The San Francisco Bay Regional Water Quality Control Board has updated its Environmental Screening Levels (ESLs), which includes a memo, an Excel workbook, summary tables, and a user’s guide. This is the first major update since 2019.
Key Changes in the July 2025 Update
The updated ESLs include several important revisions:
New PFAS ESLs: The updated ESLs now include screening levels for 14 new PFAS chemicals, in addition to updated values for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). There are now ESLs for a total of 16 different PFAS.
Updated Toxicity and Exposure Values: The values for physical and chemical properties in the ESL Workbook have been updated to align with the November 2024 USEPA Regional Screening Level (RSL) values. The toxicity values were also expanded to show all values considered, and the exposure factors for things like arsenic’s bioavailability and the construction worker exposure scenario were updated to be consistent with USEPA guidance.
Petroleum Fractions and Aquatic Habitats: The surrogates for Petroleum Fraction 5 were updated to match the latest RSLs, and new screening levels for petroleum fractions are now included in the risk tables for each media. Additionally, new goals for the protection of aquatic habitats were added to the ESLs, incorporating both State and National criteria for marine life and human health.
Tool and Guidance Improvements: The ESL Workbook’s Tier 2 tool was updated to provide specific leaching values for all possible scenarios. Information on vapor intrusion was removed from the ESL User’s Guide to reduce duplication, as it is now available in other guidance documents from the DTSC and Water Board.
Short-Term Exposure: New Short-Term Exposure Levels for elemental mercury have been added to the ESL Workbook and are discussed in an expanded chapter of the User’s Guide.
Memo: https://www.waterboards.ca.gov/sanfranciscobay/water_issues/programs/ESL/ESL_CoverMemo.pdf
Summary Tables: https://www.waterboards.ca.gov/rwqcb2/water_issues/programs/ESL/ESL_Tables.pdf
