PFAS 101

Regional Screening Levels Used in DoD Cleanups

The information on this page updates the memorandum attachment [Update to Assistant Secretary of Defense for Energy, Installations, and Environment Memorandum, “Investigating Per- and Polyfluoroalkyl Substances within the Department of Defense Cleanup Program,” August 24, 2023] and lists the U.S. Environmental Protection Agency’s (EPA’s) Regional Screening Levels (RSLs) included in Department of Defense (DoD) investigations of per-and polyfluoroalkyl substances (PFAS) conducted under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and based on EPA’s November 2023 RSL update.

Screening levels for each PFAS may be found in EPA’s RSL table or by using EPA’s RSL calculator. The Department incorporates EPA’s RSLs into DoD environmental cleanup investigations when they are derived from final, peer reviewed toxicity values. Toxicity values used in DoD cleanup are based on assessments that are: transparent; have been externally and independently peer reviewed; completed with a previously published and publicly available methodology; based on studies that use the best use of all available science; and are publicly available or accessible. (See DoD Instruction on Emerging Chemicals (ECs) of Environmental Concern (DoDI 4715.18, 2024), Appendix 3A).

PFAS analytes with RSLs derived from final, peer reviewed toxicity values that DoD will use for determining if a remedial investigation is needed, and in CERCLA risk assessments, are provided in the table below. Unless there is only one PFAS present or the conceptual site model (CSM) can demonstrate that a target hazard quotient (THQ) of 1.0 is appropriate, sites with multiple PFAS must use residential soil or tap water RSLs set at a target risk of 1E-06 or a THQ of 0.1 for initial screening purposes.

Table 1: RSLs Included in DoD Investigations of PFAS

# Chemical Chemical Abstract Service (CAS) Number Analyte Abbreviation
1 Perfluorooctanesulfonic Acid 1763-23-1 PFOS
2 Perfluorooctanoic Acid 335-67-1 PFOA
3 Perfluorobutanoic Acid 375-22-4 PFBA
4 Perfluorobutanesulfonic Acid 375-73-5 PFBS
5 Perfluorononanoic Acid 375-95-1 PFNA
6 Perfluorohexanoic Acid 307-24-4 PFHxA
7 Perfluorohexanesulfonic Acid 355-46-4 PFHxS
8 Bis(trifluoromethylsulfonyl)amine1, 2 82113-65-3 TFSI
9 Hexafluoropropylene Oxide Dimer Acid2, 3 13252-13-6 HFPO-DA
10 Perfluoropropanoic acid1 422-64-0 PFPrA

1 There are no current EPA-approved analytical methods to measure TFSI and PFPrA. Even if a site’s conceptual site model (CSM) includes analysis of TFSI or PFPrA, only analytes listed on a laboratory’s DoD Environmental Laboratory Accreditation Program (ELAP) certificate can be included in the analyte list. Please notify OSD prior to incorporating these RSLs and analyzing for these analytes.

2 HFPO-DA has primarily been used as a replacement for PFOA in the manufacture of fluoropolymers and TFSI has been used in the manufacturing and disposal of batteries. It is not likely that these PFAS have been released at the vast majority of DoD properties. As with all chemicals, the CSM should be used to determine the necessity for addressing HFPO-DA and TFSI.

3 Chemical-specific parameters for PFAS were updated promoting consistency among acid, ion, and salt forms. The tap water RSL for HFPO-DA was impacted by these changes due to dermal absorption associated with potable water use. While it is unlikely that HFPO-DA will be included as part of a site’s CSM, the project team should ensure laboratory maximum detection level capabilities for HFPO-DA that are low enough to address inclusion of HFPO-DA dermal toxicity values if needed.