Lead: Myths and Facts

 

Myth: All urban soils are polluted and it is not safe for me to garden: I need to build raised beds.

Facts: While urban soils may have elevated lead, most are not sufficiently contaminated to pose a significant health risk. Research [1] suggests most urban soils have lower lead concentrations than the EPA’s residential soil screening limit of 400 mg/kg, which is used to identify soils safe for residential use. However, the only way to know whether your soil has a lead problem is to test it. We recommend heavy metal screening for sites that are urban, industrial, within 10 feet of a current or former structure that was built before 1960, or have an unknown history. 

[1] Datko-Williams, L., Wilkie, A., & Richmond-Bryant, J. (2014). Analysis of U.S. soil lead (Pb) studies from 1970 to 2012. Science of The Total Environment, 468-469, 854-863. 

Myth: Planting sunflowers, Indian mustard, fruit trees, or other flowering plants can draw lead out of the soil.

Facts: Planting sunflowers, indian mustard, or other flowering plants in your garden will have little effect on soil lead concentrations [2]. Phytoremediation, or using plants to remove heavy metals from soils, is an effective strategy for remediating some heavy metals like zinc and nickel. However, lead is held strongly by the soil and not easily removed by plants. Phytoremediation of lead uses chemicals to increase the amount of lead taken up by plants [3]. These chemicals are not readily available to the public and carry a high risk of transferring lead to the groundwater. For these reasons, we do not recommend phytoremediation. See "Managing and Treating Contaminated Soil" for recommendations on manging contamianted soil. 

[2] Blaustein, R. (2017, August 10). Phytoremediation of Lead: What Works, What Doesn't. Retrieved from https://academic.oup.com/bioscience/article/67/9/868/4080176
[3] Huang, J. W., Chen, J., Berti, W. R., & Cunningham, S. D. (1997). Phytoremediation of Lead-Contaminated Soils:  Role of Synthetic Chelates in Lead Phytoextraction. Environmental Science & Technology, 31(3), 800-805

Myth: The danger in gardening in a high lead soil is contaminated vegetables.

Facts. Some studies suggest that lead exposure from gardening is primarily from vegetables. Others suggest the soil itself is the main risk, as people accidentally swallow soil from dust or dirty hands. Both pathways should be addressed when gardening. See "Managing and Treating Contaminated Soil" for best practices to reduce incidental ingestion and plant lead uptake when gardening. 

Myth: A raised bed is the only solution for gardening in a lead-contaminated soil.

Facts: Soils with elevated but low lead levels can be used without concern. Moderately contaminated soils can be gardened when best practices and soil treatments are used. See "Interpreting Garden Lead Test Results" for specific guidelines on soil lead concentrations and best-practices. 

Myth: My soil looks healthy and plants grow well in it. This soil is safe for gardening.

Many soil contaminants, including lead, arsenic, and cadmium, are more toxic to people than they are to plants. This means that a healthy garden may stil have harmful concentrations of heavy metals. See "Urban Agriculture and Garden Testing" for testing information. 

Myth: My home was built pre-1960s, but it’s not painted. There’s no lead in my soil.

Facts: Soil lead may still be present from past industrial activities and use of leaded gasoline. This is more likely to occur in urban areas, so we recommend testing on all urban sites. See "Urban Agriculture and Garden Testing" for testing information. 

Myth: Buying soil for raised beds is guaranteed way to reduce lead exposure.

Facts: Soil providers are not required to test for lead. We recommend testing. See "Urban Agriculture and Garden Testing" for testing information.