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Heavy Metals in Soil

Lead in Soil: Remediation Options and Where Biology Fits

Since microbes do not remove lead, this guide covers the documented options for lead in soil, EPA's current screening level, and where soil biology supports the plan.

Elm Dirt Science Team

Community garden in an urban neighborhood, illustrating city soils and the urban growing context.
Community garden in an urban neighborhood, illustrating city soils and the urban growing context.USDA · Public domain (US Gov)
On this page (8 sections)
  1. Where soil lead comes from
  2. Screening levels
  3. The options
  4. Where biology fits
  5. Bioavailability
  6. Before choosing any option
  7. Your site
  8. Sources

No microbe can destroy lead, because lead is an element [1]. The established options for lead in soil are physical or chemical: remove and replace the soil, cover it, grow food in raised beds of clean soil, dilute and bind the lead with compost and other amendments, stabilize it with phosphate, or have plants take it up [2][3][4]. Soil biology supports that work by building organic matter, cover and structure and by cutting bare ground and dust. Below are the options with their evidence, the current federal screening levels, and what to do before choosing.

We report what agencies and peer-reviewed studies say, and we won’t tell anyone a particular property is safe or unsafe. Exposure questions belong with your state or local health department. See also heavy metals in soil, the heavy metals profile and urban lead soils.

Where soil lead comes from

Lead-based paint is a well-documented source of soil lead. After the Eaton Fire, Los Angeles County said lead in soil near burned homes was reasonably expected to come from houses with lead-based paint, common before 1979, while noting many other lead sources in the area [5]. A review of urban agriculture calls lead the most common contaminant in urban areas [6]. Our post on wildfire ash and metals covers those test results.

Screening levels

EPA’s current approach for residential soil lead at Superfund and hazardous-waste cleanup sites comes from a directive issued October 16, 2025. It sets a regional screening level of 200 parts per million (ppm) for lead in residential soil and a regional removal management level of 600 ppm, using a target children’s blood lead level of 5 micrograms per deciliter to derive preliminary remediation goals. It supersedes EPA’s January 2024 guidance [7].

When reading any of these numbers:

  • A screening level is not a cleanup standard, and EPA says so directly about its RSLs [8].
  • Agencies set different levels: California’s DTSC residential screening level for lead is 80 mg/kg, which Los Angeles County used in its fire testing [5]. Hawaii’s residential action level is 200 mg/kg [9]. Since 1 mg/kg equals 1 ppm, the figures compare directly.
  • The rules change, and EPA replaced its 2024 guidance within two years, so check the current document and your state’s rule.

The options

Option What it does Evidence Where biology fits
Remove and replace soil Takes the lead off the property; clean soil goes back After soil removal in Los Angeles fire areas, county sampling showed a significant reduction in potential health risk where removal occurred [5]; a Duke study found scraping greatly reduced lead and arsenic [10] Rebuilding soil, structure and cover on the replacement soil
Raised beds of clean soil Puts growing roots in clean material EPA’s gardening guidance: use raised beds filled with clean soil, apply mulch, wash fruits and vegetables, peel root crops, cover bare soil [11] Compost and mulch feed the new bed
Dilute and bind with amendments Mixes in compost or biosolids and lime to dilute lead and reduce uptake Field plots in Tacoma and Seattle: amendments diluted soil lead 10% to 23% (biosolids mix with dolomite) and 20% to 50% (compost with dolomite), and cut lead in vegetables by 50% to 71% [3] Organic matter is the amendment
Phosphate stabilization Chemically converts lead to less soluble forms A review reports marked reductions in lead bioavailability in many tests, and calls it an emerging technology gaining regulatory acceptance [2] None directly; it is chemistry
Phytoextraction Plants take lead up and are harvested A fungus plus a hyperaccumulating plant removed 58.6% of lead in a soil study, against 40.2% for the plant alone [4] Microbes can raise uptake; slow, and the harvest needs disposal

Notes on the table:

  • Dilution leaves the lead in place: in the Tacoma and Seattle plots it was mixed with clean material and held in the soil, and the authors measured results in soil, in vegetables and in lab-washed produce [3].
  • Most of the benefit comes from lower exposure, and a review of urban agriculture concluded that urban gardens are unlikely to raise children’s blood lead and that plant uptake of lead is typically very low. The exceptions are low-growing leafy crops, where soil splash is the problem, and root vegetables such as carrots. Composts and keeping soil out of homes reduce exposure [6].
  • The studies are small and local, and soil chemistry changes from city to city, so results may not carry over.

Where biology fits

Biology works around the edges of a lead problem in three ways.

  1. Good cover and soil structure cut bare ground and the dust that carries lead particles. EPA’s gardening guidance lists covering bare soil with ground cover or mulch as a basic step [11].
  2. Compost raises organic matter and is one of the amendments in the field plots above [3].
  3. In phytoextraction studies, microbes paired with plants increased lead uptake [4], although the approach is slow and leaves contaminated plant material to dispose of.

Bioavailability

The environmental risk from soil lead depends on bioavailability, which in turn depends on how soluble the lead-bearing solids are and on the soil chemistry at that site [2]. That is how phosphate and other amendments lower risk without removing any lead: they change the chemistry that governs how much a person or plant can take up [2]. A lab report giving only total lead can therefore overstate or understate exposure, which is why researchers also measure bioaccessibility and plant uptake [3][6].

Before choosing any option

  • Test first with a certified lab, and ask about the method and whether the lab can report bioaccessible lead along with total lead.
  • Map the lead, because it often varies a lot across one lot and a single sample can mislead.
  • Call your health department about exposure and blood lead, and the state environmental agency about cleanup rules and moving soil.
  • Land banks and municipalities should decide the end use first, since a parking lot, a park and a garden need different answers.
  • Check which screening level a report used, because a result of 150 mg/kg is above California’s 80 mg/kg level and below EPA’s 200 mg/kg, so the same number reads differently under each rule.
  • Ask about depth and sample count, since surface and deeper samples can differ and one sample may not represent a whole lot.
  • Ask who set the level and when, given that EPA issued new residential lead guidance in January 2024 and replaced it in October 2025 [7].

Your site

How a site’s soil chemistry, pH and amendment history would change these results gets answered on the site, with before-and-after testing by an independent lab. If you are planning a cleanup, a community garden or a land-bank program and need help reading results, reach out.

Sources

All links checked 2026-10-01.

  1. Gadd GM. Metals, minerals and microbes: geomicrobiology and bioremediation. Microbiology 156(3):609 to 643 (2010). doi:10.1099/mic.0.037143-0
  2. Hettiarachchi GM, Pierzynski GM. Soil lead bioavailability and in situ remediation of lead-contaminated soils: a review. Environmental Progress 23(1):78 to 93 (2004). doi:10.1002/ep.10004
  3. Defoe PP, Hettiarachchi GM, Benedict C, Martin S. Safety of gardening on lead- and arsenic-contaminated urban brownfields. Journal of Environmental Quality 43(6):2064 to 2078 (2014). doi:10.2134/jeq2014.03.0099
  4. Sun L, Cao X, Li M, Zhang X, Li X, Cui Z. Enhanced bioremediation of lead-contaminated soil by Solanum nigrum L. with Mucor circinelloides. Environmental Science and Pollution Research 24(10):9681 to 9689 (2017). doi:10.1007/s11356-017-8637-x
  5. Los Angeles County Department of Public Health. Public Health Releases Final Findings of Soil Testing in Fire-Impacted Areas. Press release, September 12, 2025. publichealth.lacounty.gov
  6. Brown SL, Chaney RL, Hettiarachchi GM. Lead in urban soils: a real or perceived concern for urban agriculture? Journal of Environmental Quality 45(1):26 to 36 (2016). doi:10.2134/jeq2015.07.0376
  7. U.S. EPA. Residential Soil Lead Directive for CERCLA Sites and RCRA Hazardous Waste Cleanup Facilities (directive issued October 16, 2025). epa.gov
  8. U.S. EPA. Regional Screening Levels (RSLs). epa.gov
  9. Hawaii Department of Health. Residential confirmatory soil sampling, Maui wildfires. health.hawaii.gov
  10. Dossou SA, Kelly L, Lu PL, Jones R, O’Donnell O, Walsh JSP, Richter DD. Urban conflagrations: structural ash and soil metal(loid) contamination after California’s Eaton and Palisades fires. Environmental Science & Technology Letters 13(6):818 to 824 (2026). doi:10.1021/acs.estlett.6c00268
  11. U.S. EPA. Healthy Gardening Practices to Reduce Exposure to Lead-Contaminated Soil. epa.gov

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