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Here's Why Wildfire Experts Are Worried About an EPA Plan for Cleaner Air

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Smokey and hazy hillside.
The Berkeley Hills filled with smoke from the Butte County fire on Friday Nov. 9, 2018. (JP Dobrin/KQED)

Few laws have been as successful, or saved the United States as much money, as the Clean Air Act (PDF). First enacted in 1955, the act was a response to alarming disasters like the Donora Smog of 1948 in Western Pennsylvania and 1952’s Great Smog of London, where thick dirty air from factories and vehicles enveloped communities for days and caused widespread deaths.

Congress intended for the act to be frequently reevaluated and, if necessary, updated. The Environmental Protection Agency sets legal limits for how much pollution air districts are allowed to let into the air. Currently, the EPA is proposing tightening the standard for tiny particulates floating in the air, originating from motors, engines and fires.

Updating and tightening the standard is very popular among public health professionals, air regulators and the environmental justice community, who point to a mountain of evidence that this pollution takes lives early.

California Attorney General Rob Bonta, along with 17 other attorneys general, also supports limit tightening (PDF).

Many in the environmental justice community, concerned about the disproportionate air pollution burden that many lower-income communities and communities of color live with, would like to see standards tightened even further. In California, that’s especially true in the San Joaquin Valley and the South Coast Air Basin.


“We should have had lowered standards years ago. It’s a relief to see it now being proposed,” said Genevieve Amsalem, research and policy director at the Central California Environmental Justice Network. “Any time that you lower that standard, you’re going to be saving lives.”

She considers bad air the region’s biggest environmental public health threat, one that especially affects communities of color.

“Everyone knows a parent who has brought their baby, or their 2-year-old, into the ER because they couldn’t breathe. You know, the baby’s turning blue,” Amsalem said. “It’s a story you hear across generations.”

Data backs up this impression: Counties in the San Joaquin Valley consistently have among the worst rates of childhood asthma in the state.

But there are worries among the fire science community that the EPA’s proposed rule could have its opposite intended effect. They worry it may leave the state with ultimately worse air in the long run by stifling the use of prescribed fire. The ultimate outcome will affect everyone living in California and beyond.

“Wildfire is really challenging the paradigm that is at the core of the Clean Air Act — that emissions can be controlled,” said Michael Wara, an energy and climate scholar at Stanford University in a presentation to students and researchers.

“Wildfire emissions are not being successfully controlled. They’re growing,” he said.

The Clean Air Act was written during a time when smokestack air pollution was the key problem standing in the way of healthy air, and the U.S. Forest Service could seemingly put any wildfire out by 10 a.m. the next day. All over the country, wildfires bent more or less easily to the will of firefighters, and the big sources of pollution could be regulated at the emission’s source. But that was a different climate reality.

Clean air keeps people out of hospitals

Today, with emissions from the worst pollutants down by more than 70% (PDF), the EPA estimates the Clean Air Act saves 230,000 lives annually and hundreds of thousands more from asthma, bronchitis and heart attacks. Public health experts estimate the benefits of all these lives saved and hospital visits avoided into the many trillions of dollars.

Wildfires are now a major producer of both carbon emissions and tiny specks of sooty pollutants known as PM 2.5. A 2022 study from the National Center for Atmospheric Research found that wildfire pollution was beginning to reverse decades of clean air gains. (Researchers at Stanford in 2020 had similar findings [PDF].)

The EPA’s plan would update its standard for PM 2.5.

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Shorthand for “particulate matter of 2.5 microns in size or less,” PM 2.5 is a class of pollutants based on dimensions rather than origin or chemical makeup. It would take about 30 of them lined up to cross the width of a human hair. It’s their size that’s the key problem: It allows them to get deep into the lungs and even cross into the bloodstream, causing heart and respiratory problems. In short, it’s a terrible pollutant.

Public comment on the proposal closed late last month, and the EPA is now deciding whether and how to implement revisions.

The EPA estimates a third of the PM 2.5 we breathe in this country is from wildfires. For those in the West during wildfire season, it can be 90%.

And if wildfire trends continue and worsen, as climate models suggest they will, then we’ve seen nothing yet.

To avoid the worst outcomes, Wara of Stanford points to the need to dramatically increase the use of prescribed fire in pyro-adapted landscapes.

“Some of the best hopes that we have for reducing public health impacts from wildfire and [general] impacts from wildfire have to do with substituting prescribed fire emission for high-intensity wildfire emission,” he said.

The rub: Wildfire smoke vs. prescribed fire smoke

The EPA enforces its clean air standards. If air districts do not achieve these clean-air goals, then the EPA can take over air permitting within a district and even impose a ban on new federal highway grants.

However, EPA officials recognize that sometimes air districts are out of compliance through no fault of their own. In this case, they are allowed to file for an “exceptional event.” In this bureaucratic process, the “event” is linked to the cause of pollution going over the legal limit. It is meant for events that are unforeseeable and are unlikely to occur in the same location again, like a volcanic explosion. If the link can be made, then emissions from that event can be subtracted from the total, and the air district is no longer in trouble with the EPA.

To use an analogy, if you couldn’t pay off your credit card bill some month because you had an unforeseen emergency expense, this would be the process by which you might convince the credit card company to waive that charge.

An aerial view shows neighborhoods enshrouded in smoke as the Bobcat Fire advances toward foothill cities and new evacuation order go into effect on September 13, 2020 in Monrovia, California.
An aerial view shows neighborhoods in Monrovia enshrouded in smoke from the Bobcat Fire on Sept. 13, 2020. (David McNew/Getty Images)

It is a long, technically involved process. A California Air Resources Board (CARB) exceptional events filing (PDF) for ozone concentrations during the Northern California wildfires of 2020 runs 228 pages.

The problem, as seen by many in the wildfire science community, is that while this process essentially means air districts are not on the hook for wildfire smoke, they are on the hook for prescribed fire smoke. And prescribed fire — the most affordable, effective inoculation against future wildfires — has never been used as a basis for an exceptional event in California.

But fire scientists and those in fire agencies worry this new rule will stifle the state and federal plans to expand the use of prescribed fire as a core strategy to stem out-of-control wildfires.

“We’ve got to start doing larger prescribed burns if we want to make a difference to what is actually happening on our landscape,” said Scott Stephens, fire science professor at UC Berkeley. “That just means there’s going to be more smoke.”

Pro-prescribed-fire groups, including the National Association of Forest Service Retirees, have submitted comments detailing their concern (PDF) that the proposed rule “will reduce the Nation’s ability to implement strategies intended to reduce unwanted wildfire effects on communities and wildlands, including barriers to increasing the pace and scale of prescribed burning.”

A firefighter lights a prescribed burn in Humboldt County to reduce the underbrush without killing trees.
Prescribed burns, like this one in Humboldt County, reduce the underbrush without destroying trees. (Lenya Quinn-Davidson/NPR)

A large group of fire specialists, including professors, cultural burners and ecologists, wrote in a comment letter to the EPA that its plan “would put the EPA on the wrong side of policies and actions planned by federal, state, local and Tribal entities to address the wildfire crisis and ultimately, to reduce harmful PM2.5 emissions and impacts by reducing wildfire smoke.”

Smoke from prescribed fires is less intense and less damaging than smoke from wildfires. Many scientists view it as a protective trade-off — some pollution now in exchange for greater fire safety (and less pollution) in the future.

Air districts supportive, with qualifications

Both the California Air Resources Board and the Bay Area Air Quality Management District (PDF) have submitted comments supporting a tightening of the PM 2.5 standard. In interviews with KQED, regulators from both organizations also expressed support for prescribed burning.

Charles Knoderer, meteorologist at BAAQMD, said that the air district views prescribed burning as a partner and ally in lowering the risk of wildfires.

“We can control when they’re doing the burning and we can minimize the amount of smoke that’s released,” he said. “Wildfires will put out a ton more smoke, and at that point there’s really no controlling it.”

Neither Bay Area nor California air regulators seem to share the worries of the fire community that the EPA will hamper the increased use of prescribed fire, however.

Edie Chang, deputy executive officer at CARB, said her agency has heard from the prescribed-fire community and has brought up the issue in comments to the EPA.

“We’re trying to see how we can streamline or make suggestions for how EPA might modify their policies or their guidance to help us be able to balance the increased use of prescribed fire that we need for forest management, for managing and reducing the catastrophic wildfires that we experience in California,” said Chang.

She expressed hope that the rule’s implementation phase, which it now heads into, would be the time for nitty-gritty details to be worked out.

“Even though they can be expunged from the data, residents are still feeling [the effects of wildfire] very much so,” said Amsalem, of the Central California Environmental Justice Network. She hopes agencies will work out this issue, she said, “because we do need to do more prescribed burning to reduce the catastrophic events.”

EPA’s proposed workaround leaves burners skeptical

The EPA also seems aware of these concerns. In its proposed rule, it says it acknowledges stakeholder concerns about the importance of prescribed fire and intends to work with stakeholders to address these issues. It also says prescribed fires have the potential to qualify for exceptional events (PDF), which could encourage their continued and expanded use.

However, this has environmental lawyers very concerned. Sara Clark of the law firm Shute, Mihaly and Weinberger works with nonprofit organizations and supports prescribed fire and Indigenous cultural burners. She thinks the EPA’s reasoning as written might not hold up under a judge’s evaluation.

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“[The EPA] does a lot of linguistic acrobatics to try and clarify how a prescribed fire is … not reasonably preventable or controllable. But it’s called a ‘controlled burn,’” said Clark. “I’m concerned about the legal underpinnings there.”

She also believes that the time and technical expertise needed to file for an exceptional event exemption would make air regulators wary of using it. Extensive documentation and analysis is needed to submit for an exceptional events determination from CARB or the EPA.

A recent Government Accountability Office report echoes these concerns. The report says the EPA could do a better job working with other agencies to reduce impacts from wildfires (PDF), including making it easier to conduct prescribed fires.

Stakeholders interviewed by the GAO said that state and local agencies aren’t likely to use the exceptional events provision for prescribed burns because “the agencies would not likely approve prescribed burns that could cause National Ambient Air Quality Standards exceedances in the first place.” And they said that “exceptional event demonstrations are technically complicated and resource intensive.”

Put another way, it’s more likely that prescribed burns would never happen if air regulators thought they might have to file for an exceptional event.

It is also legally uncharted, or nearly uncharted, territory. The EPA has received only one exceptional events demonstration for a prescribed burn (PDF) — too much ozone was associated with prescribed burns in the Flint Hills of Kansas in December 2012. But since then, no tribal, state or local agency has submitted an exceptional event demonstration for a prescribed burn, according to EPA officials.

Should wildfires be considered exceptional?

The EPA’s proposed rule is based in part on the recommendations of the Clean Air Scientific Advisory Committee, a collection of public health experts. In their letter sent last spring to EPA administrator Michael Regan (PDF), they questioned whether even wildfires ought to be routinely considered exceptional events, considering they are the result of human-caused climate change, fire suppression and forest management policies and, often, problems with equipment.

“In some parts of the country, wildfires are no longer ‘exceptional’ The dramatic increase in wildfires over the last decade is not natural,” the authors write, pointing to forest management, climate change and utility power lines. “These are (in theory) at least partially controllable.”

In UC Berkeley’s Stephens’ view, the rule as proposed is an unacceptable passing of the buck.

“If you do proactive work like prescribed burning, you have to justify it through a rule that is onerous,” he said. “But if a wildfire is occurring, causing damage to people, burning down homes, no one’s accountable. I just don’t see how that can work.”

Of course, for those affected by the worst air quality in the state, pollution is damaging whether it’s from a diesel engine, a prescribed fire or a catastrophic wildfire.

Most people interviewed for this story said they hope that as the EPA decides how to implement the rule over the course of this year, it will find a route that both protects public health from human-made sources like smokestacks and tailpipes and encourages proactive wildfire protection.

“The key decision is going to be what happens in the U.S. EPA, PM 2.5 rulemaking. It’s really going to set the course for what is allowed or not allowed on the part of air districts over the next five to 10 years,” said Stanford’s Wara. He hopes for a path that can support both priorities.


“But if we just act as if it’s the year 2000 or sometime in the 1990s or even 1970 and the U.S. Forest Service reigned supreme over wildfire in the West?” he said. “We are not going to get this outcome.”

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