Air Quality Pollutants and Standards

The Sac Metro Air District is responsible for developing plans and programs to attain state and federal air quality standards. More information on these plans and programs can be found by clicking here.

Current Federal and State Standards

The U.S. Environmental Protection Agency (EPA) has established National Ambient Air Quality Standards (NAAQS) for six common pollutants (referred to as criteria pollutants), which are known to be harmful to human health and the environment. These pollutants are:

Ozone (O₃)
Particulate Matter (specifically, particulate matter less than 2.5 microns in diameter (PM_2.5)andparticulate matter less than 10 microns in diameter (PM₁₀))
Carbon Monoxide (CO)
Lead (Pb)
Sulfur Dioxide (SO₂), and
Nitrogen Dioxide (NO₂).

For several of these pollutants, California has also set standards, which are more stringent than federal standards. In the table below, links have been established to find out more information for each pollutant, planning boundary maps and designations. Locations of air monitoring stations can be found on the Air Monitoring page.

Pollutant	National Standard	Federal Designation and Classification (attainment date)	California Standard	State Designation¹
Ozone	8-hr Std (2015 NAAQS) 0.070 ppm	Nonattainment Serious³	8-hr Std⁴ 0.07 ppm	Nonattainment
	8-hr Std (2008 NAAQS) 0.075 ppm	Nonattainment Severe-15
	8-hr Std (1997 NAAQS) 0.08 ppm (revoked)	Nonattainment Severe-15
	1-hr Std (1979 NAAQS) 0.12 ppb (Revoked)	Nonattainment⁵ Severe-15	1-hr Std (1988) 0.09 ppm	Nonattainment
Particulate Matter 2.5 microns (PM_2.5)	24-hr Std (2012 NAAAQS) 35 µg/m³	Nonattainment² Moderate
	Annual arithmetic (2024 NAAQS) 9 µg/m³	To be determined10
	Annual arithmetic (2012 NAAQS) 12 µg/m³	Attainment	Annual Arithmetic 12 µg/m³	Attainment
Particulate Matter 10 microns (PM₁₀)	24-hr std (1987 NAAQS) 150 µg/m³	Attainment - Maintenance Moderate (2013)	24-hour Std 50 µg/m³	Nonattainment
Particulate Matter 10 microns (PM₁₀)	24-hr std (1987 NAAQS) 150 µg/m³	Attainment - Maintenance Moderate (2013)	Annual arithmetic mean 20 µg/m³	Nonattainment
Carbon Monoxide	1-hr Std (2011 NAAQS) 35 ppm⁶	Attainment (1998)	1-hr Std 20 ppm	Attainment
Carbon Monoxide	8-hr Std (2011 NAAQS) 9 ppm⁶	Attainment (1998)	8-hr Std 9 ppm	Attainment
Lead	3-month rolling (2008 NAAQS) 0.15 µg/m³	Attainment (2011)	30-day average 1.5 µg/m³	Attainment
Sulfur Dioxide	1-hr Std (2010 NAAQS) 75 ppb	Unclassifiable/ Attainment⁷	1-Hr Std 0.25 ppm	Attainment
Sulfur Dioxide	1-hr Std (2010 NAAQS) 75 ppb	Unclassifiable/ Attainment⁷	24-hr avg Std 0.04 ppm	Attainment
Nitrogen Dioxide	1-hr Std (2010 NAAQS) 0.100 ppm	Unclassifiable/ Attainment⁸ (2012)	1-hr Std 0.18 ppm	Attainment (2012)
Nitrogen Dioxide	Annual Arithmetic Mean (2010 NAAQS)⁹ 0.053 ppm	Unclassifiable/ Attainment⁸ (2012)	Annual arithmetic mean 0.030 ppm

¹ Summary of Historical Designations for State air quality Standards can be found here. A list of pollutants for which California Ambient Air Quality Standards were established and more information on the health and environmental effects specific to each pollutant can be found here.

²EPA issued Determination of Attainment on 05/10/2017 (82 FR 21711) but the Sacramento Federal PM_2.5 Nonattainment Area has not yet been redesignated to Attainment.

³ EPA is currently processing Air Districts' reclassification request from Serious to Severe-15.

⁴ In 04/2005, the California Air Resources Board (CARB) approved a new 8-hour standard of 70 ppb and retained the 1-hour standard of 90 ppb.

⁵ EPA issued Determination of Attainment on 10/18/2012 (77 FR 64036) but the Sacramento Federal Ozone Nonattainment Area has not yet been redesignated to Attainment.

⁶ The original NAAQS was established in 1971. EPA reviewed both the 1-hour and 8-hour standards and decided to retain these standards in 2011.

⁷ Attainment /Unclassifiable designation was made as part of EPA's Air Quality Designations for the 2010 Sulfur Dioxide (SO₂) Primary NAAQS - Round 3 designation in 12/2017.

⁸ EPA designates areas as "unclassifiable/attainment" if they met the standard or are expected to meet the standard despite a lack of monitoring data.

⁹ The original NAAQS were established in 1971. EPA reviewed and decided to retain the annual arithmetic mean standard in 2010.

10 EPA is working to determine the area designations for the updated annual PM2.5 standard, established February 7, 2024. Designations will be released February 2026. More information on the designation process and timeline can be found here.

Other California Standards

California has also set standards for four pollutants (Hydrogen Sulfide, Sulfates, Visibility-Reducing Particles and Vinyl Chloride) that do not have a federal standard.

Parameter	California Standard	State Designation
Hydrogen Sulfide (H₂S)	1-hr Std 30 ppb	Unclassified
Sulfates	24-hour std 25 µg/m³	Unclassified
Visibility-Reducing Particles	Statewide - 0.23 per km¹¹ Lake Tahoe Air Basin - 0.07 per km¹²	Unclassified
Vinyl Chloride	24-hour 10 ppb	Unclassified

¹¹ The statewide standard, the extinction of 0.23 per km, is equivalent to the standard adopted by CARB in 1969, defined as particles "in sufficient amount to reduce the visibility to less than ten miles when the relative humidity is less than 70 percent.

¹² The Lake Tahoe Air Basin standard, the extinction of 0.07 per kilometer, is equivalent to the standard adopted by CARB in 1976, defined as particles "in sufficient amount to reduce the prevailing visibility to less than 30 miles when relative humidity is less than 70 percent.