PO Box 15004, Flagstaff, AZ 86011-5004
Phone: (928) 523-0526
Fax: (928) 523-1266 Andy.Bessler@nau.edu
NTAA Air Topics:
NAAQS - Particulate Matter (PM)
The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for
pollutants considered harmful to public health and the environment. The Clean Air Act established two types of national air quality
standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such
as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against
decreased visibility, damage to animals, crops, vegetation, and buildings.
The EPA Office of Air Quality Planning and Standards (OAQPS) has set National Ambient Air Quality Standards for six principal pollutants,
which are called "criteria" pollutants. They are listed below. Units of measure for the standards are parts per million (ppm)
by volume, milligrams per cubic meter of air (mg/m3), and micrograms per cubic meter of air (µg/m3).
"Particulate matter," also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid
droplets. Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals,
metals, and soil or dust particles.
The size of particles is directly linked to their potential for causing health problems. EPA is concerned about particles that are 10
micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs.
Once inhaled, these particles can affect the heart and lungs and cause serious health effects. EPA groups particle pollution into two
"Inhalable coarse particles," such as those found near roadways and dusty industries, are larger than 2.5
micrometers and smaller than 10 micrometers in diameter.
"Fine particles," such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These
particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants,
industries and automobiles react in the air.