United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
Washington, D.C. 20460
Publication 9285.7-01 BFS
December 1991
Risk Assessment Guidance
for Superfund: Volume I --
Human Health Evaluation
Manual (Part B)
Office of Emergency and Remedial Response
Hazardous Site Evaluation Division, OS-230
Quick Reference Fact Sheet
The overarching mandate of the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) program is to protect human health and the environment from current and potential threats posed
by uncontrolled releases of hazardous substances. To help meet this mandate, the U.S. Environmental
Protection Agency's (EPA's) Office of Emergency and Remedial Response (OERR) has developed a human
health evaluation process as part of its remedial response program. EPA's Human Health Evaluation Manual
describes the process of gathering information and assessing the risk to human health, and together • ''h the
Environmental Evaluation Manual comprise a two-volume set (Volumes I and II, respectively) called Risk
Assessment Guidance for Superfund (RAGS). RAGS replaces two previous EPA guidance documents: the
Superfund Public Health Evaluation Manual (SPHEM; 1986) and the Draft Endangerment Assessment Handbook
(1985).
The Human Health Evaluation Manual (HHEM) has three main parts: Part A, which discusses the baseline
risk assessment; Part B, Development of Risk-based Preliminary Remediation Goals; and Part C, Risk Evaluation
of Remedial Alternatives. Part A contains much of the detailed information concerning risk assessment
activities (e.g., data evaluation, exposure assessment, toxicity assessment, risk characterization) and is necessary
background for much of Part B.
This fact sheet is designed to introduce remedial project managers (RPMs) and other personnel to the
information that is available in RAGS/HHEM Part B on developing risk-based preliminary remediation goals
(PRGs). Development of PRGs is part of the overall remedial investigation/feasibility study (RI/FS) process
as described in Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA (EPA
1988).
OVERVIEW OF PART B:
DEVELOPMENT OF RISK-BASED
PRGs
What is Part B?
Part B is designed to assist risk assessors, RPMs,
and the rest of the remedial design staff in
developing risk-based PRGs for chemicals of
concern at CERCLA sites. It provides guidance
on using standard default equations, EPA toxicity
values, and exposure information to derive risk-
based PRGs. Part B addresses risk-based PRGs
for both non-radioactive and radioactive
contaminants; it does not address ecological
effects.
Part B provides a summary discussion of applicable
or relevant and appropriate requirements
(ARARs). Also included is a discussion of the
nine criteria developed in the National Oil and
Hazardous Substances Pollution Contingency Plan
(NCP) for use in the remedy selection process.
These nine criteria are listed in Highlight 1.
The goal of Part B is to provide guidance on
developing PRGs that will comply with the two
"threshold criteria": (1) overall protection of
human health and the environment; and (2)
compliance with ARARs.
What are PRGs?
PRGs are initial clean-up goals for individual
chemicals given specific medium and iand-usc
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Highlight 1
NINE EVALUATION CRITERIA
(40 CFR 300.430(e)(9)(iii))
Threshold Criteria:
• Overall Protection of Human Health
and the Er.>, jnment
• Compliance with ARARs
Balancing Criteria:
• Long-term Effectiveness and
- Permanence
• Reduction of Toxicity, Mobility, and
Volume Through Treatment
• Short-term Effectiveness
• Implementability
• Cost
Modifying Criteria:
• State Acceptance
• Community Acceptance
combinations at CERCLA sites. There are two
general types of PRGs: (1) concentrations based
on ARARs and (2) concentrations based on risk
assessment. ARARs include concentration limits
set by other environmental regulations (e.g., non-
zero maximum contaminant level goals [MCLGsj
set under the Safe Drinking Water Act). The
second source for PRGs, and the focus of Part B,
is risk-based calculations using carcinogenic and
noncarcinogenic toxicity values under specific
exposure conditions.
How do Part B and PRGs assist in the RI/FS
process?
Part B provides guidance on calculating initial
target concentrations for site engineers to use
during the analysis and screening of remedial
alternatives. When used early in the decision-
making process (before the RI/FS and the baseline
risk assessment are completed), the standard
default equations and other information in Part B
can significantly streamline and increase
consistency in the remedy selection process
between sites.
Who needs to implement the guidance in Part B?
What does the RPM need to do?
Risk assessors will be the primary users of Part B.
However, RPMs and the rest of the remedial
design staff should familiarize themselves with the
information contained in Part B. The RPM needs
to assist in the direction and development of risk-
based PRGs to ensure efficient and focused site
remediation. The RPM will, need to consult the
available technical resources (e.g., lexicologists) at
the state or regional levels, and will need to
facilitate communication between the risk assessor,
the ARARs coordinator, and the site engineer(s).
DEVELOPING PRGs
When are risk-based PRGs developed?
While initially developed during the RI/FS scoping
phase using readily available information, risk-
based PRGs generally are modified as needed at
the end of the RI or during the FS based on site-
specific data from the baseline risk assessment.
Remediation levels ultimately are selected based
on evaluation of the nine criteria in the NCP and
made final in the Record of Decision (ROD).
What are "standard default equations"?
The standard default equations in Part B
incorporate certain human exposure and risk
assumptions and are used to calculate risk-based
PRGs for residential and commercial/industrial
land uses. Part B presents the standard equations
in two forms: (1) full equations, with all variables
and constants identified, and (2) reduced
equations. When site-specific information is not
readily available, the reduced equations can be
used to develop risk-based PRGs. If exposure
pathways other than those addressed by the default
equations are identified for particular media, then
site-specific equations can be derived using the full
equations. See Highlight 2 for an example of a
reduced equation from Part B.
What major assumptions are made in the standard
default equations?
The standard default equations are based on
protective, commonly used exposure (and other)
assumptions that are useful for achieving
consistency in goal-setting across sites, and for
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Highlight 2
EXAMPLE OF A REDUCED EQUATION:
RESIDENTIAL WATER-
CARCINOGENIC EFFECTS
Risk-based PRO
(mg/L; target
risk = 10-*)
where:
1.7 x 1Q-*
2(SF0) + 7J(SF.)
oral slope factor in (mg/kg-
day)'1
inhalation slope factor in
(mg/kg-day)-1
streamlining the RI/FS process. Note, however,
that they do not necessarily reflect site-specific
conditions. When risk-based PRGs are to be
calculated based on site-specific conditions, the
risk assessor must modify factors in the full
equations and/or develop additional ones.
For carcinogenic effects, a concentration is
calculated at an incremental risk of 10"6 for an
individual developing cancer over the course of a
lifetime as a result of exposure to the potential
carcinogen from all significant exposure pathways
for a given medium (e.g., water ingestion). In the
case of noncarcinogenic effects, a concentration is
calculated at a hazard index (HI) of 1, which is the
level of exposure to a chemical below which it is
unlikely for even sensitive populations to
experience adverse health effects.
All standard reduced equations incorporate
pathway-specific default exposure factors that
generally reflect reasonable maximum exposure
(RME) conditions. As detailed in Chapter 8 of
RAGS/HHEM Part A, RME risks from one
pathway should be combined with RME risks from
another pathway only if warranted by specific
circumstances. Therefore, if risk-based PRGs are
developed for both the water and the soil, the risk
assessor must determine if it is appropriate to use
RME assumptions for both.pathways.
What land uses, media, and exposure pathways are
addressed by the standard equations?
The equations contained in Part B address
residential and commercial/industrial land uses.
For residential land use, the equations address the
following exposure pathways and media:
• ingestion of contaminants and inhalation
of volatile contaminants in ground water
and surface water used as a domestic
water supply;
• ingestion of contaminants in soil; and
• direct external exposure to gamma-
emitting radionuclides in soil.
For commercial/industrial land use, the equations
address the following exposure pathways and
media:
• ingestion of soil contaminants, inhalation
of volatile contaminants from soil, and
inhalation of contaminated particulates
released to air from soil; and
• direct external exposure to gamma-
emitting radionuclides in soil.
What inputs are required to use the standard
equations?
All of the standard reduced equations require at
least one toxicity input (e.g., an oral slope factor
for carcinogenic effects from residential soil).
Most of the equations, such as the one in
Highlight 2, require only toxicity inputs, while
other equations require several chemical-specific
inputs. As more data are gathered during the
RI/FS, the full equations in Part B can be
modified—or other equations can be
developed—using site-specific exposure inputs.
How should PRGs be presented?
Highlight 3 presents an example of a useful format
for presenting PRGs. A table such as this, plus
supporting documentation, should be distributed
among all members of the remedial design staff
(e.g., ARARs coordinators, site engineers,
analytical chemists, hydrogeologists). Eventually,
PRGs—perhaps modified using the baseline risk
assessment or other information—should be
presented in the RI/FS report. Final goals,
however, are presented in the ROD.
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Highlight 3
EXAMPLE OF A PRESENTATION OF PRGs DEVELOPED DURING SCOPING3
Site: XYZCo.
Medium: Ground Water
Exposure Routes: Water Ingestion, Inhalation of Volatiles
Location: Anytown, Anystate
Land Use: Residential
Chemical
Benzene
Carbon Tetrachloride
o-Chlorotoiuene
Ethylbenzene
Hexane
Isophorone
Triallate
1,1,2-Trichloroethane
Vinyl chloride
Risk-based PRGs
(mg/L)b
10'6
—
—
—
—
—
0.022*
—
—
—
HQ = 1
—
—
0.73
—
0.33
7.3
0.47
—
—
ARAR-based PRG
Type
MCL
MCL
—
MCLG
MCL
_
—
—
MCLG
MCL
MCL
Concentration (mg/L)
0.005
0.005
—
0.7**
0.7
—
—
—
0.003**
0.005
0.002
a All information in this example is for illustration purposes only.
b These concentrations were calculated using the standard default equations in Chapter 3 of Part B.
Of the two potential risk-based PRGs tor the chemical, this concentration was selected.
Of the two potential ARAR-based PRGs for the chemical, this concentration was selected.
APPENDICES
Appendix A: Illustrations of Chemicals that
"Limit" Remediation. In many cases, one or wo
chemicals will drive the cleanup at a site, rendering
the cumulative medium or site risk approximately
equal to the risk associated with these "limiting
chemicals". Appendix A provides illustrations of
remedial alternatives where one or more chemicals
"limit" remediation and therefore represent a major
portion of the residual risk.
Appendix B: Risk Equations for Individual
Exposure Pathways. Appendix B lists equations
for medium-specific exposure pathways to help the
risk assessor derive site-specific equations where
needed. These individual risk equations can be
used and rearranged to derive full risk equations
required for calculating risk-based PRGs.
NEED MORE HELP?
Regional Toxics Integration Coordinators
(Highlight 4) can provide additional information
concerning development of risk-based PRGs.
Additional information also can be found in the
documents listed in Highlight 5.
EPA staff can obtain copies of Part B, this fact
sheet, and other documents by calling EPA's
Center for Environmental Research Information at
FTS 684-7562 (513/569-7652). Others should call
the National Technical Information Service at
800/336-4700 (703/487-4650 in the Washington, DC
area).
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Highlight 4
SUPERFUND REGIONAL TOXICS INTEGRATION COORDINATORS
EPA Region
Toxics Integration Coordinator
Telephone
10
Sarah Levinson
John F. Kennedy Federal Bldg.
Boston, MA 02203
Peter Grevatt
26 Federal Plaza
New York, NY 10278
Dr. Richard Brunker
841 Chestnut Street
Philadelphia, PA 19107
Dr. Elmer Akin
345 Courtland Street, NE
Atlanta, GA 30365
Erin Moran
230 S. Dearborn Street
Chicago, IL 60604
Jon Rauscher
First Interstate Bank Tower
1445 Ross Avenue
Dallas, TX 75202
Dave Crawford
726 Minnesota Avenue
Kansas City, KS 66101
Chris Weis
999 18th Street, Suite 500
Denver, CO 80202
Dan Stralka
75 Hawthorne Street
San Francisco, CA 94105
Pat Cirone
1200 6th Avenue
-Seattle, WA 98101
FTS 833-1504
617/223-5504
FTS 264-6323
212/264-6323
FTS 597-0804
215/597-0804
FTS 257-1586
404/347-1586
FTS 353-1420
312/353-1420
FTS 255-2198
214/655-2198
FTS 276-7702
913/551-7702
FTS 330-7655
303/294-7655
FTS 484-2310
415/744-2310
FTS 399-1597
206/553-1597
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Highlight 5
OTHER USEFUL GUIDANCE DOCUMENTS
Risk Assessment Guidance for Superfund: Volume I - Human Health Evaluation Manual (Part A, Baseline Risk
Assessment) (1989. EPA/540/1-90/002) contains background information and is particularly relevant for developing
exposure and toxicity assessments that are required when refining chemical-specific risk-based concentrations, and
accounting for site-specific factors such as multiple exposure pathways.
Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA (1988, EPA/540/G-
89/004, OSWER Directive No. 9355.3-01) presents detailed information about implementing the RI/FS and
general information on the use of risk-based factors and ARARs in the context of the RI/FS.
Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites (1988, EPA/540/G-88/003,
OSWER Directive No. 9283.1-2) details some of the key issues in development, evaluation, and selection of
ground-water remedial actions at CERCLA sites.
CERCLA Compliance with Other' ins Manuals (Part 1,1988, EPA/540/G-89/006, OSWER Directive 9234.1-01;
and Part II, 1989, EPA/G-89/009, OSWER Directive 9234.1-02) provide guidance for complying with ARARs.
Part I addresses the Resource Conservation and Recovery Act (RCRA), the Clean Water Act (CWA), and the
Safe Drinking Water Act (SDWA); Part II addresses the Clean Air Act (CAA), other federal statutes, and state
requirements.
Interim Final Guidance on Preparing Superfund Decision Documents (1989, OSWER Directive 9355.3-02)
provides guidance that: (1) presents standard formats for documenting CERCLA remedial action decisions; (2)
clarifies the roles and responsibilities of the EPA, states, and other federal agencies in developing and issuing
decision documents; and (3) explains how to address changes made to proposed and selected remedies.
Catalog of Superfund Program Publications, Chapter 5 (1990, OSWER Directive 9200.7-02A) lists all ARARs
guidance documents that have been issued by EPA, shown in order of date of issuance.
Guidance for Data Useability in Risk Assessment (1990, EPA/540/G-90/008, OSWER Directive 9285.7-05)
provides guidance on how to obtain a minimum level of quality for all environmental analytical data required for
CERCLA risk assessments. It can assist with determining sample quantitation limits (SQLs) for chemical-specific
analyses.
Guidance on Remedial Actions for Superfund Sites with PCB Contamination (1990, EPA/540/G-90/007, OSWER
Directive 9355.4-01) describes the recommended approach for evaluating and remediating CERCLA sites that
have PCB contamination.
Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions (1991, OSWER Directive 9355.0-
30) provides clarification on the role of the baseline risk assessment in developing and selecting CERCLA
remedial actions.
Risk Assessment Guidance for Superfund, Vol. 1, Human Health Evaluation Manual, Supplemental Guidance:
"Standard Default Exposure Factors" (1991, OSWER Directive 9285.6-03) describes many of the default exposure
assumptions used in Part B. Additional default exposure assumptions also are addressed.
Conducting Remedial Investigations/Feasibility Studies for CERCLA Municipal Landfill Sties (1991, EPA/540/P-
91/001, OSWER Directive 9355.3-11) offers guidance on how to streamline both the RI/FS and the selection
of a remedy for municipal landfills.
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