United States
Environmental Protectior
Agency
Air And
Radiation
(ANR-459)
EPA 520/1-75-001-A
January 1990
Manual Of Protective Actions
For Nuclear Incidents
Primed on Recycled Paper
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MANUAL OF PROTECTIVE ACTION GUIDES AND PROTECTIVE ACTIONS
FOR NUCLEAR INCIDENTS
Office of Radiation Programs
United States Environmental Protection Agency
Washington, DC 20460
1989
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FOREWORD
Public officials are charged with the responsibility to protect the
health of the public during hazardous situations. The purpose of this
manual is to assist these officials in establishing emergency response
plans and in making decisions during a nuclear incident. It provides
radiological protection guidance that may be used for responding to any
type of nuclear incident or radiological emergency. In addition, it
provides advice on implementation, with particular emphasis on application
to nuclear power facilities.
Under regulations governing radiological emergency planning and
preparedness issued by the Federal Emergency Management Agency
(47 FR 10758, March 11, 1982), the Environmental Protection Agency's
responsibilities include, among others, (1) establishing Protective Action
Guides (PAGs), (2) preparing guidance on implementing PAGs, including
recommendations on protective actions, (3) developing and promulgating
guidance to State and local governments on the preparation of emergency
response plans, and (4) developing, implementing, and presenting training
programs for State and local officials on PAGs and protective actions,
radiation dose assessment, and decision making. This document is intended
to respond to the first two responsibilities.
The manual begins with a general discussion of Protective Action
Guides (PAGs) and their use in planning for protective actions to
safeguard public health. It then presents PAGs for specific exposure
pathways and associated time periods. These PAGs apply to all types of
nuclear incidents. This is followed by guidance for the implementation of
PAGs that emphasizes their application to nuclear power facilities.
Finally, appendices provide definitions, background information on health
risks, and other information supporting the choice of the numerical values
of the PAGs.
PAGs for protection from an airborne plume during the early phase of
an incident at a nuclear power plant were published in the 1980 edition of
this manual. These are reprinted as Chapters 2 and 5 in this edition.
They should continue to be used pending publication of revised PAGs for
the early phase that will apply to a much broader range of situations, and
are currently under development. Recommendations and background
information for protection from ingestion of contaminated food were
published by the Food and Drug Administration in 1982. These are
reprinted here as Chapter 3 and Appendix D and should continue to be
used. Draft recommendations for PAGs for relocation have been developed
recently, and are presented in Chapters 4 and 7. Additional PAGs for
water and radiation protection guidance for recovery will be developed at
a later date.
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This manual Is being re-published to consolidate existing
recommendations with the new draft recommendations for relocation in a
single volume. As the above-noted revised and additional recommendations
are developed, they will be issued as revisions to this manual. The new
PAGs for relocation are appropriate for incorporation into emergency
response plans when they are revised or when new plans are developed.
After experience is gained in the application of these recommedations,
they will be reexamined and refined as necessary, proposed for review, and
then recommended to the President as Federal radiation protection
guidance. It is important to recognize that regulatory requirements for
emergency response are not provided by this manual; they are established
by the cognizant agency (e.g., the Nuclear Regulatory Commission in the
case of commercial nuclear reactors, or the Department of Energy in the
case of their contractor-operated nuclear facilities).
Users of this manual are encouraged to provide comments and
suggestions for improving its contents. Comments should be sent to Joe E.
Logsdon, Guides and Criteria Branch (ANR-460), Criteria and Standards
Division, Office of Radiation Programs, U.S. ^vironmental Protection
Agency, Washington, DC 20460.
Richard J. Guomond, Director
Washington, D. C. Office of Radnation Programs
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CONTENTS
page
Foreword iii
1. Overview 1-1
1.0 Introduction 1-1
1.1 Nuclear Incident Phases and Protective Actions 1-3
1.2 Basis for Selecting Protective Action Guides 1-6
1.3 Planning 1-7
1.4 Implementation of Protective Actions 1-8
References 1-9
2. Protective Action Guides for the Early Phase 2-1
2.0 Introduction 2-1
2.1 Whole Body External Exposure 2-2
2.2 Inhalation Dose 2-4
2.2.1 Exposure to Radioiodines in a Plume 2-4
2.2.2 Exposure to Particulate Material in a Plume 2-6
2.3 Intepretation of PAGs 2-6
3. Protective Action Guides for the Intermediate Phase
(Food and Water) Accidental Radioactive Contamination of
Human Food and Animal Feeds; Recommendations for State and
Local Agencies 3-1
4. Protective Action Guides for the Intermediate Phase
(Deposited Radioactive Materials) 4-1
4.1 Introduction 4-1
4.1.1 Exposure Pathways 4-3
4.1.2 The Population Affected 4-3
4.2 The Protective Action Guides for Deposited Radioactivity . . 4-4
4.2.1 Longer Term Objectives of the Protective Action Guides 4-5
4.2.2 Applying the Protective Action Guides for Relocation . 4-6
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page
4.3 Exposure Limits for Persons Re-entering the Restricted Zone 4-7
References 4-8
5. Implementing the Protective Action Guides for the Early Phase . . 5-1
5.0 Introduction 5-1
5.1 Release Assumptions 5-2
5.1.1 Radioactive Noble Gas and Radioiodine Releases .... 5-4
5.1.2 Radioactive Particulate Material Releases 5-5
5.2 Sequence of Events 5-5
5.2.1 Accident Notification 5-7
5.2.2 Immediate Actions 5-8
5.3 Establishment of Exposure Rate Patterns 5-9
5.4 Dose Projection 5-12
5.4.1 Duration of Exposure 5-14
5.4.2 Whole Body Dose Projection 5-15
5.4.3 Thyroid Dose Projection 5-18
5.4.3.1 Concentrations Based on Release Rates .... 5-21
5.4.3.2 Concentrations Based on Gamma Exposure Rate
Measurements 5-24
5.5 Protective Action Decisions 5-30
References 5-35
6. Implementing the Protective Action Guides for the Intermediate
Phase (Food and Uater) 6-1
7. Implementing the Protective Action Guides for the Intermediate
Phase (Exposure to Deposited Materials) 7-1
7.1 Introduction 7-1
7.1.1 Protective Actions 7-2
7.1.2 Areas Involved 7-2
7.1.3 Sequence of Events 7-5
7.2 Establishment of Isodose-rate Lines 7-8
VI
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page
7.3 Dose Projection 7-9
7.3.1 Projected External Gamma Dose 7-10
7.3.2 Inhalation Dose Projection 7-18
7.4 Priorities 7-21
7.5 Reentry 7-23
7.6 Surface Contamination Control 7-23
7.6.1 Considerations and Constraints 7-24
7.6.2 Numerical Relationships 7-25
7.6.3 Recommended Surface Contamination Limits 7-26
References 7-30
8. Radiation Protection Guidance for the Late Phase (Recovery)
(reserved) 8-1
TABLES
1-1 Exposure Pathways, Incident Phases, and Protective Actions . 1-5
2-1 Protective Action Guides for Whole Body Exposure to Airborne
Radioactive Materials 2-3
2-2 Protective Action Guides for Thyroid Dose Due to Inhalation
from a Passing Plume 2-5
4-1 Protective Action Guides for Exposure to Deposited
Radioactivity During the Intermediate Phase of a Nuclear
Incident 4-5
5-1 Recommended Protective Actions to Reduce Whole Body and Thyroid
Dose from Exposure to a Gaseous Plume 5-31
7-1 Gamma Exposure Rate and Effective Dose Equivalent (Corrected
for Radioactive Decay and Weathering) due to an Initial
2
Uniform Concentration of 1 pCi/m on Ground Surface 7-12
Vll
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page
7-2 Exposure Rate and the Effective Dose Equivalent (Corrected
for Radioactive Decay) due to an Initial Concentration of
of 1 pCi/m on Ground Surface 7-13
7-3 Example Calculation of Dose Conversion Factors for Gamma
Exposure Rate Measurements Based on Measured Isotopic
Concentrations 7-16
7-4 Dose Conversion Factors for Inhalation of Resuspended
Material 7-20
7-5 Skin Beta Dose Conversion Factors for Deposited
Radionuclides 7-22
7-6 Recommended Surface Contamination Screening Levels for
Emergency Screening of Persons and Other Surfaces at
Screening or Monitoring Stations in High Background
Radiation Areas 7-28
7-7 Recommended Surface Contamination Screening Levels for Persons
and Other Surfaces at Monitoring Stations in Low Background
Radiation Areas 7-29
FIGURES
5-1 Projected Whole Body Gamma Dose as a Function of Gamma Exposure
Rate, or Radioiodine Concentration in Air and the Projected
Exposure Time 5-17
5-2 Projected Thyroid Dose as a Function of Either Gamma Exposure
Rate, or Radioiodine Concentration in Air and the Projected
Exposure Time 5-19
5-3 Typical Values for XU/Q as a Function of Atmospheric Stability
Class and Downwind Distance 5-22
5-4 Radioiodine Release Correction Factor 5-27
5-5 Gamma Exposure Rate Finite Cloud Correction Factor 5-28
vm
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page
7-1 Response Areas 7-3
7-2 Time Frame of Response to a Major Nuclear Reactor Incident . 7-6
APPENDICES
A. Glossary
B. Risks to Health From Radiation Doses That May Result From
Nuclear Incidents
C. Protective Action Guides for the Early Phase: Supporting
Information (Reserved)
D. Background for Protective Action Recommendations: Accidental
Contamination of Food and Animal Feeds
E. Protective Action Guides for the Intermediate Phase
(Relocation) Background Information
F. Radiation Protection Criteria for the Late Phase: Supporting
Information (Reserved)
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CHAPTER 1
Overview
1.0 Introduction
Public officials, in discharging their responsibility to protect the
health of the public during hazardous situations, will usually be faced
with decisions that must be made in a short period of time. A number of
factors influencing the choice of protective actions will exist, so that
the decisions may be complex. Further, all of the information needed to
make the optimum choice will usually not be immediately available. In
such situations, it will therefore be helpful if the complexity of the
decisions needed can be reduced by careful planning during the formulation
of emergency response plans.
The U.S. Environmental Protection Agency has developed this manual in
order to assist public officials in planning for nuclear incidents. In
the context of this manual, a nuclear incident is defined as an event or a
series of events, either deliberate or accidental, leading to the release,
or potential release, into the environment of radioactive materials in
sufficient quantity to warrant consideration of protective actions. (The
term "incident" includes accidents, in the context of this manual.) A
radiological emergency may result from an incident at a variety of types
of facilities, including, but not limited to, those that are part of the
nuclear fuel cycle, defense and research facilities, and facilities that
produce or use radioisotopes, or from an incident connected with the
transportation or use of radioactive materials at locations not classified
as "facilities". This manual provides radiological protection criteria
intended for application to all nuclear incidents requiring consideration
of protective actions, other than nuclear war. It is designed for the use
of those in Federal, State, and local government with responsibility for
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emergency response planning. The manual also provides guidance for
implementation of the criteria. This has been developed primarily for
incidents at nuclear power facilities. Although this implementation
guidance may also be useful for application to other facilities, or uses
of radioactivity when the radionuclides involved or their physical
characteristics are different from those addressed here, emergency
response plans will usually require the development of additional
implementation procedures.
The decision to advise members of the public to take an action to
protect themselves from radiation from a nuclear incident involves a
complex judgment in which the risk avoided by the protective action must
be weighed in the context of the risks involved in taking the action.
Furthermore, the decision may have to be made under emergency conditions,
with little or no detailed information available. Therefore, considerable
planning is necessary to reduce to a manageable level the complexity of
decisions required to effectively protect the public at the time of an
incident.
An objective of emergency planning is to simplify the choice of
possible responses so that judgments are required only for viable and
useful alternatives when an emergency occurs. During the planning process
it is possible to make some value judgments and to determine which
responses are not required, which decisions can be made on the basis of
prior judgments, and which judgments must be made during an actual
emergency. From this exercise, it is then possible to devise operational
plans which can be used to respond to the spectrum of hazardous situations
which may develop.
The main contribution to the protection of the public from abnormal
releases of radioactive material is provided by site selection, design,
quality assurance in construction, engineered safety systems, and the
competence of staff in safe operation and maintenance. These measures can
reduce both the probability of an accident and the magnitude of potential
consequences. Despite these measures, the occurrence of nuclear incidents
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cannot be excluded. Accordingly, emergency response planning to mitigate
the consequences of an incident is a necessary supplementary level of
protection.
During a nuclear incident, when the source of exposure of the public
is not under control, the public usually can be protected only by some
form of intervention which will disrupt normal living. Such intervention
is termed protective action. A Protective Action Guide (PAG) is the
projected dose to standard man, or other defined individual, from an
unplanned release of radioactive material at which a specific protective
action to reduce or avoid that dose is warranted. The objective of this
manual is to provide such PAGs for the principal protective actions
available to public officials during a nuclear incident, and to provide
guidance for their use.
1.1 Nuclear Incident Phases and Protective Actions
It is convenient to identify three time phases which are generally
accepted as being common to all nuclear incident sequences; within each,
different considerations apply to most protective actions. These are
termed the early, intermediate, and late phases. Although these phases
cannot be represented by precise periods and may overlap, they provide a
useful framework for the considerations involved in emergency response
planning.
The early phase (also referred to as the emergency phase) is the
period at the beginning of a nuclear incident when immediate decisions for
effective use of protective actions are required and must therefore usually
be based primarily on the status of the nuclear facility (or other incident
site) and the prognosis for worsening conditions. When available, predic-
tions of radiological conditions in the environment from the condition of
the source or actual environmental measurements may also be used.
Protective actions based on the PAGs may be preceded by precautionary
actions during this period. This phase may last from hours to days.
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The intermediate phase is the period beginning after the source and
releases have been brought under control and reliable environmental
measurements are available for use as a basis for decisions on additional
protective actions. It extends until these additional protective actions
are terminated. This phase may overlap the early and late phase and may
last from weeks to many months.
The late phase (also referred to as the recovery phase) is the period
beginning when recovery action designed to reduce radiation levels in the
environment to acceptable levels for unrestricted use are commenced, and
ending when all recovery actions have been completed. This period may
extend from months to years.
The protective actions available to avoid or reduce radiation dose
can be categorized as a function of exposure pathway and incident phase,
as shown in Table 1-1. Evacuation and sheltering (supplemented by bathing
and changes of clothing), are the principal protective actions for use
during the early phase to protect the public from exposure to direct
radiation and inhalation from an airborne plume. It may also be
appropriate to initiate protective action for milk during this period, and
in cases where emergency response plans include procedures for the
issuance of stable iodine (FE-85), this may be an appropriate protective
action for the early phase.
Some protective actions are not addressed by these PAGs. Although
the use of simple, ad hoc respiratory protection may be applicable for
supplementary protection in some circumstances, this protective action is
primarily for use by emergency workers. The control of access to areas is
a protective action whose introduction is coupled to a decision to
implement one of the other early or intermediate phase protective actions
and is not discussed separately.
Relocation and decontamination are the principal protective actions
for protection of the public from whole body external exposure due to
deposited material and from inhalation of any resuspended radioactive
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TABLE 1-1. EXPOSURE PATHWAYS, INCIDENT PHASES,
AND PROTECTIVE ACTIONS.
POTENTIAL EXPOSURE PATHWAYS
AND INCIDENT PHASES
PROTECTIVE
ACTIONS
1. External radiation from
facility
2. External radiation from plume
3. Inhalation of activity in
plume
4. Contamination of skin and
clothes
5. External radiation from
ground deposition of activity
6. Ingestion of contaminated
food and water
7. Inhalation of resuspended
activity
Early
Intermediate
Late
Sheltering
Evacuation
Control of access
Sheltering
Evacuation
Control of access
Sheltering
Administration of stable iodine
Evacuation
Control of access
Sheltering
Evacuation
Decontamination of persons
Evacuation
Relocation
Decontamination of land
and property
Food and water controls
Relocation
Decontamination of land
and property
Note: The use of stored animal feed and uncontaminated water to limit the uptake of radionuclides
by domestic animals in the food chain can be applicable in any of the phases.
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participate materials during the intermediate and late phases. It is
assumed that decisions will be made during the intermediate phase
concerning whether relocated areas will be decontaminated and reoccupied,
or condemned and the occupants permanently relocated. The second major
type of protective action during the intermediate phase encompasses
restrictions on the use of contaminated food and water. This protective
action, in particular, may overlap the early and late phases.
It is necessary to distinguish between evacuation and relocation with
regard to incident phases. Evacuation is the urgent removal of people
from an area to avoid or reduce high-level, short-term exposure, usually
from the plume or deposited activity. Relocation, on the other hand, is
the removal or continued exclusion of people (households) from
contaminated areas to avoid chronic radiation exposure. Conditions may
develop in which some groups who have been evacuated in an emergency may
be allowed to return based on the relocation PAGs, while others may be
converted to relocation status.
1.2 Basis for Selecting Protective Action Guides
The PAGs in this manual incorporate the concepts and guidance
contained in Federal Radiation Council (FRC) Reports 5 and 7 (FR-64 and
FR-65). One of these is that the decision to implement protective actions
should be based on the projected dose that would be received if the
protective actions were not implemented. However, since these reports
were issued, considerable additional guidance has been developed on the
subject of emergency response (IC-84, IA-89). EPA considered the
following four principles in establishing values for the PAGs:
1. Acute effects on health (those that would be observable within a
short period of time and which have a dose threshold below which
such effects are not likely to occur) should be avoided.
2. The risk of delayed effects on health (primarily cancer and
genetic effects for which linear nonthreshold relationships to
dose are assumed) should not exceed upper bounds that are judged
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to be adequately protective of public health under emergency
conditions, and are reasonably achievable.
3. PAGs should not be higher than justified on the basis of
optimization of cost and the collective risk of effects on
health. That is, any reduction of risk to public health
achievable at acceptable cost should be carried out.
4. Regardless of the above principles, the risk to health from a
protective action should not itself exceed the risk to health
from the dose that would be avoided.
The above principles apply to the selection of any PAG. Similar
principles have been proposed for use by the international community
(IA-89). Appendices C and E demonstrate their application to the choice
of PAGs for evacuation and relocation. Although in establishing the PAGs
it is prudent to consider a range of source terms to assess the costs
associated with their implementation, the PAGs are chosen so as to be
independent of the magnitude or type of release.
1.3 Planning
The planning elements for developing radiological emergency response
plans for nuclear incidents at commercial nuclear power facilities are
provided in NUREG-0654 (NR-80), which references the PAGs in this Manual
as the basis for emergency response. Planning elements for other types of
nuclear incidents should be developed using similar types of
considerations.
NUREG-0396 (NR-78) provides guidance for nuclear power facilities on
time frames for response, the types of releases to be considered,
emergency planning zones (EPZ), and the effectiveness of various
protective actions. The size and shape of the recommended EPZs were only
partially based on consideration of the numerical values of the PAGs. A
principle additional basis was that the planning zone for evacuation and
sheltering should be large enough to encompass urban and rural areas and
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involve the various organizations needed for emergency response. This
consideration is appropriate for any facility requiring an emergency
response plan involving offsite areas. Experience gained in exercises is
then expected to provide an adequate basis for expanding the response to
an actual incident to larger areas, if needed. It is also noted that the
10-mile radius EPZ for evacuation is large enough to avoid exceeding the
evacuation PAGs at its boundary for low-consequence, nuclear reactor,
core-melt accidents and to avoid early fatalities for high-consequence,
nuclear reactor core-melt accidents. The 50-mile EPZ for ingestion
pathways was selected to account for the proportionately higher doses via
ingestion compared to inhalation and whole body external exposure pathways.
1.4 Implementation of Protective Actions
The sequence of events during the early phase includes evaluation of
conditions at the location of the incident, notification of responsible
authorities, prediction or evaluation of potential consequences to the
general public, recommendations for action, and implementing protection of
the public. In the early phase of response, the time available to
implement the most effective protective actions may be limited.
Immediately upon becoming aware that an incident has occurred that
may result in exposure of the population, responsible authorities should
make a preliminary evaluation to determine the nature and potential
magnitude of the incident. This evaluation should determine whether
conditions indicate a significant possibility of a major release and, to
the extent feasible, determine potential exposure pathways, population at
risk, and projected doses. The incident evaluation and recommendations
should then be presented to emergency response authorities for action. In
the absence of recommendations for protective actions in specific areas
from the official responsible for the source, the emergency plan should,
where practicable, provide for protective action in predesignated areas.
Contrary to the usual situation during the early phase, dose
projections used to support protective action decisions during the
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intermediate and late phases will be based on measurements of environmental
radioactivity and dose models. Following relocation of the public from
affected areas to protect them from exposure to deposited materials, it
will also be necessary to compile radiological and cost of decontamination
data to form the basis for radiation protection decisions for recovery.
The PAGs do not imply an acceptable level of risk for normal
(nonemergency conditions). They also do not represent the boundary
between safe and unsafe conditions, rather, they are the approximate
levels at which the associated protective actions are justified.
Furthermore, under emergency conditions, in addition to the protective
actions specifically identified for application of PAGs, any other
reasonable measures available should be taken to minimize radiation
exposure of the general public and of emergency workers.
References
FE-85 FEDERAL EMERGENCY MANAGEMENT AGENCY. Federal Policy on
Distribution of Potassium Iodide around Nuclear Power Sites for
Use as a Thyroidal Blocking Agent. Federal Register 50-142, p.
30256, July 24, 1985.
FR-64 FEDERAL RADIATION COUNCIL. Radiation Protection Guidance for
Federal Agencies. Federal Register, Volume 29, pp. 12056-7,
August 22, 1965.
FR-65 FEDERAL RADIATION COUNCIL. Radiation Protection Guidance for
Federal Agencies. Federal'Register, Volume 30, pp. 6953-5, May
22, 1965.
IA-89 INTERNATIONAL ATOMIC ENERGY AGENCY. Principles for Establishing
Intervention Levels for the Protection of the Public in the
Event of a Nuclear Accident or Radiological Emergency. Safety
Series No. 72, revision 1, in press. International Atomic
Energy Agency, Vienna, Austria.
IC-84 INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION. Protection
of the Public in the Event of Major Radiation Accidents:
Principles for Planning, ICRP Publication 40, Pergamon Press,
Oxford, England, 1984.
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NR-78 NUCLEAR REGULATORY COMMISSION. Planning Basis for the
Development of State and Local Government Radiological Emergency
Response Plans in Support of Light Water Nuclear Power Plants.
(1978). U.S. Nuclear Regulatory Commission, Washington, D. C.
20555.
NR-80 NUCLEAR REGULATORY COMMISSION. Criteria for Preparation and
Evaluation of Radiological Emergency Response Plans and
Preparedness in Support of Nuclear Power Plants. (1980). U.S.
Nuclear Regulatory Commission, Washington, D. C. 20555.
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CHAPTER 2
Protective Action Guides for the Early Phase*
(Exposure to Airborne Radioactive Materials)
2.0 Introduction
Following an incident involving a release of radioactive
material to the atmosphere, there may be a need for rapid action
co protect the public from radiation exposure from inhalation
and/or from whole body external radiation. This chapter provides
Protective Action Guides (PAGs) for whole body external gamma
radiation and for inhalation of radioactive material in an air-
borne plume. A person who is exposed to the plume of airborne
radioactive materials may also be exposed at a later date from
contaminated food, water, or other pathways. However, the PAGs
in this chapter refer only to the exposure received directly
from the airborne plume. The emergency response situation addressed
in this chapter is the period from initiation of an atmospheric
release until perhaps two to four days after the event occurs.
During this period, the principal effort would be directed toward
protection of the public from direct exposure to the plume or from
inhalation of radioactive material in the plume.
Ic is important to recognize that the PAGs are defined in
terms of projected dose. Projected dose is the dose that would be
received by the population if no protective action were taken. For
This Cnapter appears here in the form it was published in 1980; a
revised version with broader applicability than this version, which
applies primarily to airborne plumes for power reactors, is currently
under review.
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these PAGs, the projected dose does not include dose that may have
been received prior to the time of estimating the projected dose.
For protective actions to be most effective, they must be instituted
before exposure to the plume begins. PAGs should be considered
mandatory values for purposes of planning, but under accident con-
ditions, the values are guidance subject to unanticipated conditions
and constraints such that considerable judgment may be required for
their application.
2.1 Whole Body External Exposure
A radioactive plume will consist of gaseous and/or particulate
material. Either of these can result in whole body external expo-
sure. Measurements or calculations of environmental levels of
radioactivity are usually in terms of exposure. To translate from
whole body gamma exposure to whole body dose requires a correction
factor of approximately 0.67. However, due to the many uncertain-
ties in projecting dose from exposure to a plume, it is generally
conservatively assumed that gamma exposure and whole body gamma
dose are equivalent.
Recommended PAGs for emergency response in the case of whole
body external exposure to radionuclides in the atmosphere are
summarized in table 2.1. These guidelines represent numerical
values as to when, under the conditions most likely to occur,
intervention is Indicated to avoid radiation exposure that would
otherwise result from the incident. When ranges are shown, the
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Table 2.1 Protective Action Guides for Whole Body
Exposure to Airborne Radioactive Materials
Projected Whole Body
Population at Risk Gamma Dose (Rom)
General population 1 to 5'*'
Emergency workers 25
Lifesaving activities 75
(&)wiien ranges are shown, the lowest value should be used if
there are no major local constraints in providing protection at
that level, especially to sensitive populations. Local con-
straints may make lower values impractical to use, but in no
case should the higher value be exceeded in determining the need
for protective action.
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lowest value should be used if there are no major local constraints
in providing protection at that level, especially to sensitive popu-
lations. Local constraints may make lower values impractical to use,
but in no case should the higher value be exceeded in determining the
need for protective action. The rationale and technical bases for the
numerical guides and their ranges are described in greater detail in
Reference (4_) and are summarized In Appendix C. It is recommended
that anyone responsible for applying these guides In a nuclear emergency
become familiar with the rationale on which the guidance was based.
2.2 Inhalation Dose
The gaseous portion of a radioactive plume may consist of
noble gases and/or vapors such as radioiodines. The noble gases
will not cause as much dose from Inhalation as from whole body
external exposure and therefore need not be considered as a
separate contributor to inhalation exposure. The principal
inhalation dose will be from the iodines and partlculate material
In the plume.
2.2.1 Exposure to Radioiodines in a Plume
Due to the ability of the thyroid to concentrate Iodines,
the thyroid dose due to Inhaling radioiodines may be hundreds
of times greater than the corresponding whole body external
gamma dose that would be received. The PAGs for thyroid dose
due to inhalation from a passing plume are shown in table 2.2.
The technical support for their development is provided in
reference (4) and is summarized in Appendix C.
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Table 2.2 Protective Action Guides for Thryoid Dose
Due to Inhalation from a Passing Plume
Projected Thyroid Dose
Population at Risk rem
General population 5-25
Emergency workers 125
Lifesaving activities (b)
'a'When ranges are shown, the lowest value should be used if
there are no major local constraints in providing protection at
that level, especially to sensitive populations. Local con-
straints may make lower values impractical to use. but in iio
case (mould cne nignei vaxue be exceeded IB uetermining me need
for protective action.
No specific upper limit is given for thyroid exposure
since in the extreme case complete thyroid loss might be an
accent-able penalty for a life saved. However, this should
not be necessary if respirators and/or thyroid protection for
rescue personnel are available as the result of adequate
planning.
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2.2.2 Exposure to Particulate Material in a Plume
This section is being developed.
2.3 Interpretation of PAGs
The guides for the general population listed in tables
2.1 and 2.2 were arrived at in consideration of protection of
the public from early effects of radiation and maintaining the
delayed biological effects at a low probability. Consideration
has been made of the higher sensitivity of children and pregnant
women and the need to protect all members of the public. Con-
sideration has also been made that personnel may continue to
be exposed via some pathways after the plume passes, and that
additional PAGs may have to be applied to these exposure pathways.
Where a range of values is presented, the lower guide is a
suggested level at which the responsible officials should consider
initiating protective action particularly for the more sensitive
populations Indicated above. The higher guide is a mandatory
level at which the respective governmental agency should plan to
take effective action to protect the general public unless the
action would have greater risk than the projected dose.
At projected doses below the lower guide, responsible
officials may suggest voluntary action available to the public
at risk. This should be done with the philosophy that popula-
tion doses be kept as low as possible as long as the effects of
2.6
-------
action are not more hazardous Chan Che projected dose. The
concept of voluntary action and the types of action that may be
considered were discussed In Chapter 1.
The need for selected populations, such as emergency response
team members and persons involved in lifesaving activities, to be
allowed higher exposures than the general public is in line with
policies wherein these categories of individuals normally accept
greater risk. Public safety and nuclear plant personnel will be
essential to provide services for the public even though they may
receive a greater radiation exposure.
In the event greater exposures to selected populations are
required to save lives, these should be taken. However, if the
radiation Injury In these lifesaving activities Is excessive,
the harm may exceed the good, so some restrictions must be made.
Because of the variations in sensitivity of Che population
to radiation effects and in local conditions (weather, etc.), a
range of values is recommended for the general population. Where
selective protective actions (i.e. evacuation) for the general
population is possible, children and women of childbearing age
should be protected at the lower levels of the range. A further
interpretation of the range is that plans should be made to consider
organized protective action at the lower end of the range whereas it
is mandatory that plans be made to implement protective action at the
upper end. However, if no constraints existed, the lower range should
2.7
-------
always be used. Since constraints exist on a local basis under
different conditions, the range allows adjustment by local.
officials during the planning stage for special local problems
as discussed in Chapter 1.
The values given for emergency workers recognize the need
for some civil functions to continue in the event of an evacu-
ation of the general population. The risks are considered to be
warranted when necessary on the basis of the individual exposure
and the benefits derived. In such cases, precautions should be
taken to minimize exposures to emergency workers.
PAGs for lifesaving missions are given for those persons
whose normal duties might involve such missions, i.e., police,
firemen, radiation workers, etc. These guides would normally
be limited to healthy males. No specific upper limits are
given for thyroid exposure since in the extreme case, complete
thyroid loss might be an acceptable penalty for a life saved.
However, this should not be necessary if appropriate protective
measures for rescue personnel are available as the result of
adequate planning. For example, respiratory protection and/or
stable iodine for blocking thyroid uptake of radlolodine should
be available to the extent possible for personnel involved in
lifesaving missions and other emergency actions. The issuance
of stable iodine must be in accordance with state medical procedures.
2.8
-------
CHAPTER 3
Protective Action Guides for the Intermediate Phase*
(Food and Mater)
a) Accidental Radioactive Contamination of Human Food and Animal
Feeds; Recommendations for State and Local Agencies*
b) Drinking Water**
* These recommendations were published by FDA in 1982.
**Protective action recommendations for drinking water are under
development by EPA.
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Federal Register / Vol. 47, No. 205 / Friday, October 22. 1982 / Notices 47073
DEPARTMENT OF HEALTH AND
HUMAN SERVICES
Food and Drug Administration
(Docket No. 76M-0050]
Accidental Radioactive Contamination
o1 Human Food and Animal Feed*;
Recommendatlona tor State and Local
Agencies
AGENCY: Food and Drug Administration.
ACTION; Notice.
SUMMARY: The Food and Drug
Administration (FDA) is publishing this
notice to provide to State and local
agencies responsible for emergency
response planning for radiological
incidents recommendations for taking
protective actions in the event that an
incident causes the contamination of
human food or animal feeds. These
recommendations can be used to
determine whether levels of radiation
encountered in food after a radiological
incident warrant protective action and
to suggest appropriate actions that may
be taken if action is warranted. FDA has
a responsibility to issue guidance on
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47074 Federal Register / Vol. 47, No. 205 / Friujy. October 22. 1902 / Notices
appropriate planning actions necessary
for evaluating and preventing
contamination of human food and
animal feeds and on the control and use
of these products should they become
contaminated.
FOR FURTHER INFORMATION CONTACT:
Gail D. Schmidt, Bureau of Radiulogic.il
Health (HFX-1). Food and Drug
Administration. 5600 Fishers Lane.
Rockville, MD 20857. 301-443-2050.
SUPPLEMENTARV INFORMATION:
Background
This guidance on accidental
radioactive contamination of food from
fixed nuclear facilities, transportation
accidents, and fallout is part of a
Federal interagency effort coordinated
by the Federal Emergency Management
Agency (FEMA). FEMA issued a final
regulation in the Federal Register of
March 11,1982 (47 FR 10758). which
reflected governmental reorganizations
and reassigned agency responsibilities
for radiological incident emergency
response planning. A responsibility
assigned to the Department of Health
and Human Services (HHS) (and in turn
delegated to FDA) is the responsibility
to develop and specify to State and local
governments protective actions and
associated guidance for human food and
animal feed.
In the Federal Register of December
15,1978 (43 FR 58790), FDA published
proposed recommendations for State
and local agencies regarding accidental
radioactive contamination of human
food and animal feeds. Interested
persons were given until February 13,
1979 to comment on the proposal.
Twenty-one comments were received
from State agencies, Federal agencies,
nuclear utilities, and others. Two of the
comments from environmentally
concerned organizations were received
after the March 28.1979 accident at
Three Mile Island, which increased
public awareness of protective action
guidance. Although these comments
were received after the close of the
comment period, they were considered
by the agency in developing these final
recommenda tiona.
The Office of Radiation Programs.
Environmental Protection Agency (EPA),
submitted a detailed and exhaustive
critique of the proposed
recommendations. EPA addressed the
dosimetry data, the agricultural models
used in calculating the derived response
levels, and the philosophical basis for
establishing the numerical value of the
protective action guides. FDA advises
that, to be responsive to the EPA
comments, FDA staff met with staff of
the Office of Radiation Programs. EPA,
during the development of these f.nul
recommendations. Although EPA's
formal comments are responded to in
this notice, EPA stdff reviewed a draft of
the final recommendations, and FLJA
has considered their additional informal
comments. These contacts were
considered appiopnate because EPA
has indicated that it intends to use the
recommendations as the basis for
revising its guidance to Federal agencies
on protpctive a< lion guides for
radioactivity in food.
Protective Action Guidance
Although not raised in the comments
received, FDA has reconsidered its
proposal to codify these
recommendations in 21 CFR Part 1090.
Because these recommendations are
voluntary guidance to Slate and local
agencies (not regulations). FDA has
decided not to codify the
recommendations; rather, it is issuing
them in this notice. Elsewhere in this
issue of the Federal Register, FDA is
withdrawing the December 15.1978
proposal.
The recommendations contain basic
criteria, defined as protective action
guides (PAG's), for establishing the level
of radioactive contamination of human
food or animal feeds at which action
should be taken to protect the public
health and assure the safety of food. The
recommendations also contain specific
guidance on what emergency protective
actions should be taken to prevent
further contamination of food or feeds or
to restrict the use of food, as well as
more general guidance on the
development and implementation of
emergency action. The PAG's have been
developed on the basis of
considerations of acceptable risk to
identify that level of contamination at
which action is necessary to protect the
public health.
In preparing these recommendations.
FDA has reviewed and utilized the
Federal guidance on protective actions
contained in Federal Radiation Council
(FRC) Reports No. 5. July 1964 (Ref. 1)
and No. 7. May 1965 (Ref. 2] The
Federal guidance provides that each
Federal agency, by virtue of its
immediate knowledge or its operating
problems, would use the applicable FRC
guides as a basis for developing detailed
standards to meet the particular needs
of the agency. FDA's recommendations
incorporate the FRC concepts and the
FRC guidance that protective actions, in
the event of a contaminating accident,
should be based on estimates of the
projected radiation dose that would be
received in the absence of taking
protective actions. Similarly, protective
actions should be implemented for a
s jfficicnt time to avoid most of the
projected radiation dose. Thus, the
PAC's define the numerical value of
projected radiation doses for which
protective actions are recommended.
FDA has reviewed the recent report of
Ihc National Academy of Sciences/
Nutionul Rcsc;irch Council (Ref. 3) on
radiation risks and biological effects
data thiil became available after
publication of the FRC guidance and has
reviewed the impact of taking action m
Ihc pjisture/cow/milk/person pathway
;r. light of the current concerns in
rudiiition protection. Based on these
considerations and the comments
received on the proposed
recommendations, FDA has concluded
that protective actions of low impact
should be undertaken at projected
radiriliun doses lower than those
recommended by FRC (Refs. 1 and 2).
Accordingly, FDA is recommending low-
impact protective actions (termed the
Preventive PAG) at projected radiation
doses of 0.5 rem whole body and 1.5 rem
thyroid. FDA intends that such
protective actions be implemented to
prevent the appearance of radioactivity
in food at levels that would require its
condemnation. Preventive PAG's
include the transfer of dairy cows from
fresh forage (pasture) to uncontaminated
stored feed and the diversion of whole
milk potentially contaminated with
short-lived radionuclides to products
with a long shelf life to allow
radioactive decay of the radioactive
material.
In those situations where the only
pi elective actions that are feasible
present high dietary and social costs or
impacts (termed the Emergency PAG)
action is recommended at projected
radiation doses of 5 rem whole body
and 15 rem thyroid. At the Emergency
PAG level responsible officials should
isolate food to prevent its introduction
into commerce and determine whether
condemnation or other disposition is
appropriate. Action at the Emergency
PAG level is most likely for the
population that is near to the source of
radioactive contamination and that
consumes home-grown produce and
milk.
The PAG's represent FDA's judgment
as to that level of food contamination
resulting from radiation incidents at
which action should be taken to protect
the public health. This is based on the
agency's recognition that safety involves
the degree to which risks are judged
acceptable. The risk from natural
disasters (approximately a one in a
million annual individual risk of death)
and the risk from variations in natural
background radiation have provided
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Federal Register / Vol. 47. No. 205 / Friday. October 22. 1982 / Notices 47075
perspective in selecting the PAG values.
This issue is further discussed in the
responses to specific comments later in
this notice, especially in paragraph 9. A
more detailed treatment of the rationale.
risk factors, dosimetric and agricultural
models, and methods of calculation is
contained in the "Background for
Protective Action Recommendations;
Accidental Radioactive Contamination
of Food and Animal Feeds" (Ref. 22).
Organ PAG Values
Current scientific evidence, as
reflected by BEIR-I [Ref. 18).
UNSCEAR-1977 (Ref. B). and BEIR-III
(Ref. 3). indicates that the relative
importance of risk due to specific organ
exposure is quite different from the
earlier assumptions. The International
Commission on Radiological Protection
(ICRP) clearly recognized this in its 1977
recommendations (ICRP-26 (Ref. 6)).
which changed the methodology for
treating external and internal radiation
doses and the relative importance of
specific organ doses. ICRP-26 assigned
weighting factors to specific organs
based on considerations of the
incidence and severity (mortality) of
radiation cancer induction For the
radionuclides of concern for food PAG's.
ICRP-26 assigned weighting factors of
0 03 for the thyroid and 0.12 for red bone
marrow. Thus, the organ doses equal in
risk to l rem whole body radiation dose
are 33 rem to the thyroid and 8 rem to
Red bone marrow. (The additional
ICRP-26. nonstochastic limit, however.
restricts the thyroid dose to 50 rem or 10
times the whole body occupational limit
of 5 rem.)
In the Federal Register of January 23.
1981 (46 FR 7836], EPA proposed to
revise the Federal Radiation Protection
Guidance for Occupational Exposures
using the ICRP approach for internal
organ radiation doses, modified to
reflect specific EPA concerns. The EPA
proposal has been subject to
considerable controversy. Also, the
National Council on Radiation
Protection and Measurements (NCRP)
curently is evaluating the need to revise
its recommendations. FDA does not.
however, expect the protection model
for internal organ radiation doses to be
resolved rapidly in the United States
and has based the relative PAG dose
assignments in these recommendations
on current U.S. standards and the 1971
recommendations in NCRP-39 (Ref. 19).
Thus, the red bone marrow is assigned
the same PAG dose as the whole body
(0.5 rem Preventive PAG), and the
thyroid PAG is greater by a factor of
three (l.S rem Preventive PAG). This
results in PAG assignments for the
thyroid and red bone marrow that are
lower by factors of 3.3 and 8.
respectively, than values based on
ICRP-26 (Ref. 6). FDA advises that it
will make appropriate changes in
recommendations for internal organ
doses when a consensus in the United
States emerges.
Analysis of Comments
The following is a summary of the
comments received on the December 15,
1978 proposal and the agency's response
to them:
1. Several comments requested
clarification of the applicability and
compatibility of FDA's
recommendations with other Federal
actions, specifically the PAG guidance
of EPA (Ref. 7). the FRC Reports No. 5
(Ref. 1) and No. 7 (Ref. 2). and the
Nuclear Regulatory Commission (NRC)
definition of "Extraordinary Nuclear
Occurrence" in 10 CFR Part 140. A
comment recommended that the term,
"Protective Action Guide (PAG)", not be
used because that term traditionally has
been associated with the FRC. and the
general public would confuse FDA's
recommendations with Federal
guidance.
The FRC Report No. 5 specifically
recommended that the term, "protective
action guide." be adopted for Federal
use. The report defines the term as the
"projected absorbed dose to the
individuals in the general population
which warrants protective action
following a contaminating event." a
concept that is addressed by FDA's
recommendations. To use the concept
with a different description would, in
FDA's opinion, be unnecessanly
confusing to State and local agencies as
well as Federal agencies.
These recommendations are being
issued to fulfill the HHS responsibilities
under FEMA's March 11.1982
regulation. FDA fully considered FRC
Reports No. 5 and No. 7 and the basic
concepts and philosophy of the FRC
guidance form the basis for these
recommendations. The specific PAG
values are derived response levels
included in these recommendations are
based on current agricultural pathway
and radiation dose models and current
estimates of risk. The FRC guidance
provided that protective actions may be
justified at lower (or higher) projected
radiation doses depending on the total
impact of the protective action. Thus,
FDA's recommendation that protective
actions be implemented at projected
radiation doses lower than those
recommended by FRC doses is
consistent with the FRC guidance. The
FRC guidance is applicable to Federal
agencies in their radiation protection
activities. FDA's recommendations are
for use by Slate and local agencies in
response planning and implementation
of protective actions in the event of a
contaminating incident. Further. FDA's
recommendations would also be used by
FDA in implementing its authority for
food in interstate commerce under the
Federal Food. Drug, and Cosmetic Act.
FDA's recommendations are being
forwarded to EPA as the basis for
revising Federal guidance on food
accidentally contaminated by
radionuclides. EPA has advised FDA
that it intends to forward the FDA
recommendatiojis to the President under
its authority to "advise the President
with respect to radiation matters
directly or indirectly affecting health,
including guidance for all Federal
agencies in the formulation of radiation
standards * * *". (This authority was
transferred to EPA in 1970 when FRC
was abolished.)
The recommendations established in
this document apply only to human food
and animal feeds accidentally
contaminated by radionuclides. They
should not be applied to any other
source of radiation exposure. EPA
already has issued protective action
guidance for the short-term accidental
exposure to airborne releases of
radioactive materials and intends also
to forward the EPA guides to the
President as Federal guidance. EPA also
is considering the development of
guidance for acidentally contaminated
water and for long-term exposures due
to contaminated land, property, and
materials. Guidance for each of these
exposure pathways is mutually
exclusive. Different guidance for each
exposure pathway is appropriate
because different criteria of risk, cost.
and benefit are involved. Also, each
exposure pathway may involve different
sets of protective or restorative actions
and would relate to different penods of
time when such actions would be taken.
2. Several comments expressed
concern about radiation exposure from
multiple radionuclides and from multiple
pathways, e.g., via inhalation, ingestion.
and external radiation from the cloud
(plume exposure) and questioned why
particular pathways or radionuclides
and the does received before
assessment were not addressed in the
recommendations. Several comments
recommended that the PAG's include
specific guidance for tap water (and
potable water). Other comments noted
that particular biological forms of
specific radionuclides (i.e.,
cyanocobalamin Co 60). would lead to
significantly different derived response
levels.
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•J7076
Federal Register / Vol. 47. No. 205 / Friday. October 22, 1982 / Notices
FDA advises that the PAG's and the
protective action concepts of FRC apply
to fictions taken to avoid or prevent
projected radiation dose (or future
dose). Thus, by definition, the PAG's for
food do not consider the radiation closrs
already incurred from the plume
pathway or from other sources. The
population potentially exposed by
ingestion of contaminated food can be
divided into that population near the
source of contamination and a generally
much larger population at distances
where the doses from the cloud are not
significant. The NRC regulations provide
thdt State and local planning regarding
plume exposure should extend for 10
miles and the ingestion pathway should
extend for 50 miles (see 45 FR 55402;
August 19.1980). The total population
exposed by ingestion. however, is a
function of the animal feed and human
food production of any given area and is
not limited by distance from the source
of contamination. Exposure from
multiple pathways would not be a
concern for the more distant population
group Further, individuals in this larger
population would most likely receive
doses smaller than that projected for
continuous intake because the
contaminated food present in the retail
distribution system would be replaced
by uncontaminated food.
FRC Report No. 5 states that, fur
repetitive occurrences, the total
projected radiation dose and the total
impact of protective actions should be
considered. Similar considerations on a
case-by-case basis would then appear to
be appropriate in the case of multiple
exposures from the plume and the
ingestion pathway. Accordingly, the
final recommendations are modified to
note that, specifically in the case of the
population near the site that consumes
locally grown produce, limitations of the
total dose should be considered (see
paragraph (a)(2)). The agency concludes.
however, that a single unified PAG
covering multiple pathways, e.g..
external radiation, inhalation, and
ingestion is not practical because
different actions and impacts are
involved. Further. FDA's responsibility
in radiological incident emergency
reapon.se planning extends only to
human food and animal feeds.
The agency's primary charge is to set
recommended PAG dose commitment
limits for the food pathway. Thus.
deriving response levels for only the
radionuclides most likely to enter the
food chain and deliver the highest dose
to the population permits FDA to
establish recommendations that are
practical for use in an emergency. In
discussing with EPA the list of definitive
models, FDA and T.PA si.iffs ajjroi'd Hint
further pathway studies would be
useful Elsewhere in this notice. FDA
references models for other
radionur.lides. providing a resource fur
thosr requiting more details.
Thr chemic.-il form of radionuc lides in
the environment may he important wh»n
considering the derivation of an
appropriate "response level" in specific
situations, but would not change the
PAC's. which are in terms of projected
dose commitments. Cyanocobalamm Co
60 has not been identified as a likely
constituent of health importance to be
released from a nuclear reactor accident
and. therefore, the agency rejects the
recommendation that it provide derived
response levels for this radionuchde.
However, after reviewing current
agricultural and dose models, the
agency concludes that cesium-134 would
likely be released and has added it to
the tables in paragraph (d) of the
recommendations identifying
radionuclide concentrations equivalent
to the PAG response levels,
FDA rejects the comment
recommending that the PAG's include
guidance for water. A memorandum of
understanding between EPA and FDA
provides that FDA will have primary
responsibility over direct and indirect
additives and other substances in
drinking water (see 44 FR 42775: July 20.
1979). Thus. FDA defers to EPA for
developing guides specifically for
drinking water.
3. Three comments requested
clarification of the proposed
recommendations, including the time
over which the guides apply, the time of
ingestion required to reach the PAG. and
the time that protective actions should
be implemented.
FDA advises that the
recommendations are intended to
provide guidance for actions to be
implemented in an emergency, and the
duration of protective action should not
exceed 1 or 2 months. The agency
believes that the actions identified in
paragraphs (a) and (h) of the
recommendations should be continued
for a sufficient time to avoid most of the
emergency radiation dose and to assure
that the remaining dose is less than the
Preventive PAG. This period of time can
be estimated by considering the
effective half-life of the radioactive
material taking into account both
radioactive decay and weathering. Each
case must be examined separately
considering the actual levels of
contamination and the effective half-life
of the radioactive material present. For
the paslure/cow/milk pathway, the
effective half-lives are 5 days for iodine-
131
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Federal Register / VoL 47. No. 205 / Friday. October 22. 1982 / Notices
47077
shipment of contaminated foods from
Slates without sufficient resources and
what would be the applicable PAC.
FEMA. as the lead agency for the
Federal effort, is providing to Slates
guidance and assistance on emergency
response planning including evaluation
of projected doses. Also. NRC requires
nuclear power plant licensees to have
the capability to assess the off-site
consequences of radioactivity releases
and to provide notification to State and
local agencies (45 FR 55402: August 19.
1S80). FDA has authority under the
Fuderdl Food. Drug, and Cosmetic Act to
remove radioactively contaminated food
from the channels of interstate
commerce. In this circumstance. FDA
would use these PAG recommendations
as the basis for implementing
regulatory action.
Risk Estimates
7. Many comments questioned the risk
estimates on which FDA based the
proposed PAG's. The comments
especially suggested that risk estimates
from WASH-1400 (Ref. 4) were of
questionable validity. Other comments
argued that the proposed
recommondarions used an analysis of
only lethal effects: that they used an
absolute nsk model: and that genetic
effects were not adequately considered.
The nsk estimates themselves were
alleged to be erroneous because recent
studies show that doubling doses are
lower than are those suggested by
WASH=1400. The tinea capitis study by
Ron and Modan, which indicates an
increased probability of thyroid cancer
at an estimated radiation dose of 9 rem
to the thyroid (Ref. 5). was ated as
evidence that the PAG limits for the
thyroid were too high. The comments
requasred further identification and
support for using the cnbcal population
selected
Most of these issues were addressed
in tha preamble to the FDA proposal.
The final recommendations issued in
this notice employ the most recent nsk
estimates (somatic and genetic) of the
National Academy of Sciences
Committee on Biological Effects of
Ionizing Radiuti«n (Ref. 3).
The thyroid PAG limits are based on
the relative radiation protection guide
for thyroid compared to whole body
contained in NRC's current regulations
(10 CFR Part 20]. The denved response
levels for thyroid are based on nsk
factors for external x-ray irradiation.
Therefore, the criticism of the PAG
limifc for the thyroid is not applicable.
no "credit" having been taken for an
apparent lower radiation risk due to
iodine-131 irradiation of the thyroid
gland. Further, as discussed above
under "ORGAN PAG VALUES", the use
of BEIR-IU risk estimates or the ICRP-26
recommendations would result in jn
increase of the thyroid PAG relative to
the whole body PAG. For these reasons.
FDA believes the PAC limits for
projected dose commitment to the
thyroid are conservative when
considered in light of current knowledge
of radiation to produce equal health
risks from whole body and specific
organ doses.
Although it may be desirable to
consider total health effects, not just
lethal effects, there is a lack of data for
total health effects to use in such
comparisons. In the case of the
variability of natural background, as an
estimate of acceptable risk.
consideration of lethal effects or total
health effects is not involved because
the comparison is the total dose over a
lifetime.
Rational
8. Several comments questioned the
rational FDA used in setting the specific
PAG values included in the December
1978 proposal A comment from EPA
stated that the guidance levels should be
justified on the grounds that it is not
practical or reasonable to take
protective actions at lower risk levels.
Further. EPA argued that the protective
action concept for emergency planning
and response should incorporate the
principle of keeping radiation exposures
as low as reasonably achievable
(ALARA]. EPA noted that the principle
of acceptable risk involves a perception
of nsk that may vary from person to
person and that the implication that an
acceptable genetic risk has been
established should* be avoided.
FDA accepts and endorses the
ALARA concept but the extent to which
a concept, which is used in occupational
settings, should be applied to emergency
protective actions is not clear. To use
the ALARA concept as the basis for
specific PAG values and also require
ALARA during the implementation of
emergency protective actions appears to
be redundant and may not be practical
under emergency conditions.
FDA advises that these guides do not
constitute acceptable occupational
radiation dose limits nor do they
constitute acceptable limits for other
applications (e.g., acceptable genetic
nsk). The guides are not intended to be
used to limit the radiation dose that
people may receive but instead are to be
compared to the calculated projected
dose. i.e.. the future dose that the people
would receive if no protective action
were taken in a radiation emergency. In
this respect, the PAG'» represent trigger
levels calling for the initiation of
recommended protective actions. Once
the protective action IB initiated, it
should be executed so as to prevent as
much of the calculated projected dose
from being received as is reasonably
achievable. This does not mean.
however, that all doses above guidance
levels can be prevented.
Further, the guides are not intended to
prohibit taking actions at projected
exposures lower than the PAC values.
They have been derived for general
cases and are just what their name
implies, guides. Aa provided in F5C
Reports No. 5 and No. 7 ondaa
discussed in paragraph 1 of thi« notice.
in the absence of significant constraints.
responsible authority may End it
appropriate to implement low-impact
protective actions at projected radiation
doses less than those specified in the
guides. Similarly, high impact actions
may be justified at higher projected
doses. These judgments-must be made
according to the facts of each situation.
Paragraphs (a) (2) and (3) have been
added to the final recommendationa to
Incorporate this concept.
9. Several comments questioned the
adequacy of the level of Tiak judged
acceptable in deriving the proposed
PAG values. A comment stated that the
estimated one in a million annual
Individual nsk of death from natural
disasters is extremely conservative. EPA
suggested that comparative risk is
appropriate for perspective but not for
establishing the limits. EPA further
suggested that the population-weighted
average of the variability in natural
background dose or the variation in
dose due to the natural radioactivity in
food should be the basis for judging
acceptable risk.
FDA concludes that the differences
between EPA's suggested approach and
that employed by FDA largely involve
the semantics of the rationale
descriptions. Aa discussed in the
preamble to the proposal. FDA'believes
that safety (or a safe level of nakj needs
to be defined as the degree to which the
risks are judged acceptable, because it
is not passible to achieve zero risk from
human endeavors. Further. ICSP (Ref. 6)
recommends that, for a given
application involving radiation, the net
benefit to society should be positive.
considering the total costs and impacts
and the total benefit (this is termed
"justification"]. FDA believes that to
establish a PAC. the primary concern is
to provide adequate protection (or safe
level of nsk) for members of the public.
To decide on safety or levels of
acceptable risk to the public from a
contaminating event FDA introduced
the estimates of acceptable risk from
-------
47078
Federal Register / Vol 47. No 205 / Friday. October 22. 1982 / Notices
ndtural disastrrs and background
radiation These values provided
bcickground or perspective for FDA s
ludgment that the proposed PAG's
represent that level of food or feed
rddiation contamination at which
protective actions should be taken to
protect the public health: judgment
which, consistent with FRC Report No.
5, also involves consideration of the
impacts of the action and the possibility
of future events. The recommendations
are based on the assumption that the
occurrences of environmental
contamination requiring protective
actions in a particular area is an
unlikely event, that most individuals
will never be so exposed, and that any
individual is not likely to be exposed to
projected doses at the PAG level more
than once in his or her lifetime.
FDA continues to believe that the
average risks from natural disasters and
variation of background radiation
provide appropriate bases for judging
the acceptability of risk represented by
the Preventive PAG. These
recommendations incorporate the
philosophy that action should be taken
at the Preventive PAG level of
contamination to avoid a potential
public health problem. Should this
action not be wholly successful, the
Emergency PAG provides guidance for
taking action where contaminated food
is encountered. FDA expects that action
at the Emergency PAG level of
contamination would most likely
involve food produced for consumption
by the population near the source of
contamination. As discussed in
paragraph 2, this is also the population
which might receive radiation doses
from multiple pathways. Thus, the
Emergency PAG might be considered to
be an upper bound for limiting the total
radiation dose to individuals. FDA
emphasizes, however, that the
Emergency PAG is not a boundary
between safe levels and hazardous or
injury levels of radiation. Individuals
may receive an occupational dose of 5
rem each year over their working
lifetime with the expectation of minimal
increased risks to the individual.
Persons in high elevation areas such as
Colorado receive about 0.04 rem per
year (or 2.B rem in a lifetime) above the
average background radiation dose for
the United States population as a whole.
The Emergency PAG is also consistent
with the upper range of PAG's proposed
by EPA for the cloud (plume) pathway
(Ref.7j.
FDA agrees that a population-
weighted variable is as applicable to the
evaluation of comparative risks as is a
geographic variable. Arguments can be
m.idc for using either variable Because
prrsons rather than geographic arr.is
are the important parameter in the
evaluation of risk associated with these
guidrs, FDA has used populdtion-
weiyhhng in estimating the variability of
the annual external dose from ndtural
rddiation A recent EPA study (Ref 20)
indicates that the average population
dose from external background
radiation dose is 53 millirem [mrcm] per
year, and the variability m lifetime dose
taken as two standard deviations is
about 2,000 mrem. The proposal, which
indicated that the variation in external
background was about 600 mrem.
utilized a geographic weighting of State
averages.
Radioactivity in food contributes
about 20 mrem per year to average
population doses and about 17 mrem per
year of this dose results from potassium-
40 (Ref. 8). Measurements of potassium-
40 (and stable potassium) indicate that
variability (two standard deviations) of
the potassium-40 dose is about 28
percent or a lifetime dose of 350 mrem It
should be noted that body levels of
potassium are regulated by metabolic
processes and not dietary selection or
residence. The variation of the internal
dose is about one-fifth of the variation
from external background radiation.
FDA has retained the proposed
preventive PAG of 500 mrem whole
body even though the newer data
indicate a greater variation in external
background radiation.
FDA did not consider perceived risks
in deriving the proposed PAG values
because perceived risk presents
numerous problems in its
appropriateness and application If the
factor of perception is added to the
equation, scientific analysis is
impossible.
10. Two comments questioned the
assumptions that the Emergency PAG
might apply to 15 million people and
that the Preventive PAG might apply to
the entire United States. One comment
noted that 15 million persons are more
than that population currently within 25
miles of any United States reactor sites:
thus, using this figure results in guides
more restrictive than necessary. The
other comment noted that, by reducing
the population involved, and
unacceptably high value could result.
The ratio of total United States
population to the maximum number of
people in the vicinity of an operating
reactor could be erroneously interpreted
so that progressively smaller
populations would be subject to
progressively larger individual risks.
This is not the intent of the
recommendations. Hence, the risk from
natural disasters, the variation in the
population-weighted natural background
r.iji.ilion dose to the total population.
anu !he variation in dose due to
ingnstion of food, have been used to
provide the basis for the Preventive
PAG The basis for the Emergency PAG
involves considerations of (1) The ratio
between average and maximum
individual radiation doses (taken as 1 to
10). (2) the cost of low and high impact
protective actions. (3) the relative risks
from natural disasters, (4) health impact,
(5) the upper range of the PAG's
proposed by EPA (5 rem projected
radiation dose to the whole body and 25
rem projected dose to the thyroid), and
(6) radiation doses from multiple
pathways.
11. A comment, citing experience with
other contaminants, suggested that
further consideration should be given to
the problem of marketability of foods
containing low levels of radioactivity.
Marketability is not a concern for
PAG development. However, the
publication of the PAG's should enhance
marketability of foods because it will
enhance public confidence in food
safety. Also, FEMA has been
specifically directed to undertake a
public information program related to
radiation emergencies to allay public
fears and perceptions.
12. A comment noted the difficulty in
assessing the impacts of and the
benefits to be gained from protective
actions. Another comment suggested
that there were lower impact actions
which could be implemented to keep
food off the market until radiation levels
in the food approach normal
background.
The recommendation that planning
officials consider the impacts of
protective actions in implementing
action does not imply that a
mathematical analysis is required.
Rather, FDA intends that the local
situation, resources, and impacts that
are important in assuring effective
protective actions be considered in
selecting any actions to be implemented.
As discussed in paragraph 8. if the local
constraints permit a low impact action,
this can be appropriate at lower
projected doses. Because it is not
possible in general guidance to consider
fully all local constraints, the PAG's
represent FDA's judgment as to when
protective actions are appropriate.
Agricultural and Dose Models
13 Several comments noted errors
either in approach or calculations
regarding the proposed agricultural and
dose models, while others specifically
noted that there are newer and better
-------
Federal Register / Vol. 47. No. 205 / Friday. October 22, 1962 / Notices
47079
models for use in computation of the
derived response levels.
FDA appreciates the careful review
and the suggestions as to better data
and models. The references suggested.
as well as other current reports, have
been carefully reviewed and appropriate
ones are being used as the basis for
computation of the derived response
levels for the final PAG's. The specific
models and data being used are as
follows:
Agricultural Model—UCRU51939.1977
(Rcf.9).
Intake per unit deposition—Table B-l.
UCRU51939 (Ref. 9).
Peak milk activity—Equation 8. UCRL-
51939 (Ref. 9)
Area grazed by cow—45 square meters/
djy UCRL-51938 (Ref 9).
Initial retention on forage—0.5 fraction.
UCR1.-51939 (Ref 9)
Fcirrfgp yield—0 25 kilogram/square meter
(dry weight). UCRL-51939 (Ref. 9).
Milk consumption—0.7 liter/day in/anl,
ICRP-23.1974 (Ref. 10).—0.55 liter/day adult.
USDA. 1965 (Ref. 11}.
Dose conversion factors (rem per
microcune ingested).
Imto.
Kxhna-131
CoMim 134 „
Gjsmm-137
Slmn(ium-«fl
S r^-uum-90
16
0118
0071
0194
249
Htut
16
0068
0061
0012
070
Wetman and Anger.
1971 (Ret 12)
Adun— ORNL/NURE6/
TM-1M. 1978 (Rel
13)
from aduft based on
nlatwa body ««ght
70 kilograms (kg) end
7 7 kg and anecttw
tolomwn. 102 day*
and 19 5 days, adult
Wdinlant
respacAMry
NCRP No 52. 1977
(Re* 14)
Adult. ICRP-30. 1979
(Hal 15)
Infant Papwort*) and
Ve-nan 1973 (Rat
16)
The use of the newer agricultural
mode! (Ref 9) has resulted in a 20
prrcent increase in the iodme-131
derived response levels identified in
paragraph (d)(l) and (d)|2) of the
it'commerulations. Generally, similar
magmhiui- changes arc reflected in the
Jpnveil response levels for the other
radionuclides. Newer data on iodine-131
dose conversion factors (Ref. 17) would
have further increased the derived
response levels for that radionuchde by
about 40 percent but these data have
not been used pending their acceptance
hy United States recommending
•iiithonbes In addition, the proposal
contained a systematic error in that the
pasture derived response levels were
stated to be based on fresh weight but
were in fact based on dry weight. Fresh
weight values (X of dry weight values)
lire identified in the final
recommendations and are listed under
"Forage Concentration".
Other Comments
14. A comment addressed the
definition of the critical or sensitive
population for the tables in proposed
S 1090.400(d) and observed that there is
a greater risk per rem to the younger age
groups than to adults. Another comment
requested further explanation of the
relative ability to protect children and
adults.
FDA agrees that, ideally, the critical
segment of the population should be
defined in terms of the greatest risk per
unit intake. However, this would
introduce greater complexity into the
recommendations than is justified,
because the nsk estimates are uncertain.
The final recommendations provide
denved response levels for infants at the
Preventive PAG and infants and adults
for the Emergency PAG."
FDA has reexammed the available
data and concludes that taking action at
the Preventive PAG (based on the infant
as the critical or sensitive population)
will also provide protection of the fetus
from the mother's ingestion of milk. The
definition,of newborn infant in the
tables in paragraph (d) of the PAG's has
been revised to reflect this conclusion.
15. EPA commented that its
regulations governing drinking water [40
CFR Subchapler D) permit blending of
water to meet maximum contaminant
levels. EPA suggested that FDA's short-
term recommendations should be
compatible with the long-term EPA
regulations.
As stated in paragraphs 1 and 2 of this
notice. FDA's recommendations apply to
human food and animal feed, whereas
EPA is responsible for providing
guidance on contaminated water. Also.
as discussed in paragraph 3 of the
proposal, there is a long-standing FDA
policy that blending of food is unlawful
under the Federal Food, Drug, and
Cosmetic Act. Further, these guides are
intended Tor protective actions under
emergency situations and are not for
continuous exposure dppln.dtions. For
these reasons, FDA concludes (hdt the
differences between its
recommendations and EPA's regulations
are appropriate.
16. Two comments were received on
the adequacy or availability of
resources For sampling and analysis of
Stale, local, and Federal agencies and
the adequacy of guidance on sampling
procedures.
These recommendations are not
designed to provide a compendium of
sampling techniques, methods, or
resources. The Department of Energy
through its Interagency Radiological
Assistance Plan (IRAP) coordinates the
provision of Federal assistance and an
Offsite Instrumentation Task Force of
the Federal Radiological Preparedness
Coordinating Committee administered
by FEMA is developing specific
guidance on instrumentation and
methods for sampling food (Ref. 21).
Cost Analysis
17. Several comments argued that
FDA's cost/benefit analysis used to
establish the PAG levels was
inadequate. Comments stated that it is
not appropriate to assign a unique fixed
dollar value to the adverse health
effects associated with one person-ram
of dose.
FDA advises that its cost/benefit
analysis was not conducted to establish
the PAG levels. FDA considers such use
inappropriate in part because of-the
inability to assess definitively the total"
societal impacts (positive and negative)
of such actions. Rather, the cost/benefit
analysis was used to determine whether
protective actions at the recommended
PAG's would provide a net societal
benefit To make such an assessment it
is necessary to place a dollar value on-a
person-rem of dose.
18. Several comments also questioned
the appropriateness of the assumption in
the cost/benefit analysis of 23 days of
protective action, the need to address
radionuclides other than iodine-131, and
the need to consider the impact of other
protective actions.
The cost assessments have been
extensively revised to consider all the
radionuclides for which derived
response levels are provided in tfie
recommendations and to incorporate
updated cost data and risk estimates
(Ref. 22). The cost/benefit analysis is
limited to the condemnation of milk and
the use of stored feed because accident
analyses indicate that the milk pathway
is the most likely to require protective
action. Further, these two actions are
the most likely protective actions that
will be implemented.
FDA approached the cost/benefit
analysis by calculating the
concentration of radioactivity in milk at
which the cost of taking action equals
the risk avoided by the action taken on
a daily milk intake basis. The
assessment was done on a population
basis and considered only the direct
costs of the protective actions. The
analysis indicates that, for restricting
feed to stored feed, the cost-equals-
benefit concentrations are about one-
fiftieth to one-eightieth of the Preventive
PAG level (deri\ed peak milk
conccnlialion) for iodine-131, cesmm-
134. and cesium-137 and about one-third
-------
47080
Fedeial Register / Vol. 47. No. 205 / Friday. October 22. 1982 / Notices
of the level for strontium-89 and
strontium-90. For condemnation or milk.
based on value at the farm, the cosl-
equals-benefit concentrations are
similar fractions of the Emergency PAG
levels (derived peak milk
concentration). If condemnation of milk
is based on retail market value, the cost-
equals-benefit concentrations are
greater by a factor of two Thus, it
appears that protective actions at the
Preventive or Emergency PAC levels
will yield a net societal benefit
However, in the case of strontium-89
and strontium-90, protective action will
yield a benefit only for concentrations
greater than about one-third the derived
peak values. In the case of iodme-131.
cesium-134. and cesium-137, protective
actions could be continued to avoid 95
percent of the projected radiation dose
for initial peak concentrations at the
PAC level.
RolOfBDCM
The following information has been placed
on display in the Dockets Management
Branch (HFA-305), Food and Drug
Administration. Km. 4-62.5600 Fishers l-ane.
Rockville. MD 20857. and may be seen
between 9 a.m. and 4 p.m.. Monday through
Friday.
1 Federal Radiation Council. Memorandum
for the President. "Radiation Protection
Guidance for Federal Agencies." Federal
Register. August 22.1964 (29 FR 12056). and
Report No. 5 (July 1964).
2 Federal Radiation Council. Memorandum
for the President. "Radiation Protection
Guidance for Federal Agencies." Federal
Register." May 22.1965 (30 FR 6953). and
Report No. 7 (May 1965).
3 National Academy of Sciences/National
Research Council. "The Effects on Population
of Exposure to Low Levels of Ionizing
Radiation." Report of the Advisory
Committee on Biological Effects of Ionizing
Radiation (BE1R-I11) (1980).
4 United Slates Nuclear Regulatory
Commission. Reactor Safety Study. WASH-
1400. Appendix VI (October 1975).
5 Ron. E. and B Modan, "Benign and
Malignant Thyroid Neoplasms After
Childhood Irradiation for Tinea Capitis."
Journal of the National Cancer Institute. Vol
66. No. 1 duly 1980),
6 International Commission on
Radiological Protection (ICRP).
Recommendations of the International
Commission on Radiological Protection. ICRP
Publication 26. Annals of the ICRP. Pergamon
Press (1977).
7 Environmental Protection Agency.
"Miinual of Protective Action Guides and
Protective Actions for Nuclear Incidents."
EPA 520/1-75-001. revised June 1980
8 United Nations Scientific Committee on
the Effects of Atomic Radiation, 1977 Report.
United Nations. New York (1977)
9 Ng. Y. C. C S. Colsher. D ] Qumn. and
S E Thompson, 'Transfer Coefficients for
the Prediction of the Dose to Man Via the
Forage-Cow-Milk Pathway from
Radionuclides Released to the Biosphere."
UCRL-51939. Lawrence Livermore
Laboratory (July 15.1977)
10 International Commission on
Radiological Protection. Report of a Task
Group of Committee 2 on Reference Mdn,
Publication 23, p 360 Pcrgjmon Press.
Oxford (1974)
11 U T Department of Agriculture.
"Household F. id Consumption Survey 1965-
1966"
12 Wellman. H N and R T Anger.
"Radioiodme Dosimetry and the Use of
Rddioiodmes Other 1 han "'I in Thyroid
Diagnosis." Si-minart in Nuclear Meriiune.
3356(1971)
13 Killough. C C . D E Dunning. S R
Bernard, and | C Pleasant. "Estimates of
Internal Dose Equivalent to 22 Target Organs
for Radionuclidea Occurring in Routine
Releases from Nuclear Fuel-Cycle Facilities.
Vol 1." ORNL/NUREC/TM-190. Oak Ridge
National Laboratory (June 1978)
14 National Council on Radiation
Protection and Measurements. "Cesium-137
From (he Environment to Man Metabolism
and Dose." NCRP Report No 52. Washington
(January 15.1977).
15 International Commission on
Radiological Protection. Limits for Intakes of
Radionuclides by Workers ICRP Publication
30. Part 1. Annals of the ICRP. Pergamon
Press (1979).
16 Papworth. D G.. and J Vennart.
"Retention of *°Sr in Human Bone at Different
Ages and Resulting Radiation Doses."
Physics in Medicine and Biology. 18169-186
(1973).
17 Kereiakes. J G. P A Feller. F A.
Ascoli. S R Thomas. M ] Celfand. and E L
Saenger. "Pediatric Radiopharmaceutical
Dosimetry" in "Radiopharmoceutical
Dosimetry Symposium." April 26-29.1976.
HEW Publication (FDA) 76-8044 (June 1976)
18 National Academy of Sciences/
National Research Council, 'The Effects on
Populations of Exposure to Low Levels of
Ionizing Radiation." Report of the Advisory
Committee on Biological Effects of Ionizing
Radiation (BEIR-I) (1972).
19 National Council on Radiation
Protection and Measurements (NCRP). "Basic
Radiation Protection Criteria," NCRP Report
No 39, Washington (1971).
20 Bogen. K T. and A. S Goldm.
"Population Exposure to External Natural
Radiation Background in the United Stales.'
ORP/SEPD-60-12. Environmental Protection
Agency. Washington, DC (April 1981).
21 Federal Interagency Task Force on
Offsite Emergency Instrumentation for
Nuclear Accidents. "Guidance on Offsite
Emergency Radiation Measurement Systems:
Phase 2. Monitoring and Measurement of
Radionuclides to Determine Dose
Commitment in the Milk Pathway."
developed by Exxon Nuclear Idaho Co Inc.
Idaho Falls. ID. Draft, July 1981 (to be
published by FEMA).
22 Shleien, B. G D Schmidt, and R P
Chiacchierini. "Background for Protective
Action Recommendations. Accidental
Radioactive Contamination of Food and
Animal Feeds," September 1981. Department
of Health and Human Services. Food and
Drug Administration. Bureau of Radiological
Health. Rockville. MD
Pertinent background data and
information on the recommendations are
on file in the Dockets Management
Branch, and copies are available from
that office (address above).
Based upon review of the comments
received on the proposal of December
15 1978 (43 FR 58790). and FDA's further
consideration of the need to provide
guidance to State and local agencies for
use in emergency response planning in
the event that an incident results in the
radioactive contamination of human
food or animal feed, the agency offers
the following recommendations
regarding protective action planning for
human food and animal feeds:
Accidental Radioactive Contamination
of Human Food and Animal Feeds:
Recommendations for State and Local
Agencies
(a) Applicability. (1) These
recommendations are for use by
appropriate State or local agencies in
response planning and the conduct of
radiation protection activities involving
the production, processing, distribution,
and use of human food and animal feeds
in the event of an incident resulting in
the lease of radioactivity to the
environment. The Food and Drug
Administration (FDA) recommends that
this guidance be used on a case-by-case
basis to determine the need for taking
appropriate protective action in the
event of a diversity of contaminating
events, such as nuclear facility
accidents, transportation accidents, and
fdllout from nuclear devices.
(2) Protective actions are appropriate
when the health benefits associated
with the reduction in exposure to be
achieved are sufficient to offset the
undesirable features of the protective
actions The Protective Action Guides
(PAC's) in paragraph (c) of these
recommendations represent FDA's
judgment as to the level of food
contamination resulting from radiation
incidents at which protective action
should be taken to protect the public
health Further, as provided by Federal
guidance issued by the Federal
Radiation Council, if, in a particular
situation, and effective action with low
total impact is available, initiation of
such action at a projected dose lower
than the PAG may be justifiable. If only
very high-impact action would be
effective, initiation of such action at a
projected dose higher than the PAG may
be justifiable. (See 29 FR 12056; August
22.1964.) A basic assumption in the
development of protective action
guidance is that a condition requiring
protective action IB unusual and should
not be expected to occur frequently.
-------
Federal Register / Vol. 47. No. 205 / Friday. October 22, 1982 / Notices
47081
Circumstances that involve repetitive
occurrence, a substantial probability of
recurrence within a period of 1 or 2
years, or exposure from multiple sources
(such as airborne cloud and food
pathway) would require special
consideration. In such a case, the total
projected dose from the several evenls
and the total impact of the protective
actions that might be taken to avoid the
future dose from one or more of these
events may need to be considered. In
any event, the numerical values selected
for the PAG's are not intended to
authorize deliberate releases expected
to result in absorbed doses of these
magnitudes.
(3) A protective action is an action or
measure taken to avoid most of the
radiation dose that would occur from
future ingestion of foods contaminated
with radioactive materials. These
recommendations are intended for
implementation within hours or days
from the time an emergency is
recognized. The action recommended to
be taken should be continued for a
sufficient lime to avoid most of the
projected dose. Evaluation of when to
cease a protective action should be
made on a case-by-case basis
considering the specific incident and the
food supply contaminated. In the case of
the pasture/cow/milk/person pathway.
for which derived "response levels" are
provided in paragraph (d) of these
recommendations, it is expected that
actions would not need to extend
beyond 1 or 2 months due to the
reduction of forage concentrations by
weathering (14-day half-life assumed].
In the case of fresh produce directly
contaminated by deposition from the
cloud, actions would be necessary at the
time of harvest. This guidance is not
intended to apply to the problems of
long-term food pathway contamination
where adequate time after the incident
is available to evaluate the public health
consequences of food contamination
using current recommendations and the
guidance in Federal Radiation Council
(FRC) Report No. 5, July 1964 and Report
No. 7. May 1965.
(b) Definitions. (1) "Dose" is a general
term denoting the quantity of radiation
or energy absorbed. For special
purposes it must be appropriately
qualified. In these recommendations it
refers specifically to the term "dose
equivalent."
(2) "Dose commitment" means the
radiation dose equivalent received by
an exposed individual to the organ cited
over a lifetime from a single event.
(3] "Dose equivalent" is a quantity
that expresses all radiation on a
common scale for calculating the
effective absorbed dose. It is defined as
the product of the absorbed dose in rads
and certain modifying factors. The unit
of dose equivalent is the rem.
(4) "Projected dose commitment"
means the dose commitment that would
be received in the future by individuals
in the population group from the
contaminating event if no protective
action were taken.
(5) "Protective action" means an
action taken to avoid most of the
exposure to radiation that would occur
from future ingestion of foods
contaminated with radioactive
materials.
(6) "Protective action guide (PAG)"
means the projected dose commitment
values to individuals in the general
population that warrant protective
action following a release of radioactive
material. Protective action would be
warranted if the expected individual
dose reduction is not offset by negative
social, economic, or health effects. The
PAG does not include the dose that has
unavoidably occurred before the
assessment.
(7) "Preventive PAG" is the projected
dose commitment value at which
responsible officials should take
protective actions having minimal ipact
to prevent or reduce the radioactive
contamination of human food or animal
feeds.
(8) "Emergency PAG" is the projected
dose commitment value at which
responsible officials should isolate food
containing radioactivity to prevent its
introduction into commerce and at
which the responsible officials should
determine whether condemnation or
another disposition is appropriate. At
the Emergency PAG. higher impact
actions are justified because of the
projected health hazards.
(9) "Rad" means the unit of absorbed
dose equal to 0.01 Joule per kilogram in
any medium.
(10) "Rem" is a special unit of dose
equivalent. The dose equivalent in rems
is numerically equal to the absorbed
dose in rads multiplied by the quality
factor, the distribution factor, and any
other necessary modifying factors.
(11) "Response level" means the
activity of a specific radionuclide (i)
initially deposited on pasture; or (ii) per
unit weight or volume of food or animal
feed; or (iii) in the total dietary intake
which corresponds to a particular PAG.
(c) Protective action guides fPAC'sJ.
To permit flexibility of action for the
reduction of radiation exposure to the
public via the food pathway due to the
occurrence of a contaminating event, the
following Preventive and Emergency
PAG's for an exposed individual in the
population are adopted:
[I] Preventive PAG which is (i) 1.5
rem projected dose commitment to the
thyroid, or (ii) 0.5 rem projected dose
commitment to the whole body, bone
marrow, or any other organ.
(2) Emergency PAG which is (i) 15 rem
projected dose commitment to the
thyroid, or (ii) 5 rem projected dose
commitment to the whole body, bone
marrow, or any other organ.
(d) Response levels equivalent to
PAG. Although the basic PAG
recommendations are given in terms of
projected dose equivalent, it is often
more convenient to utilize specific
radionuclide concentrations upon which
to initiate protective action. Denved
response levels equivalent to the PAG's
for radionuchdes of interest are:
(1) Response level for Preventive
PAG. Infant' as critical segment of
population.
'Newborn infant Includes fetus (pregnant
women) a§ critical icgment of population for lodine-
131 For other radionuchdcs. "infant" refers to child
leas than 1 year of age
Response levels tor preventive PAG
Irttal Activity Area Deposition (rnioracunes/square mam) . - ........ . ..
Forage Concentration • (rmorocunea/kitogrim) . . -.--..
Put MA Activity (meraeunas/Har) .... .....
Total intake1 (merocunes) . . . . . . .....
131,"
013
005
0015
009
134n«
2
08
01S
4
137o/
3
13
024
7
80%
05
016
0009
02
89*
8
3
014
2.6
'From Mom. torJne-131 it me only nojoadme of significance with respect to milk contamination beyond the tost day In case of a reactor accident, me cumulative intake of iorjme-133 via
mlk is about 2 percent ol iodne-131 assumng equivalent deposition.
'Fresh mghl
•Intake ol oasum we the meet/person padiway (or adults mrty eioeed that ol the rralk pathway: therefore, suet) levels in mlk should cause surveillance and protective actions lor meat as
appropriate If both oa*un>l34 and cesvm-137 ate equally present as rmghl be mpecled lor reactor accidents, the response levels should be reduced by a lector ol two
-------
47082 Federal Register / Vol. 47, No. 205 / Friday. October 22. 1982 / Notices
(2] Response level for Emergency PAG. The response levels equivalent to the Emergency PAG are presented fur both
infants and adults to permit use of either level and thus assure a flexible approach to taking action in cases where exposure
of the most critical portion of the population (infants and pregnant women) can be prevented:
Response levels lor emergency PAG
Initial Activity Area Deposition (mcrocunes/square meter)
Forage Concentration • Imcrocurtes/kilograrn)
Peak Mdk Activity (mcrocunea/Mer)
Total intake (mooounea)
13V
Infant' '\ Adull
13 16
OS 1 7
015 I 2
09 10
134C.'
Intern'
ZO
a
IS
40
Adult
40
17
3
70
•^n?
»
Adult
30 SO
13
24
70
19
4
80
90,
rntarrl'
5
ia
009
2
Adult
20
e
04
7
a*.
Infant'
ao
30
14
26
ArM
IBM
700
30
400
•Newborn intent nekioes Mus (pregnant women) as cntieil segment of pepulatnn tor ndme-131
'"Infant" mien to cMd less than 1 year of age
'Rom fallout. oAna-131 • ine only radundine ol signihcince with respect to nrik conliimnauon beyond the Im day In ease ol a reactor accident the cumulative mlake ol oome-133 vii
mlk n about 2 percent ol iodne-131 assuming equrvalenl deposition
•Fresh wagrn.
•Make ol cesun «e the meat/person pathway lor adults may eiceed mat ol me mdk pathway rhoretoie such levels n milk should cause surveillance and protective arsons lor meat as
aperopfiaia. H both eesum 134 and eesum-137 an equally present, as might be enpected tor reactor acoeena the response levels should be reduced by a lacier ol 2
(e) Implementation. When using the
PAC's and associated response levels
for response planning or protective
actions, the following conditions should
be followed:
(1} Specific food items. To obtain the
response level (microcurie/kilogram)
equivalent to the PAG for other specific
foods, it is necessary to weigh the
contribution of the individual food to the
total dietary intake; thus.
Rpsrmnw. Level - Total intake (microcunes)
Response Level - eonsumpt,on (1.'
Where: Total intake (microcunes) for the
appropriate PAG end radionuclide n
given in paragraph (d) of these
recommends tioni
and
Consumption is the product of the average
daily consumption specified in paragraph
(<*)(1)(>) of these recommendations and
the days of intake of the contaminated
food as specified in paragraph (e)(1)(u) of
these recommendations.
(i) The daily consumption of specific
foods in kilograms per day for the
general population is given in the
following table:
Food
Flour, canal .... . -
Bakery products __ - — _— -
Meet _ _ _
Poultry
Cish and shetHsn. .
Eggs . . _.
Sugar, arupe. honey, molasses. Me .
VorjstabkM, fioeh (artrsmano potatoes)
Vegetables, earned, trcaen. dried
Vegetables, sjoe 'angle strength)... .
FnA fresh. -_.___
Frutl canned, frozen, dried . .
FruH, |uce (angle strength)
Average
con-
sumption
for ins
tioo
(•*>
day)
570
OSS
091
ISO
220
OSS
023
055
073
105
145
jon
008
165
035
04S
Food
Other beverages (soft drinks cottee. alcoholic)
Soup and gravies (mostly condensed) .
Nuls and peanut butter
Total
Average
con-
sumption
for the
general
non
(kilo-
gram/
day)
180
036
009
2099
'Eiprassad as cataum equivalent, thai ox the quantity ot
•Kola llud mtk to when dairy products are equivalent si
calcium content.
(ii) Assessment of the effective days
of intake should consider the specific
food, the population involved, the food
distribution system, and the
radionuclide. Whether the food is
distributed to the retail market or
produced for home use will significantly
affect the intake in most instances.
Thus, while assessment of intake should
be on a case-by-case basis, some
general comments may be useful in
specific circumstances.
(a) For short half-life rudionuclides.
radioactive decay will limit the
ingestion of radioactive materials and
the effective "days of intake". The
effective "days of intake" in this case is
1.44 times the radiological half-life. For
iodine-131 (half-life—8 05 days), the
effective "days of intake" is, thus, 11
days.
(b) Where the food product is being
harvested on a daily basis, it may be
reasonable to assume reduction of
contamination due to weathering. As an
initial assessment, it may be appropriate
to assume a 14-day weathering half-life
(used for forage in pasture/cow/milk
pathway) pending further evaluation. In
this case, the effective "days of intake"
is 20 days. A combination of radioactive
decay and weathering would result in
an effective half-life for iodine-131 of 5
days and reduce the "days of intake" to
7 days.
(c) In the case of a food which is sold
in the retail market, the effective "days
of intake" would probably be limited by
the quantity purchased at a given time.
For most food, especially fresh produce.
this would probably be about a 1 week
supply. In some cases, however, larger
quantities would be purchased for home
canning or freezing. For most foods and
members of the public, an effective
"days of intake" 30 days is probably
conservative.
(ni) For population groups having
significantly different dietary intakes, an
appropriate adjustment of dietary
factors should be made.
(2) Radionuclide mixtures. If a
mixture of radionuchdes is present, the
sum of all the ratios of the concentration
of each specific radionulide to its
specific response level equivalent to the
PAG should be less than one.
(3) Other radionuclides. The response
level for the Preventive and Emergency
PAG for other radionuclides should be
calculated from dose commitment
factors available in the literature
(Killough. G. G, et al., ORNL/NUREG/
-TM-190 (1078) [adult only), and U.S.
Nuclear Regulatory Commission Reg.
Guide 1.109 (1077)).
(4) Other critical organs. Dose
commitment factors in U.S. Nuclear
Regulatory Commission Reg. Guide 1.169
(1977) refer to bone rather than bone
marrow dose commitments. For the
purpose of these recommendations, dose
commitment to the bone marrow is
considered to be 0.3 of the bone dose
commitment. This is based on the ratio
of dose rate per unit activity in the bone
marrow to dose rale per unit activity in
a small tissue-filled cavity in bone and
assumes that strontium-90 is distributed
only in the mineral bone (Spiers. F. W.,
et al.. in "Biomedical Implications of
Radiostrontium Exposure," AEC
Symposium 25 (1972). The ratio for
strontium-69 is the same because the
mean particle energies are similar (0.56
MeV (megaelectronvolts)). Situations
could arise in which an organ other than
those discussed in this paragraph could
-------
Federal Register / Vol. 47. No. 205 / Friday. October 22. 1982 / Notices
47083
be considered to be the organ receiving
the highest dose per unit intake. In the
case of exposure via the food chain.
depending on the radionuclide under
consideration, the gastrointestinal tract
could be the primary organ exposed.
The references cited in paragraph (e)(3)
of these recommendations contain dose
commitment factors for the following
organs: bone, kidneys, liver, ovaries.
spleen, whole body, and gastrointestinal
tract.
(5) Prompt notification of State and
local agencies regarding the occurrence
of an incident having potential public
health consequences is of significant
value in the implementation of effective
protective actions. Such notification is
particularly important for protective
actions to prevent exposures from the
airborne cloud but is also of value for
food pathway contamination.
Accordingly, this protective action
guidance should be incorporated in
State/local emergency plans which
provide for coordination with nuclear
facility operators including prompt
notification of accidents and technical
communication regarding public health
consequences and protective action.
(f) Sampling parameter. Generally.
sites for sample collection should be the
retail market, the processing plant and
the farm. Sample collection at the milk
processing plant may be more effcient in
determining the extent of the food
pathway contamination. The geographic
area where protective actions are
implemented should be based on
considerations of the wind direction and
atmospheric transport, measurements by
airborne and ground survey teams of the
radioactive cloud and surface
deposition, and measurements in the
food pathway.
(g) Recommended methods of
analysis. Techniques for measurement
of radionuclide concentrations should
have detection limits equal to or less
than the response levels equivalent to
specific PAG. Some useful methods of
radionuclide analysis can be found in:
(1) Laboratory Methods—"HASL
Procedure Manual." edited by John H.
Harley. HASL 300 ERDA. Health and
Safety Laboratory, New York. NY. 1973:
"Rapid Methods for Estimating Fission
Product Concentrations in Milk." U.S.
Department of Health. Education, and
Welfare. Public Health Service
Publication No. 999-R-2. May 1963;
"Evaluation of Ion Exchange Cartridges
for Field Sampling of lodine-131 in
Milk." Johnson. R. H. and T. C. Reavy.
Nature. 208. (5012): 750-752. November
20.1965; and
(2) Field Methods—Kearny. C. H..
ORNL 4900, November 1973; Distenfeld,
C. and J. Klemish. Brookhaven National
Laboratory. NUREG/CR-0315.
December 1978; and International
Atomic Energy Agency, "Environmental
Monitoring in Emergency Situations."
1966. Analysis need not be limited to
these methodologies but should provide
comparable results. Action should not
be taken without verification of the
analysis. Such verification might include
the analysis of duplicate samples.
laboratory measurements, sample
analysis by other agencies, sample
analysis of various environmental
media, and descriptive data on
radioactive release.
(h) Protective actions. Actions are
appropriate when the health benefit
associated with the reduction in dose
that can be achieved is considered to
offset the undesirable health, economic.
and social factors. It is the intent of
these recommendations that, not only
the protective actions cited for the
Emergency PAG be initiated when the
equivalent response levels are reached,
but also that actions appropriate at the
Preventive PAG be considered. This has
the effect of reducing the period of time
required dunng which the protective
action with the greater economic and
social impact needs to be taken. FDA
recommends that once one or more
protective actions are initiated, the
action or actions continue for a
sufficient time to avoid most of the
projected dose. There is a longstanding
FDA policy that the purposeful blending
of adulterated food with unadulterated
food is a violation of the Federal Food.
Drug, and Cosmetic Act. The following
protective actions should be considered
for implementation when the projected
dose equals or exceeds the appropriate
PAG:
(1) Preventive PAG. (i) For pasture: (a)
Removal of lactating dairy cows from
contaminated pasturage and
substitution of uncontaminated stored
feed.
(£>) Substitute source of
uncontaminated water.
(ii) For milk: (a) Withholding of
contaminated milk from the market to
allow radioactive decay of short-lived
radionuclides. This may be achieved by
storage of frozen fresh milk, frozen
concentrated milk, or frozen
concentrated milk products.
(b) Storage for prolonged times at
reduced temperatures also is feasible
provided ultrahigh temperature
pasteurization techniques are employed
for processing (Finley. R. D.. H. B.
Warren, and R. E. Hargrove. "Storage
Stability of Commercial Milk." Journal
of Milk and Food Technology.
3l(12):382-387. December 1968).
(c) Diversion of fluid milk for
production of dry whole milk, nonfat dry
milk, butter, cheese, or evaporated milk.
[iii] For fruits and vegetables: (a)
Washing, brushing, scrubbing, or peeling
to remove surface contamination.
[b) Preservation by canning, freezing,
and dehydration or storage to permit
radioactive decay of short-lived
radionuclides.
(iv) For grains: (a Milling and (6)
polishing.
(v) For other food products, processing
to remove surface contamination.
(vi) For meat and meat products,
intake of cesium-134 and cesium-137 by
an adult via the meat pathway may
exceed that of the milk pathway;
therefore, levels of cesium in milk
approaching the "response level" should
cause surveillance and protective
actions for meat as appropriate.
(vii) For animal feeds other than
pasture, action should be on a case-by-
case basis taking into consideration the
relationship between the radionuclide
concentration in the animal feed and the
concentration of the radionuclide in
human food. For hay and silage fed to
lactating cows, the concentration should
not exceed that equivalent to the
recommendations for pasture.
(2) Emergency PAG. Responsible
officials should isolate food containing
radioactivity to prevent its introduction
into commerce and determine whether
condemnation or another disposition is
appropriate. Before taking this action,
the following factors should be
considered:
(i) The availability of other possible
protective actions discussed in
paragraph (h)(l) of these
recommendations.
(ii) Relative proportion of the total
diet by weight represented by the item
in question.
(iii) The importance of the particular
food in nutrition and the availability of
uncontaminated food or substitutes
having the same nutntional properties.
(iv) The relative contribution of other
foods and other radionuclides to the
total projected dose.
(v) The time and effort required to
effect corrective action.
This notice is issued under the Public
Health Service Act (sees. 301.310.311.
58 Stat. 691-693 as amended. 88 Slat. 371
(42 U.S.C. 241,242o. 243]) and under
authority delegated to the Commissioner
of Food and Drugs (21CFR 5.10).
Dated. October 11.1982.
Arthur Hull Hayes. Jr.,
Commissioner of Food and Drugs
|FR Doe B2-2B5U Filed 10-21-82 845am|
BILLING CODE 4160-01-H
-------
Draft
CHAPTER 4
Protective Action Guides for the Intermediate Phase
(Deposited Radioactive Materials)
4.1 Introduction
Following a nuclear incident it may be necessary to temporarily
relocate the public from areas where extensive deposition of radioactive
materials has occurred until decontamination has taken place. This chapter
identifies the levels of radiation exposure which indicate when relocation
from contaminated property is warranted.
The period addressed by this chapter is denoted the "intermediate
phase." This is arbitrarily defined as the period beginning after the
source and releases have been brought under control and environmental
measurements are available for use as a basis for decisions on protective
actions and extending until these protective actions are terminated. This
phase may overlap the early and late phases and may last from weeks to many
months. For the purpose of dose projection, it is assumed to last for one
year. Prior to this period protective actions will nave been taken based
upon the PAGs for the early phase. It is assumed that decisions will be
made during the intermediate phase concerning whether particular areas or
properties from which persons have been relocated will be decontaminated and
reoccupied, or condemned and the occupants permanently relocated. These
actions will be carried out during the late or "recovery" phase.
Although these Protective Action Guides (PAGs) were developed based on
expected releases of radioactive materials characteristic of reactor
incidents, they may be applied to any type of incident that can result in
long-term exposure of the public to deposited radioactivity.
4-1
-------
PAGs are expressed in terms of the projected doses above which specified
protective actions are warranted. In the case of deposited radioactivity, the
major relevant protective action is relocation. Persons not relocated (i.e.,
those in less contaminated areas) may reduce their dose through the applica-
tion of simple decontamination techniques and by spending more time than usual
in low exposure rate areas (e.g., indoors).
The PAGs should be considered mandatory only for use in planning, e.g.,
in developing radiological emergency response plans. During an incident,
because of unanticipated local conditions and constraints, professional
judgment by responsible officials will be required in their application.
Situations can be envisaged, where contamination from a nuclear incident
occurs at a site or time in which relocation of the public, based on the
recommended PAGs, would be impracticable. Conversely, under some conditions,
relocation may be quite practicable at projected doses below the PAGs. These
situations require judgments by those responsible for protective action
decisions at the time of the incident. A discussion of the implementation of
these PAGs is provided in Chapter 7.
The PAGs for relocation specified in this chapter refer only to estimates
of doses due to exposure during the first year after the incident. Exposure
pathways include external exposure to radiation from deposited radioactivity
and inhalation of resuspended radioactive materials. Protective Action Guides
for ingestion exposure pathways, which also apply during the intermediate
phase, are discussed separately in Chapter 3.
Individuals who live in areas contaminated by long-lived radionuclides
may be exposed to radiation from these materials, at a decreasing rate, over
the entire time that they live in the area. This would be the case for those
who are not relocated as well as for persons who return following relocation.
Because it is usually not practicable, at the time of a decision to relocate,
to calculate the doses that might be incurred from exposure beyond one year,
and because different protective actions may be appropriate over such longer
periods of time, these doses are not included in the dose specified in the
PAGs for relocation.
4-2
-------
4.1.1 Exposure Pathways
The principal pathways for exposure of the public occupying locations
contaminated by deposited radioactivity are expected to be exposure of the
whole body to external gamma radiation from deposited radioactive materials
(groundshine) and internal exposure from the inhalation of resuspended
materials. For reactor incidents, external gamma radiation is expected to be
the dominant source.
Almost invariably relocation decisions will be based on doses from the
above pathways. (However, in rare cases where food or drinking water is
contaminated to levels above the PAG for ingestion, and its withdrawal from
use will create a risk from starvation greater than that from the radiation
dose, the dose from ingestion should be added to the dose from the above
pathways.) PAGs related specifically to the withdrawal of contaminated food
and water from use are discussed in Chapter 3.
Other potentially significant exposure pathways include exposure to beta
radiation from surface contamination and direct ingestion of contaminated
soil. These pathways are not expected to be controlling for reactor incidents
(AR-89).
4.1.2 The Population Affected
The PAGs for relocation are intended for use in establishing the boundary
of a restricted zone within an area that has been subjected to deposition of
radioactive materials. During their development, consideration was given to
the higher risk of effects on health to children and fetuses from radiation
dose and the higher risk to some other population groups from relocation. To
avoid the complexity of implementing separate PAGs for individual members of
the population, the relocation PAG is established at a level that will provide
adequate protection for the general population.
Persons residing in contaminated areas outside the restricted zone will
be at some risk from radiation dose. Therefore, guidance on the reduction of
4-3
-------
dose during the first year to residents outside this zone is also provided.
Due to the high cost of relocation, it is more practical to reduce dose in
this population group by the early application of simple, low-impact,
protective actions other than by relocation.
4.2 The Protective Action Guides for Deposited Radioactivity
PAGs for protection from deposited radioactivity during the
intermediate phase are summarized in Table 4-1. The basis for these values
is presented in detail in Appendix E. In summary, relocation is warranted
when the projected sum of the dose equivalent from external gamma radiation
and the committed effective dose equivalent from inhalation of resuspended
radionuclides exceeds 2 rem in the first year. Relocation to avoid exposure
of the skin to beta radiation is warranted at 50 times the numerical value
of the relocation PAG for effective dose equivalent.
Persons who are not relocated, i.e., those in areas that receive
relatively small amounts of deposited radioactive material, should reduce
their exposure by the application of other measures. Possible dose
reduction techniques range from the simple processes of scrubbing and/or
flushing surfaces, soaking or plowing of soil, removal and disposal of small
spots of soil found to be highly contaminated (e.g., from settlement of
water), and spending more time than usual in lower exposure rate areas
(e.g., indoors), to the difficult and time-consuming processes of removal,
disposal, and replacement of contaminated surfaces. It is anticipated that
simple processes will be most appropriate for early application. Many can
be carried out by residents themselves with support from response officials
for assessment of the levels of contamination, guidance on appropriate
actions, and disposal of contaminated materials. Due to the relatively low
cost and risk associated with these protective actions, they may be
justified as ALARA measures at low dose levels. It is, however, recommended
that response officials concentrate their initial efforts in areas where the
projected dose from the first year of exposure exceeds 0.5 rem. In
addition, first priority should be given to cleanup of residences of
pregnant women who may exceed this criterion.
4-4
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Table 4-1 Protective Action Guides for Exposure to Deposited Radioactivity
During the Intermediate Phase of a Nuclear Incident
Protective
Action
PAG (projected
dose)3
Comments
Relocate the general >2 rem Beta dose to skin may be up to
population.& 50 times higher.
Apply simple dose <2 rem These protective actions
reduction techniques.0 should be taken to reduce doses
to as low as practicable levels.
a The projected sum of effective dose equivalent from external gamma
radiation and committed effective dose equivalent from inhalation of
resuspended materials, from exposure or intake during the first
year. Projected dose refers to the dose that would be received in
the absence of shielding from structures or the application of dose
reduction techniques. These PAGs may not provide adequate protection
from some long-lived radionuclides (see Section 4.2.1).
b Persons previously evacuated from areas outside the relocation zone
defined by this PAG may return to occupy their residences. Cases
involving relocation of persons at high risk from such action (e.g.,
patients under intensive care) should be evaluated individually.
c Simple dose reduction techniques include scrubbing and/or flushing
hard surfaces, soaking or plowing soil, minor removal of soil from
spots where radioactive materials have concentrated, and spending
more time than usual indoors or in other low exposure rate areas.
4.2.1 Longer Term Objectives of the Protective Action Guides
It is an objective of these PAGs to assure that 1) doses in any single
year after the first will not exceed 0.5 rem, and 2) the cumulative dose
over 50 years (including the first and second years) will not exceed 5 rem.
For source terms from reactor incidents, the above PAG of 2 rem projected
dose in the first year is expected to meet both of those objectives through
4-5
-------
radioactive decay, weathering, and normal part time occupancy in structures.
Decontamination of areas outside the restricted area may be required during
the first year to meet these objectives for releases consisting primarily of
long-lived radionuclides. For situations where it is impractical to meet
these objectives though decontamination, consideration should be given to
relocation at a lower projected first year dose than that specified by the
relocation PAG.
After the population has been protected in accordance with the PAGs for
relocation, return for occupancy of previously restricted areas should be
governed on the basis of Recovery Criteria as presented in Chapter 8.
Projected dose considers exposure rate reduction from radioactive decay
and, generally, weathering. When one also considers the anticipated effects
of shielding from partial occupancy in homes and other structures, persons
who are not relocated should receive a dose substantially less than the
projected dose. For commonly assumed reactor source terms, we estimate that
2 rem projected dose in the first year will be reduced to about 1.2 rem by
this factor. The application of simple decontamination techniques shortly
after the incident can be assumed to provide a further 30 percent or more
reduction, so that the maximum first year dose to persons who are not
relocated is expected to be less than one rem. Taking account of decay
rates assumed to be associated with releases from nuclear power plant
incidents (SN-82) and shielding from partial occupancy and weathering, a
projected dose of 2 rem in the first year is likely to amount to an actual
dose of 0.5 rem or less in the second year and 5 rem or less in 50 years.
The application of simple dose reduction techniques would reduce these doses
further. Results of calculations supporting these projections are
summarized in Table E-6 of Appendix E.
4.2.2 Applying the Protective Action Guides for Relocation
Establishing the boundary of a restricted zone may result in three
different types of actions:
4-6
-------
I. Persons who, based on the PAGs for the early phase of a nuclear
incident (Chapter 2), have already been evacuated from an area which
is now designated as a restricted zone must be converted to
relocation status.
2. Persons not previously evacuated who reside inside the restricted
zone should relocate.
3. Persons who normally reside outside the restricted zone, but were
previously evacuated, may return. A gradual return is recommended,
as discussed in Chapter 7.
Small adjustments to the boundary of the restricted zone from that
given by the PAG may be justified on the basis of difficulty or ease of
implementation. For example, the use of a convenient natural boundary could
be cause for adjustment of the restricted zone. However, such decisions
should be supported by demonstration that exposure rates to persons not
relocated can be promptly reduced by methods other than relocation to meet
the PAG, as well as the longer term dose objectives addressed in Section
4.2.1.
Reactor incidents involving releases of major portions of the core
inventory under adverse atmospheric conditions can be postulated for which
large areas would have to be restricted under these PAGs. As the affected
land area increases, they will become more difficult and costly to
implement, especially in densely populated areas. For situations where
implementation becomes impracticable or impossible (e.g., a large city),
informed judgment must be exercised to assure priority of protection for
individuals in areas having the highest exposure rates. In such situations,
the first priority for any area should be to reduce dose to pregnant women.
4.3 Exposure Limits for Persons Reentering the Restricted Zone
Individuals who are permitted to reenter a restricted zone to work, or
for other justified reasons, will require protection from radiation. Such
4-7
-------
individuals should enter the restricted zone under controlled conditions in
accordance with dose limitations and other procedures for control of
occupationally-exposed workers (EP-87). Ongoing doses received by these
individuals from living in a contaminated area outside the restricted zone
need not be included as part of this dose limitation applicable to workers.
In addition, dose received previously from the plume and associated
groundshine, during the early phase of the nuclear incident, need not be
considered.
References
AR-89 AABERG, ROSANNE, Battelle Northwest Laboratories. Evaluation of
Skin and Ingestion Exposure Pathways. U.S. Environmental Protection
Agency/Office of Radiation Programs, Washington, D.C. 20460 (1988
Draft).
EP-87 U.S. ENVIRONMENTAL PROTECTION AGENCY. Radiation Protection
Guidance to Federal Agencies for Occupational Exposure. Federal
Register. Vol. 52, No. 17, Page 2822, U.S. Government Printing
Office, Washington, DC 20402, January 1987.
SN-82 SANDIA NATIONAL LABORATORY. Technical Guidance for Siting Criteria
Development. NUREG/CR-2239. U.S. Nuclear Regulatory Commission,
Washington, DC 20555, 1982.
4-8
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CHAPTER 5
Implementing the Protective Action Guides
for the Early Phase*
(Application of Protective Action Guides
for Exposure to Airborne Radioactive Materials
from an Accident at a Nuclear Power Facility)
5.0 Introduction
This chapter deals with methods for estimating population dose
from plume exposure baaed on release rates and meteorological
conditions or based on offsite radiological measurements. It also
provides guidance for comparison of projected dose with PAGs for
decisions on protective actions. These dose projection methods are
recommended for use by State and local officials for development of
operational plans for responding to incidents at nuclear power
facilities.
Following a radiological incident involving an atmospheric
release that may require protection of the public, State authorities
will need information to make decisions on what protective actions
to implement and where they should be implemented. The information
needed includes (1) Protective Action Guides adjusted for local
situations and (2) projected doses in specific areas for comparison
to the Guides. Protective Action Guides were provided in
Chapter 2. Projected doses must be determined on the basis of data
available following the incident. These data may come from
(1) plant conditions, (2) release rates and meteorological
conditions, or (3) offsite radiological measurements, or
combinations thereof.
This Chapter appears here in the form it was published in 1980;
a revised version is currently under review.
Revised 6/79
5.1
-------
The methods presented in tola Chapter for relating data at the
time of the incident to projected dose are recommended for use in
development of operational response plans for atmospheric releases
at nuclear power facilities.
Planners are encouraged to improve on the methods where
possible and to alter them as necessary to respond to special
circumstances. State planners should specifically consider the use
of any improved dose projection methods developed by the nuclear
facility operator.
5.1 Release Assumptions
The guidance in this Chapter is directly related to releases to
the atmosphere that have been postulated for nuclear power
facilities. WASH-1UOO m indicates that should there be an
accident at a nuclear power station, there is an extremely wide
spectrum of different kinds of possible releases to the atmosphere
and different time frames for releases depending on the severity and
the exact sequence of the failure modes.
A nuclear power reactor may suffer a loss of coolant but
without a meltdown of the reactor core. For this class of accident,
the release to the atmosphere should be mostly radioactive noble
gases and iodines. Accidents of increasingly larger environmental
impact would occur in association with a meltdown of the reactor
core and eventual loss of containment integrity. This class of
Revised 6/79
5.2
-------
accident could release quantities of radioactive participate
material aa well as the radioactive noble gases and iodines.
However, for planning purposes, it La reoonmended that radioiodines
be assumed to represent the principal contributor to inhalation
dose, and for situations where whole body dose from the plume would
be the controlling exposure pathway, it should be assumed that noble
gases would be the principal contributors.
Guidance on time frames for releases cannot be very specific
because of the wide range of time frames that could be associated
with the potential spectrum of accidents that could occur.
Therefore, it will be necessary for planners to consider the
possible different tlae periods between the initiating event and
arrival of the plume and possible tine periods of releases in
relationship to time needed to implement protective actions. The
Reactor Safety Study indicates, for example, that major releases may
begin in the range of one-half hour to as ouch as 30 hours after an
initiating event and that the duration of the releases may range
from one-half hour to several days with the major portion of the
release occurring within the first day. In addition, significant
plume travel times are associated with the moat adverse
meteorological conditions that might result in Large potential
exposures far from the site. For example, under poor dispersion
conditions associated with low windspeeds, two hours or more might
Revised 6/79
5.3
-------
be required for the plume to travel a distance of five nilea.
Higher wlndspeeds would result in shorter travel times but would
provide more dispersion, Baking high exposures at long distances
much less likely. Additional Information on tloe frames for
releases may be found in Reference (T).
5.1.1 Radioactive Noble Gas and Radioiodine Releases
For an atmospheric release at a nuclear power facility that
involved only noble gases and radioiodines, it would usually be
conservative to assume that 100 percent of the equilibrium noble gas
inventory and 25 percent of the equilibrium radioiodine inventory
would be available for release from containment. In the absence of
more accurate information from the facility operator regarding the
release composition, it should be assumed that this composition is
released to the environment. The relative abundance of radioiodines
and noble gases in an actual release from containment would be a
function of the effectiveness of engineered safeguards (e.g.,
filters, spray systems, and scrubbing systems) in removing each
component.
1Thla assumption is in agreement with NRC guidance (2,5,6) on
assumptions that may be used in evaluating the radiological ~
consequences of a loss of coolant accident at a light water cooled
nuclear power facility.
Revised 6/79
5.4
-------
Table 3.1 of Appendix D summarizes the total quantities of
radiologies11y significant gaseous radionuclides that would be in
inventory under equilibrium conditions for a 1000 Mie plant.
Calculations of the projected population dose based on a release
mixture consisting of 1001 of the noble gases and 25% of the
radioiodines indicate that the thyroid dose from inhalation of
radioiodine ranges up to UOO times greater than the whole body gamma
dose from noble gaaea and radioiodines. However, if the engineered
safeguards function as designed, they should reduce the iodine
concentration such that the whole body gamma radiation exposure from
noble gases would be the controlling pathway.
5.1.2 Radioactive Particulate Material Releases
Except for the most severe and improbable accidents postulated
by VA5H-1400, protective actions (prophylaxis iodine excepted)
chosen on the basis of assuming the iodine exposure pathway is
critical (figure 5.2) should be sufficient to provide protection
from radioactive particular material. This partlculate material
will deliver an additional dose to the lung and to the whole body
from material located in the lung. However, it is not anticipated
that lung exposure would represent the controlling exposure pathway
for accidents at nuclear power facilities.
5.2 Sequence of Events
Following an incident at a nuclear power facility involving a
release to the atmoaphere, the most urgent protective actions in
terms of response time will be those needed to protect the
Revised 6/79
5.5
-------
population from inhalation of radioactive materials in the plume and
from direct whole body exposure to gaooa radiation from the plume.
The time of exposure to the plume can be divided into two periods;
(1) the period immediately following the incident when little or no
environmental data are available to confirm the seriousness of
population exposures, and (2) a period when environmental levels
and/or concentrations are known. During the first period, speed for
completing such actions as evacuation, seeking shelter, and access
control may be critical to minimize exposure in areas where PAGs are
postulated to be exceeded. Furthermore, environmental measurements
made during this period may have little meaning because of
uncertainty concerning plume location when measurements were made or
uncertainty concerning changes in release rate due to changes in
pressure and radionuclide concentrations within containment.
Therefore, it would generally be advisable to initiate early
predetermined protective actions on the basis of dose projections
provided by the facility operator. During the second period when
environmental levels are known, these actions can be adjusted as
appropriate.
For accidents involving a release to the atmosphere at a
nuclear power facility, the following sequence of events is
suggested to minimize population exposure.
Revised 6/79
5.6
-------
(1) Notification by the facility operators that an incident
has occurred with potential to cause offsita projected
doses that exceed the PAGa. This notification should be
provided as soon as possible following the incident and
prior to the release if possible.
(2) Immediate evacuation or shelter of populations in
pradesignated areas without waiting for confirming release
rate measurements or environmental radiation measurements.
(3) Monitor gamna exposure rates (and iodine concentrations if
possible) in the environment. The facility operator
should monitor release rates and plant conditions.
(1) Calculate plume centerline exposure rate at various
distances downwind from the release point, or use prepared
isopleths to estimate exposure rates in downwind areas.
(5) Use exposure rates, airborne concentrations, and estimated
exposure duration to convert to projected dose.
(6) Compare projected dose to PAGa and adjust areas for
protective actions as Indicated.
(7) Continue to make adjustments as more data become available.
5.2.1 Accident Notification
The first Indication that a nuclear accident has occurred
should come to State authorities from the facility operator. The
notification from a nuclear power facility to the State and local
Revised 6/79
5.7
-------
response organizations should include an estimate of the projected
dose to the population at the site boundary and at oore distant
locations along with estimated time frames. The State emergency
response planners should make arrangements with the facility
operator to assure this information will be made available on a
timely basis (within 1/2 hour or less following the incident and
prior to the start of the release) and that it will be provided in
units that can be compared to PAGs (i.e., projected dose in rem to
the whole body or thyroid).
5.2.2 Immediate Actions
The Planning Basis (T) recommends that States designate an
Emergency Planning Zone (EPZ) for protective actions for plume
exposure out to about 10 miles from a nuclear power facility.
Within this distance it may also be practical to plan an area for
immediate response prior to the availability of information for
making dose projections. This could be a circular area described by
a designated radial distance from the facility. Actions would be
taken •within approximately a 90 degree sector downwind out to the
designated distance based on notification from the facility operator
that plant conditions exist which present a potential for offsite
doses in excess of the PAGs. The remaining area out to the EPZ
would be placed on alert pending more information. When additional
information or forecasts on wind direction and meteorology became
available, decisions could be made on additional areas for
Revised 6/79
5.8
-------
protective actions. With good meteorological and wind direction
information, it might be possible to reduce the width of the sector
for protective actions. However, if wind direction is variable or
if the start of the release Is delayed, or if the release duration
is long, the width of the sector may increase or possibly extend to
a complete circle. The importance of good information and forecasts
on wind direction cannot be overemphasized.
The designated distance for immediate actions would be used
only in situations where the facility operator could not estimate
offsite projected doses. If the facility operator provides
projections of population dose, then these should be used by the
State to determine the downwind distance for immediate action in
lieu of the predesignated distance. The outer edge of the low
population zone is a suggested radial distance for immediate actions
in the absence of reasons for other distances.
5.3 Establishment of Exposure Rate Patterns
During or following initial actions to protect the close-in
population, environmental exposure rate measurements should be made
to provide a data base for projecting dose and for Devaluating the
need for additional protective actions or termination of those
actions already taken. Planning guidance for the collection of
these data is provided in Appendix A. (Note: Appendix A is still
under development. Reference (£) will form the basis for Appendix A
and is recommended as an alternate source of information.)
Revised 6/79
5.9
-------
After obtaining exposure rates or concentrations at selected
locations in the environment, these must be translated to additional
locations to identify the pattern of the exposed area. Exposure
rate patterns based on a few downwind measurements can be estimated
in a variety of ways. One simple way is to measure plume centerline
exposure rate at ground level at some known distance from the
release point and use these data to calculate exposure rates at
other designated distances downwind by assuming that the cloud
centerline exposure rate is inversely proportional to the distance
from the release point.
The following relationship can be used for this calculation:
-.ft!
Where: D = exposure rate measured at distance R.
D. = exposure rate at distance R.
x : rate of diffusion as a function of distance.
This relationship can be used to develop a crude pattern of
estimated exposure rates by assuming that x = 1.5 and that the
2The centerline exposure rate can be determined by traversing
the plume at a point sufficiently far downwind (usually greater than
one mile from the site) while taking continuous exposure rate
measurements. The highest reading should be at the center line of
the plume.
Revised 6/79
5.10
-------
exposure rate calculated for the plume centerline would also exist
at points equidistant from the source in the general downwind
direction. To use this method, one must be sure that the
exposure rate measurement is taken at or near the plume centerline.
A second and easier method for estimating exposure rate
patterns is to use a series of prepared exposure rate isopleths
(maps with lines connecting points of equal exposure rates) plotted
on transparencies. These isopleth plots are frequently available
from the licensee, thus eliminating the need for the State to
develop them. Since both the meteorological stability class and the
windspeed existing at the time of the release affect the shape of
the exposure rate isopleth curves, several sets of curves would be
needed to represent the variety of stability conditions and
windspeeds likely to exist at that site. The appropriate
transparency can be selected on the basis of windspeed and
meteorological conditions at the time of the incident. The
transparency can then be placed over a map of the area that has the
same scale as the isopleth curves sucn that the curves are properly
oriented with regard to wind direction. The isopleth curves are
3The value of 1.5 for x is for average meteorological
conditions. If the meteorological stability condition is known, it
would be more accurate to use x = 2 for stability classes A and B;
x = 1.5 for classes C and D; and x = 1 for classes E and F.
Revised 6/79
5.11
-------
used to estimate exposure rate by plotting the exposure rates known
at specific locations on the curves. Exposure rates at other
locations are simple multiples of the known exposure rates as
indicated by the multipliers associated with each curve.
A third alternative for determining exposure rate patterns is
to obtain gamma exposure rate measurements at a large number of
locations and plot these data on a map of the area. This method
would provide the most accurate data but would require a large
number of radiation instruments and trained persons to make the
measurements as well as a method for communicating the data to the
control center on a continuing basis. This method is primarily
recommended for developing information for determining the need to
revise previous protective action recommendations. Protective
actions for plume exposure should be taken prior to plume arrival,
if possible.
5.H Dose Projection
The projected dose (or dose commitment in the case of inhaled
radionuclides) should be calculated only for the early phase of an
emergency. Early phase includes the duration of the plume exposure
for Inhalation PAG3 and up to 2 to U days following the accident for
whole body exposure. Exposures that may have occurred before the
dose projection is made are not normally to be used for evaluating
the need for protective actions. Radiation doses that might be
Revised 6/79
5.12
-------
received at later times following an accident alao should not be
included within the projected dose for this guidance. These latter
doses, which nay be from reentry operations, food pathways, or long
tern groundshine are committed over a longer tiae period and will
require different kinds of protective actions. Therefore, they will
require separate guidance recommendations to be addressed in
subsequent chapters.
The best method for early determination of the need for
protective actions immediately following an incident and prior to
the start of the release is for the facility operator to estimate
potential offsite dose based on information in the control room
using relationships developed during the planning stage that relate
abnormal plant conditions and meteorological conditions to potential
offsite doses. After the release starts and the release rate is
measurable and when plant conditions or instrumentation can be used
to estimate the characteristics of the release and release rate as a
function of time, then these factors, along with meteorological
conditions and windspeed and direction, can be used with techniques
presented here to estimate projected dose. Projected dose can also
be determined on the basis of environmental measurements when these
are available. Procedures are provided herein to use either release
rates or environmental measurements to project dose. Supporting
documentation for the procedures is provided in Appendix D.
Revised 6/79
5.13
-------
5.U.1 Duration of Exposure
Dose projection is a function of the time integrated exposure
rate or of the tiae integrated concentration. Although exposure
rate would most likely vary with time, this relationship cannot be
predicted. For purposes of these calculations, exposure rate is
assumed to be constant over the exposure period. Therefore,
projected dose becomes a product of exposure rate, duration of
exposure, and a dose conversion factor.
The time period of exposure may be difficult to predict.
Exposure would start at a particular site when the plume arrived and
would be ended by a change in wind direction or by an end to the
release. It is very important that arrangements be made for the
State or local weather forecast center to provide information on
current meteorological and wind conditions and predicted wind
direction persistence during the incidents in addition to
information received from the facility operator. If neither wind
change nor the tlae until the end of the release can be predicted,
the period of exposure could be conservatively assumed to be equal
to the 99t probable maximum duration of wind direction persistence
for that site and for existing meteorological stability conditions.
Historical data on wind direction persistence as a function of
atmospheric stability class for a particular site are available in
the Final Safety Analysis Report prepared by the facility operator.
Revised 6/79
5.14
-------
5.1.2 Whole Body Doae Projection
Having established exposure rate patterns in the environment
and having determined (or estimated) the time period of exposure,
the next task is to estimate the projected whole body and thyroid
doae to members of the population so that the projected dose can be
compared with appropriate PAGs.
An airborne release from a light water reactor would be
expected to consist primarily of radioactive noble gases and
iodines. If engineered safeguards operate as designed, they may
reduce iodine concentrations to levels such that the whole body
gamma radiation dose from noble gases will be the controlling
pathway. Otherwise, the controlling pathway will be inhalation of
radioiodines resulting in committed thyroid dose ranging up to
hundreds of times the whole body gaoma dose depending on the
effectiveness of the engineered safeguards.
To avoid the necessity for calculating projected doae at the
time of the incident, it is recommended that dose projection
nomograms be developed. Figures 5.1 and 5.2 (pages 5.17 and 5.19)
are examples of such nomograms. Appendix D provides details
regarding their development. Other shortcut dose projection methods
may have been developed by the facility operators that are fully as
accurate as these methods and should be used if appropriate.
Revised 6/79
5.15
-------
The projected whole body gamma dose can be estimated by simply
multiplying the gaooa exposure rate at a particular location by the
tlae period of exposure. (The doae conversion factor is assumed to
be 1). Figure 5.1 provides this multiplication. This figure also
provides a relationship between exposure rate in mR/hr and the noble
gas concentration based on the mixture of radioactive noble gases
that would be expected to exist at about 1.5 hours after shutdown.
Zf the noble gases have decayed for a longer time, these curves
would significantly overestimate the projected dose as determined
from concentrations and exposure time. If the gamma exposure rate
from a semi-infinite cloud of airborne noble gases is to be
determined from known mixtures other than those assumed, the
following relationship may be used:
5 n
R s 9 x 103 Z C E
. n n
where: R = exposure rate (mR/hr)
C s concentration in air (Ci/m ) for radionucU.de "n"
n
E s average gamma energy per disintegration (MeV) for
radlonuclide "n". See table 3*1 of Appendix D for
values of E for specific radionuclides.
9 x 10 s a dimensionless constant.
Revised 6/79
5.16
-------
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Revised 6/79
-------
This equation is the familiar expression for gamma exposure rate
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from R/sec to mR/hr.
5.U.3 Thyroid Dose Projection
Thyroid dose commitment from inhalation is primarily a function
of the concentrations of radioactive iodines in the air integrated
over the duration of exposure. This section provides techniques for
projecting the thyroid dose using a variety of types of data that
may be available. The bases for these techniques are provided in
Appendix D.
The basic data, concentration of iodines in the air and
duration of exposure, may be obtained from a variety of sources.
The concentration may be measured either as gross iodines or as
specific isotopes. The concentration may also be calculated based
on release rates and characteristics and meteorological conditions
or based on measured gamma exposure rates. The duration of exposure
may be predicted as discussed in section 5.1.1.
Figure 5.2 provides a family of curves for projected thyroid
dose as a function of airborne concentration (right ordinate) and
duration of exposure (abscissa).
To estimate projected thyroid dose for a particular site, plot
the point on figure 5.2 corresponding to the radioiodine
concentrations in Ci/m and the expected time period of exposure
for persons at that location. Using a logarithmic interpolation,
Revised 6/79
5.18
-------
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5.19
Revised 6/80
-------
estimate the projected thyroid doae from the dose values on the
curves below and above the point. For example, if the iodine
concentration is 10 Cl/m and is expected to last two hours,
then the projected adult thyroid dose would be approximately 6 rem,
and the child thyroid dose would be approximately 12 rem. Note that
the child thyroid dose is two times the adult thyroid dose. The
child dose would apply to general populations while the adult dose
would apply to emergency teams or to other adults.
Dose conversion factors to convert from time integrated
airborne concentrations to projected dose would vary as a function
of the time after reactor shutdown that concentrations were
determined. The dose conversion factors for iodine concentrations
used in figure 5.2 are based on a mix of radiolodlnes that would be
expected to exist at about 4 hours after reactor shutdown. If the
concentration were determined at some other time, the dose
conversion factor (and thus the projected doae) would be in error.
This error would be less than 30J for measurements made in the range
of 1-to 12 hours as shown in figure 4.4 of Appendix D. This error
is considered too small to Justify the use of a correction factor,
but figure 4.4 from Appendix D could be used for this purpose, if
desired.
Air samples would provide the best source of concentration data
for use in figure 5.2. However, with present day equipment, field
measurements of environmental radioiodine concentrations may be
Revised 6/79 (
5.20
-------
difficult and too time consuming for quick decisions on
implementation of protective actions. In the absence of measured
iodine concentrations in air, one may calculate the concentrations
based on release rates and meteorological conditions or based on
gamma exposure rate measurements in the environment.
5.1.3.1 Concentrations Based on Release Rates
If information is available on the total curies released or on
the release rate and duration of release, one can use these data
with meteorological information to calculate concentrations at
specific locations downwind. Similarly, this information can be
used to determine the downwind distance at which a particular
concentration would occur. These methods are discussed below.
Figure 5.3 provides the atmospheric dilution factor, xO/Q, as
a function of downwind distance and for different atmospheric
stability classes. This factor is the concentration (x> In Ci/m3
that would exist for an average windspeed (0) of 1 m/sec and for a
release rate (Q) of 1 curie/sec. To find the downwind concentration
(X) f.or a specific windspeed and release rate, divide the value of
xO/Q by the windspeed in m/sec and multiply by the release rate in
Cl/sec.
To find the projected thyroid dose associated with a particular
concentration, find the point corresponding to the concentration and
the estimated duration of exposure on the nomogram in figure 5.2.
Interpolate logarithmically between the dose lines as necessary.
Revised 6/79
5.21
-------
10
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These values assume
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Distance Downwind (Miles)
62
Figure 5.3 Typical values for XU/Q as a function of
atmospheric stability class and downwind distance
5.22
-------
If the release is expressed in total curies as opposed to
Ci/sec, any release period can be assumed for purposes of using
figure 5.2 to estimate the projected dose. Assuming a release
period of one hour, the total release in curies can be converted to
release rate in Ci/sec by dividing by 3600 sec/hr.
A more common problem may be to determine the downwind distance
at which a particular dose would occur. The following steps would
be appropriate for solving this problem.
1. From figure 5.2 (page 5.19) determine the iodine
concentration in Ci/m that would cause the thyroid dose of
concern for the estimated duration of the exposure.
2. Multiply this concentration "\" by the windspeed "0" in
m/sec and divide by the release rate "Q" in Ci/sec. This provides a
dilution factor, x^/Q (m~ ), which can be applied in figure 5.3
(page 5.22).
3. Using figure 5.3( follow the value for x^/Q across to the
existing stability class and follow this point down to find the
corresponding distance. This is the downwind distance where Che
dose of concern should occur at the plume center-line.
Example Problem
Assume an accident involves a puff release of 20,000 curies of
iodines. The release occurs at two hours after reactor shutdown,
the windspeed is 8 mph = 4 m/sec, and the atmospheric stability
class is D. Determine the downwind distance at which the projected
dose would be 5 rem to the child thyroid.
Revised 6/79
5.23
-------
Solution
Since no duration of exposure was given, one can assume one
hour = 3600 seconds for purposes of calculations.
From figure 5.2 (page 5.19) note that the concentration, x»
corresponding to a 5 rem dose to the child thyroid from a one hour
exposure would be about 8 x 10" Ci/m .
The release rate, Q, can be assumed to be
20.000 curies _ , C1/Ma
3,oOO seconds ' 5>5 C1/9ec
Therefore:
xO 8 x 10"6 Ci/m3 x Urn/sec , „ ,_-6 -2
Q = 5.5 Ci/sec = 5.8x10 m
From figure 5.3 (page 5.22) the distance corresponding to a dilution
factor of 5.8 x 10~ m" under stability class D is about 8 Km
or 5-miles.
S.^.3.2 Concentrations Based on Gamma Exposure Rate Measurements
If environmental concentrations of radioiodines are determined
from air samples at selected locations, it would be useful to obtain
simultaneous average gamma exposure rate measurements at the same
locations in accordance with recommendations of the Task Force on
Instrumentation (£). The ratio of gamma exposure rate to iodine
Revised 6/79
5.24
-------
concentration should be approximately constant for different
locations if the measurements are not spread out over more than
about 2 hours. The process of collecting and analyzing a few air
samples and estimating concentrations based on gamma exposure rate
measurements at other locations could save considerable monitoring
time.
If no air sample measurements are available, it is possible to
obtain a crude estimate of radloiodine air concentrations from gamma
exposure rate measurements. Because of the large potential for
errors, this would be the last choice of methods for estimating
airborne iodine concentrations.
The left ordinate in figure 5.2 (page 5.19) provides a
relationship between the ganna exposure rate from airborne
radioactive noble gases plus iodines and the radioiodine
concentration (right ordinate) that would contribute to this dose.
This relationship changes with the ratio of iodines to noble gases
in the release, the atmospheric stability class, time after
shutdown, the gaona exposure coming from material already deposited
on surfaces, and the gamma exposure from airborne particulate
material.
Because of the assumptions that were made in the development of
figure 5.2, its use to estimate thyroid inhalation dose solely on
the basis of gamma exposure rates without confirmatory concentration
Revised 6/79
5.25
-------
measurements or without correction factors would generally result in
projected thyroid doses higher than those that would actually
occur. The relationships in figure 5.2 between gamma exposure rate
and iodine concentration are based on the following assumptions:
1. The ratio of concentrations of iodines to noble gases would
be about 0.3 which is the ratio that corresponds to a mixture
consisting of 251 of the iodines and 100? of the noble gases in a
nuclear power reactor at full power equilibrium conditions. Figure
5.K provides correction factors that can be multiplied times the
gamma exposure rate before its use in figure 5.2 in situations where
actual values are provided for iodine to noble gas activity ratio.
2. The atmospheric stability class would be "A". Figure 5.5
provides correction factors as a function of downwind distance and
atmospheric stability class for use in situations where these data
are known.
3. Measurements would be made within the range of 1 to 12
hours after reactor shutdown. Concentrations based on measurements
made during the first 4 hours after shutdown would be slightly lower
than estimated, thus causing a conservative dose estimate.
Concentrations based on measurements made 6 or more hours after the
reactor shutdown would produce low dose estimates. However, this
nonconservatlve error would be somewhat compensated by the
conservative error introduced by the assumption that there would be
Revised 6/79
5.26
-------
Ul
•
10
IO»
7
3
10-*
e '
2 K
IL.
rt •»
CORRECT!
% M d
7
3
2
10-3
/
.
f
'
{
>
t
IT —
/
,
'
••••=**
/
/
7 ' '
y*
s
4
'
*
TO USE THIS GRAPH
Fid
1X1
RA
RA
•FA
•RA
TH
• IN
ID THE CORRECTION FACTOR
RRESPONDINQ TO THE KNOWN
DIOIOOINE/NOBLE GAS ACTIV
TIO. MULTIPLY THIS CORRECT
CTOR BY THE GAMMA EXPOSU
TE TO BE USED IN ESTIMATINC
E PROJECTED THVROIO DOSE
FIGURE 5.2
TV
ION
RE •
t
•
IB
D.
O>
J, / 10-3 2 3 b / lir* 23 67 10
HAOlOIUniNE TO NOBLE GAS ACIIVITV RATIO
Figure 5.4 Radioiodine release correction factor
7 10"
-------
I
1
§
§
Ml
8
TO USE THIS CHART. FIND
THE CORRECTION FACTOR
CORRESPONDING TO THE
DISTANCE AND ATMOSPHERIC
STABILITY CLASS AT WHICH
THE EXPOSURE MEASUREMENT
•AS MADE. AND MULTIPLY IT
BY THE MEASURED GAMMA
EXPOSURE RATE BEFORE ITS
USE IN FIGURE 5.2
1 U 2 3 4 I 671118 IS 20 30 40 SO 70 100
DISTANCE (KILOMETERS)
0.6
1
31 10
DISTANCE (MILES)
20
Figure 5.5 Gamma exposure rett finite cloud correction factor.
5.28
Revised 6/80
-------
no contribution to gaona exposure rate from radioiodinaa deposited
on the ground. Both of these errors would increase in intensity
with time after the start of the release.
Caution should be exercised in this method of estimating
thyroid dose to avoid projecting thyroid inhalation doses on the
basis of gamna exposure coining entirely from deposited material
after the plume has passed. For this situation the gamma exposure
rate would increase as the detector approached the ground.
Example Problem
No iodine concentration measurements have been made, but gamma
exposure rate measurements indicate maximum levels of 10 mR/hour at
2 miles downwind. The stability class is D, and the nuclear utility
reports the iodine to noble gas ratio in the release is 0.1. What
is the projected child thyroid dose for a 2 hour exposure?
Solution
Referring to figure 5.2 (page 5.19) the projected dose without
correction factors for 10 mR/hr and 2 hours is about 8 rem to the
child thyroid. From figure 5.5 (page 5.28) the correction factor
for D stability and 2 miles = 1.6. From Figure 5.1 (page 5.27) the
correction factor for iodine to noble gas ratio of 0.1 = 0.45.
10 mR/hr x 1.6 x .45 3 7.2 mR/hr. Referring to figure 5.2, the
corrected thyroid dose is projected to be slightly acre than 5 rem
for a 2 hour exposure.
Revised 6/79
5.29
-------
5.5 Protective Action Decisions
The noat effective protective actions for the plume exposure
pathway are evacuation and shelter. Access control is also
effective and appropriate but generally would be taken in
conjunction with one of the other two actions. When contamination
of the skin is suspected, protective actions such as washing and
changes of clothing are justified without the need for planned
procedures because these actions are easy to take and involve little
or no risk. Chapter 1 provides a general discussion of protective
actions, and Appendix B will provide planning guidance with regard
to evacuation and shelter. (Appendix B has not been published as of
this revision).
After dose projections are made and constraints are identified,
responsible officials oust decide what protective actions should be
implemented and in what areas. They must also decide which of the
emergency actions that were taken prior to having release
information from the facility or environmental measurements should
be expanded, maintained, or canceled.
Table 5.1 provides broad guidance for these decisions on the
basis of comparing projected doses to PAGs. This guidance is
primarily for planning purposes. Acceptable values for emergency
doses to the public under actual conditions of a nuclear accident
cannot be predetermined. Protective action recommendations in any
individual ease mus* be based on the actual conditions that exist
and are projected at the time of the accident.
Revised 6/79
5.30
-------
Table 5.1 Recommended protective actions to raduoa whole body and thyroid doaa fro* exposure to a gaaeoua plu
Projaoted Doaa (Ram) to
tha Population
Who la body <1
Thyroid <5
Whola body 1 to <5
Thyroid 5 to <25
Whola body 5 and above
Thyroid 25 and above
Projected Doaa (Bern) to
Emergency Team Workera
Whole body 25
Thyroid 125
Whola body 75
Recommended actions^*)
No planned protective aatlona.(°)
State nay Issue an advisory to aeek shelter and await
further Instructions.
Monitor environmental radiation levels.
Seek shelter aa a minimum.
Consider evacuation. Evacuate unless constraints sake
It lapractlcal.
Monitor environmental radiation levels.
Control access.
Conduct mandatory evacuation.
Monitor environmental radiation levels and adjust area
for mandatory evacuation baaod on these levels.
Control access.
Control exposure of emergency team members to these
levels except for llfesavlng missions. (Appropriate
controls Tor emergency workers, Include time
limitations, respirators, and atabla Iodine.)
Control exposure of emergency team members performing
lifesavlng missions to thla level. (Control of time
of exposure will be moat effective.)
Comments
Previously recommended
protective actions may
be reconsidered or
terminated.
If constraints exist,
special consideration
should be given for
evacuation of children
and pregnant women.
Seeking ahelter would be
an alternative If
evacuation were not
Immediately possible.
although respirators and
stable Iodine ahould be
used where effective to
control doae to
emergency team workers,
thyroid doae may not be
a limiting factor for
lifesavlng missions.
»»
'•'These actions are recoonended for planning purposes.
must take existing conditions Into consideration.
Protective action decisions at the time of the Incident
tha time of the Incident, officials may Implement low-Impact protective aotlons In keeping with the
principle of maintaining radiation exposures aa low aa reasonably achievable .
-------
PAGs cannot be used- to assure that a given level of exposure to
individuals in the population is prevented. In any particular
response situation, a range of doses may be experienced, depending
mostly on the distance from the point of release. Some of these
doses nay be in excess of the PAG levels and clearly warrant the
initiation of any feasible protective actions. This does not mean,
however, that all doses above PAG levels can be prevented.
Furthermore, PAGs represent only trigger levels and are not intended
to represent acceptable dose levels. PAGs are tools to be used in
planning and as decision aids in the actual response situation for
purposes of dose savings.
Under emergency conditions all reasonable measures should be
taken to minimize radation exposures to the general public and to
emergency workers. In the absence of significant constraints and in
consideration of the generally accepted public health practice of
limiting radiation exposures to as low as reasonably achievable
levels, responsible authorities may want to Implement low impact
protective actions at projected doses below the PAGs.
The recommendations provide a range of PAG values because
implementation of the guidance will always require the use of good
Judgment and a consideration of local constraints. The lowest value
should be used if there are no major local constraints in providing
protection at that level, especially to sensitive populations.
Revised 6/79
5.32
-------
Local constraints may make lower values Impractical to use, but in
no case should the higher value be exceeded in determining the need
for protective action. The question inevitably arises, then, at
uhat projected dose below the minimum PAG values should protective
actions no longer be considered. This is a value judgment on the
part of the emergency coordinator but should be based on the
following considerations:
a. Are the risks associated with taking protective action at
low projected doses greater than the risks associated with the low
projected radiation doses?
b. Is there a reasonable probability that the protective
action being considered can be successfully Implemented without
unreasonable coat or hardship on the participants?
c. At very low projected doses, efforts to protect the
population nay do more harm than good.
The intent is to anew for flexibility in the Implementation of
the guidance because local conditions will vary and because special
information may be available. But above the upper PAG range, there
is significant risk to the exposed populations, and responsible
agencies should consider it mandatory to plan to implement effective
protective actions, recognizing that when an accident actually
occurs, unforeseen conditions or constraints may prevail such that
professional Judgment will be required with regard to priorities for
protecting the public.
Revised 6/79
5.33
-------
Guidance for emergency workers 13 given aa dose limits becauae
It la recognized that critical civil functions oust continue while
protective actiona are taken for the general population, and this
nay require emergency workers to receive radiation exposures during
emergencies that otherwise would not be permitted. Exposure of
emergency workers to any dose level is not Justified unless it is
determined that benefits to society are being achieved and efforts
are being made to limit their doses to levels as low as reasonably
achievable. Emergency workers should consist of healthy adults and
should not include women that could potentially be pregnant.
Emergency response planning should provide for specialized
protection for emergency workers during emergency activities. This
would include respiratory protection, if needed, to reduce internal
organ and thyroid doses from inhalation and perhaps prophylactic
drugs that prevent thyroid exposures from inhaled radioiodine.
There should be appropriate instrumentation to verify exposures and
communication techniques to prevent overexposures by warning
emergency workers when to withdraw from radiation fields.
The health risk associated with dose limits recommended for
lifesavlng missions are extremely high, and such high doses should
be received only on a voluntary basis by individuals aware of the
risks involved. Lifesaving actions should be performed by persons
in good health whose normal duties have trained them for such
missions.
Revised 6/79
5.34
-------
REFERENCES
(1) U.S. NUCLEAR REGULATORY COMMISSION. An Assessment of Accident
Risks in U.S. Commercial Nuclear Power Plants. (WASH-1UOO),
U.S. Nuclear Regulatory Commission, Washington, D.C.,
October 1975.
(2) U.S. NUCLEAR REGULATORY COMMISSION. Guide and Checklist for
the Development and Evaluation of State and Local Government
Radiological Emergency Response Plans in Support of Fixed
Nuclear Facilities (WASH-1293). U.S. Nuclear Regulatory
Commission, Washington, D.C. December 1971.
(3) HANS, JOSEPH M., JR., AND THOMAS C. SELL. Evacuation Risks -
an Evaluation (EPA-520/6-7U-002). U.S. Environmental
Protection Agency, Washington, D.C. June 1971.
(JO NELSON, N. S. Approaches to Population Protection in Case of
Nuclear Accidents. U.S. Environmental Protection Agency,
Office of Radiation Programs, Washington, D.C. (Draft,
December 197
-------
CHAPTER 6
Implementing the PAGs for the Intermediate Phase
(Food and Mater)
See Chapter 3 and Appendix D for Current Implementation
Recommendations for Food. Also refer to the
following documents:
Federal Emergency Management Agency
Guidance Memorandum IN-1, The Ingestion Exposure
Pathway. February 26, 1988 Federal Emergency
Management Agency. Washington, DC 20472
Guidance on Offsite Emergency Radiation Measurement Systems
Phase 2, The Milk Pathway, FEMA REP-12, September 1987.
Guidance on Offsite Emergency Radiation Measurement Systems.
Phase 3, Mater and Non-Dairy Food Pathway, September 1989.
6-1
-------
Draft
CHAPTER 7
Implementing the Protective Action Guides for
the Intermediate Phase
(Exposure to Deposited Materials)
7.1 Introduction
This chapter provides guidance for implementing the PAGs set forth in
Chapter 4. It is for use by State and local officials in developing their
radiological emergency response plans to protect the public from exposure
to radiation from deposited radioactive materials. Due to the wide variety
in types of nuclear incidents and radionuclide releases that could occur,
it is not practical to provide implementing guidance for all situations.
The guidance in this chapter applies primarily to radionuclides that would
be involved in incidents at nuclear power plants. It may be useful for
radionuclides from incidents at other types of nuclear facilities or from
incidents not involving fixed facilities (e.g., transportation accidents).
However, specific implementation procedures for incidents other than those
at nuclear power plants should be developed by planners on a case-by-case
basis.
Contrary to the situation during the early phase of a nuclear
incident, when decisions usually must be made and implemented quickly by
State and local officials before Federal assistance is available, many
decisions and actions during the intermediate phase can be delayed until
Federal resources are present, as described in the Federal Radiological
Monitoring and Assessment Plan (FE-85). Because of the reduced level of
urgency for immediate implementation of these protective actions, somewhat
less detail may be needed in State radiological emergency response plans
than is required for the early phase.
7-1
-------
At the time of decisions on relocation and early decontamination,
sheltering and evacuation should have already been completed to protect
the public from exposure to the airborne plume and from high exposure
rates from deposited materials. These protective actions may have been
implemented prior to verification of the path of the plume and therefore
some persons may have been unnecessarily evacuated from areas where actual
doses are much lower than were projected. Others who were in the path of
the plume may have been sheltered or not protected at all. During the
intermediate phase of the response, persons must be relocated from areas
where the projected dose exceeds the PAG for relocation, and other actions
taken to reduce doses to persons who are not relocated from contaminated
areas. Persons evacuated from areas outside the relocation zone may
return.
7.1.1 Protective Actions
The main protective actions for reducing exposure of the public to
deposited radioactivity are relocation, decontamination, shielding, time
limits on exposure, and control of the spread of surface contamination.
Relocation is the most effective, and, usually, the most costly and
disruptive. It is therefore only applied when the dose is sufficiently
high to warrant it. The others are generally applied to reduce exposure
of persons who are not relocated, or who return from evacuation status to
areas that received lower levels of deposited radioactivity. This chapter
provides guidance for translating radiological conditions in the
environment to projected dose, to provide the basis for decisions on the
appropriate protective actions.
7.1.2 Areas Involved
Figure 7-1 provides a generalized example of the different areas and
population groups to be dealt with. The path of the plume is assumed to
be represented by area 1. In reality, variations in meteorological
conditions would almost certainly produce a more complicated shape, but
the same principles would apply.
7-2
-------
I
U)
ARBITRARY SCALE
PLUME TRAVEL
DIRECTION
LEGEND
| | 1.
PLUME DEPOSITION AREA.
2. AREA FROM WHICH POPULATION IS EVACUATED.
3. AREA IN WHICH POPULATION IS SHELTERED.
4. AREA FROM WHICH POPULATION IS RELOCATED (RESTRICTED ZONE).
FIGURE 7-1. RESPONSE AREAS.
-------
Because of plant conditions and other considerations prior to or
after the release, persons will already have been evacuated from area 2
and sheltered in area 3. Persons who have been evacuated from or
sheltered in areas 2 and 3, respectively, as precautionary actions for
protection from the plume, but whose homes are outside the plume
deposition area (area 1), may return to their homes as soon as
environmental monitoring verifies the boundary of the area that received
deposition (area 1).
Area 4 is designated a restricted zone and is defined as the area
where projected doses are equal to or greater than the relocation PAG.
Persons residing just outside the boundary of the restricted zone may
receive a dose near the PAG for relocation if decontamination or other
dose reduction efforts are not implemented.
Area 1, with the exception of the restricted zone, represents the
area of contamination that may continue to be occupied by the general
public. Nevertheless, there will be contamination levels in this area
that will require continued monitoring and dose reduction efforts other
than relocation.
The relative positions of the boundaries shown in Figure 7-1 depend
on areas evacuated and sheltered, and the radiological characteristics of
the release. For example, area 4 (the restricted zone) could fall
entirely inside area 2 (area evacuated), so that the only persons to be
relocated would be those residing in area 4 who were either missed in the
evacuation process or who, because of the high risk for their evacuation,
had remained sheltered during plume passage.
At the time the restricted zone is established, a temporary buffer
zone (not shown in Figure 7-1) may be needed outside portions of the
restricted zone in which occupants will not be allowed to return until
monitoring confirms the stability of deposited contamination. Such zones
would be near highly contaminated areas in the restricted zone where
deposited radionuclides might be resuspended and then redeposited outside
7-4
-------
the restricted zone. This could be especially important at locations
close to the incident site where the radioactivity levels are high and the
restricted zone may be narrow. The extent of the buffer zone will depend
on local conditions. Similarly, a buffer zone encompassing the most
highly contaminated areas in which persons are allowed to reside may be
needed. This area should be monitored routinely to assure acceptability
for continued occupancy.
7.1.3 Sequence of Events
Following passage of the airborne plume, several tasks, as shown in
Figure 7-2, must be accomplished simultaneously to provide for timely
protection of the public. The decisions on the early task of relocating
persons from high exposure rate areas must be based on exposure rate
measurements and dose analyses. It is expected that monitoring and dose
assessment will be an on-going process, with priority given to the areas
with the highest exposure rate. The general sequence of events is
itemized below, but the time frames will overlap, as demonstrated in
Figure 7-2.
1. Based on environmental data, determine the areas where the
projected one-year dose will exceed 2 rem and relocate persons from
those areas, with priority given persons in the highest exposure rate
areas.
2. Allow persons who were evacuated to return immediately to their
residences if they are in areas where field gamma measurements
indicate that exposure rates are near normal background levels (not
in excess of twice the normal background in the area before the
incident). If, however, areas of high deposition are found to be
near areas with low deposition such that resuspended activity could
drift into the occupied areas, a buffer zone should be established to
restrict occupancy until the situation is analyzed and dose
projections are confirmed.
7-5
-------
I I I III
I I I 11
(A
DC
§
111
Q
O
O
PERIOD OF
RELEASE,
DISPERSION,
DEPOSITION,
SHELTERING,
EVACUATION,
AND ACCESS
CONTROL
(NO TIME SCALE)
o
Ul
fci
o
o
CO
o
a
0.1
CONDUCT AERIAL AND GROUND SURVEYS. DRAW ISODOSE RATE LINES.
IDENTIFY HIGH DOSE RATE AREAS. CHARACTERIZE CONTAMINATION.
RELOCATE POPULATION FROM HIGH DOSE RATE AREAS.
ALLOW IMMEDIATE RETURN OF EVACUEES TO NONCONTAMINATED AREAS.
ESTABLISH RESTRICTED ZONE BOUNDARY AND CONTROLS.
RELOCATE REMAINING POPULATION FROM WITHIN RESTRICTED ZONE.
GRADUALLY RETURN EVACUEES UP TO RESTRICTED ZONE BOUNDARY.
CONDUCT D-CON AND SHIELDING EVALUATIONS AND ESTABLISH PROCEDURES
FOR REDUCING EXPOSURE OF PERSONS WHO ARE NOT RELOCATED.
PERFORM DETAILED ENVIRONMENTAL MONITORING.
PROJECT DOSE BASED ON DATA.
DECONTAMINATE ESSENTIAL FACILITIES AND THEIR ACCESS ROUTES.
RETRIEVE VALUABLE AND ESSENTIAL RECORDS AND POSSESSIONS.
REESTABLISH OPERATION OF VITAL SERVICES.
BEGIN RECOVERY ACTIVITIES.
CONTINUE RECOVERY.
MONITOR AND APPLY
ALARA IN OCCUPIED
CONTAMINATED AREAS.
I I I
I H
1.0 10 100
TIME AFTER DEPOSITION (DAYS)
1,000
FIGURE 7-2. POTENTIAL TIME FRAME OF RESPONSE TO A NUCLEAR INCIDENT.
-------
3. Determine the location of the isodose line corresponding to the
relocation PAG, establish the boundary of the restricted zone, and
relocate any persons who still reside within the zone. Also,
convert any evacuees who reside within the restricted zone to
relocation status. Evacuated persons whose residence is in the area
between the boundary of the plume deposition and the boundary to the
restricted zone may return gradually as confidence is gained
regarding the projected dose in the area.
4. Evaluate the dose reduction effectiveness of simple
decontamination techniques and of sheltering due to partial
occupancy of residences and workplaces. Results of these
evaluations may influence recommendations for reducing exposure
rates for persons who are not relocated from areas near, but
outside, the restricted zone.
5. Establish a mechanism for controlling access to and egress from
the restricted zone. Typically this would be accomplished through
control points at roadway accesses to the restricted zone.
6. Establish monitoring and decontamination stations to support
control of the restricted zone.
7. Implement simple decontamination techniques in contaminated areas
outside the restricted zone, with priorities for areas with higher
exposure rates and for residences of pregnant women.
8. Collect data needed to establish long-term radiation protection
criteria for recovery and data to determine the effectiveness of
various decontamination or other recovery techniques.
9. Begin operations to recover contaminated property in the
restricted zone.
7-7
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7.2 Establishment of Isodose-rate Lines
As soon as Federal or other assistance is available for aerial and
ground monitoring, a concentrated effort should begin to establish
isodose-rate lines on maps and the identification of boundaries to the
restricted zone. Planning for this effort should include the development
of standard maps that can be used by all of the involved monitoring and
dose assessment organizations to record monitoring data.
Aerial monitoring (e.g., the Department of Energy Aerial Monitoring
Service) can be used to collect data for establishing general patterns of
radiation exposure rates from deposited radioactive material. These
data, after translation to readings at 1 meter above ground, may form the
primary basis for the development of isodose lines out to a distance
where aerial monitoring shows no radiation above twice natural background
levels. Air sample measurements will also be needed to verify the
contribution to dose from inhalation of resuspended materials.
Gamma exposure rates measured at 1 meter will no doubt vary as a
function of the location of the measurement within a very small area.
This could be caused by different deposition rates for different types of
surfaces (e.g., smooth surfaces versus heavy vegetation). Rinsing or
precipitation could also reduce levels in some areas and raise levels in
others where runoff settles. In general, where exposure rates vary
within designated areas, the higher values should be used for dose
projection for persons within these areas unless judgment can be used to
estimate an appropriate average exposure rate.
Measurements made at 1 meter to project whole body dose from gamma
radiation should be made with instruments of the "closed window" type so
as to avoid the detection of beta radiation. Although beta exposure will
contribute to skin dose, its contribution to the overall risk of health
effects from the radionuclides expected to be associated with reactor
incidents should not be controlling in comparison to the whole body gamma
dose (AR-89). Special beta dose analyses may be appropriate when time
7-8
-------
permits to determine its contribution to skin dose. Since beta dose rate
measurements require sophisticated equipment that is generally not
available for field use, beta dose to the skin should be limited based on
measured concentrations of radionuclides per unit area.
7.3 Dose Projection
The primary dose of interest for reactor incidents is the sum of the
effective gamma dose equivalent from external exposure and the committed
effective dose equivalent from inhalation. The exposure periods of
interest are first year, second year, and up to 50 years after the
incident.
Calculation of the projected gamma dose from measurements will
require knowledge of the principal radionuclides contributing to exposure
and their relative abundances. Information on these radiological
characteristics can be compiled either through the use of portable gamma
spectrometers or by radionuclide analysis of environmental samples.
Several measurement locations may be required to determine whether any
selective radionuclide deposition occurred as a function of weather,
surface type, distance from the point of release, or other factors. As
part of the Federal Radiological Monitoring and Assessment Plan (FE-85),
the U. S. Department of Energy and the U. S. Environmental Protection
Agency have equipment and procedures to assist State officials in
performing environmental measurements, including determination of the
radiological characteristics of deposited materials.
The gamma exposure rate may decrease rapidly if deposited material
includes a significant fraction of short-lived radionuclides. Therefore,
the relationship between instantaneous exposure rate and projected first-
and second-year annual or the 50-year doses will change as a function of
time, and these relationships must be established for the particular mix
of deposited radioactive materials present at the time of the gamma
exposure rate measurement.
7-9
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For incidents involving releases from nuclear power plants, gamma
radiation from deposited radioactive materials is expected to be the
principal exposure pathway, as noted above. Other pathways should also
be evaluated, and their contributions considered, if significant. These
may include inhalation of resuspended material and beta dose to the
skin. Exposure from ingestion of food and water is normally limited
independently of decisions for relocation and decontamination (see
Chapters 3 and 6). In rare instances, however, where withdrawal of food
and/or water from use would, in itself, create a health risk, relocation
may be an appropriate protective action for protection from exposure via
ingestion. In this case, the committed effective dose equivalent from
ingestion should be added to the projected dose from other exposure
pathways for decisions on relocation.
The following sections provide methods for evaluating the projected
dose from whole body external exposure and from inhalation of resuspended
particulate material, based on environmental information.
7.3.1 Projected External Gamma Dose
Projected whole body external gamma doses at 1 meter height at
particular locations during the first year, second year, and over the
50-year period after the incident are the parameters of interest. The
environmental information available for calculating these doses is
expected to be the current gamma exposure rate at 1 meter height and the
relative abundance of each radionuclide contributing significantly to
that exposure rate. Calculational models are available for predicting
future exposure rates as a function of time due to radioactive decay and
weathering. Weathering is discussed in WASH-1400, Appendix VI (NR-75),
and information on the relationship between surface concentrations and
gamma exposure rate at 1 meter is addressed in reference (DO-88).
Following the incident, experiments should be conducted to determine
the dose reduction factors associated with part-time occupancy of
dwellings and workplaces, and with simple, rapid, decontamination
7-10
-------
techniques, so that these factors can also be applied to the calculation
of dose to persons who are not relocated. However, these factors should
not be included in the calculation of projected dose for decisions on
relocation.
Relocation decisions can generally be made on the basis of the first
year projected dose. However, projected doses during the second year and
over 50 years are needed for decisions on the need for other protective
actions for persons who are not relocated. Dose conversion factors are
therefore needed for converting environmental measurements to projected
dose during the first year, second year, and over 50 years following the
incident. Of the two types of environmental measurements that can be
made to project whole body external gamma dose, gamma exposure rate in
air is the easiest to make and is the most directly linked to gamma dose
rate. However, a few measurements of the second type (radionuclide
concentrations on surfaces) will also be needed to properly project
decreasing dose rates.
Tables 7-1 and 7-2 provide information to simplify the development
of dose conversion factors through the use of data on the radionuclide
mix, as determined from environmental measurements. These tables list
the deposited radionuclides most likely to be the major contributors to
dose from incidents at nuclear power facilities. In addition to
providing integrated, effective doses per unit of surface concentration,
they provide, in column three, the exposure rate (mR/h) in air per unit
of surface contamination. All exposure rate values are based on those
given in reference (DO-88). They were estimated from the total body
photon dose rate conversion factors for exposure at 1 m above the ground
surface. Since the ratio of effective dose to air exposure is about 0.7,
dividing the effective dose rate by 0.7 results in an estimate of the
exposure rate in air. The integrated effective doses are based on dose
conversion factors also listed in reference (00-88). Table 7-1 takes
into account both radioactive decay and weathering, whereas the values in
Table 7-2 include only radioactive decay. The effect of weathering is
uncertain and will vary depending on the type of weather, type of
7-11
-------
Table 7-1 Gamma Exposure Rate and Effective Dose Equivalent (Corrected for Radioactive Decay and
Radionucl
Zr-95
Nb-95
Ru-103
Ru-106
Te-132
V 1-131
ls>
1-132
1-133
1-135
Cs-134
Cs-137
Ba-140
La-140
Weathering) due to an
Half-life
ide hours
1.54E+03
8.41E+02
9.44E+02
8.84E+03
7.82E+01
1.93E+02
2.30E+00
2.08E+01
6.61E+00
1.81E+04
2.65E+05
3.07E+02
4.02E+01
Initial Uniform Concentration
Initial exposure3
rate at 1 m
(mR/h
per pCi/m2)
1.2E-08
1.3E-08
8.2E-09
3.4E-09
4.0E-09
6.6E-09
3.7E-08
l.OE-08
2.4E-08
2.6E-08
l.OE-08
3.2E-09
3.5E-08
of 1 pCi/
year 1
(mrem per
pCi/m2)
3.3E-05
(b)
7.1E-06
1.2E-05
3.2E-06
1.3E-06
(b)
2.1E-07
1.6E-07
l.OE-04
4.5E-05
1.1E-05
(b)
m^ on Ground Surface
Integrated dose
(weathering factor included)15
year 2
(mrem per
pCi/m2)
4.0E-07
(b)
0
3.7E-06
0
0
(b)
0
0
4.7E-05
2.9E-05
0
(b)
0-50 year
(mrem per
pCi/m2)
3.4E-05
(b)
7.1E-06
1.8E-05
3.2E-06
1.3E-06
(b)
2.1E-07
1.6E-07
2.4E-04
6.1E-04
1.1E-05
(b)
Estimated exposure rate at 1 meter above contaminated ground surface. Based on data from reference (00-88).
bRadionuclides that
assumed to quickly
the parent and the
have short-lived daughters (Zr/Nb-95, Te/I-132, Ru/Rh-106, Cs-137/Ba-137m, Ba/La-140) are
reach equilibrium. The integrated dose factors listed are the effective gamma dose due to
daughter. Based on data from reference (DO-88).
-------
Table 7-2 Exposure Rate and Effective Dose Equivalent (Corrected for Radioactive Decay) due to an Initial
2
Concentration of 1 pCi/m on Ground Surface
OJ
Integrated dose
Initial exposure3 (weathering factor not included)^
Radionuclide
Zr-95
Nb-95
Ru-103
Ru-106
Te-132
1-131
1-132
1-133
1-135
Cs-134
Cs-137
Ba-140
La-140
aEsti mated exposure
bRadionuclides that
assumed to quickly
Half-life
hours
1.54E+03
8.41E+02
9.44E+02
8.84E+03
7.82E+01
1.93E+02
2.30E+00
2.08E+01
6.61E+00
1.81E+04
2.65E+05
3.07E+02
4.02E+01
rate at 1 meter
rate at 1 m
(mR/h
per pCi/m^)
1.2E-08
1.3E-08
8.2E-09
3.4E-09
4.0E-09
6.6E-09
3.7E-08
l.OE-08
2.4E-08
2.6E-08
l.OE-08
3.2E-09
3.5E-08
above contaminated
year 1
(mrem per
pCi/m?)
3.8E-05
(b)
7.8E-06
1.5E-05
3.3E-06
1.3E-06
(b)
2.1E-07
1.6E-07
1.3E-04
6.0E-05
1.2E-05
(b)
ground surface. Based
have short-lived daughters (Zr/Nb-95, Ru/Rh-106, Te/I-132,
reach equilibrium. The integrated dose factors listed are
year 2
(mrem per
pCi/m2)
8.0E-07
(b)
0
7.6E-06
0
0
(b)
0
0
9.6E-05
5.9E-05
0
(b)
0-50 year
(mrem per
pCi/m2)
3.9E-05
(b)
7.8E-06
3.0E-05
3.3E-06
1.3E-06
(b)
2.1E-07
1.6E-07
4.7E-04
1.8E-03
1.2E-05
(b)
on data from reference (DO-88).
Cs-137/Ba-137m
the effective
, Ba/La-140) are
gamma dose due to
the parent and the daughter. Based on data from reference (00-88).
-------
surface, and the chemical form of the radionuclides. The user may choose
either table depending on the confidence accorded the assumed weathering
factors.
The following steps can be used to develop dose conversion factors to
calculate projected future doses from gamma exposure rate measurements for
specific mixes of radionuclides:
1. Using spectral analysis of gamma emissions from an environmental
sample of deposited radioactivity, determine the relative abundance
of the principal gamma emitting radionuclides. Analyses of uniform
samples from several different locations may be necessary to
determine whether the relative concentrations of radionuclides are
constant. The results may be expressed as the activity (pCi) of
each radionuclide in the sample.
2. Multiply each activity from step 1 by the corresponding values in
column 3 of Table 7-1 or Table 7-2 (depending on whether or not
weathering is to be considered) to determine the relative
contribution to the gamma exposure rate (mR/h) at 1-meter height for
each radionuclide. Sum the results for each sample.
3. Similarly, multiply each activity from step 1 by the corresponding
values in columns 4, 5, and 6 to determine the Ist-year, 2nd-year,
and 50-year relative integrated doses contributed by each
radionuclide. Sum these results for each sample. Radionuclides
listed in Tables 7-1 and 7-2 that have short-lived daughters
(Zr/Nb-95, Te/I-132, Ru/Rh-106, Cs-137/Ba-137m, Ba/La-140) were
assumed to be in equilibrium with their daughters when the tabulated
values for integrated dose were calculated. Since the values for
the parents include the total dose from the parent and the daughter,
do not double count these daughters in the sum. (In the cases of
Cs-137/Ba-137m, and Ru-106/Rh-106, the parents are not gamma
emitters, so the listed exposure rates and doses are actually
those from the daughters alone.)
7-14
-------
4. Using the results from steps 2 and 3, the relevant dose conversion
factors for each sample are then given by:
nrc
DCF
H^mrem)
n
XX.(mR/h)
n
where i indexes each of the n radionucTides present in the sample.
(Since the samples represented in the numerator and denominator are
identical, the effect of the size of the sample cancels.)
These dose conversion factors may be applied to any measured gamma
exposure rate for which the relative concentrations of radionuclides are the
same as those in the sample that was analyzed.
The following example demonstrates the use of the above procedures for
calculating a DCF. For purposes of the example it is assumed that
environmental measurements revealed a mix of radionuclides as shown in column
3 of Table 7-3. The (relative) exposure rate conversion factors in column 4
of Table 7-3 are taken from column 3 of Table 7-1. The (relative) exposure
rates in column 5 are the products of columns 3 and 4. The (relative) doses
for individual radionuclides in columns 6, 7, and 8 were calculated by
multiplying the concentrations in column 3 by the dose conversion factors in
columns 4, 5, and 6 of Table 7-1, respectively. (Columns 4, 5, and 6 of Table
7-2, which do not include weathering, could have been used instead of those in
Table 7-1.)
For this example, the conversion factor for dose in the first year was
obtained for the assumed radionuclide mix from the totals of columns 5 and 6
of Table 7-3, which indicate that a calculated dose of 0.023 mrem in the first
year corresponds to an initial exposure rate of 1.5E-4 mR/h. Therefore, the
first year dose conversion factor (DCF.) for this example is 150 mrem for
each mR/h measured at the beginning of the period.
7-15
-------
Table 7-3 Example Calculation of Dose Conversion Factors for Gamma Exposure Rate Measurements Based on
Measured Isotopic Concentrations
Radionuclide
Iodine-131
Tellurium-132
1-132
Ruthenium-103
Rhodium-106f
Cesium-134
Barium-137m^
Totals
Half-life
(hours)
193
78
2.3
944
8,840
18,100
265,000
Measured
concentration
(pCi/sampled)
2.6E+2
3.6E+3
3.6E+3
2.2E+2
5.0EH
6.8E+1
4.2E+1
mR/hC
2
pCi/m
6.6E-9
4.0E-9
3.7E-8
8.2E-9
3.4E-9
2.6E-8
l.OE-8
Calculated
Exposure rate
at 1 m (mR/hr)
1.7E-6
1.4E-5
1.3E-4
1.8E-6
1.7E-7
1.8E-6
4.2E-7
1.5E-4
Calculated
year 1
(mrem)
3.3E-4
1.2E-2
(e)
1.6E-3
5.8E-4
6.9E-3
1.9E-3
2.3E-2
effective dose
year 2
(mrem)
0
0
(e)
0
1.9E-4
3.2E-3
1.2E-3
4.6E-3
at 1 meter
50 year
(mrem)
3.3E-4
1.2E-2
(e)
1.6E-3
9.2E-4
1.6E-2
2.6E-2
5.6E-2
aThe data in this table are only examples to demonstrate a calculational process. The results should not be
used in the prediction of relationships that would exist following a nuclear incident.
''Calculations are based on data in Table 7-1, which includes consideration of both radioactive decay and
weathering.
cExternal exposure rate factors at 1 meter above ground for a person standing on contaminated ground, based
on data in Table 7-1.
dThe size of the sample is not important for this analysis because only the relative concentrations are needed
to calculate the ratio of integrated dose to exposure rate.
eThe integrated dose from 1-132 is not calculated separately because it is the short-lived daughter of Te-132,
and is assumed to be in equilibrium with it. The assumed quantity present is that for a daughter in
equilibrium with the parent.
fThis is a short lived daughter of a parent that has no gamma emissions and the halflife given is that of the
parent.
-------
This DCF may be multiplied by any gamma exposure rate measurement to
estimate the dose in the first year for locations where the exposure rate
is produced by a radionuclide mix the same as assumed for calculating the
DCF, and where weathering affects the exposure rate in the same manner as
assumed. For example, if a gamma exposure rate measurement were taken at
the location where the contamination sample in Table 7-3 was taken, this
exposure rate could be multiplied by the DCF calculated in the above
example to obtain the projected first year dose at that point. Based on
the example analysis and a relocation PAG of 2 rem, for this case the
exposure rate at the boundary of the restricted zone should be no greater
than
2000 mrem
150 mrem/mR/h ~ *'
if the contribution to effective dose from inhalation of resuspended
radioactive materials is zero (See Section 7.3.2). The example DCF for the
second year and 50 years are obtained by a similar process, yielding DCFs
of 31 and 370 mrem per mR/h, respectively.
The ratio of the second year to first year dose is 31/150 = 0.21. If
this is the case, persons not relocated on the basis of a 2 rem PAG should,
for this example, receive no more than 0.21 x 2 = 0.4 rem in year 2.
Similarly, the dose in fifty years should be no more than 4.9 rem. Actual
doses should be less than these values to the extent that exposure rates
are reduced by shielding from structures and by decontamination.
Prior to reaching conclusions regarding the gamma exposure rate that
would correspond to the relocation PAG, one would need to verify by
multiple sampling the consistency of the relative abundance of specific
radionuclides as well as the relative importance of the inhalation pathway.
Dose conversion factors will change as a function of the radiological
makeup of the deposited material. Therefore, dose conversion factors must
be calculated based on the best current information following the incident.
Since the relative concentrations will change as a function of time due to
different decay rates, dose conversion factors must be calculated for
7-17
-------
specific measurement times of interest. By calculating the decay of the
original sample(s), a plot of dose conversion factors (mrem per mR/h) as a
function of time after the incident can be developed. As weathering
changes the radionuclide mix, and as more is learned about other dose
reduction mechanisms, such predictions of dose conversion factors may
require adjustment.
7.3.2 Inhalation Dose Projection
It can be shown, for the mixture of radionuclides assumed to be
deposited from postulated reactor incidents, and an assumed average
resuspension factor of 10" m~ , that the effective dose from
inhalation is small compared to the corresponding effective dose from
external exposure to gamma radiation. However, air sample analyses should
be performed for specific situations (e.g., areas of average and high
dynamic activity) to determine the magnitude of possible inhalation
exposure. The 50-year committed effective dose equivalent (H5Q)
resulting from the inhalation of resuspended airborne radioactive materials
is calculated as follows:
H5Q = I x DCF (1)
where
I = total intake (uCi), and
DCF = committed effective dose equivalent per unit intake (rem/yCi).
It is assumed that the intake rate will decrease with time due to
radioactive decay and weathering. No model is available to calculate the
effect of weathering on resuspension of deposited materials, so the model
developed for calculating its effect on gamma exposure rate (NR-75) is
assumed to be valid. This should provide conservative results. The total
intake (I) from inhalation over time t may be calculated for each
radionuclide, using the following equation:
. BC [i (i-e-l) + (l-e- )] (2)
o x \ A \
7-18
-------
where
B = average breathing rate for adults
= 1.05E+4 m3/a (EP-88),
C = initial measured concentration of the resuspended
0 3
radionuclide in air (pCi/m ),
t = time during which radionuclides are inhaled (a),
x, = radioactive decay constant (a~ ),
assumed weathering decay constant for 63 percent of the
_i
deposited activity, taken as 1.13 a (NR-75), and
\3 = assumed weathering decay constant for 37 percent of the
deposited activity, taken as 7.48 E-3 a'1 (NR-75).
Table 7-4 tabulates results calculated using the above assumptions
for weathering. The table contains factors relating the committed
effective dose from exposure during the first and second years after the
incident to an initial air concentration of 1 pCi/m for each of the
principal radionuclides expected to be of concern from reactor
incidents. The dose conversion factors are taken from FGR-11 (EP-88).
Parent radionuclides and their short lived daughters are grouped together
because these dose conversion factors are based on the assumption that
both parents and daughters will occur in equal concentrations and will
decay with the half life of the parent. Therefore, measured
concentrations of the short lived daughters should be ignored and only
the parent concentrations should be used in calculating long term
projected doses.
Table 7-4 lists factors which include the effects of both weathering
and radioactive decay, as well as those that include only the effects of
radioactive decay. Users of these data should decide which factors to
use based on their confidence on the applicability of the weathering
models used (NR-75) to their environment.
7-19
-------
Table 7-4 Dose Conversion Factors for Inhalation of Resuspended Material
N>
O
Committed effective dose equivalent from specified exposure periods
based on an initial concentration of one pCi/m^ in air (with
and without weathering)
Committed dose3
considering radioactive
decay and weathering
(mrem per
Committed dose3
considering radioactive
decay only
(mrem per pCi/m3)
Radionuclide^
Sr-90/Y-90
Zr-95/Nb-95
Ru-103
Ru-106/Rh-106
Te-132/I-132
1-131
Cs-134
Cs-137/Ba-137m
Ba-140/La-140
Ce-144/Pr-144
Lung class0
Y/Y
Y/Y
Y
Y/D
W/D
0
0
D/0
D/W
Y/Y
year 1
9.3E 0
6.8E-2
1.3E-2
2.8E 0
1.3E-3
1.1E-2
3.2E-1
2.4E-1
4.5E-3
2.0E 0
year 2
5.5E 0
0
0
l.OE 0
1.9E-5
0
1.5E-1
1.4E-1
0
4.2E-1
year 1
1.4E+1
7.9E-2
1.5E-2
3.7E 0
1.3E-3
1.1E-2
4.1E-1
3.3E-1
4.7E-3
2.7E 0
year 2
1.3E+1
0
0
1.9E 0
1.9E-5
0
3.0E-1
3.2E-1
0
9.8E-1
Calculated using dose factors from Table 2.1. Reference EP-88
bShort lived daughters are not listed separately because the entries include the dose from both the
daughter and the parent. These factors are based on the concentration of the parent only, at the
beginning of the exposure period.
cThe lung clearance class chosen was the one which results in the highest dose conversion factor.
-------
The committed effective dose equivalent is calculated by multiplying
the measured initial air concentration (pCi/m ) for each radionuclide
of concern by the appropriate factor from the table and summing the
results. This sum may then be added to the corresponding external whole
body gamma dose to yield the total committed effective dose equivalent
from these two pathways.
The PAGs include a guide for dose to skin which is 50 times the
magnitude of the PAG for effective dose. Analysis (AR-89) indicates that
this guide is not likely to be controlling for radionuclide mixes expected
to be associated with nuclear power plant incidents. Dose conversion
factors are provided in Table 7-5 for use in case of incidents where the
source term consists primarily of pure beta emitters. The skin dose from
each radionuclide may be calculated by multiplying the measured concen-
2
tration (pCi/m ) by the corresponding dose conversion factor in the
table. This will yield the first year beta dose to the skin at one meter
height from exposure to deposited materials plus the estimated dose to
the skin from materials deposited on the skin as a result of being in the
contaminated area. These factors are calculated based on information in
Reference AR-89, which used weathering factors that apply for gamma
radiation and would, therefore, be conservative for application to beta
radiation. Calculated doses based on these factors should be higher than
the doses that would be received.
7.4 Priorities
In most cases protective actions during the intermediate phase will
be carried out over a period of many days. It is therefore useful to
consider what priorities are appropriate. Further, for situations where
the affected area is so large that it is impractical to relocate all of
the public, especially from areas exceeding the PAGs by only a small
amount, priorities are needed for protective actions. The following
priorities are appropriate:
1. As a first priority, assure that all persons are protected
from doses that could cause acute health effects from all
exposure pathways, including previous exposure to the plume.
7-21
-------
Table 7-5 Skin Beta Dose Conversion Factors for Deposited Radionuclides3
Radionuclides
Co-58
Co-60
Rb-86
Sr-89
Sr-90
Y-90
Y-91
Zr-95
Nb-95
Mo-99
Tc-99m
Ru-103
Ru-106c
Rh-105
Sb-127
Te-127
Te-127m
Te-129
Te-129m
Te-131m
Te-132
1-131
1-132
Cs-134
CS-136C
Cs-137C
Ba-140
La-140
Ce-141
Ce-143
Ce-144C
Pr-143
Nd-147
Np-239
Am-241
Dose conversion
(mrem per
factors'5
pCi/m2)
Radioactive decay Radioactive
plus weathering decay only
1.2E-7
4.2E-7
6.3E-5
1.5E-4
1.2E-5
2.2E-4
1.6E-4
7.2E-7
6.1E-7
4.4E-6
7.7E-9
6.8E-7
6.4E-7
6.5E-8
3.4E-6
l.OE-6
7.8E-7
5.0E-7
3.4E-5
2.9E-7
5.4E-9
8.5E-7
5.0E-5
2.6E-5
1.4E-7
2.1E-5
9.1E-6
1.2E-5
6.6E-7
2.3E-6
8.7E-7
1.3E-5
4.3E-6
3.4E-8
4.6E-8
1.4E-7
5.6E-7
6.7E-5
1.6E-4
1.7E-5
2.9E-4
1.9E-4
8.3E-7
7.4E-7
4.6E-6
7.7E-9
7.8E-7
8.7E-7
6.6E-8
3.4E-6
l.OE-6
9.5E-7
5.0E-7
3.6E-5
2.9E-7
5.4E-9
8.7E-7
5.0E-5
3.3E-5
3.7E-7
2.9E-5
9.6E-6
1.3E-5
7.1E-7
2.3E-6
1.1E-6
1.4E-5
4.5E-6
3.4E-8
6.4E-8
aBased on data from reference AR-89.
^Dose equivalent integrated for a one-year exposure at one meter height plus
the estimated dose to the skin from materials deposited on the skin as a
result of being in the contaminated area.
contributions from short-lived (one hour or less) decay products are
included in dose factors for the parent radionuclides "(i.e., Rh-106, Ba-136,
Ba-137, and Pr-144).
7-22
-------
2. Recommend the application of simple decontamination techniques
and that persons remain indoors as much as possible to reduce
exposure rates.
3. Establish priorities for relocation with emphasis on high
exposure rate areas and pregnant women (especially those in the
8th to 15th week of pregnancy).
7.5 Reentry
After the restricted zone is established, persons will need to
reenter for a variety of reasons, including recovery activities, retrieval
of property, security patrol, operation of vital services, and, in some
cases, care and feeding of farm and other animals. It may be possible to
quickly decontaminate access ways to vital institutions and businesses in
certain areas so that they can be occupied by adults either for living
(e.g., institutions such as nursing homes, and hospitals) or for
employment. Clearance of these areas for such occupancy will require dose
reduction to comply with occupational exposure limits (EP-87). Dose
projections for individuals should take into account the maximum expected
duration of exposure.
Persons working in areas inside the restricted zone should operate
under the controlled conditions normally established for occupational
exposure (EP-87).
7.6 Surface Contamination Control
Areas under the plume can be expected to contain deposited
radioactive materials if aerosols or particulate materials were released
during the incident. In extreme cases, individuals and equipment may be
highly contaminated, and screening stations will be required for emergency
monitoring and decontamination of individuals and to evaluate the need for
medical evaluation. Equipment should be checked at this point and
decontaminated as necessary to avoid the spread of contamination to other
7-23
-------
locations. This screening service would be required for only a few days
following plume passage until all such persons have been evacuated or
relocated.
After the restricted zone is established, based on the PAGs for
relocation, adults may reenter the restricted zone under controlled
conditions in accordance with occupational exposure standards. Monitoring
stations will be required along roadways to control surface contamination
at exits from the restricted zone. Because of the possibly high
background radiation levels at control points near exits, significant
levels of surface contamination on persons and equipment may be
undetectable at these locations. Therefore, additional monitoring and
decontamination stations may be needed at nearby low background
locations. Decontamination and other measures should be implemented to
maintain low exposure rates at monitoring stations.
7.6.1 Considerations and Constraints
Surface contamination limits to control routine operations at
nuclear facilities and to transport radioactive material are generally set
at levels lower than are practical for situations involving high-level,
widespread contamination of the environment.
The principal exposure pathways for loose surface contamination on
persons, clothing, and equipment are (a) internal doses from ingestion by
direct transfer, (b) internal doses from inhalation of resuspended
materials, (c) beta dose to skin from contaminated skin or clothing or
from nearby surfaces, and (d) dose to the whole body from external gamma
radiation.
Because of the difficulties in predicting the destiny of
uncontrolled surface contamination, a contaminated individual or item
should not be released to an unrestricted area unless contamination levels
are low enough that they produce only a small increment of risk to health
(e.g., less than 20 percent), compared to the risk to health from the
principle exposure pathway (e.g., whole body gamma dose) in areas
7-24
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immediately outside the restricted zone. On the other hand, a level of
contamination comparable to that existing on surfaces immediately outside
the restricted zone may be acceptable on materials leaving the restricted
zone. Otherwise, persons and equipment occupying areas immediately
outside the restricted zone would not meet the surface contamination
limits. These two constraints are used to set permissible surface
contamination limits.
The contamination limit should also be influenced by the potential
for the contamination to be ingested, inhaled, or transferred to other
locations. Therefore, it is reasonable to establish lower limits for
surfaces where contamination is loose than for surfaces where the
contamination is fixed.
For routine (nonincident) situations, measurement of gross
beta-gamma surface contamination levels is commonly performed with a
thin-window geiger counter (such as a CDV-700). Since beta-gamma
measurements made with such field instruments cannot be interpreted in
terms of dose or exposure rate, the guidance set forth below is related to
the background radiation level in the area where the measurement is being
made. Supplementary levels are provided for gamma exposure rates measured
with the beta shield closed. Guidance levels expressed in this form will
be easily detectable and should satisfy the above considerations.
Corresponding or lower levels expressed in units related to instrument
designations may be adopted for convenience or for ALARA determinations.
Smears may also be used to detect loose surface contamination at very low
levels. However, they are not considered necessary for emergency response
and, therefore, such guidance is not provided.
7.6.2 Numerical Relationships
As discussed in Section 7.3.1, a relationship can be established
between projected first year doses and instantaneous gamma exposure rates
from properly characterized surface contamination. Based on assumed
radiological characteristics of releases from fuel melt accidents, gamma
exposure rates in areas where the projected dose is equal to the
7-25
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relocation PAG of 2 rem in the first year may be in the range of 2 to 5
uiR/h during the first few days following the deposition from a type SST-2
accident (See Section E.I.2). (This relationship must be determined for
each specific release mixture.) Based on relationships in reference
(DO-88) and a mixture of radionuclides expected to be typical of an SST-2
8 2
type accident, surface contamination levels of 2x10 pCi/m would
correspond approximately to a gamma exposure rate of 1 mR/h at 1 meter
height.
7.6.3 Recommended Surface Contamination Limits
Surface contamination must be controlled both before and after
relocation PAGs are implemented. Therefore, this section deals with the
control of surface contamination on persons and equipment being protected
during both the early and intermediate phases of a nuclear incident.
For emergency situations, the following general guidance regarding
surface contamination is recommended:
1. Do not delay urgent medical care for decontamination efforts or
for time-consuming protection of attendants.
2. Do not waste effort trying to contain contaminated wash water.
3. Do not allow monitoring and decontamination to delay evacuation
from high or potentially high exposure rate areas.
4. (Optional provision, for use only if a major contaminating event
occurs, and rapid early screening is needed.) After plume
passage, it may be necessary to establish emergency
contamination screening stations in areas not qualifying as low
background areas. Such areas should be less than 5 mR/h gamma
exposure rate. These screening stations should be used only
during the early phase and for major releases of particulate
materials to the atmosphere to monitor persons emerging from
possible high exposure areas, provide simple (rapid)
decontamination if needed, and make decisions on whether to send
7-26
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them for special care or to a monitoring and decontamination
station in a lower background area. Table 7-6 provides guidance
on surface contamination levels for use if such centers are needed.
5. Establish monitoring and personnel decontamination (bathing)
facilities at evacuation centers or other locations in low
background areas (less than 0.1 mR/h). Encourage evacuated
persons who were exposed in areas where inhalation of particulate
materials would have warranted evacuation to bathe, change
clothes, wash clothes, and wash other exposed surfaces such as
cars and trucks and their contents and then report to these
centers for monitoring. Table 7-7 provides recommended surface
contamination guidance for use at these centers.
6. After the restricted zone is established, set up monitoring and
decontamination stations at exits from the restricted zone.
Because of the probably high background radiation levels at these
locations, low levels of contamination may be undetectable. If
contamination levels are undetectable, then they probably do not
exceed those in some unrestricted areas occupied by the exposed
population and no decontamination is required. Nevertheless,
these individuals should be advised to bathe and change clothes at
their first opportunity and certainly within the next 24 hours.
If, after decontamination at the boundary of the restricted zone
station, persons still exceed the limits for this station, they
should be sent for further decontamination or for medical or other
special attention. As an alternative to decontamination,
contaminated items other than persons or animals may be retained
in the restricted zone for radioactive decay.
7. Establish auxiliary monitoring and decontamination stations in low
background areas (background less than 0.1 mR/h). These stations
should be used to achieve ALARA surface contamination levels.
Table 7-7 provides surface contamination screening levels for use
at those stations.
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Table 7-6 Recommended Surface Contamination Screening Levels for
Emergency Screening of Persons and Other Surfaces at Screening
or Monitoring Stations in High Background Radiation Areas
(0.1 mR/h to 5 mR/h Gamma Exposure)3
Condition
Geiger-counter shielded-
window reading
Recommended action
Before decontamination
<2X bkgd and <0.5 mR/h
above background
>2X bkgd or >0.5 mR/h
above background
Unconditional
release
Decontaminate.
Equipment may be
stored or disposed
of as appropriate.
After decontamination
<2X bkgd and <0.5 mR/h
above background
>2X bkgd or >0.5 mR/h
above background
Unconditional
release
Continue to
decontaminate or
refer to low back-
ground monitoring
and d-con station.
Equipment may also
be stored for
decay or disposed
of as appropriate.
a Monitoring stations in these high exposure rate areas are for use
only during the early phase of an incident involving major atmos-
pheric releases of particulates. Otherwise use Table 7-7.
7-28
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Table 7-7 Recommended Surface Contamination Screening Levels for Persons
and Other Surfaces at Monitoring Stations in Low Background
Radiation Areas (<0.1 mR/h Gamma Exposure Rate)
Condition
Before decontamination
After simple
decontamination effort
After fullc
decontamination
effort
After additional
full decontamination
effort
Geiger counter
thin window3 reading
<2X bkgd
>2X bkgd
<2X bkgd
>2X bkgd
<2X bkgd
>2X bkgd
<0.5 mR/hd
<2X bkgd
>2X bkgd
<0.5 mR/hd
>0.5 mR/hd
Recommended action
Unconditional release
Decontaminate
Unconditional release
Full
decontamination
Unconditional release
Continue to d-con
persons
Release animals
and equipment
Unconditional release
Send persons for
special evaluation
Release animals
and equipment
Refer, or. use
informed judgment on
further control of
animals and equipment
a Window thickness of approximately 30mg/cm2 is acceptable. Recommended
limits for open window readings are expressed as twice the existing
background (including background) in the area where measurements are being
made. Corresponding levels, expressed in units related to instrument
designations, may be adopted for convenience. Levels higher than twice
background (not to exceed the meter reading corresponding to 0.1 mR/h) may
be used to speed the monitoring of evacuees in very low background areas.
b Flushing with water and wiping is an example of a simple
decontamination effort.
c Washing or scrubbing with soap or solvent followed by flushing is an
example of a full decontamination effort.
d Closed shield reading including background.
7-29
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References
AR-89 AABERG, ROSANNE, Battelle Northwest Laboratories. Evaluation of Skin
and Ingestion Exposure Pathways. U.S. Environmental Protection
Agency/Office of Radiation Programs, Washington, D.C. 20460, June
1989.
DO-88 U.S. DEPARTMENT OF ENERGY. External Dose-Rate Conversion Factors
for Calculation of Dose to the Public. DOE/EH-0070 U.S. Department
of Energy, Washington, D.C. 20545, July 1988.
EP-87 U.S. ENVIRONMENTAL PROTECTION AGENCY. Radiation Protection Guidance
to Federal Agencies for Occupational Exposure. Federal Register.
Vol. 52, No. 17, Page 2822, U.S. Government Printing Office,
Washington, DC 20402, January 1987.
EP-88 U.S. ENVIRONMENTAL PROTECTION AGENCY. Limiting Values of
Radionuclide Intake and Air Concentration and Dose Conversion
Factors for Inhalation, Submersion, and Ingestion. EPA
520/1-88-020. U.S. Environmental Protection Agency, Washington,
D.C. 20460, September 1988.
FE-85 FEDERAL EMERGENCY MANAGEMENT AGENCY. Federal Radiological Emergency
Response Plan (FRERP). Federal Register Vol. 50, No. 217, U.S.
Government Printing Office, Washington, DC 20402, November 5, 1985.
NR-75 U. S. NUCLEAR REGULATORY COMMISSION. Reactor Safety Study. An
Assessment of Accident Risks in U. S. Commercial Nuclear Power
Plants. WASH-1400. NUREG-75/014. U.S. Nuclear Regulatory
Commission, Washington, DC 20555, October 1975.
7-30
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Chapter 8
Radiation Protection Guides for
The Late Phase (Recovery)
(Reserved)
-------
APPENDIX A
Glossary
-------
APPENDIX A
Glossary
The following definitions apply specifically to terms used in this manual.
Acute health effects: Prompt radiation effects (those that would be
observable within a short period of time) for which the severity of the
effect varies with the dose, and for which a practical threshold exist.
Ablation; The functional destruction of an organ through surgery or
exposure to large doses of radiation.
Buffer zone: An expanded portion of the restricted zone selected for
temporary radiation protection controls until the stability of
radioactivity levels in the area is confirmed.
Cloudshine: Gamma radiation from radioactive materials in an airborne
plume.
Committed dose: The radiation dose due to radionuclides in the body over
a 50 year period following their inhalation or ingestion.
Delayed health effects: Radiation effects which are manifested long after
the relevant exposure. The vast majority are stochastic, that is, the
severity is independent of dose and the probability is assumed to be
proportional to the dose, without threshold.
Derived response level (DRL): A level of radioactivity in an
environmental medium that would be expected to produce a dose equal to its
corresponding Protective Action Guide.
Dose conversion factor: Any factor that is used to change an
environmental measurement to dose in the units of concern.
A-l
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Dose equivalent: The product of the absorbed dose in rad, a quality
factor related to the biological effectiveness of the radiation involved
and any other modifying factors.
Effective dose equivalent: The sum of the products of the dose equivalent
to each organ and a weighting factor, where the weighting factor is the
ratio of the risk of mortality from delayed health effects arising from
irradiation of a particular organ or tissue to the total risk of mortality
from delayed health effects when the whole body is irradiated uniformly to
the same dose.
Evacuation: The urgent removal of people from an area to avoid or reduce
high-level, short-term exposure, usually from the plume or from deposited
activity. Evacuation may be a preemptive action taken in response to a
facility condition rather than an actual release.
Genetic effect: An effect in a descendant resulting from the modification
of genetic material in a parent.
Groundshine: Gamma radiation from radioactive materials deposited on the
ground.
Incident phase: This guidance distinguishes three phases of an incident
(or accident): (a) early phase, (b) intermediate phase, and (c) late phase.
(a) Early phase: The period at the beginning of a nuclear incident
when immediate decisions for effective use of protective actions
are required, and must be based primarily on predictions of
radiological conditions in the environment. This phase may last
from hours to days. For the purpose of dose projection, it is
assumed to last for four days.
(b) Intermediate phase: The period beginning after the incident
source and releases have been brought under control and reliable
environmental measurements are available for use as a basis for
decisions on additional protective actions and extending until
A-2
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these protective actions are terminated. This phase may overlap
the early and late phases and may last from weeks to many
months. For the purpose of dose projection, it is assumed to
last for one year.
(c) Late phase: The period beginning when recovery action designed
to reduce radiation levels in the environment to permanently
acceptable levels are commenced, and ending when all recovery
actions have been completed. This period may extend from months
to years (also referred to as the recovery phase).
Linear Energy Transfer (LET): A measure of the ability of biological
material to absorb ionizing radiation; specifically, for charged particles
traversing a medium, the energy lost per unit length of path as a result
of those collisions with elections in which the energy loss is less than a
specified maximum value. A similar quantity may be defined for photons.
Nuclear incident: An event or series of events, either deliberate or
accidental, leading to the release, or potential release, into the
environment of radioactive materials in sufficient quantity to warrant
consideration of protective actions.
Prodromal effects: The forewarning symptoms of more serious health effects.
Projected dose: Future dose calculated for a specified time period on the
basis of estimated or measured initial concentrations of radionuclides or
exposure rates and in the absence of protective actions.
Protective action: An activity conducted in response to an incident or
potential incident to avoid or reduce radiation dose to members of the
public (sometimes called a protective measure).
Protective Action Guide (PAG): The projected dose to standard man, or other
defined individual, from an accidental release of radioactive material at
which a specific protective action to reduce or avoid that dose is warranted.
A-3
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Recovery: The process of reducing radiation exposure rates and
concentrations of radioactive material in the environment to levels
acceptable for unconditional occupancy or use.
Reentry: Temporary entry into a restricted zone under controlled
conditions.
Relocation: The removal or continued exclusion of people (households)
from contaminated areas to avoid chronic radiation exposure.
Restricted zone: An area with controlled access from which the population
has been relocated.
Return: The reoccupation of areas cleared for unrestricted residence or
use.
Sheltering: The use of a structure for radiation protection from an
airborne plume and/or deposited radioactive materials.
Short-lived daughters: Radioactive progeny of radioactive isotopes that
have half-lives on the order of a few hours or less.
Weathering factor: The fraction of radioactivity remaining after being
affected by average weather conditions for a specified period of time.
Weighting factor: A factor chosen to approximate the ratio of the risk of
fatal cancer from the irradiation of a specific tissue to the risk when
the whole body is irradiated uniformly to the same dose.
Whole body dose: Dose resulting from uniform exposure of the entire body
to either internal or external sources of radiation.
A-4
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APPENDIX B
Risks To Health From Radiation Doses
That May Result From
Nuclear Incidents
-------
Contents
Page
B.I Introduction B-l
B.I.I Units of Dose B-l
B.I.2 Principles for Establishing Protective Action Guides. B-3
B.2 Acute Effects B-4
B.2.1 Review of Acute Effects B-4
8.2.1.1 The Median Dose for Lethality B-6
B.2.1.2 Variation of Response for Lethality .... B-7
B.2.1.3 Estimated Lethality vs Dose for Man .... B-10
B.2.1.4 Threshold Dose Levels for Acute Effects . . 8-14
B.2.1.5 Acute Effects in the Thyroid B-16
B.2.1.6 Acute Effects in the Skin B-17
B.2.1.7 Clinical Pathophysiological Effects .... B-17
B.2.2 Summary and Conclusions Regarding Acute Effects . . . B-22
B.3 Mental Retardation B-22
B.4 Delayed Health Effects B-24
B.4.1 Cancer B-24
B.4.1.1 Thyroid B-27
B.4.1.2 Skin B-28
B.4.1.3 Fetus B-28
B.4.1.4 Age Dependence of Doses B-29
B.4.2 Genetic Risk B-30
B.4.3 Summary of Risks of Delayed Effects B-31
B.4.4 Risks Associated with Other Radiation Standards . . . B-31
References B-33
Figures
B-l Acute Health Effects as a Function of Whole Body Dose .... B-12
-------
Contents (continued)
Page
Tables
B-l Radiation Doses Causing Acute Injury to Organs B-18
B-2 Acute Radiation Exposure as a Function of Rad
Equivalent Therapy Units (rets) B-19
B-3 Radiation Exposure to Organs Estimated to Cause Clinical
Pathophysiological Effects Within 5 Years to 0.1 Percent
of the Exposed Population B-20
B-4 Average Risk of Delayed Health Effects in a Population . . . B-31
-------
APPENDIX B
Risks To Health From Radiation Doses
That May Result From
Nuclear Incidents
B.I Introduction
This appendix reviews the risks from radiation that form the basis
for the choice of Protective Action Guides (PAGs) for the response to a
nuclear incident, as well as the choice of limits for occupational
exposure during a nuclear incident.
B.I.I Units of Dose
The objective of protective action is to reduce the risk to health
from exposure to radiation. Ideally, one would like to assure the same
level of protection for each member of the population. However,
protective actions cannot take into account individual variations in
radiosensitivity, since these are not known. Therefore, these PAGs are
based on assumed average values of risk. We further assume that these
risks are proportional to the dose, for any level of dose below the
threshold for acute effects (see Section B.2.).
The dose from exposure to radioactive materials may be delivered
during the period of environmental exposure only (e.g., external gamma
radiation), or over a longer period (e.g., inhaled radionuclides which
deposit in body organs). In the latter case, dose is delivered not only
at the time of intake from the environment, but continues until all of
the radioactive material has decayed or is eliminated from the body.
Because of the variable time over which such doses may be delivered, the
PAGs are expressed in terms of a quantity called the "committed dose."
Conceptually, committed dose is the dose delivered over an individual's
remaining lifetime following an intake of radioactive material. However,
due to differences in physiology and remaining years of life, the
B-l
-------
committed dose to a child from internal radioactivity may differ from that
to an adult. For simplicity, adult physiology and a remaining lifetime of
50 years are assumed for the purpose of calculating committed doses.
Another important consideration is that different parts of the body
are at different risk from the same dose. Since the objective of
protective actions is the reduction of health risk, it is appropriate to
use a quantity called "effective dose." Effective dose is the sum of the
products of the dose to each organ or tissue of the body and a weighting
factor representing the relative risk. These weighting factors (IC-77)
are chosen as the ratio of mortality (from delayed health effects) from
irradiation of particular organs or tissues to the total risk of such
mortality when the whole body is irradiated uniformly at the same dose.
Finally, doses from different types of radiation (e.g. alpha, beta,
gamma, and neutron radiation) have different biological effectiveness.
These differences are customarily accounted for, for purposes of radiation
protection, by multiplicative modifying factors. A dose modified by these
factors is designated the "dose equivalent." The PAGs are therefore
expressed in terms of committed effective dose equivalent. The PAGs are
augmented by limits for a few specific organs (skin and thyroid) which
exhibit special sensitivity. These are expressed in terms of committed
dose equivalent (rem). In the process of developing PAG values, it is
necessary to evaluate the threshold dose levels for acute health effects.
These levels are generally expressed in terms of absorbed dose (rad) to
the whole body from short term (one month or less) exposure. Other units
(Roentgens, rem, and rets) are also used in information cited from various
references. They are all approximately numerically equivalent to rads in
terms of the risk of acute health effects from beta and gamma radiation.
PAGs are intended to apply to all individuals in a population other
than workers performing emergency services. However, there may be
identifiable groups that have different average sensitivity to radiation
or, because of their living situation, will receive higher or lower
B-2
-------
doses. In addition, some groups may be at greater risk from taking a
given protective action. These factors are separately considered, when it
is appropriate, in establishing values for the PAGs.
B.I.2 Principles for Establishing Protective Action Guides
The following four principles provide the basis for establishing
values for Protective Action Guides:
1. Acute effects on health (those that would be observable within
a short period of time and which have a dose threshold below
which they are not likely to occur) should be avoided.
2. The risk of delayed effects on health (primarily cancer and
genetic effects, for which linear nonthreshold relationships to
dose are assumed) should not exceed upper bounds that are
judged to be adequately protective of public health, under
emergency conditions, and are reasonably achievable.
3. PAGs should not be higher than justified on the basis of
optimization of cost and the collective risk of effects on
health. That is, any reduction of risk to public health
achievable at acceptable cost should be carried out.
4. Regardless of the above principles, the risk to health from a
protective action should not itself exceed the risk to health
from the dose that would be avoided.
With the exception of the second, these principles are similar to
those set forth by the International Commission on Radiological Protection
(IC-84b) as the basis for establishing intervention levels for nuclear
accidents. We examine, below, the basis for estimating effects on health
for use in applying the first two of these principles.
B-3
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8.2 Acute Effects
This section provides information relevant to the first principle:
avoidance of acute effects on health from radiation.
Acute radiation health effects are those clinically observable
effects on health which are manifested within two or three months after
exposure. Their severity depends on the amount of radiation dose that is
received. Acute effects do not occur unless the dose is relatively large,
and there is generally a level of dose (i.e., threshold) below which an
effect is not expected to occur. Acute effects may be classified as
severe or nonsevere clinical pathophysiological effects. Severe
pathophysiological effects are those which have clinically observable
symptoms and may lead to serious disease and death. Other patho-
physiological effects, such as hematologic deficiencies, temporary
infertility, and chromosome changes, are not considered to be severe, but
may be detrimental in varying degrees. Some pathophysiological effects,
such as erythema, nonmalignant skin damage, loss of appetite, nausea,
fatigue, and diarrhea, when associated with whole body gamma or neutron
exposure, are prodromal (forewarning of more serious pathophysiological
effects, including death).
B.2.1 Review of Acute Effects
This section summarizes the results of a literature survey of
reports of acute effects from short-term (arbitrarily taken as received in
one month or less) radiation exposure in some detail. Many reports of
observed effects at lower doses differ, and some are contradictory;
however, most have been included for the sake of completeness. The
results of the detailed review described in this Section are summarized in
Section B.2.2.
The biological response to the rapid delivery of large radiation
doses to man has been studied since the end of World Mar II. Dose-
response relationships for prodromal (forewarning) symptoms (ED ) and
B-4
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for death within 60 days (LD ,gQ), where x is the probability (in
percent) of response, have been developed from data on the Japanese A-bomb
survivors, Marshall Island natives exposed to fallout, and patients
undergoing radiotherapy. This work has been supplemented by a number of
animal studies under controlled conditions.
The animal studies, usually using lethality as the end point, show
that many factors can influence the degree of response. The rate at which
the dose is delivered can affect the median lethal dose (LD50) in many
species, particularly at dose rates less than 5 R/min (PA-68a; BA-68).
However, in primates there is less than a 50 percent increase in the
LDgQ as dose rates are decreased from 50 R/min to about 0.01 R/min
(PA-68a). There is good evidence of species specificity (PA-68a; BO-69).
The LDr0 ranges from about 100 rad for burros to over 1000 rad for
lagomorphs (e.g., rabbits). Response is modulated by: age (CA-68), extent
of shielding (partial body irradiation) (BO-65), radiation quality
(PA-68a; BO-69), diet, and state of health (CA-68).
While animal studies provide support and supplemental information,
they cannot be used to infer the response for man. This lack of
comparability of man and animals had already been noted by a review
committee for the National Academy of Sciences as early as 1956, in
considering the length of time over which acute effects might be
expressed (NA-56): "Tnus, an LD 30-day consideration is inadequate
to characterize the acute lethal dose response of man, and an LDKn,
i w
60 days would be preferable."
Several estimates of the levels at which acute effects of radiation
occur in man have been published. For example, an early estimate of the
committee (known as the BEAR Committee) also noted "The reservation
must be made here that the exposed Japanese population was heterogeneous
with respect to age, sex, physical condition and degree of added trauma
from burns or blast. The extent to which these factors affected the
survival time has not been determined. In studies on laboratory animals
the converse is true—homogeneous populations are studied" (NA-56, p.1-6),
B-5
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dose-response curves for prodromal (forewarning) symptoms and for
lethality was made in the first edition of "The Effects of Nuclear
Weapons" (1957) (GL-57), and a more recent and well documented estimate is
given in a NASA publication, "Radiobiological Factors in Manned Space
Flight" (LA-67).
B.2.1.1 The Median Dose for Lethality
The radiation dose that would cause 50 percent mortality in 60 days
was estimated as 450 Roentgens in early reports (NA-56; GL-57; RD-51). The
National Commission on Radiation Protection and Measurements (NCRP)
calculated that this would correspond to a midline absorbed dose of 315
rad (NC-74). The ratio of 315 rad to 450 Roentgens is 0.70, which is
about the estimated ratio of the active marrow dose, in rads, to the
tissue kerma in air, in rads (KE-80). The BEAR Committee noted that the
customary reference to LD5Q in animal studies, as if it were a specific
property, independent of age, was not justifiable (NA-56): "...it is
evident, now, that the susceptibility of a whole population is not
describable by a single LD,.-. The published values are usually obtained
for young adults and are therefore maximal or nearly maximal for the
strain. In attempts to estimate LD5Q in man, this age dependence should
be taken into consideration" (NA-56, pp.4-5). They observed that the
LDrQ approximately doubled as rats went from neonates to young adults
and then decreased as the animals aged further. Finally, the BEAR
Committee concluded: "The situation is complex, and it became evident that
it is not possible to extrapolate with confidence from one condition of
radiation exposure to another, or from animal data to man"
(NA-56, p.1-8). Nevertheless, results from animal studies can aid in
interpreting the human data that are available.
The NCRP suggested the LD™,™ might be 10 to 20 percent lower for
the old, very young, or sick, and somewhat greater for healthy adults of
intermediate age (RD-51). Other estimates of adult LD,-0,gn have ranged
from about 300 rad to 243 ^ 22 rad. These lower estimates are apparently
based on a ratio of air to tissue dose similar to those calculated for
midline organs in the body; 0.54 to 0.66 (KE-80; OB-76; KO-81).
B-6
-------
A NASA panel examined all patient and accident studies, tried to
remove confounding factors, and concluded, "On this basis, it may be
assumed that the LD5Q value of 286 rad obtained by a normal fit to the
patient data is the preferred value for healthy man" (LA-67).
An LDcn.,n of 286 + 25 rad (standard deviation) midline absorbed
oU/oU —
dose and an absorbed dose/air dose ratio of 0.66, suggested by the
National Academy of Science (LA-67), is probably a reasonable value for
healthy males. In the absence of more complete information, we assume
that a value of 300 rad + 30 rad is a reasonable reflection of current
uncertainties for average members of the population.
8.2.1.2 Variation of Response for Lethality
Uncertainty in the dose-response function for acute effects has been
expressed in various ways. The slope of the estimated dose-response
function has most commonly been estimated on the basis of the percent
difference in the LD5Q and the LD,,- g or LDg4 , (one standard
deviation from the LDVnK as was done by NASA (GL-57). These and other
parameters derived in a similar manner describe the uncertainty in the
central risk estimate for the dose-response function.
Another means is to use an estimate of upper and lower bounds for the
central risk estimate, e.g., the 95 percent fiducial limits. At any given
response point on the dose-response function, for example, the LD,-, the
dose causing that response has a 95 percent probability of lying between
the lower and upper bounds of the 95 percent fiducial limit for that
point. To estimate this value, probit analyses were run for each species
using data in published reports (KO-81; TA-71). This provided estimates
for each species for comparability analyses. The 95 percent fiducial
limits at the LD5Q response for LDcn/oQ studies averaged ^9 percent
(range -9 to +26 percent) and for LD5Q,60 studies ^17 percent (range -20
B-7
-------
to +45 percent). At the LD,5 response, values were +_16 percent (range
-12 to +50 percent) for LD15/-0 data and +26 percent (range -20 to +65
percent) for LD,,-,g0 data. For the LDg5 response, values were +_17
percent (range -36 to +36 percent) for the LD85/30 data and +24 percent
(range -46 to +31 percent) for LD85,go data.
The differences in the magnitude of the fiducial limits are a
function of the differences in age, sex, radiation quality, degree of
homogeneity of the experimental animals, husbandry, and other factors.
The estimates show that the fiducial limits, expressed as a percent of the
dose at any response, get greater the farther from the LD™ the estimate
is made. For the purpose of estimating fiducial limits for humans, the 95
percent fiducial limits will be considered to be LD,,. +15 percent,
LDcQ +10 percent, and LDgr +JL5 percent. Beyond these response levels,
the fiducial limits are too uncertain and should not be used.
If the median lethal dose, LDcn,,nt is taken as 300 +30 rad midline
DU/oU —
absorbed dose, the response to higher and lower doses depends on the
degree of biological variation in the exposed population. The NASA panel
decided the wide variation in the sensitivity of patients was a reflection
of the heterogeneity of the sample; and that the variation in sensitivity,
the slope of the central estimate of the response function, would be
stated in the form of one standard deviation calculated as 58 percent of
the LOcn- They further decided the deviation in the patients (58
percent) was too great, and the standard deviation for "normal" man should
be closer to that of dogs and monkeys (18 percent) (LA-67). (The
rationale for selecting these species was not given.)
Jones attempted to evaluate the hematologic syndrome from mammalian
lethality studies using the ratio of dose to LD5Q dose as an indicator
of the steepness of the slope of the dose-response function (JO-81).
However, he evaluated LD™ studies only of species having a rather steep
slope, i.e., dogs, monkeys, mice, and swine. He also looked at several
different statistical models for dose-response functions and pointed out
the problems caused by different models and assumptions, particularly in
B-8
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evaluating the tails of the dose-response function (less than LD1Q and
greater than LDgo). Jones recommended using a log-log model, which he
felt provided a better fit at low doses (JO-81).
Scott and Hahn also evaluated acute effects from mammalian lethality,
but suggested using a Weibull model (SC-80). One of the advantages of the
Weibull model is that in addition to developing the dose-response function,
it can also be used to develop hazard functions. These hazard functions,
if developed using the same model, can be summed to find the joint hazard
of several different types of exposure (SC-83). This would allow esti-
mation of the total hazard from multiple organ exposures to different
types of radiation.
As mentioned earlier, the human median lethal dose is commonly
reported in terms of the LDcn/Kn' Most laboratory animal median lethal
doses are reported in terms of the LD50,-0. In those cases where
estimates of both Lticn,->n and LD™,,.,. are available, i.e., the burro
oU/JU bU/ou
(ST-69), the variation (that is, the slope of the dose-response curve) is
greater in the LD5(,,60 study than in the LDcQ/3Q study. Both the dog
and the monkey data are for LD™,™, and so are not appropriate for
direct comparison to man.
If an estimate of the deviation is made for data from other studies
and species, those where most of the fatalities occur within 30 days (like
dogs and monkeys) have standard deviations of from around 20 percent
[swine (x-ray) (ST-69), dogs (NA-66), hamsters (AI-65), primates (Macaca)
(DA-65)] to 30 percent [swine (60Co) (HO-68)]. Those in which most
deaths occur in 60 days, like man, have deviations from around 20 percent
[sheep (CH-64)] to 40 percent [goats (PA-68b), burros (TA-71)]. Nachtwey,
ejt a_L (NA-66) suggested the steepness of the slope of the exposure
response curve depends on the inherent variability of the subjects exposed
and any variation induced by uncontrolled factors, e.g., temperature,
diurnal rhythm, and state of stimulation or arousal. So, while the slope
of the response curve for the patients studied by the NASA panel may be
unrealistically shallow for normal human populations, there is no reason
to think it should be as steep as those for dogs and monkeys.
B-9
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The average deviation for those species (burros, sheep, and goats)
for which the standard deviation of the lDcnicn is available has been
bU/bU
used as an estimator for man. The mean value is 34 ^ 13 percent. This is
only slightly greater than the average value for all physically large
animals (swine, burros, sheep, and goats), 32 + 12 percent.
B.2.1.3 Estimated Lethality vs Dose for Man
As noted in Section B.2.1.1, dose-response estimates vary for a
number of reasons. Some factors affecting estimates for humans are:
1. Age:
Studies on rats indicate the 1050 is minimal for perinatal
exposure, rises to maximum around puberty, and then decreases
again with increasing age (CA-68). The perinatal 1059 is about
one-third of that for the healthy young adult rats; that for the
geriatric rat is about one-half of that for the young adult rat.
2. Sex:
Females are slightly more sensitive than males in most species
(CA-68).
3. Health:
Animals in poor health are usually more sensitive than healthy
animals (CA-68), unless elevated hematopoietic activity is
occurring in healthy animals (SU-69).
While these and other factors will affect the LD5Q/60 and the
response curve for man, there are no numerical data available.
The variation in response at a given dose level increases as the
population at risk becomes more heterogeneous and as the length of time
over which mortality is expressed increases. In general, larger species
show greater variance and longer periods of expression than do small
mammals, e.g., rodents. It is likely that the human population would show
at least the same amount of variation as do the larger animals, i.e., a
coefficient of variation of about one-third.
B-10
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The degree of variation exhibited in animal studies follows a
Gaussian distribution as well as or better than a log normal distribution
over that range of mortality where there are reasonable statistics. We
have assumed here that the functional form of human response is
Gaussian. Generally, sample sizes for extreme values (the upper and
lower tails of the distribution) are too small to give meaningful
results. Therefore, we have not projected risks for doses more than two
standard deviations from the LD50,6Q. Ue recognize that estimates of
acute effects may not be reliable even beyond one standard deviation for a
population containing persons of all ages and states of health. However,
in spite of these uncertainties, previous estimates have been made of the
acute effects caused by total body exposure to ionizing radiation as a
function of the magnitude of the exposure (NC-71; LU-68; FA-73; NA-73).
Given the large uncertainties in the available data, a median lethal
dose value of about 300 rad at the midline, with a standard deviation of
100 rad, may be assumed for planning purposes. Such risk estimates should
be assumed to apply only in the interval from 5 percent to 95 percent
fatality, as shown in Figure B-l. (See also section B.2.1.4.)
Figure B-l is based on the following values:
Dose (rad) Percent fatalities
<140 none^
140 5
200 15
300 50
400 85
460 95
For moderately severe prodromal (forewarning) effects, we
believe the dose at which the same percentage of exposed would show
effects would be approximately half of that causing fatality. This
yields the following results (see also Figure B-l):
2The risk of fatality below 140 rad is not necessarily zero; rather, it
is indeterminate and likely to remain so. This also applies to prodromal
effects below 50 rad.
B-ll
-------
100
10
100 200 300 400 500
WHOLE BODY ABSORBED DOSE (rad)
600
FIGURE B-1. ACUTE HEALTH EFFECTS AS A FUNCTION
OF WHOLE BODY DOSE.
B-12
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Dose (rad) Percent affected
50 <2
100 15
150 50
200 85
250 98
Although some incidence of prodromal effects has been observed at
doses in the range of 15 to 20 rads in patients (LU-68) and in the 0 to
10 rads range of dose in Japanese A-bomb survivors (SU-80a; GI-84), there
is great uncertainty in interpreting the data. Patients may be abnormally
sensitive, so that the dose-response function in patients may represent
the lower bound of doses that would show a response in a healthy
population (LU-67). The response of Japanese survivors in the low dose
ranges is complicated by the blast and thermal exposure that occurred at
the same time (SU-80b). For these reasons, care should be taken in
applying estimates of prodromal effects. The prodomal dose-response
function listed above is more likely to overestimate the proportion of
persons affected than to underestimate it.
These estimated ranges and effects are in agreement with estimates
made for manned space flights (LA-67; LU-67), which included consideration
of the effect of abnormal physiology or sickness in the patients to which
the data apply. Uncertainty in estimates of the biological effects of
radiation exposure is great. It is probably due in part to variation in
the health of individuals in exposed populations. These estimates assume
a healthy young adult population and may not be a conservative estimate of
risk for other population groups, such as children or the elderly.
Lushbaugh, et a]_. (LU-68) found that prodromal effects probably occur in
both healthy and ill persons in about the same dose range. However,
Lushbaugh, et a\_. (LU-68) and NATO (NA-73) suggest that acute mortality in
a population which is ill, injured, or in other ways debilitated will
occur in 50 percent of that population at doses of 200-250 rad in about 60
days (LDcn,cn), in contrast to an LD,.-.,. from doses of 220-310 rad
bU/bU bU/bU
for a healthy young adult population. Thus, the ill or injured are
assumed to have an increased risk of acute mortality at high doses.
B-13
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The above estimates for LD50/fin are also based on the assumption of
minimal medical care following exposure. UNSCEAR (UN-88) estimates that
the threshold for mortality would be about 50 percent higher in the
presence of more intense medical care.
B.2.1.4 Threshold Dose Levels for Acute Effects
This section summarizes information available in the literature
regarding thresholds for health effects. It also reviews actions that
have been taken as a result of radiation exposure to provide insight on
dose levels at which actions to avoid dose may be appropriate.
Some acute effects, such as cellular changes, may occur at low doses
with no dose threshold. Most such effects have a minimum threshold of
detectability; for example, five rad is about the lower limit of whole
body dose which causes a cellular effect detectable by chromosome or other
special analyses (NC-71; FA-73). This value is recommended by UNSCEAR as
the starting point for biological dosimetry (UN-69). Purrott, et a\_. have
reported a lower limit of detection of chromosome aberrations of 4 rad for
x-rays and 10 rad for gamma rays (PU-75).
More recent advanced chromosome banding techniques permit detection
of increased incidence of chromosome abnormalities from continuous
exposure to systematically deposited radioisotopes or radioisotopes
deposited in the lung at very low levels, e.g., body burdens of 100 to
1200 pCi of plutonium-239 (BR-77). While the exact dose associated with
such burdens is not known, it is probably on the order of 10 to 100
millirem per year. Lymphocytes exposed to 5 rem in vitro show severe
metabolic dysfunction and interphase cell death (ST-64). The extent to
which similar effects occur after in vivo exposure is unknown. While
chromosome abnormalities in circulating lymphocytes are reported to
persist for long periods (UN-69), the significance of such abnormalities
is not known (BR-77).
Hug has suggested 5 rem as the lower limit of exposure which might
produce acute effects (WH-65). Five rad is also in the low dose, short-
B-14
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term exposure range defined by Cronkite and Haley, and is below the 10 rad
which they thought would cause only a slight detectable physiological
effect of unknown clinical significance (CR-71).
Although the ICRP has suggested that annual doses of 15 rad would not
impair the fertility of normal fertile men (IC-69), an acute dose of 15
rad causes "moderate" oligospermia (approximately 70 percent reduction in
sperm count) which lasts for some months (LA-67). Popescu and Lancranjan
reported alterations of spermatogenesis and impaired fertility in men
exposed to from 500 millirad to 3 rad per year for periods varying from 2
to 22 years (PO-75). The shortest exposure period in which abnormal
spermatogenesis was reported was 31 to 41 months (PO-75); at the highest
dose rate reported (3 rad/a), this is a cumulative dose of 8 to 10 rem.
While more study is required, these results suggest the need to restrict
acute doses to below 10 rem to avoid this effect, because a given acute
dose is anticipated to be more effective than the same cumulative dose
given over a longer period of time (NA-56; UN-58).
Many observations have indicated that doses of 10 rem or more to the
pregnant woman are hazardous to the fetus. Mental retardation due to
exposure of the fetus is discussed in Section B.3; this discussion is
restricted to acute effects. The World Health Organization (WHO)
indicates that there is no evidence of teratogenic effects from short term
exposure of the fetus to a dose less than 10 rad during the early phase of
gestation, the period when the fetus is most sensitive to these
effects (WH-84).
A number of authorities have recommended that exposures of 10
roentgens or higher be considered as an indication for carrying out
induced abortion (HA-59, DE-70, BR-72, NE-76). Brent and Gorson also
suggest that 10 rad is a "practical" threshold for induction of fetal
abnormalities (BR-72). The Swedish Government Committee on Urban Siting
of Nuclear Power Stations stated the situation as follows: "What we have
called unconditional indication of abortion involves the exposure of
pregnant women where radiation dose to the fetus is higher than 10 rad.
B-15
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When such doses are received In connection with medical treatment, it has
hitherto been assumed that the probability of damage to the fetus is so
high that an abortion is recommended. The probability for such injury is
still moderate compared with the normal frequency of similar fetal
injuries, and the probability is particularly reduced when the dose is
received late in the pregnancy" (NA-74).
B.2.1.5 Acute Effects in the Thyroid
Acute effects are produced in the thyroid by doses from radioiodine
on the order of 3,000 to 100,000 rad. Ablation of the thyroid requires
doses of 100,000 rad (BE-68). The thyroid can be rendered hypothyroid by
doses of about 3,000 to 10,000 rad (IC-71). A thyroid dose from
radioiodines of 1000 rad in adults and 400 rad in children implies an
associated whole body dose of about 1 rad due to radioiodines circulating
131
in the blood. Following inhalation of I, the committed thyroid dose
131
is about one rad/yCi intake of I in adults. In the developing fetus,
131
the thyroid dose ranges from one to six rad per yCi of I entering the
mother's body (IL-74).
Although acute clinical effects are only observed at high doses,
subclinical acute thyroid radiation effects may occur at lower doses
(DO-72). Impaired thyroid capability may occur above a threshold of about
200 rad (DO-72).
Effects of radiation exposure of the thyroid have been shown in
animal experiments. Walinder and Sjoden found that doses in excess of
3,000 rad from I caused noticeable depression of fetal and juvenile
mouse thyroid development (WA-69). Moore and Calvin, working with the
Chinese hamster, showed that an exposure as low as 10 roentgens (x-rays)
would give rise to 3 percent aberrant cells when the thyroid was cultured
(MO-68). While the direct relationship of these results to human effects
is not certain, mammalian thyroid cells can be injured at exposures as low
as 10 roentgens.
B-16
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B.2.1.6 Acute Effects in the Skin
The first stage of skin reaction to radiation exposure is erythema
(reddening) with a threshold of from 300 to 800 rad. Acute exudative
radiodermatitis results from doses of 1,200 to 2,000 rad (WH-84).
B.2.1.7 Clinical Pathophysiological Effects
A large amount of anecdotal information is available on the injury of
organ tissues by high doses of radiation. Acute injury to tissue includes
swelling and vacuolation of the cells which make up the blood vessels,
increased permeability of vessels to fluids so that exudates form,
formation of fibrin clots and thrombi, fibrinoid thickening in the walls
of blood vessels, and swelling and vacuolization of parenchymal cells.
In summary, there is an initial exudative reaction followed in time by
fibrosis and sclerosis (WH-76, CA-76).
Estimates of radiation doses necessary to cause severe tissue
response in various organs are given in Table B-l. These tissue dose
estimates are based on response to radiotherapy treatment, which is
normally given on a fractionated dose basis, but also may be given as a
continuous exposure. Therefore, these estimates must be adjusted to the
equivalent single radiation dose for use in the present analysis. The
formalism of Kirk, et ajk (KI-71) is used to estimate the equivalent dose
for a single acute exposure in rad-equivalent therapy units (rets: the
dose calculated from the fractionated exposure which is equivalent to a
single acute exposure for a specific biological endpoint.) Table B-2
lists acute exposure equivalents in rets for various organs.
With the exception of bone marrow, the exposures required to cause
5 percent injury within 5 years (TD 5/5) in internal organs are in the
range of 1,000 to 5,000 rad. Since, with this type of injury, the dose
response is nonlinear and has a threshold (i.e., is nonstochastic), there
is an exposure below which injury is not expected. If the shape of the
injury dose-response curve is the same for all internal organs as it is
B-17
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Table B-l Radiation Doses Causing Acute Injury to Organs (RU-72, RU-73)
Organ
Bone marrow
Liver
Stomach
Intestine
Lung
Kidney
Brain
Spinal cord
Heart
Skin
Fetus
Lens of eye
Ovary
Testes
Volume or
area of
exposure3
whole
segment
whole
100 cm2
400 cm2
100 cm2
whole
100 cm2
whole
whole
10 cm
60 percent
—
whole
whole
whole
whole
Risk of injury
5 percent
(rad)
250
3000
2500
4500
4500
5000
1500
3000
2000
6000
4500
4500
5500
200
500
200-300
500-1500
in five years
50 percent
(rad)
450
4000
4000
5500
5500
6500
2500
3500
2500
7000
5500
5500
7000
400
1200
625-1200
2000
Type of injury
aplasia and
pancytopenia
acute and chronic
hepatitis
ulcer, perforation,
hemorrhage
ulcer, perforation,
hemorrhage
acute and chronic
pneumonitis
acute and chronic
nephrosclerosis
infarction,
necrosis
infarction,
necrosis
pericarditis and
pancarditis
ulcers, fibrosis
death
cataracts
permanent
sterilization
permanent
sterilization
aDose delivered in 200-rad fractions, 5 fractions/week.
— Unspecified.
B-18
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Table B-2 Acute Radiation Exposure as a Function of Rad Equivalent
Therapy Units (rets)
Organ
Bone marrow
Liver
Stomach
Intestine
Lung
Kidney
Brain
Spinal cord
Heart
Skin
Fetus
Lens of eye
Ovary
Testes
Volume or
area of
exposure
whole
segment
whole
100 cm2
400 cm2
100 cm2
whole
100 cm2
75 percent
whole
whole
10 cm
60 percent
—
whole
whole
whole
whole
(sterilization)
Risk of injury
5 percent
(rets)
230
1135
1000
1465
1465
1570
720
1135
770b
875
1770
1465
1465
1665
200
355
200-430a
340-7203
in five years
50 percent
(rets)
340
1360
1360
1665
1665
1855
1000
1245
1000
1950
1665
1665
1950
315
620
410-875*
410-875*
aFor a 200-rad/treatment, 5 treatments/week schedule (LU-76),
Reference WA-73.
— Unspecified.
B-19
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for the lung, plotting the two acute exposure equivalents (TD 50/5 and
5/5) for each organ on log probability paper allows a crude estimation of
the number of clinical pathophysiological effects per 1000 persons exposed
as a function of dose level. If one acute effect per 1000 persons within
5 years (TD 0.1/5) is taken as the threshold for the initiation of
clinical pathophysiological effects in organs other than thyroid, the
equivalent dose level for most organs is 550 rets or more; testes 440 ^
150 rets, ovary 170 + 70 rets, and bone marrow 165 rets.
The radiation exposure to organs in rad units that will cause
clinical pathophysiological effects within 5 years to 0.1 percent of the
exposed population as a function of the duration of a continuous level of
exposure can then be estimated by using Goitein's modification of the Kirk
methodology (60-76). This relationship is shown in Table B-3.
Table B-3 Radiation Exposure to Organs Estimated to Cause Clinical
Pathophysiological Effects within 5 Years to 0.1 Percent
of the Exposed Population (GO-76)
Duration of
exposure
(days)
(acute)
1
2
4
7
30
365b
Ovary
(rad)
(170 rets)*
315
390
470
550
840
1740
Bone marrow
(rad)
(165 rets)
300
380
450
540
820
1690
Testes
(rad)
(440 rets)
810
1010
1210
1430
2190
4510
Other organs
(rad)
(550 rets)
1020
1260
1510
1790
2740
5640
aThe dose in rets is numerically equal to the dose in rads.
^Assuming tissue recovery can continue at the same rate as observed
during 30- to 60-day therapeutic exposure courses.
Bone marrow is an organ of particular concern because radionuclides
known to concentrate in this organ system occur in nuclear incidents. The
acute lethality due to the hematologic syndrome (LA-67) is estimated to
B-20
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occur in the range of 200 to 1,000 rad, so that the difference is small
between exposure levels that might cause acute lethality and exposure
levels that might cause only "severe clinical pathophysiology," as derived
from radiotherapy data.
In summary, organ systems are not expected to show symptoms of severe
clinical pathophysiology for projected short-term exposure doses less than
a few hundred rad. Projected doses to bone marrow at this high level are
relatively more serious and more likely to result in injury than doses to
other organ systems.
Even if severe clinical pathophysiological effects can be avoided,
there is still a possibility of clinical pathophysiological effects of a
less severe or transitory nature. The 1982 UNSCEAR report (UN-82)
reviewed much of the data on animals and man. In the animal studies,
there were reports of: changes in stomach acid secretion and stomach
emptying at 50 to 130 rad; stunting in growing animals at the rate of 3 to
5 percent per 100 rad; degeneration of some cells or functions in
the brain at 100 rad, particularly in growing animals; temporary changes
in weight of hematopoietic tissues at 40 rad; and more damage in ovaries
and testes caused by fractionated doses rather than acute doses. Some of
the effects are transitory, others are long-lasting, but with only minor
reductions in functional capacity.
Human data are limited and are reported primarily in the radiotherapy
literature. The data suggest most tissues in man are more radiation
resistant than those in animals. However, the human hematopoietic system
shows a transient response, reflected by decreased circulating white cells
and platelets, at about 50 rad. Temporary sterility has been observed
after doses of 150 rad to the ovaries and 10 rad to the testes, when given
as fractionated doses.
There is not sufficient data to determine dose-response functions
nor to describe the duration and severity 'of dysfunction expected.
B-21
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8.2.2 Summary and Conclusions Regarding Acute Effects
Based on the foregoing review of acute health effects and other
biological effects from large doses delivered over short periods of time,
the following whole body doses from acute exposure provide useful
reference levels for decisionmaking for PAGs:
50 rad - Less than 2 percent of the exposed population would be
expected to exhibit prodromal (forewarning) symptoms.
25 rad - Below the dose where prodromal symptoms have been observed.
10 rad - The dose level below which a fetus would not be expected
to suffer teratogenesis (but see Section B.3, Mental
Retardation.).
5 rad - The approximate minimum level of detectability for acute
cellular effects using the most sensitive methods.
Although these are not severe pathophysiological effects,
they may be detrimental.
Based on the first principle to be satisfied by PAGs (paragraph
B.I.6), which calls for avoiding acute health effects, values of 50 rem
for adults and 10 rem for fetuses appear to represent upper bounds.
B.3 Mental Retardation
Brain damage to the unborn is a class of injury reported in atomic
bomb survivors which does not fall into either an acute or delayed effect
category, but exhibits elements of both. What has been observed is a
significant, dose-related increase in the incidence and severity of mental
retardation, microencephaly (small head size), and microcephaly (small
brain size) in Japanese exposed to radiation in utero during the 8th to
15th week after conception (BL-73; MI-76). While the actual injury may be
acute, it is not identified until some time after birth.
B-22
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In an early study Mole (MO-82) suggested that, although radiation
may not be the sole cause of these conditions, it is prudent to treat the
phenomenon as radiation-related. More recently, Otake and Schull (OT-83)
have concluded: (1) there is no risk to live-born due to doses delivered
up to 8 weeks after conception, (2) most damage occurs at the time when
rapid proliferation of neuronal elements occurs, i.e., 8 to 15 weeks of
gestational age, (3) the dose-response function for incidence during this
period appears to fit a linear model, (4) the risk of occurrence is about
five times greater during the period 8-15 weeks of gestation than in
subsequent weeks, and (5) in later stages of gestation, e.g., after the
15th week, a threshold for damage may exist.
In their published reports, Otake and Schull (OT-83) evaluated the
incidence of severe mental retardation using the T-65 dosimetry and the
dosimetry estimates developed in the ongoing dose reassessment program for
the atomic bomb survivors, and using two tissue dose models. Their
estimated ranges of risk were:
8 to 15 weeks after gestation: 3-4xlO~3 cases/rad;
16 or more weeks after gestation: 5-7xlO~4 cases/rad.
The higher values are based on the T-65 dosimetry and the Oak Ridge National
Laboratory estimate of tissue dose. The lower values are based on Oak Ridge
National Laboratory dosimetry and the Japanese National Institute of
Radiological Sciences estimates of tissue dose. Later estimates based on the
dose reassessment completed in 1986 are consistent with these published
results (SC-87).
In view of the foregoing, the risk of mental retardation from exposure
of a fetus in the 8th to 15th week of pregnancy is taken to be about 4xlO~
per rad. Because of this relatively high risk, special consideration should
be given to protection of the fetus during this period. The risk to a fetus
_4
exposed after the 15th week is taken as 6x10 per rad. For the cases
studied (OT-84), no increased incidence of mental retardation was observed
for exposure during the 1st to the 7th week of pregnancy.
B-23
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Federal Radiation Protection Guidance, adopted in 1987, recommends that
dose to occupationally exposed pregnant women be controlled to keep the fetal
dose below 0.5 rem over the entire term of pregnancy, and that no dose be
delivered at more than the uniform monthly rate that would satisfy this limit
(i.e., approximately 50-60 mrem/month)(EP-87). The NCRP has, for many years,
recommended a limit of 0.5 rem (NC-71). ICRP recommends controlling exposure
of the fetus to less than 0.5 rem in the first 2 months to provide
appropriate protection during the essential period of organogenesis (IC-77).
B.4 Delayed Health Effects
This section addresses information relevant to the second principle
(paragraph B.I.5) for establishing PAGs, the risk of delayed health effects
in exposed individuals. The following subsections summarize the estimated
risks of cancer and genetic effects, the two types of delayed effects caused
by exposure to radiation.
B.4.1 Cancer
Because the effects of radiation on human health have been more
extensively studied than the effects of many other environmental pollutants,
it is possible to make numerical estimates of the risk as a result of a
particular dose of radiation. Such estimates, may, however, give an
unwarranted aura of certainty to estimated radiation risks. Compared to the
baseline incidence of cancer and genetic defects, radiogenic cancer and
genetic defects do not occur very frequently. Even in heavily irradiated
populations, the number of cancers and genetic defects resulting from
radiation is known with only limited accuracy. In addition, all members of
existing exposed populations have not been followed for their full lifetimes,
so data on the ultimate numbers of effects is not yet available. Moreover,
when considered in light of information gained from experiments with animals
and from various theories of carcinogenesis and mutagenesis, the observed
data on the effects of human exposure are subject to a number of
interpretations. This, in turn, leads to differing estimates of radiation
risks by individual scientists and expert groups. In summary, the estimation
B-24
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of radiation risks is not a fully mature science and the evaluation of
radiation hazards will continue to change as additional information
becomes available.
Most of the observations of radiation-induced carcinogenesis in
humans are on groups exposed to low-LET radiations. These groups include
the Japanese A-bomb survivors and medical patients treated with x-rays for
ankylosing spondylitis in England from 1935 to 1954 (SM-78). The National
Academy of Science Committee on the Biological Effects of Ionizing
Radiations (6EIR) (NA-80) and UNSCEAR (UN-77) have provided knowledgeable
and exhaustive reviews of these and other data on the carcinogenic effects
of human exposures. The most recent of the BEIR studies was published in
1980 and is here designated BEIR-3 to distinguish it from previous reports
of the BEIR committee.
The most important epidemiological data on radiogenic cancer is that
from the A-bomb survivors. The Japanese A-bomb survivors have been
studied for more than 40 years, and most of them have been followed in a
major, carefully planned and monitored epidemiological survey, the Life
Span Study Sample, since 1950 (KA-82, WA-83). They were exposed to a wide
range of doses and are the largest group that has been studied. They are
virtually the only group providing extensive information on the response
pattern at various levels of exposure to low-LET radiation.
The estimated cancer risk from low-LET, whole body, lifetime exposure
presented here is based on a life table analysis using a linear response
model. We use the arithmetic average of relative and absolute risk
projections (the BEIR-3 L-L model) for solid cancers, and an absolute
risk projection for leukemia and bone cancer (the BEIR-3 L-L model). For
whole body dose, this yields an estimated 280 (with a possible range of
120 to 1200) fatalities per million person-rem for a population cohort
representative of the 1970 U.S. population. We assume this estimate also
applies to high-LET radiation (e.g. alpha emitters); no reduction has been
B-25
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-4 3
applied for dose rate. (The rounded value, 3x10 fatalities per
person-rein, has been selected for this analysis.)
Whole body dose means a uniform dose to every organ in the body. In
practice, such exposure situations seldom occur, particularly for ingested or
inhaled radioactivity. Inhaled radioactive particulate materials may be
either soluble or insoluble. Soluble particulate materials deposited in the
lung will be rapidly absorbed, and the radionuclides associated with them
distributed throughout the body by the bloodstream. As these radionuclides
are transported in the blood, they irradiate the entire body. Usually, they
then redeposit in one or more organs, causing increased irradiation of that
organ. Insoluble particulate materials, on the other hand, are only
partially absorbed into body fluids. (This fraction is typically assumed to
be about 8 percent.) This absorption occurs over a period of years, with a
portion entering the bloodstream and another retained in the pulmonary lymph
nodes. The balance (92 percent) of inhaled insoluble particulate materials
are removed from the lung within a few days by passing up the air passages to
the pharynx where they are swallowed. Inhaled insoluble particulate materials
thus irradiate both the lung and the gastrointestinal tract, with a small
fraction being eventually absorbed into the bloodstream (TG-66). These
nonuniform distributions of dose (and therefore risk) are taken into account
through use of the weighting factors for calculating effective dose.
There is a latent period associated with the onset of radiation-induced
cancers, so the increased risk is not immediately apparent. The increased
risk is assumed to commence 2 to 10 years after the time of exposure and
continue the remainder of the exposed individual's lifespan (NA-80).
^Preliminary reviews of new results from studies of populations exposed
at Hiroshima and Nagasaki indicate that these risk estimates may be
revised upwards significantly in the near future, particularly for acute
exposure situations. EPA has recently used a slightly higher value,
4 x 10~4 fatalities in standards for air emissions under the Clean Air
Act. We will revise these risk estimates to reflect new results following
appropriate review.
B-26
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For uniform exposure of the whole body, about 50 percent of radiation-
induced cancers in women and about 65 percent in men are fatal (NA-80).
Therefore, 1 rem of low-LET radiation would be expected to cause a total
of about 500 cancer cases if delivered to a population of one million.
(In the case of thyroid and skin, the ratio of nonfatal to fatal cancers
are much higher. These are addressed separately below.) This corresponds
to an average annual individual probability of developing cancer of about
7x10" per year. For perspective, the average annual risk of dying of
cancer from all causes in the United States, in 1982, was 1.9x10" .
B.4.1.1 Cancer Risk Due to Radiation Exposure of the Thyroid
Exposure of the thyroid to extremely high levels of radiation may
cause it to degenerate. At moderate levels of exposure some loss of
thyroid function will occur. At lower levels of exposure, there are
delayed health effects, which take the form of both thyroid nodules and
thyroid malignancies (NA-72; NA-80). Doses as low as 14 rad to the
thyroid have been associated with thyroid malignancy in the Marshall
Islanders (CO-70). The increased risk of radiation-induced cancer is
assumed to commence about 10 years after initial exposure and to continue
for the remaining lifespan of an exposed individual.
The true nature of thyroid nodules cannot be established until they
are surgically removed and examined histologically, and those that are
malignant can lead to death if not surgically removed (SA-68; DE-73;
PA-74). Although thyroid malignancies are not necessarily fatal, effects
requiring surgical removal of the thyroid cannot be considered benign. In
this analysis, all thyroid cancers, both fatal and nonfatal, are counted
for the purpose of estimating the severity of thyroid exposures.
Based on findings in BEIR-3, we estimate that 1 rem of thyroid
_4
exposure carries a risk of producing a thyroid cancer of 3.6x10 , of
which a small fraction (on the order of 1 in 10) will be fatal (NA-80).
Since the calculation of effective dose equivalent does not include
consideration of nonfatal thyroid cancers and the severity of the medical
procedures for their cure, it is appropriate to limit the dose to the
B-27
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thyroid by an additional factor beyond that provided by the PAG expressed
in terms of effective dose equivalent. Protective action to limit dose to
thyroid is therefore recommended at a thyroid dose 5 times the numerical
value of the PAG for effective dose.
B.4.1.2 Cancer Risk Due to Radiation Exposure of the Skin
The risk of fatal skin cancer is estimated to be on the order of one
percent of the total risk of fatal cancer for uniform irradiation of the
entire body (IC-78). However, since the weighting scheme for calculating
effective dose equivalent does not include skin, the PAG expressed in
terms of effective dose does not provide protection against radionuclides
which primarily expose skin. As in the case of the thyroid, the ratio of
nonfatal to fatal cancers from irradiation of the skin is high (on the
order of 100 to 1). It would not be appropriate to ignore this high
incidence of nonfatal skin cancers by allowing 100 times as much dose to
the skin as to the whole body. For this reason, evacuation is recommended
at a skin dose 50 times the numerical value of the PAG for effective dose.
B.4.1.3 Cancer Risk Due to Radiation Exposure of the Fetus
The fetus is estimated to be 5 to 10 times as sensitive to radio-
genic cancer as an adult (FA-73; WH-65). Stewart reports increased
relative incidence of childhood cancers following prenatal x-ray doses as
low as 0.20 to 0.25 rem and doubling of childhood cancers between 1-4 rem
(ST-73). She concluded that the fetus is about equally sensitive to
cancer induction in each trimester. Her findings are supported by similar
results reported by MacMahon and Hutchinson (MA-64), Kaplan (KA-58),
Polhemus and Kock (PO-59), MacMahon (MA-63), Ford, et ah (FO-59), Stewart
and Kneale (ST-70b), and an AEC report (AE-61). MacMahon reported that
although there were both positive and negative findings, the combination
of weighted data indicates a 40 percent increase in childhood cancer
mortality after in vivo exposure to diagnostic x rays (1.0 to 5.0 rad):
about 1 cancer per 2,000 exposed children in the first 10 years after
birth (MA-63). He concluded that although the range of dose within which
B-28
-------
these effects are observed is wide, effects will be fewer at 1 rad than at
5 rad.
Graham, et al., investigating diagnostic x-ray exposure, found a
significantly increased relative risk of leukemia in children: by a
factor of 1.6 following preconception irradiation of mothers or in utero
exposure of the fetus; by a factor of 2 following postnatal irradiation of
the children; and by a factor of 2 following preconception irradiation of
the mother and in utero exposure of the child (GR-66).
B.4.1.4 Age Dependence of Doses
Almost all dose models are based on ICRP "Reference Man," which
adopts the characteristics of male and female adults of working age.
ICRP-30 dosimetric models, which use "Reference Man" as a basis, are
therefore appropriate for only adult workers and do not take into account
differences in dose resulting from the differences in physiological
parameters between children and adults, e.g., intake rates, metabolism,
and organ size. Although it is difficult to generalize for all
radionuclides, in some cases these differences tend to counterbalance
each other. For example, the ratio of volume of air breathed per unit
time to lung mass is relatively constant with age, so that the ICRP adult
model for inhaled materials provides a reasonably good estimate of the
dose from a given air concentration of radioactive material throughout
life.
The thyroid is an exception because the very young have a relatively
high uptake of radioiodine into a gland that is much smaller than the
adult thyroid (see Section B.4.2.2.). This results in a larger childhood
dose and an increased risk which persists throughout life. Me have
examined this worst case situation. Age-specific risk coefficients for
fatal thyroid cancer (See Table 6-8 of "Risk Assessment Methodology"
(EP-89)) are about 1.9 higher per unit dose for persons exposed at ages 0
to 9 years than for the general population. Age-dependent dose factors
(see NRPB-R162 (GR-85)) for inhalation of 1-131, are a factor of about 1.7
higher for 10 year olds than for adults. Therefore, the net risk of fatal
B-29
-------
thyroid cancer from a given air concentration of 1-131 is estimated to be
a factor of about 3 higher for young children than for the remainder of
the population. This difference is not considered large enough, given the
uncertainties of exposure estimation for implementing protective actions,
to warrant establishing age-dependent PAGs.
B.4.2 Genetic Risk
An average parental dose of 1 rem before conception has been
estimated to produce 5 to 75 significant genetically-related disorders
per million liveborn offspring (NA-80). For this analysis we use the
geometric mean of this range, i.e. 1.9x10" . This estimate applies to
effects in the first generation only, as a result of dose to parents of
liveborn offspring. The sum of effects over all generations is estimated
-4
to be approximately twelve times greater; that is, 2.3x10 . In
addition, since any radiation dose delivered after a parent's last
conception has no genetic effect, and not all members of the population
become parents, less than half of the entire dose in an average population
is of genetic significance. Taking the above factors into account, we
estimate that the risk of genetically-related disorders in all generations
-4
is 1x10 per person-rem to a typical population.
Although the overall severity of the genetic effects included as
"significant" in the above estimates is not well known, rough judgements
can be made. The 1980 BEIR report referred to " disorders and traits
that cause a serious handicap at some time during lifetime" (NA-80). From
the types of defects reported by Stevenson (ST-59), it can be estimated
that, of all radiation-induced genetic effects, 50 percent lead to minor
to moderate medical problems (i.e., hair or ear anomalies, polydactyl,
strabismus, etc.), 25 percent lead to severe medical problems (i.e.,
congenital cataracts, diabetes insipidus, deaf mutism, etc.), 23 percent
would require extended hospitalization (i.e., mongolism, pernicious
anemia, manic-depressive psychoses, etc.), and 2 percent would die before
age 20 (i.e., anencephalus, hydrocephalus, pancreatic fibrocytic disease,
etc.).
B-30
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B.4.3 Summary of Risks of Delayed Effects
Table B-4 summarizes average lifetime risks of delayed health effects
based on results from the above discussion. Because of the nature of the
dose-effect relationships assumed for delayed health effects from
radiation (linear, nonthreshold), there is no dose value below which no
risk can be assumed to exist.
Table B-4 Average Risk of Delayed Health Effects in a Population3
Fatal cancers
Nonfatal cancers
Genetic disorders
(all generations)
Effects
Whole Body
2.8E-4&
2.4E-4b
l.OE-4
per person-rem
Thyroid0
3.6E-5
3.2E-4
Skin
3.0E-6
3.0E-4
3 Me assume a population with the same age distribution as that of the
U.S. population in 1970.
0 Risk to the fetus is estimated to be 5 to 10 times higher.
c Risk to young children is estimated to be about two to three times
as high.
B.4.4 Risks Associated with Other Radiation Standards
A review of radiation standards for protection of members of the
general population from radiation shows a range of values spanning several
orders of magnitude. This occurs because of the variety of bases (risk,
cost, practicability of implementation, and the situations to which they
apply) that influenced the choice of these standards. Some source-
specific standards are relatively protective, e.g., the EPA standard
limiting exposure of the public from nuclear power operations (25 mrem/y)
from all pathways combined corresponds to a risk (for cancer death) of
A
5x10 for lifetime exposure. Similarly, regulations under the Clean
B-31
-------
Air Act limit the dose due to emissions of radionuclides to air alone from
all DOE and NRC facilities to 0.01 rem per year, which corresponds to a
_4
cancer risk of 2x10 for lifetime exposure. Other guides permit much
higher risks. For example, the level at which the EPA recommends action
to reduce exposure to indoor radon (0.02 working levels) corresponds to a
risk of about 2x10" (for fatal lung cancer) for lifetime exposure. All
of these standards and guides apply to nonemergency situations and were
based on considerations beyond a simple judgement of acceptable risk.
Federal Radiation Protection Guidance for nonemergency situations
recommends that the dose from all sources combined (except from exposure
to medical and natural background radiation) to individuals in the
population not exceed 0.5 rem in a single year (FR-60) and that the dose
to the fetus of occupationally-exposed mothers not exceed 0.5 rem during
the 9-month gestation period (EP-87). This dose corresponds to an annual
incremental risk of fatal cancer to members of the general population of
_4
about 1.4x10 . If exposure of the fetus is limited to one ninth of 0.5
rem per month over a 9-month gestation period, as recommended, the risk of
severe mental retardation in liveborn is limited to about 7x10" .
The International Commission on Radiation Protection recommends that
the dose to members of the public not exceed 0.5 rem per year due to
nonrecurring exposure to all sources of radiation combined, other than
natural sources or beneficial medical uses of radiation (IC-77). They
also recommend a limiting dose to members of the public of 0.1 rem per
year from all such sources combined for chronic (i.e., planned) exposure
(IC-84a). These upper bounds may be taken as representative of acceptable
values for the situations to which they apply. That is, these are upper
bounds of individual risk that are acceptable for the sum of all sources
and exposure pathways under international recommendations, for
circumstances that are justified on the basis of public benefit, and when
actual doses from individual sources are "as low as reasonably achievable"
(ALARA) within these upper bounds.
B-32
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Commission Technical Report, 25-68, 1968.
SC-80 SCOTT, B.R. and HAHN, F.F. A Model That Leads to the Weibull
Distribution Function to Characterize Early Radiation Response
Probabilities. Health Physics 39(1980):521-530.
SC-83 SCOTT, B.R. Theoretical Models for Estimating Dose-Effect
Relationships after Combined Exposure to Cytotoxicants. Bull.
Math. Biol. 45(1983):323-345.
SC-87 SCHULL, W.J., Radiation Affects Research Foundation. Personal
Conversation with Allan C.B. Richardson. EPA Office of Radiation
Programs. June 1987.
SM-78 SMITH, P.G. and DOLL, R. Radiation-Induced Cancers in Patients
with Ankylosing Spondylitis Following a Single Course of X-ray
Treatment, in: Proc. of the IAEA Symposium, Late Biological
Effects of Ionizing Radiation 1, 205-214, International Atomic
Energy Agency, Vienna, March 1978.
ST-59 STEVENSON, A.C. The Load of Hereditary Defects in Human
Populations. Rad. Research Suppl. 1(1959):306-325.
B-38
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ST-64 STEFANI, S. and SCHREK, R. Cytotoxic Effect of 2 and 5 Roentgens
on Human Lymphocytes Irradiated in Vitro. Rad. Research
22(1964):126-129.
ST-69 STILL, E.T. et al. Acute Mortality and Recovery Studies in
Burros Irradiated with 1 MVP X-rays. Rad. Research
39(1969):580-593.
ST-70b STEWART, A. AND KNEALE, 6.W. Radiation Dose Effects in Relation
to Obstetric X-rays and Childhood Cancer. Lancet
1(1970):1185-1188.
ST-73 STEWART, A. An Epidemiologist Takes a Look at Radiation Risks.
DHEW Publication No. (FDA) 73-8024 (BRH/DBE 73-2). Food and Drug
Administration (HHS), Rockville, MD, 1973.
SU-69 SUGAHARA, T. et al. Variations in Radiosensitivity of Mice in
Relation to Their Physiological Conditions, pp. 30-41, in
Comparative Cellular and Species Radiosensitivity. Eds. V.P.
BOND and T. SUGAHARA. The Williams a Wilkins Company, Baltimore,
MD, 1969.
SU-80a SUMMERS, D.L. and SLOSARIK, W.J. Biological Effects of
Initial-Nuclear Radiation Based on the Japanese Data, DNA 5428F.
Defense Nuclear Agency, Washington, DC, 1980.
SU-80b SUMMERS, D.L. Nuclear Casualty Data Summary, DNA 5427F. Defense
Nuclear Agency, Washington, DC, 1980.
TA-71 TAYLOR, J.F., et al. Acute Lethality and Recovery of Goats After
1 MVP X-Irradiation. Rad. Research 45(1971):110-126.
TG-66 TASK GROUP ON LUNG DOSIMETRY (TGLD). Deposition and Retention
Models for Internal Dosimetry of the Human Respiratory Tract.
Health Physics, 12(1966):173-208.
UN-58 UNITED NATIONS. Report of the United Nations Scientific
Committee on the Effects of Atomic Radiation, General Assembly,
Official Records: 13th Session Supp. No. 17(A/3838), United
Nations, NY, 1958.
UN-69 UNITED NATIONS. Radiation-Induced Chromosome Aberrations in
Human Cells, United Nations Scientific Committee on the Effects
of Atomic Radiation Report to the 24th Session. Annex C, Geneva,
pp. 98-142, 1969.
UN-77 UNITED NATIONS. Sources and Effects of Ionizing Radiation.
United Nations Scientific Committee on the Effects of Atomic
Radiation, Report to the General Assembly, with annexes, UN
Publication E.77 IX.1., United Nations, New York, 1977.
B-39
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UN-82 UNITED NATIONS. Ionizing Radiation: Sources and Biological
Effects. United Nations Scientific Committee on the Effects of
Atomic Radiation, 1982 Report tc the General Assembly, with
annexes, United Nations, New York, 1982.
UN-88 UNITED NATIONS. Sources, Effects and Risks of Ionising
Radiation. United Nations Scientific Committee on the Effects of
Atomic Radiation, 1988 Report to the General Assembly, with
annexes, United Nations, New York, 1988.
WA-69 WALINOER, G. and SJODEN, A.M. The Effect of 131I on Thyroid
Growth in Mouse Fetuses: Radiation Biology of the Fetal and
Juvenile Mammal. AEC Symposium Series 17. M.R. Sikov and D.D.
Mahlum, Editors. U.S. Atomic Energy Commission, Oak Ridge, TN,
pp. 365-374, 1969.
WA-73 MARA, W.M. et al. Radiation Pneumonitis: A New Approach to the
Derivation of Time-Dose Factors. Cancer Research
32(1973):547-552.
WA-83 WAKABAYASHI, T. et al. Studies of the Mortality of A-bomb
Survivors, Report 7, Part III, Incidence of Cancer in 1959-78
Based on the Tumor Registry, Nagasaki, Rad. Research
93(1983):112-142.
WH-65 WORLD HEALTH ORGANIZATION. Protection of the Public in the Event
of Radiation Accidents. World Health Organization, Geneva,
p. 123, 1965.
WH-76 WHITE, D.C. The Histopathologic Basis for Functional Decrements
in Late Radiation Injury in Diverse Organs. Cancer Research 37
(Suppl.)1976:2046-2055.
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-principles of public health action. WHO Regional Publications,
European Series No. 16. 1984.
B-40
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APPENDIX C
Protective Action Guides
for the Early Phase:
Supporting Information
(Reserved)
C-l
-------
APPENDIX D*
Background for Protective Action Recommendations:
Accidental Radioactive Contamination of
Food and Animal Feeds**
*This is a new Appendix and is not the one referred to in Chapter 5. The
original Appendix D "Technical Bases for Dose Projection Methods" published
in this manual in 1980 has been deleted and the material incorporated into
the "Accident Assessment" training program conducted by the Federal
Emergency Management Agency.
**This background document concerning food and animal feeds was published by
the Food and Drug Administration in 1982.
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HHS Publication FDA 82-8196
Background for Protective Action
Recommendations: Accidental
Radioactive Contamination of
Food and Animal Feeds
B. Shleien, Pharm.D.
G.D. Schmidt
Office of the Bureau Director
and
R. P. Chiacchierini, Ph.D.
Division of Biological Effects
WHO Collaborating Centers for
• Standardization of Protection
Against Nomonizmg Radiations
• Training and General Tasks in
Radiation Medicine
• Nuclear Medicine
August 1982
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Food and Drug Administration
Bureau of Radiological Health
Rockville. Maryland 20857
-------
FOREWORD
The Bureau of Radiological Health develops and carries out a national program to
control unnecessary human exposure to potentially hazardous ionizing and nonionizing
radiations and to ensure the safe, efficacious use of such radiations. The Bureau publishes
the results of its work in scientific journals and in its own technical reports.
These reports provide a mechanism for disseminating results of Bureau and contractor
projects. They are distributed to Federal, State, and local governments; industry; hos-
pitals; the medical profession; educators; researchers; libraries; professional and trade
organizations; the press; and others. The reports are sold by the Government Printing
Office and/or the National Technical Information Service.
The Bureau also makes its technical reports available to the World Health Organization.
Under a memorandum of agreement between WHO and the Department of Health and
Human Services, three WHO Collaborating Centers have been established within the Bureau
of Radiological Health, FDA:
WHO Collaborating Center for Standardization of Protection Against Nonionizing
Radiations;
WHO Collaborating Center for Training and General Tasks in Radiation Medicine; and
WHO Collaborating Center for Nuclear Medicine.
Please report errors or omissions to the Bureau. Your comments and requests for
further information are also encouraged.
John C. Villforth
'Director
Bureau of Radiological Health
11
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PREFACE
By FEDERAL REGISTER action of March 11, 1982 (*7 FR 10758), the Federal Emer-
gency Management Agency (FEMA) outlined the responsibilities of several Federal agencies
concerning emergency response planning guidance that the agencies should provide to State
and local authorities. This updated a prior notice published in the FEDERAL REGISTER by
the General Services Administration (GSA) on December 2
-------
ABSTRACT
Shleien, B., G.D. Schmidc, and R.P. Chiacchierini. Background for Protecrive Action
Recommendations: Accidental Radioactive Contamination of Food and Animal Feeds. HHS
Publication FDA 82-8196 (August 1982) (pp. 44).
This report provides background material for the development of FDA's
Protective Action Recommendations: Accidental Radioactive Contamination
of Food and Animal Feeds. The rationale, dosimetric and agricultural transport
models for the Protective Action Guides are presented, along with information
on dietary intake. In addition, the document contains a discussion of fie!4
methods of analysis of radionudides deposited on the ground or contained
in milk and herbage. Various protective actions are described and evaluated,
and a cost-effectiveness analysis for the recommendations performed.
The opinions and statements contained in this report may not
necessarily represent the 'views or the stated policy of the World
Health Organization (WHO). The mention of commercial products,
their sources, or their use in connection with material reported
herein is not to be construed as either an actual or implied
endorsement of such products by the Department of Health and
Human Services (HHS) or the World Health Organization.
IV
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CONTENTS
Page
Foreword ii
Preface iii
Abstract iv
Chapter 1. Rationale for Determination of the Protective Action Guides .... 1
1.1 Introduction 1
1.2 Models for Evaluation of Risk 1
1.2.1 Somatic Risk Evaluation 1
1.2.2 Genetic Risk Evaluation 2
1.3 Assessment of Common Societal and Natural Background
Radiation Risks 3
1.3.1 Common Societal Risks 3
1.3.2 Risks from Natural Radiation 4
1.4 Preventive and Emergency PAG's 5
1.4.1 Preventive PAG 6
1.4.2 Emergency PAG 7
1.5 Evaluation of PAG Risks 7
Chapter 2. Oosimetric Models, Agricultural Transport Models,
Dietary Intake, and Calculations . , 8
2.1 Dosimetrie Models 8
2.1.1 Introduction 8
2.1.2 Iodine-131: Dose to Thyroid 8
2.1.3 Cesium-137 and-134: Dose to Whole Body 9
2.1.4 Strontium: Dose to Bone Marrow 10
2.1.5 Other Radionuclides 11
2.2 Agriculture Transport Models , 12
2.2.1 Transport Models 12
2.2.2 Total Intake 13
2.2.3 Peak Concentration 14
2.3 Dietary Intake 14
2.4 Calculations 15
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Page
Chapter 3. Methods of Analyses for Radionuclide Determination 18
3.1 Introduction 18
3.2 Determinations of Radionuclide Concentrations by
Sensitive Laboratory Methods 18
3.3 Determinations of Radionuclide Concentrations by Field Methods .... 19
3.3.1 Ground Contamination (Beta Radiation) 19
3.3.2 Herbage 20
3.3.3 Milk 21
Chapter 4. Protective Actions 26
Chapter 5. Cost Considerations 31
5.1 Cost/Benefit Analysis 31
5.1.1 Introduction 31
5.1.2 Benefit of Avoided Dose 32
5.1.3 Protective Action Costs 32
5.1.4 Population Milk Intake and Dose 33
5.1.5 Milk Concentration for Cost = Benefit 33
5.2 Economic Impact 35
5.3 Cost-Effectiveness Analysis 37
5.4 Summary and Conclusion 38
References 39
VI
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CHAPTER 1. RATIONALE FOR DETERMINATION OF THE
PROTECTIVE ACTION GUIDES
1.1 INTRODUCTION
The process of determining numerical limits for radiation standards is one of risk
assessment. This process, in which risk considerations are an important factor in decision-
making, consists of two elements: determination of the probability that an event will occur,
and determination of "acceptable risk." A recent discussion of acceptable risk defines risk
as a measure of the probability and severity of adverse effects. Safety is the degree to
which risks are judged acceptable (1).
Since initiation of protective action assumes that an accident has occurred, no
attention will be given to the estimation of probabilities for accident occurrence in the
present analysis.
One process of determining "acceptable risk" is to compare estimates of risk associated
with an action with already prevalent or "natural" risks that are accepted by society.
This method of evaluation is employed in the present discussion by comparing the risk
from natural disasters and from the variation in "natural radiation background" to the
radiation risk associated with the numerical limits for the Protective Action Guides (PAG).
"Protective action guide" (PAG) means the projected dose commitment values to
individuals in the general population that warrant protective action following a release of
radioactive material. Protective action would be warranted if the expected individual dose
reduction is not offset by negative social, economic, or health effects. The PAG does not
include the dose that has unavoidably occurred prior to the assessment. "Projected dose
commitment" means the dose commitment that would be received in the future by indi-
viduals in the population group from the contaminating event if no protective action
were taken. The projected dose commitment is expressed in the unit of dose equivalent or
the rem.
The "natural radiation background" consists of contributions from external radiation
and internal deposited radioactivity from ingestion and inhalation. For the most part, the
variation in the internal natural radiation dose is due to the variability of whole-body
potassium-40. Since these PAG's are limited to ingestion, a parameter that describes the
variability of the internal natural radiation dose might appear more appropriate than using
the variability of the external or total natural radiation dose in evaluating the acceptability
of a given level of risk. However, the potassium level in the body (and hence internal dose)
is controlled by metabolic processes and dietary intake has little effect. Hence the risk of
natural disasters, which is dependent on geographical location of residence, is in this
agency's opinion a better measure of acceptable risk.
1.2 MODELS FOR EVALUATION OF RISK
Models for the somatic and genetic effects of radiation are required for comparisons of
radiation risks from the PAG's relative to other naturally occurring risks.
1.2.1 Somatic Risk Evaluation
A review of the current literature indicates that the risk estimates developed in the
National Academy of Science Committee on the Biological Effects of Ionizing Radiation or
the BEIR-I report (2) and the BEIR-HI report (3) are appropriate for use in analysis of
1
-------
somatic risk. Mortality rather than incidence estimates are employed in the comparisons.
In the case of comparisons to natural background radiation, use of mortality data or
incidence estimates would yield the same numerical PAG limits, because these limits are
based on a comparison between risks rather than an evaluation of absolute risk.
The radiation doses in the event of a contaminating accident will most likely result from
ingestion of the fission products cesium-134 and -137; strontium-89 and -90; and iodine-131.
For the purpose of this analysis it is assumed that all projected extra cancers can be
attributed to internal radiation via the food pathway (i.e., the risks from ingested
radioactive material is the same as that fro n external radiation).
The BEIR-III (3) best estimate of lifetime cancer risk (linear quadratic model) for a
single exposure to low-dose, low LET radiation is from 0.77 to 2.26 x 10~* deaths per person-
rem, depending on whether the absolute or relative-risk projection model is used (calculated
from Table 1). The equivalent risk estimate from BEIR-I (2) is 1.17 to 6.21 x 10~* deaths
per person-rem.
Table 1. Risk estimates for single dose
Deaths per million persons per 10
rads single dose whole-body BEIR-III
Dose response model
Linear quadratic
Linear
Quadratic
Absolute risk
766
1671
95
Relative risk
2255
5014
276
These risk estimates are for a single dose of 10 rem, because limitations of the scientific
information do not justify estimates at lower doses according to the BEIR Committee.
Because of the uncertainty of risk estimates at low doses, BEIR-III provided risk estimates
based on a linear model and a pure quadratic dose response model as well as estimates based
on the preferred linear quadratic model. The risk estimates for the linear model are about
a factor of 2 higher and those of the quadratic model^and about a factor of S lower than
those of the linear quadratic model. It should further be noted, that BEIR-III does not
recommend that their risk estimates be extrapolated to lower doses because of the
inadequacies of the scientific basis. BEIR-III does recognize however that Federal agencies
have a need to estimate impacts at lower doses. While BEIR-III prefers the linear-quadratic
dose response model as the best estimate, regulatory agencies have continued to favor the
linear model as the basis for making risk estimates. While the BEIR-III estimates will be
used here to estimate the impact (health effects) at lower doses, it is fully recognized
that current scientific opinion leaves alternatives as to which dose response and risk model
to use.
As previously stated, for the purpose of setting PAG's, comparison of radiation risks to
those from natural disasters is considered the approach of choice in this document.
1.2.2 Genetic Risk Evaluation
The model for genetic risks from radiation exposure is described in the BEIR-III report
(3). In the first generation, it is estimated that 1 rem of parental exposure throughout the
general population will result in an increase of 5 to 75 additional serious genetic disorders
per million liveborn offspring. The precision for estimating genetic risks is less precise than
those for somatic risks. Given the broad range, genetic risks are evaluated, but are not
precise enough to be a basis for setting the PAG's.
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1.3 ASSESSMENT OF COMMON SOCIETAL AND NATURAL BACKGROUND RADIA-
TION RISKS
1.3.1 Common Societal Risks
As previously stated, one m-thod of determining the acceptability of a risk is by
comparing prevalent or normal risks from hazards common to society. A list of the annual
risks from common societal hazards is given in Table 2. Comparision of radiation risks to
commonly accepted societal risks Assumes that the age dependencies are similar and that all
individuals are equally exposed tr the hazard. This latter assumption is, of course, not
entirely valid in that persons nearer a nuclear power plant or a dam, or in an earthquake or
tornado area might be expected to be at greater risk than persons living at a distance from
the particular hazard.
Table 2. Annual risk of death from hazards common to society
Risk of death
Category Reference (per person per year)
All disease
Leukemia and all other cancer
Motor vehicle accidents
Accidental poisoning
Air travel
Tornadoes (Midwest)
Earthquakes (Calif.)
Floods (46 million at risk)
Catastrophic accidents
(tornadoes, floods,
hurricanes, etc.)
Natural disasters
Tornadoes
Hurricanes
Floods
Lightning
Winter storms
(<0
(5)
(6)
(6)
(7)
(8)
(8)
(9)
(10)
(11)
(6)
(7)
(9)
(7)
(9)
(8)
(9)
(7)
(9)
8 x 10-3
1.5 x 10-J
3 x 10-"
1 x 10'5
9 x 10"'
2 x 10-6
2 x 10-'
2.2 x 10-6
1.2 x 10~'
9 x lO'7
8 x Iff1
0.4 x ID'6
0.6 x 10-'
0.* x ID'6
0.3 x 10-'
2 x 10"s
0.5 x 10"'
0.5 x 10-'
0.* x ID'6
Natural disasters (sum of above) 2.1 to 3.9 x 10~6
Table 2 indicates that the annual individual risk from natural disasters is approximately
1 to k x 10"6. This risk represents a common risk level, which is generally not considered
in selecting place of residence. At this level of risk, some action to prevent further loss of
life could be expected by society following the occurrence of a natural disaster. It thus
appears prudent to evaluate the somatic risks from radiation in relation to the risk of death
from a natural disaster. For comparison purposes, a value of 1 in a million (1 x 10'6) annu-
al risk of death, which is often quoted as an acceptable risk, will be used as the risk of
natural disasters. Actual data indicate that the risk of natural disasters may be a 2 or 3
times greater risk than this value. For a risk of death of 1 x 10"' per year, the lifetime
accepted societal risk would be about 70 x 10"6. This is equivalent to a single radiation
dose of 1*0 to 420 mrem, using the linear model, or 310 to 910 mrem using the BEIR-III
linear quadratic model (see Table 1). The upper and lower ranges are those obtained from
employment of relative and absolute risk models and the dose response extrapolations
mentioned above (from calculations based on data in Table 1). Genetic effects are not
considered m evaluating common societal hazards because of the difficulty in assessing
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deaths occurring from genetic consequences, either natural or radiation induced. If sponta-
neous abortions are deleted from mis category, then fatal genetic effects are a small
portion of the overall genetic impact on health. However, it is difficult to accurately
evaluate genetic effects, and even more difficult to compare its impact to the impact of
somatic effects in an effective manner.
1.3.2 Risks From Natural Radiation
Further perspective i»n acceptable risk can be obtained by examining the risks of natural
background radiation. In risk assessments where a radiation risk is compared co that from
the natural radiation background, the question is which variable associated with natural
background should be used to determine "acceptable risk?" Since background radiation has
always been a part of the natural environment, a plausible argument might be to assume
that the risks associated with the average natural radiation dose represent an "acceptable
risk."
It has also been argued that because of the ever present risk from natural radiation, a
level of manmade radiation ought to be acceptable if it is "small" compared to natural
background (12). It has been suggested that "small" be taken as the standard deviation of
the population-weigh ted natural background (13). In previous evaluations that led to the
FDA's proposed PAG recommendations (1*) the geographic variable (two standard
deviations) in the natural radiation dose was used as a point of comparison for judging
acceptable radiation risk (15). This value, calculated on a State-by-State basis assuming a
log-normal distribution and not weighted for population, is 8.5 mrem per year. The
cumulative lifetime dose equivalent would thus be about 500 mrem, which was the basis for
the proposed PAG recommendation for the whole body at the Preventive PAG level. The
Environmental Protection Agency (EPA), in a further analysis of previously published data
(16), has calculated the cumulative distribution of dose equivalent in the U.S. population.
These data show that 95 percent of the population receives between 28 and 84 mrem/year
from cosmic and terrestrial background radiation (17). The actual distribution is
asymmetric and not log-normal. Thus, one-half of this 95-percent increment range, or 28
mrem/year, will be taken as the value for judging acceptable risk. Adler (13) notes that one
standard deviation of the natural external and internal radiation background derived from
earlier sources (18) is 20 mrem. Personal conversations with Adler revealed that this
estimate is based on air exposures rather than dose equivalent (mean whole body) and
involved a broad rounding off of values. At the 95-percent increment value (latest EPA
data) of 28 mrem/year (19), the additional lifetime dose over 70 years is about 2000 mrem.
About 6 million persons (2-1/2 percent of the population) receive lifetime doses that exceed
the mean background radiation dose by this amount or more.
Another possibility, especially applicable to setting limits for internal emitters, is using
che variation in internal natural radiation dose as a reference for establishing an acceptable
standard for PAG's. For PAG limits for radionuclides via the ingestion pathway, doses to
organs other than the lungs are most pertinent. Using this suggestion still requires a
judgmental decision as to whether the variation in internal natural radiation dose is "small."
A summary of internal natural radiation doses is given in Table 3. It is apparent that
natural radiation doses to human tissues and organs is determined mainly by potassium-40
concentration. The average annual internal whole-body radiation dose per person from
ingested natural radioactivity is 19.6 mrem, of which 17 mrem is due to potassium-40.
In potassium-40 whole-body measurements of 10,000 persons, a standard deviation of
about 12 percent (95-percent confidence level of 23.52 percent) was observed (20). The
study further concluded that the standard deviation is also the same for different groups of
age and sex, and therefore, it may be concluded [hat the same biological variation exists for
all the different age-sex groups. In another study based on che chemical determinations of
total body potassium the average amount in a 70-kg man was estimated co be 136 g with a
standard deviation of ± 28 g or ±20 percent (95-percent confidence increment of ± f0
percent) (21).
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Table 3. Annual internal radiation dose per person
for non-inhaled natural radioactivity2
Annual dose (mrads/year) whole-body average
(unless otherwise noted)
H-3
Be-7
C-l*
Na-22
K-*0
Rb-87
U-238-U-23* series
Ra-222
Po-210
Ra-226
Th-230
Th-232
0.001
0.008
1.3
0.02
17
0.4
0.0*3°
0.060°
0.7
0.031°
0.0*°
0.0*°
Total 19.65
DBased on soft tissue dose (lung, testes, and ovaries)
An indirect means of determining the variability of whole-body potassium values is
based on the constant ratio of mean potassium values to cotal body water up to age 50
(20). The 95-percent confidence increment for the variability of total body water in males,
ages 16 co 90 is 16 percent, while for females it is 13 percent for ages 16 to 30 and 21
percent for ages 31 to 90 (22).
From the above data, it appears that the increment for the 95-percent confidence
level for whole-body potassium, and hence potassium-*0, is between ± 15 percent and ± 40
percent. Note that this variability may be due to differences in body water or body weight^
Only in the case of one study (21) is it dear the total body weight is considered a constant.
It is apparent that a range of values between approximately 3 to 7 mrad per year may be
used to describe the variability in natural potassium-40 dose to the population on a whole-
body dosimetric basis. The mid-point of this range is 5 mrad per year or a lifetime dose
commitment (70 years) of 350 mrem.
Thus, the lifetime radiation dose associated with the variability in natural radiation is
about 350 mrem (internal) and 2000 mrem (external).
l.t PREVENTIVE AND EMERGENCY PAG'S
PAG's have been proposed for two levels of response:
1. Preventive PAG - applicable to situations where protective actions causing
minimal impact on che food supply are appropriate. A preventive PAG establishes a level ac
which responsible officials should take protective action to prevent or reduce the
concentration of radioactivity in food or animal feed.
2. Emergency PAG - applicable to incidents where protective actions of great impact
on the food supply are justified because of the projected health hazards. An Emergency
PAG establishes a level at which responsible officials should isolate food containing
radioactivity co prevent its introduction into commerce, and at which the responsible offi-
cials must determine whether condemnation or another disposition is appropriate.
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1.4.1 Preventive PAG
During recent years numerous reports on risks and risk/benefit assessments for the
evaluation of technological insults have been published. A number of these have concluded
that an annual risk of death of 1 in a million is acceptable to the public (8). The total aver-
age annual risk to the U.S. population from natural disasters appears to be about 2 or 3
times greater than the 1 in a million annual risk. Those individuals living in certain flood
plains, tornado, or earthquake areas accept risks that may be greater than the average by a
f act&i of 2 or more (See data for tornadoes and earthquakes in Table 2).
As previously mentioned, based on BE1R-III (3) upper risk estimates, a 1 in a million annu-
al risk of death corresponds to a single radiation dose of 140 co 910 mrem.
It is our conclusion that an annual risk of 1 in a million provides a proper perspective for
setting food protective actions guides (PAG's) for radiation contamination accidents of low
probability. It appears chat most individuals in the United States will never be exposed to
such a radiation contamination accident and that any one individual is not likely to be
potentially exposed more than once in his lifetime.
Based on the above considerations, the uncertainty in radiation risk estimates and the
uncertainty in the average natural disaster risks, a value of 0.5 rem whole body is selected
for the Preventive PAG. Thus, at projected doses of 0.5 rem from contaminated food, it is
recommended that protective actions having low impacts be taken for protection of the
public. The specific value of 0.5 rem represents a judgment decision rather than a specifi-
cally derived value from specific models and assumptions.
Further perspective on acceptable risks for setting the PAG's is the risks associated with
natural background radiation. The discussion above indicates that lifetime dose associated
with the 95-percent increment of the variability in natural radiation is about 350 mrem
internal and 2000 mrem external (that is, 2-1/2 percent of the population receives doses
greater than the average by this amount or more).
This Preventive PAG is applicable to whole-body radiation exposure and to major
portions of the body including active marrow (ingestion of strontium) in conformity with
current U.S. radiation protection practice. Coincidently, 0.5 rem is the Federal Radiation
Council's (FRC) annual limit for individuals of the general population (23).
Present convention, recommended by the Federal Radiation Council (23) based on prior
estimates of relative radiation risks for various organs indicates chat radiation limits for the
thyroid gland be set. at 3 times those for the whole body. More recent scientific information
indicates that the risks from organ doses relative co whole body differ from those assumed
when the current U.S. regulations and FRC guidance were established. The International
Commission on Radiological Protection (ICRP) in revising its recommendations on internal
exposure derived weighting factors that represent the ratio of risk from irradiation to a
given tissue (organ) to the total cancer risk due to uniform irradiation to the whole body.
The ICRP weighting factors are 0.12 for red bone marrow and 0.03 for thyroid, indicating
that the cancer risk is 8 times less for red bone marrow and 33 times less for thyroid than
for whole body exposure (24). Further considerations of effects other than cancer resulted
in che limitation of organ doses to 50 rems per year for occupational workers. Thus the
ICRP recommendations in effect provide for or allow single organ doses that are 8 times
greater for red bone marrow and 10 times greater for thyroid than for whole body. The EPA
has recently proposed Federal guidance for occupational radiation protection that incorpo-
rates che basic ICRP recommendations (46 FR 7836, 3an. 23, 1980). Setting the Preventive
PAG at 0.5 rem for whole body and red bone marrow and 1.5 rem for thyroid provides
significantly more protection from the actual risks of organ doses than from whole-body
risks. To che extent that the whole-body risk is considered acceptable, che red bone marrow
and thyroid limits are conservative by factors of S and 3.3, respectively.
-------
1.*.2 Emergency PAG
The philosophy of the protective action guidance of FDA is that low impact protective
actions should be initiated when contamination of food exceeds the Preventive PAG. The
intent is that such protective actions be implemented to prevent che appearance of
radioactivity in food at levels that would require the condemnation of food. If such actions
are ineffective, or high levels appear in food, then the Emergency PAG is that level at
which higher impact (cost) protective actions are warranted. At the Emergency PAG
radiation level, action should be taken to isolate and prevent the introduction of such food
into commerce and to determine whether condemnation or other disposition is appropriate.
With regard to the numerical relationship between the Preventive PAG level and the
Emergency PAG level, prior conventions may be considered. For example, the Federal
Radiation Council (23) assumed that the dose to the most highly exposed individual does not
vary from the average dose to the whole population by a factor greater than three; Hence, a
factor of 3 was used to define the difference between maximum and average population
limits. Traditionally, it has been more common to use a factor of 10 as a safety factor,
such as between occupational and general public limits. A factor of 10 difference between
the Emergency and Preventive PAG levels, based on these traditional radiation protection
approaches has in the past been thought to introduce a sufficient level of conservatism. The
proposed PAG's (14) adopted this rationale in setting the Emergency PAG's. The analyses of
costs, to follow, also indicate that a factor of 10 between the Preventive PAG and
Emergency PAG is appropriate. As calculated in the last chapter of this report the cost of
condemnation of milk (high impact protective action) is about a factor of 10 greater than
the cost of using uncontaminated stored feed (low impact protective action). Since
contamination of the milk pathway is considered to be the most probable and significant
food problem, this is the only pathway that is cost analyzed.
The use of a factor of 10 adopted here results in an Emergency PAG of 5 rem for the
whole body which numerically is equivalent to the current occupational annual limit. This
limit permitted each year over a working lifetime is associated with the expectation of
minimal increased radiation risks.
1.5 EVALUATION OF PAG RISKS
The risks associated with a radiation dose equal to the PAG's can be readily calculated
from the BEIR-UI risk estimates in Table 1. For the Preventive PAG of 0.5 rem, the deaths
per million persons exposed are one-twentieth of those given for the 10-rad single dose (or
about 38 to 250 deaths for the linear quadratic and linear models respectively). On an
individual basis, this is a risk of death of 0.38 to 2.50 x 10"1 (0.0038 to 0.025 percent)
over a lifetime. BEIR-OI gives the expectation of cancer deaths in the U.S. population
as 167,000 per million or an individual expectation of cancer death of 16.7 percent.
As noted above, the BEIR-UI estimate of serious first generation genetic disorders is 5 to
75 per million live offspring per rem of parental exposure. Thus, for a dose of 0.5 rem, the
expectation is 2.5 to 38 disorders per million live offspring. BEIR-II1 notes the current
estimate of the incidence of serious human disorders of genetic origin as roughly 10 percent
of liveborn offspring.
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CHAPTER 2. DOSIMETRIC MODELS, AGRICULTURAL TRANSPORT MODELS,
DIETARY INTAKE, AND CALCULATIONS
2.1 DOSIMETRIC MODELS
2.1.1 Introduction
The dosimetric models and metabolic parameters for estimating the dose from internally
deposited radionudides are in a state of flux. The recent reports and current activity
represent the first major revision since the adoption of ICRP Publication 2 (25) and NCRP
Report 22 (26) in 1959. ICRP Publication 30 (27) superseded ICRP Publication 2 and revised
the basic approach in setting limits for intake of radionudides by workers. The ICRP recom-
mendations are intended to avoid nonstochastic effects and to limit the occurrence of
stochastic effects to an acceptable level. This approach indudes the use of weighting
factors to sum the risk from organ doses in setting the limits for intakes. This system
contrasts with the earlier approach where limits were based on the dose to the "critical
organ."
The ICRP Publication 30 approach has considerable merit, but is not yet widely accepted
in the United States. Its use in calculating the derived response levels would represent a
major change. Accordingly, the approach is to use the organ to whole-body dose relation-
ship of current U.S. regulations and to select critical organ dose conversion factors that are
based on current dosimetric models and metabolic parameters. Where apropriate, the
recent ICRP and NCRP organ dose models will be accepted as representing current scientif-
ic opinion. It should be noted that future reports and revisions by NCRP, MIRD (Medical
Internal Radiation Dose Committee of The Sodety of Nuclear Medidne) and other Federal
agencies may necessitate a revision of the dose conversion values selected here.
The PAG's are applicable to the most critical or sensitive segment of the population. In
most cases this means that the infant or child is the critical segment. In the case of the
Emergency PAG, derived response levels are also presented for the adults. This permits
greater flexibility in the choice of protective actions in cases where infants are not present
or can be excluded from use of the spedfic food item being considered.
2.1.2 Iodine-131: Dose To Thyroid
Fetal uptake of iodine begins at about the 9th week of gestation and reaches a maximum
in the newborn infant (2S,29) before returning to adult levels. Kereiakes et al. (30) report
that thyroid uptake during the first 2 weeks of life is very high and report a value of 70
percent of that administered for the newborn. The radioiodine uptake expressed per unit
thyroid weight remains high for the newborn and infant and only gradually decreases
throughout childhood and adolescence to adult levels. The newborn infant will be taken as
the most critical segment of the population because factors concerning intake, uptake, and
radiosensitivity indicate that the thyroid gland of an infant receives a higher radiation dose
per unit 1-131 ingested than any other age group (30). However, it is interesting to note that
data indicate that only about 3 percent of infants are given whole cow's milk at 1 month of
age and about 1 percent at 10 days (31). Hence, assuming that all infants are given whole
milk provides a conservative estimate of infant thyroid doses.
Data on the dose to the fetal thyroid from 1-131 ingested by che mother is rather limit-
ed. The study of Dyer and Brill (29) reports an increase in the fetal thyroid dose from 0.7 to
5.9 rads per uCi administered to the mother for fetal ages of 13 to 22 weeks. It thus
-------
appears that the fetal thyroid dose is less than that of the newborn infant ingesting 1-131
contaminated milk.
The current literature on normal thyroid uptake in U.S. adults shows 24-hour jptake has
decreased from about 30 percent reported in the 1960's to about 20 percent or less in cur-
rent comparable studies. Kereiakes et al. (32) use a 20-percent uptake for all ages. This
reduced uptake apparently results from changes in the U.S. diet, whereas [CRP 30 (27) has
continued to use an uptake of 30 percent to reflect world averages.
The Medical Internal Radiation Dose (MIRD) Committee schema (33) has be *n used by
Wellman and Anger (3*) to calculate dose factors per uCi ingested for the newb >rn for the
1-, 5-, 10-, and 15-year-old child, and for the adult. These factors were then modified by
Kereiakes et al. (32) to reflect a 20-percent uptake for all ages. A biological half-life of 68
days is used for all ages, which results in an effective half-life of 7.2 days. Although there
is some evidence that the biological half-life for the infant is less, the radiation dose is
largely controlled by the radiological half-life and use of a single value appears appropriate
here. Because of some uncertainty regarding the fetal thyroid dose and lack of acceptance
by national and international groups, the older data (27-percent uptake) of WelJman and
Anger (34) will be used. This provides some additional conservatism in the derived response
levels for 1-131. The cumulative activity is 2.08 uCi-days per uCi ingested
(administered).
Table 4. Summary of 1-131 dose conversion factors
Age
Newborn
1 yr.
5 yrs.
10 yrs.
15 yrs.
Adult
Thyroid weight (R)
1.5
2.2
4.7
8.0
11.2
16.0
Dose rad/ uCi
16.0
10.9
5.1
3.0
2.1
1.5.
For the infant and adult, the dose conversion factors to be used are 16.0 and 1.5 rad/ yCi
ingested.
2.1.3 Cesium-137 and-134: Dose To Whole Body
The NCRP (35) has reviewed the behavior of Cs-137 in the environment and its metabo-
lism and dose to man. From studies of Cs-137 in food chains, the biological half-life is
found to vary from 15 ±5 days in infants to 100 ±5 days in adults. The biological half-
life in pregnant women is reported to be 1/2 to 2/3 that in nonpregnant women and
consequently the dose to the fetus is also reduced.
Retention of Cs-137 in the adult is stated to be well represented by a 2-exponential
equation with biological half-times of 1.4 days and 135 days applicable to retention in body
fluid and soft tissues, respectively. Integration of this equation yields an accumulated activ-
ity of 170 uCi-days per uCi of intake. This accumulated activity may be expressed in
terms of a single retention function yielding a value of 118 days.
The dosimetry of internally deposited Cs-137 in infants and adults is treated separately
for the beta particle and photon components. The difference between infants and adults is a
smaller photon contribution to the infant because of the smaller body size. For a uniform
concentration of 1 uCi/kg of body weight, the total beta and photon dose rate is 19
mrad/day to the infant and 25 mrad/day to the adult. Use of the above accumulated activ-
ity factor of 170 uCi-days per uCi intake yields a dose of 0.061 rad/ uCi intake for the
adult. Assuming an effective retention time of 20 days for the infant, the corresponding
factor for the infant is 0.071 rad/uCi intake. The use of a smaller effective retention
-------
time (15 days as noted in NCRP (26)) or 10 days as used in NUREG-0172 (36) would reduce
the infant dose conversion factor. The use of 20 days thus tends to overestimate the infant
dose.
It is also important to consider the dose from Cs-134 which, depending on operating
history, occurs in nuclear reactor fuel at levels equal to or greater than that of Cs-137.
Unfortunately, published dosimetry data for Cs-134 for the infant are rather limited.
Conversion factors for the adult that use current models and metabolic data are found in
ORNL/NUREG/TM-190 (37). Johnson et al. (38) have used this same data base to compute
committed effective dose equivalent conversion factors for both infants and adults. The
mean absorbed dose per cumulated activity factor for the infant were modified by the ratio
of adult and infant organ mass (with a further correction co photon component based on
absorbed fraction) to produce the infant factors. It was stated that this procedure may
underestimate the infant dose.
The approach adopted here will be to modify the adult dose conversion factor in
ORNL/NUREG/TM-190 (37) based only on relative body weight and cumulated activity
(effective retention half-times). The dose conversion factor for cesium-134 from
ORNL/NUREG/TM-190 adult whole body is 0.068 rem/uCi ingested and the estimated
factor for the infant is then 0.118 rem/uCi ingested. This value should overestimate the
infant dose and is conservative.
Summary of Cs-134 and Cs-137 Dose Conversion Factors
Table 5. Summary of dose factors for Cs-134 and Cs-137
Infant Adult
Body Mass
Uptake to whole body3
T biological (days)
T effective Cs-134 (days)
Cs-137 (days)
7,700g
1.0
20
19.5
20
70,000g
1.0
118
102
118
Dose conversion (rem/ uCi ingestion)
Cs-134 0.118 0.068
Cs-137 0.071 0.061
dFor cesium-13*, ORNL/NUREG/TM-190 uses uptake of 0.95.
2.1.4 Strontium: Dose To Bone Marrow
The tissues at greatest risk in the skeleton have been identified as the active red marrow
in trabecular bone and endosteal cells near bone surfaces (generally referred to as bone
surface). Spiers and his coworkers (39,40) have developed methods to calculate the absorbed
doses, Dm and Ds, received by red marrow and bone surfaces, respectively from beta-
emitting radionuclides uniformly distributed throughout the volume of bone. They consider
the dose, Do, in a small, tissue-filled cavity in an infinite extent of mineral bone uniformly
contaminated with the radionuclide and give dose factors DS/DO and Dm/Do for obtaining
the absorbed doses. For both Sr-89 and Sr-90, the ratio of Ds/Dm is about 1.5. Therefore,
since che dose limit recommendations are 15 rem to bone and 5 rem to red marrow
(occupational limits), the dose to red marrow is the limiting criterion and will be used in this
report (26).
The work of Spiers and his coworkers has been used by the ICRP (27) in calculating dose
commitment factors for adults and by Papworth and Vennart (41) for doses as a function of
age at times of ingestion. The dose commitment values from Papworth and Vennart in red
marrow per uCi of Sr-89 and Sr-90 ingested are as follows (Table 6).
10
-------
Table 6. Dose commitment values
for Sr-89 and Sr-90
Age at Ingestion
/ V
(years)
0
0.5
1
2
3
4
5
6
7
8
9
10
11
Adultsa
rem per uCi
br-S?
0.41
-------
2.2 AGRICULTURE TRANSPORT MODELS
A review of the agricultural transport mechanism for radionuclides, which employs pa-
rameters appropriate for the U.S. experience, is contained in the Reactor Safety Study,
WASH-1400, Appendix VI (7). An analysis specific for calculating derived response levels
(concentration values) in agricultural media for emergency action that reflects the British
experience is found in a report of the Medical Research Council (*3).
A more recent and comprehensive assessment of the transport mechanisms for the forage-
cow-milk pathway is found in UCRL-51939 and will be used here (M)
2.2.1 Transport Models
According to Ng et al., the time dependency of the concentration of a radionuclide in
the milk of a cow continuously grazing pasture contaminated by a single event can be
described by (W):
where C^(t) = concentration of radionuclide in milk at time t (yCi/1)
IQ(O) = initial rate of ingestion of radionuclide by the cow ( u Ci/d)
Aj = coefficient of ith exponential term, which describes the secretion in milk (liter"1)
i = effective elimination rate of the itn milk component (d~l)
XR = radiological decay constant (d'1)
^MBi = biological elimination rate of ic^ milk component (d" l)
Xp = effective rate of removal of the nuclide from pasture (d'1), and
Xp = XR + Xw, where X\y is removal rate for a stable element from pasture (d'1),
and
t = time of milk secretion (d).
The total activity ingested by a person who drinks this milk can now be determined by
integration:
;"idt = /"jcM(t)dt = ;jic(o)
where I = rate of ingestion of the radionuclide by a person (uCi/d) and
3 = rate of consumption of milk (liter/d).
The solution for the total activity ingested by man is:
r -, dt =
0
12
-------
where f M = transfer coefficient; i.e., the fraction of daily intake by cow that is se-
creted per liter of milk at equilibrium (d/liter)
Ng et al. have conducted a comprehensive review of the literature relevant to the deter-
mination of transfer coefficients for both stable elements and radionuclides (44). These
data are summarized in UCRL-51939, which also include values »:' the normalized co-
efficients, A-,, the biological half-life TMBi (related to AMB^ for srlected elements and
values of fM for all stable elements. This information is then used with the radioactive half-
life to calculate values of fM for specific radionuclides of interest (Table B-l of Ng et al.
(44)). M
An examination of the logistics of the forage-cow-milk-man pathway shows that there is
generally a delay time between the production of milk by the cow and its consumption by
the general public. Therefore, it is appropriate to introduce a factor, S, to account for
radioactive decay between production and consumption, where
S = e ' Xt where X = the decay constant for a given radionuclide (d~ l)
and t = the delay between production and consumption (d).
Since the delay time for fresh whole milk is assumed to be 3 days only 1-131 of the
radionuclides of interest here has a sufficiently short half-life to result in a value of S
significantly smaller than one. Thus, for 1-131:
S(I-131) = e-°-0865C 3
5(1-131) = 0.772
Therefore, the total activity ingested as calculated by the above formula (Jldt) must 6e
multiplied by 0.772 in the case of iodine- 1 31.
2.2.2 Total Intake
The calculated values of integrated activity ingested per uCi/m 2 deposition from
Appendix B of UCRL-51939 will be accepted as the basis for deriving the response levels
equivalent to the PAG (44) . The values in Appendix B are based on these values of
parameters:
(1) Ic(0)» initial rate of intake by cow
UAF = "utilized area factor" (93)
UAF = 45 m z/d
Initial Retention on Forage = 0.5 fraction
Initial Deposition = 1 uCi/m 2
thus Ic(0) = 22.5 uCi/d,
(2) J = 1 liter/day consumption of milk, and
(3) Half-residence time on forage is 14 days.
13
-------
The UAF of 45 m 2/d assumes a forage consumption by the cow of 11.25 kg/d dry weight
or 56 kg/d wet weight based on a forage yield of 0.25 kg/m2 (dry weight) (45).
The values of the total intake per unit deposition (uCi/uCi/m *) for a 1-liter per day
milk intake from Ng et al., are given in Table 7, line 1 (44).
Table 7. Derivation of raporae levels equivalent to 1 rein dose commit nenl to critical organ
i - 131 cs - is* • • cr-T3»
. o LW1
1. Pathway intake factor* (tf) |.ja J.J2 ).22
(uCl/uCi/m1 per l/d)
Infant Adult Infant Adult Infant Adult
2. Dose conversion factor 16 1.3 .US .068 .071 .061
(rem/uCl ingested)
3. Intake per rem * 1 . .063 .67 S.3 l».7 l».l 16.*
line 2 '
(uCl intake per rem)
». Specif Ic intake factor (line Ix .72* .37* 2.11 1.77 2.23 1.77
0.7 or 0.33) - (uCl per u Cl/m1
3. Initial surface deposition (line 3) .OS6 1.17 3.9 8.6 S.3 9.3
line*
(uCI/m* per rem)
6. Peak concentration factor (see text) 0.116 0.078 0.078
(uCi/l per u Cl/m')
7. Peak milk concentration .0100 .136 .303 .67 .09 .72
( line 3 x line 6)
(uCI/l per rem)
8. Initial grass concentration .03*3 .«7 1.33 3.*3 2.30 3.70
(line 3xO.»)
(uCl/kg per rem)
"Corrected for decay during distribution (3 days 1 act or - .772)
5r - 90 5r - 59
.636 .»6
Infant Adult Infant Adult
2.09 .70 .19* .012
.00 I.O 3.2 S3
.«3 .33 .322 .293
.90 O.I 16 329
0.0196 0.018
.0177 .080 .288 3.9
.361 1.63 6.«0 LJ2
2.2,3 Peak Concentration
The time dependent equation for the concentration in milk CM(t) given above has been
evaluated for times up to 20 days. From a graph of the results, the peak concentration per
initial unit area deposition have been determined and are summarized in Table 7, line 6.
The peak concentration occurs at 3 days for 1-131 and at 6-8 days for cesium and strontium.
2.3 DIETARY INTAKE
Infant less than 1 year old - For the purposes of these recommendations, the dietary
intake of milk is estimated to be 0.7 liters per day for a newborn infant.
Based on the average intake up to and including 1 year of age, the daily intake of milk
for an infant less than 1 year of age is 0.7 liters (46). An additional 300 g of food may also
be assumed to be ingested by an infant less than 1 year of age (based on intake of 6 month-
old infants - Kahn, B. (47)).
Adult - Based on U.S. Department of Agriculture Household Food Consumption Survey
1965-1966, the average consumption for the general population is given in Table 8. The
dietary intake of milk is taken to be 0.55 liters per day for the adult.
In addition to water ingested in food and drink, an estimated 150 ml of tap water is also
ingested each day (46) for a total daily food intake of 2.2 kg.
14
-------
Table S. Average consumption for the general population
Average consumption
for the general population
Food
Milk, cream, cheese, ice cream3
Fats, oils
Flour, cereal
Bakery products
Meat
Poultry
Fish and shellfish
Eggs
Sugar, syrups, honey, molasses, etc.
Potatoes, sweet potatoes
Vegetables (excluding potatoes) fresh
Vegetables canned, frozen, dried
Vegetables juice (single strength)
Fruit, fresh
Fruit canned, frozen, dried
Fruit juice (single strength)
Other beverages
(soft drinks, coffee, alcoholic bvgs.)
Soup and gravies (mostly condensed)
Nuts and peanut butter
Total
R/day
567.5
5*. 5
90.8
149.8
217.9
50.5
22.7
50.5
72.6
104.0
105.3
77.2
9.1
163.0
36.3
05.0
177.1
36.3
9.1
2088.1
% of total diet
27.2
2.6
0.3
7.2
10.0
2.6
1.1
2.6
3.5
5.0
7.0
3.7
0.0
7.8
1.7
2.2
8.5
1.7
0.0
99.9
'Expressed as calcium equivalent; that is, the quantity of whole fluid
milk to which dairy products are equivalent in calcium content.
(From the U.S. Department of Agriculture Household Food Consump-
tion Survey, 1965-1966)
2.0 CALCULATIONS
The calculation of the derived response levels equivalent to 1 rem dose commitment
to critical organ for the grass-cow-milk-man pathway is summarized in Table 7. An explana-
tion of Table 7 and the calculations follow:
Line 1 Pathway Intake Factor is the total intake (pCi) for a 1 liter per day milk
ingestion per 1 uCi/m2 of initial area deposition (00).
Line 2 Dose Conversion Factor is the dose commitment in rem/uCi ingested. See
section 1 for summary.
Line 3 Intake per rem is intake in uCi to yield a 1 rem organ dose.
COMPUTATION - The reciprocal of line 2.
Line 0 Specific Intake Factor is the product of the Pathway Intake Factors (line 1) and
the milk ingestion rate of 0.7 I/day infant or 0.55 I/day adult. In the case of 1-131, a
factor of 0.772 is included to adjust for 3 day's decay between production and consumption.
COMPUTATION - Line 1 x (1 or .772) x (0.7 or 0.55)
Line 5 Initial Surface Deposition is initial area deposition of a specific radionuclide in
pCi/mz which gives a 1-rem dose commitment.
15
-------
COMPUTATION - Line 3 divided by Line 4
Line 6 Peak Concentration Factor is the peak maximum concentration in milk (uCi/1)
from an initial area deposition of 1 uCi/m2. Summary in Section 2.2.3 per model of
Ng et al.
Line 7 Peak Milk Concentration is the maximum milk concentration ( yCi/1) that yields
a dose commitment of 1 rem from continuous ingestion of the contaminated milk supply.
COMPUTATION - Line 5 x Line 6
Line 8 Initial Grass Concentration is the activity concentration (uCi/kg) on grass
(edible forage) chat results from the Initial Surface Deposition giving a 1-rem dose
commitment.
Retention fraction on forage - 0.5
Forage yield - 1.25 kg/m2 (wet weight)
COMPUTATION - Line 5 x 0.5
1.25 k
The derived response levels that correspond to the Preventive PAG (1.5 rem thyroid: 0.5
rem whole body and bone marrow) and the Emergency PAG (15 rem thyroid; 5 rem whole
body and bone marrow) are given in Tables 9 and 10.
Table 9. Derived response levels for grass-cow-milk pathway equivalent
to Preventive PAG dose commitment of 1.5 rem thyroid, 0.5 whole body
or red bone marrow to infant1
Response levels for ~~"~~~~~~~"~"~
Preventive PAG 1-1312 Cs-13»3 Cs-1373 Sr-90 Sr-89
Initial activity
area deposition
(uCi/m2)
Forage concentration1*
( viCi/kg)
•v
Peak milk acitivity
( uCi/1)
Total intake ( uCi)
0.13
0.05
0.015
0.09
2
0.8
0.15
4
3
1.3
0.24
7
0.5
0.18
0.009
0.2
8
3
0.14
2.6
1 New born infant includes fetus (pregnant women) as critical segment of population
for iodine-131. For other radionuclides, "infant" refers to child less than 1 year of
age.
2From fallout, iodine-131 is the only radioiodine of significance with respect to milk
contamination beyond the first day. In case of a reactor accident, the cumulative
intake of iodine-133 via milk is about 2 percent of iodine-131, assuming equivalent
deposition.
3 In take of cesium via the meat-man pathway for adult may exceed that of the milk
pathway; therefore, such levels in milk should cause surveillance and protective ac-
tions for meat, as appropriate. If both Cs-134 and Cs-137 are equally present, as
might be expected in reactor accidents, the response levels should be reduced by a
factor of 2.
"Fresh weight.
16
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Table 10. Derived response levels for grass-cow-milk pathway equivalent to emergency PAG dose commitment
of 15 rem thyroid, 5 rem whole body or red bone marrow
Response levels for I- 131J Cs - 134' Cs - 137' Sr - 90 Sr - 89
emergency PAG Infant1 Adult Infant2 Adult Infant2 Adult Infant2 Adult Infant2 Adult
Initial activity
area deposition
(pCi/m2) 1.3 18 20 40 30 50 5 20 80 1600
Forage concentration
(uCi/kg)" 0.5 78 17 13 19 1.8 8 30 700
Peak milk activity
0.15 2 1.5 3 2.4 4 0.09 0.4 1.4 30
Total intake (uCi) 0.9 10 40 70 70 80 2 7 26 400
'Newborn infant includes fetus (pregnant women) as critical segment of population for iodine-131.
2"Infant" refers to child less than I year of age.
3From fallout, iodine-131 is the only radioiodine of significance with respect to milk contamination beyond first day. In case
of a reactor accident, the cumulative intake of iodine-133 via milk is about 2 percent of iodine-131 assuming equivalent de-
position.
"Fresh weight.
5 Intake of cesium via the meat-man pathway for adult may exceed that of the milk pathway: therefore, such levels in milk
should cause surveillance and protective actions for meat, as appropriate. If both Cs-134 and Cs-137 are equally present as
might be expected for reactor accidents, the response levels should be reduced by a factor of 2.
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CHAPTER 3. METHODS OF ANALYSES FOR RADIONUCLIDE DETERMINATION
3.1 INTRODUCTION
The measurement of radionuclides in food can be accomplished by either laboratory
methods or field methods using portable survey instrumentation. Unfortunately, neither
method of analysis was developed expressly for the purpose of implementing protective
actions. In order to provide instrumentation guidance to the States, the Federal Radiologi-
cal Preparedness Coordinating Committee formed a Task Force on off site instrumentation.
A draft report on instrumentation analysis methods for che milk pathway is now undergoing
review by the Task Force and a second report on other food is under development. This
effort is being fostered by past and current contracts of Nuclear Regulatory Commission
(NRC) and Federal Emergency Management Agency (FEMA) with Brookhaven National Lab-
oratory and Idaho National Engineering Laboratory.
The material and methods are given as interim guidance until these more definitive
reports are available. It should be noted that laboratory methods of Chapter 3.2, below,
were developed for environmental monitoring purposes and are more sensitive than required
for protective actions implementation. And, conversely, the field methods of Chapter 3.3
are generally inadequate for the purpose of implementing action at the Preventive PAG
level. Analysis methods should be able to measure radionuclide concentrations in food lower
by a factor of 10 than the derived levels for Preventive PAG. Thus, it may be necessary to
use a combination of laboratory and field methods in implementing and ceasing protective
actions.
3.2 DETERMINATIONS OF RADIONUCLIDE CONCENTRATIONS BY SENSITIVE
LABORATORY METHODS
Many compendia of- methods of analysis of environmental samples are available. The
EML Procedure Manual recommended is noted for its up-to-date methodologies, which
continuously undergo revision and improvement (48). Analysis need not be limited to refer-
ence 48 but laboratory analysis of food should provide limits of detection as listed below,
which are lower than required for protective action:
Limit of detection*
Radionuclide pCi/liter or kg
1-131 10
Cs-137 10
Sr-90 1
Sr-89 5
•Concentration detectable at the 95-percent confidence level.
A source of more rapid methods of analysis of radionuclides in milk, applicable to these
recommendations is described by B. Kahn et al. (49). The methods for gamma radionuclide
analysis (applicable to 1-131 and Cs-137 presented in this reference are also applicable to
pasture. The gamma scan determinations of 1-131 and Cs-137 in milk (or water) can
generally be accomplished within 2 or 3 hours. For samples measuring in the 0-100 pCi/liter
range, the error at the 95-percent confidence level (2 sigma) is 5 to 10 pCi/liter. For
samples measuring greater than 100 pCi/liter the error is 5 to 10 percent.
18
-------
Radiostrontium procedures permit analyses of several samples simultaneously in 5 hours
of laboratory bench time, plus 1-2 weeks for ingrowth of yttrium daughters. If the laborato-
ry is sec up for routine analysis of these radionudides recovery in tracer studies is 80 ± 5
percent.
An ion exchange field method for determination of 1-131 in milk, whid. uses gamma
spectroscopy after sample collection, has also been described (50). The main advantage of
this method is that it permits a large number of samples to be processed in the field or
shipped and analyzed in a central laboratory.
For analysis of samples other than milk the HASL reference (48) is recomnr ended.
3.3 DETERMINATIONS OF RADIONUCLIDE CONCENTRATIONS BY FIELD METHODS
3.3.1 Ground Contamination (Beta Radiation)
The conversion of ground survey readings to contamination levels can be accomplished
by using the following equations and factors (assuming a metal tube wail thickness (sceel) of
30 mg/on2):
1. Use a G-M survey meter calibrated to yield 3,000 counts/min per 1 mR/h of Ray
2. Hold the probe not more than 5 cm above the ground with the beta shield open.
3. Assure that 100 counts/min can be detected above a normal 50 to 100 counts/min
background.
4. Take readings in open terrain; that is, not in close proximity to heavy vegetation,
cover, or buildings.
For determinations of ground deposition:
D = RxF
where, D = ground deposition (in yCi/m2),
R = G-M reading (in units of 102 counts/min) (background
corrected), and
F = factor given in Table 11.
For determination of concentrations in vegetation:
C = (Dx
where, C = concentration (in yCi/kg),
D = ground deposition (in p Ci/m2),
f = fraction of deposited nuclide in the vegetation, and
d = density of vegetation cover (in kg/m2).
Generally, f ranges from 0.1 to 1 and is usually taken to be 0.25 for 1-131 in the
United Kingdom, and 0.5 in the United States.
19
-------
Data of a similar nature may also be found in "Emergency Radiological Plans and Proce-
dures," in the Chapter (Item 04.3.4) on "Conversion of Survey Meters to Concentration," (51).
Table 1 1 . Ground surface contamination levels3 of various nudides
required to yield 100 counts/min (net) on a G-M meter (open window)
- p -
_____ _ Nuclide _ (uCi/m2 per 100 counts/min)
Zr-95 + Nb-95 6
Ce-141 2
1-131, Ru-103m, mixed Ru-Rh (100-dold)b 1
Co-60, Sr-89, Y-90, Y-91, Cs-137, Ba-140, La-
- - - 0.3
Ce-144 + Pr-144, Ru-10^i Rh-106,
mixed radioiodines (1-h to 1-week old),
mixed fission-products (100-d old)
*Level varies with background readings, ground roughness, and vegetation cover.
"Age refers to time since irradiation of the fuel from which the Fission Products were
released.
3.3.2 Herbage
A field method for estimation of radionudide contamination at the response levels
equivalent to the Emergency PAG for pasture (forage) which has been suggested by
International A comic Energy Agency (52) is as follows:
1. Obtain enough vegetation to fill a 30 cm x 40 cm plastic bag approximately half
full. This is about one-third of a kilogram (Note: the vegetation cover should be obtained
from at least 1 m2 of ground. The vegetation should be cut at approximately 1 to 2 cm
from che ground and should not be contaminated in the process by soil).
2. Note the area represented by this quantity of material.
3. Compress the air from the bag and seal.
4. Transfer che sample to a low background area.
^
5. Flatten bag and lay probe of a portable G-M survey meter on the center of the bag.
6. Wrap bag around probe and note reading (window open and background corrected).
7. Calculate the contamination from the following equation:
C = R/k
where, C = vegetation concentration (in y Ci/kg),
R = G-M reading (in units of 102 counts/min) (background corrected), and
k = 102 counts/min per u Ci/kg as given in Table 12.
8. Convert u Ci/kg to u Ci/m2 on che basis of che area represented by the sample.
20
-------
9. The limiting radionuclide (i.e., having the lowest recommended PAG relative to
its deposition on pasture) is iodine-131. According to Table 12, this radionuclide
is detected with the lowest efficiency. Thus, if the operator assumes this
radionuclide to be exclusively present in the pasture the most conservative
estimates relative to the Emergency PAG would be reached.
Table 12. Typical G-M survey-meter readings probe
inserted in the center of a large
sample i f vegetation
k
Nuclide (10* x counts/min per uCi/kg)
Sr-89, Sr-90 + Y-90 20
Ru-106 + Rh-106 50
Ba-140 >La-140 10
1-131. Cs-137 4
3.3.3 Milk
The experimental data for field determination of radionuclides in milk are limited to
determination of iodine-131, and the details are rather sketchy. What material is available
is abstracted below.
1. Although no data are available for field determination of radionuclides other than
iodine-131 in milk, Table 13 presents experimental information obtained in water (52,53).
To the extent milk is more self-shielding than water, the following data is presented as a
guide rather than a means of analysis.
Table 13. G-M survey-meter open window readings (counts/min
per iiCi/liter) (probe immersed in contaminated water)
Size of sample container
Nuclide 1 liter 5 liters > 10 liters
Counts/min per uCi/l
Sr-89 2000 2000 2000
Sr-90 + Y-90 2000 2000 2000
Ru-106
-------
by the probe shielded within the test hole by 3 cpm. Background, on the aver-
age, was measured (in "pure" water) to be 12 to 15 cpm (in an uncontaminated
environment). Thus, total background counts (with sky shine) is on the average
around 19 cpm.
e. From Figure 2, the net counts per minute equivalent to the response level for
the Emergency PAG applicable for milk (infant as critical segment of
population) is approximately 20.
3. Method of C. Distenf eld and J. Klemish (55).
a. Instruments:
i. CDV 700 instrument turned to 10 X scale and calibration adjustment turned
to require the meter to indicate 2 mR/hr. (NB: Discrepencies were noted
between data from scale and pulse counting with an oscilloscope).
ii. Modified CDV 700 M with factory calibration. Good agreement between
scale reading and electronic check.
b. Geometry: The basic container was a 5-gallon heavy-wall polyethylene "3erri"
type measuring 12x9x10 inches. A 2-inch O.D. blind tube was installed to
allow the G-M probe to sample the center of the container.
c. Counts were taken inside and at the top (external) to the container.
d. Background was determined in a water filled plastic container (15x25x20 cm)
about 7 meters from the sample vessel.
e. Net counts per minute equivalent to the response levels for the Emergency
PAG for milk are summarized in Table 14.
4. The International Atomic Energy Agency reports on a series of experiments (53).
The data are duplicated in Table 15.
5. A forthcoming report of the Federal Interagency Task Force on Offsite
Emergency Instrumentation for Nuclear Incidents to be published by FEMA is
"Monitoring and Measurements of Radionudides to Determine Dose Commitment
in the Milk Pathway." A subsequent report by the Task Force will address field
methods and monitoring strategies for other food pathways.
6. The relative sensitivity of the various techniques is summarized in Table 16.
22
-------
Water tight
Al or plastic tub*
(1"to 1 1/2"
dlam.; 3* long)
Plastic lining
E irth fill - 4
a) 17.5 qts of
"pure" water
b) Contaminated
milk.
S gal. container '//.
(small plastic '/I
garbage } "{.
'W//////////.
3.3" stick in 7/L
bottom of tube
* CDV-700. Model No. 68 covered with small plastic bag taped to cable
of probe la further protect against dampness.
Figure 1. Geometry for making
measurements within a volume
of liquid.
I 1 1 1 1 1 1
(After Keamy ORNL-4900)
0 20 40 60 80 100 120 140 160 180 200 220 240
Net Counts Per Minute*
'Net counts per minute determined by ear. Net counts per
minute = grosscounts per minute — background in pure water.
Figure 2. Net counts per minute*
23
-------
Table 14. Net counts per minute equivalent to the response
levels for the Emergency PAG for milk
Instrument
Probe Position
Approximate
net counts per minute
CDV-700
Inside
Outside
CDV-700M
Inside Outside
Response level for
Emergency PAG
(Milk-Infant)
(Milk- Adult)
20*
260
ga
110
220
2,900
100
1,300
*At or below background cpm - precision not adequate.
Table 15. Survey-meter readings versus concentration
of 1-131 in a 40-liter milk can
Meter
used
Al-walled
GM probe
Mica-window
GM probe
a,B,Y
scintillation
survey-meter3
Transportable
single-channel
analyzer system
uCi I- 131 /liter
milk
0.9
0.5
0.1
0.05
Background
0.9
0.5
0.1
0.05
Background
0.9
0.5
0.1
0.05
Background
0.10
0.05
0.01
0.005
Background
Net counts
Inside can
1,500
500
100
50
50
600
400
100
50
50
5,500
3,000
600
250
100
1,200
650
140
80
30
per minute
Outside can
300
200
50
50
50
250
100
50
50
50
3,000
1,500
300
150
100
-
-
-
-
-
^Crystal is 3-mm thick disc of "Bioplastic" scintillator sprayed with
10 mg/cm2 of ZnS. Effective area is 6.4 cm2.
24
-------
Table 16. Comparison of methodologies
cpm per uCi liter"
Inside Outside
IAEA - 197* (52) 1,000
Kearney - ORNL (5») 140
Distenfeld and Klemish - Brookhaven (55)
CDV-700 13* 56
CDV-700M 1,«0 660
IAEA - 1966 (53)
Al Walled CM Probe 1,100 350
Mica-Window CM Probe 700 250
at6iy Scintilla**0" 6,000 3,300
Survey Meter
Transportable Single 12,000
Channel Analyser
25
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CHAPTER k. PROTECTIVE ACTIONS
The National Advisory Committee on Radiation (56) (NACOR) made the following recom-
mendation that applies to action taken to reduce potential exposure following the accidental
release of radioactivity:
"A countermeasure, useful to public health, must fulfill a number of i-.*q>iirements.
First, it must be effective; that is, it must substantially reduce population exposures below
those which would prevail if the counter measure were not used. Second, it must be safe;
i.e., the health risks associated with its use must be considerably less than those of the
contaminant at the level at which the countermeasure is applied. Third, it must be
practical. The logistics of its application must be well worked out; its costs must be
reasonable; and ail legal problems associated with its use must be resolved. Next,
responsibility and authority for its application must be well identified. There must be no
indecision due to jurisdictional and misunderstandings between health and other agencies
concerned with radiation control. Finally, careful attention must be given to such
additional considerations as its impact on the public, industry, agriculture, and govern-
ment."
An action, in order to be useful must be effective, safe, and practical. An action may be
applied at the source in an attempt to control the release of radioactivity from the source;
or, the action may be applied at the beginning of the food chain (soil, vegetation, or cattle),
to the immediate vector prior to ingestion by man (milk or food), or to the population itself.
For the most part these recommendations suggest protective actions to milk, human and
animal foods, or soil and this chapter is limited to actions concerning these media. Further
recommendations by NACOR (56) extend the discussion of protective measures to public
health actions directly affecting the exposed population. For details of agriculture actions,
several Department of Agriculture reports are available that deal with specific actions for
crops and soil (57,58,59).
Potential actions relative to the pasture-milk-man pathway are summarized in Table 17.
For this pathway, only four countermeasures are rated as effective, safe, and practical (a
somewhat arbitrary scale of judgment was used). Of the four, one has distinctive
disadvantages. Although removal of radionuclides from milk has been shown to be practical
no facilities for doing this exist. Another, diverting fresh milk to processed milk products,
freezing and/or storage, is effective only for short-lived radionuclides. Thus, changing
dairy cattle to an alternate source of uncontaminated feed and condemnation of milk
are the only two protective actions rated good for effectiveness, safety, and practicality.
Of course the other countermeasures should also be considered, but they appear less
promising.
Actions for fruits and vegetables are presented in Table 18 (60,61,62). Note chat studies
in which these products were contaminated under actual conditions with fallout (Studies
2 and 3) yielded a lower reduction in the radioactivity removed during preparation than
was the case in an investigation (Study 1) in which radionuclides were sprayed on the food.
Depending on the food, reductions between 20 and 60 percent in strontium-90 contaminations
are possible by ordinary home preparation or by food canning processes (60).
Milled grains contain only a small portion of the total radioactive contamination of
the whole grain; removal of bran from wheat and polishing of rice are effective methods of
reducing contaminating fallout (58). Todd indicated average concentration of Sr-90 (pCi/kg)
26
-------
in wheat of wheat berry (22 ), wheat bran (68 ), and only <*.& in flour. In rice the corres-
ponding values are: whole grain U.9 ), and milled rice (0.7 ),(58).
Although these recommendations are intended for implementation within hours or days
after an emergency, long-term actions applicable to soil are shown for information purposes
only in Table 19. Alternatives to decontamination and soil management should be
considered, especially if the radioactive material is widespread, because great effort is
required for effective treatment of contaminated land.
The concept of Protective Action assumes that the actions impien ented will continue
for a sufficient period of time to avoid most of the projected dose. Tie concentration of
radioactivity in a given food will decrease because of radioactive deoiy and weathering as a
function of time after the incident. Thus, as discussed in Chapter 5 ol this report, actions
that have a positive cost-benefit ratio at the time of initial contamination or maximum
concentration may not have a positive cost-benefit ratio at later times. Therefore, depend-
ent on the particular food and food pathway, it may be appropriate to implement a series of
protective actions until the concentrations in the food have essentially reached background
levels.
»
As an example of the Implementation of protective actions, consider the case where an
incident contaminates the pasture-cow-milk-man pathway with a projected dose of 2-3
times the Emergency PAG due to iodine- 131. In such a situation these protective actions
may be considered appropriate:
1. Immediately remove cows from pasture and place them on stored feed in order to
prevent as much iodine-131 as is possible from entering the milk;
2. Condemn any milk that exceeds the Emergency PAG response at the farm or milk
plant receiving station;
3. Divert milk contaminated at levels below the Emergency PAG to milk products;
and
*>. Since the supply of stored feed may be limited and the costs of this protective
action greater than diversion to milk products, the use of stored feed may be the first
action to cease; this should not be done, however, until the concentration of 1-131 has
dropped below the Emergency PAG and preferably is approaching the Preventive PAG.
5. The diversion of fresh milk to milk products must continue until most of the
projected dose has been avoided; this action might be ceased when the cost-effectiveness
point is reached or the concentration of iodine-131 approaches the background levels.
This discussion assumes that there is an adequate supply of whole milk from noncon-
taminated sources, that there is an available manufacturing capacity to handle the diverted
milk, and that the iodine-131 is the only radionuclide involved. In an actual situation these
conditions may not be present and other factors may affect the practicality of proposed
protective actions. The agency responsible for emergency action must identify and evaluate
those factors that affect the practicality of protective action, and thus develop a response
plan (with tentative protective action) that is responsive to local conditions and capabilities.
27
-------
Table 17. Actions applicable to the pasture-milk-man pathway (compiled from references 57 and 59)
DO
Action
Applicable to cattle
Provide alternate source of
uncontaminated animal feed
Add stable iodine to cattle ration
Add stable calcium to cattle ration
Add binders to cattle ration
Substitute sources of uncontaminated water
Applicable to milk
Condemnation of milk
Divert fresh milk to processed milk products
Process fresh - store
Process fresh - store
Remove radionuclides from milk
Radionuclide(s) for which protective action is applicable
Practicality
Effectiveness Safety (effort required)
!III, "Sr, "Sr, M7Cs (+)a (+) ( + ) Good
I Marginal Some hazard (+)
"Sr, "Sr Marginal Some hazard ( + )
IJ7Cs, "Sr, "Sr Marginal Questionable (+)
117- •»_ 90- , . / . . .c
Cs, Sr, Sr (+) (*) ( + )
111. 89- 90_ 11 V / % i ^ , .d f~ j
1, Sr, Sr, Cs (+) (+) ( + ) Good
Mll, "Sr (+) (+) ( + ) Good
>0Sr, M7Sr Marginal Questionable (+)
>nl (O (+) (t) Good
ml, "Sr, "Sr, J7Cs (*) ( + ) (*)e Good
: 90%effective
bMarginal: less than 90% effective
cDepends on availability
^Somewhat dependent on volume
eNo processing plant presently available
-------
ro
Table 18. Percent reduction in radioactive contamination of fruits and vegetables by processing
Spinach
Snap beans
Carrots
Tomatoes
Broccoli
Peaches
Onions
Potatoes
Cabbage
Green beans
Normal
External
"Sr
92
-
-
-
94
" 100
-
_
-
-
Study 1 (60)
food preparation for freezing, canning or
Contamination3 Internal
U)Cs
95
-
-
.
92
"•100
.
_
-
-
"Sr
64
-
_
65
72
~100
-
_
-
-
dehydration
Contamination3
-A-uu"UJCs
88
_
_
_
89
-100
_
_
-
-
Study 2(61)
Canning
22
62
19
21
„
50
.
_
-
-
Study 3 (62)
Home preparation
90Sr
.
-
19
28
.
_
37
24
•»
36
Contamination on surface is referred to as external contamination. Internal contamination is contamination of fleshy portion
of product from surface deposition of radionuclide.
-------
Table 19. Actions applicable co soil (compiled from references 57 and 59)
Action
Radionuclide(s) for which protective action is applicable
Practicality
Effectiveness8 Safety (effort required)"
Applicable to soil
Soil management—minimum tillage: 905,- poor to fajr
deep plowing with root inhibition tosr Good to fair
irrigation & leaching »o$r poor
liming & fertilizing »osr Poor to fair
Removing contaminated surf ace crops »«Sr Most poor
Not applicable
it
aRating for reducing strontium -90
Good- 95% reduction
Fair - 75-95% reduction
Poor - 75% reduction
^Rating for effort required
Good - not significantly more than normal field practice
Fair - extra equipment or labor required
Poor - very great requirement of equipment, materials, and labor
Good
Poor
Good
Good
Poor to fair
Removal of soil surface contamination:
warm weather with vegetation cover
cold weather no cover
»°Sr
»°Sr
Good to fair "
Good to poor »
Poor
Good to poor
-------
CHAPTER 5. COST CONSIDERATIONS
5.1 COST/BENEFIT ANALYSIS
5.1.1 Introduction
The general expectation is that protective action taken in the event of a nuclear
incident will result in a net societal benefit considering the cost of the action and the
corresponding avoided dose. These cost assessments, including cost/benefit analysis, have
not been used to set the numerical value of the PAG's but rather to evaluate the feasibility
of specific protective actions.
At least two basically different approaches can be used to assess the cost/benefit ratio
of protective actions for the milk pathway. One approach would be to assume a protective
action scenario (maximum milk concentration and length of time of protective action) and
to calculate the total cost of the action and the benefit because of the avoided dose. The
ratio of the cost/benefit can then be used to scale the maximum milk concentration to that
concentration that yields equal costs and benefits. The problem with this approach is that
positive net benefits when milk concentration of radioactivity is high are used to offset
the negative net benefits during the later times of action.
This deficiency leads to the second approach of calculating the milk concentration on a
per liter basis where the cost of the protective action equals the benefit because of the
dose avoided. This approach will be used here since it gives a clearer picture of the
identified costs and benefits. The specific concentration at which costs equals benefits
should not however be viewed as the appropriate level for taking protective action. The
philosophy of protective action is to take action to avoid most of the projected doses.
Further, the simple analysis considered here treats only the direct cost of protective
actions and ignores the administrative costs of starting, monitoring, and ceasing action,
and other related social and economic impacts.
Although the PAG recommendations provide that protective actions be taken on the
basis of projected dose to the infant, cost/benefit analysis must consider the cost impact
on the milk supply and the benefit on a whole population basis. Accordingly the benefit
realized from avoiding the dose associated with a given level of milk contamination
C (uCi/1) must be summed over the age groups having different Intakes (I) and Dose
Factors (OF) and is:
Benefit = C (uCi/1) x Value ($/rem) ZIi(l/d).DFi(rem/uCi).
The total cost of the protective actions, which must also be summed over all the age intake
groups is:
Cost = PA COST x Zli
Costs are in 1980 - 1981 dollars. These equations can then be solved for the concentration
(C) at which cost = benefit giving:
C (C=B) = PA COST Zli
Value ($/rem)
31
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5.1.2 Benefit of Avoided Dose
In situations in which chere has been an uncontrolled release of radioactivity ro the
environment, both the health savings and cost of a protective action can be expressed in
terms of dollar values. This does not exclude the probability that undesirable features will
result from an action thm is difficult to evaluate in economic terms.
A previous cost-benefit analysis described che radioactive concentration of iodine-131 in
milk at which it would *Te justifiable to initiate condemnation of milk (63). Following is a
summary of the moneta-y benefit of radiation dose avoided using the approach suggested,
with changes because of increased costs over time and new data on the relative incidence of
various tumors.
The International Commission on Radiological Protection, (6*) has endorsed the principle
of expressing the detriment from radiation in monetary terms in order to facilitate
simplified analysis of costs and benefits. This permits a direct comparison between the
societal advantage gained in a reduction of the radiation dose and the cost of achieving this
reduction. Cost-benefit analysis is the evaluation process by which one can determine the
level at which, or above which, it would be justifiable to initiate the protective action
because the health savings equaled or exceeded, the economic coses of die protective
action. Certain factors, such as loss of public confidence in a food supply, are noc
considered; nor are economic factors because of hoarding and a shortage of supply
considered. A similar treatment of the problem with almost the same result has
been published (65). This type of exercise is useful prior to taking an action as one, and
only one, of a series of inputs into decisionmaking.
The costs, and hence health savings to society, of 1 person-rem of whole-body dose (the
product of a dose of 1 rem to the whole body and 1 person) has been estimated by various
authors to be between $10 and $250 (66). The Nuclear Regulatory Commission (NRC) value
for a cost-benefit analysis for augmented equipment for light-water reactors to reduce
population dose, sets radiation costs at $1000 per person-rem (67).
Based on medical expenses in 1970, the total future cost of the consequences of all
genetic damage of 1 person-rem (whole-body) was estimated by the BEIR Committee (2) to
be between $12 and $120. These costs are in good agreement with estimates made by
Arthur 0. Little, Inc., for the Environmental Protection Agency, which calculated that
in terms of 1973 dollars, 1 person-rem of radiation yielded a tangible cose of between $5 and
$181 due to excess genetic disorders. A tangible cost of between $7 and $24 per person-rem
was estimated to be the result of excess cancer in the same report. Therefore, the total
health cost of a person-rem from these studies is between $12 and $205 (68).
Assuming that $200 is a reasonable estimate for the overall somatic health cost to socie-
ty per person-rem whole body, the proportionate cost for individual organ doses must then
be derived. For the purposes of assessing health cost, it is appropriate to use the relative
incidence of cancer estimated to result from organ doses vs. whole body doses. From BEIR-
III (3) (Table V-14 and V-17, and using an average of the male and female incidence) the
thyroid contributes 20 percent of cancer and leukemia (red bone marrow doses) 11 percent
of the total cancer incidence. Hence, the monetary costs per rem of radiation dose avoided
are: to thyroid $40; and to red bone marrow $22.
5.1.3 Protective Action Costs
The direct cost of protective action will be assessed for (1) cost of stored feed, (2)
condemnation at the farm (farm value), and (3) condemnation at the processing plant (retail
value).
1. Cost of stored feed. For the participating herds (May 1, 1978 - April 30, 1979)
the Dairy Herd Improvement Letter (69) reports a consumption of 12,600 Ibs. of succulent
32
-------
forage and 3,000 Ibs. of dry forage, with a corresponding annual milk production of 14,129
Ibs. (6200 liters). (The cows also consumed 5,800 Ibs. of concentrates, which are not of
concern here.) Taking 3 Ibs. of succulent forage (silage) as equivalent to 1 Ib. of hay, the
annual hay equivalent consumption is 7,200 Ibs (70). Thus, 1.16 Ibs. of hay equivalent is
consumed per liter of milk production. The 1980 average price received by farmers for all
baled hay was $67.10 per ton or $0.0335 par Ib. (71). The Protective Action (PA) cost of
buying baled hay to replace pasture as the sole forage source is then $0.039 per liter.
2. Milk-farm value. The average pr'ce received by farmers for fluid-eligible milk,
sold to plants and dealers in 1980, was $13.11 per hundred weight (monthly range $12.70 to
$14.20) (71). The lower prices are received during the pasture season of April through
August. For 44 liters per hundred weight, tlie farmer value of milk is $0.30 per liter.
3. Milk-retail value. Since it may be necessary to take protective action at some
stage in the milk processing and distribution system it is appropriate to consider the retail
value of milk. If condemnation of milk is taken at the receiving station or processing plant
there will be additional costs above farm value associated with disposal. It is felt that
retail price should represent an appropriate value. The average city retail price of fortified
fresh whole milk sold in stores, January through October 1980 was $1.037 per 1/2 gallon
(72). The monthly price increased from $1.015 in January to $1.067 in October, apparently
because of inflation. Based on the average price the value of $0.56 per liter will be used.
5.1.4 Population Milk Intake and Dose
Table 20 summarizes the milk intake by population age groups and gives values of the
age group intake factor Ii(l/d). The total intake by a population of 1000 is 281 1/d or an
average individual daily intake of 0.28 1. The intake factor (li) is used with the dose factor
DFi listed in Table 21 to calculate the dose factor summed over the whole population
weighted by age per uCi/1 of milk contamination.
5.1.5 Milk Concentration For Cost = Benefit
The above results are then used to calcultate the milk concentration at which the
Protective Action (PA) costs equals the benefit from the dose avoided. The results are
presented in Table 22. The cost = benefit concentration for use of stored feed in place of
contaminated pasture is about 0.2 to 0.3 of the Preventive PAG for strontium and 0.01 to
0.02 for iodine and cesium. For condemnation, the cost = benefit concentrations based on
farm value of milk have ratios of the Emergency PAG similar to those above. The cost =
benefit concentrations based on retail value of milk are about a factor of 2 greater than
those based on the milk's farm value. The fact that the cost = benefit concentrations are a
significant percent of the PAG for strontium results largely because the value of the person-
rem dose to red bone marrow is one-ninth that of whole-body doses while the PAG's are set
at equal doses consistent with current regulations. Further the controlling PAG's are for
the infant, while the cost/benefit reflects population averaged benefits.
Table 20. Population milk intake lEIi)
ARC group
In utero
0 <1
1 - 10
11 - 20
>20
Persons per
1000 popu-
lation
11
14
146
196
633
El
Milk intake3
(1/d)
.4
.775
.470
.360
.200
i
Intake (li) by
age group
(J/d)
4.4
10.9
68.6
70.6
126.7
281.2
a!CRP, 1974
33
-------
Table 21. Population dose factors
5r-89
Age group
In utero
0 < 1
1 - 10
11 - 20
>20
DFi
rem/uCi
.414
.194
.0565
.0175
.012
EHDFi
li x DFi
rem • 1
uCi d
1.22
2.12
3.88
1.24
1.52
10.58
Sr-90
DFi
rem/uCi
4.03
2.49
.929
.82
.70
li x DFi
rem • [_
uCi d
17.7
27.2
63.8
57.9
88.7
255.3
Reference for
DFi values3
0 yr old
0.5 yr-old
Average
Av 11 yr& adult
Adult
See Chapter 2.
Cs-134
Age group
In utero
0 < 1
1 - 10
11 - 20
> 20
DFi
rem/uCi
.068
.118
.093
.093
.068
ZliDFi
•i x DFi
rem • 1
yCi d
.3
1.29
6.39
6.57
8.51
23.06
Cs-137
DFi
rem/uCi
.061
.071
.066
.066
.061
li x DFi
rem • 1
uCi d
.27
.77
4.53
4.66
7.73
17.966
Reference for
DFi values3
Adultb
Infant
Av. infant
& adult
it
Adult
aSee Chapter 2.
"No credit taken for reduced biological half-life in pregnant women.
1-131
Age group
li x DFi
DFi rem • 1^
rem/uCi uCi d
Reference for
DFi values3
In utero
0 < 1
1 - 10
11 - 20
>20
8
16
5.7
2.1
1.5
Eli DFi
35
174
391
148
190
938
Max. estimate
Newborn
Average from
smooth curve
15 yr old
Adult
aSee Chapter 2.
34
-------
Table 22. Milk concentration at which cost = benefit
(Population basis - value of IlixDFi for 1000 persons)
Zli x DFi
rem 1
uCi'd
5r-89
10.58
5r-90
255
1-131
938
Cs-134
23.1
Cs-137
17.96
Value ($/rem) 22 22 40 200 200
PA cost CONG. (Cost = Benefit) (uCi/1)
Stored Feed $0.039 .047 .002 .0003 .0025 .003
Farm Milk 0.30 .36 .015 .0023 .018 .025
Retail Milk 0.56 .68 .028 .0042 .034 .044
Peak CONG. (uCl/1)
Preventive PAG
Emergency PAG infant
Emergency PAG adulr
.14
1.4
30
.009
.09
.H
.015
.15
2.0
.15
1.5
3.0
.24
2.4
4.0
5.2 ECONOMIC IMPACT
The Emergency Planning Zone (EPZ) for the ingestion pathway has been set at 50 miles
(73). The area impacted that requires protective action is the major factor influencing cose.
Assessment of the economic impact will be considered for the case of contamination of the
milk pathway in one 22.5° Sector out to a distance of 50 miles. Table 23 gives data on the
annual sales of whole milk and total area of leading dairy States and selected States. The
annual milk sales in Wisconsin of 3.52 x 10s Ibs. per sq. mile exceeds that of any other
State and will be used to assess the economic impact. There may, of course, be individual
counties and areas surrounding nuclear power plants where milk production exceeds the
Wisconsin State average. The Wisconsin average should, however, represent a maximum for
most areas of the United States.
Table 23. Milk production of selected States
(Statistical Abstract of the U.S., 1978)
State
WI
VT
NY
PA
IA
CT
MN
OH
MI
CA
MA
N:
Whole milk sold
(109 Ibs/vear)
20.5
2.06
9.92
7.37
4.07
.595
9.27
4.43
4.63
11.53
0.55
0.52
Total area
(mi2)
56,154
9,609
49,576
45,333
56,290
5,009
84,068
41,222
58,216
158,693
8,257
7,836
Milk per unit area
10s lbs/mi2
3.52
2.14
2.00
1.64
1.38
1.19
1.10
1.08
0.80
0.73
0.67
0.66
Another important factor in assessing the economic impact of protective actions in the
milk pathway is the length of time that such actions will be necessary. During most of the
year in northern parts of the U.S., cattle will already be on stored feed and chere will be no
35
-------
additional costs for the stored feed protective action. For other situations and the Emer-
gency PAG, the time over which protective actions will be necessary is a function of a
number of parameters unique to each site and the causative accident. Thus, what are
intended as conservative assumptions will be selected. The time behavior of 1-131 on
pasture grass is controlled by the 8-day radioactive half-life and the U-day weathering half-
life (yielding an effective half-life of about 5 days). Milk which contains 1-131 at the
Emergency PAG of 0.15 uCi/1 will be reduced to the cost = benefit concentration (farm
value) of 0.0023 uCi/1 about 30 days later. Obviously in most cases of an atmospheric
release, those areas closer to the release point will have higher levels of contamination and
longer times of protective action. The NRC and EPA in the Planning Basis Report NUREG-
0396 (NRJ, ^1978) assume that radiation doses from the airborne plu ne decrease according
to the r l< factor. Use of this factor for contamination of pasture results in milk
concentrations at 2 miles that are about 100 times that at 50 miles. For an effective half-
life of 5 days this would require an additional 30-35 days of protective action at 2 miles
over that at 50 miles to yield the same milk levels upon ceasing action. Although these
models cannot be assumed to be rigorously accurate in a specific accident situation, they do
indicate that action might be required for 1 or 2 months.
NUREG-0396 notes that the dose from milk pathway is of the order of 300 times the
thyroid dose from inhalation (7*). Under this assumption (and above models), the food PAG's
would be exceeded at hundreds of miles if protective action because of inhalation were
required at 10 miles. It should be noted that the meteorological models that are empirically
derived are not likely to be valid for such long distances. Further changes in wind direction
and meteorological dispersion conditions may reduce the levels 01 pasture contamination
and the downwind distance. For assessing ecomomic impact, contamination of a 22.5°
Sector out to a distance of 50 miles will be arbitrarily assumed, even though actual
contamination patterns are not likely to be similar.
Under these assumptions we then have:
Area (Circle - 50 mile radius) - 7850 mi2
Area (22.5° Sector - 50 mile) - Ml mi2
Milk Production - 3.52 x 10s lbs/mi2 per year - 2.93 x 10" lbs/mi2 per month
Production (22.5°/50 mi Sector) - 1.** x 10 7 lbs./month
Cost of Stored Feed - $0.017 per Ib. milk
Cost Impact (22.5°/50 mile Sector) - $2.*6 x 10s per month
Thus, the direct cost of placing cows on stored feed within a 22.5° Sector out to 50
miles based on farm value, would be about $0.25 million per month. The cost would be zero
during that portion of the year and in geographical areas where cattle are already on stored
feed. While such protective actions might be required for periods up to 2 months at areas
near the accident site, such would not be the case at the greater distances which involve the
major portion of the area. Condemnation of milk is the protective action of last resort for
areas of very high contamination. As noted above, the farm value of milk is $0.30 per liter.
Thus, the condemnation of milk at the Emergency PAG for a 22.5°/50 mile sector would
have a cost of about $2 million for a month of protective action. Where 1-131 is the only
significant contaminant, whole milk can be diverted to manufactured products, such as
powdered milk, which can be stored to allow disappearance of the radioactivity. We do not
have cost figures for this action.
It is of interest to compare the arbitrary assumptions on land area used above to the
contamination resulting from the Windscale accident. (NB: This was not a power reactor of
the type presently used in the United States). According to Booker, the Windscale accident
resulted in milk values exceeding 0.015 uCi/1 at about 200 kilometers or 125 miles
36
-------
downwind (75). Milk contamination was estimated as exceeding 0.01 uCi/I over 16,700
km2 or 6*00 mi2. Thus, the WindscaJe accident resulted in contamination exceeding
the Preventive PAG over an area about 10 times greater than that assumed above. Protective
actions were taken at Windscale at milk concentrations of 0.1 uCi/1 (approximately
the Emergency PAG) and involved an area of about 520 km2 or 200 mi2 for periods
of 3-6 weeks.
5.3 COST-EFFECTIVENESS ANALYSIS
Cost-effectiveness analysis is defined as the economy with which a particular task may
be carried out.
The data available for this analysis was obtained with the cooperation of the Nuclear
Regulatory Commission. Briefly, the NRC employed the models cited in the Reactor Safety
Study (7) to evaluate the agricultural costs and cumulative dose commitment that could
occur under two accident conditions - a design basis for siting purposes and a PWR 7
accident (7). A typical reactor site in the northeastern United States was envisioned.
Unfortunately, the parameters employed are not directly comparable with the pathways and
dosimetric parameters associated with the PAG's. Nevertheless, a good indication of the
effects of taking a protective action (in this case the condemnation of milk) at specific
interdiction levels can be ascertained.
Figure 5 presents the agricultural costs at specific interdiction criteria. The costs are,
for the most part, associated with the market value of milk. The interdiction criteria are in
terms of rem to an infant thyroid. From Figure 3, it can be seen that costs drop rapidly
between 0.5 and 10 rem and more gradually after 20 rem. The ratio of costs for a design
basis accident (siting) to a PWR 7 remains constant.
I0»r-
a
•a
o
.•
•a
tfl
o
u
K
\
10'
(ding)
• PWR 7
101
10 20 30 40 SO
INTERDICTION CRITERIA (rem-thyroid)
Figure 3. Agricultural cost model accident.
37
60
-------
Figure b is a graph of the dose commitment for a design basis accident and a PWR 7
assuming protective action is initiated at specific interdiction levels. The dose commit-
ments are accrued via external as well as internal exposure (inhalation and ingestion).
Therefore, they do not exactly fit the situation described in the PAG's under consideration.
The dose commitment rises rapidly when the interdiction criteria are between 0.5 and 20
rem. The increase in dose commitment for a design basis accident is less rapid than for a
PWR 7. Hence, at or above an interdiction criteria of 20 rem, savings in radiation dose are
minimal compared to the savings accrued below 10 rem.
10* r-
—
3
UJ
10*
8
10-
o
a
10*
»
• PWR 7
I
I
I
I
10 20 30 40 SO
INTERDICTION CRITERIA (rwn-thyoid)
60
Figure 4. Dose commitment model accident.
5.* SUMMARY AND CONCLUSION
The milk concentration at which the population benefits (from dose avoided) equals the
direct costs of stored feed is equivalent to about one-third of the Preventive PAG for stron-
tium and to one-fiftieth or less for iodine-131 and cesium. If condemnation is based on
retail milk value, then the respective concentrations are about one-half and one-fiftieth of
the Emergency PAG. Unless the indirect costs of implementing protective actions are
significantly greater than the direct costs, it appears feasible to take protective actions at
the respective PAG level and to continue such action to avoid about 90 percent of the
projected dose for iodine and cesium. In the case of strontium contamination of milk, such
action is only cost beneficial until the concentration is about 30 percent of the PAG
response level.
Estimated costs of taking protective action within the Emergency Planning Zone (EPZ)
for a 22.5° Sector to 50 miles (about 500 mi2) is $2 million per month for condemnation
(farm milk value) and $0.2f million per month for use of stored feed. In the case of
•J
38
-------
atmospheric dispersed contamination, protective action may have to continue for 2 months
near the site.
The recommended approach is to place all cows on stored feed to prevent the
contamination of milk at significant levels, to divert iodine contaminated milk to
manufactured products that have a long shelf life to allow radioactive decay, and only
consider condemnation of milk exceeding the Emergency PAG. It appears chat doses co the
public can be limited to less than 10 percent of the Preventive PAG (or less then 0.15 rem
thyroid) by actions having direct costs of a few milion dollars for a significant accident.
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Draft
APPENDIX E
Protective Action Guides for the Intermediate Phase
(Relocation)
Background Information
-------
Contents
Page
E. 1 Introduction E-l
E.I.I Response Duration E-2
E.I.2 Source Term E-2
E.I.3 Exposure Pathways E-4
E.I.4 Response Scenario E-5
E.2 Considerations for Establishing PAGs for the Intermediate Phase.. E-7
E.2.1 Principles E-9
E.2.1.1 Cost/Risk Considerations E-10
E.2.1.2 Protection of Special Groups E-12
E.2.2 Federal Radiation Protection Guides E-14
E.3 Dose from Reactor Incidents E-15
E.4 Alternatives to Relocation E-17
E.5 Risk Comparisons E-18
E.6 Relocation PAG Recommendations E-21
E.7 Criteria for Reentry into the Restricted Zone E-23
References E-25
Figures
E-l Response Areas E-6
E-2 Time Frame of Response to a Major Nuclear Reactor Accident E-8
E-3 Cost of Avoiding Statistical Fatalities and Exposure
Rates Corresponding to Various Total First Year Doses E-13
ii
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Contents (continued)
Page
Figures
E-4 Average Lifetime Risk of Death from Whole Body Radiation Dose
Compared to the Average Risk of Accidental Death from Lifetime
(47 years) Occupation in Various Industries E-19
Tables
E-l Brief Descriptions Characterizing Nuclear Power Plant Accident
Types (SN-82) E-3
E-2 Release Quantities for Postulated Nuclear Reactor Accidents E-3
E-3 Annual Doses Corresponding to 5 Rem in 50 Years E-16
E-4 Measure of Lifetime Risk of Mortality from a Variety of Causes... E-20
E-5 Summary of Considerations for Selecting PAGs for Relocation E-22
E-6 Estimated Maximum Doses to Nonrelocated Persons E-24
iii
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Appendix E
Protective Action Guides for the Intermediate Phase
(Relocation)
Background Information
E.I Introduction
This Appendix provides background information for the choice of
Protective Action Guides (PAGs) for relocation and other protective
actions to reduce exposure to deposited radioactive materials during the
intermediate phase of the response to a nuclear incident. The resulting
PAGs and associated implementing guidance are provided in Chapters 4 and
7, respectively.
This analysis is based on the assumption that an airborne plume of
radioactive material has already passed over an area and left a deposit
of radioactive material behind, or that such material exists from some
other source, and that the public has already been either sheltered or
evacuated, as necessary, on the basis of PAGs for the early phase of a
nuclear incident, as discussed in Chapters 2 and 5. PAGs for subsequent
relocation of the public and other protective actions, as well as dose
limits for persons reentering the area from which the public is
relocated, are addressed in this Appendix.
We first set forth the assumptions used to derive information
pertinent to choosing the dose level at which relocation of the public is
appropriate. This is followed by an examination of information relevant
to this decision, and selection of the PAG for relocation. The Appendix
concludes with a brief discussion of the basis for dose limits for
persons temporarily reentering areas from which the public has been
relocated.
E-l
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E.I.I Response Duration
In order to decide whether to initiate relocation of the public from
specific areas it is necessary to predict the dose that would be
avoided. One factor in this prediction is the duration of the exposure
to be avoided. Relocation can begin as soon as patterns of exposure from
deposited radioactivity permit restricted areas to be identified. For
the purpose of this analysis, relocation of persons who have not already
been evacuated from the restricted zone is assumed to take place on the
fourth day after the incident. Return of evacuated persons to their
residences outside the restricted zone and transition to relocation
status of persons already evacuated is assumed to occur over a period of
a week or more.
The period of exposure avoided by relocation ends when the relocated
person either returns to his property or is permanently resettled in a
new location. At the time of relocation decisions, it will usually not
be possible to predict when either of these actions will occur.
Therefore, for convenience of dose projection, it is assumed that the
period of exposure avoided is one year and that any extension beyond this
period will be determined on the basis of recovery criteria. This
assumption corresponds to emergency response planning guidance by ICRP
(IC-84) and IAEA (IA-85).
E.I.2 Source Term
The "source term" for this analysis is comprised of the quantities
and types of particulate radioactive material found in the environment
following a nuclear incident. Nuclear incidents can be postulated with a
wide range of release characteristics. The characteristics of the source
terms assumed for the development of these PAGs are those postulated for
releases from various types of fuel-melt accidents at nuclear power
plants (SN-82). Table E-l provides brief descriptions of these accident
types. Radionuclide releases have been estimated for the three most
severe accident types (SST-1, SST-2, SST-3) based on postulated core
inventories and release fractions (Table E-2). The other types (SST-4
E-2
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Table E-l Brief Descriptions Characterizing Various Nuclear Power Plant
Accident Types (SN-82)
Type
Description
SST-1 Severe core damage. Essentially involves loss of all installed
safety features. Severe direct breach of containment.
SST-2 Severe core damage. Containment fails to isolate. Fission
product release mitigating systems (e.g., sprays, suppression
pool, fan coolers) operate to reduce release.
SST-3 Severe core damage. Containment fails by base-mat melt-
through. All other release mitigation systems function as
designed.
SST-4 Modest core damage. Containment systems operate in a degraded
mode.
SST-5 Limited core damage. No failures of engineered safety features
beyond those postulated by the various design basis accidents.
The most severe accident in this group assumes that the
containment functions as designed.
Table E-2 Release Quantities for Postulated Nuclear Reactor Accidents
Principal
radionuclides
contributing
to dose from
deposited
materials
Zr-95
Nb-95
Ru-103
Ru-106
Te-132
1-131
CS-134
CS-137
Ba-140
La-140
Half-life
(days)
6.52E+1
3.50E+1
3.95E+1
3.66E+2
3.25
8.05
7.50E+2
1.10E+4
1.28E+1
1.67
Estimated
SST-1
1.4E+6
1.3E+6
6.0E+6
1.5E+6
8.3E+7
3.9E+7
8.7E+6
4.4E+6
1.2E+7
1.5E+6
quantity released3
(Curies)
SST-2
4.5E+4
4.2E+4
2.4E+5
5.8E+4
3.9E+6
2.6E+5
1.2E+5
5.9E+4
1.7E+5
5.1E+4
SST-3
1.5E+2
1.4E+2
2.4E+2
5.8E+1
2.6E+3
1.7E+4
1.3E+2
6.5En
1.7E+2
1.7E+2
a Based on the product of reactor inventories of radionuclides and
estimated fractions released for three accident categories (SN-82).
E-3
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and SST-5) would generally not produce offsite doses from exposure to
deposited material sufficient to warrant consideration of relocation.
For other types of source terms, additional analysis may be
necessary to assure adequate protection. For example, if the release
includes a large proportion of long-lived radionuclides, doses will
continue to be delivered over a long period of time and, if no remedial
actions are taken, the dose delivered in the first year may represent
only a small portion of the total dose delivered over a lifetime. On the
other hand, if the release consists primarily of short-lived
radionuclides, almost the entire dose may be delivered within the first
year.
From the data in Table E-2, it is apparent that, for the groups of
accidents listed, both long and short lived radionuclides would be
released. Consequently, doses due to deposited materials from such
accidents would be relatively high during the first year followed by long
term exposures at lower rates.
E.I.3 Exposure Pathways
The principal exposure pathway to members of the public occupying
land contaminated by deposits of radioactive materials from reactor
incidents is expected to be exposure of the whole body to external gamma
radiation. Although it is normally expected to be of only minor
importance, the inhalation pathway would contribute additional doses to
internal organs. The health risks from other pathways, such as beta dose
to the skin and direct ingestion of dirt, are also expected to be minor
in comparison to the risks due to external gamma radiation (AR-89). Skin
and inhalation dose would, however, be important exposure pathways for
source terms with significant fractions of pure beta emitters, and
inhalation dose would be important for source terms with significant
fractions of alpha emitters.
Since relocation, in most cases, would not be an appropriate action
to prevent radiation exposure from ingestion of food and water, these
E-4
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exposure pathways have not been included in this analysis. They are
addressed in Chapters 3 and 6. In some instances, however, where
withdrawal of food and/or water from use would, in itself, create a
health risk, relocation may be an appropriate alternative protective
action. In this case, the committed effective dose equivalent from
ingest ion should be added to the projected dose from deposited
radionuclides via other pathways, for decisions on relocation.
E.I.4 Response Scenario
This section defines the response zones, population groups, and the
activities assumed for implementation of protective actions during the
intermediate phase.
After passage of the radioactive plume, the results of environmental
monitoring will become available for use in making decisions to protect
the public. Sheltering, evacuation, and other actions taken to protect
the public from the plume will have already been implemented. The tasks
immediately ahead will be to (1) define the extent and characteristics of
deposited radioactive material and identify a restricted zone in
accordance with the PAG for relocation, (2) relocate persons from and
control access to the restricted zone, (3) allow persons to return to
areas outside the restricted zone, (4) control the spread of and exposure
to surface contamination, and (5) apply simple decontamination and other
low-cost, low-risk techniques to reduce the dose to persons who are not
relocated.
Because of the various source term characteristics and the different
protective actions involved (evacuation, sheltering, relocation,
decontamination, and other actions to reduce doses to "as low as
reasonably achievable" levels), the response areas for different
protective actions may be complex and may vary in size with respect to
each other. Figure E-l shows a generic example of some of the principle
areas involved. The area covered by the plume is assumed to be
represented by area 1. In reality, variations in meteorological
conditions would almost certainly produce a more complicated shape.
E-5
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PLUME TRAVEL
DIRECTION
LEGEND
| | 1. PLUME DEPOSITION AREA.
L-J
2. AREA FROM WHICH POPULATION IS EVACUATED.
3. AREA IN WHICH POPULATION IS SHELTERED.
4. AREA FROM WHICH POPULATION IS RELOCATED (RESTRICTED ZONE).
FIGURE E-1. RESPONSE AREAS.
-------
Based on plant conditions or other considerations prior to or after
the release, members of the public are assumed to have already been
evacuated from area 2 and sheltered in area 3. Persons who were
evacuated or sheltered as a precautionary action for protection from the
plume but whose homes are outside the plume deposition area (area 1) are
assumed to return to their homes or discontinue sheltering when
environmental monitoring verifies the outer boundary of area 1.
Area 4 is the restricted zone and is defined as the area where
projected doses are equal to or greater than the relocation PAG. The
portion of area 1 outside of area 4 is designated as a study zone and is
assumed to be occupied by the public. However, contamination levels may
exist here that would be of concern for continued monitoring and
decontamination to maintain radiation doses "as low as reasonably
achievable" (ALARA).
The relative positions of the boundaries shown in Figure E-l are
dependent on areas evacuated and sheltered. For example, area 4 could
fall entirely inside area 2 (the area evacuated) so that relocation of
persons from additional areas would not be required. In this case
relocation PAG would be used only to determine areas to which evacuees
could return.
Figure E-2 provides, for perspective, a schematic representation of
the response activities expected to be in progress in association with
implementation of the PAGs during the intermediate phase of the response
to a nuclear incident.
E.2 Considerations for Establishing PAGs for the Intermediate Phase
The major considerations in selecting values for these PAGs for
relocation and other actions during the intermediate phase are the four
principles that form the basis for selecting all PAGs. Those are
discussed in Section E.2.1. Other considerations (Federal radiation
protection guidance and risks commonly confronting the public) are
discussed in Sections E.2.2 and E.5.
E-7
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I I I I I I III I I I I 11111 I I I I 11 111 I I ITTTTTI
w
EC
O
O
O
LJJ
I
o
PERIOD OF
RELEASE,
DISPERSION,
DEPOSITION,
SHELTERING,
o
UJ
UJ
_i
o_
5
O
O
EVACUATION, 55
AND ACCESS
CONTROL
(NO TIME SCALE)
O
g]
Q
CONDUCT AERIAL AND GROUND SURVEYS. DRAW ISODOSE RATE LINES.
IDENTIFY HIGH DOSE RATE AREAS. CHARACTERIZE CONTAMINATION.
RELOCATE POPULATION FROM HIGH DOSE RATE AREAS.
ALLOW IMMEDIATE RETURN OF EVACUEES TO NONCONTAMINATED AREAS.
ESTABLISH RESTRICTED ZONE BOUNDARY AND CONTROLS.
RELOCATE REMAINING POPULATION FROM WITHIN RESTRICTED ZONE.
GRADUALLY RETURN EVACUEES UP TO RESTRICTED ZONE BOUNDARY.
CONDUCT D-CON AND SHIELDING EVALUATIONS AND ESTABLISH PROCEDURES
FOR REDUCING EXPOSURE OF PERSONS WHO ARE NOT RELOCATED.
PERFORM DETAILED ENVIRONMENTAL MONITORING.
PROJECT DOSE BASED ON DATA.
DECONTAMINATE ESSENTIAL FACILITIES AND THEIR ACCESS ROUTES.
RETRIEVE VALUABLE AND ESSENTIAL RECORDS AND POSSESSIONS.
REESTABLISH OPERATION OF VITAL SERVICES.
BEGIN RECOVERY ACTIVITIES.
CONTINUE RECOVERY.
MONITOR AND APPLY
ALARA IN OCCUPIED
CONTAMINATED AREAS.
I I I I Mill I I I I INI
I I I I Mill I I I I Mill
0.1
1.0 10 100
TIME AFTER DEPOSITION (DAYS)
1,000
FIGURE E-2. POTENTIAL TIME FRAME OF RESPONSE TO A NUCLEAR INCIDENT.
-------
In addition, a planning group consisting of State, Federal, and
industry officials provided recommendations in 1982 which EPA considered
in the development of the format, nature, and applicability of PAGs for
relocation. Abbreviated versions of these recommendations are as follows:
a. The PAGs should apply to commercial, light-water power reactors.
b. The PAGs should be based primarily on health effects.
c. Consideration should be given to establishing a range of PAG
values.
d. The PAGs should be established as high as justifiable because at
the time of the response, it would be possible to lower them, if
justified, but it probably would not be possible to increase them.
e. Only two zones (restricted and unrestricted) should be
established to simplify implementation of the PAGs.
f. The PAGs should not include past exposures.
g. Separate PAGs should be used for ingestion pathways.
h. PAGs should apply only to exposure during the first year after an
incident.
Although these PAGs apply to any nuclear incident, primary
consideration was given to the case of commercial U.S. reactors. In
general, we have found it possible to accommodate most of the above
recommendations.
E.2.1 Principles
In selecting values for these PAGs, EPA has been guided by the
principles that were set forth in Chapter 1. They are repeated here for
convenience:
E-9
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1. Acute effects on health (those that would be observable within a
short period of time and which have a dose threshold below which
they are not likely to occur) should be avoided.
2. The risk of delayed effects on health (primarily cancer and
genetic effects, for which linear nonthreshold relationships to
dose are assumed) should not exceed upper bounds that are judged
to be adequately protective of public health, under emergency
conditions, and are reasonably achievable.
3. PAGs should not be higher than justified on the basis of
optimization of cost and the collective risk of effects on
health. That is, any reduction of risk to public health
achievable at acceptable cost should be carried out.
4. Regardless of the above principles, the risk to health from a
protective action should not itself exceed the risk to health
from the dose that would be avoided.
Appendix B analyzed the risks of health effects as a function of
dose (Principles 1 and 2). Considerations for selection of PAGs for the
intermediate phase of a nuclear incident differ from those for selection
of PAGs for the early phase primarily with regard to implementation
factors (i.e., Principles 3 and 4). Specifically, they differ with
regard to cost of avoiding dose, the practicability of leaving infirm
persons and prisoners in the restricted zone, and avoiding dose to
fetuses. Although sheltering is not generally a suitable alternative to
relocation, other alternatives (e.g., decontamination and shielding) are
suitable. These considerations are reviewed in the sections that follow.
E.2.1.1 Cost/Risk Considerations
The Environmental Protection Agency has issued guidelines for
internal use in for performing regulatory impact analyses (EP-83). These
include consideration of the appropriate range of costs for avoiding a
statistical death. The values are inferred from the additional
E-10
-------
compensation associated with employment carrying a higher than normal
risk of mortality, and is expressed as a range of $0.4 to $7 million per
statistical death avoided. The following discussion compares these
values to the cost of avoiding radiation-induced fatal cancers through
relocation.
The basis for estimating the societal costs of relocation are
analyzed in a report by Bunger (BU-89). Estimated incremental societal
costs per day per person relocated are shown below. (Moving and loss of
inventory costs are averaged over one year.)
Moving J1.70
Loss of use of residence 2.96
Maintain and secure vacated property 0.74
Extra living costs 1.28
Lost business and inventories 14.10
Extra travel costs 4.48
Idle government facilities 1.29
Total
The quantity of interest is the dose at which the value of the risk
avoided is equal to the cost of relocation. Since the above costs are
expressed in dollars/person-day, it is convenient to calculate the dose
that must be avoided per-person day. The equation for this is:
H -!-
E ~ VR
where:
HE = dose (rem/day)
C = cost of relocation (dollars/day).
V = value of avoiding a statistical death (dollars/death)
R = statistical risk of death from radiation dose (deaths/rem)
_4
Using the values cited above, and a value for R of 3x10 deaths/rem
(See Appendix B), one obtains a range of doses of about 0.01 to 0.2 rem/day.
Thus, over a period of one year the total dose that should be avoided to
justify the cost of relocation would be about 5 to 80 rem.
E-ll
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These doses are based on exposure accumulated over a period of one
year. However, exposure rates decrease with time due to radioactive decay
and weathering. Thus, for any given cumulative dose in the first year, the
daily exposure rate continually decreases, so that a relocated person will
avoid dose more rapidly in the first part of the year than later. Figure
E-3 shows the effect of changing exposure rate on the relationship between
the cost of avoiding a statistical death and the time after an SST-2
accident (See Table E-l) for several assumed cumulative annual doses. The
curves represent the cost per day divided by the risk of fatality avoided by
relocation per day, at time t, for the annual dose under consideration,
where t is the number of days after the accident. The right ordinate shows
the gamma exposure rate (mR/h) as a function of time for the postulated
radionuclide mix at one meter height.
The convex downward curvature results from the rapid decay of
short-lived radionuclides during the first few weeks following the
accident. Since the cost per day for relocation is assumed to be constant
and the dose avoided per day decreases, the cost effectiveness of relocation
decreases with time. For this reason it is cost effective to quickly
recover areas where the population has been relocated at projected doses
only marginally greater than the PAG.
Only trends and general relationships can be inferred from Figure E-3
because it applies to a specific mix of radionuclides. However, for this
radionuclide mix, cost analysis supports relocation at doses as low as one
rem for the first week and two rem for up to 25 days after an accident.
E.2.1.2 Protection of Special Groups
Contrary to the situation for evacuation during the early phase of an
incident, it is generally not practical to leave a few persons behind when
most members of the general population have been relocated from a specified
area for extended periods of time. Further, no data are available on
differing risks of relocation for different population groups. In the
absence of such data, we have assumed that these risks will be similar to
E-12
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0.2
0.3
0.4
0.5
0.6
0.7
0.8 uj
O
0.9
1.0
6
7
8
9
10
20
30
40
10 15 20
TIME AFTER ACCIDENT (days)
25
30
FIGURE E-3. COST OF AVOIDING STATISTICAL FATALITIES AND
EXPOSURE RATES CORRESPONDING TO VARIOUS
TOTAL FIRST YEAR DOSES (ASSUMES AN SST-2
ACCIDENT AND A $27 PER PFRSON-DAY COST OF
RELOCATION).
E-13
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those from evacuation. Those risks were taken as equivalent to the health
risk from doses of 30 mrem for members of the general population and of 150
mrem for persons at high risk from evacuation (see Appendix C). Therefore,
to satisfy Principle 4 for population groups at high risk, the PAG for
relocation should not be lower than 150 millirem. Given the arbitrary nature
of this derivation, it is fortunate that this value is much lower than the
PAG selected, and is therefore not an important factor in its choice.
Fetuses are a special group at greater risk of health effects from
radiation dose than is the general population, but not at significantly
greater risk from relocation itself. The risk of mental retardation from
fetal exposure (see Appendix 8) is significant. It is affected by the stage
of pregnancy relative to the assumed one-year exposure, because the 8th to
15th week critical period during which the risk is greatest, must be
considered in relation to the rapidly changing dose rate. Taking these
factors into account, it can be postulated that the risk of mental
retardation due to exposure of the fetus during the intermediate phase will
range from one to five times the cancer risk of an average member of the
public, depending upon when conception occurs relative to the time of the
incident. The elevated risk of radiation-induced cancer from exposure of
fetuses is less significant, as discussed in Appendix B.
It will usually be practicable to reduce these risks by establishing a
high priority for efforts other than relocation to reduce the dose in cases
where pregnant women reside near the boundary of the restricted zone.
However, women who are less than seven months pregnant may wish to relocate
for the balance of their pregnancy if the projected dose during pregnancy
cannot be reduced below 0.5 rem.
E.2.2 Federal Radiation Protection Guides
The choice of a PAG at which relocation should be implemented does not
mean that persons outside the boundary of the restricted zone should not be
the subject of other protective actions to reduce dose. Such actions are
justified on the basis of existing Federal radiation protection guidance
E-14
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(FR-65) for protecting the public, including implementation of the
principle of maintaining doses "as low as reasonably achievable"
(ALARA).
The intended actions to protect the public from radiation doses
on the basis of Radiation Protection Guides (RPGs) are those related to
source control. Although it is reasonable for members of the public to
receive higher exposure rates prior to the source term being brought under
control, the establishment of acceptable values for relocation PAGs must
include consideration of the total dose over the average remaining
lifetime of exposed individuals (usually taken as 50 years).
The nationally and internationally recommended upper bound for
dose in a single year from man-made sources, excluding medical radiation,
is 500 mrem per year to the whole body of individuals in the general
population (IC-77, FR-65). These recommendations were not developed for
nuclear incidents. They are also not appropriate for chronic exposure.
The ICRP recommends an upper bound of 100 mrem per year, from all sources
combined, for chronic exposure (IC-77). The corresponding 50-year dose at
100 mrem/yr is 5 rem. We have chosen to limit a) the projected first
year dose to individuals from an incident to the Relocation PAG, b) the
projected second year dose to 500 mrem, and c) the dose projected over a
fifty-year period to 5 rem. Due to the extended duration of exposures and
the short half-life of important radioiodines, no special limits for
thyroid dose are needed.
E.3. Dose from Reactor Incidents
Doses from an environmental source will be reduced through the
natural processes of weathering and radioactive decay, and from the
shielding associated with part time occupancy in homes and other
structures. Results of dose calculations based on the radiological
characteristics of releases from three categories of postulated,
fuel-melt, reactor accidents (SST-1, SST-2, and SST-3) (SN-82) and
a weathering model from WASH-1400 (NR-75) are shown in Table E-3.
E-15
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This table shows the relationship between annual doses for the case
where the sum, over fifty years, of the effective dose equivalent
from gamma radiation and the committed effective dose equivalent from
inhalation of resuspended materials, is 5 rem. Radioactive decay and
weathering reduces the second year dose from reactor incidents to 20 to 40
percent of the first year dose, depending on the radionuclide mix in the
release.
Table E-3 Annual Doses Corresponding to 5 Rem in 50 Years3
Year
c
Dose According to Accident Category
SST-l(rem) SST-2(rem) SST-3(rem)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1.25
0.52
0.33
0.24
0.18
0.14
0.12
0.10
0.085
0.080
0.070
0.060
0.060
0.055
0.055
0.050
1.60
0.44
0.28
0.20
0.16
0.12
0.11
0.085
0.075
0.070
0.060
0.055
0.055
0.050
0.045
0.045
1.91
0.38
0.24
0.17
0.13
0.11
0.090
0.070
0.065
0.060
0.050
0.050
0.045
0.040
0.040
0.040
aWhole body dose equivalent from gamma radiation plus committed
effective dose equivalent from inhalation assuming a resuspension factor
of 10~6 nr1. Weathering according to the WASH-1400 model (NR-75)
and radioactive decay are assumed.
bRadionuclide abundance ratios are based on reactor inventories from
WASH-1400 (NR-75). Release quantities for accident categories SST-1,
SST-2 and SST-3 are shown in Table E-2. Initial concentrations are
assumed to have decayed for 4 days after reactor shutdown.
cAnnual doses after 16 years would be less than 0.05 rem.
E-16
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Based on studies reported in WASH-1400 (NR-75), the most conservative
dose reduction factor for structures (frame structures) is about 0.4 (dose
inside divided by dose outside) and the average fraction of time spent in a
home is about 0.7. Combining these factors yields a net dose reduction
factor of about 0.6. In most cases, therefore, structural shielding would
be expected to reduce the dose to persons who are not relocated to 60
percent (or less) of the values shown in Table E-3 before the application
of decontamination.
E.4 Alternatives to Relocation
Persons who are not relocated, in addition to dose reduction provided
by partial occupancy in homes and other structures, can reduce their dose
by the application of various techniques. Dose reduction efforts can range
from the simple processes of scrubbing and/or flushing surfaces, soaking or
plowing of soil, removal and disposal of small spots of soil found to be
highly contaminated (e.g., from settlement of water), and spending more
time than usual in lower exposure rate areas (e.g., indoors), to the
difficult and time consuming processes of removal, disposal, and
replacement of contaminated surfaces. It is anticipated that simple
processes would be most appropriate to reduce exposure rates for persons
living in contaminated areas outside the restricted zone. Many of these
can be carried out by the residents with support from officials for
monitoring, guidance on appropriate actions, and disposal. The more
difficult processes will usually be appropriate for recovery of areas from
which the population is relocated.
Decontamination experiments involving radioactive fallout from nuclear
weapons tests have shown reduction factors for simple decontamination
methods in the vicinity of 0.1 (i.e., exposure rate reduced to 10 percent
of original values). However, recent experiments at the Riso National
Laboratory in Denmark (WA-82, WA-84), using firehoses to flush asphalt and
concrete surfaces contaminated with radioactive material of the type that
might be deposited from reactor accidents, show decontamination factors for
radionuclides chemically similar to cesium that are in the range of 0.5 to
0.95, depending on the delay time after deposition before flushing is
E-17
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applied. The factor for ruthenium on asphalt was about 0.7 and was
Independent of the delay of flushing. The results of these experiments
indicate that decontamination of the important reactor fission products
from asphalt or concrete surfaces may be much more difficult than
decontamination of nuclear weapons fallout. Other simple dose reduction
methods listed above would be effective to varying degrees. The average
dose reduction factor for gamma radiation from combinations of simple
decontamination methods is estimated to be at least 0.7. Combining this
with the 40 percent reduction estimated above for structural shielding
indicates that the doses listed in Table E-3 may be more than twice as high
as those which would actually be received by persons who are not relocated.
E.5 Risk Comparisons
Many hazardous conditions and their associated risks are routinely
faced by the public. A lingering radiation dose will add to those risks,
as opposed to substituting one risk for another, and, therefore, radiation
protection criteria cannot be justified on the basis of the existence of
other risks. It is, however, useful to review those risks to provide
perspective. This section compares the risks associated with radiation
doses to those associated with several other risks to which the public is
commonly exposed.
Figure E-4 compares recent statistics for the average lifetime risk of
accidental death in various occupations to the estimated lifetime risk of
fatal cancer for members of the general population exposed to radiation
doses ranging up to 25 rem. Non-radiation risk values are derived from
information in reference (EP-81) and radiation risk values are from
Appendix 6. These comparisons show, for example, that the lifetime cancer
risk associated with a dose of 5 rem is comparable to the lifetime risk of
accidental death in some of the safest occupations, and is well below the
average lifetime risk of accidental death for all industry.
Risks of health effects associated with radiation dose can also be
compared to other risks facing individuals in the general population. The
risks listed in Table E-4 are expressed as the number of premature deaths
E-18
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10
-2
UJ
0
UJ
oc
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•CONSTRUCTION & MINING
AGRICULTURE
-TRANSPORTATION & PUBLIC UTILITIES
AVERAGE FOR ALL UTILITIES
•GOVERNMENT
.SERVICE
MANUFACTURING
• RETAIL &
WHOLESALE.
TRADE
25 rem
•5 rem
•1 rem
•0.5 rem
I I
I
I
I
I
I
8 10 12 14 16 18
rem (effective dose equivalent)
20 22 24 26
FIGURE E-4. AVERAGE LIFETIME RISK OF DEATH FROM WHOLE BODY RADIATION DOSE
COMPARED TO THE AVERAGE RISK OF ACCIDENTAL DEATH FROM LIFETIME
(47 YEARS) OCCUPATION IN VARIOUS INDUSTRIES.
E-19
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Table E-4 Measure of Lifetime Risk of Mortality from a Variety of Causes3
(Cohort Size = 100,000)
Aggregate years Reduction of Average years
Nature of Premature of life lost life expectancy of life lost to
accident deaths to cohort at birth (years) premature deaths
Falls
Fires
Drowning
Poisoning
by drugs and
medicaments
1,000
300
190
69
12,000
7,600
8,700
2,500
0.12
0.076
0.087
0.025
11
26
45
37
Cataclysm13
Bites and
stings0
Electric
current
in homes^
17
8
490
220
290
0.005
0.002
0.003
30
27
37
aAll mortality effects shown are calculated as changes from the U.S. Life
Tables for 1970 to life tables with the cause of death under investigation
removed. These effects also can be interpreted as changes in the opposite
direction, from life tables with the cause of death removed to the 1970
Life Table. Therefore, the premature deaths and years of life lost are
those that would be experienced in changing from an environment where the
indicated cause of death is not present to one where it is present. All
values are rounded to no more than two significant figures.
^Cataclysm is defined to include cloudburst, cyclone, earthquake, flood,
hurricane, tidal waves, tornado, torrential rain, and volcanic eruption.
cAccidents by bite and sting of venomous animals and insects include bites
by centipedes, venomous sea animals, snakes, and spiders; stings of bees,
insects, scorpions, and wasps; and other venomous bites and stings. Other
accidents caused by animals include bites by any animal and nonvenomous
insect; fallen on by horse or other animal; gored; kicked or stepped on by
animal; ant bites; and run over by horse or other animal. It excludes
transport accidents involving ridden animals; and tripping, falling over an
animal. Rabies is also excluded.
^Accidents caused by electric current from home wiring and appliances
include burn by electric current, electric shock or electrocution from
exposed wires, faulty appliances, high voltage cable, live rail, and open
socket. It excludes burn by heat from electrical appliances and lighting.
E-20
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and the average reduction of life-span due to these deaths within a group
of 100,000 persons. For purposes of comparison, a dose of 5 rem to each
member of a population group of 100,000 persons representative of the
average U.S. population carries an estimated lifetime risk of about 150
fatal cancers (see Appendix 8). The number of deaths resulting from the
various causes listed in Table E-4 is based on data from mortality
records.
In summary, the risk of premature death normally confronting the
public from specific types of accidents ranges from about 2 to 1000 per
100,000 population. The estimated radiation doses required to produce a
similar risk of death from radiation-induced cancer range from about 0.07
to 33 rem.
E.6 Relocation PAG Recommendations
Previous sections have reviewed data, standards, and other
information relevant to establishing PAGs for relocation. The results are
summarized in Table E-5, in relation to the principles set forth in
Section E.2.1.
Based on the avoidance of acute effects alone (Principle 1) 50 rem
and 10 rem are upper bounds on the dose at which relocation of the general
population and fetuses, respectively, is justified. However, on the basis
of control of chronic risks (Principle 2) a lower upper bound is
appropriate. Five rem is taken as an upper bound on acceptable risk for
controllable lifetime exposure to radiation, including avoidable exposure
to accidentally deposited radioactive materials. This corresponds to an
average of 100 mrem per year for fifty years, a value commonly accepted as
an upper bound for chronic annual exposure of members of the public from
all sources of exposure combined, other than natural background and
medical radiation (IC-77). In the case of projected doses from nuclear
reactor accidents, a five rem lifetime dose corresponds to about 1.25 to
2 rem from exposure during the first year and 0.4 to 0.5 rem from exposure
during the second year.
E-21
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Table E.5 Summary of Considerations for Selecting PAGs for Relocation
Dose
(rem) Consideration Principle
50 Assumed threshold for acute health effects in adults. 1
10 Assumed threshold for acute health effects in the
fetus. 1
6 Maximum projected dose in first year to meet 0.5 rem 2
in the second year3.
5 Maximum acceptable annual dose for normal
occupational exposure of adults. 2
5 Minimum dose that must be avoided by
one year relocation based on cost. 3
3 Minimum projected first-year dose corresponding
to 5 rem in 50 years3. 2
3 Minimum projected first-year dose corresponding
to 0.5 rem in the second year3. 2
2 Maximum dose in first year corresponding to
5 rem in 50 years from a reactor incident,
based on radioactive decay and weathering only. 2
1.25 Minimum dose in first year corresponding to 5 rem
in 50 years from a reactor incident based on
radioactive decay and weathering only. 2
0.5 Maximum acceptable single-year dose to the
general population from all sources from
non-recurring, non-incident exposure. 2
0.5 Maximum acceptable dose to the fetus from
occupational exposure of the mother. 2
0.1 Maximum acceptable annual dose to the general
population from all sources due to routine (chronic),
non-incident, exposure. 2
0.03 Dose that carries a risk assumed to be equal to
or less than that from relocation. 4
aAssumes the source term is from a reactor incident and that simple
dose reduction methods are applied during the first month after the
incident to reduce the dose to persons not relocated from contaminated
areas.
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Analyses based on Principle 3 (cost/risk) indicate that considering cost
alone would not drive the PAG to values less than 5 rem. Analyses in
support of Principle 4 (risk of the protective action itself) provide a
lower bound for relocation PAGs of 0.15 rem.
Based on the above, 2 rem projected committed effective dose equivalent
from exposure in the first year is selected as the PAG for relocation.
Implementation of relocation at this value will provide reasonable assurance
that, for a reactor accident, a person relocated from the outer margin of
the relocation zone will, by such action, avoid an exposure rate which, if
continued over a period of one year, would result in a dose of about 1.2 rem.
This assumes that 0.8 rem would be avoided without relocation through normal
partial occupancy of homes and other structures. This PAG will provide
reasonable assurance that persons outside the relocation zone, following a
reactor accident, will not exceed 1.2 rem in the first year, 0.5 rem in the
second year, and 5 rem in 50 years. The implementation of simple dose
reduction techniques, as discussed in section E-4, will further reduce dose
to persons who are not relocated from contaminated areas. Table E-6
summarizes the estimated maximum dose that would be received by these
persons for various reactor accident categories with and without the
application of simple dose reduction techniques. In the case of non-reactor
accidents these doses will, in general, differ, and it may be necessary to
apply more restrictive PAGs to the first year in order to assure conformance
to the second year and lifetime objectives noted above.
Since effective dose does not include dose to the skin (and for other
reasons discussed in Appendix B) protective action to limit dose to skin is
recommended at a skin dose 50 times the numerical value of the PAG for
effective dose. This includes consideration of the risk of both curable and
fatal cancers.
E.7 Criteria for Reentry into the Restricted Zone
Persons may need to reenter the restricted zone for a variety of
reasons, including radiation monitoring, recovery work, animal care,
property maintenance, and factory or utility operation. Some persons
E-23
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outside the restricted zone, by nature of their employment or habits, may
also receive higher than average radiation doses. Tasks that could cause
such exposures include, 1) changing of filters on air handling equipment
(including vehicles), 2) handling and disposal of contaminated vegetation
(e.g., grass and leaves) and, 3) operation of control points for the
restricted zone.
Individuals who reenter the restricted zone or who perform tasks
involving exposure rates that would cause their radiation dose to exceed
that permitted by the PAGs should do so in accordance with existing Federal
radiation protection guidance for occupationally exposed workers (EP-87).
The basis for that guidance has been provided elsewhere (EP-87)
Table E-6 Estimated Maximum Doses to Nonrelocated Persons From Areas Where
the Projected Dose is 2 REMa
Dose (rem)
Accident
Category
SST-1
SST-2
SST-3
No
addi
Year 1
1
1
1
.2
.2
.2
tional dose
Year 2
0.5
0.34
0.20
reduction
50
5
3
3
years
.0
.9
.3
Early
Year 1
0.9
0.9
0.9
simple dose
Year 2
0.35
0.24
0.14
reduction^
50
3
2
2
years
.5
.7
.3
aBased on relocation at a projected dose of 2 rem in the first
year and 40 percent dose reduction to nonrelocated persons from normal,
partial occupancy in structures. No dose reduction is assumed from
decontamination, shielding, or special limitations on time spent in high
exposure rate areas.
bThe projected dose is assumed to be reduced 30 percent by the
application of simple dose reduction techniques during the first month.
If these techniques are completed later in the first year, the first year
dose will be greater.
E-24
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REFERENCES
AR-89 AABERG, ROSANNE, Battelle Northwest Laboratories. Evaluation of
Skin and Ingestion Exposure Pathways. U.S. Environmental
Protection Agency/Office of Radiation Programs, Washington,
D.C. 20460 (1989 in press).
BU-89 8UNGER, BYRON M., Cost of Relocation. U.S. Environmental
Protection Agency/Office of Radiation Programs. Washington,
D.C. 20460. 1989 (draft).
EP-81 U.S. ENVIRONMENTAL PROTECTION AGENCY. Background Report.
Proposed Federal Radiation Protection Guidance for Occupational
Exposure. EPA 520/4-81-003. U.S. Environmental Protection
Agency/Office of Radiation Programs. Washington, D.C. 20460.
January, 1981.
EP-83 U.S. ENVIRONMENTAL PROTECTION AGENCY, Office of Policy
Analysis. Guidelines for Performing Regulatory Impact Analysis,
EPA-23-01-84-003. U.S. Environmental Protection Agency,
Washington, DC 20460. December 1983.
EP-87 U.S. ENVIRONMENTAL PROTECTION AGENCY. Radiation Protection
Guidance to Federal Agencies for Occupational Exposure. Federal
Register. Vol. 52, No. 17, p. 2822, U.S. Government Printing
Office, Washington, DC 20402..January 27, 1987.
FR-65 FEDERAL RADIATION COUNCIL. Radiation Protection Guidance for
Federal Agencies. Federal Register, Volume 30, pp. 6953-6955,
U.S. Government Printing Office, Washington, DC 20402, May 22,
1965.
IA-85 INTERNATIONAL ATOMIC ENERGY AGENCY. Principles for Establishing
Intervention Levels for Protection of the Public in the Event of
a Nuclear Accident or Radiological Emergency, Safety Series
No.72, International Atomic Energy Agency, Vienna, 1985.
IC-77 INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION.
Radiological Protection. ICRP Publication 26, Pergamon Press,
Oxford, England, January 1977.
IC-84 INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION. Protection
of the Public in the Event of Major Radiation Accidents:
Principles for Planning, ICRP Publication 40, Pergamon Press,
New York, 1984.
NR-75 U.S. NUCLEAR REGULATORY COMMISSION. Calculations of Reactor
Accident Consequences, WASH-1400, U.S. Nuclear Regulatory
Commission, Washington, DC 20555, October 1975.
E-25
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SN-82 SANDIA NATIONAL LABORATORIES. Technical Guidance for Siting
Criteria Development, NUREG/CR-2239, U.S. Nuclear Regulatory
Commission, Washington, DC 20555, December 1982.
WA-82 WARMING, L. Weathering and Decontamination of Radioactivity
Deposited on Asphalt Surfaces, Riso-M-2273, Riso National
Laboratory, DK 4000 Roskilde, Denmark, December 1982.
WA-84 WARMING, L. Weathering and Decontamination of Radioactivity
Deposited on Concrete Surfaces. RISO-M-2473. Riso National
Laboratory, DK-4000 Roskilde, Denmark. December 1984.
E-26
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APPENDIX F
Radiation Protection Criteria
for the Late Phase
Background Information
(Reserved)
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