Air Quality: PM2.5

What is PM 2.5?

Particulate matter, or PM2.5, is very small particles in air that are 2.5 micrometers (about 1 ten-thousandth of an inch) or less in diameter. This is less than the thickness of a human hair. Particulate matter, one of six U.S. EPA criteria air pollutants, is a mixture that can include organic chemicals, dust, soot and metals. These particles can come from cars and trucks, factories, wood burning, and other activities.

Why is this indicator included in CalEnviroScreen?

The smaller the particles, the deeper they can move into the lungs when we breathe.
Fine particle pollution has been shown to cause many serious health effects, including heart and lung disease.
Exposure to PM2.5 contributes to deaths across California.
Children, the elderly, and people suffering from heart or lung disease, asthma, or chronic illness are most sensitive to the effects of PM2.5 exposure.

What measure is used in CalEnviroScreen 4.0 to evaluate PM 2.5?

The California Air Resources Board measures PM2.5 concentrations from air monitoring stations around the state.
The indicator combines PM2.5 concentrations from monitors along with satellite observations estimated at a 1 kilometer grid.
PM 2.5 annual means were extracted from the air monitors for 2015-2017 and a mean was calculated by averaging across the three years.
A spatial model was created with the air monitoring and satellite data to estimate PM2.5 concentrations for each census tract within 50 km of an air monitoring station.
For census tracts further than 50 km of an air monitor, satellite observations were used to assign a PM 2.5 concentration.
A complete description of the PM 2.5 indicator can be found in the CalEnviroScreen 4.0 report.