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PM10 vs PM2.5: What’s the Difference?

Joe Di Noto

Executive Summary:

  • PM10 and PM2.5 are types of particulate matter and are both harmful air pollutants found indoor and outdoors. PM2.5 (fine particles) are typically more dangerous to human health.
  • Indoor sources of PM10 and PM2.5 include dust, tobacco smoke, burning of candles or incense, emissions from office equipment, construction or renovation activities, poor ventilation, and infiltration of outdoor air pollution.
  • Monitoring both PM10 and PM2.5 is important for maintaining a healthy indoor environment and understanding potential sources and health impacts.
  • Continuous monitoring over time is useful for detecting changes in PM concentrations, especially during periods of high outdoor pollution or external events like wildfires.
  • When selecting a commercial IAQ monitor, ensure it can detect both PM10 and PM2.5 for a comprehensive understanding of indoor air quality.

PM10 vs PM2.5

In simple terms:  PM2.5 and PM10 refer to tiny particles in the air, smaller than the width of a hair, that could be inhaled and cause health issues. They are created from various sources like traffic, factories, or even office printers. Both can be detrimental to health and should be monitored, but PM2.5 poses more serious and urgent health risks.

In technical terms: PM10 and PM2.5 refer to different sizes of particulate matter (PM), which is a type of pollutant that can be present in indoor or ambient air. The number that follows "PM" in each term refers to the aerodynamic diameter of the particles. Specifically, PM10 encompasses particles with an aerodynamic diameter smaller than 10 micrometers (μm), while PM2.5 includes particles with a diameter smaller than 2.5 μm. Notably, PM10 can be described as coarse dust and PM2.5 as fine dust. 

NB: According to the technical definition, PM2.5 is contained in PM10 (which covers all particles < 10 micrometers). For the purposes of this article, we will distinguish between the two, and will generally use PM10 to refer to particles that are between 2.5-10 micrometers.

Sources of PM10 and PM2.5

PM10: Also known as coarse particles, these are primarily formed from physical processes such as wind-blown dust from roads or fields, and crushing or grinding operations. Natural sources can include sea spray, volcanic ash, and pollen. Man-made sources, on the other hand, largely involve agricultural works, industrial emissions, and road traffic. Combustion processes also release PM10, but these are more frequently associated with the release of finer PM2.5 particles.

PM2.5: PM2.5, also known as fine particles, originate from the burning of fossil fuels (like gasoline and diesel) and are generally emitted from vehicles, power plants, industrial processes, residential wood burning, forest fires, agricultural burning, and some industrial processes. They are formed from gas and condensation processes such as the transformation of sulfur dioxide (SO2) or nitrogen oxides (NOx) into sulfate and nitrate particles, or the formation of soot and complex organics in the atmosphere.

Causes of High Levels of PM10 and PM2.5 in Office Buildings:

Indoor sources of particulate matter include dust, tobacco smoke, burning of candles or incense, indoor cooking (such in poorly-insulated kitchens or office cafeterias), and emissions from office equipment such as printers and photocopiers. Construction and renovation activities within the office could also contribute to high levels of PM, particularly PM10.

The use of heating and cooling systems can re-circulate particles within indoor spaces, while poor ventilation might not efficiently filter indoor air and prevent outdoor particles from entering the building. For example, offices situated in urban areas or near roadways may experience higher levels of PM2.5 due to infiltration of outdoor air pollution.

Activities like cleaning, particularly without the use of high-efficiency particulate air (HEPA) filter-equipped vacuum cleaners, could also stir up particles and contribute to high PM levels. Furthermore, materials used in office furnishings, flooring, or wall coverings may also emit particles into the indoor environment.

Individual activities can significantly impact PM levels: actions such as vaping in the office, smoking next to doorways and windows, or frequently opening windows to busy streets invite these pollutants into the workspace. Thus, maintaining good office etiquette can also contribute to lower PM10 and PM2.5 levels indoors.

PM10 vs PM2.5: The Health Impacts

The main difference between PM10 and PM2.5 is their size, but this difference in size also means they have different properties and health impacts. 

PM10 are small enough to be inhaled and can be detrimental to human health, but are usually filtered out in the throat and nasal passages. 

On the other hand, PM2.5, also known as fine particles, are so small that they can penetrate the lungs and enter the bloodstream, causing a variety of health problems such as respiratory issues, and worsening existing heart and lung conditions.

Summary of Differences

  PM10 PM2.5
Aerodynamic Diameter Smaller than 10 micrometers (μm) Smaller than 2.5 micrometers (μm)
Description Coarse dust Fine dust
Sources Wind-blown dust, crushing/grinding operations, agricultural works, industrial emissions, road traffic Burning of fossil fuels, vehicle emissions, power plants, industrial processes, residential wood burning, forest fires, agricultural burning
Health Impacts Can be inhaled and cause health issues, but is usually filtered out in the throat and nasal passages Can penetrate the lungs, enter the bloodstream, and cause respiratory issues and worsen heart and lung conditions
Indoor Sources Any type of combustion - primarily cooking (such as from office kitchens or cafeterias) Sweeping, carpets, mud / dust being brought indoors from people's shoes

PM10 and PM2.5 in IAQ Monitoring

Monitoring the levels of both PM10 and PM2.5 in the indoor air helps maintain a healthy indoor environment. The type, size, and concentration of PM can often give clues about the sources, their potential health impacts, and strategies for their control.

Continuous monitoring over long periods of time can be particularly useful to detect unusual changes in PM concentrations – which can be especially important in instances where external events contribute to their increased levels, such as during wildfire seasons or periods of high outdoor pollution. 

When evaluating commercial IAQ monitors, ensure you choose an IAQ monitor that can detect both PM10 and PM2.5, which will provide a comprehensive understanding of your indoor air quality.

What about PM1 and PM0.1?

When discussing particulate matter, you might also come across references to PM1, PM0.1, etc. Just like PM10 and PM2.5, these refer to the particle sizes in ambient or indoor air. PM1 represents particles with an aerodynamic diameter smaller than 1 μm, PM0.1 represents those smaller than 0.1 μm, and so forth.

While it's possible in theory to measure such ultrafine particles, keep in mind the practical limitations of measurement. Most personal and commercial monitors use laser light scattering technology to detect particulate matter, and the accuracy of particulate matter detection primarily relies on the performance of said laser light. The physical limit of laser light wavelength limits how small of a particle can be measured and would typically not be accurate with particles smaller than 0.3 μm. Some monitors can accurately measure PM0.1, but they would be using other technology - and you should inquire further to understand which tech is being used to validate such claims.

Moreover, even if some devices provide data points for PM1 or similar sizes, it’s pertinent to question the practicality of this information. The health or environmental impacts of different sizes of particulate matter, and therefore, the guidelines for good or bad levels of these pollutants, are predominantly based on studies on PM10 and PM2.5.