Understanding Pm10 And Pm2.5: Air Quality Essentials

Particulate matter (PM) is a term used to describe the mixture of solid particles and liquid droplets in the air. PM10 and PM2.5 are both types of particulate matter that can be inhaled and have been linked to adverse health effects. PM10 includes dust from construction sites, landfills, agriculture, wildfires, and industrial sources, while PM2.5 is primarily emitted from road vehicles and industrial emissions. PM2.5 is of particular concern as it is small enough to penetrate deep into the lungs and has been associated with the greatest proportion of adverse health effects related to air pollution.

PM10 and PM2.5 refer to the sizes of particles in the air

The main distinction between PM10 and PM2.5 is their size, which also gives them different properties and health impacts. PM10 particles, also known as coarse dust, are small enough to be inhaled and can be harmful to human health, but they are typically filtered out in the throat and nasal passages. On the other hand, PM2.5 particles, referred to as fine dust, are so minuscule that they can penetrate deep into the lungs and even enter the bloodstream. This can lead to a host of health issues, including respiratory problems and the exacerbation of pre-existing heart and lung conditions.

The sources of PM10 and PM2.5 particles vary as well. PM10, or coarse particles, are primarily formed from physical processes such as wind-blown dust from roads or fields, and crushing or grinding operations. Natural sources include sea spray, volcanic ash, and pollen. Anthropogenic or man-made sources largely involve agricultural activities, industrial emissions, and road traffic.

PM2.5 particles, on the other hand, have different predominant sources. While industrial and domestic combustion contribute significantly to PM2.5 emissions, activities such as construction and demolition produce a higher proportion of PM10 particles. It is worth noting that the classification of particles as PM10 or PM2.5 is based on scientific consensus and long-standing evidence regarding how particles of varying sizes penetrate the respiratory system and are absorbed by the lungs.

Monitoring the levels of both PM10 and PM2.5 is crucial for maintaining a healthy indoor environment and understanding their potential health impacts. Continuous monitoring over time can help detect changes in particle concentrations, especially during periods of high outdoor pollution or external events like wildfires. While both types of particles can be harmful, PM2.5 poses more urgent and severe health risks due to its ability to penetrate deeper into the respiratory system.

PM10 is classified as coarse dust, while PM2.5 is fine dust

PM10 and PM2.5 are both types of particulate matter (PM) – a mixture of solid particles and liquid droplets found in the air. Particulate matter is also known as particle pollution. PM10 is classified as coarse dust, while PM2.5 is fine dust.

The numbers in PM10 and PM2.5 refer to the diameter of the particles in micrometres. Particles with a diameter of 10 micrometres or less are classified as PM10, while particles with a diameter of 2.5 micrometres or less are classified as PM2.5. To put this into perspective, the average human hair is about 70 micrometres in diameter. This means that a single human hair is 30 times larger than the largest fine particle.

PM2.5 particles are so small that they can be inhaled and cause serious health problems. They can get deep into your lungs, and some may even enter your bloodstream. PM2.5 particles are the main cause of reduced visibility (haze) in many parts of the United States, including national parks and wilderness areas. PM2.5 particles come in many sizes and shapes and can be made up of hundreds of different chemicals. They are emitted directly from sources such as construction sites, unpaved roads, fields, smokestacks, and fires. Most particles form in the atmosphere as a result of complex reactions between chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from the combustion of gasoline, oil, diesel fuel, or wood.

PM10 particles are larger than PM2.5 particles but are still small enough to be inhaled and cause adverse health effects. They are more likely to deposit on the surfaces of the larger airways in the upper region of the lung. PM10 particles often derive from different sources than PM2.5 particles and have different chemical compositions. They include dust from construction sites, landfills, agriculture, wildfires, industrial sources, wind-blown dust from open lands, pollen, and fragments of bacteria.

PM2.5 poses more serious health risks than PM10

PM10 and PM2.5 are both airborne particulate matter that can be inhaled and cause adverse health effects. However, PM2.5 poses more serious health risks than PM10 due to its smaller size and ability to penetrate deeper into the respiratory system.

PM10 refers to particulate matter with a diameter of 10 micrometres or less. These particles are inhaleable and can reach the lungs, where they can cause damage and inflammation. PM10 is typically deposited on the surfaces of the larger airways in the upper region of the lung.

On the other hand, PM2.5 is defined as fine particulate matter with diameters of 2.5 micrometres or less. Due to their smaller size, these particles can penetrate deeper into the respiratory system and are more likely to be deposited in the lower regions of the lung. This includes the alveoli, where gas exchange occurs, and from where particles can potentially enter the bloodstream.

The health risks associated with PM2.5 exposure are more severe than those linked to PM10. Short-term exposure to PM2.5 (up to 24 hours) has been associated with premature mortality, increased hospital admissions for heart or lung issues, acute and chronic bronchitis, asthma attacks, emergency room visits, respiratory symptoms, and restricted activity days. Research has also shown that children living in areas with high levels of PM2.5 have slower lung growth and smaller lungs at age 18 compared to those in low PM2.5 areas.

The California Air Resources Board (CARB) recognises the health risks posed by airborne particles and has adopted standards to regulate PM2.5 and PM10 concentrations. The national annual average standard for PM2.5 was most recently revised in 2024 following new evidence of continued risk at lower concentrations. This highlights the serious health concerns associated with PM2.5 exposure and the need for stringent air quality standards to protect public health.

Sources of PM10 include road traffic and industrial emissions

PM10 refers to particulate matter that has a penetration efficiency through a size-selective orifice of 50% at an aerodynamic diameter of 10 μm. Sources of PM10 include road traffic and industrial emissions. Road traffic is considered a major source of PM10, contributing up to 55% of PM10 in traffic sites. This includes emissions from the combustion of gasoline, diesel fuel, and vehicle abrasion from tires, brakes, and road surfaces.

Non-exhaust emissions from road traffic, such as resuspended road dust and crustal material, also contribute significantly to PM10 levels. In a study conducted in Southern Europe, non-exhaust emissions accounted for approximately 87% of traffic-derived PM10. Similarly, in Poland, natural emissions (soil, sand) and non-exhaust emissions from vehicle traffic had a stronger influence on the composition of PM10 during a measurement period.

Industrial emissions contribute to PM10 through industrial processes and product use, including fuel combustion in manufacturing and construction. Industrial combustion refers to burning fuels to generate energy for industrial use, such as driving machinery or creating heat for industrial processes. While annual emissions of PM10 have decreased globally, industrial activities, such as the burning of biomass-based fuels, continue to contribute to PM10 pollution.

Other sources of PM10 include construction sites, landfills, agriculture, wildfires, and industrial sources. PM10 particles can also form through chemical reactions of gases, such as sulfur dioxide and nitrogen oxides, emitted from both natural and anthropogenic sources. Overall, a combination of road traffic, industrial emissions, and other factors contribute to the presence of PM10 in the atmosphere.

PM emissions have decreased in the UK in recent years

PM10 and PM2.5 refer to particulate matter that affects air quality and, consequently, the climate. Particulate matter, or PM, is a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large enough to be seen by the human eye, while others are so small they can only be detected using an electron microscope. PM10 refers to particles smaller than 10 microns, while PM2.5 refers to particles smaller than 2.5 microns.

However, the impact of the lockdown on PM emissions in the UK varied across different regions. For example, in the South East of the UK, there was a decrease in de-weathered PM10 concentrations of approximately 14% relative to the previous 5-year mean. At the same time, PM2.5 concentrations increased by about 6%. The limited evidence of a decline in particulate matter concentrations during the UK lockdown was attributed to reductions in local traffic volumes in the South East.

While the COVID-19 lockdown may have temporarily reduced PM emissions in certain regions of the UK, other factors, such as government policies and technological advancements, have also contributed to decreasing PM emissions in the UK over the years. For instance, the UK government has implemented various measures to reduce air pollution and improve air quality, including policies targeting the reduction of NO2 and PM emissions.

Additionally, the transition to electric vehicles (EVs) is another factor that could contribute to decreasing PM emissions in the UK. However, the recent weakening of rules on electric car sales by the UK government may slow down this transition. According to analysis by the campaign group Transport and Environment (T&E), the relaxed rules could result in more plug-in hybrid electric vehicles (PHEVs) on UK roads, potentially leading to higher emissions than expected.

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