Answer to Question #12676 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Plants and Animals

The following question was answered by an expert in the appropriate field:

Q

What amount of uranium in the soil is considered safe for a vegetable garden? I live in the foothills of the Rocky Mountains in Colorado. My well water contained uranium and needed mitigation. I want to start a garden and had my soil tested. It came back as 0.7 milligrams per kilogram (mg kg-1) using method SW-846 6020. What does this mean? Thank you for your time and assistance.

A

Overall, there is no need for concern about the uranium in your soil.

The concentration of uranium you reported, 0.7 mg of natural uranium per kg of soil (mg kg-1), is typical for the United States. I converted the concentration you reported to slightly different units, and it is roughly 19 millibecquerels (mBq) per gram of soil (mBq g-1). The US Agency for Toxic Substances and Disease Registry (ATSDR) maintains a document that specifically addresses uranium. Section 6.1 of the ATSDR document on uranium indicates that the average concentration of natural uranium in soils is 74 mBq g-1 in International System units (equivalent to 2 picocuries per gram [pCi g-1] in traditional units used by ATSDR), which is higher than in your sample.

The ATSDR also indicates that little or no uranium will be taken into the roots of plants. So you can see why, overall, there is no need to be concerned about the uranium in your soil.

Thomas E. Johnson, PhD, CHP, NRRPT

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
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