Screening Levels

The Screening Levels are chemical-specific concentrations for individual contaminants in air, drinking water and soil that may warrant further investigation or site cleanup.

Resident SoilIndustrial SoilResident AirIndustrial AirTapwater
1.6 mg/kg230 mg/kg0.042 μg/m30.18 μg/m34.0 μg/L
Screening Levels for “Uranium” (Last Updated by the EPA in November 2020)

Maximum Contaminant Level

The Maximum Contaminant Level (MCL) is the highest level of a contaminant that is allowed in drinking water.

MCL: 30 μg/L

National Primary Drinking Water Regulations for “Uranium” (Last Updated by the EPA in May 2009)

Uranium-235

Decay Chain U235.svg
Source: https://metadata.berkeley.edu/nuclear-forensics/Decay%20Chains.html

The stable isotope within the Uranium-235 decay chain is lead (Pb-207). In an area with Uranium-235 contamination, there could also be lead contamination.

Uranium-238

Decay Chain U238.svg
Source: https://metadata.berkeley.edu/nuclear-forensics/Decay%20Chains.html

The stable isotope within the Uranium-238 decay chain is lead (Pb-206). In an area with Uranium-238 contamination, there could also be lead contamination.

Units

AbbreviationMeaningNotes
mg/kgmass of chemical (milligrams, mg) per mass of soil (kilogram, kg)Equivalent to parts per million (ppm)
μg/m3mass of chemical (micrograms, mg) per volume of air (cubic meter, m3)This can be converted to ppm using the molecular weight of the chemical
μg/Lmass of chemical (micrograms, μg) per volume of water (liter, L)Equivalent to parts per billion (ppb); divide by 1,000 to get ppm

For more information about these units and their conversion factors, visit https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileid/14285.