Many are finding, despite all the elbow grease and thousands they're paying for professional cleaners, lead is a very stubborn toxin.
Before the New Year, Eaton Fire Survivors United released what is a truly terrifying statistic: 45 out of 50 homes that were remediated still tested positive for lead.
One year on, some are still struggling to get the lead out of their soil and out of their homes.
"I was just more concerned about myself and my neighbors," Altadena homeowner Blossom Wright told 7 On Your Side Investigates as she began to cry.
The tears haven't stopped for Wright, even a year later after the Eaton Fire.
As you walk her property with her, you'll learn what's fueling Wright's feelings now is frustration.
"It's been like having to become a citizen scientist," said Wright. "It's ridiculous."
Wright's bungalow craftsman is still completely sealed off.
Professional remediators have scrubbed and vacuumed the inside not once, twice or even three times, but four times.
And still, a dining room windowsill has failed a fourth test because of a high lead reading.
"Those are just tiny particles that are so stubborn," Wright told ABC7.
Ellen Dinerman's insurance won't cover the cost to remediate her soil, even though in one patch of her front yard, testing showed 1,200 parts per million, or PPM, of lead. The EPA threshold for potential lead contamination is just 300 PPM.
So to "detox" her soil, Dinerman has planted her front yard with specific grasses and sunflowers known to suck up heavy metals.
"I've pulled them all out because you don't want the birds to eat the seeds or they're getting the toxins," said Dinerman as she showed Eyewitness News the sunflowers she has planted.
Caltech geochemist Francois Tissot knows firsthand how lead from last year's smoke plume lurched in every pour it could.
Nearly everything he owns inside his Altadena home is now piled up.
It's all been flagged by remediators to be thrown out.
"It's pretty emotional to be here," Tissot said outside his home.
When Tissot isn't fighting his insurance company for coverage he's collecting samples from homes in and around the burn scar with students.
Early last year, they found high lead levels in more than half the samples they took.
Now they have started the process of retesting those homes to see how effective remediation has been.
Tissot and the students are swiping up dust from behind picture frames and up in attics looking for lingering lead.
And they expect to find some.
Last year, during their first testing round, 10% of cleaned windowsills they sampled still had lead levels above the EPA limit.
"So it is not a given that remediation will work," Tissot said to 7 On Your Side Investigates.
"And we have many stories of people that have cleaned their house once, twice, three times with professional companies and they're still testing above," Tissot said.
Tissot and his team of students will do the bulk of their retesting later this month.
Of course, we'll stay in touch with them and let you know what they find out.