Benton Clean Air Agency

Air Quality and Health

The U.S. Environmental Protection Agency (EPA) establishes National Ambient Air Quality Standards for six criteria pollutants. The chart below provides key information on each of these pollutants. To learn more about the two pollutants of most concern in Benton County (fine particles and coarse particles) click here.

Criteria Pollutant

Description & Standard


Health Effects

Particulate Matter Up to 10 Microns in Diameter (PM10)

Particles less than 10 microns in diameter in size. 24-hour Standard: 150 micrograms per cubic meter of air, averaged over 24 hrs.

Dust stirred up from paved and unpaved roads, construction activities, windblown dust.

When inhaled, fine particles travel deep in the lungs, damaging delicate lung tissue. Especially harmful to those suffering from existing heart and lung diseases, as well as the pregnant, young children, and the elderly.

Fine Particulate Matter Up to 2.5 Microns in Diameter (PM2.5)

Fine particles less than 2.5 microns in diameter in size. 24-hour Standard: 35 micrograms per cubic meter of air, averaged over 24 hrs. Annual Standard: 15 micrograms per cubic meter of air.

Combustion-related, motor vehicles, wood burning, open burning, industrial processes.

(same as above)

Carbon Monoxide (CO)

An odorless, tasteless, colorless gas which is emitted from any form of combustion. Standard: 9 parts per million, averaged over 8 hrs.

Automobiles, wood burning devices, outdoor burning, and industrial combustion sources.

Deprives the body of oxygen by reducing the blood’s capacity to carry oxygen: causes headaches, dizziness, nausea, listlessness and in high doses, may cause death.

Ozone (O3)

Formed when nitrogen oxides and volatile organic compounds react in the presence of sunlight. A component of smog. Standard: 0.075 parts per million, averaged over 8 hours.

Automobiles, industry, gasoline storage and transfer, gasoline refueling, paints, solvents.

Irritates eyes, nose, throat, and respiratory system; especially bad for those with chronic heart and lung disease, as well as the very young and old, and pregnant women.

Nitrogen Dioxide (NO2)

A poisonous gas produced as a byproduct of high combustion temperatures. Standard: .053 parts per million, annual average.

Effective 4/12/2010 - EPA established a new 1-hour standard of 100 parts per billion (0.100 ppm)

Fossil fuel power generation, mobile sources, industrial combustion processes.

Harmful to lungs, irritates bronchial and respiratory systems; increases symptoms in asthmatic patients.

Sulfur Dioxide (SO2)

A gas resulting from the burning of sulfur-containing fuel. Standard: .14 parts per million, averaged over 24 hours.

Effective 8/23/2010 - EPA is establishing a new 1-hour standard of 75 parts per billion (0.075 ppm) and revoking the 24-hour and annual standards.

Fossil fuel power plants, non-ferrous smelters, pulp production, primary aluminum production.

Increases symptoms in asthmatic patients; irritates respiratory system.

Lead (Pb)

Lead emissions throughout the country have been significantly reduced since the conversion to unleaded gasoline. Between 1976 and 1995, ambient levels of lead declined 97%.

Effective 1/12/209 - EPA established a new standard of 0.15 micrograms per cubic meter of air for a 3-month rolling average.

Smelters and battery plants.

Affects motor function and reflexes and learning; causes damage to the central nervous system. Kidneys and brain. Children are affected more than adults.