Ozone (O3)
Ozone (O3) is a gas whose molecules are composed of three oxygen atoms. Ozone is not emitted directly into the air, but is created by a chemical reaction between two precursors — oxides of nitrogen (NOX) and volatile organic compounds (VOC) — in the presence of sunlight. Ozone concentrations are expressed in parts per million (ppm) or parts per billion (ppb). High ground-level ozone concentrations can reduce lung function and increase respiratory symptoms, thereby aggravating asthma, bronchitis, or other respiratory conditions including chest pains and wheezing. Ozone exposure is associated with increased susceptibility to respiratory infections, cardiac-related effects, medical visits, school absenteeism and contributing to premature death, especially in people with heart and lung disease.
Reducing ozone to levels below state and federal standards is one of the primary goals of the Sac Metro Air District . As a nonattainment area, the region must evaluate air quality data and emission trends to determine how much ozone concentrations will need to be reduced to attain the standard in the future. Control measures and strategies are included as commitments in these plans to achieve the reductions in emissions of NOx and VOC necessary for the region to attain the standard. Information on the location of ozone monitors can be found on the Air Monitoring page.
1-hour std (1979 NAAQS)1 - 124 ppb | Nonaattainment2 (2010) | 1-hour std (1988)- 90 ppb | Nonattainment |
8-hour std (1997 NAAQS)1 - 84 ppb | Nonattainment3 | | Nonattainment |
8-hour std (2008 NAAQS) - 75 ppb | Nonattainment3 |
8-hour std (2015 NAAQS) - 70 ppb | Nonattainment5 |
Footnotes:
1 EPA revoked the 1979 1-hour and 1997 8-hour standards.
2 EPA issued Determination of Attainment on Oct 18, 2012 (77 FR 64036) but the Sacramento Federal Ozone Nonattainment Area has not yet redesignated the to Attainment.
3 The nonattainment area is classified as Severe-15.
4 In April 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 The nonattainment area is classified as Moderate for the 2015 NAAQS of 70 ppb (83 FR 25788).