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
78 mg/kg12 mg/kgN/AN/A20 μg/L
Screening Levels for “Thallium” (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: 2 μg/L

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

Units

AbbreviationMeaningNotes
mg/kgmass of chemical (milligrams, mg) per mass of soil (kilogram, kg)Equivalent to parts per million (ppm)
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.