Ground-level ozone, best known as smog, is an air pollutant seen primarily in the summer and fall which can inhibit breathing and damage respiratory systems at higher concentrations. Breathing ozone is akin to giving your lungs a sunburn: the pollutant damages healthy cells and prolonged exposure can lead to serious health impacts.
Ozone levels in Yolo-Solano are in the healthy range on most days. However, ozone and its precursors don’t respect political boundaries, and emissions created within Yolo and Solano counties do affect neighboring communities, especially in the greater Sacramento region. As such, the Yolo-Solano AQMD is included in the Sacramento Federal Non-attainment (SFNA) Area by the U.S. Environmental Protection Agency (EPA).
The U.S. EPA periodically reviews its air quality standards for regulated pollutants. The EPA may also revise its standards when health studies indicate that a revision is necessary to protect the most sensitive segments of the population.
Federal Ozone Attainment Plan
As a nonattainment area for the federal ozone standard, the Sacramento region is required to prepare various planning documents on an ongoing basis. Each time a new standard is adopted by EPA, local air districts must prepare plans to show how the standard will be achieved by the appropriate deadline.
1979 Ozone Standard (1 hour – 124 ppm) – The districts of the Sacramento region developed the attainment plan in November 1994, which shows how the region would attain the 1979 1-hour ozone NAAQS. The 1-hour standard was revoked in 2004. The EPA proposed approval of a clean data finding on May 18, 2011 (76 FR 28696) and final approval on October 18, 2012 (77 FR 64036). The region developed an attainment determination request in 2010 and a supplemental report in 2012. These documents were submitted to the EPA but never acted upon. The EPA asked that the request be updated under the redesignation substitution guidelines for the 2008 NAAQS. A Redesignation Substitution Request for the 1979 1-Hour ozone standard was prepared and approved by the Sac Metro Air District Board and submitted to ARB in October 2017 to be forwarded to the EPA. Once approved by EPA, this request will redesignate the SFNA to attainment and remove the previous Clean Air Act obligations associated with that standard.
The Exceptional Event Demonstration report shows how wildfires contributed to high 1 hour ozone concentrations in 2008.
1997 Ozone Standard (8 hour – 84 ppb) – The region developed the Sacramento Regional 8-Hour Ozone Milestone Report (2011) to demonstrate how existing control strategies have provided the emission reductions needed to meet the federal Clean Air Act requirements for reasonable further progress toward attainment of the 1997 8-hour NAAQS. In 2013 the regional air districts developed the Sacramento Regional 8-Hour Ozone Attainment and Reasonable Further Progress Plan to demonstrate how the region would attain the 1997 8-hour standard. This plan was approved by U.S. EPA effective March 2, 2015 (80 FR 4795).
The Federal Clean Air Act (CAA), Part D, Section 182(b)(2) requires ozone nonattainment areas to implement reasonably available control technology (RACT) for certain categories of sources. The District’s RACT SIP analysis (for the 1997 standard) was approved by the District’s Board of Directors in September, 2006. The analysis was initially disapproved by EPA in 2008 (73 FR 48166), but EPA subsequently proposed to approve on January 8, 2018 (83 FR 764) and issued a final approval on April 6, 2018 (83 FR 14754).
2008 Ozone Standard (8 hour – 75 ppb) – The District’s Board of Directors held a Public Hearing on October 11, 2017 and adopted the Sacramento Regional 2008 National Ambient Air Quality Standard (NAAQS) 8-Hour Ozone Attainment and Reasonable Further Progress Plan (Plan).
- Sacramento Regional 2008 NAAQS Attainment and RFP Plan
- Sacramento Regional 2008 NAAQS Attainment and RFP Plan – Appendices
The District’s RACT SIP analysis (for the 2008 standard) was approved by the District’s Board of Directors on September 13, 2017. On May 8, 2018 EPA proposed approval (83 FR 21235) of the District’s negative declarations, and on July 3, 2018 EPA finalized the approval (83 FR 31072).
The District was required to certify that our Nonattainment New Source Review (NNSR) program meets the requirements for the implementation of the 2008 ozone NAAQS. Our Board certified this on March 14, 2018 and submitted it to EPA.
2015 Ozone Standard (8 hour – 70 ppb) – In 2015, EPA promulgated a new 8-hour NAAQS of 70 ppb. In 2016, the California Air Resources Board recommended in their report that the Sacramento region be designated nonattainment (based on 2014-2016 monitoring data). The EPA published a final rule on June 4, 2018 (83 FR 25776) designating the Sacramento Metro area as moderate nonattainment.
State Ozone Plan
The California Clean Air Act (CCAA) of 1988 required submission of a plan for attaining and maintaining state ambient air quality standards for ozone with subsequent updates every three years. The District originally adopted an Air Quality Attainment Plan (AQAP) in 1991 and has completed seven triennial plan updates since then.
The most recent adopted triennial plan (May 2019) covers the years 2015-2017. The document summarizes emission trends over this time period, forecasts future emissions, and reviews efforts made by the District to improve air quality.