EPA RSL November 2024 Update - What Changed and Key Values
EPA updated its Regional Screening Levels (RSLs) in November 2024, marking the second major revision this year. The update affects screening values for multiple chemicals commonly encountered in environmental site assessments.
Key changes include lower screening levels for several carcinogens and updated toxicity values based on recent health assessments. The revisions impact both residential and industrial soil screening levels, as well as tap water and ambient air values.
What Changed in the November 2024 Update
The most significant changes affect these chemicals:
- Benzene: Residential soil screening level decreased from 1.4 mg/kg to 1.1 mg/kg
- Arsenic: Industrial soil screening level dropped from 3.0 mg/kg to 2.4 mg/kg
- Tetrachloroethylene (PCE): Residential soil screening level reduced from 0.81 mg/kg to 0.64 mg/kg
- Trichloroethylene (TCE): Tap water screening level lowered from 0.46 μg/L to 0.37 μg/L
- 1,4-Dioxane: New residential soil screening level added at 0.35 mg/kg
The changes reflect updated cancer slope factors and reference doses from EPA’s Integrated Risk Information System (IRIS) database. Several chemicals also received new inhalation unit risk values that affected ambient air screening levels.
How This Affects Site Assessment Work
CERCLA and RCRA Corrective Action Sites
Sites using RSLs for preliminary remediation goals will need to apply the updated values to ongoing risk assessments. If your site has benzene or PCE contamination above the new screening levels, additional evaluation or remediation may be required.
For sites with existing Records of Decision or cleanup agreements, the new RSLs do not automatically trigger plan modifications. However, EPA may consider the updated values during five-year reviews or permit renewals.
Phase II Environmental Site Assessments
The updated screening levels affect how you interpret analytical results in Phase II ESAs. Soil concentrations that previously fell below screening thresholds may now exceed them, potentially requiring additional investigation or risk assessment.
This is particularly relevant for petroleum sites where benzene is a key constituent and industrial sites with historical solvent use where PCE and TCE are common contaminants.
State Program Applications
Many state cleanup programs reference EPA RSLs as screening tools or default cleanup standards. Check whether your state program automatically adopts EPA updates or maintains its own screening level schedule.
Ohio’s VAP program uses state-specific standards rather than EPA RSLs, so the November 2024 update does not directly affect Ohio VAP sites. However, consultants working on federal sites or using RSLs for preliminary screening should apply the updated values.
What to Do Now
If you conduct risk assessments or Phase II ESAs:
- Update your screening level databases: Replace May 2024 RSL values with November 2024 versions for affected chemicals
- Review active projects: Check whether any ongoing assessments have analytical results that now exceed updated screening levels
- Verify state program requirements: Confirm whether your state automatically adopts EPA RSL updates or maintains separate screening values
- Document RSL version used: Always specify which RSL table version you applied in reports to avoid confusion during regulatory review
The EPA RSL tables remain the primary federal screening tool for preliminary site assessments and risk evaluations. For detailed explanations of how RSLs work and when to use them, see our risk assessment guides.