Helena Joyce
Particulate matter is a mix of solid and liquid particles in the air we breathe. These particles vary in size, shape, and chemical composition and are emitted directly or formed when pollutants from various sources react in the atmosphere. Particulate matter smaller than 10 micrometers can enter our lungs and cause serious health issues, with smaller particles causing more damage. PM2.5, or fine particles, are linked to the greatest proportion of adverse health effects, including respiratory and cardiovascular issues, and even premature death. Human activities, such as burning fossil fuels, and natural sources contribute to particulate matter, which can have both warming and cooling effects on the climate.
| Characteristics | Values |
|---|---|
| Definition | Particulate matter (PM) is a proxy indicator for air pollution. It includes everything in the air that is not a gas. |
| Composition | A mixture of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid coatings. |
| Particle Size | PM particles vary widely in size. They can be larger than 10 micrometres (PM10) or smaller, at 2.5 micrometres or less (PM2.5). |
| Health Effects | Exposure to PM is associated with respiratory conditions (including asthma), cardiovascular disease, lung cancer, and premature death. |
| Sources | PM can be directly emitted from sources such as construction sites, unpaved roads, fields, smokestacks, and fires. It can also form in the atmosphere through complex reactions of pollutants. |
| Visibility | PM, especially PM2.5, reduces visibility by altering the way light is absorbed and scattered in the atmosphere. |
| Climate Impact | Some constituents of PM promote climate warming (e.g., black carbon), while others have a cooling influence (e.g., nitrate and sulfate). |
| Ecosystem Impact | PM deposition can adversely affect ecosystems, including plants, soil, and water quality. Metal and organic compounds in PM can alter plant growth. |
| Regulatory Action | The EPA in the US and the UK government have regulations and commitments to reduce PM emissions and improve air quality. |
What You'll Learn
Particulate matter is a mix of solids and liquids
Particulate matter, also known as particle pollution, is a complex mixture of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid coatings. These particles are so small that they are often invisible to the naked eye, requiring an electron microscope to be seen. However, when their levels are high, they can cause a haze in the air as they scatter and absorb light, reducing visibility.
The solids and liquids that make up particulate matter come from various sources, both human activities and natural processes. Human activities contributing to particulate matter include the combustion of carbon-based fuels, such as burning wood in residential fireplaces, wildfires, agricultural and prescribed fires, and the burning of fossil fuels in factories, power plants, and vehicles. Natural sources include ash and gases from wildfires and volcanoes.
Particulate matter can also form through chemical reactions in the atmosphere. For example, nitrogen dioxide and sulfur dioxide pollutants can react with oxygen and water vapour to form nitrate and sulfate particles. These particles have different chemical compositions and vary widely in size, shape, and toxicity. Some particles, such as those from diesel fuel, are particularly toxic due to their lead content.
The size of particulate matter is a critical factor in its potential health effects. The smaller the particle, the more harmful it can be. Particles less than 10 micrometers in diameter (PM10) can be inhaled into the lungs, and those less than 2.5 micrometers in diameter (PM2.5) are the most concerning as they can reach the alveoli in the lungs and even enter the bloodstream. Long-term exposure to PM2.5 has been linked to adverse health outcomes, including respiratory and cardiovascular issues, lung cancer, and premature death, especially in individuals with pre-existing heart or lung conditions.
While air quality has improved in recent decades due to stricter regulations and cleaner power plants and vehicles, particle pollution remains a significant concern. Climate change is driving increases in particulate matter from wildfire smoke, and certain groups, such as people of colour and children, are disproportionately affected by indoor and outdoor air pollution.
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Health risks: cancer, cardiovascular issues, premature death
Particulate matter, also known as particle pollution, refers to a mix of tiny solid and liquid particles in the air we breathe. These particles can be released through the burning of fuels, chemical reactions, or human activities and natural sources. The size of these particles varies, with some being one-tenth the diameter of a strand of hair, while others are so small they can only be seen with an electron microscope.
The health risks associated with exposure to particulate matter are significant and far-reaching. Due to their minuscule size, these particles can be inhaled and enter the lungs, leading to a variety of respiratory issues. People with existing heart or lung diseases, children, older adults, and individuals from minority and low socioeconomic status populations are particularly vulnerable to the effects of particulate matter.
Cancer
Particulate matter has been identified as a cause for concern when it comes to lung cancer. Epidemiological evidence strongly suggests that airborne particulate matter, specifically PM2.5, is associated with an increased incidence and mortality rate of lung cancer. PM2.5 particles are 2.5 microns or smaller in diameter and are capable of carrying toxic substances such as sulfates, organic compounds, polycyclic aromatic hydrocarbons, and heavy metals. These substances are considered major carcinogens, increasing the risk of lung cancer upon exposure.
Cardiovascular Issues
The American Heart Association (AHA) has concluded that exposure to particulate matter air pollution contributes to cardiovascular morbidity and mortality. Short-term exposure to particulate matter can lead to acute cardiovascular issues, while long-term exposure can reduce life expectancy by several years. Ultrafine particles, with a diameter of less than 0.1 microns, have been linked to various cardiovascular problems, including endothelial dysfunction, increased blood pressure, and the progression of atherosclerosis.
Premature Death
Exposure to particulate matter has been linked to premature death, particularly in individuals with pre-existing heart or lung disease. The fine particles in particulate matter can penetrate deep into the lungs and even enter the bloodstream, causing respiratory and cardiovascular issues that can lead to premature death.
In summary, particulate matter air pollution poses a significant threat to human health, with strong links to cancer, cardiovascular issues, and premature death. The minuscule size of these particles allows them to be inhaled, penetrating deep into the lungs and even entering the bloodstream, causing a range of health issues. While air quality standards and regulations have helped reduce particulate matter levels, it remains a pressing issue, especially with the increasing impact of climate change.
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Sources: human activities, natural sources, combustion
Particulate matter, or PM, refers to a mixture of solid and liquid particles suspended in the air. These particles vary in size, shape, and chemical composition. The size of the particles determines how they affect us. Coarse particles (PM10-2.5) can be coughed or sneezed out of the body, but smaller fine (PM2.5) and ultrafine particles can get trapped in the lungs, and the smallest ultrafine particles can pass through the lungs into the bloodstream.
PM emissions are the result of the formation of soot or black carbon, which is frequently referred to as "soot" or simply "particle pollution". These particles are produced by human activities and natural sources. Human activities that produce particulate matter include the combustion of carbon-based fuels in factories, power plants, vehicles, and equipment. The burning of fossil fuels, diesel, and gasoline is a large contributor to particulate matter emissions. Other human activities that produce particulate matter include industrial processes, vehicle emissions, and construction.
Natural sources of particulate matter include wildfires, volcanic activity, dust storms, and agricultural fires. Wildfires, in particular, are a significant source of particulate matter and are increasing due to climate change, especially in the western United States.
The combustion process is a significant contributor to particulate matter emissions. Both solid and liquid particles are produced during combustion, and these particles can include carbonaceous materials, nitrates, and sulfates, as well as other compounds. Volatile particulate matter (vPM) is formed during the combustion of fuels, especially in colder regions, and can change from a gaseous to a solid or liquid state once released into the atmosphere. CPM, or condensable PM, is another type of particulate matter that transforms from a gaseous state to a solid or liquid state immediately after leaving the engine exhaust.
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Standards and regulations: EPA, Clean Air Act, NAAQS
The Clean Air Act requires the United States Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, referred to as "criteria pollutants", that are common in outdoor air and are considered harmful to public health and the environment. These six pollutants are particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and lead. The EPA is also required to periodically review the standards to ensure they provide adequate health and environmental protection and to update them as necessary. The Clean Air Act identifies two types of NAAQS: primary standards and secondary standards.
Primary standards are national ambient air quality standards designed to protect public health with an adequate margin of safety. This includes protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards are national ambient air quality standards designed to protect the public welfare from adverse effects, including those related to effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate; damage to property; transportation hazards; economic values; and personal comfort and well-being.
The NAAQS review process begins with a comprehensive review of the relevant scientific literature. The literature is summarized, and conclusions are presented in a document called the Integrated Science Assessment (ISA). Based on the ISA, EPA staff perform a risk and exposure assessment, which is summarized in the Risk and Exposure Assessment (REA) document. The third document, the Policy Assessment (PA), integrates the findings and conclusions of the ISA and REA into a policy context and provides lines of reasoning that could be used to support the retention or revision of existing NAAQS, as well as alternative standards that could be supported by the review findings. Each of these three documents is released for public comment and peer review by the Clean Air Scientific Advisory Committee (CASAC), a subcommittee of the EPA's Science Advisory Board. Members of CASAC are appointed by the EPA Administrator for their expertise in one or more of the subject areas covered in the ISA.
Once all three documents are finalized, they are given to the EPA Administrator to select a proposed NAAQS, which is released through the Federal Register for public comment. Following the close of the comment period, the Administrator considers the comments received, makes changes to the proposed NAAQS if warranted, and publishes the final NAAQS in the Federal Register. Federal law requires that all states attain the NAAQS. Nonattainment areas must develop plans to attain the NAAQS, and attainment areas must develop plans to maintain attainment. Failure of a state to reach attainment of the NAAQS by the target date can trigger penalties, including withholding federal highway funds.
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Improving air quality: source control, ventilation, filters
Particulate matter refers to a mix of tiny solid and liquid particles in the air we breathe. These particles are so small that they can only be seen with an electron microscope. They are produced by human activities and natural sources, such as the burning of fuels, wildfires, and industrial processes. These particles contribute to air pollution and can have harmful effects on human health, even leading to respiratory issues and other chronic conditions.
To improve air quality and reduce the health risks associated with particulate matter, a combination of source control, ventilation, and filters can be employed.
Source Control
The first step to improving indoor air quality is to control the sources of pollution. This includes reducing or eliminating the use of known pollutants, such as avoiding the use of fireplaces or wood stoves, which can release soot and other fine particles into the air. It is also important to address outdoor sources of pollution, such as living near busy highways, ports, airports, or factories with high emissions, as these can contribute to indoor air pollution as well.
Ventilation
Ventilation is the next step to improving indoor air quality. It involves bringing in clean, outdoor air to dilute and remove indoor pollutants. Opening doors and windows for at least 15 minutes each day is a simple yet effective way to increase ventilation and improve air quality. However, it is important to avoid doing so on days with poor outdoor air quality or when there are nearby sources of pollution, such as wildfire smoke. Exhaust fans in bathrooms and kitchens can also help remove moisture and pollutants from specific areas, while ceiling fans can improve airflow throughout the home.
Filters
Air filters are another crucial component of improving indoor air quality. They work by capturing and removing particulate matter from the air, including dust, pollen, pet dander, and mold spores. It is important to choose high-quality filters with higher MERV ratings and denser filter media, as these are more effective at capturing smaller particles. Activated carbon filters, for example, are effective at removing particulate matter and household odours. However, it is important to replace filters regularly, as even premium filters have finite lifespans and can lose their effectiveness over time.
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Frequently asked questions
Particulate matter, often written as PM, is made up of tiny pieces of dust, dirt, soot, smoke, droplets of liquid, fumes, and other pollutants. Particulate matter is categorised based on size, with larger particles referred to as PM10 and finer particles as PM2.5.
Particulate matter is harmful because it can be inhaled and cause serious health problems. The smaller the particulate, the more serious the potential health effects. PM2.5 is the most harmful to health as it can go deep into the lungs and even enter the bloodstream. PM10 can also induce adverse health effects. Particulate matter has been linked to lung cancer, lung and cardiovascular disease, and decreased life expectancy.
Particulate matter can come from a variety of sources, including human activities and natural sources. Human activities that produce particulate matter include burning fossil fuels, construction, unpaved roads, and agricultural activities. Natural sources include ash and gases from wildfires and volcanoes.
There are several ways to reduce exposure to particulate matter. At the individual level, it is important to identify and remove the sources of pollutants, improve ventilation, and stay informed about air quality through tools like the Air Quality Index (AQI). At the government level, policies can be implemented to reduce emissions and improve air quality, such as the Clean Air Act in the United States.
