A lead result only makes sense next to the right reference value for that kind of sample. Pick your sample type, enter the number and unit from your report, and the tool shows how it compares with the federal value that applies, with the source.
In short: water, soil, dust and paint results use different units and different standards, and they cannot be swapped. This tool is educational guidance for reading a report you already have. It is not a test, a formal risk assessment or medical advice.
How to use the interpreter
- Choose the sample type: drinking water, soil, dust wipe or paint. For a blood result, use the blood lead level explainer instead.
- Enter the number and the unit exactly as printed on the lab report or kit. If the report says “less than” or “not detected,” choose that option.
- Add the details the tool asks for, such as where a dust wipe was taken (floor, window sill or window trough) or whether soil came from a play area.
Units: why they are not interchangeable
| Sample | Usual units | What the number means |
|---|---|---|
| Drinking water | ppb = µg/L (micrograms per liter) | Lead dissolved or carried in the water you collected |
| Soil | ppm = mg/kg = µg/g | Lead in a weight of soil |
| Dust wipe | µg/ft² (micrograms per square foot) | Lead wiped from a measured area of floor or sill |
| Paint | mg/cm² (XRF reading) or % by weight (lab chip test) | Lead per area of painted surface, or in a weight of paint |
A dust wipe in µg/ft² measures lead on a surface area; a soil result in ppm measures lead in a weight of soil; a water result in ppb measures lead in a volume of water. There is no conversion between them, so a dust result can never be compared with a soil or water limit. Even within one sample type, the sampling method matters: a first-draw water sample and a flushed sample from the same tap can give very different numbers.
How to read the results
Water
EPA’s health goal for lead in drinking water (the MCLG) is zero, because EPA says there is no safe level of exposure to lead. The 15 ppb “action level” you may see is a trigger for water systems: if more than 10 percent of a utility’s tap samples are above it, the utility must take extra steps. It is not a safe level for your tap. Any lead in your water is worth acting on; see how to test water for lead and lead water filters.
Soil
Under EPA’s rule for homes and child-occupied facilities, a soil-lead hazard is bare soil with 400 ppm or more of lead in a play area, or an average of 1,200 ppm in the rest of the yard. See lead in soil testing.
Dust wipes
Since January 12, 2026, EPA treats any reportable level of lead in a floor or window sill dust wipe, analyzed by an EPA-recognized (NLLAP) lab, as a dust-lead hazard. Separate clearance levels apply after lead abatement work: 5 µg/ft² for floors, 40 µg/ft² for window sills and 100 µg/ft² for window troughs. See lead dust testing.
Paint
Federal rules define lead-based paint as paint with 1.0 mg/cm² or more of lead, or 0.5 percent or more by weight. A home swab kit gives a color change, not a number, so it cannot be compared with these values. See how to test for lead paint.
Official references
- EPA, Basic Information about Lead in Drinking Water (MCLG of zero; 15 ppb action level)
- 40 CFR 745.65, Lead-based paint hazards (dust and soil hazard standards)
- EPA, Hazard Standards and Clearance Levels for Lead in Paint, Dust and Soil (2026 changes)
- 40 CFR 745.103, Definitions (lead-based paint: 1.0 mg/cm² or 0.5% by weight)
Limitations
The interpreter compares one number with one federal reference value. It cannot check how the sample was taken, whether the lab was certified, or whether your state uses a stricter value, and some do. A result below a reference value does not mean “no lead,” and a single sample may not represent your whole home. For decisions about a home, ask a certified risk assessor; for health questions, ask a doctor or your health department.
Frequently asked questions
What is a safe level of lead in water?
EPA’s health goal is zero. The 15 ppb action level is a trigger for utilities, not a safe level for your home.
My water report says 3 ppb. Is that the same as 3 µg/L?
Yes. For water, 1 ppb equals 1 µg/L. Some labs report in mg/L instead: 0.003 mg/L is also 3 ppb.
Can I compare my dust wipe result with the soil limit?
No. Dust wipes measure lead per area of surface and soil measures lead per weight of soil. Each has its own standard.
What does “ND” or “less than” mean on my report?
It means the lab did not find lead above the lowest amount its method can measure. Ask the lab what that lowest amount was, because it varies by lab and method.