Interpreting Heavy Metal Test Results

Interpreting Heavy Metal Test Results for Food production

Use this table to interpret your soil heavy metal test results. The values in the table are for total metal soil tests (also called XRF, x-ray fluoresence, strong acid extraction, total acid extraction; USEPA 3050 or USEPA 3051a). This table should no be used for lead estimates (also called weak acid extraction, nutrient tests, M3 or Mehlich-3, Modified Morgan). These tests do not extract all the lead in a soil and need a different interpretation, which may be available from that soil testing lab.

Interpretations for arsenic and cadmium are coming soon!

 

Total  Lead 

(ppm or mg/kg)                                                                                                      

Interpretation [1,2]

0-50

Background lead 

Soil Pb is at naturally occuring, or background, concentrations and is not polluted with human lead sources. In Ohio, background soil lead is at or below 50 mg/kg. Follow this link to find the background soil lead concentration in your state. There are no restrictions to using a soil with background lead concentrations.

50-100

Low lead

Soil lead is elevated above backround concentrations, but poses low risk to gardeners and those consuming garden produce. 

100-300

Moderate lead

Mulch all bare soil, including walkways. Use Best Practices to Reduce Exposure and consider Managing and Treating Lead-Contaminated Soil.

300-800

High lead

Mulch all bare soil, including walkways, and do not consume leafy or root crops grown in the soil. Consider using raised beds with tested soil. See Managing and Treating Lead-Contaminated Soil for ways to reduce soil lead exposure and toxicity.

800+

Very high lead

Cover bare soil. If soil lead concentration exceed 2,000 mg/kg, contact the local health department.

[1]  Pollutant concentration limits for land-applied biosolids. Code of Federal Regulations Title 40, Part 503. Retrieved from https://www.ecfr.gov/cgi-bin/retrieveECFR? gp=2&SID=3ba5c96eb4bfc5bfdfa86764a30e9901&ty=HTML&h=L&n=pt40.30.503&r=PART#se40.32.503_113.

[2] Stehouwer, R. (2018, December 23). Lead in Residential Soils: Sources, Testing, and Reducing Exposure. Retrieved from https://extension.psu.edu/lead-in-residential-soils-sources-testing-and-...