EPA Releases May 2014 RSLs – Here’s What You Need To Know
What risk managers should know about these RSL updates and how they may affect your remediation risk-based projects
In May 2014, the United States Environmental Protection Agency (USEPA) released the updated Regional Screening Levels (RSLs) that were developed using risk assessment guidance from the USEPA Superfund program. Although the RSLs were developed for the Superfund program, most federal and state risk-based environmental cleanup programs reference the RSLs. Based on the current revisions, changes to the RSLs were both chemical-specific and based on individual chemical toxicities and risk drivers (i.e., carcinogenic versus noncarcinogenic), and incorporate changes in standard default exposure parameters for several major potential exposure pathways.
EHS Support routinely uses the RSLs in the risk assessment process to determine if there is a potential need for further investigation, or whether a site-specific risk assessment is required for cleanup of a site. We have also incorporated the RSLs in state-led risk assessments where their guidance requires the use of the RSLs. These requirements include either in setting standards or as a source of toxicity criteria for a toxicity assessment. EHS Support also conducts a cost-benefit analysis before using RSLs as remedial standards by comparing remedial action costs versus the cost of a site-specific risk assessment.
What are the significant changes?
Toxicological values were revised and/or added for several constituents based on updates to the Provisional Peer Reviewed Toxicity Values for Superfund (PPRTV. The changes include the reference dose (RfD) and reference concentration (RfC).
Changes based on PPRTV:
- guanidine chloride, RfD added
- guanidine, RfD added
- azodicarbonamide, RfD added, RfC added
- dicyclopentadiene, RfD increased, RfC decreased
- 1,2-trans dichloroethylene, RfC removed
- Aroclor 5460, RfD added.
The change of toxicological values for the 6 constituents listed above will result in changes to the RSLs or their use in risk assessments for these constituents. If you have a project where one of these constituents may be present, EHS Support will evaluate whether the change in the RSLs could affect the characterization of potential risks in a quantitative risk assessment. For those constituents with a decrease in an RfC, a more stringent RSL might be developed; and an increase in the RfD might result in a more lenient RSL. If an RfD or RfC was added,a new exposure pathway (i.e., soil ingestion) might be evaluated by an RSL.
What were the other changes that were made to RSL chemicals?
- 1,2-dichloroethylene (mixed isomers) was removed because the RSLs were higher than the individual isomers.
- An OSWER Directive instructed the use of updated standard default exposure parameters, and all of the RSL equations have been updated accordingly.
- The cancer toxicity values have been removed for the total petroleum hydrocarbons.
- The new construction worker land use equations were modified to more clearly define averaging time and time of exposure for exposures less than one year.
- For the residential land use, the exposure frequency was moved into the age-adjusted intake portion of the equation. Now each age segment can have a unique exposure frequency.
- Trichloroethylene’s RSL calculation has changed from a three step process to a seamless calculation.
- All Furans were assigned an ABS of 0.03 for this version of the RSLs.
- A new key column noting carcinogenic versus non-carcinogenic endpoint was added after the Risk-based SSL column.
- FAQs were updated or added to explain:
- How the RSL tables and calculator handle rounding
- Three and four phase equilibrium modeling
- TCE equation changes
- TPH screening.
Where can I find the RSLs and specific information on the updated sections?