Lead in Residential Soils: Sources, Testing, and Reducing Exposure

Summary

This information integrates findings from peer-reviewed research and federal public health guidance from the U.S. Environmental Protection Agency (EPA) and the National Institutes of Health (NIH).

Why Lead in Soil Matters

Lead is a naturally occurring metal found in most soils at low concentrations. However, past human activities—especially the use of lead-based paint, leaded gasoline, and certain industrial emissions—have resulted in elevated soil lead levels in many residential areas. Urban gardening and raised-bed gardening are increasingly common ways for communities to grow food and engage with their local environment (Figure 1), but these activities can bring people into direct contact with potentially contaminated soils. Soil near older homes, especially close to building foundations painted with lead-based paint, can contain very high lead levels. In these areas, soil lead concentrations may range from about 150 mg/kg to as high as 10,000 mg/kg (Cheng et al., 2015; Haque et al., 2021). Unlike many contaminants, lead does not degrade over time and can persist in soil for decades or centuries (EPA, 2001; Filippelli and Laidlaw, 2010)

Exposure to lead is a significant public health concern, particularly for young children. Even low-level, chronic exposure has been associated with impacts on cognitive development, behavior, and academic performance (Lanphear et al., 2005; NIH, 2022). Because the human body removes lead slowly, preventing exposure is the most effective way to reduce health risks.

Major Sources of Lead in Residential Soils

Research shows that the primary contributors to elevated residential soil lead include legacy lead-based paint, historical vehicle emissions from leaded gasoline, and past industrial activities (Mielke and Reagan, 1998; Filippelli and Laidlaw, 2010).

Homes built before 1978 are more likely to have used lead-based paint. As paint ages, chips and dust accumulate in nearby soil, often producing higher concentrations near building foundations (EPA, 2001). Vehicle emissions from leaded gasoline, which was phased out in the United States by the late 1980s, deposited lead particles along roads and into adjacent yards. In some communities, smelting, manufacturing, and coal combustion also contributed to long-lasting soil contamination (Laidlaw and Filippelli, 2008).

How Lead Behaves in Soil

Lead strongly binds to fine soil particles such as clay and organic matter, and it is typically concentrated in the top few inches of soil unless the soil has been disturbed by digging, construction, or gardening (Alloway, 2013). These fine particles can adhere to skin and clothing, become airborne as dust, and can be tracked into homes on shoes, clothing, or pets becoming part of household dust.

Soil chemistry influences how tightly lead is held. Acidic soils increase lead solubility, whereas neutral soils, higher organic matter, and iron-rich minerals tend to immobilize lead, reducing its movement and bioavailability (Sparks, 2003; Alloway, 2013).

Not all lead in soil is equally available to plants (or to people if soil or dust is accidentally swallowed). Lead availability depends strongly on soil conditions. In acidic soils (pH below 5), lead dissolves more easily and is therefore more available. In neutral to slightly alkaline soils (pH 6.5–7.0), lead is held more tightly and is less available. Clay-rich soils also retain lead more strongly than sandy soils. Soils with higher organic matter (such as those with compost) have more surfaces that can bind lead and reduce its movement. Naturally occurring minerals, especially iron compounds, can further bind lead in place, and phosphorus can react with lead to form very stable minerals. Overall, soil chemistry and mineralogy play an important role in determining how tightly lead is bound and the risk it may pose.

These soil properties are important because they influence how management practices such as maintaining neutral soil pH, adding organic matter, or applying phosphorus can reduce lead mobility and exposure risk.

Exposure Pathways

People are exposed to soil lead primarily by ingesting or inhaling contaminated soil or dust during dry or windy conditions (Mielke et al., 2007; CDC/NIH, 2022). Young children are at greatest risk due to normal hand-to-mouth behavior and higher soil ingestion rates (EPA, 2011). Children may ingest small amounts of soil during outdoor play, and contaminated dust can also accumulate on indoor surfaces and toys (Figure 2).

Additional exposure pathways include consumption of produce grown in lead-contaminated soil. Plant uptake of lead is generally very low. An important exception is expanded hypocotyl root crops (root vegetables with thickened stems, such as carrots, radishes, and beets), which may accumulate lead in their edible portions. Other crops, including low-growing leafy vegetables and potatoes, may also present a greater risk of contamination due to soil adhesion (the tendency of soil particles to adhere to plant surfaces). In contrast, fruiting crops such as tomatoes, peppers, beans, squash, and cucumbers generally pose a lower risk because lead is poorly translocated into fruits and the edible portions of crops develop above the soil surface (Brown et al., 2016; Finster at al., 2004) (Table 1).

Testing Residential Soil for Lead

Testing soil is the most reliable way to determine whether lead contamination is present and to guide risk-reduction decisions. Federal and academic guidance recommends testing soils around older homes, near roadways, in children’s play areas, and in vegetable gardens (EPA, 2001; Filippelli and Laidlaw, 2010).

Soil samples should be collected from the upper 1–2 inches in undisturbed areas and to a depth of about 6 inches in gardens or recently mixed soils. Multiple subsamples from each area should be combined and submitted to a certified laboratory for total lead analysis, along with soil pH and phosphorus to inform management options.

Several laboratories in Pennsylvania, including Penn State's Agricultural Analytical Services Laboratory, can test soils for lead. Before collecting samples, contact the laboratory for instructions and required forms. Soil testing generally involves a few steps.

1. Select sites. Sample areas where lead contamination is more likely (near older painted structures or roadways) and areas where exposure is more likely (gardens and play areas) (Fig. 3). Sample each area separately and keep a simple map of sampling locations.
2. Collect soil. In undisturbed areas, collect from the upper 1–2 inches. In gardens or disturbed areas, collect to a depth of 6 inches. Take 8–12 subsamples per area, mix them in a clean plastic bucket, then submit about one cup of air-dried soil for analysis.
3. Send to a lab. Request total soil lead, and also request soil pH, lime requirement, and soil phosphorus to help guide management steps.

In some situations, rapid field screening can help identify areas of potential contamination before laboratory testing.

Rapid Screening with Portable XRF

Portable X-ray fluorescence (XRF) instruments allow rapid field screening of soil Pb concentrations across yards and community spaces (Figure 4). Studies show that XRF can effectively identify spatial patterns of contamination, although laboratory confirmation is recommended when results are near regulatory thresholds (Kalnicky and Singhvi, 2001; EPA, 2007).

Because soil moisture, particle size, and soil composition can influence XRF readings, results should be treated as screening data, not definitive concentrations. For decisions near the EPA residential soil screening level of 200 ppm, selected samples should be confirmed using EPA method 3050B or 3051, which are the approved regulatory methods for soil lead analysis.

One way to increase confidence in XRF screening results is to test a small number of soil samples using both XRF and a standard laboratory method. Comparing these results helps show how XRF readings relate to laboratory values for a specific site. This comparison can be used to adjust XRF results, so they more closely reflect laboratory measurements. Doing this improves how XRF data is interpreted, but some uncertainty will always remain, especially the results close to the screening level.

This uncertainty matters most when XRF results are close to the EPA screening level. As a general guideline, XRF values below 200 ppm are likely below the screening level. When XRF results fall near 200 ppm (approximately 150–250 ppm), laboratory confirmation is strongly recommended. If corrected estimates, considering uncertainty, could exceed 200 ppm, it is safest to manage the soil as above the screening level and take appropriate steps to reduce exposure.

Interpreting Soil Lead Levels

Soil lead concentrations can be reported as mg/kg, ppm, or μg/g—these units are equivalent; however, soil lead concentrations are most often reported in parts per million (ppm). The EPA residential soil screening level of 200 ppm is commonly used as a health-protective benchmark (EPA, 2026). Research indicates that children’s blood lead levels increase as soil lead concentrations rise, even below older regulatory thresholds (Lanphear et al., 2005; Mielke et al., 2007).

General interpretations and guidance for lead risk reduction:

Less than 200 ppm: Maintain ground cover (grass or mulch). Practice good hygiene, including handwashing after outdoor activities. Follow safe gardening practices.

200–400 ppm: Cover bare soil and limit direct contact. Maintain soil pH between 6.5 and 7.0 and add organic matter. Avoid growing leafy greens and all root crops. Wash garden produce thoroughly.  

400–1,000 ppm: Restrict children’s and pets’ access to soil. Avoid growing edible crops. Keep soil covered with mulch or healthy turfgrass. Use raised beds filled with clean soil for growing vegetables.

Greater than 1,000 ppm: Do not garden in native soil and avoid direct contact. Keep the soil well covered. Contact your local Extension office or health department for guidance.

Note! These are general guidelines, not a call for action. The health effects of lead depend on factors such as age and individual health history. If your soil lead level exceeds 200 ppm, consider discussing potential exposure with your healthcare provider.

Reducing Exposure to Soil Lead

Evidence-based strategies can substantially reduce exposure to lead in residential settings (Figure 5). Key recommendations from EPA and NIH guidance include maintaining vegetative cover or mulch over bare soil, removing shoes before entering homes, and using wet cleaning methods to reduce indoor dust (EPA, 2001; NIH, 2022).

For gardening, raised beds filled with clean soil are recommended where native soil lead is elevated. Thorough washing of produce, peeling root crops, and discarding outer leaves of leafy vegetables can further reduce ingestion of soil particles (Clark et al., 2008; EPA, 2014).

Creating play areas away from older painted structures and busy roads and ensuring children wash hands after outdoor play are additional effective preventive measures supported by public health research (CDC/NIH, 2022).

Key Takeaways:

Legacy Pb contamination remains common in many residential soils but can be effectively managed. Testing soil, maintaining ground cover, practicing good hygiene, and using safe gardening methods are practical steps that significantly reduce exposure. Preventive actions are especially important for protecting young children, who are most vulnerable to the health effects of lead.

References

Alloway, B.J. (2013) Heavy Metals in Soils: Trace Metals and Metalloids in Soils and their Bioavailability. Dordrecht: Springer.

Brown, S.L., Chaney, R.L., and Hettiarachchi (2016). Lead in urban soils: a real or perceived concern for urban agriculture? Journal of Environmental Quality. 45:26-36

CDC/NIH (2022) Childhood Lead Poisoning Prevention. National Institutes of Health and Centers for Disease Control and Prevention.

Cheng Z., Paltseva A, .Li, I., Morin, T., Huot, H., Egendorf, S.P., et al (2015). Trace metal contamination in New York city garden soils. Soil Science. 180:167-174

Clark, H.F., Hausladen, D.M. and Brabander, D.J. (2008) ‘Urban gardens: Lead exposure, recontamination mechanisms, and implications for remediation design’, Environmental Research, 107: 312–319.

EPA (2007) Method 6200: Field Portable X-Ray Fluorescence Spectrometry for the Determination of Elemental Concentrations in Soil and Sediment. U.S. Environmental Protection Agency.

EPA (2011) Exposure Factors Handbook. U.S. Environmental Protection Agency.

EPA (2014) Best Management Practices for Lead in Outdoor Residential Soils. U.S. Environmental Protection Agency.

EPA (2026) ‘Residential Soil Lead Directive for CERCLA Sites and RCRA Hazardous Waste Cleanup Facilities’. Accessed January 11, 2026.

Filippelli, G.M. and Laidlaw, M.A.S. (2010) ‘The elephant in the playground: Confronting lead-contaminated soils as an important source of lead burdens to urban populations’, Perspectives in Biology and Medicine, 53:31–45.

Finster, M. E., Gray, K. A., & Binns, H. J. (2004). Lead levels of edibles grown in contaminated residential soils: a field survey. Science of the Total Environment, 320:245-257.

Haque, E., Thorne, P. S., Nghiem, A. A., Yip, C. S., & Bostick, B. C. (2021). Lead (Pb) concentrations and speciation in residential soils from an urban community impacted by multiple legacy sources. Journal of hazardous materials, 416, 125886.

Kalnicky, D.J. and Singhvi, R. (2001) ‘Field portable XRF analysis of environmental samples’, Journal of Hazardous Materials, 83:93–122.

Laidlaw, M.A.S. and Filippelli, G.M. (2008) ‘Resuspension of urban soils as a persistent source of lead poisoning in children: A review and new directions’, Applied Geochemistry, 23:2021–2039.

Lanphear, B.P. et al. (2005) ‘Low-level environmental lead exposure and children’s intellectual function: An international pooled analysis’, Environmental Health Perspectives, 113:894–899.

Mielke, H.W. and Reagan, P.L. (1998) ‘Soil is an important pathway of human lead exposure’, Environmental Health Perspectives, 106:217–229.

Mielke, H.W. et al. (2007) ‘Lead concentrations in inner-city soils as a factor in the child lead problem’, American Journal of Public Health, 97:967–972.

NIH (2022) Lead and Your Health. National Institutes of Health.

Sparks, D.L. (2003) Environmental Soil Chemistry. 2nd edn. San Diego: Academic Press.

U.S. Environmental Protection Agency, Lead in Soil (Washington, DC: EPA Region III, 2020), PDF.