Air Pollution: Who Guidelines For A Healthier Planet

Air pollution is a serious environmental threat to human health, alongside climate change. It is caused by a complex mixture of solid particles, liquid droplets, and gases, which can originate from natural sources and human activity. The World Health Organization (WHO) has been publishing Air Quality Guidelines (AQGs) since 1987, with the latest update released in 2021. These guidelines are designed to offer recommendations on safe levels of common air pollutants to protect public health and reduce health risks associated with air pollution. The guidelines are based on rigorous scientific evidence and are intended to inform policy decisions and air quality management strategies worldwide. While they are not legally binding, the WHO AQGs provide valuable guidance for countries to improve air quality and mitigate the harmful impacts of air pollution on human health and the environment.

Air pollution sources

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 many other sources.

There are four main types of air pollution sources: mobile sources, stationary sources, area sources, and natural sources. Mobile sources include cars, buses, planes, trucks, and trains. These sources account for more than half of all air pollution in the United States, with automobiles being the primary contributor. Stationary sources, such as power plants, oil refineries, industrial facilities, and factories, emit large amounts of pollution from a single location and are also known as point sources. Area sources consist of smaller pollution sources that can collectively have a significant impact, such as agricultural areas, cities, and wood-burning fireplaces. Natural sources, including wind-blown dust, wildfires, and volcanoes, can sometimes be significant but typically do not create ongoing air pollution issues.

Particulate matter (PM) is a significant component of air pollution and is composed of chemicals such as sulfates, nitrates, carbon, or mineral dusts. Vehicle and industrial emissions from fossil fuel combustion, cigarette smoke, and burning organic matter, such as wildfires, all contribute to PM. Fine particulate matter (PM2.5) is of particular concern as it can be inhaled deeply into the lungs and has been associated with various health issues, including respiratory and cardiovascular diseases, and cancers. PM2.5 from coal combustion is especially harmful due to its high levels of sulfur dioxide, black carbon, and metals.

Other sources of air pollution include residential wood burning, agricultural equipment, construction, and industrial processes such as oil and gas development. Volatile organic compounds (VOCs), released during the combustion of gasoline and natural gas, are another major source of air pollution. Polycyclic aromatic hydrocarbons (PAHs), which are organic compounds containing carbon and hydrogen, are produced by industrial processes, power generation, and combustion. Ozone (O3), often referred to as smog at ground level, is formed when pollutants from cars, power plants, industrial boilers, refineries, and other sources react chemically in the presence of sunlight.

The WHO Global Air Quality Guidelines (AQG) provide recommendations for reducing key air pollutants and protecting public health. By implementing these guidelines, countries can improve air quality and mitigate the health risks associated with air pollution.

Health risks

Air pollution is one of the greatest environmental threats to human health, and it is estimated to cause 6.7 to 7 million premature deaths annually. Outdoor air pollution alone 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. It is a leading cause of non-communicable diseases (NCDs) such as heart attacks, stroke, lung cancer, and chronic obstructive pulmonary disease (COPD). Fine particulate matter (PM2.5) can penetrate the lungs and enter the body through the bloodstream, affecting all major organs. Exposure to PM2.5 can cause diseases to both our cardiovascular and respiratory systems. New research has also shown an association between prenatal exposure to high levels of air pollution and developmental delay at age three, as well as psychological and behavioural problems later on, including symptoms of attention deficit hyperactivity disorder (ADHD), anxiety, and depression. In children, exposure to air pollution can also result in reduced lung growth and function, respiratory infections, and aggravated asthma. In adults, ischaemic heart disease and stroke are the most common causes of premature death attributable to outdoor air pollution, and evidence is also emerging of other effects such as diabetes and neurodegenerative conditions.

The World Health Organization's (WHO) Air Quality Guidelines (AQG) serve as a global target for governments to improve their citizens' health by reducing air pollution. The guidelines provide recommendations for limit values of specific air pollutants, including particulate matter (PM), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO). These guidelines are developed through a transparent, evidence-based decision-making process and are updated regularly to reflect new health studies and scientific evidence.

WHO's Air Quality and Health Unit works in three cross-cutting areas to reduce air pollution levels and protect populations from health risks: knowledge, evidence, and measuring progress; institutional capacity building and technical support; and leadership and coordination. The organization also promotes interventions and initiatives for healthy sectoral policies, such as energy, transport, housing, and urban development, to address the key risks to health from indoor and outdoor air pollution.

WHO's guidelines provide interim targets to promote a gradual shift from high to lower concentrations of air pollutants, with associated health benefits. For example, achieving an interim target of 35 µg/m3 would save around 300,000 deaths worldwide annually. The guidelines also offer qualitative statements on the management of certain types of particulate matter, such as black carbon and ultrafine particles, for which there is insufficient quantitative evidence to set specific guideline levels.

Overall, addressing air pollution is crucial for protecting public health, and the WHO's Air Quality Guidelines provide a global framework for governments and policymakers to improve air quality and mitigate the significant health risks associated with air pollution.

Reducing air pollution

Air pollution is a complex mixture of solid particles, liquid droplets, and gases that can originate from numerous sources, both natural and anthropogenic (human-induced). The WHO Global Air Quality Guidelines (AQGs) provide evidence-based recommendations on air quality levels and targets to reduce key air pollutants and protect public health worldwide. While these guidelines are not legally binding, they serve as a reference for decision-makers to set standards and policies for improving air quality.

To reduce air pollution, the following measures can be implemented:

Improving the energy sector:

• Promoting cleaner energy sources and improving the efficiency of energy generation can reduce emissions from the energy sector, which is a major source of air pollution.
• Encouraging the use of renewable and alternative energy sources, such as solar, wind, and hydropower, can help reduce the reliance on fossil fuels and improve air quality.

Transport sector interventions:

• Encouraging the use of public transportation, carpooling, and active travel, such as walking and cycling, can reduce vehicle emissions.
• Investing in electric vehicles (EVs) and improving fuel efficiency standards for conventional vehicles can also help lower emissions from the transport sector.

Household and indoor air quality:

• Providing access to clean household energy, such as electricity or liquefied petroleum gas (LPG), can reduce the use of solid fuels and kerosene, which are major contributors to indoor air pollution.
• Promoting the use of vented heating and cooking stoves and raising awareness about the risks of tobacco smoke can also improve indoor air quality.

Waste management:

Implementing better municipal waste management practices, such as waste separation, recycling, and proper disposal, can reduce open-air burning of waste, which is a significant source of air pollution.

Industrial activities and agriculture:

• Regulating and enforcing stricter emission standards for industrial activities, such as the use of industrial chimneys, can help reduce air pollution from this sector.
• Promoting sustainable agricultural practices, such as reducing the burning of crop residues and improving livestock management, can also lower emissions from agriculture.

Policy interventions:

• Governments can set legally binding standards and goals for air quality management at international, national, and local levels, utilizing the WHO guidelines as a reference.
• Investing in cleaner transport, energy-efficient homes, and improved power generation can reduce key sources of outdoor air pollution, as outlined by the WHO.

By implementing these measures and striving to achieve the WHO guideline levels, significant health benefits can be achieved, and millions of premature deaths due to air pollution can be prevented.

Air quality guideline levels

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 many other sources. The World Health Organization's Air Quality Guidelines (AQG) are a set of evidence-based recommendations of limit values for specific air pollutants. They are designed to provide guidance in reducing the health impacts of air pollution based on expert evaluations of current scientific evidence. The guidelines are neither standards nor legally binding criteria, but they offer global targets for national, regional, and city governments to work towards improving the health of their citizens by reducing air pollution.

The WHO's Air Quality Guidelines recommend levels and interim targets for common air pollutants: particulate matter (PM), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2). These guidelines are of high methodological quality and are developed through a transparent, evidence-based decision-making process. They are based on systematic literature reviews, rigorous evaluation methods, and extensive consultation with experts and end-users of the guidelines from all regions of the world. The guidelines also incorporate scientific evidence from multiple countries, making them relevant to diverse conditions around the world.

The WHO updates the Air Quality Guidelines regularly to assure their continued relevance and to support a broad range of policy options for air quality management. The 2021 update of the guidelines responded to the real and continued threat of air pollution to public health. The latest global version before that was published in 2005. Since the 2005 update, there has been a marked increase in evidence showing how air pollution affects different aspects of health. As a result, the WHO has adjusted almost all the AQG levels downwards, warning that exceeding the new air quality guideline levels is associated with significant risks to health.

The WHO's Air Quality Guidelines provide clear evidence of the damage air pollution inflicts on human health, even at lower concentrations than previously understood. They recommend new air quality levels to protect the health of populations by reducing levels of key air pollutants, some of which also contribute to climate change. By striving to achieve these guideline levels, countries will be both protecting the health of their citizens and mitigating global climate change. The guidelines also highlight 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.

Management of particulate matter

Particulate matter (PM) is a complex mixture of solid particles and liquid droplets, which can be carried over long distances and settle on various surfaces, including lakes, forests, crops, soil, and stones. It is one of the most important and dangerous air pollutants, alongside harmful gases, chemicals, and smoke particles. PM is primarily generated by fuel combustion in sectors such as transport, energy, households, industry, and agriculture. Diesel vehicles, in particular, are a major source of particle pollution.

The World Health Organization (WHO) has developed global air quality guidelines (AQG) to address the health risks associated with particulate matter. These guidelines offer global guidance on thresholds and limits for key air pollutants, including PM. While the guidelines are not legally binding, they provide recommendations for limit values to help countries improve air quality and protect public health. The guidelines also offer qualitative statements on good practices for managing certain types of particulate matter, such as black carbon, ultrafine particles, and particles from sand and dust storms.

To reduce particulate matter emissions and protect human health and the environment, various strategies can be implemented. At the individual level, reducing the usage of particulate-forming appliances, avoiding burning, improving combustion efficiency, opting to walk instead of driving, using solar energy, using indoor air purifiers, and maintaining vehicles or switching to non-polluting vehicles can help. Additionally, quitting indoor smoking and improving ventilation and regular cleaning practices can reduce indoor particulate matter levels.

On a larger scale, national and regional regulations, as well as local actions, can be implemented to improve air quality and reduce particulate matter concentrations. Policies supporting cleaner transport, energy-efficient homes, improved power generation, and better municipal and agricultural waste management can significantly reduce outdoor air pollution. Access to clean household energy can also positively impact ambient air quality in certain regions.

By addressing both indoor and outdoor sources of particulate matter and implementing a combination of individual, local, and national strategies, we can effectively reduce particulate matter emissions and mitigate the adverse effects of this dangerous air pollutant on human health and the environment.

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