Greta Jimenez
Air pollution is a complex mixture of solid particles, liquid droplets, and gases that can come from many sources, such as household fuel burning, industrial chimneys, traffic exhausts, and agricultural practices. It is a significant threat to people worldwide, causing an estimated 4.2 million premature deaths worldwide in 2019 alone. The World Health Organization (WHO) has developed Air Quality Guidelines (AQG) to serve as global targets for governments to work towards improving air quality and protecting their citizens' health. These guidelines offer recommended levels and targets for common air pollutants such as PM, O3, NO2, and SO2. In the United States, the Environmental Protection Agency (EPA) establishes the National Ambient Air Quality Standards (NAAQS) for six principal pollutants (criteria air pollutants) through the Clean Air Act. These standards aim to protect public health and the environment, and they are periodically reviewed and revised to ensure effectiveness. Both the WHO guidelines and the EPA standards play a crucial role in addressing the health and environmental impacts of air pollution.
| Characteristics | Values |
|---|---|
| Air Quality Index (AQI) | 0-50 is good air quality, 300+ is hazardous |
| WHO Air Quality Guidelines (AQG) | Interim targets for PM, O3, NO2, and SO2 |
| Particulate Matter (PM) | PM2.5 and PM10 |
| Carbon Monoxide (CO) | Colourless, odourless, and tasteless |
| Nitrogen Dioxide (NO2) | 0.053 ppm |
| Sulfur Dioxide (SO2) | 0.14 ppm (24-hour), 0.03 ppm (annual) |
| Lead | 0.15 micrograms per cubic liter (µg/m3) |
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What You'll Learn
The World Health Organization's Air Quality Guidelines
The World Health Organization (WHO) has developed Air Quality Guidelines (AQG) that offer global guidance on thresholds and limits for key air pollutants that pose health risks. These guidelines are not legally binding but are designed to offer evidence-based recommendations to countries to help them achieve air quality that protects public health. The guidelines are updated regularly to ensure their continued relevance and to support a broad range of policy options for air quality management in various parts of the world.
The first release of the guidelines was in 1987, and several updated versions have been published since then, with the latest global version released in 2005. The 2021 update of the WHO air quality guidelines recognizes the real and continued threat of air pollution to public health and includes particulate matter, ozone, nitrogen dioxide, and sulfur dioxide. The guidelines recommend aiming for annual mean concentrations of PM2.5 not exceeding 5 µg/m3 and NO2 not exceeding 10 µg/m3, and a peak season mean 8-hour ozone concentration not exceeding 60 µg/m3.
The WHO has also developed a global database of air quality standards that compiles national air quality standards for major pollutants and other airborne toxics from countries worldwide. This database provides an overview of global efforts towards achieving the WHO global air quality guidelines and is intended to empower stakeholders such as policymakers, public health officials, and researchers with the information necessary to monitor progress, drive policy changes, and support the implementation of effective interventions to improve air quality and safeguard public health.
In addition to the guideline values, the WHO Global air quality guidelines provide interim targets to promote a gradual shift from high to lower concentrations and their associated health benefits. For example, achieving interim target one (35 µg/m3) could save around 300,000 deaths worldwide annually. The guidelines also offer qualitative statements on good practices for the management of certain types of particulate matter, such as black carbon/elemental carbon, ultrafine particles, and particles originating from sand and dust storms.
The WHO Air Quality Guidelines are an important tool to help improve public health by reducing air pollution levels. In 2019, 99% of the world's population was living in places where the WHO air quality guidelines levels were not met, and ambient (outdoor) air pollution is estimated to have caused 4.2 million premature deaths worldwide in that year. The guidelines provide critical input into clean air policies and regulations around the world, helping to reduce the health impacts of air pollution and improve health outcomes for people of all ages.
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Particulate matter (PM)
PM is classified based on the diameter of the particles. PM10 refers to particles with a diameter of 10 micrometres or less, which are inhalable into the lungs and can induce adverse health effects. PM2.5, on the other hand, refers to fine particles with a diameter of 2.5 micrometres or less, which pose the greatest risk to health. These particles are so small that they can penetrate deep into the lungs and enter the bloodstream, affecting all major organs. They are the main cause of reduced visibility (haze) in many areas and have been linked to various health issues, including respiratory and cardiovascular diseases, lung cancer, and even premature death.
PM2.5 particles come in many sizes and shapes and can be composed of hundreds of different chemicals. Some are emitted directly from sources such as construction sites, unpaved roads, fields, smokestacks, or fires. However, most particles form in the atmosphere as a result of complex reactions between pollutants such as sulfur dioxide and nitrogen oxides. These pollutants are emitted from sources like power plants and industrial combustion processes.
To protect public health, the World Health Organization (WHO) has developed Air Quality Guidelines (AQG) that provide global targets for governments to work towards improving air quality and reducing air pollution. The AQG offers guidance on thresholds and limits for key air pollutants, including PM2.5 and PM10. Additionally, the US Environmental Protection Agency (EPA) regulates inhalable particles and has implemented rules to reduce emissions of pollutants that form PM, helping state and local governments meet national air quality standards.
It is important to note that good air quality is crucial for both human health and the environment. Air quality alerts, such as the Air Quality Index (AQI), can help individuals protect themselves from harmful levels of PM. These alerts provide information on the air quality and associated health risks, allowing people to take appropriate actions to safeguard their health.
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National Ambient Air Quality Standards (NAAQS)
Air pollution is a complex mixture of solid particles, liquid droplets, and gases. It can come from many sources, such as household fuel burning, industrial chimneys, traffic exhausts, power generation, open burning of waste, agricultural practices, desert dust, and many other sources. The World Health Organization (WHO) estimates that in 2019, about 4.2 million premature deaths worldwide were caused by ambient (outdoor) air pollution.
To address this issue, the Clean Air Act Amendments of 1970 instructed the U.S. Environmental Protection Agency (U.S. EPA) to establish National Ambient Air Quality Standards (NAAQS). NAAQS are defined as the maximum amount of a pollutant averaged over a specified period that can be present in outdoor air without harming public health. The Clean Air Act identifies two types of NAAQS: primary standards and secondary standards. Primary standards aim to protect public health, including sensitive populations such as asthmatics, children, and the elderly. On the other hand, secondary standards focus on protecting public welfare, including soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate.
The U.S. EPA is responsible for setting NAAQS for six principal pollutants or "criteria pollutants," which are common in outdoor air and considered harmful to public health and the environment. These six criteria pollutants include particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and lead. The EPA regularly reviews and revises the NAAQS every five years to ensure they are based on the most recent scientific findings.
Federal law requires all states to attain the NAAQS. Nonattainment areas must develop plans to reach the standards, and attainment areas must maintain them. The EPA can impose penalties on states that fail to achieve the NAAQS by the target date, including withholding federal highway funds. The process of selecting a proposed NAAQS involves a comprehensive review of scientific literature, risk and exposure assessments, and public comments. The final NAAQS is published in the Federal Register.
Additionally, the WHO has developed Air Quality Guidelines (AQG) to provide global targets for national and regional governments to work towards improving air quality and protecting their citizens' health. While the AQG is not legally binding, it offers guidance on thresholds and limits for key air pollutants. Governments can use these guidelines as a reference and consider their unique local conditions before adopting them as legally based standards.
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Air Quality Index (AQI)
The Air Quality Index (AQI) is a system that provides information about the health effects of common air pollutants and how to avoid the adverse effects. It is a useful tool that helps individuals understand the impact of air quality on their health and make decisions to reduce short-term exposure to air pollution. The AQI is calculated using the concentration of air pollutants over a specified period, obtained from air quality monitors or models. The concentration and time together represent the dose of the air pollutant. The AQI can increase due to a rise in air emissions, such as during rush-hour traffic or an upwind forest fire, or from a lack of dilution of air pollutants.
The AQI is designed to protect public health and guide countries in achieving cleaner air that safeguards the well-being of their citizens. It is based on the lowest achievable emissions rate and reflects air quality management objectives. The World Health Organization (WHO) plays a crucial role in this regard by offering global guidance on thresholds and limits for key air pollutants that pose health risks. Their Air Quality Guidelines (AQG) serve as a target for governments to work towards improving air quality and reducing pollution-related health issues.
The AQI is typically presented as a scale with ranges, each assigned a descriptor, a colour code, and a standardised public health advisory. For instance, Canada's Air Quality Health Index (AQHI) provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality. It also offers advice on protecting oneself during different levels of air quality and suggests behavioural changes to reduce environmental footprints. The AQHI specifically caters to individuals sensitive to air pollution, ensuring they receive tailored guidance to safeguard their health.
Various nations and territories have adopted their own AQIs, tailoring them to their specific needs and circumstances. For example, each state and territory in Australia is responsible for monitoring air quality and publishing data according to the National Environment Protection (Ambient Air Quality) Measure (NEPM) standards. They utilise a consistent linear scale where 100 represents the maximum concentration standard for each pollutant, as set by the NEPM. These AQIs are essential tools for raising awareness, empowering individuals to take necessary precautions, and driving policy changes to improve air quality and protect public health.
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Health effects of air pollution
Air pollution is a complex mixture of solid particles, liquid droplets, and gases. It can come from many sources, including household fuel burning, industrial chimneys, traffic exhausts, power generation, open burning of waste, agricultural practices, desert dust, and more. The World Health Organization (WHO) estimates that air pollution causes 7 million premature deaths every year.
Air pollution has been linked to a range of adverse health effects, including respiratory and cardiovascular problems, cancers, and mental health issues. Fine particulate matter (PM2.5) can penetrate the lungs and enter the bloodstream, affecting major organs. Exposure to PM2.5 has been associated with cardiovascular and respiratory diseases, lung cancer, and chronic obstructive pulmonary disease (COPD).
Recent studies have also found links between air pollution and mental health. Research examining medical records in the US and Denmark found that people living in areas with poor air quality had higher rates of bipolar disorder and major depression. Additionally, air pollution has been associated with developmental delays in children, including symptoms of attention deficit hyperactivity disorder (ADHD), anxiety, and depression.
Outdoor air pollution, caused by sources such as traffic exhausts and industrial emissions, is a major environmental health problem affecting people worldwide. It is estimated to have caused 4.2 million premature deaths globally in 2019, with 89% of these occurring in low- and middle-income countries. The greatest number of deaths were recorded in the WHO South-East Asia and Western Pacific Regions.
Indoor air pollution can also have significant health impacts. For example, freshly painted walls can release fumes and volatile organic compounds (VOCs) that irritate the eyes and nose. New furniture or carpets may contain strong-smelling chemicals that can cause headaches or dizziness.
Overall, the health effects of air pollution are far-reaching and pose a significant threat to public health. It is important for individuals to be aware of the air quality in their local areas and take appropriate measures to protect their health.
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Frequently asked questions
Air pollution is a mixture of solid particles, liquid droplets, and gases that can be harmful to human health and the environment.
Air pollution comes from a variety of sources, including household fuel burning, industrial chimneys, traffic exhausts, power generation, open burning of waste, agricultural practices, and desert dust.
Air pollution has been linked to a range of negative health effects, including respiratory and cardiovascular diseases, cancers, and even developmental delays in children. It is estimated to cause millions of premature deaths worldwide each year.
The World Health Organization (WHO) has developed Air Quality Guidelines (AQG) that serve as global targets for governments to improve air quality and protect public health. The AQG provides recommended levels and interim targets for common air pollutants such as PM, O3, NO2, and SO2.
Air quality is typically measured through the Air Quality Index (AQI), which is an index that indicates the level of air pollution and the potential health concerns. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality.
