Soil Contaminant Myths and Facts

Myth 1: All urban soils are polluted and are unsafe for gardening

Facts: While urban soils may have elevated lead, most are not sufficiently polluted to pose a significant human 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 a soil has a lead problem is to test it. Heavy metal screening is recommended for sites that are urban, industrial, within 10 feet of a current or former structure 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 2: 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 a garden will have little effect on soil lead concentrations [2]. Using plants to remove heavy metals from soils (phytoremediation), is an effective strategy for remediating some metals like zinc and nickel. However, lead is held strongly by the soil so plants only take up very small amounts of lead. Phytoremediation of lead requires added chemicals to increase lead availability to 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 managing contaminated 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 3: The danger to gardening in a high lead soil will be contaminated vegetables.

Facts. Some studies suggest that lead exposure from gardening is primarily from the small amount of lead taken up by vegetables. Others suggest the soil itself is the main risk, as people accidentally swallow soil from dust or dirty hands. Both routes of exposures 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 4: the solution for gardening in a lead-contaminated soil is to use A raised bed.

Facts: Soils with very low lead levels below 100 mg/kg can be used without concern. Soils with low to moderate lead levels (100 mg/kg- 800 mg/kg) 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 5: My soil looks healthy and the plants grow well, so it must be safe for gardening.

Facts: Many soil contaminants, including lead, arsenic, and cadmium, are more toxic to people than they are to plants. A healthy garden may still have harmful concentrations of heavy metals. See "Soil Heavy Metal Testing" for testing information. 

Myth 6: My pre-1960s home was not painted, so Lead is not a concern for my property.

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 testing urban sites is recommended. See "Soil Heavy Metal Testing" for testing information. 

Myth 7: Buying soil for raised beds will guarantee reduced lead exposure.

Facts: Soil providers are not required to test for lead. Testing is recommended. See "Soil Heavy Metal Testing" for testing information.