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EPA Takes Action to Ensure California Meets Nation's Air Quality Standards

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WASHINGTON (Sept. 24, 2019) — Yesterday, U.S. Environmental Protection Agency (EPA) Administrator Andrew Wheeler sent a letter to California Air Resource Board (CARB) Chairman Mary Nichols notifying her of the Trump Administration’s forthcoming action to eliminate its backlog of California State Implementation Plans (SIPs). This action is a necessary step toward ensuring compliance with EPA’s National Ambient Air Quality Standards (NAAQS) designed to ensure that all Americans have clean air.

“California has failed to carry out its most basic responsibilities under the Clean Air Act, and as a result, millions of Californians live in areas that do not meet our nation’s air quality standards,” said EPA Administrator Andrew Wheeler. “EPA stands ready to work with California to meet the Trump Administration’s goal of clean, healthy air for all Americans, and we hope the state will work with us in good faith.” 

The state of California represents a disproportionate share of the national list of backlogged SIPs, including roughly one-third of EPA’s overall SIP backlog. As most of these California SIPs are inactive and do not meet the minimum threshold of public health protection necessary for approval, they must either be redone or withdrawn. As a first step, EPA is calling on California to immediately withdraw inactive SIPs that would most likely be denied. If California does not withdraw the inactive SIPs in a timely manner, EPA will begin the process of evaluating these SIPs for disapproval and developing Federal Implementation Plans that are approvable and will protect public health.

Disapproval of a SIP triggers statutory clocks for:

  • Highway funding sanctions, which could result in a prohibition on federal transportation projects and grants in certain parts of California.
  •  New Source Review permitting sanctions.
  •  A deadline for the issuance of a Federal Implementation Plan (FIP).

“We certainly want to avoid these statutory triggers, but our foremost concern must be ensuring clean air for all Americans. That is our goal,” added Wheeler.

EPA has made reviewing and approving or disapproving of SIPs a priority to meet its goal of providing regulatory certainty with regard to Clean Air Act implementation. This is particularly relevant for SIPs, which provide important air quality benefits to impacted communities. California’s extensive backlog is due to approvability issues, state-requested holds, missing information, or resources. California has the worst air quality in the United States, with 82 nonattainment areas and 34 million people living in areas that do not meet NAAQS—more than twice as many people as any other state in the country.


A SIP is a collection of regulations and documents used by a state, territory or local air district to reduce air pollution in areas that do not meet NAAQS. EPA has established the NAAQS for six criteria air pollutants known to be harmful to human health: carbon monoxide, lead, nitrogen oxide, ozone, particulate matter, and sulfur dioxide. SIPs provide a plan for implementation, maintenance and enforcement of the NAAQS in each state. To learn more, visit