Particulate Matter (PM), also known as soot, is made of microscopic solid particles or liquid droplets that are either emitted directly into the air or formed by pollutants that combine in the atmosphere. PM is usually measured in three size ranges, which are the most harmful to health: PM10, PM2.5, and PM1
PM10 or coarse dust particles refer to particles with a diameter less than or equal to 10 microns in size. They are about 30 times smaller than the width of a human hair and are small enough to evade our defensive nose hairs and get inhaled into our lungs. Sources of this PM10 include crushing/grinding operations, and dust stirred up by vehicles. Pollen, mold, and plant and insect particles are also considered PM10. Finally, the evaporation of sea spray can also produce large particles in coastal areas.
Dangerous level: 125 μg/m³ (microgram per cubic meter) or more.
PM2.5 or fine particles are 2.5 micrometers in diameter or smaller. Fine particles are produced from all types of combustion, including motor vehicles, power plants, residential wood burning, wildfires, agricultural burning, and some industrial processes. While PM10 ends up in your lungs, PM2.5 is more dangerous as it can transfer from your lungs into your bloodstream. From your bloodstream, it can it end up anywhere in your body, thereby making it “the invisible killer”.
Dangerous level: 90 μg/m³ or more.
PM1 – particulate matter with a diameter smaller than 1 micron – is a major subset of PM2.5. These are extremely fine particles that are even more likely to reach deeper into the respiratory system than PM2.5. PM1 is the by-product of emissions from factories, vehicular pollution, construction activities, and road dust. It is not dispersed and stays suspended in the air that you breathe.
Dangerous level: 61 μg/m³ or more.