Why those in L.A. whose homes were spared in wildfires could still face serious health risks

When Kate Gammon and her family fled their Santa Monica, Calif., home during the recent wildfires, she wasn't sure what they would find when they returned. 

Though they weren't under an evacuation order, Gammon, who has asthma, told CBC News that the air quality was quickly worsening and the fires were volatile, so they left on Jan. 8, when the fires were about six kilometres away. Four days later, she returned to find that the house had been spared from the flames, but was alarmed to see a layer of ash dotting everything in her yard.

"It's just raining down on us at night," she said. "They're sort of like big, white, chunky pieces of ash."

Researchers now say that because of the massive scale of these wildfires and the types of structures that are burning, people returning home when the initial fire hazard is over can still face health concerns from airborne compounds in the ash and smoke. 

Firefighters in the state are still working to put out the two largest fires in Altadena and Pacific Palisades, which have killed at least 27 people and destroyed more than 12,000 structures including homes, schools and banks. On Thursday, the Los Angeles County Health Officer prohibited any cleanup or removal of fire debris until hazardous materials inspections are completed.

Ash and dirt in debris from residential and structural fires may contain asbestos, heavy metals and other hazardous substances, the health officer said, noting that people can be exposed to the toxic substances by inhaling ash or particles of fire dust, or through contact with the skin or contaminated drinking water supplies. 

As an environmental journalist, Gammon has previously reported on the health hazards posed by ash, not only from brush, but also from thousands of charred structures. That's why she says she avoids touching the ash and wears a mask outdoors.

Earlier this week, scientists published their findings about how wildfires that burn both wildland and urban areas can impact indoor air. They studied the 2021 Marshall Fire in Boulder, Colo., where about 1,000 structures burned in eight hours, which could help shed light on urban fires like those in L.A. 

Post fire headaches, itchy eyes 

Colleen Reid, a professor at the University of Colorado, studied the health effects among people who returned to unburned homes after that fire. She and her colleagues surveyed residents living near burned structures.

Over about five weeks, they also measured levels of volatile organic compounds (VOCs) at one home that survived the fires, but was heavily impacted by the smoke.

They found higher-than-normal levels of VOCs persisted for nearly a month inside the home before returning to typical indoor levels. 

"People who said that their home smelled differently after the fire were more likely six months after the fire to have headache, dry cough, itchy, watery eyes, strange taste in their mouth and sneezing," said Reid, an environmental epidemiologist. 

WATCH | Wildfire ash, smoke stick around in unburned homes:

Harmful toxins from wildfires linger in surviving homes

2 days ago

Duration 2:09

As evacuees in Los Angeles start to consider returning home, research suggests the toxic aftereffects of urban wildfires can linger for months in structures that survive the flames.

Reid and her team also surveyed people six months after the fire (642 respondents) and again a year later (413 respondents). The results included:

• 61 per cent of respondents reported campfire- or chemical-like smells in their homes one week after the fire, but they said those smells dissipated over time.

• 65 per cent of respondents reported ash in their homes after the fire.

• Most respondents were less confident about air quality both in their home and neighbourhood six months after the fire. Most regained confidence by one year.

Cleaning tips after wildfires

Delphine Farmer, a Canadian scientist with Colorado State University, studies indoor air as part of an experiment at the U.S. National Institute of Standards and Technology in Gaithersburg, Md., where she and her team analyzed the composition of particles inside a home-turned-laboratory after they introduced wildfire smoke.

Farmer found that smoke buries itself into painted surfaces, then slowly starts to come back into the air, which means residents are exposed to indoor pollutants for a long time after a fire.

To provide a guide for people who need to clean after a fire, the scientists are also studying how different air cleaners work and how surface cleaning impacts air quality. 

Based on her findings, Farmer's cleaning recommendations include: 

• Opening windows as soon as smoke pollution clears. The sooner you clean out smoke, the better.
• Wash fabrics like bedsheets, clothing and curtains that may have retained smoke. 
• Vacuum floors. Wear an N95 mask while doing this as it can stir up soot or smoke debris.
• Mop floors with soap and water and wipe down every surface you reasonably can, including walls if your region got a lot of smoke. Wash ceiling fans and other infrequently-cleaned surfaces. Change the water as it gets dirty.
• Clean the 'hidden spaces' of your home like attics, basements, closets and garages. 
• If your HVAC system was running, consider getting it professionally cleaned. Change the filters on your home HVAC system or air purifiers and run the fans constantly.
• Vacuum and wash furniture as soon as possible. If you still smell smoke, consider deep cleaning or replace.