National Ambient Air Quality Standards

There are two sizes of particulate matter: PM_2.5 and PM₁₀.

PM_2.5 or less in diameter is produced by industrial processes, heating boilers and engines. Particulate matter can clog lung sacs and may pass into bloodstream. Often they carry toxic and carcinogenic materials.

The National Ambient Air Quality Standard for PM2.5 24-hour standard is 35 micrograms per cubic meter of air (µg/m3). The annual standard for PM2.5 is 12.0 µg/m3, averaged over three years.

PM₁₀ or less in diameter is produced by dust from construction sites, wildfires, and industrial sources.

The National Ambient Air Quality Standard for PM10 24-hour standard is 150 (µg/m3).

For more information, visit the U.S. EPA website.

Sulfur dioxide comes from the burning of coal and oil and industrial processes. It can be corrosive to outdoor structures and causes acid rain. Sulfur dioxide aggravates lung conditions.

The National Ambient Air Quality Standard for sulfur dioxide hourly average is 75 parts per billion.

For more information, visit the U.S. EPA website.

Nitrogen dioxide is emitted from industrial processes and vehicle exhaust. It causes structural damage to lungs and lowers resistance to respiratory infections. Nitrogen dioxide is a precursor to smog and also causes acid rain.

The National Ambient Air Quality Standard for nitrogen dioxide 100 parts per billion, having a 1-hour averaging time. The annual standard for nitrogen dioxide is 53 parts per billion.

For more information, visit the U. S. EPA website.

Ozone is formed when volatile organic compounds and nitrogen oxides react in presence of heat and sunlight. It is the main component of smog. Ozone irritates mucous membranes, causing coughing, choking and impaired lung function. It also aggravates asthma and bronchial conditions.

The National Ambient Air Quality Standard for ozone 8-hour average is 70 parts per billion.

For more information, visit the U.S. EPA website. 

Lead is produced by industrial sources, lead smelters, foundries, metals processing and piston-engine aircraft operating on leaded aviation gasoline. Lead in air can be inhaled or ingested after it settles onto surfaces. Lead can be absorbed into the bloodstream and can affect many of the body's organs.

The National Ambient Air Quality Standard for lead is 0.15 micrograms per cubic meter of air (µg/m3) having a 3-months averaging time.

For more information, visit the U.S. EPA website.