Air Pollution: A Silent Killer's Deadly Reach

Air pollution is a major cause of death and disease worldwide, with an estimated 7 million deaths attributed to it annually. In 2021, this number rose to 8.1 million, making it the second-leading risk factor for death globally, including for children under five. The World Health Organization (WHO) has found that 99% of the global population breathes air that exceeds its guideline limits and contains high levels of pollutants, with low- and middle-income countries suffering the highest exposures. Fine particulate matter (PM2.5) is the air pollutant driving the most significant health problems and premature mortality, with emissions coming from the burning of fossil fuels and biomass in sectors such as transportation, residential homes, coal-burning power plants, industrial activities, and wildfires. Both short- and long-term exposure to air pollution can lead to a wide range of diseases, including stroke, heart disease, lung cancer, asthma, and other respiratory issues.

Outdoor air pollution

Long-term exposure to outdoor air pollution can lead to the onset of asthma in children and adults, lower respiratory tract infections, and an increased risk of cardiovascular and respiratory diseases. It can also exacerbate existing health conditions, causing more frequent hospitalizations, reduced quality of life, and even premature death. Vulnerable populations, including people of color, low-income communities, and those living near industrial operations, bear the brunt of exposures to outdoor air pollution.

The impact of outdoor air pollution on pregnant individuals and their fetuses is particularly concerning. Exposure to air pollution during pregnancy is associated with an increased risk of hypertensive disorders, intrauterine inflammation, and damage to the placenta, which can disrupt fetal growth and development. It is also linked to premature birth, low birth weight, and stillbirth, especially in mothers with pre-existing conditions or from marginalized communities.

Addressing outdoor air pollution is crucial not only for environmental but also for public health reasons. Implementing policies and initiatives that promote sustainable land use, cleaner energy and transport, energy-efficient housing, and improved waste management can effectively reduce air pollution levels and mitigate the associated health risks. By taking action to reduce outdoor air pollution, we can protect vulnerable populations, improve overall public health, and contribute to the fight against climate change.

Indoor air pollution

The health consequences of indoor air pollution are severe and include an increased risk of ischaemic heart disease, stroke, lower respiratory infection, and lung cancer. In children, indoor air pollution is linked to pneumonia, asthma, low birth weight, and tuberculosis. The impact of indoor air pollution on child health is particularly striking, with the death rate in children under five in East, West, Central, and Southern Africa being 100 times higher than in high-income countries.

The World Health Organization (WHO) has issued guidelines for indoor air quality and household fuel combustion to address this issue. These guidelines provide recommendations on clean fuels and technologies, such as solar, electricity, biogas, liquefied petroleum gas (LPG), and natural gas. They also emphasize the importance of addressing all household energy uses, especially cooking, space heating, and lighting, to improve health and environmental outcomes.

While the number of deaths from indoor air pollution is high, there is hope. Death rates from indoor air pollution are falling, even in the most polluted countries. Significant policy changes are needed to rapidly increase access to clean fuels and technologies, improve health outcomes, and mitigate climate change.

Fine particulate matter

The impact of fine particulate matter on human health is evident across all ages, with children and older adults being particularly vulnerable. In 2021, exposure to air pollution was linked to more than 700,000 deaths of children under five years old globally, with pneumonia and asthma being the leading causes. Among older adults, a study of over 22 million adults aged 65 and older found that short-term exposure to fine particulate matter was associated with an increased risk of mortality.

The health risks associated with fine particulate matter are not limited to physical health but also extend to mental health. A study conducted by Villeneuve et al. (2015) followed 89,835 healthy Canadian women between the ages of 40 and 59 for 25 years and found a link between long-term exposure to fine particulate matter and mortality, even after adjusting for other risk factors such as smoking and obesity.

The impact of fine particulate matter on human health is a global concern, with nearly every person on Earth breathing unhealthy levels of air pollution daily. The sources of this pollution are diverse, and policies addressing sustainable land use, cleaner energy, improved waste management, and energy efficiency can help reduce fine particulate matter and improve air quality.

Ozone and nitrogen dioxide

Ozone (O3) is a gas molecule composed of three oxygen atoms. While ozone in the upper atmosphere shields us from the sun's ultraviolet radiation, ozone at ground level is a serious health hazard. Ground-level ozone is formed when gases from tailpipes, smokestacks, factories, and other pollution sources come into contact with sunlight. This ozone smog aggressively attacks lung tissue, causing serious health problems.

Ozone exposure can cause premature death, especially when combined with other risk factors. Research has shown that the risk of premature death increases with higher levels of ozone. Notably, even lower levels of ozone can cause harm, with older adults facing a higher risk of premature death even when ozone pollution remains below the current national standard. In 2021, long-term exposure to ozone contributed to an estimated 489,518 deaths globally, including 14,000 ozone-related COPD deaths in the United States.

Nitrogen dioxide (NO2) is a toxic gas that irritates the mucous membrane and is linked to pulmonary diseases. The primary route of exposure is through inhalation, making the lungs the primary target organ. The dose inhaled determines the toxicity, with nitrogen dioxide poisoning depending on the duration, frequency, and intensity of exposure. At high concentrations, nitrogen dioxide has a harsh odour and is reddish-brown, while at lower concentrations, it may be odourless and colourless.

Nitrogen dioxide poisoning can cause a range of symptoms, including mild hyperinflammation, airway obstruction, and pulmonary edema. In some cases, it can lead to obstructive lung disease, asthma, chronic obstructive pulmonary disease (COPD), and even death. The effects of nitrogen dioxide exposure can be immediate or delayed, with death occurring through asphyxiation or pulmonary edema. In 2006, the World Health Organization (WHO) estimated that over 2 million deaths annually were attributed to air pollution, including nitrogen dioxide as one of the pollutants.

Health inequities

Air pollution is a major cause of health inequities, particularly affecting vulnerable populations who are disproportionately impacted by both climate hazards and poor air quality. Low- and middle-income countries suffer the highest exposures to air pollution, with nearly every person on earth breathing unhealthy levels of air pollution daily. This has far-reaching health implications, contributing to the global burden of disease and mortality.

Women and children, especially in low- and middle-income regions of Africa, Asia, and Oceania, bear the brunt of the health consequences from polluting fuels and technologies in homes. They are typically responsible for household chores, such as cooking and collecting firewood, exposing them to harmful smoke and pollutants. The use of solid fuels, such as wood, crop waste, charcoal, and coal, for cooking and heating, is a significant source of indoor air pollution, leading to respiratory infections, lung cancer, and other diseases. In 2021, indoor air pollution contributed to over 500,000 child deaths, with the death rate in children under five in Africa being 100 times higher than in high-income countries.

Additionally, air pollution impacts children's health from the womb, with potential lifelong effects. Children inhale more air relative to their body weight and absorb more pollutants while their organs are still developing. This exposure is linked to adverse pregnancy outcomes, including premature birth, low birth weight, and asthma. It also increases the risk of pneumonia, the leading cause of child deaths globally, and other respiratory diseases.

Addressing health inequities related to air pollution requires significant policy changes to increase access to clean fuels and technologies, such as solar, electricity, and liquefied petroleum gas. These interventions are crucial to protect the health of vulnerable populations, reduce morbidity and mortality, and achieve sustainable development goals.

Furthermore, as climate change intensifies, areas with high levels of nitrogen dioxide (NO2) and other pollutants can expect even greater health impacts. Fine particulate matter (PM2.5) from the burning of fossil fuels and biomass in transportation, residential homes, and industrial activities, poses a significant health risk. It can penetrate deep into the lungs, enter the bloodstream, and cause systemic damage to tissues and organs, leading to diseases such as stroke, heart disease, and lung cancer.

Frequently asked questions