Soil Testing for Lead and Contaminants in Urban Gardens
Lab test or home test kit?
You have three realistic choices. For a garden where children or sold produce are involved, use a laboratory.
| Option | Good for | Limits |
|---|---|---|
| University extension soil lab | Basic pH and nutrients, and in many states a metals or lead test. Often the cheapest way to start. | Not every extension lab tests for contaminants. Ask whether lead and metals are on the menu. |
| Private environmental laboratory | Lead and other metals, organic chemicals such as PAHs and petroleum compounds, and tests designed for a particular site history. | Costs more and the report is written for professionals, so ask how to read it. |
| Home test kit | A rough screen for one or two metals when you cannot yet send a sample. | Accuracy and detection limits vary by product, and a kit result should not be your only evidence for sold or donated produce or for gardens with children. |
If you use a lab, ask five questions before you send anything: which metals and chemicals are included, in what units the results come back, what the lowest reportable value is, whether the lab is certified or accredited by your state for environmental testing, and how long results take.
How to take a soil sample
The lab’s own instructions come first. If they differ from the steps below, follow the lab. These steps match the general approach in extension sampling guides.
- Draw a map and divide the site.Mark each bed, play area and old building edge. Plan one sample for each distinct area, not one for the whole lot.
- Choose clean tools and containers.Use a clean plastic trowel or stainless steel tool and a clean plastic bucket. Rust, galvanized metal and dirty tools can change results for some metals.
- Take several small samples in each area.Dig to the depth the lab asks for. Many labs want the top few inches where roots and children contact the soil. Take samples from several spots in the same area.
- Mix the spots into one sample.Combine the spots in the bucket, remove stones and plant material, and let the soil air dry if the lab asks for that.
- Bag, label and record.Use the lab’s bag or a clean sealable bag. Label it with the area name and write the date, depth and location on your map.
- Add extra samples where risk is higher.Take separate samples next to old painted buildings, along busy roads, near fences with old paint and anywhere children will play.
What to test for
Match the test to the history of the site.
| If the site had | Ask the lab to test for | Why |
|---|---|---|
| Older houses, flaking paint or demolition | Lead | Lead paint was widely used before 1978. |
| Busy road, old highway or rail line | Lead, other metals and PAHs | Traffic and rail leave metals and combustion by-products. |
| Treated lumber, fence posts or railroad ties | Arsenic, chromium, copper and PAHs | Wood preservatives and creosote contain these. |
| Gas station, garage, tanks or heating oil | PAHs, benzene, toluene, xylene and petroleum compounds | These come from fuel and oil. |
| Factory, dry cleaner, metal shop or rail yard | Metals and a solvent or broader environmental package; consider a Phase 1 review | Industrial uses vary, so a professional review helps choose tests. |
| Orchard, nursery or heavy past pesticide use | Lead, arsenic and a pesticide screen | Some older pesticides left metals or persistent chemicals. |
| Imported fill or compost of unknown origin | Metals, plus ask for the supplier’s own test results | The source decides what is in it. |
If the site history is unclear or points to industry, a Phase 1 site assessment is a better first step than guessing at a list of tests.
What does a soil test cost?
There is no single price. The cost depends on the laboratory, the number of samples and which contaminants you choose. A simple pH and nutrient test is usually the cheapest, a lead or metals test costs more, and a broad environmental package or a professional site assessment costs the most. Prices change, so this page does not list dollar amounts. Do these three things instead:
- Ask two or three labs for a written quote that lists what each sample includes.
- Ask whether the lab offers a discount for community gardens, schools or nonprofits.
- Group samples sensibly: composite samples from each distinct area cost less than testing many single spots, but do not mix areas with different risks.
Free and low-cost soil testing
Free soil testing programs exist but they come and go. Places to ask:
- your county or state university extension office, which may run a soil lab or know a certified one;
- your state or local health department, which sometimes runs lead screening events;
- your city garden program, parks department or land bank, which may test lots it leases or sells to gardeners;
- a city or state Brownfields program. EPA Brownfields assessment grants can pay for property-specific soil testing, but only governmental entities are eligible, so a garden group usually works through a city or state partner;
- a nearby university or master gardener program, which sometimes runs sampling days.
How to read a soil test report
| Term | What it means |
|---|---|
| ppm or mg/kg | Parts per million, the same as milligrams of metal per kilogram of dry soil. Most lead numbers are given this way. |
| Total lead | All the lead in the sample. This is what most screening levels use. |
| Reporting limit | The lowest value the lab can report. A result of “<5” means below that limit. |
| Dry weight | Results corrected for the water in the sample so labs can compare soils. |
| Screening level | A value used to decide whether to look closer. It is not a legal limit for gardens. |
| Method | The analytical method the lab used. Ask the lab if you need to compare it with a reference value. |
Compare the lead number with EPA’s 2024 residential screening levels of 200 ppm (or 100 ppm where another lead source is present), and with any value or guidance from your state. These are screening values for residential Superfund and RCRA sites, and not rules for gardens; see the soil overview for what each number means. If a result is above the screening level or the lab flags an unusual contaminant, call your state environmental or health agency before you plant, and read contaminated soil options.
Why pH still matters
Even though a pH test does not show lead, pH still matters for gardens that have some contamination. Extension and EPA fact sheets note that keeping soil near neutral, often given as a pH of 6.5 or higher, and adding compost and other organic matter can reduce how much lead plants take up. Sources differ on the exact target, so follow the advice of your extension office. These steps reduce risk but do not make contaminated soil safe.
When to retest
- After you bring in new soil, compost or fill.
- After nearby demolition, construction or heavy dust.
- Every few years in raised beds near roads or older painted buildings.
- After a flood, or any spill or dumping on the site.
- Whenever a new use begins, such as a children’s area or produce sales.
Frequently asked questions
Where can I get my soil tested for lead?
Start with your county extension office, which can tell you whether it runs a lab or recommends a certified environmental lab. Your health department and city garden program may also help.
How do I find a soil testing lab?
Ask your extension office or state environmental agency for certified labs, and ask each lab which metals and chemicals it tests, the units, the reporting limit and the turnaround time.
How much does a soil test cost?
It depends on the lab and the tests. A pH and nutrient test is cheaper than a lead or metals test, and a broad contaminant package costs more. Ask for a written quote.
Is there free soil testing?
Sometimes. Extension offices, health departments, city garden programs and university projects occasionally offer free or subsidized testing. Programs change, so ask locally.
Are home soil test kits accurate?
Kits can give a rough screen, but accuracy and detection limits vary. For a community garden, children or sold produce, use a laboratory.
Does a soil pH test show if my soil is contaminated?
No. It only measures acidity. Order a lead or metals test.
How deep should I sample garden soil?
Follow your lab’s instructions. Many ask for the top few inches, where roots and children are in contact with the soil.
How many samples do I need?
One mixed sample for each distinct area, such as each bed group, play area and old building edge, made of several small samples from that area.
What should I test for in a vacant lot?
Lead first, then other metals, and PAHs or petroleum compounds if there were fuel tanks, garages or burning. A Phase 1 review can help choose tests.
What does a soil test report number mean for my garden?
It is a total concentration in ppm. Compare it with screening levels such as EPA’s 200 ppm (100 ppm where another source is present) and with your state’s guidance, and ask the lab or health department to help interpret it.
How often should I test my garden soil?
Test before you plant, then retest after adding soil, after nearby construction or every few years in higher-risk raised beds.
Can the city require a soil test for a community garden?
Some cities and landlords do, especially on public land. Many have no rule. Check your city garden or land program.
Official sources
- U.S. EPA, Know Before You Grow: Understanding Site Risks for Garden and Growing Activities (EPA-560-F-21-201, October 2021)
- U.S. EPA, memorandum on updated residential soil lead guidance, January 17, 2024
- U.S. EPA, Brownfields and Urban Agriculture: Interim Guidelines for Safe Gardening Practices (2011)
- University extension soil sampling guides for your state
- Your state environmental agency, state health department and county extension office
- Not checked for this page: laboratory prices, home kit accuracy, and which labs are certified in each state