The L.A. wildfires left lead and other toxins in the soil of burn zones. Here are their health risks

The Eaton and Palisades fires released mountains of hazardous material as flames chewed through old homes layered with lead paint and asbestos, kitchen cabinets filled with cleaning solutions, and cars, microwaves and other electronic devices filled with heavy metals.

In the wake of the fires, federal officials broke from the decades-long tradition of testing soil in wildfire burn areas in California to determine whether and when it is safe for people to come home. But testing conducted by the Los Angeles Times revealed levels of arsenic, lead and mercury that exceeded safety standards on a number of residential properties in the burn zone — including parcels that have already been marked as clean by federal officials with the U.S. Army Corps of Engineers.

Reporters from The Times fanned out across Altadena and Pacific Palisades to obtain soil samples from 20 properties cleared by the Army Corps, as well as 20 homes that survived the fires. The samples were carefully collected, stored and transported to BSK Associates, a state-certified laboratory in Fresno, to be tested for 17 toxic metals.

The state uses health-based cleanup goals to identify hazardous concentrations for each of those metals (measured in milligrams of contaminant per kilogram of soil) that recovery workers must remediate. The numbers come from the state and federal environmental protection agencies and are based on the risk of exposure — or how likely a soil contaminant is to enter your body through the skin, inhalation or ingestion — and the risk of negative health effects from that exposure.

Here’s what we were looking for, listed in alphabetical order — and why they could be cause for concern.

Antimony

Antimony (Sb) is used for hardening lead in batteries, as a flame retardant, and in the production of some semiconductors. Short term, inhaling antimony can cause eye irritation or a skin rash known as antimony spots. Long-term exposure can result in lung inflammation, chronic bronchitis and chronic emphysema.

Cleanup goals for soil are 31 mg/kg.

Arsenic

Arsenic (As) is a common element found in soil, water and air. It is also found in some paints, pesticides and batteries, and was once prominently used in treated wood for outdoor structures such as decks, sheds and picnic tables, though that application is no longer recommended. It is a known carcinogen. Ingesting high levels of arsenic can be fatal, while exposure to lower levels can cause nausea, vomiting, decreased production of red and white blood cells, abnormal heart rhythm, damage to blood vessels and other serious health issues. Skin contact with arsenic can cause redness and swelling. Arsenic has been known to bind with wildfire ash and soot.

Cleanup goals for soil vary based on the naturally occurring levels of arsenic. They typically range from 2 to 11 mg/kg. No official goals for the Palisades or Eaton fires have been set.

Barium

Barium (Ba) is commonly used as a contrast agent in X-ray procedures and is also used as a pigment in fireworks, among other applications. The Environmental Protection Agency does not consider it a carcinogen; however, exposure to barium can cause gastrointestinal irritation, cardiovascular effects, kidney damage and respiratory problems.

Cleanup goals for soil are 15,000 mg/kg.

Beryllium

Beryllium (Be) occurs naturally in mineral rocks, coal and soil, and is used in aerospace components, sports equipment such as golf clubs and bicycle frames, X-ray equipment and some electronics. Acute exposure from inhalation can cause lung inflammation, and chronic inhalation can cause chest pain, cough, shortness of breath, or noncancerous lesions in the lungs that can lead to scarring. Though there haven’t been many studies on beryllium exposure, those that have been done suggest that it may raise the risk of lung cancer.

Cleanup goals for soil are 16 mg/kg.

Cadmium

Cadmium (Cd) is a byproduct of smelting other metals and can be found in cellphone batteries, paint pigments, metal coating and some plastics. Cadmium is also released through the burning of fossil fuels and the incineration of municipal waste. The effects of acute exposure include lung irritation, and chronic inhalation or oral exposure can lead to kidney disease. It is a probable human carcinogen, with some studies finding lung cancer in workers exposed to cadmium in the air.

Cleanup goals for soil are 7.1 mg/kg.

Chromium

Chromium (Cr) is typically found in two forms with drastically different health risks. Chromium 6, a known human carcinogen, is almost exclusively released by man-made activities. Most notably, chromium 6 is used as a durable, anti-corrosive coating — known as chrome — for a variety of automotive and aviation parts, as well as a protective coating to lumber products. Inhaling or ingesting trace amounts for a prolonged period has been linked to an increased risk of lung cancer. Chromium 3, or trivalent chromium, is naturally found in soil, and is usually far less toxic than chromium 6. However, studies show wildfires can transform naturally occurring chromium 3 into toxic chromium 6. Soil testing typically doesn’t distinguish between the two forms.

Cleanup goals for soil are 85,000 mg/kg.

Cobalt

Cobalt (Co) is naturally found throughout the environment. It is a common constituent in lithium-ion batteries and paint pigments. Acute exposure by inhalation can cause respiratory issues such as difficulty breathing, congestion, edema and lung hemorrhages, while oral ingestion can cause adverse effects in the blood and thyroid. Chronic long-term exposure can cause more severe respiratory issues, cardiac effects, immunological effects and congestion of the liver and kidneys, among other problems.

Cleanup goals for soil are 23 mg/kg.

Copper

Copper (Cu) is a soft metal used in electrical wiring, plumbing, building materials and jewelry. Copper is an essential nutrient for humans and is found in many foods in small amounts. However, short periods of excess exposure can cause gastrointestinal disturbance, while longer-term effects include liver and kidney damage, which is why the EPA monitors copper in drinking water. Inhaling copper can cause nose and throat irritation, metallic taste, dizziness and headaches.

Cleanup goals for soil are 3,100 mg/kg.

Lead

Lead is a heavy metal commonly found in car batteries, household electronics, ceramic pottery, plumbing fixtures and other applications. For many years, lead was also used in gasoline and household paint. When lead is released into the air, it can travel long distances before settling to the ground, where it typically sticks to soil particles. It can also move from soil into groundwater. If inhaled or ingested, lead can cause permanent brain damage in children as well as slowed development and behavioral issues. In adults, lead exposure has been linked to kidney issues, cardiovascular issues and reproductive problems. Pregnant women in particular should avoid lead, as exposure can harm a developing baby. There is no safe level of lead.

Cleanup goals for soil are 80 mg/kg.

Mercury

Mercury (Hg) is a heavy metal historically used in thermometers and medical devices. Although it is a metal, it acts as a liquid at room temperature. Mercury is a neurotoxin and can cause serious health issues such as tremors, insomnia, emotional changes, headaches, decreased mental function, kidney effects, respiratory failure and death, depending on the amount and form of exposure.

Cleanup goals for soil are 1 mg/kg.

Molybdenum

Molybdenum (Mo) is an essential dietary nutrient, but it can be harmful when inhaled or ingested in higher levels. It is often used in the production of cast iron and stainless steels as well as some paint pigments, biofuels and solar panels. Studies have shown that breathing high levels of molybdenum for a long time can cause lung problems.

Cleanup goals for soil are 390 mg/kg.

Nickel

Nickel (Ni) is a naturally occurring element found in water, soil and air. It is primarily used to make stainless steel and is often combined with other metals to form alloys used in medical devices, jewelry, coins, batteries and other applications. Prolonged exposure has been linked to respiratory effects, while animal studies have shown effects on the stomach, blood, liver, kidneys, immune system, reproduction and development. It is a believed carcinogen.

Cleanup goals for soil are 820 mg/kg.

Selenium

Selenium (Se) is a trace mineral needed in small amounts for good health. However, exposure to high levels can result in brittle hair, deformed nails and neurological effects. Inhalation of selenium vapors may also cause dizziness, fatigue, irritation of the mucous membranes and respiratory effects. Selenium can be found in products such as electronics, glass, plastics, pesticides, shampoos and rubber. Most forms of selenium are not considered carcinogenic; the EPA, however, has determined that one form, selenium sulfide, is a probable carcinogen.

Cleanup goals for soil are 390 mg/kg.

Silver

Silver (Ag) is often used to make jewelry, silverware and electronic equipment. Most people are exposed to low levels of silver each day in food, water and potentially the air. But exposure to dust containing high levels of silver compounds can cause respiratory issues, lung and throat irritation and stomach pain. Skin contact with silver compounds can also cause allergic reactions or turn some areas of the skin blue or gray.

Cleanup goals for soil are 390 mg/kg.

Thallium

Thallium (Tl) is a naturally occurring element used in superconductors, infrared optical materials, photoelectric cells and gamma radiation detection equipment, among other applications. Exposure can lead to gastrointestinal issues, neurological symptoms such as tremors, seizures and coma, dermatological symptoms and possibly even death. There are many recorded cases of fatal thallium poisoning.

Cleanup goals for soil are 5 mg/kg

Vanadium

Vanadium (V) occurs naturally in soil, air and water but can be released by industrial sources — primarily the combustion of fossil fuels in facilities such as oil refineries and power plants. Acute exposure can lead to respiratory issues, skin and eye irritation, and gastrointestinal problems such as nausea and vomiting. Longer-term exposure to high levels can result in lung damage. The EPA does not currently classify vanadium as a carcinogen, but other health groups have said it could cause lung cancer based on evidence from animal trials.

Cleanup goals for soil are 390 mg/kg

Zinc

Zinc (Zn) is one of the most common elements in the Earth’s crust and an essential micronutrient for the human body. It is also found in batteries, paints and pigments and metal alloys, and can be released from industrial activities such as coal burning, steel production and waste management. Inhaling large amounts of zinc or zinc dust can cause a short-term disease called metal-fume fever. Ingesting high levels of zinc can also lead to gastrointestinal issues or anemia and pancreatic damage, among other adverse outcomes.

Cleanup goals for soil are 23,000 mg/kg

What is a ‘cleanup goal’?

Both the U.S. EPA and California’s Department of Toxic Substances Control consider the risks of developing cancer and experiencing other adverse health effects from long-term exposure to metals when determining “safe levels” of the metals in residential soil.

But establishing cleanup goals isn’t always as simple as applying those health-based safety levels. That’s because some metals are naturally occurring and already present in an area as part of its geology. Some communities — such as those near a freeway — can also have elevated levels of these toxins long before the fire moved in.

Sometimes, the background levels of metals are higher than the health-based levels. This is virtually always the case for arsenic, which has a health-based level of 0.032 mg/kg, but often naturally occurs in California at levels ranging from 2 to 11 mg/kg.

When this happens, wildfire recovery experts sample unaffected areas to establish a “background level” that is used instead of a fixed cleanup goal.

Scientists and recovery experts do this for a few reasons: First, the scope of their work is strictly to remove contamination from the fire, not preexisting contamination or the natural background levels. Removing naturally occurring metal is an arduous to borderline-impossible task.

“The presence of arsenic in soils and related exposures to that arsenic is a part of living on Earth,” the Department of Toxic Substances Control said in a statement — noting that their 0.032 health level is not meant to represent an acceptable cleanup level. “It is important to recognize that while elevated levels may pose a risk under specific conditions, simply having a detection above a screening level does not indicate imminent risk.”

The toxicity of a metal like arsenic can vary greatly depending on the chemical compounds it exists in. Metals bound to large soil particles are less likely to move through the air and enter the lungs, and metals in certain natural compounds are less likely to do damage when inside the body. Generally — but not always — metals in wildfire ash, unlocked by the heat, are more likely to pose a risk.

Determining the background level — and therefore the cleanup level — for metals is not always simple. There often isn’t a history of samples taken before the fire to serve as a direct comparison, so scientists have to get creative and determine background levels by testing similar soil outside the burn zone, sampling deeper in the earth where fire contaminants haven’t reached yet and using sophisticated statistics calculations.

With no comprehensive testing efforts, scientists have not established arsenic background levels for the Eaton fire and Palisades fire burn areas. However, the 2024 Mountain fire, which burned in Ventura County atop a similar soil type as the Eaton fire, has a background arsenic level of around 4 mg/kg. The 2018 Woolsey fire, which burned on a similar soil as the Palisades, had a background level of around 9.3.

The Times found arsenic significantly above these levels at one standing home in the Palisades and two homes in Altadena — one standing and one that had been destroyed and for which the Army Corps had removed debris and the top layer of soil. There were also a number of properties among the 40 samples taken by Times journalists that showed levels of lead and mercury far above the cleanup goals. Read more about what we found here.

Health risks and other information contained in this glossary come from the Centers for Disease Control and Prevention, the U.S. Environmental Protection Agency, the Agency for Toxic Substances and Disease Registry, and the National Institutes of Health.