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This is Science Friday.

I'm Flora Lickman.

Today on the podcast, the fires in Los Angeles are fully contained, but now residents

are dealing with a different problem.

The toxic chemicals left behind.

It's definitely an open question in terms of how much cleanup, how deep of a cleanup,

how often should you keep cleaning up until you can feel safe again in your home.

As the dust literally settles, people in L.A. are left with questions, like, what is in that

ash coating my backyard? What's in the air and how do I stay safe? Today, we've got two experts

in public health and toxic substance exposure on the line to talk about the chemicals left behind after an urban fire,

how much is known, and what science really needs to be done in order to understand this problem.

Let me introduce my guests. Dr. Rima Haber, Associate Professor of Environmental Health and Spatial

Sciences at the University of Southern California in L.A. And Dr. Mark Wilson,

Director of Exposure Science at the Chemical Insights Research Institute in Marietta, Georgia.

Welcome to Science Friday. Thanks so much for having us. Hi. Thank you for having me.

Rima, give me a sense of what's happening in L.A. right now. Where are we with the cleanup process?

We are now at the point where people are starting to go back to their homes. Some of them have been

cleared through what we call phase one. Others are still waiting. But the cleanup hasn't really

kind of finished yet. I would say it's not even maybe halfway.

It's massive and like the scale is unprecedented. So there's so many questions people are having right now.

I mean, is it safe for people to go back to burned structures?

...