Air Pollution's Deadly Duo: Uncovering The Second Killer

Air pollution is a major global health concern, causing millions of deaths annually. In 2021, approximately 8.1 million deaths worldwide were linked to air pollution, making it the second leading risk factor for death, after high blood pressure. This issue affects almost every part of the world, with low- and middle-income countries suffering the highest exposures. Indoor and outdoor air pollution, caused by sources such as vehicle emissions, industrial facilities, and the burning of fossil fuels, have severe health implications. These include respiratory diseases, cardiovascular issues, lung cancer, and chronic conditions like asthma. With air pollution surpassing smoking, malaria, and other factors as a cause of death, it demands urgent attention from policymakers and health organizations to implement effective regulations and reduce its deadly impact.

Indoor air pollution

Air pollution is a leading cause of death worldwide, with approximately 8.1 million deaths linked to it in 2021. It has become the second leading risk factor for death, after high blood pressure. Of these deaths, 709,000 were children under the age of five, with more than 70% linked to household air pollution.

The use of polluting fuels and stoves for cooking and heating results in indoor air pollution. The World Health Organization (WHO) has issued guidelines for indoor air quality, offering evidence-based guidance on clean fuels and technologies. These include solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, alcohol fuels, and biomass stoves that meet emission targets.

The effects of indoor air pollution on human health are significant. Both short- and long-term exposure can cause respiratory diseases, heart disease, cognitive deficits, and cancer. Indoor air pollution is also linked to an increased risk of non-communicable diseases in adults, such as stroke, diabetes, lung cancer, and chronic obstructive pulmonary disease (COPD). Prenatal exposure to indoor air pollution has been associated with an increased chance of children developing pneumonia in their first year of life.

There are many sources of indoor air pollution. Inadequate ventilation can increase indoor pollutant levels as outdoor air does not dilute emissions from indoor sources. High temperatures and humidity levels can also increase some pollutants' concentrations. Other sources include human activities such as smoking, burning solid fuels, cooking, and cleaning.

Outdoor air pollution

In 2021, air pollution accounted for approximately 8.1 million deaths globally, making it the second leading risk factor for death, after high blood pressure. Of these deaths, 709,000 were children under the age of five, with more than 70% linked to household air pollution caused by the burning of unclean fuels and solid fuel stoves. Outdoor air pollution is estimated to have caused 4.2 million premature deaths worldwide in 2019, with 89% of those premature deaths occurring in low- and middle-income countries, particularly in the WHO South-East Asia and Western Pacific Regions.

The major sources of outdoor air pollution include residential energy use for cooking and heating, vehicles, power generation, agriculture/waste incineration, and industry. Fossil fuels, particularly coal, are the largest contributors to global climate change and air pollution, accounting for over 75% of global greenhouse gas emissions and nearly 90% of all carbon dioxide (CO2) emissions. Carbon monoxide (CO), a colorless, odorless, and toxic gas produced by the incomplete combustion of fossil fuels, is another significant contributor to outdoor air pollution, especially from cars, trucks, and other vehicles burning fossil fuels.

Particulate matter (PM), particularly PM2.5, is a common proxy indicator for air pollution and is associated with negative health impacts. These tiny particles, measuring less than 2.5 micrometers in diameter, can remain in the lungs, enter the bloodstream, and affect multiple organ systems, increasing the risks for various non-communicable diseases. In 2021, PM2.5 air pollution was attributed to approximately 7.8 million deaths globally.

Addressing outdoor air pollution is crucial for protecting public health and reducing the burden of disease, especially in low- and middle-income countries. Successful policies to reduce outdoor air pollution include implementing clean technologies in industries, improving waste management practices, transitioning to clean and renewable energy sources, promoting energy efficiency in homes and urban planning, and adopting cleaner modes of transportation.

Particulate matter

According to the fifth edition of the State of Global Air (SoGA) report, air pollution is the second leading cause of death worldwide, accounting for approximately 8.1 million deaths in 2021. It is a significant issue affecting almost every part of the world, with low- and middle-income countries suffering the highest exposures. Among the various air pollutants, fine particulate matter, specifically PM2.5, stands out as a critical contributor to these adverse health outcomes.

The health consequences of exposure to fine particulate matter are extensive. Studies have linked PM2.5 exposure to premature death, especially in individuals with chronic heart or lung diseases. It is a significant contributor to cardiovascular and respiratory diseases, including heart disease, stroke, and chronic obstructive pulmonary disease (COPD). Moreover, fine particulate matter has been associated with increased respiratory symptoms such as airway irritation, coughing, and difficulty breathing. The impact of PM2.5 extends beyond physical health, as there is growing evidence suggesting that air pollution can impair cognitive functions.

The sources of particulate matter pollution are diverse and context-specific. Outdoor air pollution, or ambient air pollution, arises from residential energy use for cooking and heating, vehicles, power generation, agriculture and waste incineration, and industrial activities. Indoor air pollution, or household air pollution, is caused by the use of polluting open fires or inefficient stoves fuelled by kerosene, biomass (such as wood, animal dung, and crop waste), and coal. The burning of these unclean fuels and solid fuels releases dangerous pollutants, including particulate matter, into indoor environments.

The adverse effects of particulate matter pollution are not limited to humans alone. It also impacts the environment, affecting ecosystems and materials. Additionally, particulate matter has been shown to reduce visibility by altering the way light is absorbed and scattered in the atmosphere.

Addressing particulate matter pollution is crucial to protecting public health and the environment. Implementing policies and investments that promote sustainable land use, cleaner household energy sources, improved transportation, energy-efficient housing, and better waste management practices can effectively reduce particulate matter pollution and improve air quality globally.

Carbon monoxide

The harmful effects of carbon monoxide are due to its strong affinity for hemoglobin. When inhaled, carbon monoxide molecules bind tightly to hemoglobin, preventing oxygen molecules from attaching to it. This interference with cellular respiration and gas exchange can lead to hypoxic injury, nervous system damage, and even death. The symptoms of carbon monoxide poisoning are often mistaken for viral infections or other illnesses. Headache is the most common symptom, and increasing exposure can lead to cardiac abnormalities, central nervous system disorders, and eventually death.

According to the World Health Organization (WHO), air pollution, including indoor and outdoor pollution, is a significant risk factor for various health issues. While the specific contribution of carbon monoxide to air pollution-related deaths is challenging to determine, it is undoubtedly a contributing factor. Efforts to reduce air pollution, such as promoting sustainable land use, cleaner energy sources, and improved waste management, can help mitigate the health impacts of pollutants like carbon monoxide.

Nitrogen dioxide

In addition to respiratory issues, NO2 exposure has been linked to heart and lung damage, adverse pregnancy and birth outcomes, and potential risks of kidney and neurological harm, autoimmune disorders, and cancer. The elderly, children, and individuals with asthma are generally at greater risk of experiencing the negative health effects of NO2.

According to the World Health Organization (WHO), the vast majority of the global population (99%) breathe air that exceeds the recommended guideline limits for pollutant levels. This is particularly concerning as air pollution, including NO2, has become the second-leading risk factor for death globally. In 2021, approximately 8.1 million deaths worldwide were attributed to air pollution, with more than 700,000 of those being children under five years old.

While efforts to reduce NO2 emissions, such as the federal Clean Air Act, have led to improvements in air quality in some regions, there is still a significant impact on human health in many parts of the world.

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