to the air pollutant PM2.5 is associated with an increased risk of death.

Lung cancer is the number one cancer killer of both men and women in the US. Overwhelming evidence shows that particle pollution in the outdoor air—from vehicle exhaust, coal-fired power plants, and other industrial sources—can cause lung cancer. Particle pollution increases the risk of dying early, heart disease, and asthma attacks, and it can also interfere with the growth and function of the lungs.

A new mechanism has been identified through which very small pollutant particles in the air may trigger lung cancer in people who have never smoked. These particles are typically found in vehicle exhaust and smoke from fossil fuels and are associated with non-small cell lung cancer (NSCLC), accounting for over 250,000 lung cancer deaths globally per year.

In addition to lung cancer, air pollution has been linked to an increased risk of several other types of cancer, including breast, liver, and pancreatic cancer. A study of 66,280 residents of Hong Kong aged 65 or older found that long-term exposure to ambient fine particulate matter increased the risk of mortality for these types of cancer.

Exposure to air pollution during pregnancy is associated with adverse birth outcomes

Air pollution is a mix of hazardous substances from both human-made and natural sources. It is a major threat to global health and prosperity, causing more than 6.5 million deaths annually. The main pathway of exposure is through the respiratory tract, leading to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells, impacting the lungs, heart, and brain, among other organs.

Pregnant individuals are particularly vulnerable to the adverse effects of air pollution. Exposure to air pollution during pregnancy has been associated with an increased risk of adverse birth outcomes. These outcomes include low birth weight, pre-term birth, and small for gestational age births. The risk of low birth weight is further exacerbated by preterm birth, as the baby may not have sufficient time to develop in the womb.

Several studies have investigated the impact of air pollution on pregnancy outcomes. One study in Durban, South Africa, found that exposure to PM2.5, SO2, and NOx had significant direct and indirect effects on adverse birth outcomes. Similarly, elevated prenatal exposure to PM2.5 was positively associated with low birth weight, preterm birth, and small for gestational age. Another study in Kansas, US, reported significant relationships between higher ozone (O3) exposure during pregnancy and an increased risk of preterm birth, decreased birth weight, and gestational hypertension.

The negative consequences of air pollution exposure during pregnancy extend beyond birth outcomes. There is evidence that air pollution exposure may affect neurological development in children, with potential links to an increased risk of autism, ADHD, and high blood pressure in early life.

Overall, the available research highlights the significant risks associated with air pollution exposure during pregnancy, underscoring the importance of mitigating air pollution and providing guidance to pregnant individuals to minimize their exposure.

Pollutants can cause inflammation and oxidative stress, impacting the lungs, heart, and brain

Air pollution is a major threat to global health and prosperity, causing more than 6.5 million deaths each year worldwide. It is the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities that can be harmful to human health.

The main pathway of exposure to air pollution is through the respiratory tract. Pollutants cause inflammation and oxidative stress, which have a detrimental impact on the lungs, heart, and brain, ultimately leading to disease.

Impact on the lungs

Oxidative stress is a driving force behind the toxicity of airborne pollutants in the lungs. Most airborne pollutants are associated with intrinsic oxidative potential and stimulate the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). These can cause irreversible damage to critical biomolecules such as lipids, proteins, and DNA, as well as initiating pathogenic cellular processes.

Airborne pollutants can overwhelm the lung's antioxidant defences, causing oxidative injury. This can lead to various pathogenic cellular processes, including inflammation, cell death, and mucus hypersecretion, which are linked to the development and progression of lung diseases.

COPD, for example, is a disease characterised by abnormal lung inflammation, irreversible airflow limitation, and lung damage. It is caused primarily by tobacco smoking, but exposure to indoor and outdoor air pollutants is also a significant factor, especially in developing countries.

Impact on the heart

Air pollution exposure has been linked to cardiac problems and is a risk factor for all-cause mortality. Specific diseases associated with air pollution include ischaemic heart disease, chronic obstructive pulmonary disease, and stroke.

Impact on the brain

Air pollution has been linked to adverse pregnancy outcomes, including low birth weight and an increased risk of autism. Prenatal exposure to air pollution may also play a role in the development of neurobehavioural problems in childhood, such as ADHD.

Additionally, exposure to PM2.5, even at low levels, may alter the size of a child's developing brain, increasing the risk for cognitive and emotional problems in adolescence.

Other health impacts

Air pollution has also been linked to an increased risk of cancer, pneumonia, cataracts, diabetes, and neurological diseases. It can also cause systemic inflammation and impact almost every organ in the body.

Air pollution disproportionately affects low-income communities and minority populations

Air pollution is a mix of hazardous substances from both human-made and natural sources. It is a major threat to global health, causing more than 6.5 million deaths each year worldwide. The health problems associated with air pollution include respiratory issues, oxidative stress, inflammation, immunosuppression, and mutagenicity in cells, impacting the lungs, heart, and brain, ultimately leading to diseases such as stroke, ischaemic heart disease, chronic obstructive pulmonary disease, lung cancer, pneumonia, and asthma.

Unfortunately, the burden of air pollution is not shared equally. Low-income communities and minority populations are disproportionately affected by air pollution due to systemic racism and environmental injustice. Studies have found that non-Hispanic blacks, Hispanics, and Asians are more likely to live in areas with higher particle pollution and ozone pollution. Racial and ethnic minorities living in poorer areas are more exposed to environmental hazards, particularly air pollution. This is due to a combination of factors, including the placement of polluting facilities, a lack of emissions regulations, and the political power of large emitters.

For example, a California study revealed that over 30 years, 245 toxic polluting facilities were deliberately placed in poor communities, particularly in neighbourhoods in Houston, Texas, and along the Mississippi River in Louisiana, dubbed "Cancer Alley". These vulnerable communities were targeted due to their lack of resources and political power to oppose the siting of these facilities. As a result, the residents in these areas are exposed to higher levels of pollutants, increasing their health and environmental risks.

Additionally, low-income individuals are more likely to live in close proximity to sources of pollution, such as busy roads and industrial areas, and have fewer resources to relocate. Poverty and the issues prevalent in low-income communities, such as a lack of safety, green spaces, and access to healthy food, contribute to increased psychosocial distress and chronic stress, making residents more susceptible to the health impacts of air pollution.

The health consequences of air pollution exposure are severe for low-income communities and minority populations. Studies have found a greater risk of premature death from fine particle pollution in these groups. Maternal exposure to air pollution is also associated with adverse birth outcomes, such as low birth weight, preterm birth, and an increased risk of autism and neurobehavioural issues in children. Furthermore, air pollution exacerbates existing health disparities, as people of colour are more likely to have chronic conditions that make them more susceptible to the impacts of air pollution, including asthma and diabetes.

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