As crews race to remove hazardous household debris from the burn zones of the Eaton and Palisades fires, federal environmental officials are seeking to reassure a fire-weary public over the quality of the region’s air amid lingering concerns over toxic elements not measured on a regular basis.

While Southern Californians are well acquainted with smog, some are concerned by a different kind of air pollution, air toxics, being generated by the recent wildfires that burned thousands of structures, releasing into the air and into the ash lead from painted surfaces, chlorine from pool chemicals and asbestos from older buildings and homes.

These toxic pollutants, often linked to cancer and other health problems, are not measured on a regular basis, raising concerns about whether local air is safe as crews work to clean up the burn zones.

Another concern is that the cleanup of thousands of properties is stirring toxic ash into the air. In the first phase of the cleanup of the rubble, Environmental Protection Agency teams have been fanning out across both blaze footprints, collecting old car batteries, paint and other hazardous items, and then removing them to designated collection sites.

In the second phase, the U.S. Army Corps of Engineers will remove all ash and debris and truck it to a landfill so that property owners can rebuild on cleared land.

Officials said crews are taking precautions to make sure the surrounding air is safe, even as others are urging vigilance and signaling some hope that tests that measure for more toxics could become the norm.

“We all know how toxic this stuff is that comes from urban fires,” said Joe Lyou, president and CEO of the Coalition for Clean Air, a nonprofit air quality watchdog group based in Los Angeles. “We know there are things to be concerned about. We need to take precautions.”

Air quality agencies say they are doing just that.

A mobile air testing device has tested the air in the Eaton fire area, collecting data on air toxics, said Jason Low, who heads the South Coast Air Quality Management District’s monitoring and analysis division.

“We drive through the communities with the burn scars to see what the level of pollutants are,” he explained.

The measurements were taken Jan. 31, 24 days after the Eaton fire broke out and during the removal of hazardous waste from properties, known as Phase 1 of the cleanup.

In about a month, the AQMD will have run four real-time mobile testing surveys, two in the Palisades fire zone and two in the Eaton fire zone, said Nahal Mogharabi, AQMD director of communications.

Results of the first mobile surveys in Altadena and Pasadena “near cleanup and re-populated zones” showed no elevated levels of air toxics, the AQMD reported Friday on its website.

The AQMD tests in the Eaton fire footprint back up the EPA’s claim that workers removing household hazardous waste are not putting particles into the air.

“We are doing work by hand,” said Rusty Harris-Bishop, a section leader with the EPA overseeing hazardous waste removal from the fires. “Our crews go in using at the most shovels, or sometimes rakes. They are removing debris to get to materials such as containers and batteries. We don’t typically stir up dust.”

He said the hazardous waste removal process involved 101 teams of about 1,200 workers on Thursday.

“It’s low-impact work and doesn’t do much to disturb the ash,” he added.

The just-released AQMD results will spot the locations of potential hot spots for air toxics and help determine where fixed testing sites will be placed. They will also be situated near sensitive areas, such as schools, Low said.

“We are looking at where the debris removal is and also the sensitive receptors like schools,” he said.

Jane Williams, executive director of California Communities Against Toxics, believes air testing in and around the burn areas should be ramped up during both Phase 1, the hazardous waste removal, and also during Phase 2.

As it is now, workers first spray debris with water to keep any dust and particles from becoming airborne, Harris-Bishop said.

The fire ash and debris are placed in a dump truck inside a heavy-duty plastic liner, according to the L.A. County Recovers website.

“This liner is tightly wrapped around the ash, and a tarp is then lowered over the truck to ensure the ash remains contained during transit,” the county explained.

Each worker has their own air quality monitors. Their monitors also keep track of air quality upwind and downwind, according to the Army Corps of Engineers.

Williams’ concern stems from past work on disasters. She has overseen cleanup of the 9/11 terrorist attack on the twin towers in New York City, and said more people died from inhaling dust and asbestos particles than from the initial collapse of the buildings that were struck by two hijacked commercial aircraft, which killed 2,996 people.

She wants the EPA to test the air in and around the Eaton and Palisades fires for silica and asbestos, as well as lead, which can interfere with development in children, and dioxin, an extremely toxic carcinogen produced by incomplete combustion. Indeed, The Mesothelioma Center said in a recent statement that fires such as those in L.A. County can release asbestos fibers. With prolonged exposure, the fibers can cause mesothelioma, a deadly lung disease.

“In Altadena they had a lithium battery storage facility that burned to the ground. You burned car dealerships, dry cleaners, battery storage facilities, part of industrial facilities,” Williams said. “We do not monitor the air for the things we should be.

“In post-urban fires, the exposure is ongoing until the ash is removed,” she said.

Williams is particularly concerned about ash and debris being removed from the burn zones, because this can kick up particles into the air and, if there’s wind, they can be blown into nonburn areas. When politicians take photos while walking in burn areas and not wearing masks, they send the wrong message, she said.

Dr. Muntu Davis, the Los Angeles County health officer, issued an order warning that any ash and debris from the fires poses “a substantial present or potential hazard to human health” if it is not properly stored, transported and disposed of.

While the AQMD has stepped up air toxics testing, during the first few days of the fires the wind-blown air had high levels of lead and other metals, as first discovered by an independent team of scientists.

Their work is fueling hope for more routine testing that captures more toxics, more often.

New data from Caltech, Jet Propulsion Laboratory and UC Riverside scientists shook up the regulatory world this month. They analyzed hourly levels of air pollutants from one site in Pico Rivera and another in Rubidoux starting on Jan. 7, the night of the Eaton fire, which burned 14,021 acres and destroyed 9,413 structures in Pasadena and Altadena.

From the evening of Jan. 7 through Jan. 11, Caltech and JPL scientists found elevated levels of air toxics using this new kind of real-time air monitoring system. Lead levels on Jan. 9 on average were 100 times higher than the typical range, while chlorine was 40 times higher at the peak and average black carbon levels were eight times higher than prefire concentrations, said Haroula Baliaka, a graduate student in environmental science and engineering at Caltech who analyzed the data.

Likewise, UC Riverside atmospheric scientist Roya Bahreini monitored real-time levels of these air toxics from Rubidoux, where the levels were not substantially higher than average because the wind was blowing southwesterly and didn’t bring the smoke to the Inland Empire site.

Both groups used the Atmospheric Science and Chemistry Measurement Network, known as ASCENT, funded by the National Science Foundation.

Bahreini called the system, which has only been in operation for about a year, a major air quality monitoring advancement. She said ASCENT gives other scientists in her field a better understanding of how urban fires change the air environment and impact public health, with at least hourly data 24/7.

Without ASCENT, data measuring air toxics would be delayed. Bahreini described the AQMD system, which uses air filters to collect particles. These samples are sent to labs and data is available every three days.

“If there are events in between you miss them,” she said. “If you are trying to see the effects of different emission sources on aerosol composition, you are blind to that.”

The AQMD’s Air Quality Index, which grades the air via numbers with colors and descriptions ranging from good to unhealthy, accounts for smog components such as ozone; PM2.5, particles 2.3 microns or smaller; carbon monoxide; nitrogen dioxide; and sulfur dioxide. But it does not account for toxic chemicals or metals that the Caltech and JPL researchers found in real time during the few days after the fires started, said Sina Hasheminassab, a JPL science system engineer who specializes in air pollution monitoring.

UCLA’s Institute of the Environment & Sustainability on Jan. 17 said air quality sensors, including the Air Quality Index, do not measure all the harmful things in the atmosphere. The index does measure PM2.5, particles that can reach the lungs and cause disease, but doesn’t break them down into components.

“We do not regularly measure asbestos, lead, other heavy metals, polyaromatic hydrocarbons, formaldehyde, etc.,” the institute stated.

But the institute said those not in a burn area or “burn-adjacent area” can trust the index.

The AQMD said it has 45 air toxic monitoring sites, some of which measure for lead. But these are within communities of concern, such as those near refineries, and are not specific to urban wildfires.

“Yes, we collect samples and do a gold standard analysis. It does take some time,” said Low, with the AQMD.

One exception is an AQMD site in Huntington Park that does provide real-time data on air toxics and metals, usually every hour, he said.

In comparison, he called the ASCENT system sites that provide information in real time as “helpful.” His colleague, Scott Epstein, an air quality assessment manager, said the AQMD’s filter samples also are very useful.

“Those samples have clear advantages for looking at long-term health impacts,” he said. “However, it takes time to get the data.”

The AQMD’s measurement of PM2.5 can tip them off to heavy metals or other chemicals from incomplete combustion, Epstein said. Sometimes when the particle concentration is heavier, it signals that researchers should dig deeper into the data to look for metals or lead.