EPA’s plan to stop regulating tailpipe emissions forces states to make a choice: compensate by clamping down harder on pollution within their borders, or risk violating the Clean Air Act.
That’s the message that state officials from around the country are relaying to EPA. In comments on the agency’s proposal, officials argued that a patchwork of state regulations would be more expensive and less effective than keeping federal rules that limit pollution from cars and trucks.
But the alternative, they said, would be to blow a hole in state climate targets — and violate federal standards for safe air quality.
“Without reductions from vehicles, states must more and more aggressively squeeze emissions reductions from stationary sources or develop burdensome regulations of consumer products,” Minnesota state agencies wrote in comments to EPA’s proposal.
The Trump administration plans to stop regulating planet-warming pollution from cars and trucks, as part of its push to overturn the 2009 endangerment finding. The finding, which is the legal underpinning for most federal climate rules, states that greenhouse gases harm human health by driving climate change.
During EPA’s comment period for its proposal — which ended Sept. 22 — state officials urged the agency to reverse course. They pointed out that the only way to compensate for a retreat in federal vehicle standards would be to impose state-level regulations on other sectors of the economy.
Transportation is the largest source of U.S. greenhouse gases. Vehicles are also a leading source of conventional pollutants that harm public health, and which states are required to control under the Clean Air Act.
EPA’s proposal would leave in place Biden-era standards for so-called criteria pollutants that contribute to ozone, particulate matter and air toxics. But it would jettison climate rules that would accelerate the shift toward electric vehicles — a transition that promised cuts in localized pollution.
“It is going to create more pollution, and it’s going to create fewer choices for states and locals to address that pollution unless they can figure out a way around what looks like a very high bar,” said Miles Keogh, executive director of the National Association of Clean Air Agencies (NACAA).
“What it means is we’re going to get emission reductions wherever we have the authority to advance those clean air protections,” he said.
Air quality compliance at risk
States are required to submit plans to EPA for how they will meet the Clean Air Act’s National Ambient Air Quality Standards (NAAQS) for pollutants that harm public health — like ozone and particulate matter.
Those state implementation plans, or SIPs, detail how states will keep their pollution at or below EPA-approved limits. That task becomes harder as federal climate rules disappear — along with their co-benefits for local air pollution — and some regions see a baseline pollution spike.
Requiring states to offset the pollution previously abated by federal regulations amounts to an “unfunded mandate,” NACAA wrote in its comments to EPA.
“Various states have relied on the emission reductions provided by these federal standards to demonstrate future attainment of ozone and PM standards,” the group wrote. “The withdrawal of these standards would create a significant ‘gap’ and immediate compliance challenges for numerous nonattainment areas. States would be required to identify alternative emission reduction measures to maintain their approved implementation plans.”
The alternatives available to states, NACAA’s leaders wrote, “generally achieve emission reductions at higher per-ton costs and often face greater implementation challenges.”
A state could also lose federal highway funds if it fails to deliver on its implementation plan. That risk might be particularly acute for blue states like California under the Trump administration, which has shown a zeal for slashing federal funding to states that aren’t politically aligned with the president.
In February, EPA threatened to reject the South Coast Air Quality Management District’s plan to attain compliance with federal standards for ozone. The move — which EPA has deferred — could cost the Los Angeles region billions of dollars in federal highway funds.
The South Coast region has never been in compliance with ozone standards despite some of the toughest regulations in the country. In a February statement, the management district noted that more than 80 percent of the area’s smog-forming emissions come from motor vehicles, ships, planes and other sources the district has no regulatory authority over.
“Meeting national air quality standards is impossible unless these mobile source emissions under U.S. EPA authority are substantially reduced,” it stated.
Ann Carlson, director of the Emmett Institute on Climate Change and the Environment at UCLA, said vehicle standards are the most effective way to bring Southern California in compliance with federal ozone standards.
“If they shut down all their stationary sources and they just said, ‘OK, you can no longer operate,’ we’d still be out of compliance standards,” she said.
Congressional Republicans and the Trump administration have rescinded California’s waiver to implement its own vehicle standards — though that is still being litigated — at the same time as EPA moves to scrap its own clean car and truck rules.
“So at the same time they’re threatening to sanction [California], they’re also taking away the most effective tool California has to meet the standard,” said Carlson.
Some questioned whether the Trump administration — which has proposed loosening the NAAQS — would follow through on the lengthy process of rejecting a state’s plan and replacing it with a new abatement plan that would ultimately result in stronger limits on businesses.
“That sort of thing does happen from time to time, but it’s a long process. EPA can’t come down like a ton of bricks,” said Michael Gerrard, faculty director at Columbia University’s Sabin Center for Climate Change Law. “EPA can’t automatically jump in and require further action. Obviously, the current EPA wouldn’t anyway.”
But future EPAs might.
John Graham, a senior scientist at the Clean Air Task Force, noted that the history of the NAAQs shows that pollution limits tend to tighten over time as epidemiological studies show that lower and lower concentrations of pollutants harm public health. That could mean new parts of the country become out of compliance.
“If that standard is likely to change in the next three decades, which it could very well do, then these rules become even more important,” he said.
In response to questions, EPA issued a statement saying the agency is “following all of its statutory obligations under the Clean Air Act.”
Even if Trump’s EPA doesn’t impose sanctions on states and localities that fail to meet the NAAQS standards, citizens or nonprofits can still sue states for noncompliance. Activists are already signaling they’ll use litigation as a backstop to protect public health and the climate if EPA repeals the endangerment finding and vehicle standards.
“To the extent EPA is not doing [enforcement], I can guarantee that others will be,” said Greg Cunningham, vice president for clean energy and climate change at the Conservation Law Foundation.
‘Near zero’ chance of hitting climate goals
State commenters questioned whether they could scrape together enough emissions cuts to make up the difference if EPA gets rid of its greenhouse gas rules.
In Oregon, where state law requires deep emissions cuts by 2050, officials said federal vehicle standards had allowed the state to decarbonize while still growing the economy. Trying to achieve the same result through state regulations, they said, would harm the state’s growth for a fraction of the benefits.
“Without federal greenhouse gas emissions standards, Oregon would be left with a patchwork of state-level policies that cannot achieve the same extent of reductions in emissions,” Oregon Department of Environmental Quality Director Leah Feldon wrote in comments to EPA.
“Removing these standards would make it far more difficult, if not impossible, to achieve the state’s legally binding emission reduction targets,” she wrote.
In Washington state, where a cap-and-invest system covers the state’s biggest polluters, some officials warned that state law would force the state to balance a rise in vehicle pollution by clamping down on other, nontransportation sectors. But state agencies expect to get less juice from the squeeze.
“The federal standards are already not stringent enough to meet Washington’s greenhouse gas limits — in this scenario, if they are repealed as proposed, our ability to meet our limits would be near zero,” Washington state agencies wrote to EPA.
North Carolina officials warned that worsening air pollution would have “severe consequences” for public health as well as the state’s economic competitiveness.
“One of the first questions corporations ask when they are evaluating the location of a manufacturing facility in the state is if the area in which they are evaluating complies with all the NAAQS,” wrote Michael Abraczinskas, director of the Division of Air Quality at the North Carolina Department of Environmental Quality.
“For Mecklenburg County and adjacent counties, we are proud to say that, yes, the area complies with all the NAAQS, and we intend to keep it that way,” he wrote.
Turning to stationary sources
States and regional authorities can’t regulate mobile sources directly — at least, not unless the courts ultimately overturn EPA’s repeal of California’s waiver.
But there are new strategies states and local regulatory authorities may pursue to limit vehicle emissions indirectly.
EPA last year allowed the South Coast regional authority to include its “indirect source rule” for warehouses in California’s state implementation plan to decrease nitrogen oxides and particulates. Warehouses — like rail yards and ports — are hubs for high-emitting long-haul trucks that spew criteria and climate pollution. The rule requires warehouses to formulate plans to reduce overall emissions via installing electric vehicle charging infrastructure, limiting trips by diesel-burning trucks and other options.
It’s less efficient than fleetwide vehicle emissions standards, and more costly for warehouse owners. But its a strategy states and regional authorities may use to limit pollution at other warehouses, rail yards and ports around the country. And while EPA had to sign off on adding it to California’s SIP, states and regional authorities don’t require federal permission to regulate local infrastructure.
States also have wide leeway to electrify their own fleets of government vehicles. Subsidizing EVs, building charging stations and other incentives also remain available.
The Clean Air Act allows states to regulate stationary sources, like manufacturing, oil and gas development and power generation. But that’s complicated by tight electricity demand, high prices and public concern about the economy.
“States can impose all kinds of requirements on their stationary sources,” Gerrard said. “But often that’ll chase companies out of town, and cause electric rates to go up and lots of other bad things that states want to avoid.”
The Edison Electric Institute, which represents investor-owned utilities, filed comments urging EPA not to repeal the greenhouse gas endangerment finding. While the draft rule doesn’t directly undo Biden-era power plant carbon rules, EPA is working separately to roll those back.
EEI noted that repealing the scientific finding would leave the power sector unregulated for climate change at the federal level.
But it would do nothing to roll back state climate laws.
“Many EEI members serve customers in states with existing state policies for [greenhouse gas] emissions,” wrote EEI regulatory lead Alex Bond. Those policies are already shaping those companies’ investments, he said.
“Settled” federal standards would do more to lessen regulatory uncertainty, he said, than a regulatory void at the federal level that would be filled with “competing and conflicting regulations through a patchwork of state regulations.”
