LOS ANGELES — Tens of thousands of people in southeast Los Angeles County have been engulfed in a dense cloud of smoke for nearly a week as a fire continues to tear through a massive refrigerated warehouse in Boyle Heights. Toxic air has covered the San Gabriel Valley and beyond at times, as the fire continues to burn and the wind shifts the pall in different directions.

People have reason to be concerned about their loved ones breathing in the plume, experts say.

“There’s no safe level of exposure to particle pollution,” said Will Barrett, assistant vice president for nationwide clean air policy at the American Lung Assn.

Soot can be deadly. The charred microscopic particles can travel deep into a person’s lungs and bloodstream, causing swelling and triggering heart attacks and strokes.

People aren’t just being exposed for hours. They’ve been exposed for days in Boyle Heights, unincorporated East Los Angeles, Maywood, Montebello and Bell, according to the South Coast Air Quality Management District.

“There are some pollutants where just breathing in a little bit of it can cause some serious issues for people,” said Dr. Afif El-Hasan, a pediatrician with Kaiser Permanente. He said he’s most concerned about particles, carbon monoxide, volatile organic compounds and chemical gases from incinerated insulation, plastics and paint in the smoke.

“Those chemicals can cause irritation in the lungs, they can cause long-term lung damage, and sometimes they can even cause cancer,” he said. “I also worry about children, because children breathe in more air per volume of their body than adults do and they tend to be more active.”

“People also need to remember that even if you are healthy, these chemicals are going to put you at risk. It’s not just people who are vulnerable, anyone is in danger.”

The fact that the smoke continues to billow into the sky for a sixth day matters, said Jill Johnston, associate professor of environmental and occupational health at UC Irvine. “The longer the exposure time, the more dose you’re getting, or the more potential chemicals that you’re inhaling. So you’re gonna be increasing a potential risk,” she said.

Pregnant women and their babies in utero are known to be vulnerable to smoke from wildfires, she said. But less is known about city fires. “We see increased risk of low birth weight and preterm birth connected to exposure to wildfire smoke. This isn’t exactly the same composition of smoke, but would anticipate ... there could be potentially similar risk.”

A fire like this can leave people with no good choices. They can stay home with an air filter if they have one. But homes need “fresh” air, and a fire can make getting that impossible.

For that reason, some people believe that the official response to the gravity of the fire at Lineage Logistics has been inadequate. Jane Williams, executive director of California Communities Against Toxics, is among several activists who criticized the Los Angeles Fire Department and city officials who appeared to downplay health risks from prolonged smoke, and ultimately decided against evacuating these areas. They think many more people should have been evacuated.

“They always under-warn, they under-evacuate, they bring people back too fast,” Williams said. “I get that there’s a societal desire to return to normalcy.”

Local officials have opened a pair of shelters to house residents who want to temporarily relocate. The Los Angeles Unified School District also canceled summer programming for schools in the smoke-affected communities.

But “there is nothing in the air that is so dangerous that we have to do evacuations or even shelter in place,” LAFD Chief Jaime Moore said. Asked at a recent news conference whether the air was dangerous, Mayor Karen Bass said, “not to the extent that required a mandatory evacuation.”

Yet Williams pointed to the burning chemical-laden insulation foam inside the building, which could release several other highly toxic gases, including hydrogen cyanide, an asphyxiating gas, and isocyanates, chemical vapors that can cause serious lung damage.

“It’s about what you value and who you value,” Williams said. “If you value truth, you cannot sit there in front of a burning building and say the air is safe.”

A Fire Department spokesperson declined to comment when asked why the department considered a shelter-in-place order more appropriate than issuing an evacuation. It’s not clear that evacuation would have been purely a city responsibility. Lineage Logistics sits along the city boundary, with unincorporated Los Angeles County and other cities nearby.

mark! Lopez, a community organizer with East Yard Communities for Environmental Justice, also said the recently lifted shelter-in-place orders were not enough to protect residents from the heavy smoke and potential chemical releases. Residents, he said, have complained about smoke seeping into homes through cracks in doorways and windows, giving them sore throats and breathing problems.

Lopez said many of the smoke-affected communities have long suffered from poor air quality from decades of heavy polluting industrial facilities, highway traffic and rail yards. He said the public statements from Fire Department and elected officials that cast doubt on the risks from smoke were unacceptable.

“This is what happens when the Fire Department says there’s not a threat to human health. ... The LAFD, they aren’t public health experts.”

—Times staff writer David Zahniser contributed to this report.

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