Public Statement on Impact of Waiver Disapproval

What actions did the federal government take with respect to California’s regulations?

Under the federal Clean Air Act (CAA), the federal government sets emissions standards for motor vehicles nationwide. However, since California had adopted its own clean air regulations on vehicles before the federal Act was adopted, the CAA contains a special provision that allows California to enact stricter regulations than apply nationally. California has done so many times since the CAA was enacted in 1970, and the U.S. Environmental Protection Agency (EPA) has consistently and routinely approved California’s regulations under this CAA provision.

In 2025, in an unprecedented move, the Trump Administration reclassified EPA’s approval of three California motor vehicle regulations as “federal rules.” By calling these approvals federal rules, the Trump Administration claimed that they were subject to the Congressional Review Act, a seldom-used federal law from 1996 that allows Congress to revoke federal rules through a truncated process. The Trump Administration’s allies in Congress then voted to disapprove the California regulations, over the objections of the non-partisan Government Accountability Office and Senate Parliamentarian, both of whom determined that the Congressional Review Act process to disapprove federal rules did not apply. California and ten other states contend that this action was not allowed under the law and are challenging it in court.

What are the impacts of the rejected rules on pollution and health?

The key pollutants of concern are fine particulate matter (PM_2.5) and nitrogen oxides (NO_X). On-road mobile sources contribute to PM_2.5 through two different pathways: direct or “primary” particulate matter emissions and “secondary” PM_2.5 formation from gaseous precursors such as NO_X. While in the Bay Area on-road vehicles contribute a smaller share of regional primary PM_2.5, they are critical sources of NO_X emissions that drive secondary PM_2.5 formation. These pollutants are responsible for premature deaths, asthma, neurological impacts and many other health concerns. PM_2.5 aggravates cardiovascular and lung problems leading to many premature deaths. NO_X, in addition to causing its own health problems, combines with other pollutants in the atmosphere to form PM_2.5.

The rejected California regulations require clean vehicles to phase in over time, especially trucks. Since the requirements phase in, pollution reductions and therefore health benefits increase over time.

To put these numbers in context, the additional pollution that will directly result from the federal government’s actions is the same as putting 20,000-30,000 additional trucks on the road in the Bay Area in the 2030s.

The act of rejecting California’s regulations will also lead to as many as 400 excess deaths in the Bay Area between 2025 and 2050, and the rate of excess deaths will increase over time as the extra pollution increases over time. These are people who would be alive if these rules remain in place.

Will the rejection of California’s regulations conflict with other federal requirements?

In addition to significant health impacts, the rejection of California’s regulations will also make it harder for the Bay Area to meet federal clean air requirements.

In 2024, EPA strengthened the federal air quality standards for Particulate Matter to protect millions of Americans from harmful and costly health impacts, such as heart attacks and premature death. The Bay Area currently does not meet this stricter standard for PM_2.5 and will be required to submit a plan to reduce emissions to meet it. At the same time, the federal government is increasing pollution in the Bay Area by rejecting these important clean air regulations.

On-road vehicles account for 20% of NO_X emissions in the Bay Area. Rejecting these regulations will increase NO_X pollution in the Bay Area by around 2% in 2032, but that number will grow significantly over time.

It is anticipated that the Bay Area will have to reduce emissions to meet the stricter standards by 2032. The Bay Area will need to show that the plan will continue to meet the standard even as pollution from trucks goes up due to this federal action. These emissions reductions are likely to come from stationary sources. For example, oil refineries are one of the most significant stationary sources of NO_X. The Bay Area could theoretically achieve substantial NO_X reductions from refineries by requiring pollution standards already in place at the South Coast Air Quality Management District. Those South Coast rules were estimated to cost $2.36 billion to implement. Imposition of additional compliance costs on the refining sector would likely have significant economic impacts, including corporate decisions regarding the continued viability of their California assets.