What is the Difference Between PM2.5 and PM10?

Particulate Matter & Air Pollution: What is the Difference Between PM2.5 and PM10?

While air pollution has been around as long as humans have, the industrial revolution brought about a significant increase in recent air pollution with the burning of fossil fuels, the invention of the automobile, and the creation of large, commercial agricultural areas. In 2019, 99% of the world population was living in places where the WHO air quality guideline levels were not met. People exposed to air pollution may experience eye, nose, or throat irritation, shortness of breath, aggravated asthma, respiratory problems, cardiovascular issues, and even premature death. Particulate matter in the air contributes to poor air quality, pollution, and negative health impacts. Read on to learn more about particulate matter categories, sources, and ways to understand and reduce your exposure to particulate matter.

Understanding Particulate Matter

Understanding particulate matter is key to understanding air pollution. Airborne particulate matter (PM) is “not a single pollutant, but rather a mixture of many chemical species”, and particulate matter can include hundreds of different chemicals. Particulate matter is made up of liquid or solid microscopic particles in the air and can come from either natural or man-made sources. The more particulate matter in the air, the more air pollution in the area. The two main categories of particulate matter are PM2.5 and PM10, which are defined by their diameter size. A third subset of particulate matter is PM0.1, known as ultrafine dust. Much smaller than PM10 and PM2.5, scientists are only beginning to understand the health impacts of PM0.1. The focus of this article is on PM10 and PM2.5, as there is much more data on these two subsets of particulate matter.

PM10 is particulate matter that is 10 micrometers or less in diameter. PM2.5 is particulate matter that is 2.5 micrometers or less in diameter, and PM2.5 particles are generally described as fine particles. Therefore, PM2.5 is a subset within PM10, but due to its small size, PM2.5 has its own category. A great indication of sizing is to compare PM10 and PM2.5 with the size of a human hair. To put the size in perspective, a human hair is about 70 micrometers in diameter – making it around 30 times larger than the largest fine particle. Another example is a grain of sand, which is around 90 micrometers in diameter. Examples of particulate matter include dirt, soot, pollen, smoke, mold spores, and dust.

Both PM10 and PM2.5 are inhalable and pose health threats to humans. Since PM2.5 are smaller particles, they are more likely to travel farther and deeper into the lungs, while the larger PM10 particles end up on a surface area of the lungs. Due to their small size, PM2.5 also has the ability to enter the bloodstream and infiltrate other parts of the body, creating additional health risks. Particle build-up on and in the lungs can lead to tissue damage and inflammation, which can lead to aggravated asthma and respiratory problems noted earlier.

Reducing Exposure to PM Outside

So how do we reduce exposure to PM10 and PM2.5? The first way to reduce exposure is to understand the main sources of PM10 and PM2.5. PM2.5 fine particles primarily come from vehicles, such as cars, trucks, buses, construction equipment, and trains. PM2.5 particles are also released from burning fuel sources like wood, oil, and coal, or from forest fires. PM10 particles come from these sources and from construction sites, landfills, agricultural sites, industrial plants, and some indoor products. Your location plays a key role in your exposure to particulate matter – this is where the U.S. Air Quality Index comes in.

The U.S. Air Quality Index (AQI) is a free tool designed to give you a daily understanding of the air quality in your area. The AQI covers five major air pollutants identified by the Clean Air Act, including particulate matter PM10 and PM2.5. You simply type in your ZIP Code, City, or State, and air quality information is calculated for that day, based on a scoring system of 0 to 500. A score of 0 is best, while a score of 301 or higher is hazardous. This is a great way to better understand the air quality in your area.

To combat exposure to outdoor particulate matter, minimize time outside on poor air quality days or wear an N95 mask (especially if conditions are dusty or hazy). Avoid areas of higher pollution, which are typically freeways and busy areas of large cities.  

Reducing Exposure to PM Inside

While outside air particulate matter is a little more difficult to control, there are various ways to reduce indoor exposure to particulate matter. Avoid smoking (particularly indoors), utilize exhaust fans when cooking, avoid using wood-burning fireplaces, limit the use of air fresheners, candles, and cleaning products, and keep adequate ventilation to avoid excess moisture, which can lead to mold and aggravate allergies and asthma. To protect oneself against outdoor particulate matter in the home, close windows when air quality is poor, invest in doormats, take off shoes at the front door, vacuum regularly, and utilize a high-efficiency air filter and air purifier.


Even though PM10 and PM2.5 are separated into two categories, both are dangerous to human health. Following the AQI and implementing the previously mentioned techniques to reduce your exposure to poor air quality will help reduce your risk of experiencing associated negative health impacts. The best place to start when improving your indoor air quality is to upgrade your air filters to a MERV 13 filter and to utilize an air purifier that filters particles down to at least 0.3 microns in size. You can find both at the above links or at DiscountFilters.com.

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