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% UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
8 WASHINGTON, D.C. 20460
JUN - 320H
OFFICE OF
SOLID WASTE AND
EMERGENCY RESPONSE
OSWER 9285.6-20
MEMORANDUM
SUBJECT: Distribution of the "Radiation Risk Assessment At CERCLA Sites: Q&A'
FROM: Ljv-Robin H. Richardson, Acting Director (AL^f
T\ Office of Superfund Remediation and Techirology Innovation
TO: Superfund National Policy Managers, Regions 1-10
Purpose
The purpose of this memorandum is to transmit the final guidance "Radiation Risk Assessment At
CERCLA Sites: Q&A." This new final guidance will replace a previous version of the "Radiation Risk
Assessment At CERCLA Sites: Q&A" issued in 1999.
Role of the Guidance
The Office of Superfund Remediation Technology Innovation (OSRTI) developed this document to
present an overview of current EPA guidance for risk assessment and related topics for radioactively
contaminated Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
remedial sites. It provides answers to several commonly asked questions regarding risk assessments at
radioactively contaminated CERCLA remedial sites.1 The purpose of this document is to provide
answers to commonly asked questions regarding risk assessment for radioactive contamination, describe
how to analyze levels of radioactive contamination and explain how to assess the risks from radioactive
1 The document transmitted by this memorandum provides guidance on risk assessment under CERCLA and is consistent with the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP). It does not alter the NCP's general expectations for
remedial actions, such as those regarding treatment of principal threat waste and the use of containment and institutional controls for
low-level threat waste. Consistent with CERCLA and the NCP, remedial actions need to attain or waive Applicable or Relevant and
Appropriate Requirements (ARARs); potential ARARs for contaminated ground water at radiation sites typically include Maximum
Contaminant Levels (MCLs) or non-zero Maximum Contaminant Level Goals (MCLGs) established under the Safe Drinking Water
Act.
This document provides guidance to U.S. Environmental Protection Agency (EPA) staff on how to conduct risk
assessments for radioactively contaminated CERCLA sites. The guidance is designed to be consistent with EPA's national guidance
on these issues. This guidance does not, however, substitute for EPA's statutes or regulations, nor is it a regulation itself. Thus, it
cannot impose legally binding requirements on EPA, states, or the regulated community, and may not apply to a particular situation
based upon the circumstances. EPA may change this guidance in the future, as appropriate.
Internet Address (URL) http://www.epa.gov
Recycled/Recyclable Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper
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contamination as part of a remedy for a radioactively contaminated CERCLA remedial site. This
guidance is intended to help health physicists, risk assessors, remedial project managers, and others
involved with risk assessment and decision making at CERCLA remedial sites with radioactive
contamination.
Background
The EPA issued guidance entitled "Establishment of Cleanup Levels for CERCLA Sites with
Radioactive Contamination" (OSWERNo. 9200.4-18, August 22, 1997). This 1997 guidance provided
clarification on establishing protective cleanup levels for radioactive contamination at CERCLA sites.
The guidance reiterated that cleanups of radionuclides are governed by the risk range for all carcinogens
established in the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) when
Applicable or Relevant and Appropriate Requirements (ARARs) are not available or are not sufficiently
protective. Cleanups generally should achieve a level of risk within the 10"4 to 10"6 carcinogenic risk
range based on the reasonable maximum exposure for an individual. In calculating cleanup levels, one
should include exposures from all potential pathways, and through all media (e.g., soil, ground water,
surface water, sediment, air, structures, etc.) The guidance also provides a listing of radiation standards
that are likely to be used as ARARs to establish cleanup levels or to conduct remedial actions.
The EPA previously issued "Radiation Risk Assessment At CERCLA Sites: Q&A" (OSWER No.
9200.4-3 IP, December 1999). The 1999 Risk Q&A provided an overview of the then current EPA
guidance for risk assessment and related topics for radioactively contaminated CERCLA sites. This
guidance provided answers to several commonly asked questions regarding risk assessments at
radioactively contaminated CERCLA sites. In addition, it recommended that dose assessments only be
conducted under CERCLA where necessary to demonstrate compliance with ARARs. Today's Risk
Q&A guidance updates the 1999 version of the Risk Q&A by summarizing and citing guidance that was
developed after the 1999 version. This new guidance explains how to convert radon measurements to
demonstrate compliance with indoor radon standards that are potential ARARs using a methodology
based on international guidance, and it changes the Superfund recommendation on what is considered a
protective dose-based ARAR from 15 to 12 millirem per year (mrem/yr). The new recommendation of
12 mrem/yr regarding what dose-based ARARs are protective is based on using an updated risk
assessment to achieve the same 3 x 10"4 cancer risk as the previous recommendation using 15 mrem/yr.
The Radiation Risk Q&A guidance is part of a continuing effort by OSRTI to provide updated guidance
for addressing radioactively contaminated remedial Superfund sites consistent with our guidance for
addressing chemically contaminated sites (while accounting for the technical differences between
radionuclides and chemicals). OSRTI intends for this effort to facilitate remedial cleanups that are
consistent with the NCP at radioactively contaminated sites and to incorporate new information based on
improvements to the Superfund program.
Implementation
For questions regarding radiation site policy and guidance for CERCLA cleanup actions, readers are
referred to the Superfund Radiation Webpage at
http://www.epa.gov/superfund/health/contaminants/radiation/index.htm. The subject matter specialist
for this guidance is Stuart Walker of OSRTI. He can be reached by e-mail at walker.stuart@epa.gov or
by telephone at (703) 603-8748.
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Attachment
cc: Mathy Stanislaus, OSWER
Nitin Natarajan, OSWER
Barry Breen, OSWER
Lawrence Stanton, OSWER/OEM
Barnes Johnson, OSWER/ORCR
David Lloyd, OSWER/OBLR
Reggie Cheatham, OSWER/FFRRO
Carolyn Hoskinson, OSWER/OUST
Rafael DeLeon, OECA/OSRE
David Kling, OECA/FFEO
John Michaud, OGC/SWERLO
Mike Flynn, OAR/ORIA
OSRTI Managers
Regional Superfund Branch Chiefs, Regions 1-10
Lisa Price, Superfund Lead Region Coordinator, Region 6
NARPM Co-Chairs
OSRTI Document Coordinator
3
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(sszy
United States Office of Superfund
Environmental Protection Agency Remediation and
Technology Innovation
Directive 9200.4-40
E PA 540-R-012-13
May 2014
Radiation Risk Assessment
At CERCLA Sites: Q & A
NOTICE: The policies set out in this document are intended solely as guidance to U.S. Environmental Protection Agency (EPA)
personnel; they are not final EPA actions and do not constitute rulemaking. These policies are not intended, nor can they be
relied upon, to create any rights enforceable by any party in litigation with the United States. EPA officials may decide to follow
the guidance provided in this document, or to act at variance with the guidance, based on analysis of specific-site
circumstances. EPA also reserves the right to change the guidance at any time without public notice.
Table of Contents Page
Introduction 2
Purpose 4
I. Data Collection and Evaluation 4
Q1. What strategy and key information should be considered during the initial planning stage for radiological data collection ? 4
Q2. How should a list of radionuclides of concern be developed? 6
Q3. What criteria should be used to determine areas of radioactive contamination or radioactivity releases? 8
Q4. How should the areal extent and depth of contamination be determined? 9
Q5. What field radiation survey instruments should be used and what are their lower limits of detection ? 9
Q6. What sample measurement units for radiation risk assessment are typically used? 10
Q7. What sample measurement units for remedial action evaluation may be used? 10
Q8. Are radionuclides included in EPA's Contract Laboratory Program (CLP)? If not, where should comparable radioanalytical
services be obtained? 11
Q9. How can I decide if the data collected are complete and of good quality? 12
II. Exposure Assessment 12
Q10. For CERCLA risk assessments, is it appropriate to use guidance developed by other Federal, State or Tribal Agencies or
by International or National organizations? 12
Q11. How does the exposure assessment for radionuclides differ from that for chemicals? 12
Q12. Can exposure pathways be added or deleted based on site-specific conditions? 13
Q13. How should radioactive decay products be addressed? 16
Q14. To what extent should generic and site-specific factors and parameter values be used in exposure assessments? 16
Q15. How should exposure point concentrations be determined? 16
Q16. What calculation methods or multimedia radionuclide transport and exposure models are recommended by EPA for
Superfund risk assessments? 17
Q17. How should Radon-222 (radon) and Radon-220 (thoron) exposures and risks be evaluated? 18
Q18. How long a time period should be considered for possible future exposures? 19
Q19. How should the results of the exposure assessment for radionuclides be presented? 19
III. Toxicity Assessm ent 20
Q20. What is the mechanism of radiation damage? 20
Q21. What are radionuclide slope factors? 20
Q22. What are radionuclide dose conversion factors? 21
Q23. What is dose equivalent, effective dose equivalent, and related quantities? 21
Q24. What is the critical organ approach to dose limitation? 22
Q25. How should radionuclide slope factors and dose conversion factors be used? 22
Q26. In addition to cancer, should the potential teratogenic and genetic effects of radiation exposures be considered? 23
Q27. Should chemical toxicity of radionuclides be considered? 25
IV. Risk Characterization 25
Q28. How should radionuclide risks be estimated? 25
Q29. Should radionuclide and chemical risks be combined? 25
Q30. How should risk characterization results for radionuclides be presented? 26
Q31. Should the collective risk to populations be estimated along with that to individual receptors? 26
Q32. How should uncertainty in estimates of radiation risk be addressed in the risk characterization report? 26
Q33. When should a dose assessment be performed 27
Q34 What is the upper end of the risk range with respect to radionuclides 27
Q35 Should the ARAR protectiveness criteria evaluation recommendation be changed from 15 mrem/yr to reflect the updates to
Radiation risk estimates contained in Federal Guidance Report 13? 28
Q36 Should dose recommendations from other federal be used to assess risk or establish cleanup levels? 28
Q37. How and when should exposure rate be used to estimate radionuclide risks? 29
Q38. What radiation standards may be applicable or relevant and appropriate requirements (ARARs) ? 30
V. Ecological Assessments 30
Q39. What guidance is available for conducting ecological risk assessments? 30
VI. Background Radiation 31
Q40. How should background levels of radiation be addressed? 31
Where to go for Further Information 33
References 34
Appendix A: EPA's Recommended Guidance for Radiation Risk Assessment at CERCLA Remedial Sites 43
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INTRODUCTION
Some sites on the U.S. Environmental Protection Agency's (EPA) National Priorities List (NPL)
are radioactively contaminated. To assist in the evaluation and cleanup of these sites under the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or
Superfund), EPA's Office of Superfund Remediation and Technology Innovation (OSRTI) has
developed guidance for conducting radiation risk assessments during the remedial
investigation/feasibility study (RI/FS) process of the CERCLA remedial program. This guidance
may also be useful for non-time critical removal actions.
This guidance does not address emergency or time-critical removals conducted under CERCLA.
Also, this guidance does not address how other cleanup programs (those not conducted under
CERCLA authority) should be implemented. Persons conducting radiation risk assessments at
sites using these other authorities should consult the regulations and guidance that are appropriate
for that authority.
EPA has developed a number of guidance for the CERCLA remedial program. Users of this
guidance should prior to conducting any CERCLA radiation risk assessments at remedial sites be
familiar with the following guidance specific to radiation risk assessment for the CERCLA
remedial program and how they relate to one another:
The Preliminary Remediation Goals (PRGs) for Radionuclides electronic calculator, known
as the Rad PRG calculator (U.S. EPA 2002a).
The Building Preliminary Remediation Goals for Radionuclides (BPRG) electronic calculator
(U.S. EPA 2007).
The Radionuclide Outdoor Surfaces Preliminary Remediation Goals (SPRG) electronic
calculator (U.S. EPA 2009a).
Soil Screening Guidance for Radionuclides contains both a User's Guide and Technical
Background Document, (known as the Rad SSG documents) that provide information on soil
screening for radionuclides at CERCLA sites (U.S. EPA 2000a, 2000b). The risk assessment
equations and the soil screening levels (SSLs) in this guidance have been superseded by the
Rad PRG calculator.
ARAR Dose Compliance Concentrations for Radionuclides (DCC) electronic calculator (U.S.
EPA 2004a).
ARAR Dose Compliance Concentrations for Radionuclides in Buildings (BDCC) electronic
calculator (U.S. EPA 2010a), known as the BDCC calculator.
ARAR Radionuclide Outdoor Surfaces Dose Compliance Concentrations for Radionuclides
(SDCC) electronic calculator (U.S. EPA 2010b), known as the SDCC calculator.
Chapter 10, "Radiation Risk Assessment Guidance" of RAGS Part A (U.S. EPA 1989a).
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Chapter 4, "Risk-based PRGs for Radioactive Contaminants," of RAGS Part B (U.S. EPA
1991a).
Appendix D, "Radiation Remediation Technologies," of RAGS Part C (U.S. EPA 1991b).
RAGS Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessments
(U.S. EPA 1998a).
Superfund Radiation Risk Assessment and How You Can Help: An Overview (U.S. EPA
2005a).
Appendix A "EPA's Recommended Guidance for Radiation Risk Assessment at CERCLA
Remedial Sites," which are the last two pages of this guidance, has a short overview of these
guidance for radiation risk assessment at CERCLA remedial sites. In addition to PRG and DCC
calculators, Soil Screening Guidance for Radionuclides (Rad SSG) documents, and RAGS,
EPA has published several other guidance documents and OSWER directives concerning risk
assessment methods for radioactive and nonradioactive contaminants for remedial sites. The PRG
and DCC calculators are frequently updated. OSWER directives specific to radioactive
contaminants may be found at the Superfund Radiation website at
http://www.epa.gov/superfund/health/contaminants/radiation/index.htm.
Overall, the process for assessing radionuclide exposures and radiation risks at remedial sites for
humans that is presented in the PRG and DCC calculators, Rad SSG documents, RAGS, and in
supplemental guidance documents parallels the process for assessing risks from chemical
exposures (exposure assessment, toxicity assessment, and risk characterization). Both types of
assessments follow the same evaluation process, consider similar exposure scenarios and
pathways (except the external "direct exposure" pathway, which is unique to radiation and is
included in the PRG and DCC calculators [EPA 2002a, 2004a, 2007, 2009a, 2010a, and 2010b];
and the dermal exposure pathway, which is not a significant contributor to radiological risk and so
is not included in the current PRG and DCC calculators); determine exposure point
concentrations; and provide estimates of cancer risks to humans.
However, several aspects of risk assessment for radioactive contaminants differ substantially
from those considered for chemical contaminants. Occasionally these differencesin
measurement units, exposure terms and concepts, field and laboratory procedures and detection
limits, and toxicity criteria, among othershave led to questions concerning the Agency's
recommended approach for addressing radionuclide contamination and risk and the remediation
of CERCLA radiation sites.
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PURPOSE
OSRTI has prepared this document to provide answers to questions regarding risk assessments at
radioactively contaminated CERCLA remedial action sites raised by Remedial Project Managers
(RPMs), risk assessors, federal, state and local agencies, potentially responsible parties (PRPs),
and contractors. These questions and answers supplement the Frequently Asked Questions (FAQs)
that accompany the remedial program's on-line calculators (see http://epa-
prgs.ornl.gov/radionuclides/faq.htmn. This document supersedes an earlier version issued in 1999
(EPA 1999a). Its purpose is to provide an overview of current EPA guidance for risk assessment
and related topics for radioactively contaminated CERCLA remedial sites.
The questions and answers (Q&A) that follow are presented in sections corresponding to the four
basic steps in the CERCLA risk assessment process:
1. Data Collection and Evaluation
2. Exposure Assessment
3. Toxicity Assessment
4. Risk Characterization
I. DATA COLLECTION AND EVALUATION
Ql. What strategy and key information should be considered during the initial
planning stage for radiological data collection?
A. The data quality objectives (DQO) process is an important tool for project managers and
planners to determine the types, quantity, and quality of data needed to support decisions.
Detailed guidance on the DQO process can be found in Guidance for the Data Quality
Objectives Process (U.S. EPA 1994a), Data Quality Objectives for Superfund (U.S. EPA
1993 a), and Uniform Federal Policy for Implementing Environmental Quality Systems:
Evaluating, Assessing, and Documenting Environmental Data Collection/Use and
Technology Programs (U.S. EPA 2005b). Additional guidance on the application of this
process at radiation sites can be found in the Soil Screening Guidance for Radionuclides
(Rad SSG) documents which provide EPA's recommended guidance on site-
characterization of radioactively contaminated sites and in Multi-Agency Radiation Survey
and Site Investigation Manual (MARS SIM) (U.S. EPA et al. Rev 1. 2000d), which
provides technical information on final status surveys of radioactively contaminated sites.
The DQO process outlined in these documents should be completed during the initial
planning stage for data collection.
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At a minimum, site characterization should evaluate the following key information and
considerations:
S Review of the site history and records collected during the preliminary assessment
and site inspection (PA/SI), considering:
Past site operations
Types and quantities of radioactive material used or produced
Radioactive waste stream characteristics
Disposal practices and records
Previous radiological characterization data and/or environmental monitoring data
Physical site characteristics (hydrology, geology, meteorology, etc.)
Demography
Current and potential future land use
¦S Formulation of a conceptual site model to:
Identify radionuclides of concern
Identify the time period for assessment
Identify potentially contaminated environmental media
Identify likely release mechanisms, potential for migration and exposure pathways
Identify potential human and ecological receptors
Focus initial surveys and sampling and analysis plans
S Development of comprehensive sampling plans based on the conceptual site model
and available historical information to:
Confirm the identities of radionuclide contaminants
Confirm release mechanisms and exposure pathways
Measure or model exposure point concentrations and point exposure rate (as
appropriate for the type of radioactive decay)
Confirm human and ecological receptors including sensitive sub-populations
Specify cleanup levels or develop preliminary remediation goals
Establish DQOs
Figure 1 depicts typical conceptual site models for human health risk assessments at
CERCLA sites with radioactive contamination. The user guides of each of the PRG and
DCC calculators (EPA 2002a, 2004a, 2007, 2009a, 2010a, and 2010b) include guidance on
developing conceptual site models for the exposure routes addressed by each model. Also,
each of the illustrations in Figure 1 appears in the PRG and DCC user guides with
additional explanatory text and in a larger size that is more legible.
The Rad SSG documents provide EPA's recommended guidance on planning,
implementing, and evaluating radiological site characterization for surface and subsurface
soil. The Rad SSG documents are consistent with EPA's site characterization guidance for
chemicals.
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The Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) (U.S.
EPA et al. Rev 1. 2000d) provides guidance on planning, implementing, and evaluating
radiological final status site surveys for surface soil and buildings. Final status surveys
follow scoping, characterization, and any necessary remedial actions. Although this multi-
agency technical document is not a recommended guidance for CERCLA remedial sites, it
may provide useful information on final status surveys to demonstrate compliance with
dose-based or risk-based criteria.
Q2. How should a list of radionuclides of concern be developed?
A. When developing a list of potential contaminants of concern, the list should initially be
developed to be as inclusive of potential contaminants as possible. As more information
and data are collected and evaluated, it may be appropriate to reduce the number of
contaminants on the list to include only those that are of concern based on potential
exposure pathways and the toxicity of site contaminants. An initial list of radionuclides of
potential concern should be based on a review of previous site operations, including
disposal, that contributed to the current levels of contamination as well as the conceptual
site model. As a first consideration, all radionuclides potentially used, produced or
disposed at the site should be included on the list. As appropriate, the list should also
include all radioactive decay products that may have formed since disposal or termination
of operations. Radionuclides with short half-lives and no parent radionuclide to support
ingrowth may be considered for exclusion from the list if no slope factor was developed
for the radionuclide. However, careful consideration should be given to its initial and
current activity inventories, its radioactive half-life, and the time elapsed since the
contamination occurred to the present before a short-lived radionuclide is excluded from
the list.
Site characterization efforts should be directed to confirming or refuting the presence of
the radionuclides of concern in on-site sources and in environmental media
contaminated by releases migrating or being transported and dumped off-site. The
activity concentrations of radionuclides (and decay products, if appropriate) in each
medium should then be compared with site-specific background concentrations of those
radionuclides (i.e., radionuclide concentrations in environmental media not related to
site operations or releases), Preliminary Remediation Goals (PRGs), screening levels, or
potential remediation criteria (see Q3). Caution should be exercised in making these
comparisons, since radionuclide concentrations in environmental media may change
over time due to radioactive decay and ingrowth; therefore, consideration should be
given to the radioactive half-life of the radionuclides of concern and any decay products,
and the time period over which risks will be evaluated.
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Figure 1. Typical Conceptual Site Models for Humans
PRIMARY
RELEASE
MECHANISM
SECONDARY
RELEASE
MECHANISM
|receptor]
Resuspenslon
> And
Volatilization
B-
Radionuclide
Handling
Area
Release or
Spill
¦H Biota |-
Conceptual Site Model of Quantified Exposure Pathways for radionuclide PRGs.
Black lines are direct exposure routes.
Black dashed lines are direct and indirect exposure routes
Red lines are indirect exposure routes.
Route
Resident
Outdoor
Worker
Indoor
Worker
Worker
Farmer 1
Inhalation
Submersion
1 Exposure
1 Route
Resident
Outdoor
Worker
Indoor
Worker
Worker
Farmer
Ingestion
Inhalation
1 Exposure
1 Route
Resident
Outdoor
Worker
Indoor
Worker
Worker
Farmer
Ingestion
¦¦
Inhalation
External
Exposure
1 Exposure
1 Route
Resident
Outdoor
Worker
Indoor
Worker
Worker
Farmer
Produce
Poultry
Eggs
Beef
Milk
Pork
Fish
PRIMARY
SOURCES
PRIMARY
RELEASE
MECHANISM
SECONDARY
SOURCES
SECONDARY
RELEASE
MECHANISM
EXPOSURE
MEDIA
RECEPTOR
Indoor
Building
Materials
Breakdown
» of Building
Materials
Settled
Dust
3-D Sources
Conceptual Site Model of Quantified Exposure Pathways for radionuclide BPRGs.
Black lines are direct exposure routes.
Exposure
J Route
Resident
Indoor
Worker |
Indoor 1
Inhalation
9
Submersion
1 Exposure
I Route
Resident
Indoor
Worker
Indoor
Ingestion
Inhalation
Exposure
Route
Resident
indoor
Worker
indoor
External
Exposure
PRIMARY
SOURCES
PRIMARY
RELEASE
MECHANISM
SECONDARY
SOURCES
SECONDARY
RELEASE
MECHANISM
EXPOSURE
MEDIA
Hard
Outdoor
Surfaces
Breakdown
of Surface
Materials
Resusperision
-Wind
- Mechanical
Settled
Dust
U Exposure
Route
Resident
Indoor
Worker
Outdoor
Worker
Indoor 1
Composite
Worker
Ingestion
External
Exposure
3-D and 2-D Sources
| Exposure
| Route
Resident
Indoor
Worker
Outdoor
Worker
1 Indoor
Composite
Worker
External
Exposure
Conceptual Site Model of Quantified Exposure Pathways for radionuclide SPRGs.
Black lines are direct exposure routes.
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Q3. What criteria should be used to determine areas of radioactive contamination or
radioactivity releases?
During the site assessment phase, Section 7 of EPA's revised Hazard Ranking System
(HRS) (see Appendix A to 40 Code of Federal Regulations [CFR] Part 300) outlines the
methodology for evaluating radioactive releases and determining whether a radioactive
release is a high priority for the CERCLA remedial program.
During risk assessments, guidance for the measurement and evaluation of radiological
contaminants is provided in the Soil Screening Guidance for Radionuclides (Rad SSG)
documents (U.S. EPA 2000a, 2000b). The Rad SSG also provides guidance on the
determination of site-specific background levels for comparison to site measurements. The
Soil Screening Levels (SSLs) are not cleanup standards, but may be used to inform further
investigation at sites. The SSL risk assessment equations have been superseded by those in
the PRGs calculator where applicable or relevant and appropriate requirements (ARARs)
are not available or sufficiently protective; therefore, the PRG calculator should be used for
determining SSL risk based concentrations rather than the Rad SSG documents.
General guidance to inform the evaluation of radiological contamination is provided in the
following Agency documents:
Methods for Evaluating the Attainment of Cleanup StandardsVolume 1: Soil and
Soil Media (U.S. EPA 1989b)
Statistical Methods for Evaluating the Attainment of Cleanup StandardsVolume
2: Ground Water (U.S. EPA 1992a)
Statistical Methods for Evaluating the Attainment of Cleanup StandardsVolume
3: Reference-Based Standards for Soils and Solid Media (U.S. EPA 1992b)
Although these documents do not specifically address radionuclides, most of the
evaluation methods and tests provided in these documents should be applicable to both
radioactive and nonradioactive contaminants.
There are two general sampling approaches for determining what is contaminated for site
characterization or demonstrating compliance with cleanup levels; a not-to-exceed (NTE)
or area averaging (AA) approach. In general, the same sampling approach should be used
for both radionuclide and chemical contaminants in the same medium at the same site (e.g.,
soil, groundwater, surface water, air, or buildings) to facilitate a consistent approach for
addressing radionuclides and chemicals; generally, samples for both should be collocated
in the media of interest. For groundwater contamination, EPA's Superfund remedial
program generally recommends an NTE approach. EPA's Superfund remedial program
general practice has been to use the NTE approach for soil where residential land use is
assumed. If using the AA approach, users should ensure that exposure of receptors across
the exposure unit is random. However, exposure is not expected to be random under
residential land use because residents often engage in activities (such as gardening or
child's play) in specific portions of a yard. Under most residential situations and other non-
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random exposure situations, remediating with the AA approach may not be protective of
human receptors. When an AA approach is used, software such as Spatial Analysis and
Decision Assistance (SADA) (Stewart and Purucker 2011) may be useful for providing
visual representations of surface and subsurface contamination and plotting random
surface and subsurface sampling locations across a survey area.
Q4. How should the areal extent and depth of radioactivity contamination be determined?
A. As noted in Ql, a conceptual site model generally should be developed to identify
reasonable boundaries for investigating the nature and extent of contamination. General
guidance for site characterization activities is provided in Guidance for Conducting
Remedial Investigations and Feasibility Studies under CERCLA (U.S. EPA 1988a).
Guidance specifically for site characterization of radionuclides in soil is found in the Soil
Screening Guidance for Radionuclides documents (U.S. EPA 2000a, 2000b).
The choice of a specific method or methods to characterize remedial sites contaminated
with radioactive substances depends on several factors, including the decay characteristics
of the radionuclides potentially present at the site, suspected contamination patterns, and
activity concentrations. Ground-based or aerial radiation surveys are typically conducted
for gamma-emitting radionuclides in near-surface sources, in addition to surface sampling
to characterize the areal extent of contamination. Borehole logging for gamma emitters,
core sampling programs for radionuclides that emit alpha, beta or gamma radiation, or a
combination of all types of methods, may be advisable for subsurface contamination. In
addition to measurements to determine volumetric contamination in environmental media,
measurements of surface contamination on building and equipment surfaces may also be
needed. Additional discussion of measurement techniques and their limitations for soil and
buildings is provided in Multi-Agency Radiation Survey and Site Investigation Manual
(MARSSIM) (U.S. EPA et al. Rev 1. 2000d), and for equipment is provided by Multi-
Agency Radiation Survey and Assessment of Materials and Equipment Manual
(MARSAME) (U.S. EPA et al. 2009b).
Q5. What field radiation survey instruments should be used and what are their lower
limits of detection?
A. Selection of appropriate radiation detection instruments for site characterization depends
on the decay characteristics of the radionuclides potentially present at the site, suspected
contamination patterns, and activity concentrations, among other factors. Numerous
documents have been written on this topic. For a general discussion on radiation survey
instruments, readers are directed to Real-Time Measurement of Radionuclides in Soil:
Technology and Case Studies document (ITRC 2006), Real-Time Measurement of
Radionuclides in Soil on-line training course (ITRC 2008), Multi-Agency Radiation Survey
and Site Investigation Manual (MARSSIM) (U.S. EPA et al. Rev 1. 2000d) and Chapter
10 of RAGs Part A (U.S. EPA 1989a). For supplemental information regarding the
usability of analytical data for performing a baseline risk assessment at radioactively
contaminated sites, readers should refer to Guidance for Data Usability in Risk
Assessment, Part B (U.S. EPA 1992d).
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Q6. What sample measurement units for radiation risk assessment are typically used?
A. Concentrations of radionuclides in environmental media are typically expressed in terms of
"activity" of the radionuclide per unit mass (for soil, sediment, and food-stuffs) or volume
(for water and air) of the environmental medium. Two different systems of units for
radioactivity are currently in common usage: the International System (SI) units, and the
"conventional" or "traditional" units, which were used before the advent of the SI system.
The principal unit of radioactivity in the SI system is the Becquerel (1 Bq = 1
disintegration/second), while the basic conventional unit of activity is the Curie (1 Ci = 3.7
x 1010 Bq). Since most radiation standards in the United States are expressed in
conventional units, this system is used in this document. Concentrations of radionuclides in
environmental media at contaminated sites are typically far below Curie quantities, and are
commonly expressed in units of picoCuries (1 pCi = 10"12 Ci = 3.7 x 10"2 Bq). Typical
conventional units for reporting environmental measurements are picoCuries per gram
(pCi/g) for soil (dry-weight), picoCuries per liter (pCi/L) for groundwater or surface water,
and picoCuries per cubic meter (pCi/m3) for air. The corresponding SI units, typically used
in other countries, are Bq/g, Bq/L, Bq per 100 cm2, and Bq/m3.
Radionuclide concentrations on building or equipment surfaces are specified in units of the
activity concentrations of the radionuclide of concern in a specified surface area, typically
disintegration per minute (dpm) per 100 square centimeters (cm2) or pCi per 100 cm2,
while the SI system, typically used in other countries, would use Bq per 100 cm2.
A special unit, the working level (WL), is used as a measure of the concentration of short-
lived radon decay products in air. WL is any combination of short-lived radon decay
products in 1 liter of air that will result in the ultimate emission of 1.3 x 105 million
electron volts (MeV) of alpha energy. The working level month (WLM) is exposure to 1
WL for 170 hours (1 working month).
The radiation "exposure" rate is often reported in addition to radionuclide concentrations
in environmental media. Radiation exposure, in this context, refers to the transfer of energy
from a gamma radiation field to a unit mass of air. The unit for radiation exposure is the
roentgen (1 R = 2.58 x 10"4 coulombs of charge per kilogram of air). Exposure rates at
contaminated sites are typically expressed in units of microroentgens/hour (|iR/hr).
Q7. During a remedial action evaluation what sample measurement units may be used?
A. For remedial action evaluations, it is often useful to express radionuclide concentrations in
terms of mass concentration. Mass units provide insight and information into treatment
selection, treatment compatibility, and treatment efficiency, particularly for remedial
actions involving mixed waste. However since radionuclides are generally measured in
terms of activity for health evaluation purposes, except when assessing the non-cancer risk
posed by uranium, the practice of using activity should continue for response actions at
CERCLA remedial sites in order to ensure protectiveness of human health. Proposed and
final site decision documents (e.g., proposed plans, Record of Decisions [RODs]) generally
should include, in addition to activity measurements, estimates of concentrations in terms
of mass consistent with those used for non-radiological contaminants. Typical units for
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expressing mass in environmental media for soil and water are milligrams per kilogram
(mg/kg) for soil and milligrams per liter (mg/L) for water. These mass units also can be
expressed as parts per million (ppm) for soil and water, which is equivalent to mg/kg and
mg/L since the density of water is 1 kilogram per liter (kg/L) under most environmental
conditions. To estimate the radionuclide concentrations in ppm, the following equations
can be used:
mg kgSo,i = (2.8 x 10~12)xAx Tin x pCi/g
mg/lWater = (2.8 x 10~15) X A X T"l/2 xpd/L
ppm soil = (2.8 x 10'12) xAx Tin x pd/g
ppmwater = (2.8 x 10~15) x Ax TmxpCi/L
where A is the radionuclide atomic weight and T1/2 is the radionuclide half-life in years.
Most radionuclides have half-lives ranging from a few years to 10,000 years, which means
that for most radionuclides, an activity of 1 pCi/g would mean the concentration value of
the radionuclide would be well under 1 x 10"6 ppm. EPA's PRG and DCC calculators
(EPA 2002a, 2004a, 2007, 2009a, 2010a, and 2010b) provide concentrations in media
corresponding to the target risk and dose in both activity and mass where it is possible to
convert activity concentrations to mass.
Q8. Are radionuclides included in EPA's Contract Laboratory Program (CLP)? If not,
where should comparable radioanalytical services be obtained?
A. Radionuclides are not standard analytes in EPA's CLP program. Contract laboratory
support for radionuclide analysis may be obtained through the EPA Office of Emergency
Management (OEM) Environmental Response Laboratory Network (ERLN), which keeps
an updated list of laboratories or through EPA's radiation laboratories. Generally,
radioanalytical services may also be obtained through a site-specific or pre-placed EPA
regional or national contract or Interagency Agreement that provides access to analytical
services.
EPA has published information on radionuclide methods in Multi-Agency Radiological
Laboratory Analytical Protocols Manual (MARLAP) (U.S. EPA et al. 2004b) Inventory of
Radiological Methodologies for Sites Contaminatedwith Radioactive Materials (U.S. EPA
2006) and Chapter 10 ofiMGSPart A (U.S. EPA 1989a). MARLAP provides guidance for
planning, implementing, and assessing projects that are using the laboratory analysis of
radionuclides. The U.S. EPA 2006 document describes radioanalytical methodologies used
to characterize environmental samples containing radionuclides, including screening
methodologies and radionuclide-specific analyses. In addition, EPA's Radiochemistry
Procedures Manual (U.S. EPA 1984) provides information for radionuclide-specific
analytical techniques.
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Q9. How can I decide if the data collected are complete and of known quality?
A. All data should be collected under an approved site-specific Quality Assurance Project
Plan (QAPP), which should include appropriate data validation criteria. Relevant policies
and guidance pertaining to quality assurance and the development of QAPPs are available
at http://epa.gov/qualitv/document (e.g., EPA Quality Program Policy CIO 2106.0; EPA
Requirements for Quality Management Plans (QA/R-2), EPA Requirements for QA
Project Plans (QA/R-5), and Guidance on Systematic Planning Using the Data Quality
Objectives Process EPA QA/G-4).
II. EXPOSURE ASSESSMENT
Q10. For CERCLA risk assessments at remedial sites, is it appropriate to use guidance or
approaches developed by other Federal, State or Tribal Agencies or by International
or National Organizations?
A. EPA has made the policy decision that risks from radionuclide exposures at remedial sites
should be estimated in the same manner as chemical contaminants, which is consistent
with EPA's remedial program implementing guidance (e.g., EPA 1997g, 1999d,
2000f). Consequently, approaches that do not follow the remedial program's policies and
guidance should not be used at CERCLA remedial sites. Should regional staff have
questions, they should consult with the Superfund remedial program's National Radiation
Expert (Stuart Walker of OSRTI at the time this fact sheet was issued, at (703) 603-8748
or walker.stuart@epa.gov). before using guidance from other organizations that is not
already incorporated into this and other EPA Superfund remedial program guidance. The
current Superfund remedial program's National Radiation Expert will be listed on the
Superfund Radiation webpage at:
http://www.epa.gov/superfund/health/contaminants/radiation/index.htm.
Qll. How does the exposure assessment for radionuclides differ from that for chemicals?
A. For the Superfund remedial program, exposure assessment for radionuclides is similar to
that for chemicals. Both nonradioactive chemical assessments and radionuclide
assessments should follow the same basic stepscharacterizing the exposure setting,
identifying exposure pathways and potential receptors, estimating exposure point
concentrations, and estimating exposures and intakes. In addition to the exposure
pathways considered for chemicals (e.g., ingestion of contaminated water, soil, or
foodstuffs, and inhalation of contaminated air), external exposure to penetrating radiation
(i.e., gamma radiation and X-rays) may be an important exposure pathway for certain
radionuclides in near-surface soils. Dermal absorption is considered to be an insignificant
exposure pathway for radionuclides and generally is not evaluated. However,
radionuclides that are on the skin would be appropriate for evaluation under the external
pathway. Figure 2 depicts typical exposure pathways for humans to radionuclides;
additional pathways that may be considered on a site-specific basis, where appropriate,
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are discussed in Q12. Additional discussion of radiation exposure pathways is provided in
the user guides for the PRG and DCC calculators (EPA 2002a, 2004a, 2007, 2009a,
2010a, and 2010b); each of these illustrations in Figure 2 appears in these user guides
with additional explanatory text and in a larger size that is more legible.
Q12. Should exposure pathways be added or deleted based on site-specific conditions?
A. Generally, yes. Inclusion or deletion of exposure pathways should be based on site-
specific conditions, including but not limited to local hydrology, geology, potential
receptors, and current and potential future land use, among other factors. Accordingly,
some exposure pathways may not be appropriate for a given site and may be deleted; in
such cases, the Region should explain its justification for doing so and provide specific
supporting data and information in the administrative record documents that discuss the
risk assessment (e.g., Baseline Risk Assessment, RI, ROD, etc.). In other cases, exposure
pathways that are typically not significant may be important under site-specific
conditions (e.g., ingestion of contaminated fish for recreational scenarios, ingestion of
contaminated meat or milk from livestock for agricultural scenarios) and should be
included in the assessment. A well-supported conceptual site model should facilitate
users making site-specific adjustments when appropriately supported by site-specific
information, such as deleting the contaminated fish pathway for the agricultural
scenario when the site is in an area that would not support fish ponds.
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Figure 2. Typical Radionuclide Exposure Pathways for Humans
Outdoor (or Composite) Worker: Soil Exposure
Resident: Soil Exposure
External Exposure Incidental
Inhalation of
Dust Particulates
Consumption of
Fruits and Vegetables
Incidental
Ingestion of Soil
Consumption of Swine °f V?fb'M
and Fruits
Consumption of
Incidental Ingestion
of Soil
Inhalation of , ,r, ,
. . Consumption of Fish
Dust Particulates
External Exposure
Tapwater Ingestion Exposure
Fish Ingestion Exposure
Water It
- - Inhalation of
Volatiles
~~k
(^p
Resident: Settled Dust
Resident: Ambient Air
to Source
External Exposure
Ingestion of Dust
Direct External Exposure
Direct External Exposure to Source
Resident: Contaminated Building Materials
-------
Figure 2. Typical Radionuclide Exposure Pathways for Humans - continued
Indoor Worker: Contaminated
Building Materials
Indoor Worker: Settled Dust
External Exposure
Due to Air Submersion \
V
. w
>
Settled Dust: Resident
3D Exposure to Fixed Contaminated Building
Materials (Outdoor Worker)
Indoor Worker: Settled Dust on Indoor Surfaces
Indoor Worker: Ambient Air
External Exposure
to Radiation
ilBHHHSB!!! ill
2D Exposure to Fixed Contaminated Finite Slabs
(Resident)
~ 0
Direct External Exposure from Contaminated Dust
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Q13. How should radioactive decay products be addressed in an exposure assessment to
determine dose or risk?
A. All radionuclides, by definition, undergo radioactive decay. In this process, one unstable
nucleus of an element transforms (decays) spontaneously to a nucleus of another element.
As the unstable nucleus decays, energy is released as particulate or photon radiation, or
both, and the radionuclide is transformed in atomic number and/or atomic mass. The
resulting decay products, or progeny, may also be radioactive and undergo further decay.
Various decay products may have different physical and chemical characteristics that
affect their fate and transport in the environment as well as their radiotoxicity. In cases
where decay products have greater radiotoxicity than the original radionuclide, the
potential radiation dose and health risk may increase over time; in such cases, the exposure
assessment should consider the change in concentrations of all decay products over time to
determine the time of maximum potential impact.
To help ensure protectiveness of human health, consideration of all potential radioactive
decay products is a key element of the exposure assessment for radionuclides. Many of the
computerized mathematical models available for simulating the behavior of radionuclides
in the environment (see Q16) incorporate the ingrowth and decay of radioactive decay
products as a function of time; these models are useful in pinpointing the time of maximum
dose or risk. Similarly, slope factors (see Q21) and dose conversion factors (see Q22) for
some radionuclides may include consideration of radioactive decay products, where
appropriate, to facilitate these considerations in estimating potential radiation dose and
risk. However, these values typically assume that all decay products are present at the
same concentration as the primary radionuclide (i.e., secular equilibrium), which may not
be appropriate for all situations. In those situations model users may need to calculate risks
or doses for various radionuclides in the decay chain separately and use a sum of the
fractions approach for determining total risk or dose. For additional information regarding
such limitations see the user guides for the PRG and DCC calculators (U.S. EPA 2002a,
2004a, 2007, 2009a, 2010a, and 2010b).
Q14. To what extent should generic and site-specific factors and parameter values be
used in exposure assessments?
A. For both radionuclide and chemical assessments in the Superfund remedial program,
EPA recommends use of empirically-derived, site-specific factors and parameter values,
where these values can be justified and documented. For generic assessments, EPA
recommends use of the default parameter values provided in the PRG and DCC calculators
(EPA 2002a, 2004a, 2007, 2009a, 2010a, and 2010b).
Q15. How should exposure point concentrations be determined?
A. As for chemical contaminants, exposure point concentrations for radionuclides in
environmental media and radiation exposure rates (e.g., alpha, beta, and gamma) should
be either measured, modeled, or both, to help ensure protectiveness of human health. To
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the extent possible, measurement data should be used to evaluate current exposures.
When measurements at the exposure locations cannot be made, or when potential
concentrations and exposures will be predicted at future times, modeling may be needed
to estimate past or future movement of radionuclides (see Q16).
Q16. What calculation methods or multimedia radionuclide transport and exposure models
are recommended by EPA for Superfund risk assessments?
A. The PRG calculators (U. S. EPA 2002a, 2007, 2009a), which are used to develop risk-based
PRGs for radionuclides, are recommended by EPA for Superfund remedial radiation risk
assessments. These risk and dose assessment models are similar to EPA's methods for
chemical risk assessment at CERCLA sites. Guidance on how to use each calculator, the
default input parameters and their sources, is provided in the user guide for each calculator.
In addition, a tutorial for using the PRG calculator is included in module 3 of the on-line
training course Radiation Risk Assessment: Update and Tools (ITRC 2007), and a tutorial
for the BPRG and SPRG calculators is provided in module 3 of the on-line training course
Decontamination and Decommissioning of Radiologically-Contaminated Facilities (ITRC
2008b). The PRG calculator superseded the Soil Screening Guidance for Radionuclides
(Rad SSG) calculator (U.S. EPA 2000e).
To avoid unnecessary inconsistency between radiological and chemical risk
assessment at the same site, users should generally use the same model for chemical
and radionuclide risk assessment. If there is a reason on a site-specific basis for using
another model justification for doing so should be developed. The justification should
include specific supporting data and information in the administrative record. The
justification normally would include the model runs using both the recommended EPA
PRG model and the alternative model. Users are cautioned that they should have a
thorough understanding of both the PRG recommended model and any alternative model
when evaluating whether a different approach is appropriate. When alternative models are
used, the user should adjust the default input parameters to be as close as possible to the
PRG inputs, which may be difficult since models tend to use different definitions for
parameters. Numerous computerized mathematical models have been developed by EPA
and other organizations to predict the fate and transport of radionuclides in the
environment; these models include single-media unsaturated zone models (for example,
groundwater transport) as well as multi-media models. These models have been designed
for a variety of goals, objectives, and applications; as such, no single model may be
appropriate for all site-specific conditions. Generally, even when a different model is used
to predict fate and transport of radionuclides through different media, EPA recommends
using the PRG calculators for the remedial program to establish the risk-based
concentrations to ensure consistency with CERCLA, the NCP and EPA's Superfund
guidance for remedial sites.
EPA has evaluated five soil to groundwater models ranging from the simple to the multi-
dimensional in Simulating Radionuclide Fate and Transport in the Unsaturated Zone:
Evaluation and Sensitivity Analyses of Select Computer Models (EPA 2002c). This
evaluation is also summarized in Part 3 of the Rad SSG Technical Background Document
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(TBD) (EPA 2000b). For further information on selection of models appropriate to meet
specific-site characteristics and requirements, readers can refer to Ground-Water Modeling
Compendium (U.S. EPA 1994c), and A Technical Guide to Ground-Water Model Selection
at Sites Contaminated with Radioactive Substances (U.S. EPA 1994d). While these
documents specifically address groundwater models, the model selection criteria and logic
may be useful for other models as well.
Q17. How should Radon-222 (radon) and Radon-220 (thoron) exposures and risks be
evaluated?
A. Radon-222 (Rn-222) and Radon-220 (Rn-220) are radioactive gases that are isotopes of
the element radon (Rn). Each is produced by the radioactive decay of an isotope of radium
(Ra). The parent radium isotope for Rn-222 (also called radon), is Ra-226 and the parent
radium isotope for Rn-220 (also called thoron) is Ra-224. (Although thoron is produced
from the radioactive decay of Ra-224, it is often referred to as a decay product of Ra-228,
which is a longer-lived precursor typically measured in environmental samples.) Each
radon isotope gives rise to a series or chain of short-lived radioactive decay products that
emit alpha particles, which can damage lung tissues if inhaled. Of the two decay chains,
the radon series is longer lived and more hazardous than the thoron series. Both decay
chains are addressed by the same ARAR discussed below. Risk and dose assessments of
radon and thoron concentrations at CERCLA remedial sites should be developed using the
PRG and DCC calculators (U.S. EPA 2002a, 2004a, 2007, 2009a, 2010a, and 2010b).
Structures built on radium-contaminated soil or constructed with radium-bearing materials
can accumulate elevated concentrations of radon and thoron in indoor air. Some radiation
protection standards that may be potential ARARs at a site explicitly exclude dose or risk
from radon and its decay products from consideration. Other potential ARARs directly
address radon and its decay products (for example, under 40 CFR 192.12(b)(1) a standard
of 0.03 working levels (WL) and a goal of 0.02 WL for allowable concentrations of radon
decay products in indoor air).
Several EPA-approved methods are available for measuring radon and progeny
concentrations in indoor air (EPA et al., Rev 1. 2000d). Because the indoor radon
guidelines for homeowners are expressed in terms of picocuries per liter (pCi/L) of air,
tools to address pCi/L are more prevalent than those to address WL. For purposes of
demonstrating compliance with the 0.02 WL Uranium Mill Tailings Radiation
Control Act (UMTRCA) regulations as an ARAR, users may assume that either 5
pCi/L of Rn-222, or 7.5 pCi/L of Rn-220, corresponds to 0.02 WL. Therefore 5 pCi/L
of Rn-222 or 7.5 pCi/L of Rn-220 may be considered to be the concentration for
complying with the UMTRCA indoor radon standard as an ARAR. These values are
based on an indoor residential equilibrium fraction of 0.4 (40%) for Rn-222 and 0.02 (2%)
for Rn-220. For the case of secular equilibrium, where the equilibrium fraction is 100%,
the corresponding concentrations of Rn-222 and Rn-220 would be 2 pCi/L and 0.15 pCi/L
respectively. The methodology for making this conversion is discussed on page 11 of the
International Commission on Radiological Protection's (ICRP) guidance Lung Cancer
Risk from Radon and Progeny (ICRP 2011). To adjust the indoor radon concentration to
any given equilibrium fraction, the value for 0.02 WL at secular (100%) equilibrium is
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divided by the appropriate equilibrium fraction. Thus, 2 pCi/L divided by 0.4 yields 5
pCi/L forRn-222 and 0.15 pCi/L divided by 0.02 yields 7.5 pCi/L for Rn-220. This 40%
value for Rn-222 is discussed on page 190 of the NAS Report Health Effects of Exposure
to Radon: BEIR VI (NAS 1999). For Rn-220, the assumed equilibrium factor of 2% is
discussed on page 206 of Appendix E: Sources-to-effects assessment for radon in homes
and workplaces of the United Nations Report Effects of Ionizing Radiation Volume II
(UNSCEAR 2006).
Computer codes have been developed to predict radon concentrations in indoor air and
potential human exposure, based on simplified equations and assumptions; these models
may yield results that are meaningful on average (e.g., for a geographical region) but
highly imprecise for an individual house or structure. Despite their widespread use, these
codes should be used with caution and their estimates interpreted carefully. Also, some
states have their own radon testing and mitigation requirements that may be potential
ARARs at a site (see Q38).
Q18. How long a time period should be considered for possible future exposures?
A. The PRG calculators include assumptions for the appropriate time period for generic land
use exposure scenarios. Furthermore, in some cases, federal or state ARARs may include
specific time-frame requirements for a given purpose, which is often a thousand years for
dose-based standards. Several of the isotopes are listed with a "+E" designation. This
designation indicates that the dose conversion factor (DCF) includes the contribution from
ingrowth of daughter isotopes out to 1,000 years. As a result, the DCC calculators allow
the selection of radionuclides with the +E designation, which provide a dose assessment
based on the year of peak dose over 1,000 years since many standards that are potential
ARARs specify this time-period for dose assessments. If the ARAR does not specify a
time-period for assessment, users should use the +D designation for a radionuclide where
the decay chain is in secular equilibrium. The +D designation indicates the contribution
from ingrowth of daughter isotopes out to 100 years.
Q19. How should the results of the exposure assessment for radionuclides be
presented?
A. Results of the exposure assessment for radionuclides should be presented with intake and
external exposure estimates for use in risk characterization. If it is determined that there
are dose-based standards that are ARARs at a CERCLA remedial site, then the intake and
external exposure estimates should also be used for dose assessment.
Note that intake estimates for radionuclides should not be divided by body weight or
averaging time as is done for chemical contaminants, because the radionuclide slope
factors and dose conversion factors are age averaged, which accounts for average body
weight in the United States population over different ages and the risk or dose is
dependent upon the total exposure not the time period over which it occurs. Intake
estimates for inhalation or ingestion pathways should include the total activity of each
radionuclide inhaled or ingested via each pertinent route of exposure (e.g., ingestion of
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contaminated drinking water, direct ingestion of contaminated soil, ingestion of
contaminated produce, milk, or meat). Measured or predicted external exposure rates
should be presented, along with the exposure time, frequency, and duration. The
concentration of each radionuclide in the medium is needed to estimate the risk from the
external pathway using slope factors.
111. TOXICITY ASSESSMENT
Q20. What is the mechanism of radiation damage?
A. Radiation emitted by radioactive substances can transfer sufficient localized energy to
atoms to remove electrons from the electron cloud surrounding the nucleus (ionization). In
living tissue, this energy transfer can produce chemically reactive ions or free radicals,
destroy cellular constituents, and damage DNA. Improperly repaired DNA damage is
thought to be a major factor in carcinogenesis. (While ionizing radiation may also cause
other detrimental health impacts, only radiogenic cancer risk is normally considered in
CERCLA risk assessments [see Q26].)
The type of ionizing radiation emitted by a particular radionuclide depends on the exact
nature of the nuclear transformation, and may include emission of alpha particles, beta
particles (electrons or positrons), and neutrons; each of these transformations may be
accompanied by emission of photons (gamma radiation or X-rays). Each type of radiation
differs in its physical characteristics and in its ability to inflict damage to biological tissue.
The various types of radiation are often categorized as low linear energy transfer (LET)
radiation (photons and electrons) and high-LET radiations (alpha particles and neutrons)
for radiation risk and dose estimates.
Ionizing radiation can cause deleterious effects on biological tissues only when the energy
released during radioactive decay is absorbed in tissue. The average energy imparted by
ionizing radiation per unit mass of tissue is called the "absorbed dose." The SI unit of
absorbed dose is the joule per kilogram, also assigned the special name the Gray (1 Gy = 1
joule/kg); the conventional unit of absorbed dose is the rad (1 rad =100 ergs/g = 0.01 Gy).
Q21. What are radionuclide slope factors?
A. EPA has developed slope factors for estimating incremental cancer risks resulting from
exposure to radionuclides via inhalation, ingestion, and external exposure pathways.
Slope factors for radionuclides represent the probability of cancer incidence as a result of
a unit exposure to a given radionuclide averaged over a lifetime using the linear no-
threshold model. It is the age-averaged lifetime excess cancer incident rate per unit intake
(or unit exposure for external exposure pathway) of a radionuclide (U.S. EPA 1989a).
EPA recommends the slope factors that are used in the PRG calculators for CERCLA
remedial radiation risk estimates (U.S. EPA 2002a, 2007, and 2009a). Current
radionuclide slope factors incorporate the age- and gender-specific radiogenic cancer
risk models from Federal Guidance Report No. 13: Cancer Risk Coefficients for
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Environmental Exposure to Radionuclides (U.S. EPA 1999c), which assume a maximum
lifetime for an individual of 120 years, but incorporate competing causes of death over a
120 year lifetime.
Q22. What are radionuclide dose conversion factors?
A. Dose conversion factors (DCFs), or "dose coefficients", for a given radionuclide
represent the dose equivalent per unit intake (i.e., ingestion or inhalation) or external
exposure of that radionuclide. These DCFs are used to convert the amount of
radionuclide externally exposed, ingested, or inhaled to a radiation dose from an
environmental sample of modeled estimate of radionuclide concentration in soil, air,
water, or foodstuffs. DCFs may be specified for specific body organs or tissues of
interest, or as a weighted sum of individual organ dose, termed the effective dose
equivalent. (These quantities are discussed further in Q23.) These DCFs may be
multiplied by the total activity of each radionuclide inhaled or ingested per year, or the
external exposure concentration to which a receptor may be exposed, to estimate the
dose equivalent to the receptor.
EPA recommends the DCFs that are used in the DCC calculators for CERCLA remedial
dose assessments (U.S. EPA 2004a, 2010a, and 2010b). The most up to date
radionuclide DCFs in the current DCC calculators, ICRP 60, incorporate age- and
gender-specific models and are from the CD supplement to Federal Guidance Report
No. 13: Cancer Risk Coefficients for Environmental Exposure to Radionuclides (U.S.
EPA 1999c).
Q23. What is dose equivalent, effective dose equivalent, and related quantities?
A. As discussed in Q20, different types of radiation have differing effectiveness in
transferring their energy to living tissue. Since it is often desirable to compare doses
from different types of radiation, the quantity "dose equivalent," or "equivalent dose," has
been defined as a measure of the energy absorbed by living tissues, adjusted for the type of
radiation present. The SI unit for dose equivalent is the Sievert (Sv) and the conventional
unit is the rem (1 rem = 0.01 Sv). The absorbed dose is multiplied by Quality Factor (Q) or
radiation weighting factor (wr) to compute dose equivalent; these values range from 1 for
photons and electrons to 10 for neutrons to 20 for alpha particles. For an equal amount of
energy absorbed, an alpha particle will inflict approximately 20 times more damage to
biological tissue than that inflicted by a beta particle or gamma ray. Internally deposited
(inhaled or ingested) radionuclides may be deposited in various organs and tissues long
after initial deposition. The "committed dose equivalent" is defined as the integrated dose
equivalent that will be received by an individual during a 50-year period following the
intake. By contrast, external radiation exposure contributes to dose only as long as the
receptor is present within the external radiation field.
When they are exposed to equal doses of radiation, different organs and tissues in the
human body will exhibit different cancer induction rates. The quantity "effective dose
equivalent," or "effective dose," was developed by the International Commission on
Radiological Protection (ICRP) to account for these differences and to normalize radiation
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doses and effects on a whole body basis for regulation of occupational exposure. The
effective dose equivalent is computed as a weighted sum of organ-specific dose equivalent
values, with weighting factors specified by the ICRP (ICRP 1977, 1979). The effective
dose equivalent is equal to that dose equivalent, delivered at a uniform whole-body rate,
that corresponds to the same number (but possibly dissimilar distribution) of fatal
stochastic health effects as the particular combination of organ dose equivalents.
Q24. What is the critical organ approach to dose limitation?
A. Regulatory standards developed by EPA and the Nuclear Regulatory Commission (NRC)
that use the critical organ approach usually consist of a combination of whole body and
critical organ dose limits, such as 25 mrem/yr to the whole body, 75 mrem/yr to the
thyroid, and 25 mrem/yr to any critical organ other than the thyroid. For example, EPA's
uranium fuel cycle rule, 40 CFR 190.10(a); NRC's low level waste rule, 10 CFR 61.41;
and EPA's management and storage of high level waste by NRC and agreement states rule,
40 CFR 191.03(a), use this "25/75/25 mrem/yr" dose limit approach. EPA's management
and storage of high level waste by U.S. Department of Energy (DOE) rule, 40 CFR
191.03(b), is expressed as 25 mrem/yr to the whole body and 75 mrem/yr to any critical
organ (including the thyroid). When these standards were adopted, dose was calculated and
controlled for each organ in the body and uniform radiation of the "whole body." The
"critical organ" was the organ that received the most dose for the radionuclide concerned.
With the adoption of the dose equivalent concept, the dose to each organ is weighted
according to the effect of the radiation on the overall system (person). The new dose
system for the EPA and NRC regulations allows for one value of dose equivalent (see Q
23) to be assigned as a limit, which is protective of the entire system. The critical organ
approach required individual limits for each organ based on the effect of radiation on that
organ.
It should be noted that although most critical organ standards include 25 mrem/yr or higher
(for example, 75 mrem/yr to the thyroid) dose limits, these critical organ standards are not
comparable to 25 mrem/yr effective dose equivalent standards or guidance. EPA has
determined that for Superfund remedial sites a 25 mrem/yr effective dose equivalent level
should not be used for the purposes of establishing cleanup levels at CERCLA remedial
sites (see 1997a). This determination does not apply to critical organ standards (see 1997a).
For further discussion of EPA's comparison of critical organ and effective dose equivalent
limits see pages 4-5 of Attachment B to EPA 1997a. The DCC, BDCC, and SDCC
calculators are not intended for demonstrating compliance with ARARs using the critical
organ dose approach based on ICRP 2.
Q25. How should radionuclide slope factors and dose conversion factors be used?
A. EPA recommends that radionuclide slope factors be used to estimate the excess
cancer risk resulting from exposure to radionuclides at radiologically
contaminated sites, consistent with the NCP's risk range (10~4 to 10"6 lifetime
excess cancer risk) for CERCLA remedial responses. The incremental risk generally
is calculated by multiplying the estimates of chronic daily intake over a lifetime by a
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slope factor that is appropriate for the exposure route (ingestion, inhalation and external
exposure) and media (e.g., soil, food and water) of concern.
Cancer risk from radionuclide exposures may also be estimated by multiplying the
effective dose equivalent computed using the dose conversion factors (DCFs) by a risk-
per-dose factor. Some key differences in the two cancer risk methods are summarized in
Table 2.
The primary use of DCFs by the Superfund remedial program generally should be to
compute doses resulting from site-related exposures for comparison with radiation
protection standards (see Q32 and 33) that are determined to be ARARs. This can be
accurately accomplished by multiplying the estimates of annual chronic daily intake by a dose
conversion factor that is appropriate for the exposure route (ingestion, inhalation and external
exposure) and media (e.g., soil, food and water) of concern.
At Superfund remedial responses, excess cancer risk generally represents cumulative
lifetime cancer morbidity risk from a multi-year exposure period (e.g., 30 years of
exposure for residential scenario). In contrast, when complying with most dose-based
standards that are considered to be ARARs at CERCLA remedial responses, the dose
limits are typically expressed in terms of annual exposure (for example, the effective dose
equivalent resulting from exposure during a 1-year period, mrem/year).
DCFs from the default settings in the latest versions of the DCC, BDCC, and SDCC
calculators (U.S. EPA 2004a, 2010a, and 2010b) should be used for complying with
ARARs based on effective dose equivalent, while DCFs from ICRP 2 should be used
when complying with ARARs based on the critical organ approach. There are some
potential ARARs (for example, the maximum contaminant levels [MCLs] for beta and
photon emitters) that specify in the text of the regulation itself which DCFs should be
used.
Q26. In addition to cancer, should the potential teratogenic and genetic effects of
radiation exposures be considered?
A. Biological effects associated with exposure to ionizing radiation in the environment may
include carcinogenicity (induction of cancer), mutagenicity (induction of mutations in
somatic or reproductive cells, including genetic effects), and teratogenicity (effects on
the growth and development of an embryo or fetus). Agency guidance (U.S. EPA 1989a,
1994b) indicates that the radiogenic cancer risk is normally assumed to be limiting for
risk assessments at Superfund remedial sites, and evaluation of teratogenic and genetic
effects is not required. Similarly, consideration of acute effects at CERCLA remedial
sites generally is not required, since these effects occur only at doses much higher than
those normally associated with environmental exposures.
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Table 2. Comparison of Radiation Risk Estimation Methodologies: Slope Factors vs.
Effective Dose Equivalent
Parameter
Slope Factor Approach
Effective Dose Equivalent (EDE) x
Risk Factor Approach
Competing
Risks
Persons dying from competing causes of death
(such as disease, accidents) are not considered
susceptible to radiogenic cancer.
Probability of dying at a particular age from
competing risks is considered based on the mortality
rate from all causes at that age in the 1989 to 1991
(previously 1979 to 1981) U.S. population.
Competing risks not considered.
Risk
Models
Age-dependent and gender-dependent risk models
for 14 cancer sites are considered individually and
integrated into the slope factor estimate.
Risk estimate averaged over all
ages, sexes, and cancer sites.
Genetic
Risk
Genetic risk is not considered in the slope factor
estimates; however, ovary is considered as a potential
cancer site.
EDE value includes genetic risk
component.
Dose
Estimates
Low-LET and high-LET dose estimates considered
separately for each target organ.
Dose-equivalent includes both low-
LET and high-LET radiation,
multiplied by appropriate Quality
Factors.
RBE for high- LET
(alpha) radiation
20 for most sites (8 prior to 1994)
10 for breast (8 prior to 1994)
1 for leukemia (1.117 prior to 1994)
20 (all sites)
Organs
Considered
Estimates of absorbed dose to 16 target organs/tissues
considered for 13 specific cancer sites plus residual
cancers.
EDE (ICRP, 1979) considers dose
estimates to six specific target
organs plus remainder (weighted
average of five other organs).
Lung Dose
Definition
Absorbed dose used to estimate lung cancer risk
computed as weighted sum of dose to
tracheobronchial region (80%) and pulmonary lung
(20%).
Average dose to total lung (mass
weighted sum of doses to the
tracheobronchial region,
pulmonary region, and pulmonary
lymph nodes).
Integration
Period
Variable length (depending on organ-specific risk
models and
consideration of competing risks) not to exceed 110
years.
Fixed integration period of 50 years
typically considered.
Dosimetric /
Metabolic
Models
Metabolic models and parameters for dose estimates
follow recent recommendations of the ICRP series of
documents on age-specific dosimetry (ICRP, 1989,
1993, 1995a, 1995b), where available; previous
estimates based primarily on ICRP 30 (ICRP, 1979).
Typically employ ICRP
Publication 30 (ICRP 1979)
models and parameter for
radionuclide uptake, distribution,
and retention.
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Q27. Should chemical toxicity of radionuclides be considered?
A. At Superfund remedial program radiation sites, EPA generally evaluates potential human
health risks based on the radiotoxicity (the adverse health effects caused by ionizing
radiation), rather than on the chemical toxicity, of each radionuclide present. Uranium, in
soluble form, is a kidney toxin at mass concentrations slightly above background levels. It
is the only radionuclide for which the chemical toxicity has been identified to be
comparable to or greater than the radiotoxicity and for which an oral reference dose (RfD)
has been established to evaluate chemical toxicity. To properly evaluate human health
risks, both effects (radiogenic cancer risk and chemical toxicity) should be considered for
radioisotopes of uranium. When risk estimates will be made of the chemical toxicity of
uranium, EPA recommends using the Regional Screening Levels for Chemical
Contaminants at Superfund Sites (RSL) calculator (U.S. EPA 2008) for uranium in soil,
water and air and the equations in (U.S. EPA 2003) for uranium in dust inside of buildings.
The RSL calculator is frequently updated.
IV. RISK CHARACTERIZATION
Q28. How should radionuclide risks be estimated?
A. At Superfund remedial sites, risks from radionuclide exposures should be estimated in
a manner analogous to that used for chemical contaminants. The estimates of intake by
inhalation and ingestion and the external exposure over the period of exposure
estimated for the land use (e.g., 30 years residential, 25 years commercial/industrial)
from the exposure assessment should be coupled with the appropriate slope factors for
each radionuclide and exposure pathway. Only excess cancer risk should be considered
for most radionuclides (except for uranium, as discussed in Q27). The total
incremental lifetime cancer risk attributed to radiation exposure is estimated as the
sum of the risks from all radionuclides in all exposure pathways.
Q29. Should radionuclide and chemical risks be combined?
A. Generally, yes. At CERCLA remedial sites, excess cancer risk from both radionuclides and
chemical carcinogens should be summed to provide an estimate of the combined risk
presented by all carcinogenic contaminants as specified in OSWER directive 9200.4-18
(U.S. EPA 1997a). An exception would be cases in which a person reasonably cannot be
exposed to both chemical and radiological carcinogens; Regions should include specific
supporting data and information in the administrative record to document this conclusion.
Similarly, the chemical toxicity from uranium should be combined as appropriate with that
of other site-related contaminants. As recommended in RAGS Part A (U.S. EPA 1989a),
risk estimates for radionuclides and chemical contaminants also should be tabulated and
presented separately in the risk characterization report.
There are generally several differences between slope factors for radionuclides and
chemicals. However, similar differences also occur between different chemical slope
factors. In the absence of additional information, it is reasonable to assume that
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excess cancer risks are additive for evaluating the total incremental cancer risk
associated with a contaminated site.
Q30. How should risk characterization results for radionuclides be presented?
A. Results should be presented according to the standardized reporting format presented in
RAGS Part D (U.S. EPA 1998a). EPA guidance for risk characterization (U.S. EPA 1995a,
1995b) indicates that four descriptors of risk are generally needed for a full
characterization of risk: (1) central tendency (such as median, mean) estimate of individual
risk; (2) high-end estimate (for example, the 95th percentile) of individual risk; (3) risk to
important subgroups of the population, such as highly exposed or highly susceptible groups
(such as children) or individuals, if known; and (4) population risk. The reasonable
maximum exposure (RME) estimate of individual risk typically presented in Superfund risk
assessments represents a measure of the high-end individual exposure and risk. While the
RME estimate remains the primary scenario for Superfund risk management decisions,
additional risk descriptors may be included to describe site risks more thoroughly (e.g.,
central tendency, sensitive subpopulations). Population risk is generally not used as part of
Superfund risk assessments.
Q31. Is it necessary to present the collective risk to populations estimated along with that
to individual receptors?
A. Generally, no. Risk to potential RME individual receptors generally is the primary measure
of protectiveness under the CERCLA remedial process (thetarget range of 10"6 to 10"4
lifetime excess cancer risk to the RME receptor). As noted in Q30, however, Agency
guidance (U.S. EPA 1995a, 1995b) also indicates that the central tendency risk to the
potentially exposed population may be evaluated where possible. Consideration of central
tendency risk may provide additional input to risk management decisions; such
considerations may be either qualitative or quantitative, depending on the availability of
data.
Q32. How should uncertainty in estimates of radiation risk be addressed in the risk
characterization report?
A. Consideration of uncertainty in estimates of risks from potential exposure to radioactive
materials at CERCLA sites typically is an essential element of informed risk management
decisions. RAGS and subsequent guidance (U.S. EPA 1995a, 1995b) stress the importance
of a thorough presentation of the uncertainties, limitations, and assumptions that underlie
estimates of risk. Either qualitative or quantitative evaluation may be appropriate,
depending on the availability of data and the magnitude of predicted risk. In either case,
the evaluation should address both uncertainty ("the lack of knowledge about specific
factors, parameters, or models") and variability ("observed differences attributable to true
heterogeneity or diversity in a population or exposure parameter"). Estimates of potential
risk should include both central tendency estimates (median, mean) and high-end
estimates (such as RME or 95th percentile).
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Extrapolation from high dose and dose rate exposure is generally done to estimate risks
of low-level exposures for both chemical carcinogens and radionuclides. This extrapolation
typically constitutes the greatest source of uncertainty. Additional uncertainty may be
introduced due to extrapolation of animal data to humans for chemical carcinogens.
Slope factors for both radionuclides and chemicals are used to estimate incremental cancer
risk, which typically represents a small increment over a relatively high baseline incidence.
It should be noted that there is less uncertainty associated with the slope factors for
radionuclides than any, or almost any, chemical slope factors since the radionuclide slope
factors are based primarily on human rather than animal data. Other sources of uncertainty
may be associated with instrumentation and measurements used to characterize the nature
and extent of radionuclides of concern, and the parameters used to characterize
potential exposures of current and future receptors (such as intake rates and frequency of
exposure).
Probabilistic Risk Assessment (PRA) may be used to provide quantitative estimates of the
uncertainties in the risk assessment. However, probabilistic estimates of risk should be
presented as a supplement to, not instead of, the deterministic (point estimate) methods
outlined in RAGS Part A. A tiered approach is often useful, with the rigor of the
analysis depending on the magnitude of predicted risk. Factors to be considered in
conducting a probabilistic analysis typically should include the sensitivity of parameters,
the correlation or dependencies between parameters, and the distributions of parameter values
and model estimates. Detailed guidance on this topic is provided in Use of Probabilistic
Techniques (Including Monte Carlo Analysis) in Risk Assessment (U.S. EPA 1997c) and
Guiding Principles for Monte Carlo Analysis (U.S. EPA 1997d).
Q33. When should a dose assessment be performed?
A. Dose assessments should be conducted during CERCLA remedial responses only when
considering compliance of clean up plans with dose-based ARARs. As discussed in
OSWER Directive 9200.4-18 (U.S. EPA 1997a), cleanup levels for radioactive
contamination at remedial sites should be established as they would for any chemical that
poses an unacceptable risk and the risks should be characterized in standard Agency risk
language consistent with CERCLA guidance for remedial sites. Thus, cleanup levels not
based on an ARAR should be based on the carcinogenic risk range (generally 10~4 to
10"6, with 10"6 as the point of departure and 1 x 10"6 used for PRGs) and expressed in
terms of risk (# x 10"#).
Q34. What is the upper end of the risk range with respect to radionuclides?
A. Consistent with existing Agency guidance for the CERCLA remedial program, while the
upper end of the risk range is not a discrete line at 1 x 10"4, EPA generally uses 1 x 10"4 in
making risk management decisions. A specific risk estimate around 10"4 may be considered
acceptable based on site-specific circumstances. For further discussion of these points and
how EPA uses the risk range, see OSWER Directive 9355.0-30, Role of the Baseline Risk
Assessment in SuperfundRemedy Selection Decisions (U.S. EPA 1991 d). In general, dose
assessment used as a method to assess risk is not recommended as a way of ensuring
protectiveness of human health at CERCLA remedial sites.
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Q35. Should the ARAR protectiveness criteria evaluation recommendation be changed
from 15 mrem/yr to reflect the updates to radiation risk estimates contained in
Federal Guidance Report 13?
A. Yes, ARAR protectiveness criteria evaluation recommendation of 15 mrem/yr should
be changed to 12 mrem/yr to reflect the current federal government position on the
risks posed by radiation, which is contained in EPA's Federal Guidance Report 13
(U.S. EPA 1999c). More recent scientific information reflected in EPA's Federal
Guidance Report 13 risk estimates show that 12 mrem/yr is now considered to correspond
approximately to 3 x 10"4 excess lifetime cancer risk. This updated approach is based on
FGR 13's assumption of a risk of cancer incidence of 8.46 x 10"4 per rem of exposure
(while still using the EPA CERCLA standard period of exposure of 30 years for residential
land use, which also was the basis of the 15 mrem/yr determination in OSWER Directive
9200.4-18). Therefore, the ARAR evaluation guidance first discussed in OSWER Directive
9200.4-18 is being updated to 12 mrem/yr so that ARARs that are greater than 12 mrem/yr
effective dose equivalent (EDE) are generally not considered sufficiently protective for
developing cleanup levels under CERCLA at remedial sites. As before, this ARAR
evaluation tool should not be used as a to be considered (TBC) as a basis for establishing
12 mrem/yr cleanup levels at CERCLA remedial sites.
Please note that the prior references to 15 mrem/yr in OSWER Directive 9200.4-18 were
intended as guidance for the evaluation of potential ARARs and TBCs factors and should
not be used as a TBC for establishing 15 mrem/yr cleanup levels at CERCLA sites.
Consistent with that guidance, using 15 mrem/yr as an ARAR evaluation tool originally
was based on three factors:
1. The CERCLA risk range for remedial sites. In 1997, 15 mrem/yr was
estimated to correspond to approximately 3 x 10"4 under the then EPA
practice of using the dose to risk estimate conversions assumption of a risk
of cancer incidence of 7.6 x 10"4 per rem of exposure, found in ICRP 1991
and NAS 1990. This dose to risk estimate has been superseded by the
assumption of a risk of cancer incidence of 8.46 x 10"4 per rem of exposure
in FGR 13 (U.S. EPA 1999c).
2. Prior EPA radiation rulemakings, and
3. Prior EPA CERCLA site-specific decisions.
Q36. Should dose recommendations from other federal agencies be used to assess risk or
establish cleanup levels?
A. Generally, no. Dose assessments generally should only be performed to assess risks or
to establish cleanup levels at CERCLA remedial sites to show compliance with an
ARAR that requires a dose assessment (for example 40 CFR 61 Subparts H and I, and 10
CFR 61.41). Dose level recommendations from international and other non-EPA
organizations are not enforceable and therefore cannot be ARARs. The selection of
cleanup levels for carcinogens for CERCLA remedy selection purposes should be
consistent with the NCP and CERCLA guidance - i.e., based on the risk range when
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ARARs are not available or are not sufficiently protective. EPA has made the policy
decision to use the NCP's risk range in developing cleanup levels for radionuclides at
CERCLA remedial sites rather than using dose-based guidance since the use of dose-
based guidance. See Q10 for more information on this determination.
EPA recommends using the DCC, BDCC, and SDCC calculators (U.S. EPA 2004a,
2010a, and 2010b) to develop dose assessments for ARAR compliance purposes at
Superfund remedial sites. As indicated on page 2 of the memorandum transmitting the
DCC calculator (U.S. EPA 2004c), that guidance superseded the dose assessment
equations in Chapter 10 of RAGs Part A (U.S. EPA 1989a).
Q37. How and when should exposure rate be used to estimate radionuclide risks?
A. As discussed previously (see Q25 and Q28), EPA recommends that estimates of
radiation risk should be derived using slope factors, in a manner analogous to that
used for chemical contaminants. However, to ensure protectiveness of human health
consistent with CERCLA and the NCP requirements for the remedial program, there
may be circumstances where it is desirable at CERCLA remedial sites to also consider
estimates of risk based on direct exposure rate measurements of penetrating radiation in
addition to risk estimates based on slope factors. Examples of such circumstances where
it may be appropriate to also use direct measurements for assessing risk from external
exposure to penetrating radiation include:
During early site assessment efforts when the site manager is attempting to
communicate the relative risk posed by areas containing elevated levels of
radiation,
As a real-time method for indicating that remedial objectives are being met
during the conduct of the response action. The use of exposure rate measurements
during the conduct of the response actions should not decrease the need for a
final status survey.
To facilitate developing risk estimates under any of these situations, EPA is developing a
Counts Per Minute (CPM) calculator (U.S. EPA 2014a) to model correlations in exposure
rate measurements back to modeled estimates of cancer risk. Direct radiation exposure rate
measurements may provide important indications of radiation risks at a site, particularly
during early investigations, when these may be the first data available. However, these data
may reflect only a subset of the radionuclides and exposure pathways of potential concern
(for example, only external exposure from gamma-emitting radionuclides in near-surface
soil), and may present an incomplete picture of site risks (such as risk from internal
exposures, or potential increased future risks from radionuclides in subsurface soils). In
most cases, more accurate estimation of radiation risks will require additional site
characterization data, including concentrations of all radionuclides of concern in all
pertinent environmental media. The principal benefit of using direct exposure rate
measurements is the speed and convenience of analysis, and reducing the potential for
missing areas of contamination. However, exposure rate data generally should
be used in conjunction with characterization data of radionuclides concentrations
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in environmental media to obtain a complete picture of potential site-related risks.
Exposure rate measurements scanned in the field should be correlated with samples
analyzed in a laboratory by collocating them to ensure that modeled assumptions
about the correlation between exposure rate and sample concentrations are
accurate. For a general discussion on radiation survey instruments, readers are directed to
Real-Time Measurement of Radionuclides in Soil: Technology and Case Studies document
(ITRC 2006), Real-Time Measurement of Radionuclides in Soil on-line training course
(ITRC 2008), Multi-Agency Radiation Survey and Site Investigation Manual (MARS SIM)
(U.S. EPA et al. Rev 1. 2000d) and Chapter 10 of RAGs Part A (U.S. EPA 1989a).
Q38. What radiation standards may be applicable or relevant and appropriate
requirements (ARARs)?
A. In some cases, cleanup levels may be derived based on site-specific risk assessments,
ARARs, and/or to-be-considered materials (TBCs). TBCs are non-promulgated
advisories or guidance issued by Federal or State governments that are not legally
binding and do not have the status of potential ARARs. However, TBCs will be
considered along with ARARs as part of the site risk assessment and may be used in
determining the necessary level of cleanup for protection of health and the environment.
Attachment A, "Likely Federal Radiation Applicable or Relevant and Appropriate
Requirements (ARARs)," of OSWERDirective 9200.4-18 (U.S. EPA 1997a) provides
information regarding the circumstances in which federal standards that have often been
selected as ARARs may be either applicable or relevant and appropriate for particular
site-specific conditions. The 1997 guidance (U.S. EPA 1997a) should be consulted
for further direction. For more general information ARARs and TBCs see the
CERCLA Compliance with Other Laws Manual (U.S. EPA 1989d).
OSWER Directive 9200.4-25, Use of Soil Cleanup Criteria in 40 CFR Part 192 as
Remediation Goals for CERCLA Sites (U.S. EPA 1998c), provides more detailed
discussion on the use of the concentration limits for radium and/or thorium in subsurface
soils.
V. ECOLOGICAL ASSESSMENTS
Q39. What guidance is available for conducting ecological risk assessments?
A. EPA is developing a Radiological Ecological Benchmark (REB) (U.S. EPA 2014b)
calculator that will be designed to develop concentrations protective of biota from
radioactivity at CERCLA sites. In addition, existing EPA guidance (OSWER Directive
9285.7-25, Ecological Risk Assessment Guidance for Superfund: Process for Designing
and Conducting Ecological Risk Assessments, U.S. EPA 1997e) is intended to facilitate
defensible and appropriately scaled site-specific ecological risk assessments at CERCLA
sites. This guidance is not intended to dictate the scale, complexity, protocols, data needs,
or investigation methods for such assessments. Professional judgment is required to
apply the process outlined in this guidance to ecological risk assessments at specific
sites. This guidance is supplemented by the guidance Ecological Risk Assessment and
Risk Management Principle for Superfund Sites (U.S. EPA 1999b). Typical exposure
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pathways for ecological risk assessments are in Figure 3. Each of the illustrations in
Figure 3 is expected to appear in the forthcoming guidance, together with explanatory
text in the user guide for the ecological calculator (U.S. EPA 2014b).
VI. BACKGROUND RADIATION
Q40. How should background levels of radiation be addressed?
A. Background radiation levels at a specific site generally should be determined the same way
background levels are determined for other contaminants: on a radionuclide and
site-specific basis when the same constituents are found in on-site samples as well as in
background samples. The levels of each constituent of potential concern at a site
typically are compared with background levels of those constituents to determine whether
site activities have resulted in elevated levels. For example, background levels for radium-
226 and radon-222 would generally not be relevant at a site if these radionuclides were
not site-related contaminants. Remedial site risk-based cleanup levels for individual
radionuclides generally are not set below site-specific background levels. When
background levels exceed the remedial risk range, background levels may be selected
as the cleanup levels. It should be noted that some ARARs specifically address how
to factor background into cleanup levels. For example, many radiation standards are
increments above background levels, while the indoor radon standards under 40 CFR
192.12(b)(1) are inclusive of background.
For further information regarding background, see the Role of Background in the
CERCLA Cleanup Program (U.S. EPA 2002b) and the section "Background
Contamination"in OSWER Directive 9200.4-18 (U.S. EPA 1997a).
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Figure 3. Typical Radionuclide Exposure Pathways for Biota
Aquatic Animals
I Internal Dose Pathways
|c = Exposure to radionuclides via
ingestion of contaminated
vegetation including water content
with dissolved nutrients and minerals
d - Exposure to radionuclides
biomagnified through the food web
Riparian Animals
Internal Dose Pathways
Ic - Exposure to radionuclides via
ingestion of contaminated
vegetation including water content
with dissolved nutrients and minerals
2 Exposure to radionuclides
biomagnified through the food web
Terrestrial Animals
Internal Dose Pathways
c = Exposure to radionuclides via ingestion of contaminated
vegetation, including water content with dissolved nutrients
and minerals
d = Exposure to radionuclides via ingestion of contaminated food
and soil, and via inhalation of soil
e = Exposure to radionuclides via ingestion of contaminated water
&
Aquatic Plants
1
External Dose Pathways
a = Exposure to radionuclides
in sediments
b = Exposure to radionuclides
I
Internal Dose Pathways
c = Exposure to radionuclides taken up
in water including dissolved
nutrients and minerals
Terrestrial Plants
External Dose Pathways
a = Exposure to radionuclides in soil
b = Exposure to radionuclides in water
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WHERE TO GO FOR FURTHER INFORMATION
Readers should periodically consult the EPA Superfund Radiation webpage for updates
on current guidance and for copies of new documents at this address:
http://www.epa. gov/superfund/health/contaminants/radiation/index.htm.
Radiation and radioactive materials pose special hazards and require specialized detection
instrumentation, techniques and safety precautions. EPA strongly encourages RPMs and
risk assessors to consult with individuals trained and experienced in radiation
measurements and protection. These individuals include health physicists and
radiochemists who can provide additional assistance in designing and executing
radionuclide sampling and analysis plans and interpreting radioanalytical results.
The subject matter specialist for this fact sheet is Stuart Walker of OSRTI. He can be reached
by e-mail at walker.stuart@epa.gov or by telephone at (703) 603-8748.
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International Commission on Radiological Protection (ICRP). 1977. Recommendations of the
ICRP. ICRP Publication 26. Pergamon Press, Oxford, UK.
International Commission on Radiological Protection (ICRP). 1979. Limits for Intakes of
Radionuclides by Workers. ICRP Publication 30. Pergamon Press, Oxford, UK.
International Commission on Radiological Protection (ICRP). 1989. Age-Dependent Doses to
Members of the Public from Intake of Radionuclides, Part 1. ICRP Publication 56. Pergamon
Press, Oxford, UK.
International Commission on Radiological Protection (ICRP). 1991. 1990 Recommendations of
the International Commission on Radiological Protection. ICRP Publication 60. Pergamon
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International Commission on Radiological Protection (ICRP). 1993. Age-Dependent Doses to
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International Commission on Radiological Protection (ICRP). 1995a. Age-Dependent Doses to
Members of the Public from Intake of Radionuclides, Part 3. ICRP Publication 69. Pergamon
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International Commission on Radiological Protection (ICRP). 1995b. Age-Dependent Doses to
Members of the Public from Intake of Radionuclides, Part 4. ICRP Publication 71. Pergamon
Press, Oxford, UK.
International Commission on Radiological Protection (ICRP). 2011. Lung Cancer Risk from
Radon and Progeny. ICRP Publication 115.
http://www.elsevier.com/wps/find/bookdescription.cws home/726672/description#description
Interstate Technology Regulatory Council (ITRC) 2006. Real-Time Measurement of Radionuclides
in Soil: Technology and Case Studies
http://www.itrcweb.org/Documents/RAD 4Web.pdf
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Tools
http://www.clu-in.org/conf/itrc/rads 051507/
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Interstate Technology Regulatory Council (ITRC) 2008a. Real-Time Measurement of
Radionuclides in Soil
http://www.clu-in.org/conf/itrc/radsrealtime 102808/
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of Radiologically-Contaminated Facilities
http://www.clu-in.org/conf/itrc/radsdd 040308/
National Academy of Sciences (NAS). 1980. The Effects on Populations of Exposure to Low
Levels of Ionizing Radiation: 1980. National Research Council, Committee on the Biological
Effects of Ionizing Radiation (BEIR III). National Academy Press, Washington, DC.
National Academy of Sciences (NAS). 1988. Health Effects of Radon and Other Internally
Deposited Alpha-Emitters National Research Council, Committee on the Biological Effects
of Ionizing Radiation (BEIR IV). National Academy Press., Washington, DC.
National Academy of Sciences (NAS). 1990. Health Effects of Exposure to Low Levels of
Ionizing Radiation. National Research Council, Committee on the Biological Effects of
Ionizing Radiation (BEIR V). National Academy Press., Washington, DC.
National Academy of Sciences (NAS). 1999. Health Effects of Exposure to Radon. National
Research Council, Committee on the Health Effects of Exposure to Radon (BEIR VI).
National Academy Press., Washington. DC.
http://books.nap.edu/openbook.php?isbn=0309056454
National Council on Radiation Protection and Measurements (NCRP). 1976. Environmental
Radiation Measurements. NCRP Report No. 50. Bethesda, MD.
National Council on Radiation Protection and Measurements (NCRP). 1978. Instrumentation
andMonitoring Methods for Radiation Protection. NCRPReportNo. 57. Bethesda, MD.
National Council on Radiation Protection and Measurements (NCRP). 1987. Exposure of the
Population in the United States and Canada from Natural Background Radiation. NCRP
Report No. 94. Bethesda, MD.
Stewart, R, N. and S. T. Purucker. 2011. "An Environmental Decision Support System for
Spatial Assessment and Selective Remediation," Environmental Modeling & Software
26(6): 751-760.
http: // www .sadaproiect.net/
United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 1988.
Sources, Effects and Risks of Ionizing Radiation. United Nations, NY.
United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 2006.
Effects of Ionizing Radiation. Volume II: Scientific Annexes C, D, andE. United Nations, NY.
http://www.unscear.org/unscear/en/publications/2006 2.html
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U.S. EPA. 1980. Upgrading Environmental Data: Health Physics Society Committee Report
HPSR-1 (1980). Office of Radiation Programs, Washington, DC.
U.S. EPA. 1984. EERF Radiochemistry Procedures Manual. EPA 520/5-84-006. Office of
Radiation Programs, Eastern Environmental Radiation Facility, Montgomery, AL.
U.S. EPA. 1988a. Guidance for Conducting Remedial Investigations and Feasibility Studies
under CERCLA. EPA/540/G-89/004. Office of Radiation Programs, Washington, DC.
http: //rai s. ornl. gov/documents/GUIDANCE. PDF
U.S. EPA. 1988b. Limiting Values of Radionuclide Intake and Air Concentration and Dose
Conversion Factors for Inhalation, Submersion, and Ingestion: Federal Guidance Report
No. 11. EPA-520/1-88/020. Office of Radiation Programs, Washington, DC.
http://www.epa.gov/rpdweb00/docs/federal/520-l-88-02Q.pdf
U.S. EPA. 1989a. Risk Assessment Guidance for Superfund, Volume 1: Human Health
Evaluation Manual, Part A, Interim Final. EPA/540/1-89/002. Office of Emergency and
Remedial Response, Washington, DC. NTIS PB90-155581/ CCE.
http://www.epa.gov/oswer/riskassessment/ragsa/pdf/rags-voll-pta complete.pdf
U.S. EPA. 1989b. Methods for Evaluating the Attainment of Soil Cleanup Standards. Volume 1:
Soils and Solids. EPA/540/1-89/003. Statistical Policy Branch, Office of Policy, Planning, and
Evaluation, Washington, DC.
http://www.clu-in.org/download/stats/vollsoils.pdf
U.S. EPA. 1989c. Risk Assessment Methodology: Environmental Impact Statement-NESHAPs
for Radionuclides, Background Information Document-Volume 1. EPA-520/1-89-006-1.
Office of Radiation Programs, Washington, DC.
http://www.epa.gov/rpdwebOO/docs/neshaps/subpart-w/historical-rulemakings/risk-
assessments-methodology-eis-neshaps-for-radionuclides.pdf
U.S. EPA. 1989d. Exposure Factors Handbook. EPA/600/8-89/043. Office of Health and
Environmental Assessment, Washington, DC.
http://rais.ornl.gov/documents/EFH 1989 EPA600889043.pdf
U.S. EPA. 1989e. CERCLA Compliance with Other LawsManual: Interim Final. EPA/540/G-
89/006. Office of Emergency and Remedial Response, Washington, DC.
http://www.epa.gov/superfund/policv/remedv/pdfs/540g-89006-s.pdf
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U.S. EPA. 1991a. Risk Assessment Guidance for Superfund, Volume 1: Human Health
Evaluation Manual (Part B, Development of Risk-Based Preliminary Remediation Goals).
Publication 9285.7-OIB. Office of Emergency and Remedial Response, Washington, DC.
NTIS PB92-963333.
http://www.epa.gov/oswer/riskassessment/ragsb/index.htm
U.S. EPA. 1991b. Risk Assessment Guidance for Superfund, Volume 1: Human Health
Evaluation Manual (Part C, Risk Evaluation of Remedial Alternatives). Interim. OSWER
Directive 9285.7-01C. Office of Emergency and Remedial Response, Washington, DC.
http://www.epa.gov/oswer/riskassessment/ragsc/index.htm
U.S. EPA. 1991c. Human Health Evaluation Manual, Supplemental Guidance: Standard Default
Exposure Factors. OSWER 9285.6-03. Office of Emergency and Remedial Response,
Washington, DC. NTIS PB91-921314.
http://epa-prgs.ornl.gov/chemicals/help/documents/OSWERdirective9285.6-03.pdf
U.S. EPA. 199 Id. Role of the Baseline Risk Assessment in Superfund Remedy Selection
Decisions. OSWER Directive 9355.0-30. Office of Solid Waste and Emergency Response.
http://www.epa.gov/oswer/riskassessment/pdf/baseline.pdf
U.S. EPA. 1992a. Statistical Methods for Evaluating the Attainment of Cleanup Standards-
Volume 2: Groundwater. Draft. Statistical Policy Branch, Office of Policy, Planning, and
Evaluation, Washington, DC.
http://www.clu-in.org/download/stats/vol2gw.pdf
U.S. EPA. 1992b. Statistical Methods for Evaluating the Attainment of Cleanup Standards-
Volume 3: Reference-Based Standards for Soils and Solid Media. PB94 176831. Statistical
Policy Branch, Office of Policy, Planning, and Evaluation, Washington, DC.
http://www.epa.gov/tio/download/stats/vol3-refbased.pdf
U.S. EPA. 1992c. Guidance for Data Usability in Risk Assessment (Part A). Publication
9285.7A. Office of Emergency and Remedial Response, Washington, DC.
http://www.epa.gov/oswer/riskassessment/datause/pdf/datause-parta.pdf
U.S. EPA. 1992d. Guidance for Data Usability in Risk Assessment (Part B). Publication
9285.78. Office of Emergency and Remedial Response, Washington, DC.
http://www.epa.gov/oswer/riskassessment/datause/pdf/datause-partb.pdf
U. S. EPA. Implementing the Deputy Administrator's Risk Characterization Memorandum.
Memorandum from H.L. Longest, Director of Office of Emergency and Remedial
Response, Washington, DC, 5/26/92.
http://www.epa.gov/oswer/riskassessment/pdf/1992 0526 risk characterization memo.pdf
U.S. EPA. 1993a. Data Quality Objectives for Superfund, Interim Final Guidance. EPA 504-R-
93/071. Office of Emergency and Remedial Response, Washington, DC.NTIS PB94-963203.
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U.S. EPA. 1993b. External Exposure to Radionuclides in Air, Water, and Soil: Federal
Guidance Report No. 12. EPA-402-R-93-081. Office of Air and Radiation, Washington, DC.
http://www.epa.gov/rpdweb00/docs/federal/402-r-93-081.pdf
U.S. EPA. 1994a. Guidance for the Data Quality Objectives Process. EPA QA/G4. Office of
Research and Development.
http://www.epa.gov/osw/hazard/correctiveaction/resources/guidance/qa/epaqag4.pdf
U.S. EPA. 1994b. Estimating Radiogenic Cancer Risks. EPA 402-R-93-076. Office of Radiation
and Indoor Air, Washington, DC.
http://www.epa.gov/rpdweb00/docs/assessment/402-r-93-076.pdf
U.S. EPA. 1995a. EPA Risk Characterization Program. Memorandum from CarolBrowner, Office
of the Administrator, Washington, DC, 3/21/95.
http://www.epa.gov/oswer/riskassessment/pdf/1995 0521 risk characterization program.pd
f
U.S. EPA. 1995b. Guidance for Risk Characterization. Science Policy Council, February 1995.
http://www.epa.gov/spc/pdfs/rcguide.pdf
U.S. EPA. 1996. Radiation Exposure and Risk Assessment Manual: Risk Assessment Using
Radionuclide Slope Factors. EPA 402-R-96-016, Office of Radiation and Indoor Air,
Washington, DC, June 1996.
U.S. EPA. 1997a. Establishment of Cleanup Levelsfor CERCLA Sites with Radioactive
Contamination, OSWERNo. 9200.4-18, August 22, 1997.
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/radguide.pdf
U.S. EPA. 1997b. Exposure Factors Handbook (Update). EPA/600/P-95/002F. Office of
Research and Development, Washington, DC, August 1997.
U.S. EPA. 1997c. Use of Probabilistic Techniques (Including Monte Carlo Analysis) in Risk
Assessment, Memorandum from Deputy Administrator Hansen, August 1997.
http://www.epa.gov/spc/pdfs/probcovr.pdf
U.S. EPA. 1997d. Guiding Principles for Monte Carlo Analysis, EPA/63 0/R-97-001.
http://www.epa.gov/ncea/pdfs/montcarl.pdf
U.S. EPA. 1997e. Ecological Risk Assessment Guidance for Superfund: Process for Designing
and Conducting Ecological Risk, OSWER Directive 9285.7-25,
http://www.epa.gov/oswer/riskassessment/ecorisk/pdf/intro.pdf
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U.S. EPA. 1997f. Clarification of the Role of Applicable, or Relevant and Appropriate
Requirements in Establishing Preliminary Remediation Goals under CERCLA, OSWERNo.
9200.4-23, August 22, 1997.
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/aras.pdf
U.S. EPA. 1997g. Memorandum from James E. Woolford, Office of Restoration and Reuse, and
Stephen D. Luftig, Office of Emergency and Remedial Response, Washington, DC. to
Raymond P. Berube, U.S. Department of Energy. 12/12/1997.
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/EPA1997g.pdf
U.S. EPA. 1998a. Risk Assessment Guidance for Superfund, Volume 1: Human Health
Evaluation Manual, Part D, Standardized Planning, Reporting, and Review of Superfund
Risk Assessments. Publication 9285.7-01D. NTIS PB97-963305. Office of Emergency and
Remedial Response, Washington, DC.
http://www.epa.gov/oswer/riskassessment/ragsd/index.htm
U.S. EPA. 1998b. Risk Assessment Guidance for Superfund, Volume 1: Human Health
Evaluation Manual, Part E, Supplemental Guidance to RAGS: The Use of Probabilistic
Analysis in Risk Assessment. (Working Draft). Office of Emergency and Remedial
Response, Washington, DC.
http://www.epa.gov/oswer/riskassessment/ragse/index.htm
U.S. EPA. 1998c. Use of Soil Cleanup Criteria in 40 CFRPart 192 as Remediation Goals for
CERCLA Sites, OSWER Directive No. 9200.4-25, February 1998.
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/umtrcagu.pdf
U.S. EPA. 1998e. Integrated Risk Information System (IRIS). Cincinnati, OH.
http://www.epa.gov/IRIS/
http://www.epa.gov/rpdwebOO/heast/index.html
U.S. EPA. 1998f. Health Effects Summary Tables (HEAST); Annual Update, FY1998.
Environmental Criteria and Assessment Office, Office of Health and Environmental
Assessment, Office of Research and Development, Cincinnati, OH.
http://cfpub.epa. gov/ncea/cfm/recordisplav.cfm?deid=2877
U.S. EPA. 1999a. Radiation Risk Assessment at CERCLA Sites: Q&A, Office of Emergency and
Remedial Response and Office of Radiation and Indoor Air. Washington, DC. OSWER
Directive 9200.4-3 IP,
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/riskqa.pdf
U.S. EPA. 1999b. Ecological Risk Assessment and Risk Management Principle for Superfund
Sites, OSWER Directive 9285.7-28P,
http://www.epa.gov/oswer/riskassessment/ecorisk/pdf/final99.pdf
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U.S. EPA. 1999c. Cancer Risk Coefficients for Environmental Exposure to Radionuclides:
Federal Guidance Report No. 13. EPA 402-R-99-001. Office of Air and Radiation,
Washington, DC.
http://www.epa.gOv/radiation/federal/techdocs.html#reportl3
U.S. EPA. 1999d. Distribution of OSWER Radiation Risk Assessment at CERCLA Sites Q&A
Final Guidance, Memorandum from Stephen D. Luftig, Office of Emergency and
Remedial Response and Stephen D. Page, Office of Radiation and Indoor Air.
Washington, DC. 12/ 17/1999
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/EPA1999d.pdf
U.S. EPA. 2000a. Soil Screening Guidance for Radionuclides: User's Guide. Office of
Emergency and Remedial Response and Office of Radiation and Indoor Air. Washington,
DC. OSWER No. 9355.4-16A
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/ssuserguide.pdf
U.S. EPA. 2000b. Soil Screening Guidance for Radionuclides: Technical Background
Document. Office of Emergency and Remedial Response and Office of Radiation and
Indoor Air. Washington, DC. OSWER No. 9355.4-16
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/sstbd.pdf
U.S. EPA. 2000c. Guidance for Data Quality Assessment. EPA QA/G9. Quality Assurance
Management Staff, Office of Research and Development, Washington, DC. EPA/600/R-
96/084
http://www.clu-in.org/conf/tio/pasi 121603/g9-final.pdf
U.S. EPA, NRC, U.S. DOE, and U.S. Department of Defense. 2000d. Multi-Agency Radiation
Survey and Site Investigation Manual (MARSSIM). NUREG-1575, EPA 402-R-97-016,
Rev.l Washington, DC.
http://www.epa.gov/radiation/marssim/obtain.html
U.S. EPA. 2000e. Soil Screening Guidance for Radionuclides electronic calculator.
http://rais. ornl. gov/rad start, shtml
U.S. EPA. 2000f. Memorandum from Robert Perciasepe, Office of Air and Radiation and
Timothy Fields, Jr. Office of Solid Waste and Emergency Response, Washington, DC. to
Charles M. Hardin, Conference of Radiation Control Program Directors. 7/7/2000
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/EPA2000f.pdf
U.S. EPA. 2002a Radionuclide Preliminary Remediation Goals (PRGs) for Superfund
electronic calculator.
http://epa-prgs.ornl.gov/radionuclides/
U.S. EPA. 2002b Role of Background in the CERCLA Cleanup Program. Office of Emergency
and Remedial Response. OSWER 9285.6-07P
http://www.epa.gov/oswer/riskassessment/pdf/bkgpol ianOl.pdf
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U.S. EPA. 2002c Simulating Radionuclide Fate and Transport in the Unsaturated Zone:
Evaluation and Sensitivity Analyses of Select Computer Models
http://www.epa.gov/nrmrl/pubs/600r02082/600R02Q82-full.pdf
U.S. EPA 2003. World Trade Center Indoor Environmental Assessment: Selecting
Contaminants of Potential Concern and Setting Health-Based Benchmarks. Prepared by
the Contaminants of Potential Concern (COPC) Committee of the World Trade Center
Indoor Air Task Force Working Group.
http://www.epa.gov/wtc/copc benchmark.pdf
U.S. EPA. 2004a Radionuclide ARAR Dose Compliance Concentrations (DCCs) for Superfund
electronic calculator.
http://epa-dccs.ornl.gov/
U.S. EPA, NRC, U.S. DOE, and U.S. Department of Defense. 2004b. Multi-Agency Radiation
Laboratory Analytical Protocols (MARLAP). Washington, DC.
http://www.epa.gOv/rpdweb00/marlap/manual.html#voli chaps
U.S. EPA. 2004c. Distribution of OSWER Radionuclide ARAR Dose Compliance Concentrations
(DCCs) for Superfund Electronic Calculator. OSWER 9355.0-86A, January 28, 2004.
http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/dccmemo.pdf
U.S. EPA. 2005 a. Superfund Radiation Risk Assessment and How You Can Help: An Overview.
http://www.epa.gov/superfund/health/contaminants/radiation/radvideo.htm
U.S. EPA. 2005b. Uniform Federal Policy for Implementing Environmental Quality Systems:
Evaluating, Assessing, and Documenting Environmental Data Collection/Use and
Technology Programs. EPA: EPA-505-F-03-001, DoD: DTIC ADA 395303, DOE:
DOE/EH-0667, Version 2 Washington, DC.
http://www.epa.gov/superfund/health/contaminants/radiation/radvideo.htm
U.S. EPA. 2006. Inventory of Radiological Methodologies for Sites Contaminated with Radioactive
Materials. EPA 402-R-06-007 October 2006
http ://www. epa. gov/narel/IRM Final .pdf
U.S. EPA 2007. Preliminary Remediation Goals for Radionuclides in Buildings (BPRG)
electronic calculator.
http ://epa-bprg.ornl. gov/
U.S. EPA 2008. Regional Screening Levels for Chemical Contaminants at Superfund Sites
(RSL) electronic calculator.
http://www.epa.gov/reg3hwmd/risk/human/rb-concentration table/index.htm
U.S. EPA 2009a. Preliminary Remediation Goals for Radionuclides in Outdoor Surfaces
(SPRG) electronic calculator.
http://epa-sprg.ornl.gov/
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U.S. EPA, NRC, U.S. DOE, and U.S. Department of Defense. 2009b. Multi-Agency Radiation
Survey and Assessment of Materials and Equipment Manual (MARSAME). NUREG-
1575, Supp. 1, EPA 402-R-09-001, Washington, DC.
http://www.epa.gov/rpdwebOO/marssim/marsame.html
U.S. EPA 2010a. ARAR Dose Compliance Concentrations Goals for Radionuclides in
Buildings (BDCC) electronic calculator.
http://epa-bdcc.ornl.gov/
U.S. EPA 2010b. ARAR Dose Compliance Concentrations Goals for Radionuclides in
Buildings (SDCC) electronic calculator.
http://epa-sdcc.ornl.gov/
U.S. EPA 2014a. Draft Counts Per Minute (CPM) electronic calculator.
U.S. EPA 2014b. Draft Ecological Benchmarks for Radionuclides electronic calculator.
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APPENDIX A:
EPA's Recommended Guidance for
Radiation Risk Assessment at CERCLA Remedial Sites
The Preliminary Remediation Goals (PRGs) for Radionuclides electronic calculator, known
as the Rad PRG calculator (U.S. EPA 2002a). This electronic calculator presents risk-based
standardized exposure parameters and equations that should be used for calculating
radionuclide PRGs for residential, commercial/industrial, agricultural, tap water, and fish
ingestion exposures. The calculator also presents soil PRGs that protect groundwater, which
are determined by calculating the concentration of radioactively contaminated soil subject to
leaching to groundwater that will meet maximum contaminant levels (MCLs) or risk-based
concentrations.
Th q Building Preliminary Remediation Goals for Radionuclides (BPRG) electronic calculator
(U.S. EPA 2007). The BPRG calculator helps standardize the evaluation and cleanup of the
interiors of radiologically contaminated buildings where risk is being assessed for occupancy.
BPRGs are radionuclide concentrations in dust, air, and building materials that correspond to
a specified level of human cancer risk.
The Radionuclide Outdoor Surfaces Preliminary Remediation Goals (SPRG) electronic
calculator (U.S. EPA 2009a). The SPRG calculator was developed to address radionuclide
concentrations in dust on and within hard outside surfaces such as building slabs, outside
building walls, sidewalks, and roads.
Soil Screening Guidance for Radionuclides contains both a User's Guide and Technical
Background Document, (known as the Rad SSG documents) that provide information on soil
screening for radionuclides at CERCLA sites (U.S. EPA 2000a, 2000b). The risk assessment
equations and the soil screening levels (SSLs) in this guidance have been superseded by the
Rad PRG calculator;
ARAR Dose Compliance Concentrations for Radionuclides (DCC) electronic calculator (U.S.
EPA 2004a). The DCC calculator equations are identical to those in the PRG for
Radionuclides, except that the applicable or relevant and appropriate requirement (ARAR)
based target dose rate (in millirems per year or mrem/yr) is substituted for the target cancer
risk (1 x 10"6), the period of exposure is 1 year to indicate year of peak dose, and a Dose
Conversion Factor (DCF) is used in place of the slope factor. The DCC calculator presents
standardized exposure parameters and equations that should be used for calculating
radionuclide DCCs for residential, commercial/industrial, agricultural, tap water, and fish
ingestion exposures.
ARAR Dose Compliance Concentrations for Radionuclides in Buildings (BDCC) electronic
calculator (U.S. EPA 2010a), known as the BDCC calculator, was developed to present
standardized exposure parameters and equations that should generally be used for calculating
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radionuclide BDCCs for interiors of contaminated buildings with either a residential or a
commercial/industrial use.
ARAR Radionuclide Outdoor Surfaces Dose Compliance Concentrations for Radionuclides
(SDCC) electronic calculator (U.S. EPA 2010b), known as the SDCC calculator, was
developed to present standardized exposure parameters and equations that should generally be
used for calculating radionuclide SDCCs for outside hard surfaces (such as building slabs,
outside building walls, sidewalks, and roads) with either a residential or a
commercial/industrial use.
Chapter 10, "Radiation Risk Assessment Guidance" of RAGS Part A (U.S. EPA 1989a)
which covers data collection and evaluation, exposure and dose assessment, toxicity
assessment, and risk characterization for sites contaminated with radioactive substances.
Chapter 4, "Risk-based PRGs for Radioactive Contaminants," of RAGS Part B (U.S. EPA,
1991a) which presents standardized exposure parameters and equations that should generally
be used for calculating PRGs for radionuclides under residential and commercial/industrial
land use exposure scenarios. This guidance has been superseded by the PRG, BPRG, and
SPRG calculators.
Appendix D, "Radiation Remediation Technologies," of RAGS Part C (U.S. EPA 1991b),
which provides guidance on using risk information to evaluate and select remediation
technologies for sites with radioactive substances.
RAGS Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessments
(U.S. EPA, 1998a), which provides guidance on standardized risk assessment planning,
reporting, and review throughout the CERCLA process.
Superfund Radiation Risk Assessment and How You Can Help: An Overview (U.S. EPA,
2005a) is a video that explains to the public the Superfund risk assessment process and how
the public can help inform the risk assessment process.
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