The Toxic Aftermath Of An Urban Fire

FLORA LICHTMAN: This is Science Friday. I’m Flora Lichtman. After nearly four weeks of burning, the fires in Los Angeles are almost fully contained, and cleanup is underway. But as the dust literally settles, people in LA 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 Habre, Associate Professor of Environmental Health and Spatial Sciences at the University of Southern California in LA, and Dr. Mark Wilson, Director of Exposure Science at the Chemical Insights Research Institute in Marietta, Georgia. Welcome to Science Friday.

RIMA HABRE: Thanks so much for having us.

MARK WILSON: Hi. Thank you for having me.

FLORA LICHTMAN: Rima, give me a sense of what’s happening in LA right now. Where are we with the cleanup process?

RIMA HABRE: 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 the scale is unprecedented. So there’s so many questions people are having right now.

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

RIMA HABRE: I think that’s what we’re all struggling to answer as accurately and in the most helpful way as possible. A burned structure obviously is very dangerous, and I’d love to hear Mark’s thoughts on that. But where we’re struggling the most is many people are going back to not-so-damaged structures but that have a lot of ash outside and around them and perhaps in them and got a lot of smoke damage.

And even when you clean that up, you have a lot of lingering questions around what’s possibly safe or not, even in the longer term.

MARK WILSON: Yeah, I agree that it is very difficult to understand just what safe means, given the vast differences in level of impact that are going to be experienced at different locations. And there are very significant unknowns associated with what chemical hazards, as well as physical hazards, exist within the residual materials and how those may be trafficked in the environment and how they may ultimately impact health.

FLORA LICHTMAN: Well, what are some of those unknowns, specifically?

MARK WILSON: The nature of the residues is heavily influenced by the fuels, the combustion fuels that were associated with the event. And those can vary widely from location to location, even residents to residents.

So things like age of properties can be important covariates associated with whether you are likely to see things like heavy metals from legacy building materials like lead and paint or lead service lines in water, versus newer residences, which may have things like solar panels and powerwalls and e-vehicles. So it’s very difficult to have a broad understanding of what types of hazards you anticipate being present.

RIMA HABRE: Yeah, absolutely. I think it’s exactly what Mark said. And also, let’s say, asbestos, which we know that might not travel too far, but it’s so hard to know given how complex the plumes were, how windy things have been. But also, we are worried about kind of what we call multimedia exposures now to people going back.

So let’s say some of the really open questions are exactly what Mark said, like, how much of that is remaining inside my home or right outside? Lead and asbestos are particularly concerning, especially if you have kids who like to play on the floor and get their hands in their mouth or track in the outdoor dust and dirt.

But also, even for the smoke itself, we know that a lot of these volatile compounds tend to glue themselves onto surfaces and will take a lot of time to start off gassing and stay in the air even after you clean up. I’m not saying that is maybe the most scary thing or concerning thing right now, but 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.

FLORA LICHTMAN: So you’re saying that even if you’ve cleaned up all the ash, there could be small volatile organic compounds that are stuck in your couch or that could sort of re-off gas. Is that right?

RIMA HABRE: 100%. 100%. And we’ve been talking about this a lot. And I worry that sometimes we’re making people panic about every little thing that could be there. I’m not saying those VOCs are maybe my biggest worry, relative to lead and asbestos and the things that Mark mentioned. Especially with these newer materials, we’re not sure exactly what’s in them.

But all of these are still open questions. And we’re trying hard, especially in our exposure science community, like Mark and I are specialized, to get people more actionable information and answers, like, how do you figure these things out?

FLORA LICHTMAN: Well, what kind of chemical monitoring is happening right now in Los Angeles?

RIMA HABRE: We’re trying to deploy a lot of air sensors and monitors. Right now, the air quality is much better, to be honest. But also, sometimes the ash gets kicked around. We’re trying to measure more of the chemical species within the particles and the gases and volatile organics in the air. But we’re also trying very hard to deploy into homes to measure what’s in the dust and the soil and especially ash impacts or remaining air contamination, water contamination.

The tricky part is these are very intensive, very complicated studies. And they need so many things to line up together to be able to do them. So we’re not fully out there yet, but we’re working very hard around the clock to try to do that.

FLORA LICHTMAN: Let’s talk about air quality a little bit because I know this is on people’s minds. I want to play a question from one of our LA listeners.

SANDEN TOTTEN: Hi. My name is Sanden Totten, and I live in Los Angeles, California. A lot of what I’m scared about and wondering about there’s these particles we’ve heard we can’t really measure, things like asbestos or benzene. And how much of that is in the air? Should I be wearing a mask when I go outside? And I’ve heard N95s don’t quite catch all the smaller particles. So should it be full-fledged gas masks, like a P100? It feels like that really is postapocalyptic.

I also have a young child. He’s four years old. And I don’t know, should I be keeping him indoors? When will we know it’s safe to let them run around and take big, healthy gulps of air again?

FLORA LICHTMAN: Mark, any thoughts?

MARK WILSON: I think it’s important to recognize that the caller brought up two distinct classes of hazards. They brought up benzene, which would be a volatile organic, which we were just talking about, and also asbestos. If you were going to use something like an N95 respirator, that might provide a good level of protection associated with something like particles or fibers, like asbestos.

But depending on the type of respirator, like in the absence of a VOC cartridge, it wouldn’t provide any protection at all for gases. So until we have a better understanding of the holistic picture of what the chemical hazard landscape looks like, both in the air and in soils and water and dusts, it’s going to be very difficult to make definitive statements associated with safety.

FLORA LICHTMAN: Mark, would you be wearing an N95 or a more heavy duty respirator if you were in LA right now?

MARK WILSON: If I was personally there, yes, I would wear respiratory protection. I would focus a lot on hygiene, so handwashing and things like that. I would certainly consider if I was going to interact with any kind of impacted area, that I would want to probably wear disposable gloves, close-toed shoes, long pants, long-sleeve shirt.

But we also have to acknowledge that the personal protective equipment has to be appropriate for the hazards. And when we don’t have a real clear picture of what those are, it’s difficult to identify exactly what level of protection is necessary.

FLORA LICHTMAN: Rima?

RIMA HABRE: Yeah, I definitely agree with that, Mark. I think I just want to make a couple of clarifications because we’re also getting a lot of these questions. So I think Sanden was our caller’s name. And basically, I’m in LA right now. I’m going around as normal, not wearing anything in general day-to-day life, not in impacted areas.

But there is a distinction. When the fires were burning, of course, we’re worried because all these things are being emitted very quickly and in large volumes. So I would wear protection if I’m going outside, or at least I would consider it if you’re in the general LA area and not very close to the burn or very adjacent to it or downwind of the smoke.

But right now, I think if you are going into impacted areas, like Mark said, or trying to clean up your house or you were very close to it or in the middle of it, that’s when I would wear protection for sure and exactly like Mark said. I do think another important thing that Sanden, our caller, mentioned is their child, who’s four years old.

And with children, we worry more, of course, because they’re in such a sensitive developmental stage of their life. And kind of the open questions we have now are, if they’re out playing in a sandbox or on the playground, and yes, there’s a little bit of lead that deposited at one of these events, perhaps ash and asbestos, how much cleanup should happen to make sure they are safe? The really important question is, how much deposited on these surfaces that the kids are playing in, especially when it comes to lead and ash and metals and asbestos?

So just keep in mind that lots of open questions. But still, as Mark said, if the air quality is good outside and you’re not right in the zone, you’re probably fine.

FLORA LICHTMAN: Did these air quality indices pick up on some of these other chemicals that Sanden and that we’ve mentioned? If you look at AQI, is it actually going to give you a picture of whether the air is safe?

RIMA HABRE: So here’s the thing. I think people are kind of doing unfair comparisons with the AQI because the AQI was designed as a communication tool. And it’s done so much public health good and benefit. The AQI can only use information that we measure regularly. And that’s particles and maybe NO2 and ozone, depending on what’s around. We don’t have measurements of VOCs and these toxics as regularly and as intensively as some of these other things.

That said, the AQI is still a very good indication of whether you should be worried, yes or no, and it should help you plan your life. But also, your nose can tell you a lot if you’re smelling smoke or seeing smoke and ash.

FLORA LICHTMAN: Rima, what long-term health effects are you concerned about?

RIMA HABRE: So there’s mental health effects, of course, and trauma from the entire disaster. But we worry about cancer effects because some of these toxics are more hazardous than your average particle. We worry about cardiovascular effects, longer-term respiratory effects. Ash is very irritating as it is, let alone now with all these urban fires, like Mark was explaining. We don’t know what kind of damage that could have caused.

So this is, again, not to alarm people, but when you look at an entire community that was exposed, over the long-term, across all these people, we definitely will be monitoring to see what the chronic health outcomes will be.

FLORA LICHTMAN: Mark, we’ve talked a lot about how there are so many unknowns right now. If we wanted to understand fires and chemical exposure on a scale like this, what is the ideal science experiment that you would do?

RIMA HABRE: That’s such a good question. Mark, I want to know.

MARK WILSON: In a world that is completely not impacted by resource limitations, not impacted by time, I would build a city. I would geotag everything within the city so I could account for point sources of various things like homes that contained lead, e-vehicles, internal combustion vehicles, et cetera, and then create a very large-scale fire in a mock city and see what happens.

FLORA LICHTMAN: You’d burn it down?

MARK WILSON: That’s not a practical approach.

FLORA LICHTMAN: Do you do this on a smaller scale in your lab?

MARK WILSON: We do try to recreate scenarios that are associated with various fire fuels. But one of the biggest challenges with lab-scale reconstructions is that it is literally a matter of scale. So things like temperature of combustion or combustion efficiencies are difficult to impossible to recreate at a small scale.

FLORA LICHTMAN: Mark, do you have any cleanup tips for people who are going back to their house and maybe there’s ash around or they’re near an affected site? What should they do?

MARK WILSON: One of the critical things that I would do myself would be using a as-highly-rated air filtration system as my HVAC system could deal with, so MERV 13 or better. And I would engage in cleaning practices that were not stirring things up. So mopping would be better than using a broom, for instance.

But the ultimate answer is that there isn’t a very clear criteria to establish how you clean all things all of the time.

FLORA LICHTMAN: When do you think we’ll start having some answers? And what should people be doing in the meantime?

RIMA HABRE: I think over the next few weeks, because a lot of people are mobilizing, and I’m so glad I met Mark through Science Friday because I will need your help, please, and expertise as well. And I’ll reach out. But I think over the next few weeks, you’ll start to see data coming out. I want to say in the meantime, though, there’s so much good, practical information out there on how to clean, how to be safe. Listen to people you trust. Don’t panic.

But if you’re in impacted areas, try to be safe about these things. If you’re in a general area that’s not as impacted, you can go about your day-to-day life and hopefully try to help as much as you can with anyone around you who needs help.

FLORA LICHTMAN: Thank you for joining me today.

RIMA HABRE: Thank you for having me.

MARK WILSON: Thank you for having me.

FLORA LICHTMAN: Dr. Rima Habre, an Associate Professor of Environmental Health and Spatial Sciences at the University of Southern California in LA, and Dr. Mark Wilson, Director of Exposure Science at the Chemical Insights Research Institute in Marietta, Georgia.

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