Regional Removal Management Levels (RMLs) User's Guide
Introduction
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly known as Superfund, authorizes two kinds of response actions: remedial and removal. Remedial actions are long-term actions that permanently and significantly reduce the dangers associated with releases or threats of releases of hazardous substance that are serious, but not immediately life threatening. In contrast, removal actions are short-term cleanups intended to stabilize or clean up a site that poses an imminent and substantial threat to human health or the environment. EPA addresses environmental contamination in a more efficient manner through the integration of these authorities, which is achieved though the remedial and removal programs using related triggers for initiating action and common goals for site cleanup.
The purpose of this website is to provide the Regional Removal Management Levels (RMLs) that can be used by On-Scene Coordinators (OSCs) and other site managers to evaluate the need to use removal authority at a site. The RMLs are chemical-specific concentrations for individual contaminants in tap water, air, and soil. They are derived using similar methodologies as the tools used in the remedial program but are calculated with risk levels and exposure scenarios that align with identifying areas, contaminants, and conditions where a removal action may be appropriate. Because of this, calculated RMLs should not be confused with or used as Regional Screening Levels (RSLs), Preliminary Remediation Goals (PRGs), cleanup levels or cleanup standards required by the Applicable or Relevant and Appropriate Requirements (ARARs) under CERCLA. All final cleanup values should be selected to address site-specific threats. Additionally, the decision to undertake a removal action is informed by various factors not limited to the evaluation of site contamination using the RMLs.
For proper application of the RMLs and to ensure understanding of RML exposure scenarios, please review the methodology section below as well as the RMLs Frequent Questions page.
Methodology
The RMLs are based on exposure and risk assessment methods presented in the Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part B, Development of Risk-based Preliminary Remediation Goals) (RAGS Part B) and Soil Screening Guidance:
RAGS Part B and the Soil Screening Guidance use toxicity values and exposure information to calculate risk-based screening levels. The relationship of Preliminary Remediation Goals (PRGs) to Regional Screening Levels (RSLs) and RMLs is discussed in more detail in the RMLs Frequent Questions.
This website presents “generic” risk-based RMLs for individual chemical contaminants.
Generic RMLs are based on default exposure parameters and factors that represent Reasonable Maximum Exposure (RME) conditions for long-term/chronic exposures. Generic RMLs are provided for tap water, air, and soil in a residential setting and for air and soil in an industrial setting.
The target risk levels for calculating generic RMLs are an extension of the Superfund program’s “Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions” (OSWER Directive 9355.0-30) guidance which states:
“Where the cumulative carcinogenic site risk to an individual based on reasonable maximum exposure for both current and future land use is less than 10-4 and the non-carcinogenic hazard quotient is less than 1, action generally is not warranted unless there are adverse environmental impacts. However, if Maximum Contaminant Levels (MCLs) or non-zero Maximum Contaminant Level Goals (MCLGs) are exceeded, action generally is warranted.”
The guidance cited above describes conditions at a site where remedial action generally is not warranted. As such, the associated risk levels correspond to a cumulative site risk less than approximately 10-4 for exposure to multiple chemicals with potential carcinogenic effects and a Hazard Quotient (HQ) less than 1 for those chemicals with potential non-carcinogenic toxicity. On the other hand, since RMLs may be used to support the decision to undertake a removal action at a site, they can correspond to higher risk levels and do not address cumulative risk from exposure to multiple chemicals.
Although exceeding an MCL does not in itself trigger a removal action, once the Agency has determined the need for a removal action under CERCLA, typically MCLs should be attained to the extent practicable during the removal action considering the exigencies of the situation. In determining whether ARARs are practicable, the Agency may consider appropriate factors including the urgency of the situation and the scope of the removal action to be taken. For further information on ARARs in the removal action process, please refer to the guidance titled, “Superfund Removal Procedures: Guidance on the Consideration of ARARs During Removal Actions” (USEPA, 1991). ) If a risk-based RML is lower than an MCL, the MCL is generally used as the removal level.
Calculated RMLs are not meant to define protective levels and are not de facto cleanup levels but are meant to help identify areas, contaminants, or conditions where a removal action may be appropriate. Thus, generic RMLs correspond to the higher risk levels of approximately 10-4 and/or a Hazard Quotient of up to 3 for long-term exposure to individual chemicals at a site. A 10-4 risk level corresponds to the upper-end of EPA’s generally acceptable cancer risk range of 10-6 to 10-4 as discussed in the National Contingency Plan (NCP), 40 CFR 300.430. The NCP gives no analogous recommended range for non-carcinogenic risks.
However, an HQ of 3 is generally considered a reasonable risk level for RMLs for non-carcinogenic chemicals based on the discussion of uncertainty included in EPA’s definition of the non-carcinogenic Reference Dose (RfD) and Reference Concentration (RfC). EPA defines the RfD and RfC as:
“…an estimate (with uncertainty spanning perhaps an order of magnitude) of daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime...”
It is unknown for any chemical where the RfD/RfC may fall within the order of magnitude range of uncertainty. As a science policy choice, OLEM places the RfD/RfC in the middle of a factor of ten uncertainty range (i.e., 0.1 to 10) to provide boundaries to aid in defining a non-carcinogenic risk. As stated previously, action generally is not warranted at a site where the non-carcinogenic HQ is less than 1 (i.e., the exposure level is lower than the RfD/RfC); whereas action may be warranted where the non-carcinogenic HQ exceeds 1. Therefore, using an HQ less than 1 to calculate the RMLs does not align with the intended purpose of these values; and an HQ of 10 is unacceptable as this risk level may be approaching the adverse health effect levels of some chemicals. Thus, as a science policy choice to aid in prioritizing actions that may warrant the use of removal authority, OLEM selects an HQ of 3 as the upper, target risk level for calculating non-cancer RMLs.
However, the generic RML tables provide risk-based values corresponding to an HQ of 1 and 3 as there may be site-specific and/or chemical specific circumstances where an HQ less than 3 may be more appropriate for calculating RMLs. For example, RMLs corresponding to an HQ of 1 may be more appropriate for those sites where multiple chemicals are present that have RfDs or RfCs based on the same toxic endpoint or where the toxicity of a chemical is such that exceeding the RfD/RfC, even slightly, warrants particular concern. Consultation with an experienced EPA risk assessor is recommended to perform these evaluations.
In addition to providing the user with a table of generic, risk-based RMLs, this website links to the Regional Screening Levels (RSLs) generic tables and the calculation tool which allows users to modify the standardized, default parameters to calculate site-specific RSLs and RMLs. The generic RSL table corresponds to risk levels of approximately 10-6 and/or an HQ of 1 for long-term exposure to individual chemicals at a site. It is recommended that if an OSC or other site manager is calculating site specific RSLs or RMLs that a Regional risk assessor be consulted for assistance.
A risk assessor or risk manager may want to calculate RMLs based on short-term exposures. In this case, they would use the calculation tool but reduce the 25- or 30-year default value for exposure duration and replace the toxicity criteria and risk levels used for chronic exposures with values that are appropriate for the scenario-specific exposure duration selected.
Whether the user relies on generic RMLs or chooses to calculate site-specific RMLs, it is important to clearly demonstrate the equations and exposure parameters used in deriving RMLs at a site. A discussion of the assumptions used in the RML calculations should be included in the decision document where site-specific RMLs are presented.
Comparison of site concentrations to RMLs is only one factor used in determining the need for a removal action at a site. While EPA's expectation is that removal actions are generally justifiable above the RML, EPA has the flexibility to determine that case-specific conditions do not warrant a removal action. For example, site-specific background or incomplete exposure pathways might indicate that a removal is not necessary, or that another mechanism for addressing the site is more appropriate. In such cases, EPA might refer the site for remedial action, or to a state or other authority, or might choose some other means of addressing the site.
Conversely, these generic values cannot account for all chemicals, exposure pathways or receptors that may be present at a site. Thus, a significant health threat may exist at a site even if none of the substances detected exceeds its numeric RML. Flexibility is provided so that additional site-specific factors can be considered such as: threat of fire or explosion, exposures from other sources, exposures to multiple contaminants, population sensitivity, the finding of a public health hazard by the Agency for Toxic Substances and Disease Registry (ATSDR), and other factors not directly related to the contaminant concentration. Therefore, a removal action may be initiated if the risk/hazard at a site has been analyzed in detail and the analysis indicates that a serious risk/hazard is present due to site-specific factors.
It is always recommended that if an OSC or other risk manager has questions about RMLs, RSLs, and/or clean up levels that a Regional risk assessor be consulted for assistance.
- Note: Radionuclide RMLs are not provided or addressed on this website, more information is available at EPA’s Preliminary Remediation Goals for Radionuclides.
- Note: No consideration is given to ecological effects in the values presented in this database tool. Therefore, ecological risk may need to be addressed separately when a removal action based on these RMLs is being considered.
- Note: For air as an exposure medium, the duration of the exposure and the level of exposure may dictate the use of very short duration (acute) air benchmarks (TEELs, AEGLs, ERPGs) over RMLs. Due to the different types of air release scenarios an OSC may encounter, and the difficulties inherent in choosing among these multiple criteria, OSCs and other risk managers should consult their Regional risk assessors and/or public health officials for help in selecting the most appropriate comparison values for their site-specific circumstances. Please see the FAQ page for further information.