Particulate Matter Pollutants and Sources

Particulate matter refers to a mixture of solid particles and liquid droplets found in the air. Some of these particles are large enough to be seen with the naked eye. Others are so small they can only be detected using a microscope.

Fine particulate matter smaller than 2.5 micrometers (or microns) in diameter is called PM_2.5. To help understand this size, the diameter of a single human hair is about 50 to 70 micrometers. Industrial, residential and motor vehicle fuel combustion emits fine particles into the air. Fine particles also form in the atmosphere when chemical reactions in the air transform gaseous air pollutants such as sulfur dioxide, nitrogen oxides and organic compounds into microscopic solid or liquid particles.

Health Effects of Particulate Matter

Since particulate matter is so small, particles can be inhaled deep into the lungs. Inhaling high concentrations of particulate matter has been associated with an increased risk of heart attacks, acute and chronic bronchitis, asthma attacks and other respiratory issues for individuals with pre-existing heart or lung conditions. 

Air Quality Standards and Monitoring

The primary National Ambient Air Quality Standards (NAAQS), based on health effects, for PM_2.5 are a concentration of 35 micrograms of PM_2.5 per cubic meter of air (µg/m3) averaged over 24 hours (98th percentile, averaged over three years) and 12 µg/m3 annual average (averaged over three years). 

Particulate matter smaller than 10 micrometers in diameter is called PM₁₀. PM₁₀ includes PM_2.5 and also coarser particles between 2.5 and 10 micrometers in diameter, including airborne dust emitted into the air from industrial processes, agricultural activity, and unpaved roads. PM₁₀ is also inhalable.

The primary NAAQS, based on health effects, for PM₁₀ is 150 µg/m3 averaged over 24 hours (not to be exceeded more than once per year on average over three years).

Missouri monitors particulate matter concentrations in the air at locations across the state. Click on the Monitoring tab to learn more about these air monitoring sites. Explore the Data tab below to learn more about the data collected from this sites.