UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
DEC 1 7 1999
MEMORANDUM
SUBJECT: Dis
FROM:
iation Risk Assessment Q & A's Final Guidance
TO:
PURPOSE
Office of Air and Radiation
Addressees
rgency an<8 Remedial Response (OERR)
ste and Emergency Response
Director
ionand Indoor Air (ORIA)
The purpose of this memorandum is to transmit to you a final guidance document entitled:
"Radiation Risk Assessment At CERCLA Sites: Q & A." The guidance provides answers to several
common questions about radiation risk assessments at CERCLA sites. It should be especially useful
to Remedial Project Managers (RPMs), On-Scene Coordinators (OSCs), and risk assessors.1
BACKGROUND
The U.S. Environmental Protection Agency (EPA) issued guidance entitled "Establishment
of Cleanup Levels for CERCLA Levels for CERCLA Sites with Radioactive Contamination"
(OSWER No. 9200.4-18, August 22, 1997). This 1997 guidance provided clarification for
establishing protective cleanup levels for radioactive contamination at Comprehensive
Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) sites. The 1997
guidance reiterated that cleanups of radionuclides are governed by the risk range for all carcinogens
established in the NCP when ARARs are not available or are not sufficiently protective. Cleanup
should generally achieve a cumulative risk within the 10"4 to 10"6 carcinogenic risk range based on
the reasonable maximum exposure. The cleanup levels should consider exposures from all potential
The attached document provides guidance on risk assessment issues involved at CERCLA sites and is
consistent with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). It does not alter the
NCP expectations 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, response actions must attain or waive Applicable or
relevant and appropriate requirements (ARARs). CERCLA response actions for contaminated ground water at radiation
sites must attain (or waive as appropriate) the Maximum Contaminant Levels (MCLs) or non-zero Maximum
Contaminant Level Goals (MCLGs) established under the Safe Drinking Water Act, where the MCLs or MCLGs are
relevant and appropriate for the site.
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pathways, and through all relevant media (e.g., soil, ground water, surface water, sediment, air,
structures, etc.) The 1997 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.
Since issuance of the 1997 guidance, regional staff have requested additional guidance on
specific Superfund process and requirements related to radiation cleanups. Today's guidance
responds to these requests.
The attached final Risk Q & A fact sheet is part of a continuing effort between the Office of
Emergency and Remedial Response (OERR) and the Office of Radiation and Indoor Air (ORIA) to
provide updated guidance for addressing radioactively contaminated sites that is consistent with our
guidance for addressing chemically contaminated sites, except to account for the technical
differences between radionuclides and chemicals. This effort is intended to facilitate compliance
with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) at radioactively
contaminated sites while incorporating the improvements to the Superfund program that have been
implemented through Administrative Reforms.
Two issues addressed in this Risk Q & A should be noted here. First, the answer to question
32 in the Risk Q & A is intended to further clarify that 15 millirem per year is not a presumptive
cleanup level under CERCLA, but rather site decision-makers should continue to use the risk range
when ARARs are not used to set cleanup levels. There has been some confusion among stakeholders
regarding this point because of language in the 1997 guidance. EPA is issuing further guidance
today to site decision makers on this topic. This Risk Q&A clarifies that, in general, dose
assessments should only be conducted under CERCLA where necessary to demonstrate ARAR
compliance. Further, dose recommendations (e.g., guidance such as DOE Orders and NRC
Regulatory Guides) should generally not be used as to-be-considered material (TBCs). Although
in other statutes EPA has used dose as a surrogate for risk, the selection of cleanup levels for
carcinogens for a CERCLA remedy is based on the risk range when ARARs are not available or
are not sufficiently protective. Thus, in general, site decision-makers should not use dose-based
guidance rather than the CERCLA risk range in developing cleanup levels. This is because for
several reasons, using dose-based guidance would result in unnecessary inconsistency regarding how
radiological and non-radiological (chemical) contaminants are addressed at CERCLA sites. These
reasons include: (1) estimates of risk from a given dose estimate may vary by an order of magnitude
or more for a particular radionuclide, and; (2) dose based guidance generally begins an analysis for
determining a site-specific cleanup level at a minimally acceptable risk level rather than the 10"6
point of departure set out in the NCP.
Second, it is important that data that support remedial decisions be of known and acceptable quality.
There are a number of EPA guidances available that may aid the decision maker in gathering data
of acceptable quality. One such guidance is the Multi-Agency Radiation Survey and Site
Investigation Manual (MARSSIM). The determination of what data are needed is a site-specific
decision and it is the responsibility of the site decision-maker (e.g., RPM, OSC) to use the tools that
are most appropriate for that situation.
-2-
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IMPLEMENTATION
For questions regarding radiation site policy and guidance for CERCLA cleanup actions,
readers are referred to the RCRA/Superfund Hotline at 1-800-424-9346. The subject matter
specialists for this fact sheet are Stuart Walker of OERR and Dr. Kung-Wei Yeh of ORIA.
Attachments
Addressees:
National Superfund Policy Managers
Superfund Branch Chiefs (Regions I-X)
Superfund Branch Chiefs, Office of Regional Counsel (Regions I-X)
Radiation Program Managers (Regions I, IV, V, VI, VII, X)
Radiation Branch Chief (Region n)
Residential Domain Section Chief (Region in)
Radiation and Indoor Air Program Branch Chief (Region VIII)
Radiation and Indoor Office Director (Region IX)
Federal Facilities Leadership Council
OERR Center Directors
cc
Jim Woolford, FFRRO
Elizabeth Cotsworth, OSW
Craig Hooks, FFEO
Barry Breen, OSRE
Joanna Gibson, HOSC/OERR
Earl Salo, OGC
Bob Cianciarulo, Region I
-3-
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^ico sj^, United States Office of
„•* ^^ *^ Environmental Protection Agency Emergency and
£ ^^* 4 Remedial Response
Office of Directive 9200.4-31 P
Radiation and EPA 540/R/99/006
Indoor Air December 1999
%% PR^&<^ 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.
INTRODUCTION
Some sites on the U.S. Environmental Protection Agency's
National Priorities List (NPL) are radioactively contaminated. To
assist in the evaluation and cleanup of these sites and surrounding
areas under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA or Superfund), EPA's
Office of Emergency and Remedial Response (OERR) and the
Office of Radiation and Indoor Air (ORIA) have developed
guidance for conducting radiation risk assessments during the
remedial investigation/feasibility study (RI/FS) process. This
guidance is provided primarily in the multi-part document, Risk
Assessment Guidance for Superfund, Volume I, Human Health
Evaluation Manual (RAGS). Guidance specific to radiation risk
includes:
• Chapter 10, "Radiation Risk Assessment Guidance," of
RAGSPart 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;
• Chapter4, "Risk-based PRGs for Radioactive Contaminants,"
of RAGS Part B (U.S. EPA, 199 la) which presents standard-
ized exposure parameters and equations that should generally
be used for calculating preliminary remediation goals (PRGs)
forradionuclidesunder residential and commercial/industrial
land use exposure scenarios [the equations for residential
land use will be updated shortly with a new soil screening
guidance for radionuclides (U.S. EPA, 1998d)];
• 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; and
• RAGSPart 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
(Radionuclides Worksheet to be developed).
In addition to RAGS, EPA has published several other guidance
documents and OSWER Directives concerning risk assessment
methods for radioactive and nonradioactive contaminants.
Attachment 1 presents a bibliography of selected Agency
guidance documents on risk assessment. OSWER Directives
specific to radioactive contaminants include:
• OSWERNo. 9200.4-18, Establishmentof'Cleanup Levelsfor
CERCLA Sites with Radioactive Contamination (U.S. EPA
1997a), which provides guidance for establishing protective
cleanup levels for radioactive contamination at CERCLA
sites; and
• OSWER No. 9200.4-25, Use of Soil Cleanup Criteria in 40
CFR Part 192 as Remediation Goals for CERCLA Sites (U.S.
EPA 1998c), which provides guidance regarding the circum-
stances under which the subsurface soil cleanup criteria in 40
CFR Part 192 should be considered an applicable or relevant
and appropriate requirement (ARAR) for radium or thorium
in developing a response action under CERCLA.
Overall, the process for assessing radionuclide exposures and
radiation risks presented in RAGS and in supplemental guidance
documents parallels the process for assessing risks from chemical
exposures. Both types of assessments follow the same four-step
evaluationprocess(exposure assessment, toxicity assessment, risk
characterization, ecological assessments) , consider similar
exposure scenarios and pathways (except the external "direct
exposure" pathway which is unique to radiation), determine
exposure point concentrations, and provide estimates of cancer
risks to humans.
However, several aspects of risk assessment for radioactive
contaminants do differ substantially from those considered for
chemical contaminants. Occasionally these differences—in
measurement units, exposure terms and concepts, field and
laboratory procedures and detection limits, and toxicity criteria,
among others—have led to questions concerning the Agency's
recommended approach for addressing radionuclide contamina-
tion and risk and the cleanup of CERCLA radiation sites.
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PURPOSE
OERR and ORIA have prepared this document to provide
answers to several commonly asked questions regarding risk
assessments at radioactively contaminated CERCLA sites raised
by Remedial Project Managers (RPMs), On-Scene Coordinators
(OSCs), risk assessors, Federal, State and local agencies,
potentially responsible parties (PRPs), and contractors. Its
purpose is to provide an overview of current EPA guidance for
risk assessment and related topics for radioactively contaminated
CERCLA sites. Guidance issued by other organizations (e.g.,
NRC, DOE, ICRP, NCRP) may provide technical assistance,
however the reader should exercise caution since some of these
documents utilize a framework for risk management (e.g.,
allowable dose limits of 25, 100, or 500 mrem/yr) that EPA has
determined is not suitable for use at CERCLA 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
In addition, a bibliography of selected reference materials related
to radiation risk assessment is provided in Attachment 1.
Readers are strongly encouraged to direct all questions concern-
ing site-specific evaluations involving radioactive contaminants
to the EPA Regional Radiation Program Office or Regional
Superfund Office in the EPA Region in which their site is located.
EPA has found that early involvement of the Regional Radiation
Program and Superfund staff in all phases of site characterization
and cleanup improves and expedites the entire process.
For general questions on, or assistance with, radiation surveys or
radioanalytical procedures, readers are directed to EPA's
National Air and Radiation Environmental Laboratory (NAREL)
in Montgomery, AL, or Radiation and Indoor Environments
National Laboratory (RIENL) in Las Vegas, NV. For questions
regarding radiation site policy and guidance, readers are also
referred to the RCRA/Superfund Hotline at 1-800-424-9346. The
subject matter specialists for this fact sheet are Dr. Kung-Wei Yeh
of ORIA and Stuart Walker of OERR.
I. DATA COLLECTION AND EVALUATION
Ql. What strategy and key information should be consid-
ered during the initial planning stage for radiological
data collection?
A. The Data Quality Objectives (DQO) process is an impor-
tant 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) and Data Quality Objectives for
Superfundr(U. S. EPA, 1993 a). Additional guidance on the
application of this process at radiation sites can be found
in the Multi-Agency Radiation Survey and Site Investiga-
tion Manual (MARSSIM) (U.S. EPA et al. 1997). The
DQO process outlined in these documents should be
completed during the initial planning stage for data
collection.
At a minimum, site characterization should include the
following key information and considerations:
• 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
• 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 and exposure
pathways
identify potential human and ecological receptors
focus initial surveys and sampling and analysis plans
• 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
• specify cleanup levels or develop preliminary remedia-
tion goals
• establish DQOs
The MARSSIM (U.S. EPA et al. 1997) provides guidance on
planning, implementing, and evaluating radiological site surveys.
This multi-agency consensus document was developed collabor-
atively by the four Federal Agencies having authority and control
over radioactive materials: the Department of Defense (DoD),
Department of Energy (DOE), EPA, and the Nuclear Regulatory
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Commission (NRC). While the primary focus of MARSSIM is
on final status surveys to demonstrate compliance with dose- or
risk-based criteria, guidance is also provided for designing and
conducting scoping and characterizing surveys, based on the
DQO process.
Q2. How should a list of radionuclides of concern be con-
structed?
A. An initial list of radionuclides of potential concern should
be based on a review of previous site operations that
contributed to the current levels of contamination and the
conceptual site model. As a first consideration, all radio-
nuclides used or produced at the site should be included on
the list. If 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.
However, before a short-lived radionuclide is excluded
from the list, 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.
Site characterization efforts should be directed to confirm-
ing or refuting the presence of the radionuclides of concern
in on-site sources and in environmental media contami-
nated by releases migrating off-site. The activity concen-
trations of radionuclides (and decay products, if appropri-
ate) 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), PRGs, screening
levels, or potential remediation criteria (see Q3). Caution
should be exercised in making such 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.
Q3. What criteria should be used to determine areas of
radioactive contamination or radioactivity releases?
A. Section 7 of EPA's revised Hazard Ranking System (HRS)
(see Appendix A to 40 CFR Part 300) provides general
criteria for comparing concentrations of radionuclides in
sources and various environmental media against back-
ground levels for use in screening sites for inclusion on the
NPL. Table 1 presents a summary of the HRS criteria for
establishing observed radiological contamination or
observed releases of radioactive materials; key consider-
ations include the measurement of radionuclide concentra-
tions significantly above site-specific background levels.
General guidance is provided in the following Agency
documents:
• Methods for Evaluating the Attainment of Cleanup
Standards—Volume 1: Soil and Soil Media (U.S. EPA,
1989b)
• Statistical Methods for Evaluating the Attainment of
Cleanup Standards—Volume 2: Ground Water (U.S.
EPA, 1992a)
• Statistical Methods for Evaluating the Attainment of
Cleanup Standards—Volume 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. More
specific guidance for the measurement and evaluation of
radiological contaminants is provided in the MARSSIM
(U.S. EPAetal. 1997); MARS SIM also provides guidance
on the determination of site-specific background levels for
comparison to site measurements. Additional guidance
regarding soil screening levels (SSLs) for radionuclides is
currently under development (U.S. EPA 1998d). The
SSLs are not cleanup standards, but may be used to
identify areas that may require further investigation at NPL
sites. The SSL equations should also be used to establish
PRGs for residential land use where ARARs are not
available or sufficiently protective. For additional guid-
ance on this issue, readers should contaci the appropriate
EPA Regional Radiation Program Office or Regional
Superfund Office, as appropriate, or ORIA-HQ.
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Table 1. EPA's Hazard Ranking System Criteria for Establishing Radionuclide Contamination/Releases*
Based on:
Direct Observation
Analysis of
Radionuclide
Concentrations in
Samples (ground
water, soil, air,
surface water,
benthic, or sediment
samples)
Gamma Radiation
Exposure Rate
Measurements
Criteria for Establishing Observed Contamination or Observed Releases of Radionuclides
Applies to All Radionuclides
(I) For each migration pathway, a material that contains one or more radionuclides has been seen entering the
atmosphere, surface water, or ground water, as appropriate, or is known to have entered ground water or surface
water through direct deposition, or
(ii) For the surface water migration pathway, a source area containing radioactive substances has been flooded at a
time that radioactive substances were present and one or more radioactive substances were in contact with the
flood waters.
Applies to Naturally Occurring Radionuclides and Man-made Radionuclides
With Ubiquitous Background Concentrations in the Environment
(I) Measured concentrations (in- units of activity, for example pCi per kilogram [pCi/kg], pCi per liter [pCi/L], pCi per
cubic meter [pCi/m3]) of a given radionuclide in the sample are at a level that:
(a) Equals or exceeds a value 2 standard deviations above the mean site-specific background concentration for
that radionuclide in that type of sample, or
(b) Exceeds the upper-limit value of the range of regional background concentration values for that specific
radionuclide in that type of sample.
(ii) Some portion of the increase must be attributed to the site to establish the observed release (or observed
contamination).
(iii) For the soil exposure pathway only, the radionuclide must also be present at the surface or covered by 2 feet or
less of cover material (for example, soil) to establish observed contamination. **
Applies to Man-made Radionuclides
Without Ubiquitous Background Concentrations in the Environment:
I
(I) Measured concentrations (in units of activity) of a given radionuclide in the sample equals or exceeds the sample
quantitation limit for that specific radionuclide in that type of media and is attributable to the site.
(a) However, if the radionuclide concentration equals or exceeds its sample quantitation limit, but its release can
also be attributed to one or more neighboring sites, then the measured concentration of that radionuclide must
also equal or exceed a value either 2 standard deviations above the mean concentration of that radionuclide
contributed by the neighboring sites or 3 times its background concentration, whichever is lower.
(ii) If the sample quantitation limit cannot be established:
(a) use the EPA contract-required quantitation limit (CRQL) in place of the sample quantitation limit in
establishing an observed release (or observed contamination) if the sample analysis was performed under the
EPA Contract Laboratory Program, or
(b) use the detection limit in place of the sample quantitation limit if the sample analysis is not performed under
the EPA Contract Laboratory Program.
(iii) For the soil exposure pathway only, the radionuclide must also be present at the surface or covered by 2 feet or
less of cover material (for example, soil) to establish observed contamination.**
Applies to Gamma-Emitting Radiongclides
(I) The gamma radiation exposure rate in microroentgens per hour (uR/hr) using a survey instrument held 1 meter
away from the ground surface (or 1 meter away from an aboveground source), equals or exceeds 2 times the site-
specific background gamma radiation exposure rate.
(ii) Some portion of the increase must be attributable to the site to establish observed contamination.
(iii) The gamma-emitting radionuclides do not have to be within 2 feet of the surface of the source.
Source: Hazard Ranking System; Final Rule, Environmental Protection Agency, 55 FR 51532, December 14, 1990.
* Note: This criterion should not be interpreted to mean that radionuclides present in soils at depths greater than 2 feet below the surface would not
warrant investigation and potential response action, but only that such materials may not be readily detected by surface measurements.
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Q4. How should the area! extent and depth of radioactivity
contamination be determined?
A. As noted in Ql, a conceptual site model should be devel-
oped 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).
The choice of a specific method or methods to characterize
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. For
gamma-emitting radionuclides in near-surface sources,
walk-over radiation surveys are typically conducted to
characterize the areal extent of contamination. For subsur-
face contamination, borehole logging for gamma emitters,
core sampling programs for radionuclides that emit only
alpha or beta particles, or a combination of both types of
methods, may be advisable. In addition to measurements
to determine volumetric contamination in environmental
media, measurementsof surface contamination on building
and equipment surfaces may also be required. Additional
discussion of measurement techniquesand their limitations
is provided in MARSSIM (U.S. EPA et al. 1997) For site-
specific assessments, readers should consult the appropri-
ate EPA Regional Radiation Program Office or Regional
Superfund Office.
Q5. What Held radiation survey instruments should be used
and what are their lower limits of detection?
A. Selection of appropriate radiation detection instrumentsfor
site characterization depends on the decay characteristics
of the radionuclides potentially present at the site, sus-
pected 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 MARSSIM
(U.S. EPA 402-R-96-018) and Chapter 10 of RAGs Part A
(U.S. EPA, 1989a). For supplemental information regard-
ing the usability of analytical data for performing a
baseline risk assessment at sites contaminated with radio-
activity, readers should refer to "Guidance for Data
Usability in Risk Assessment, Part B" (U.S. EPA, 1992d).
For site-specific applications of field radiation survey
instruments, readers should contact their appropriate
Regional Radiation Program Office or Regional Superfund
Office.
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 10'°
Bq). Since most radiation standards in the U.S. are
expressed in conventional units, this system is used for the
purpose of 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 pCi/g for soil (dry-weight), pCi/L for
groundwater or surface water, and pCi/m3 for air.
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 one liter of air that will result in the ultimate
emission of 1.3 x 10s million electron volts (MeV) of alpha
energy. The Working Level Month (WLM) is the exposure
to 1 WL for 170 hours (1 working month).
In addition to radionuclide concentrations in environmental
media, the radiation "exposure" rate is often reported.
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 kg of air). Exposure rates at
contaminated sites are typically expressed in units of
microroentgens/hour (u.R/hr).
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 dpm (disintegration per minute) per 100 cm2 or
pCi per 100cm2.
Q7. What sample measurement units for remedial action
evaluation may be used?
For remedial action evaluations it is often useful to express
radionuclide concentrations in terms of mass (mass
concentration). The carcinogenic effects of a radionuclide
are due to its disintegration rate that occurs during its decay
process, concentrations of radionuclides are generally
measured in terms of activity for health evaluation
purposes. Mass units, however, provide insight and
information into treatment selection, treatment
compatibility, and treatment efficiency, particularly for
remedial actions involving mixed waste. The practice of
using activity concentration should continue for response
actions at CERCLA sites. Mass concentration estimates
contained in proposed and final site decision documents
[e.g., proposed plans, Record of Decisions (RODs))] may
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include, in addition to activity measurements, estimates of
concentrations in terms of mass consistent with those used
for non-radiological contaminants. Typically units for
expressing mass in environmental media for soil and water
are mg/kg for soil and mg/1 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/1. To
estimate the radionuclide concentrations in ppm, the
following equations are given below:
mg/kgson = (2.8xlO-|2)x/lx TlKxpCi/g
mg/lva,,, = (2.8 x 10'15) x A x Tl/2 x pCi/l
ppmsoil = (2.8 xlO'12) x A x TV2xpCi/g
ppmmler = (2.&\lQ-*5)xA\ 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.
I
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. However, EPA has published guidance for
radionuclide methods in Chapter 10 of RAGS Part A (U.S.
EPA, 1989a). In addition, EPA's Radiochemistry
Procedures Manual (U.S. EPA, 1984) provides
information for radionuclide-specific analytical
techniques. For additional guidance on selection of
radiological laboratories and analytical methods, readers
should contact the appropriate RegionalRadiationProgram
Office or Regional Superfund Office, NAREL, or RIENL.
Q9. How can I decide if the data collected are complete and
of good quality?
A. EPA's Guidance for Data Quality Assessment (U.S. EPA,
1995), Guidance for Data Useability in Risk Assessment,
Part /((U.S. EPA, \992c) and Part B (U.S. EPA, 1992d),
provide procedures and statistical tests that may be used to
determine whether or not collected data are of the correct
type, quality, and quantity to support their intended use. In
addition, the MARSSIM (U.S. EPA et al. 1997) addresses
quality assurance and quality control requirements for
radiological data.
II. EXPOSURE ASSESSMENT
Q10. How does the exposure assessment for radionuclides
differ from that for chemicals?
A. Exposure assessment for radionuclides is very similarto that
for chemicals. Both nonradioactive chemical assessments
and radionuclide assessments follow the same basic
steps—i.e., characterizing the exposure setting, identifying
exposure pathways and potential receptors, estimating
exposure point concentrations, and estimating
exposures/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. On
the other hand, with the primary exception of tritium (H-3)
as tritiated water or water vapor, dermal absorption is
typically not a significant exposure pathway for radio-
nuclides and generally need not be considered. (Other
possible exceptions could include organic compounds
containing radionuclides.) Figure 1 depicts typical exposure
pathways for radionuclides; additional pathways that may
be considered on a site-specific basis, where appropriate,
are discussed in Ql 1. Additional discussion of radiation
exposure pathways is provided in the Radiation Exposure
and Risk Assessment Manual (RERAM), June 1996 (EPA
402-R-96-016).
Qll. Can exposure pathways be added or deleted based on
site-specific conditions?
A. Yes. Inclusion or deletion of exposure pathways should be
based upon site-specific conditions, including 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, if justification is provided. In other
cases, exposure pathways that are typically not significant
may be important for the 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.
Q12 . How should radioactive decay products be addressed?
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
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all decay products over time, to determine the time of
maximum potential impact.
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 Q15) incorporate the
ingrowth and decay of radioactive decay products as a
function of time; these models are very useful in
pinpointing the time of maximum dose or risk. Similarly,
slope factors (see Q20) and dose conversion factors (see
Q21) for some radionuclides may include consideration of
radioactive decay products, where appropriate, to facilitate
these considerations in estimating potential radiation dose
and risk. However, such values typically assume that all
decay products are present at the same concentration as the
primaryradionuclide(i.e., secular equilibrium), whichmay
not be appropriate for all situations. Readers should
consult their Regional Radiation Program Office or
Regional Superfund Office for additional information
regarding such limitations. See also section "Modeling
Assessment of Future Exposures" in OSWER Directive
9200.4-18 (U.S. EPA 1997a) for information modeling
decay products.
Q13. To what extent should generic and site-specific factors
and parameter values be used in exposure assessments?
A. For both radionuclide and chemical assessments, EPA
recommends the use of empirically-derived, site-specific
factors and parameter values, where such values can be
justified and documented. For generic assessments, EPA
recommends the use of the default parameter values
provided in OSWER Directive 9285.6-03 Standard
Default Exposure Factors (U.S. EPA, 1991c) and the
Exposure Factors Handbook (U.S. EPA, 1990, 1997b).
Q14. How should exposure point concentrations be
determined?
A. As for chemical contaminants, exposure point
concentrations of radionuclides in environmental media
and radiation exposure rates (e.g., alpha, beta, gamma)
should be either measured, modeled, or both. To the
extent possible, measurement data should be used to
evaluate current exposures. When measurements at the
exposure locations cannot be made, or when predicting
potential concentrations and exposures at future times,
modeling is required (see Q15).
Q15. What calculation methods or multimedia radionuclide
transport and exposure models are recommended by
EPA for Superfund risk assessments?
A. Currently, only the equations in RAGS Part B (U.S. EPA,
1991 a) - which are used to develop risk-based preliminary
remediation goals for hazardous chemicals and radio-
nuclides - are recommended by EPA for Superfund
radiation risk assessments. (Note: The Soil Screening
Guidance for Radionuclides (U.S. EPA 1998d) is expected
to supersede the RAGS Part B algorithms when finalized.)
Numerous computerized mathematical models have been
developed by EPA and other organizations to predict the
fate and transport of radionuclides in the environment; these
include single-media models (e.g., ground water transport)
as well as multi-media models. These models have been
designed for a variety of goals, objectives and applications,
but no single model may be appropriate for all site-specific
conditions. While the Agency has approved individual
models for specific applications (e.g., CAP88 or COMPLY
for atmospheric transport calculations to demonstrate
compliance with 40 CFR Part 61 requirements), no model
has yet been formally endorsed for evaluating potential
impacts from radionuclides in soil. For further information
on selection of models appropriate to meet a 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 types of models as well.
Attachment 1 provides a bibliography of reference
documents for numerous models currently available.
Readers are strongly encouraged to consult with the
appropriate EPA Regional Radiation Program Office or
Regional Superfund Office in which the site is located for
guidance on selection and use of radionuclide fate and
transport models for site-specific applications.
Q16. 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). For Rn-222 (also called radon), the
parent radium isotope is Ra-226 and for Rn-220 (also called
thoron), the parent radium isotope 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.
Consequently, most (but not all) radon exposure and risk
assessments deal with radon (Rn-222) arising from radium
(Ra-226) contamination.
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Structures built on radium-contaminated soil or
constructed with radium-bearing materials can accumulate
elevated concentrations of radon in indoor air. Some
radiation protection standards which may be potential
ARARs at a site, explicitly exclude dose or risk from radon
and its decay products from consideration. Other potential
ARARs and to-be-considered (TBC) information directly
address radon and its decay products (e.g., allowable
concentrations of radon decay products in indoor air under
40 CFR 192(b)(l) of a standard of 0.003 working level
(WL) and a goal of 0.002 WL, as well as the U.S. EPA
Guideline of 4 pCi radon-222 per liter of indoor air).
Several EPA-approved methods are available for
measuring radon and progeny concentrations in indoor air
(EPA et al, 1997). 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.
Readers are encouraged to consult with the EPA Regional
Radiation Program Office or Regional Superfund Office
for specific guidance and recommendations concerning
measurement of radon concentrations in indoor air,
evaluation of potential exposures, and applicable
mitigation measures. Also, some states have their own.
radon testing and mitigation requirement or
recommendations. Readers should also determine if any of
the standards for radon are potential ARARs at their site
(see Q 34).
Q17. How long a time period should be considered for
possible future exposures?
A. Section "Modeling Assessment of Future Exposures" in
OSWER Directive 9200.4-18 (U.S. EPA 1997a) provides
guidance for estimating future threats. Also, in some cases,
Federal or State ARARs may include specific time-frame
requirements for a given purpose, such as disposal of
radioactive materials in an approved waste repository.
Q18 . How should the results of the exposure assessment for
radionuclides be presented?
A. Results of the exposure assessment for radionuclides should
be presented in two stages: (1) intake and external exposure
estimates for use in risk characterization; and (2) estimates
of radiation dose (see Q22 for discussion of specific
dosimetric quantities that may be appropriate) for
comparison with dose-based standards. Note that intake
estimates for radionuclides should not be divided by body
weight or averaging time as is done for chemical
contaminants. Intake estimates for inhalation or ingestion
pathways should include the total activity of each
\ V\ ° 7; 7
R&dioaetive Contaminants in Soil
Figure 1. Typical Radionuclide Exposure Pathways
8
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radionuclide inhaled or ingested via each pertinent route of
exposure (e.g., ingestion of contaminated drinking water,
direct ingestion of contaminated soil, ingestion of
contaminated produce/milk/meat). Measured or predicted
external exposure rates should be presented, along with the
exposure time, frequency, and duration. In the absence of
measured exposure rates, the concentration of each
radionuclide in soil is needed to estimate the risk from the
external pathway using slope factors. When present,
estimates of radiation surface contamination also should be
presented by radiation type (alpha, beta, gamma).
III. TOXICITY ASSESSMENT
Q19. 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 electric field of their nucleus (ionization). In
living tissue, this energy transfer can produce chemically
reactive ions or free radicals, destroy cellular constituents,
and damage DNA. Irreparable 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 Q24).]
The type of ionizing radiation emitted by a particular
radionuclide depends upon 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. For purposes of radiation risk estimates,
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).
Ionizing radiation can cause deleterious effects on biologi-
cal 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).
Q20 . 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. 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).
Current radionuclide slope factors incorporate the age- and
gender-specific radiogenic cancer risk models from
Estimating Radiogenic Cancer Risks (U.S. EPA, 1994b).
Age-specific estimates of absorbed dose rate are used,
where available, for internal exposure pathways, whereas
dose estimates for external exposure are taken directly from
Federal Guidance Report No. 12 (U.S. EPA 1993b).
Population mortality statistics and baseline cancer rates
reflect the U.S. population of 1989-1991 (1979-1981 for
slope factors derived prior to 1998). Detailed information
on the derivation and application of risk coefficients and
radionuclide slope factors is presented in Radiation
Exposure and Risk Assessment Manual (RERAM) (U.S.
EPA, 1996,1998h).Agency-recommendedslope factors for
radionuclides (as well as nonradioactive carcinogens) are
published in EPA's Health Effects Assessment Summary
Tables (HEAST) (U.S. EPA, 1998e). EPA plans to revise
the HEAST tables based on information in Federal
Guidance Report No. 13: Health Risks from Low-Level
Environmental Exposure to Radionuclides (U.S. EPA
1998g).
Q21 . 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 a radio-
nuclide concentration in soil, air, water, or foodstuffs to a
radiation dose. 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 Q21). 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-approved DCFs for inhalation and ingestion exposure
are published in Federal Guidance Report No. 11 (U.S.
EPA, 1988b). EPA-approved DCFs for external exposure
are published in Federal Guidance Report No. 12 (U.S.
EPA, 1993b). Both compilations provide DCF values for a
reference adult only, but it is anticipated that future
revisions will include values for other age groups.
Q22 . What is dose equivalent, effective dose equivalent, and
related quantities?
As discussed in Q18, 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"
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has been defined as a measure of the energy absorbed by
living tissues, adjusted for the relative biological
effectiveness of 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). For computation of dose
equivalent, the absorbed dose is multiplied by Quality
Factor (Q) or radiation weighting factor (WR); these values
range from 1 for photons and electrons to 10 for neutrons
to 20 for alpha particles (i.e., 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 (i.e., 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 (based on occupational exposure) following the
intake. By contrast, external radiation exposure contribute
to dose only as long as the receptor is present within the
external radiation field.
When 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"
was developed by the International Commission on
Radiological Protection (ICRP) to account for these
differences and to normalize radiation 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.
Q23. What is the critical organ approach to dose limitation?
A. Critical organ standards developed by EPA and NRC
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. 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 system allows for one
value of dose equivalent 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 (75 mrem/yr) dose
limits, these critical organ standards are not comparable to
25 mrem/yr effective dose equivalent standards or guidance.
EPA's determination that the 25 mrem/yr dose level found
in NRC's decommissioning standard and various guidance
should not be used to establish cleanup levels at CERCLA
sites does not apply to critical organ standards.
Q24. 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 for comparison with EPA's target risk range (i.e.,
10"4 to 10"6 lifetime excess cancer risk). The incremental
risk is calculated by multiplying estimates of the lifetime
intake via inhalation and ingestion of each radionuclide of
concern, and the duration and concentration in
environmental media to which the receptor is exposed via
the external exposure pathway, by the appropriate slope
factor values for that exposure pathway and radionuclide.
Additional information on the use of radionuclide slope
factors and their underlying assumptions, which introduce
significant uncertainties, is provided in the Radiation
Exposure and Risk Assessment Manual (RERAM) (U.S.
EPA 1996a, 1999b).
Estimates of cancer risk from radionuclide exposures may
also be computed by multiplying the effective dose
equivalent computed using the DCFs by a risk-per-dose
factor. EPA recommends that this method not be used at
CERCLA sites to estimate risks for PRGs or cleanup levels,
and estimates computed using this method may tend to
inaccurately estimate potential risks, with the magnitude of
discrepancy dependent on the dominant radionuclides and
exposure pathways for the site-specific conditions. These
differences can be attributed to factors such as the
consideration of competing mortality risks and age-
dependent radiation risk models in the development of the
slope factors, different distributions of relative weights
assigned to individual organ risks in the two methods, and
differences in dosimetric and toxicological assumptions.
Some key differences in the two methods are summarized
in Table 2.
Due to these factors, no simple and direct conversion
between radiation dose and radiogenic cancer risk is
available. Given the differing dosimetric and radio-
toxicological characteristics of different radionuclides, as
reflected in the DCFs and slope factors, respectively, a
given dose from one radionuclide via a given exposure
pathway may present a much greater cancer risk than the
same dose from another radionuclide and/or exposure
pathway. Therefore, any conversion between dose and risk
now must be performed on a radionuclide- and pathway-
specific basis.
10
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The primary use of DCFs should generally be to compute
doses resulting from site-related exposures for comparison
with radiation protection standards and dose limits (see
Q31 -32) that are determined to be ARARs or TBCs. This
is accomplished by multiplying the exposure estimates
produced through the exposure assessment (i.e., the intake
of each radionuclide of concern via inhalation and
ingestion, and the duration of exposure and concentration
of each radionuclide of concern in environmental media
for external exposure) by the appropriate DCF values for
that exposure pathway and radionuclide. Unlike excess
cancerrisk, which represents cumulative lifetimeexposure,
dose estimates are typically expressed in terms of annual
exposure (e.g., the effective dose equivalent resulting from
exposure during a one-year period, mrem/year).
Unless otherwise stated in the standard, DCFs from
Federal Guidance Report No. 11 (U.S. EPA, 1988b) and
Federal Guidance Report No. 12 (U.S. EPA, 1993b)
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.
Q25. 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
(i.e., induction of cancer), mutagenicity (i.e., induction of
mutations in somatic or reproductive cells, including
genetic effects), and teratogeniciry (i.e., 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 sites, and evaluation of
teratogenic and genetic effects is not required. Similarly,
consideration of acute effects normally is not required,
since these effects occur only at doses much higher than
normally associated with environmental exposures.
Q26. Should chemical toxicity of radionuclides be
considered?
A. At Superfund radiation sites, EPA generally evaluates
potential human health risks based on the radiotoxicity
(i.e., 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, and is the only radionuclide for which the chemical
toxicity has been identified to be comparable to or greater
than the radiotoxicity, and for which a reference dose
(RfD) has been established to evaluate chemical toxicity.
For radioisotopes of uranium, both effects (radiogenic
cancer risk and chemical toxicity) should be considered.
IV. RISK CHARACTERIZATION
Q27. How should radionuclide risks be estimated?
A. Risks from radionuclide exposures should be estimated in
a manner analogous to that used for chemical contaminants.
That is the estimates of intakes 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 Q25). 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.
Q28 . Should radionuclide and chemical risks be combined?
A. Yes. 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 can not be
exposed to both chemical and radiological carcinogens.
Similarly, the chemical toxicity from uranium should be
combined 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 excess cancer risks are additive
for purposes of evaluating the total incremental cancer risk
associated with a contaminated site.
Q29 How should risk characterization results for radio-
nuclides be presented?
A. Results should be presented according to the standardized
reporting format presented in RAGS Part D (U.S. EPA,
1998a). However, specific guidance for radionuclides (i.e.,
the Radionuclides Worksheet) is not yet available.
EPA guidance for risk characterization (U.S. EPA, 1992e)
indicates that four descriptors of risk are generally needed
for a full characterization of risk: (1) central tendency (e.g.,
median, mean) estimate of individual risk; (2) high-end
estimate (e.g., 95th percentile) of individual risk; (3) risk to
important subgroups (e.g., children) of the population, such
as highly exposed or highly susceptible groups or
individuals, if known; and (4) population risk. The
reasonable maximum exposure (RME) estimate of individ-
11
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ual risk typically presented in Superrund risk assessments
represents a measure of the high-end individual exposure
and risk. While the RME estimate remains the primary
scenario for risk management decisions, additional risk
descriptors may be included to describe site risks more
fully.
Q30 . Should the collective risk to populations be estimated
along with that to individual receptors?
A. Risk to potential individual receptors is the primary
measure of protectiveness under the CERCLA process
(i.e., the target range of 10~6 to 10"4 lifetime excess cancer
risk to the RME receptor). As noted in Q28, however,
Agency guidance (U.S. EPA, 1992e) also indicates that the
collective risk to the potentially exposed population and to
important subgroups of the population also should be
evaluated where possible. Consideration of population
risk provides additional input to risk management
decisions; such considerations may be either qualitative or
quantitative depending on the availability of data and the
magnitude of projected population risk.
Q31. 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
is essential for informed risk management decisions. RAGS
and subsequent guidance (U.S. EPA, 1992e, 1995b) stress
the importance of a thorough presentation of the
uncertainties, limitations, and assumptions that underlay
estimates of risk. Either qualitative or quantitative evalu-
ation may be appropriate, depending on the availability of
data and the magnitude of predicted risk. In either case, the
evaluation should address both uncertainty (i.e., "the lack of
knowledge about specific factors, parameters, or models")
and variability (i.e., "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 (e.g., RME or 95th percentile).
Table 2. Comparison of Radiation Risk Estimation Methodologies: Slope Factors vs Effective Dose Equivalent
Parameter
Competing
Risks
Risk
Models
Genetic
Risk
Dose
Estimates
RBE for high-
LET (alpha)
radiation
Organs
Considered
Lung Dose
Definition
Integration
Period
Dosimetric /
Metabolic
Models
Slope Factor Approach
• Persons dying from competing causes of death (e.g., 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 1989-1991 (previously 1979-1981) U.S. population.
• Age-dependent and gender-dependent risk models for 14 cancer
sites are considered individually and integrated into the slope factor
estimate.
• Genetic risk is not considered in the slope factor estimates; however,
ovary is considered as a potential cancer site.
• Low-LET and high-LET dose estimates considered separately for
each target organ.
• 20 for most sites (8 prior to 1994)
• 10 for breast (8 prior to 1994)
• 1 for leukemia (1.117 prior to 1994)
• Estimates of absorbed dose to 16 target organs/tissues considered
for 13 specific cancer sites plus residual cancers.
• Absorbed dose used to estimate lung cancer risk computed as
weighted sum of dose to tracheobronchial region (80%) and
pulmonary lung (20%).
• Variable length (depending on organ-specific risk models and
consideration of competing risks) not to exceed 1 1 0 years.
• 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).
Effective Dose Equivalent x Risk Factor Approach
• Competing risks not considered.
• Risk estimate averaged over all ages, sexes, and cancer
sites.
• Effective dose equivalent (EDE) value includes genetic risk
component.
• Dose-equivalent includes both low-LET and high-LET
radiation, multiplied by appropriate Quality Factors.
• 20 (all sites)
• EDE (ICRP, 1979) considers dose estimates to 6 specific
target organs plus remainder (weighted average of 5 other
organs).
• Average dose to total lung (mass weighted sum of doses to
the tracheobronchial region, pulmonary region, and
plumonary lymph nodes).
• Fixed integration period of 50 years typically considered.
• Typically employ ICRP Publication 30 (ICRP, 1 979) models
and parameter for radionuclide uptake, distribution, and
retention.
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\ For both chemical carcinogens and radionuclides,
extrapolation from high dose and dose rate exposure is
generally required to estimate risks of low-level exposures.
This extrapolation typically constitutes the greatest source
of uncertainty. For chemical carcinogens, additional
uncertainty may be introduced due to extrapolation of
animal data to humans. 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. Other
sources of uncertainty may include that 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 (e.g., intake rates, 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 always be presented as a supplement to - not
instead of- the deterministic (i.e., point estimate) methods
outlined in RAGS Part A. A tiered approach is often
useful, with the rigor of the analysis dependent on the
magnitude of predicted risk. Factors to be considered in
conducting a probabilistic analysistypically 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).
Q32 . When should a dose assessment be performed?
OSWER Directive 9200.4-18 (U.S. EPA 1997a) specifies
that cleanup levels for radioactive contamination at
CERCLA 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. 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"* used for PRGs) and expressed
in terms of risk (# x 10"*). 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 if
based on site-specific circumstances. For further
discussion of how EPA uses the risk range, see OSWER
Directive9355.0-30, Role of the Baseline Risk Assessment
in Superfund Remedy Selection Decisions (U.S. EPA
199Id). In general, dose assessment used as a method to
assess risk is not recommended at CERCLA sites.
Please note that the references to 15 mrem/yr in OSWER
Directive 9200.4-18 are intended as guidance for the
evaluation of potential ARARs and TBCs, and should not
be used as a TBC for establishing 15 mrem/yr cleanup
levels at CERCLA sites. At CERCLA sites dose
assessments should generally not be performed to assess
risks or to establish cleanup levels except to show
compliance with an ARAR that requires a dose assessment
(e.g., 40 CFR 61 Subparts H and I, and 10 CFR 61.41).
Q33 How and when should exposure rate be used to estimate
radionuclide risks?
As discussed previously (see Q24 and Q27), EPA
recommends that estimates of radiation risk should be
derived using slope factors, in a manner analogous to
that used for chemical contaminants. However, there
may be circumstances where it is desirable to also consider
estimates of risk based on direct exposure rate
measurements of penetrating radiation. Instances where it
may be beneficial 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 may not
decrease the need for a final status survey.
• When risk estimates developed during a risk assessment
may underestimate the level of risk posed by
radionuclides. An example of this situation would be
where the source of the radiation is highly irregular
(inside a contaminated structure) instead of being an
infinite plane, which is the standard assumption used
during risk assessments.
When developing risk estimates under any of these
situations, risk factors from "Estimating Radiogenic Cancer
Risks, EPA 402-R-93-076" or HEAST plus shape & area
factor, should be used in conjunction with the measured
dose rate to develop a risk estimate for external exposure to
penetrating radiation.
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, such data may only reflect a subset of
the radionuclides and exposure pathways of potential
concern (e.g., only external exposure from gamma-emitting
radionuclides in near-surface soil), and may present an
incomplete picture of site risks (e.g., 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
13
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site characterization data, including concentrations of all
radionuclides of concern in all pertinent environmental
media. The principal benefits of exposure rate
measurements is the speed and convenience of analysis,
and the elimination of potential modeling uncertainties.
However, these data should be used in conjunction with,
rather than instead of, characterization data of
radionuclides concentrations in environmental media to
obtain a complete picture of potential site-related risks.
Q34. What radiation standards may be applicable or
relevant and appropriate requirements (ARARs)?
A. In some cases, cleanup levels may be derived based on
compliance with ARARs. Attachment A "Likely Federal
Radiation Applicable or Relevant and Appropriate
Requirements (ARARs)" of OSWER Directive 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. It should be noted that the Agency has
determined that the NRC decommissioning require-
ments (e.g., 25,100 mrem/yr dose limits) under 10 CFR
20 Subpart E should generally not be used to establish
cleanup levels under CERCLA, even when these
regulations are ARARs. 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 subsur-
face soils.
V. ECOLOGICAL ASSESSMENTS
Q35 . What guidance is available for conducting ecological
risk assessments.
A. OSWER Directive 9285.7-25, Ecological Risk Assessment
Guidance for Superfund: Process for Designing and
Conducting Ecological Risk Assessments (U.S. EPA June
1997) 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
judgement is required to apply the process outlined in this
guidance to ecological risk assessments at specific sites.
VI. BACKGROUND CONTAMINATION
Q36. How should background levels of radiation be
addressed?
A. Background radiation levels on a specific site will
generally be determined as background levels are
determined for other contaminants, on a radionuclide-
specific basis when the same constituents are found in on-
site samples as well as in background samples. The levels
of each constituent in background are compared to that on
site-related contaminant to determine its impact, if any.
Background is generally measured only for those
radionuclides that are contaminants of concern and is
compared on a radionuclide specific basis to determine
cleanup levels. For example, background levels for radium-
226 and radon-222 would generally not be evaluated at a
site if those radionuclides were not site-related
contaminants.
In certain situations background levels of a site-related
contaminant may equal or exceed PRGs established for a
site. In these situations background and site-related levels
of radiation will be addressed as they are for other
contaminants at CERCLA sites. For further information
regarding background, see section "Background
Contamination" in OSWER Directive 9200.4-18 (U.S. EPA
1997a).
WHERE TO GO FOR FURTHER INFORMATION
Attachment 1 provides a bibliography of selected EPA documents
related to radiation risk assessment. Readers should periodically
consult the EPA Headquarters and Regional Superfund and
Radiation Program Offices for updates on current guidances and
for copies of new documents. Copies of many of the documents
listed in Attachment 1 are available to the public for a fee from the
National Technical Information Service (NTIS) at (703) 605-6000
or (800) 553-6847. Many documents are also available from EPA
on the Internet.
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. Such 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 specialists for this fact sheet are Dr. Kung-Wei
Yeh of ORIA and Stuart Walker of OERR. General questions
about this fact sheet should be directed to 1-800-424-9346.
REFERENCES
International Atomic Energy Agency (IAEA). 1992. Effects of
Ionizing Radiation on Plants and Animals at Levels Implied by
Current Radiation Protection Standards. IAEA Technical
Report Series No. 332.
International Commission on Radiological Protection (ICRP).
1977. Recommendations of the ICRP. ICRP Publication 26.
Pergamon Press, Oxford, UK.
14
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International Commission on Radiological Protection (ICRP).
1979. Limits for Intakes ofRadionuclides 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. 7990 Recommendations of the International
Commission on Radiological Protection. ICRP Publication
60. Pergamon Press, Oxford, UK.
International Commission on Radiological Protection (ICRP).
1993. Age-Dependent Doses to Members of the Public from
Intake of Radionuclides, Part 2. ICRP Publication 67.
Pergamon Press, Oxford, UK.
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 Press, Oxford, UK.
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.
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 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 and Monitoring Methods for
Radiation Protection. NCRP Report No. 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.
United Nations Scientific Committee on the Effects of Atomic
Radiation (UNSCEAR). 1988. Sources, Effects and Risks of
Ionizing Radiation. United Nations, NY.
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.
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.
U.S. EPA. 1989a. Risk Assessment Guidance for Superfund,
Volume I: 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.
U.S. EPA. 1989b. Methods for Evaluating the Attainment of Soil
Cleanup Standards. Volume I: Soils and Solids. EPA/540/1 -
89/003. Statistical Policy Branch, Office of Policy, Planning,
and Evaluation, Washington, DC.
U.S. EPA. 1989c. Risk Assessment Methodology: Environmental
Impact Statement—NESHAPsfor Radionuclides, Background
Information Document—Volume I. EPA-520/1-89-006-1.
Office of Radiation Programs, Washington, DC.
U.S. EPA. 1990. Exposure Factors Handbook. EPA/600/8-
89/043. Office of Health and Environmental Assessment,
Washington, DC.
U.S. EPA. 199la. Risk Assessment Guidance for Superfund,
Volume I: Human Health Evaluation Manual (Part B,
Development of Risk-Based Preliminary Remediation Goals).
Publication 9285.7-0 IB. Office of Emergency and Remedial
Response, Washington, DC. NTIS PB92-963333.
U.S. EPA. 1991b. Risk Assessment Guidance for Superfund,
Volume I: 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.
U.S. EPA. 1991c. Human Health Evaluation Manual,
15
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Supplemental Guidance: StandardDefaultExposureFactors.
OSWER 9285.6-03. Office of Emergency and Remedial
Response, Washington, DC. NTIS PB91-921314.
U.S. EPA. 199Id. Role of the Baseline Risk Assessment in
Superfund Remedy Selection Decisions. OSWER Directive
9355.0-30. Office of Solid Waste and Emergency Response.
U.S. EPA. 1992a. Statistical Methods for Evaluating the
Attainment of Cleanup Standards—Volume2: Ground Water.
Draft. Statistical Policy Branch, Office of Policy, Planning,
and Evaluation, Washington, DC.
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.
U.S. EPA. 1992c. Guidance for Data Useability in Risk
Assessment (Part A). Publication 9285.7A. Office of
Emergency and Remedial Response, Washington, DC.
U.S. EPA. 1992d. Guidance for Data Useability in Risk
Assessment (Part B). Publication 9285.7B. Office of
Emergency and Remedial Response, Washington, DC.
U.S. EPA. 1992e. Guidance on Risk Characterization for Risk
Managers and Risk Assessors. Memorandum from F.H.
Habicht, Deputy Administrator, Washington, DC, 2/26/92.
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.
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.
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.
U.S. EPA. 1994a. Guidance for the Data Quality Objectives
Process. EPA QA/G4. Office of Research and
Development.
U.S. EPA. 1994b. Estimating Radiogenic Cancer Risks. EPA
402-R-93-076. Office of Radiation and Indoor Air,
Washington, DC.
U.S. EPA. 1995a. Guidance for Data Quality Assessment.
External Working Draft. EPA QA/G9. Quality Assurance
Management Staff, Office of Research and Development,
Washington, DC.
U.S. EPA. 1995b. EPA Risk Characterization Program.
Memorandum from Carol Browner, Office of the
Administrator, Washington, DC, 3/21/95.
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 Levels for CERCLA
Sites with Radioactive Contamination, OSWER No. 9200.4-
18, August 1997.
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.
U.S. EPA. 1997d. Guiding Principles for Monte Carlo Analysis,
EPA/630/R-97-001.
U.S. EPA. 1998a. Risk Assessment Guidance for Superfund,
Volume I: Human Health Evaluation Manual, Part D,
Standardized Planning, Reporting, and Review of Superfund
NTIS PB97-963305. Office of Emergency and Remedial
Response, Washington, DC.
U.S. EPA. 1998b. Risk Assessment Guidance for Superfund,
Volume I: 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.
U.S. EPA. 1998c. Use of Soil Cleanup Criteria in 40 CFR Part
192 as Remediation Goals for CERCLA Sites, OSWER
Directive No. 9200.4-25, February 1998.
U.S. EPA. 1998d, Soil Screening Guidance for Radionuclides:
User's Guide (Draft). Office of Emergency and Remedial
Response, Washington, DC. August 1998.
U.S. EPA. 1998e. Integrated Risk Information System (IRIS).
Cincinnati, OH.
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.
U.S. EPA. 1998g. Health Risks from Low-Level Environmental
Exposure to Radionuclides: Federal Guidance Report No. 13 -
Part I, Interim Version. EPA 402-R-97-014. Office of Air and
Radiation, Washington, DC.
16
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U.S. EPA. 1998H. Radiation Exposure and Risk Assessment
Manual: Risk Assessment Using Radionuclide Slope Factors
Derived Under Federal Guidance Report No. 13. (Draft),
Office of Radiation and Indoor Air, Washington, DC.
U.S. EPA, NRC, U.S. DOE, and U.S. Department of Defense.
1997. Multi-Agency Radiation Survey and Site Investigation
Manual (MARSSIM). NUREG-1575, EPA 402-R-97-016,
Washington, DC.
U.S. EPA, NRC, U.S. DOE, and U.S. Department of Defense.
1998. Multi-Agency Radiation Laboratory Analytical
Protocols(MARLAP). Washington,DC. (Under Development)
17
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ATTACHMENT #1
Bibliography of Selected EPA
Guidance Documents and Directives on Risk Assessment
U.S. ENVIRONMENTAL PROTECTION AGENCY
EPA Human Health Risk Assessment
• Risk Assessment Guidance for Superfund: Volume I:
Human Health Evaluation Manual, Part A, Interim Final.
EPA/540/1-89/002. Office of Emergency and Remedial
Response, Washington, DC, March 1989.
• Role of the Baseline Risk Assessment in Superfund Remedy
Selection Decisions. OSWER Directive 9355.0-30. ^Office
of Solid Waste and Emergency Response, Washington, DC.
April 22, 1991.
• Guidance on Risk Characterization for Risk Managers and
Risk Assessors. Memorandum from Deputy Administrator,
U.S. Environmental Protection Agency H. Habicht to
Assistant and Regional Administrators. Feb. 26, 1992.
EPA Ecological Risk Assessment
• Risk Assessment Guidance for Superfund: Volume II:
Environmental Evaluation Manual, Interim Final.
EPA/540/1-89/001. Office of Emergency and Remedial
Response, Washington, DC. March 1989.
• Ecological Assessment of Hazardous Waste Sites: A Field
and Laboratory Reference. EPA/600/3-89/013. Environ-
mental Research Laboratory, CorvaHis, OR. March 1989.
• Framework for Ecological Risk Assessment. EPA/630/R-
92/001. Risk Assessment Forum, Washington, DC. Febru-
ary 1992.
EPA Exposure Assessment
• Superfund Exposure Assessment Manual. OSWER Direc-
tive 9285.5-1. EPA/540/1-88/001. NTIS PB89-135859.
Office of Emergency and Remedial Response, Washington,
DC. April 1988.
• Guidelines for Exposure Assessment. Federal Register, Vol.
57, No. 104, pp 22888-22938, Office of Health and
Environmental Assessment, Washington, DC. 5/22/92.
EPA Standard Exposure Scenarios and Default Ex-
posure Factors
• Exposure Factors Handbook: Final Report. EPA/600/8-
89/043. Office of Health and Environmental Assessment,
Office of Research and Development, Washington, DC.
March 1989.
• Exposure Factors Handbook (Update). EPA/600/P-95/
002F. Office of Research and Development, Washington,
DC. August 1997.
• Human Health Evaluation Manual, Supplemental Guid-
ance: Standard Default Exposure Factors. OSWER
Directive 9285.6-03. Office of Emergency and Remedial
Response, Washington, DC. March 25, 1991.
• Radiation Site Cleanup Regulations: Technical Support
Document for the Development of Radionuclide Cleanup
Levels for Soil (Review Draft). Office of Air and Radiation,
Washington, DC. September 1994.
• Soil Screening Guidance: User's Guide. EPA/540/R-
96/018, Office of Emergency and Remedial Response,
Washington, DC. June 1996.
• Soil Screening Guidance: Technical Background Docu-
ment. EPA/540/R-96/128, Office of Emergency and
Remedial Response, Washington, DC. June 1996.
EPA-Approved Toxicity Criteria
• IntegratedRiskInformationSystem(lRlS). Cincinnati,OH.
• Health Effects Assessment Summary Tables (HEAST).
Annual Update, FY 1997. Environmental Criteria and
Assessment Office, Office of Health and Environmental
Assessment, Office of Research and. Development,
Cincinnati, OH. 1997.
• Limiting Values of Radionuclide Intake and Air Concentra-
tion and Dose Conversion Factors for Inhalation, Submer-
sion, and Ingestion: Federal Guidance Report No. 11.
EPA-520/1-88-020. Office of Radiation Programs,
Washington, DC. September 1988.
• External Exposure to Radionuclides in A ir, Water, and Soil:
Federal Guidance Report No. 12. EPA 402-R-93-081.
Office of Air and Radiation. September 1993.
• Health Risks from Low-Level Environmental Exposure to
Radionuclides: Federal Guidance Report No. 13 - Part 1
(Interim Version). EPA402-R-97-014. Office of Air and
Radiation. January 1998.
EPA Methods for Deriving Preliminary Remediation
Goals and Soil Screening Levels
• Risk Assessment Guidance for Superfund: Volume I:
Human Health Evaluation Manual, Part B, Development of
Risk-Based Preliminary Remediation Goals, Interim.
EPA/540/R-92/003. Office of Research and Development,
Washington, DC. December 1991.
• Soil Screening Guidance: User's Guide. EPA/540/R-
96/018, Office of Emergency and Remedial Response,
Washington, DC. June 1996.
• Soil Screening Guidance: Technical Background Docu-
ment. EPA/540/R-96/128, Office of Emergency and
Remedial Response, Washington, DC. June 1996.
• Soil Screening Guidance for Radionuclides: User's Guide
(Draft). Office of Radiation and Indoor Air and Office of
Emergency and Remedial Response, Washington, DC.
September 1998.
A1-1
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ATTACHMENT #1 (Continued)
Bibliography of Selected EPA
Guidance Documents and Directives on Risk Assessment
EPA Modeling
• OSWER Models Study: Promoting Appropriate Use of
Models in Hazardous Waste /Superfund'Programs: Phase
I: Final Report. Office of Program Management and
Technology, Office of Solid Waste and Emergency Re-
sponse, Washington, DC. May 26, 1989.
• OSWER Models Management Initiative: Report on the
Usage of Models in Hazardous Waste / Superfund Pro-
grams: Phase II: Final Report. Office of Program Man-
agement and Technology, Office of Solid Waste and
Emergency Response, Washington, DC. December 1990.
• Environmental Pathway Models—Ground- Water Modeling
in Support of Remedial Decision Making at Sites Contami-
nated with Radioactive Material. EPA 402-R-93-009.
Office of Air and Radiation, Washington, DC. March 1993.
• Frameworkfor Assessing Groundwater Modeling Applica-
tions. EPA-500-B-94-004. Resource Management and
Information Staff, Office of Solid Waste and Emergency
Response, Washington, DC. 1994.
• Groundwater Modeling Compendium, Second Edition.
EPA-500-B-94-003. Resource Management and Informa-
tion Staff, Office of Solid Waste and Emergency Response,
Washington, DC. 1994.
• Modifications to the PRESTO-CPG Code to Facilitate the
Analysis of Soil Contamination Sites. RAE-9231/6-1.
Rogers & Associates Engineering Corporation with S.
Cohen & Associates, Inc. Jan. 14, 1994.
EPA Data Quality/Data Control (QA/QC) and Data
Useability
• Soil Sampling Quality Assurance User's Guide. EPA
600/4-84-0043. Office of Emergency and Remedial
Response, Washington, DC. May 1984.
• Guidance for Data Useability in Risk Assessment (Part A):
Final Advance Copy. Publication 9285.7A. Office of
Emergency and Remedial Response, Washington, DC.
April 1992. [Covers data Useability for hazardous chemi-
cals.]
• Guidance for Data Useability in Risk Assessment (Part B):
Final. Publication 9285.7B. PB92-963362. Office of
Emergency and Remedial Response, Washington, DC. May
1992. [Covers data useability for radionuclides.]
• Data Quality Objectives for Superfund: Interim Final
Guidance. EPA 540-R-93-071. Publication 9255.9-01.
NTIS PB92-96338. Office of Emergency and Remedial
Response, Washington, DC. 1993.
• Quality Assurance for Superfund Environmental Data
Collection Activities. Quick Reference Fact Sheet. NTIS
PB93-963273.Office of Emergency and Remedial Re-
sponse, Washington, DC. 1993.
• Guidance for the Data Quality Objectives Process: Final.
EPA QA/G-4. Quality Assurance Management Staff,
Office of Research and Development, Washington, DC.
September 1994.
• Guidance for the Data Quality Assessment. EPA/600/R-
96/084. Quality Assurance Management Staff, Office of
Research and Development, Washington, DC. January
1998.
EPA Statistical Methods for Compliance Demonstra-
tion
• Methods for Evaluating the Attainment of Soil Cleanup
Standards: Volume I: Soil and Soil Media. EPA 230/02-
89-042. Office of Policy, Planning and Evaluation,
Washington, DC. February 1989.
• Statistical Methods for Evaluating the Attainment of
Cleanup Standards: Volume 2 .'Ground Water. Draft Office
of Policy, Planning and Evaluation, Washington, DC.
February 1992.
• Statistical Methods for Evaluating the Attainment of
Cleanup Standards: Volume 3: Reference-Based Standards
For Soils and Solid Media. PB94 176831. Office of Policy,
Planning and Evaluation, Washington, DC. December
1992.
• Guidance for the Data Quality Assessment: External
Working Draft. EPAQA/G-9. Quality Assurance Manage-
ment Staff, Office of Research and Development,
Washington, DC. March 27, 1995.
EPA Survey/Measurement Methods
• Samplers and Sampling Procedures for Hazardous Waste
Streams. EPA 600/2-80-018. Environmental Monitoring
and Support Laboratory, Cincinnati, OH. 1980.
• Handbookfor Sampling and Sample Preservation of Water
and Wastewater. EPA-600/4-82-029. PB83-124503.
Environmental Monitoring and Support Laboratory,
Cincinnati, OH. September 1982.
• Eastern Environmental Radiation Facility: Radiochemistry
Procedures Manual. EPA 520/5-84-006. Eastern Environ-
mental Radiation Facility, Montgomery, AL. August 1984.
• A Compendium of Superfund Field Operations Methods.
EPA/540/P-87/001. OSWER Directive 9355.0-14. Office
of Emergency and Remedial Response, Washington, DC.
December 1987.
• Field Screening Methods Catalog—User's Guide. EPA
540/2-88-005. Office of Emergency and Remedial Re-
sponse, Washington, DC. September 1988.
A1-2
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ATTACHMENT #1 (Continued)
Bibliography of Selected EPA
Guidance Documents and Directives on Risk Assessment
Compendium of ERTGround Water Sampling Procedures.
EPA 540/P-91-005. PB91-921274/CCE. January 1991.
Compendium of ERT Soil Sampling andSurfaceGeophysics
Procedures. EPA 540/P-91-006. PB91-921273/CCE.
January 1991.
Compendium of ERT Ground Water Sampling Procedures.
EPA 540/P-91-007. PB91-921275/CCE. January 1991.
Description and Sampling of Contaminated Soils. EPA
625/12-91-002. Office of Emergency and Remedial Re-
sponse, Washington, DC. November 1991.
User's Guide to the Contract Laboratory Program. PB91 -
921278CDH. Office of Emergency and Remedial Re-
sponse, Washington, DC. 1991.
A1-3
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