Helping Families by Monitoring Soil Safety after the LA Fires

The Challenge

With raging wildfires across the Los Angeles area finally contained, millions of residents are now concerned about whether the air and soil are safe for their children and families. Specifically, residents have new fears of what contaminants (such as harmful metals) may have been released into the environment from incinerated homes, vehicles, equipment, and personal belongings.

Air quality has returned to pre-fire conditions, but pollutants may still linger in our soils, buildings, and streets.

Local, state, and federal authorities are working tirelessly to remove fire debris and make residents’ homes and schools safe again. And USC researchers have jumped in to apply their expertise to this emerging challenge. To provide greater context on potential exposure and impacts, researchers in USC Dornsife’s Department of Earth Sciences and USC Keck School of Medicine are working with Public Exchange to quickly evaluate and communicate the levels of lead contamination in soils and playgrounds in fire-impacted areas.

This testing is meant to augment ongoing State and Federal efforts, to more quickly provide Los Angeles residents with general updates on safety and the potential for exposure. It’s important to note that USC’s testing is not as comprehensive as the testing conducted by government agencies or environmental remediation experts, nor is it meant to be used for regulatory compliance with State and Federal requirements for remediation.

The Research

This project is evolving; new research will be conducted through Spring 2025.

In January 2025, after the fires were contained and before major rains had fallen, researchers and students gathered samples of roadside dust, playground sand, and stormwater runoff in and around the Eaton Fire burn area. A team of experts, Dr. Seth John, Dr. Josh West, and Dr. Sam Silva, conducted a preliminary analysis to measure the samples for lead levels.

Explore Interactive Map

The results were reassuring regarding the potential for lead exposure: Areas in the burned areas had the highest lead levels, with lead concentrations decreasing farther away. Within the Eaton Fire burn area, in the middle of neighborhoods where many structures burned, lead levels in roadside dust exceeded the EPA regional screening level (200 parts per million, ppm) for residential soils.

Lead levels were low in playground sand across all samples. Therefore, the research team can infer that lead is likely not a dominant contaminant of concern in playground sandboxes. Even locations that were heavily covered in ash but outside the burn zone had relatively low lead levels below the EPA soil lead threshold.

The animation above represents the movement of smoke across the Los Angeles area between January 7 and January 24, 2025, with dark red patches representing extremely smoky conditions (“heavy” smoke) and yellow representing less smoky air (“light” smoke). This is an estimate of the smoke’s behavior—the boundaries between orange and red, for example, should not be interpreted too precisely. The team expects that areas that were covered in red and orange plumes, particularly over consecutive days, may have greater overall exposure to pollution from the fires.

The researchers behind this analysis are Los Angeles residents and parents, and they find these results reassuring, particularly for areas outside of the burn zone. These findings can inform what actions and precautions other residents might feel comfortable taking—like sending children back to school.

Frequently Asked Questions

How should parents protect their children from potential contaminants in the soils, air, and water?

The key is to be educated about what contaminants of concern are in your community and how you can reduce your and your family’s exposure. Our data indicate that in this case, it’s a good idea to avoid taking your children to any burned structures, avoid drinking or playing in stormwater runoff in street gutters (which we should already do anyway!), and generally stay inside when the air quality is bad, using an air filter if available. The easy way to check the air quality is to use the EPA AirNow website, which has current, detailed information. Be sure to follow any guidance about your drinking water from your local water district. For more information about lead specifically, including how it can impact health and how to protect yourself see the Agency for Toxic Substances and Disease Registry’s (ATSDR) ToxFAQs on lead (also available in Spanish). For example, to reduce your family’s exposure you might wash your and your children’s hands and children’s faces often to remove dust and soil. You should also regularly clean your home (e.g., wet mop and damp dust) to remove dust and lead tracked in soil, use doormats at exterior doors, and consider leaving shoes by the door and not wearing them inside your home.

How reliable are the EPA safety thresholds for lead in residential soils?

No amount of lead is safe for a human body. Lead is a toxic substance, but there is likely some tiny amount of lead in places all around us. The EPA set a very low safety threshold for lead levels—200 parts per million (ppm). Up until 2024, the level for soil in which children play was set at 400 ppm, and nearly all of the samples in Altadena (even after the fires) would have been below that threshold and considered safe with regards to lead. Further, even the elevated levels in and around Altadena are similar to many soils in urban areas, including those around USC.

Do these results tell us anything about the threat of lead in soil to pets in and around Altadena and the Palisades?

These results indicate that the current lead concentrations in soils are elevated relative to what they usually are in these areas. Still, they’re no higher than the levels found at USC before the fires occurred. Moreover, the EPA sets its thresholds very low. While we can’t say there is zero risk to your pets, the risk is very low after the area has been remediated.

Does this mean the soil in Altadena is safe?

We can’t make a definitive statement on overall safety at this time. This data does not necessarily tell us that Altadena’s soils are completely safe today, but it does indicate the area can be made safe very soon. As part of those cleanup efforts, federal disaster cleanup crews–typically from the US Army Corps of Engineers–will scrape off the top 6 inches of the burned area in Altadena.

On the map, lead seems to be concentrated in the southwest corner of Altadena. Why is that?

We are still in the process of sorting out why the locations all have different lead concentrations. It may have something to do with how street dust moves across a community, a nearby lead source (e.g., a large old building that burned down), or something else. We intend to do more data collection and processing soon, providing more context and allowing us to understand better how these lead concentrations vary.

How does rainfall affect soil contamination?

Lead in dust appears to be washing away to some extent with the rain, though stormwater levels were below EPA “action levels” (which is 15 parts per billion). So far, preliminary testing of stormwater runoff—which was collected right in the burn area—indicates that, while there is evidence of enhanced lead in the water, the levels are not elevated beyond what is often observed in a large city like Los Angeles.

Did you test for asbestos or volatile organic compounds (VOCs)?

We haven’t tested for these; we’ve only tested for lead because it is easy and fast to test and generally a good way of assessing overall toxicity. We’re hoping to add people and resources to our team that can test for asbestos and harmful organic compounds. The researchers in this project are also parents living in the Los Angeles area, and after seeing the results of this lead testing, they have felt safer.

Will this amount of lead affect food grown in home gardens?

No, we do not expect that the amount of lead recorded in this analysis will impact fruits and vegetables grown at home outside of the areas in the footprint of burned structures. Make sure to wash your backyard fruits and vegetables (as you would ordinarily) before eating them.

As remediation begins, should we be worried about contaminated soils being blown into the air and deposited elsewhere in the region?

There are very strict guidelines governing debris removal after a fire, including hosing the soils down with water so that they are less likely to get into the air, transporting them with a cover such that they’re not open to the wind, and capping the location with fresh, non-contaminated soils.