The Biden administration today set a new, more rigorous standard for a dangerous air pollutant that has plagued vast swaths of California for decades: Fine particles, commonly called soot.
The U.S. Environmental Protection Agency’s new annual soot standard could throw seven new California counties out of compliance, totaling 29 counties, according to EPA information released today based on 2020 through 2022 data.
San Diego and the rural counties of Mendocino, Mono, Shasta, Siskiyou, Tehama, and Colusa could be added to the long list of California counties already breathing unhealthy levels of soot.
And the Los Angeles basin and the San Joaquin Valley, which are blanketed with the nation’s worst smog and soot, now face an even tougher challenge after spending decades trying to clean the air.
California is so far off from achieving clean air that the local San Joaquin Valley Air District wrote to the EPA last year to warn: “There is no clear path forward on how the Valley or other regions of California can attain the proposed standard.”
Spewed by an array of sources — from fireplaces to diesel trucks — fine particles known as PM2.5 can lodge in lungs, aggravate respiratory disease and trigger heart attacks. Hospitalizations and deaths from heart and lung ailments surge when soot concentrations rise, research shows.
The new standard is extremely controversial — and widely expected to be challenged in court by industries and some states.
The EPA predicts that strengthening it will save 4,500 lives and eliminate 290,000 lost workdays nationwide in 2032.
The soot standard was last strengthened in 2012. Although the Clean Air Act requires an EPA evaluation every five years, President Donald Trump’s administration declined to tighten it despite mounting evidence of the threat to public health.
Under the new standard, annual average concentrations of fine particles cannot exceed 9 micrograms per cubic meter of air, down 25% from the current 12.
For years, the Visalia and Bakersfield areas have had the nation’s worst fine particle pollution, with average levels nearly twice as high as the new standard allows, based on the EPA's 2020 through 2022 data. Mono County, in the Eastern Sierra, also has soot levels more than double the new limit, according to that EPA data.
Although 29 counties have soot exceeding the new standard based on 2020-22 data, the EPA projects that it could drop to 23 counties by 2032.
Nationwide soot in 119 counties exceeds the new standard, based on the 2020-22 data. Of those, 59 already violated the old standard. By 2032, the EPA says it could drop to 52 counties in 16 states that violate the new limit.
Business groups say efforts to attain it will cause widespread economic problems and job losses. Brady Van Engelen, a lobbyist for the California Chamber of Commerce, said the more stringent standards could “effectively put all permitting into a gridlock” for new manufacturing activities and jobs.
Marty Durbin, senior vice president for policy for the U.S. Chamber of Commerce, said in an emailed statement that compliance is complicated by dust from roads and smoke from wildfires. He said the EPA should have kept the existing standard instead of “punishing counties and the private sector for situations largely out of their control.”
However, the Clean Air Act requires the EPA to set its standards based strictly on the latest scientific evidence — not what is achievable or economical.
Achieving the new target will take wide-ranging new state and local regulations aimed at cutting emissions. Fine particles are spewed into the air from the burning of diesel fuel, gasoline and wood, including trucks, farm vehicles, fireplaces and restaurant charbroilers, but also from manufacturing plants and dust stirred up by farming, construction and roads. (Emissions from wildfires are exempt from the EPA’s soot standards.)
Air pollution rules in California, particularly in the Los Angeles basin, are already the most stringent in the nation. So California officials say that they desperately need the help of the federal government, since states and local agencies cannot control some of the biggest remaining sources of soot — aircraft, trains and ships.
Remote, rural, mountain areas aren’t immune: The Sierra Nevada counties of Mono and Plumas have high levels of soot, largely because of wood burning.
“The science is clear: soot pollution is one of the most dangerous forms of air pollution and it's linked to a range of serious and potentially deadly illnesses, including asthma and heart attacks,” said EPA Administrator Michael S. Regan.
Dr. Doris Browne, a former president of the National Medical Association, which represents Black physicians, said the new standards are critical for addressing health disparities. Communities of color, along with older people and those with heart and lung conditions, are most in danger from “their close proximity to sources of this dangerous and deadly pollutant,” she said.
The next step? The EPA will spend up to two years determining which counties are out of compliance. The agency warned that its projections released today are not formal designations, and the counties could change.
Then, local and state officials will launch years of planning to decide which additional pollution-fighting measures to undertake. California’s local air quality districts must develop and approve elaborate plans detailing their promises to achieve emissions reductions.
The federal government can withhold highway dollars if a state fails to submit a plan, the plan is inadequate or the plans aren’t followed. But those situations are rare, and the EPA considers withholding funds an “extraordinary measure,” said Shayla Powell, an agency spokeswoman.
What is pm2.5 and why is it dangerous?
Fine particles of air pollution are 30 times smaller than a human hair, or 2.5 micrometers in diameter or less. Soot is sometimes hard to see, easy to inhale deep into the lungs and devastatingly common in California.
Fine particle pollution can be extremely harmful when inhaled. That’s because the human body’s defenses help keep larger, coarse particles from the deepest parts of lungs. But the fine particles can penetrate the air sacs of lungs and then pass into the bloodstream and travel to other organs, particularly the heart.
An EPA analysis concluded that “a substantial body of published scientific literature documents the association between PM2.5 concentrations and the risk of premature death.”
A range of adverse health impacts can result; increased risk of death from heart disease is one of the most well-documented. A 2019 study of Californians, for instance, linked fine particles to elevated risks of death from coronary artery disease, and a 2020 study found that long-term exposure was associated with deaths from heart disease and strokes.
Increased asthma attacks are another well-documented health impact. And in recent years, a growing body of research has shown it can harm the brain. A study by University of Southern California researchers published this year reported that exposure can alter brain development patterns in adolescents.
“It's a much larger, systemic story,” said Edward Avol, professor emeritus at the University of Southern California’s School of Medicine. “A sad part of the story is that it's not equal — we don't all get to breathe the same quality air.”
“People who live closer to freeways, who live close to refineries or power plants, who, by virtue of their economic status, live in more polluted areas are more exposed.”
What are the major sources in California?
While fine particle pollution is often referred to as soot, evoking an industrial Dickensian era, much of it comes from fumes from trucks, automobiles, power plants and other sources that mix in the air with other compounds.
While some fine particle pollution can come directly from a specific source, such as a diesel truck, construction site, fireplace or smokestack, most fine particle pollution (unrelated to wildfires) comes from these complex chemical reactions.
Sulfur dioxide is one compound that can mix with others to create particles. It’s emitted when coal, petroleum oil or diesel is burned. Nitrogen oxides are other common urban precursors that come largely from traffic or industrial plants. Ammonia, which can come from large-scale agricultural operations, among other sources, is another important precursor.
What will the San Joaquin Valley have to do?
California’s vast valley has a long way to go to make its air healthy, according to the San Joaquin Valley Air District, the agency responsible for regulating the region’s polluters.
In an interview with CalMatters, Samir Sheikh, the district’s executive director, said the region faces unique challenges given its geography. With the valley surrounded by mountains, pollution gets trapped.
Emissions from agriculture, energy production and goods transport are among the major sources. While some emissions are at an all-time low, according to the district, climate change worsens the problem.
“We do have a very unique situation here where it takes even more reduction — significantly more reduction — in our area than it does most of the rest of the country to achieve the same goals,” Sheikh said.
“We're surrounded by forests with wildfires, there's persistent droughts...There are challenges that are becoming even bigger over time.”
Reductions will need to come from cars, trucks, heavy equipment and other so-called “mobile” sources that the local air district doesn’t regulate — they are under the control of the state Air Resources Board.
California has already set the nation’s toughest emission standards for cars, trucks and other vehicles, and its recently enacted regulations for zero-emission cars will help the San Joaquin Valley and Los Angeles basin comply with the new soot standard.
Clean air advocates in the Central Valley deploy the morbid emergency room acronym D.O.A., dead on arrival, as shorthand for what they see as the main causes of pollution in the valley: development, oil and agriculture.
In the San Joaquin Valley, which is one of the poorest regions in the nation, inequality and health injustice go hand-in-hand.
“It's hard to put a price tag on not being able to let your kid go outside and play safely,” said Catherine Garoupa, executive director of the Central Valley Air Quality Coalition. “For better or worse, the San Joaquin Valley is the canary in the coal mine. We're the extreme example.”
In the Sacramento region, soot isn’t a new problem. But its air has met the EPA’s previous annual standards for soot. In an interview with CalMatters before the EPA’s announcement, Mark Loutzenhiser, a manager with the Sacramento Metropolitan Air Quality Management District, said his agency will be closely watching the process with the anticipation that they could be out of compliance.
What will the Los Angeles region have to do?
The Los Angeles region also faces severe challenges meeting the current standard. The South Coast Air Quality Management District is responsible for regulating air pollution in Los Angeles, Orange, San Bernardino, and Riverside counties, which has 17 million residents.
Based on the EPA’s analyses of air quality data from 2019 through 2021, The Los Angeles basin reached 14.2 per cubic meter of fine particulate matter in the air. It now has to get to 9 to meet the new one announced today.
Yet the South Coast hasn’t even approved a plan to meet the previous standard, set in 2012. It won’t do so until at least spring of 2024, said Bernard Parks, Jr., a spokesperson for the agency. That plan will now immediately be outdated.
Parks refused CalMatters' requests for an interview about how the region will cut emissions and would only answer questions by email.
The air district said it has already set dozens of local regulations and that it needs the federal government’s help to control sources that it can’t regulate, such as ships and aircraft.
Local regulations already in place have cut emissions from oil refineries and other industrial plants, as well as an array of sources in homes and businesses, such as paints, solvents, charbroilers and fireplaces.
The district is seeking more reductions by targeting industrial boilers, heaters, furnaces and other units as well as internal combustion engines and turbines. The district also offers an array of incentives aimed at reducing emissions from trucks, school buses and other mobile sources regulated by the state.
Violating the previous fine particle standard caused an annual toll of an estimated 1,500 premature deaths, 8,700 hospitalizations and 163,000 days absent from school and work, the air district said in a letter to the EPA.
What about wildfires? Aren’t they a major source?
Wildfire smoke is toxic and its proliferation this summer in many cities in other states helped underscore the reality of what a future with more extreme weather might look like. It is a considerable source of soot, and those particles are considered smoke’s most hazardous ingredient.
Smoke may be diminishing some of California’s clean-air gains, according to The New York Times. The Energy Policy Institute of Chicago released a report last year that showed some California counties were more polluted than they were in 1970. In 2020, more than half of California counties experienced their worst air pollution since 1998, according to the report.
But California’s air quality agencies do not have to consider wildfire smoke when planning how to attain the EPA’s new standard. Fires are considered “exceptional events” under the federal Clean Air Act. And the EPA allows jurisdictions to apply for waivers for wildfire events, although critics say that is a complex and protracted process.
Some experts say that the EPA’s exemptions for wildfires may have to be reconsidered as climate change triggers larger and more unpredictable wildfires — and more and more soot.
John Osborn D'Agostino, CalMatters’ data and interactives editor, contributed to the reporting on this article.