[Federal Register Volume 59, Number 246 (Friday, December 23, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-31618]
[[Page Unknown]]
[Federal Register: December 23, 1994]
_______________________________________________________________________
Part III
Environmental Protection Agency
_______________________________________________________________________
Federal Radiation Protection Guidance for Exposure of the General
Public; Notice
ENVIRONMENTAL PROTECTION AGENCY
[FRL-5126-7]
RIN 2060-AE61
Federal Radiation Protection Guidance for Exposure of the General
Public
AGENCY: U.S. Environmental Protection Agency.
ACTION: Proposed recommendations, request for written comments, and
notice of public hearings.
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SUMMARY: The Agency is proposing to make recommendations to the
President for new guidance to Federal agencies on radiation protection
which would have two effects: it would cause a five-fold reduction in
the maximum allowable risk of cancer from any Federally regulated
activity involving nuclear materials or other sources of radiation; and
it would decrease the cost of Federal regulation of radiation by
promoting uniform treatment of radiation by all Federal agencies, and
reducing costly duplicative and conflicting requirements.
The new guidance would replace those portions of previous
recommendations that apply to protection of the general public,
approved by Presidents Eisenhower and Kennedy in 1960 and 1961,
respectively. New Federal guidance issued in 1987 replaced those
portions of the 1960 and 1961 guidance that applied to protection of
workers.
These proposed recommendations are based on a review of existing
guidance in light of current scientific understanding of the risks of
exposure to ionizing radiation and of the experience of Federal
agencies in its control. They include both qualitative guidance on
radiation protection and numerical guides for limiting radiation doses
to the general public. The most significant proposed changes are that:
the Radiation Protection Guide (RPG) be expressed in terms of a single
weighted sum of doses to organs, and the separate RPGs for individual
organs deleted; the current RPGs limiting the average genetic dose to
members of the U.S. population to 5 rems in 30 years and the annual
whole body dose to 500 millirem dose equivalent be replaced by a single
RPG of 1 millisievert (100 millirem) effective dose equivalent received
by or committed in a single year to any individual from all sources
combined; doses from individual sources normally be limited to a
fraction of the RPG; and increased emphasis be given to the principle
that all exposure should be maintained as low as reasonably achievable,
within the RPG.
The Agency invites written comments on these proposals and shall
also hold a public hearing, as discussed below. All written and oral
comments will be considered carefully in preparing our final
recommendations to the President.
DATES: Written comments in response to this notice of proposed guidance
must be received on or before February 21, 1995, to be ensured full
consideration. A public hearing will be held in Washington, D.C., on
February 22 and 23, 1995. Requests to participate should be received on
or before January 23, 1995. The schedule, location, and procedures for
this hearing will be published in the Federal Register shortly.
ADDRESSES: Written comments (in duplicate if possible) should be
submitted to: Central Docket Section Section (6102), Attn.: Docket No.
A-83-41, U.S. Environmental Protection Agency, Washington, DC 20460.
Written comments, the public hearing record, and other documents
related to this rulemaking will be filed under the above docket number
in Room M1500 at Waterside Mall, U.S. Environmental Protection Agency,
401 M Street, S.W., Washington, DC. The docket may be inspected between
8:00 a.m. and 4:00 p.m. on weekdays. A reasonable fee may be charged
for copying.
Requests to participate in the public hearing should be submitted
to Allan C. B. Richardson, Deputy Director for Federal Guidance,
Criteria and Standards Division, Office of Radiation and Indoor Air
(6602J), U.S. Environmental Protection Agency, Washington, D.C. 20460.
Requests to participate in the public hearing should include an outline
of the topics to be addressed, the amount of time requested, and the
names of the participants. EPA may allow testimony to be given at the
hearing without prior notice, subject to time constraints at the
discretion of the hearing officer.
FOR FURTHER INFORMATION CONTACT: Allan Richardson at the above address
(telephone (202) 233-9213; FAX (202) 233-9629) concerning these
proposed recommendations or the public hearing.
SUPPLEMENTARY INFORMATION:
Introduction
The Administrator of the Environmental Protection Agency (EPA) has
the responsibility 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 and in the establishment and execution of programs of
cooperation with States.'' This authority stems from Executive Order
10831; the Atomic Energy Act of 1954, as amended; and Reorganization
Plan No. 3 of 1970. Guidance to Federal agencies has historically
consisted of both qualitative and quantitative recommendations
expressed as ``Federal Radiation Protection Guidance.'' The guidance
proposed here would replace those portions of existing Federal
Radiation Protection Guidance, adopted in 1960 (25 FR 4402) and 1961
(26 FR 9057), that apply to protection of the general public.
The purpose of Federal guidance is to provide a common framework to
help ensure that the regulation of exposure to ionizing radiation is
carried out by Federal agencies in a consistent and adequately
protective manner. Although the individual Federal agencies have
determined, and will continue to determine, the details of specific
regulations, it is intended that they adhere to these proposed
recommendations as basic, minimum requirements. It should be
recognized, however, that in some situations application of these
recommendations may be superseded by specific statutory requirements.
These proposed recommendations have been developed by EPA in
cooperation with the Departments of Agriculture, Commerce, Defense,
Energy, Health and Human Services, Housing and Urban Development,
Interior, Justice, Labor, and Transportation; the National Aeronautics
and Space Administration; and the Nuclear Regulatory Commission. In
addition, the Conference of Radiation Control Program Directors of the
States contributed to the development of this proposal. This
cooperation was carried out through an extensive series of interagency
meetings carried out between 1986 and 1992, and agency reviews
conducted in 1993.
Previous Relevant Actions by the FRC and EPA
On May 13, 1960, President Eisenhower approved the first
recommendations of the former Federal Radiation Council (FRC) for
guidance to Federal agencies on the protection of workers and the
general public from radiation (25 FR 4402). This guidance was extended
by further recommendations approved by President Kennedy on September
26, 1961 (25 FR 9057).
Following a lengthy review by Federal agencies of those portions of
the 1960 and 1961 guidance that applied to occupational exposure the
Administrator of EPA made new recommendations for protection of workers
which were approved by President Reagan on January 27, 1987 (52 FR
2822). Those recommendations motivated a number of the changes now
proposed here for protection of the general public.
During the period since the current guidance was issued, EPA, alone
and in concert with other Federal agencies, has sponsored major reviews
of the health risks from exposure to low level ionizing radiation by
the Committee on the Biological Effects of Ionizing Radiation (BEIR),
National Academy of Sciences--National Research Council. These reviews,
which were published in 1972, 1980, 1988, and 1990, each incorporated
new scientific information that had become available since the
preceding review and contributed directly to the deliberations which
have resulted in these proposed recommendations.
Scope of the Proposed Guidance
These recommendations would apply to most exposure of the general
public to sources of ionizing radiation that are created or influenced
by human activities, the principal exceptions being exposure of
workers, of patients for medical purposes in the practice of the
healing arts, and of the general public from accidents. They would
apply, for example, to exposure of members of the general public due
to: (a) emissions of radioactive materials or radiation from
industrial, defense-related, and scientific operations; (b) use of
radiation and radionuclides in consumer products and medicine (except
for beneficial exposure of patients); (c) mining and processing of ores
that contain naturally-occurring radioactive materials; (d) disposal of
wastes generated by any of the above operations; and (e) transportation
of radioactive materials involved in any of the above operations.
Specific examples include, but are not limited to: nuclear
installations, including mines, mills, and processors of uranium and
thorium, nuclear fuel fabrication plants, nuclear reactors (nuclear
power plants, critical and subcritical facilities, and research
reactors), spent fuel storage and processing facilities, and weapons
production, testing, and storage facilities; x-ray generators and
radioactive sources; irradiation installations, such as particle
accelerators and large irradiators for teletherapy, radiosterilization,
and commercial product irradiation; inspection devices in airports;
consumer products such as static electricity elimination devices, ion
generating tubes, smoke detectors, and devices for producing light or
an ionized atmosphere, such as for dials and laboratory measurements;
and radioactive waste installations where radioactive wastes are
handled, treated and conditioned, temporarily stored, or permanently
disposed of.
These proposed recommendations also address most terrestrial
sources of exposure arising from human activities (these principally
involve naturally-occurring radioactive materials), but not exposure
due solely to background radiation or due to globally-dispersed effects
of past activities and accidents. Excluded, for example, is
consideration of variations in exposure which result from geographic
location, as well as the small annual dose increment from past weapons
tests and residual global contributions of past nuclear accidents, like
that at Chernobyl in 1986, because it is not practicable to contemplate
their control. For the purpose of these recommendations, ``background
radiation'' includes radiation of cosmic and solar origin at the
surface of the earth and radiation from naturally-occurring primordial
and cosmogonic radionuclides found in the earth's crust or produced in
the upper atmosphere by cosmic or solar radiation (including
radioactivity normally ingested in food and water) that is not enhanced
by human activities.
By technological means, however, exposure to naturally-occurring
radionuclides that might otherwise be considered sources of ``natural
background'' may be enhanced. Technologically-enhanced exposure to
natural radiation may be defined as exposure to natural sources of
radiation which is increased by (or would not occur without) a human
activity. Examples of such sources include radon and its progeny
accumulated in buildings; wastes from mineral ores, including ores
which are mined for uses or purposes other than for their radioactive
isotopes; wastes and/or emissions from the burning of coal, oil, and
natural gas; ion exchange resins and sludge from drinking water
treatment; scale in oil- and gas-field piping; articles made from
naturally-occurring radioactive materials, such as thorium in lantern
mantles and in certain optical glasses, and uranium in certain ceramic
glazes; and cosmic rays experienced during high altitude airplane
flights.
To the extent that exposure to such sources is controllable, they
are addressed by these recommendations. However, the guidance does not
recommend that all situations that could lead to increased exposure
should necessarily be regulated. For example, there is no readily
applicable means to reduce the small increase in radiation exposure
while in flight. In addition, it would require many circumnavigations
of the globe by airline on non-business matters to approach the
recommended limit for dose to individuals. Similarly, we believe it is
also not appropriate to regulate, for example, exploration of caves,
mountain climbing, or residence in high altitude locations because of
technologically-enhanced radiation. Decisions on what exposures are
appropriate candidates for reduction through regulation have been and
will continue to be based on legislative mandates and decisions by
regulatory agencies.
The largest single source of exposure of the general public is
radon. Radon, a naturally-occurring radioactive gas, can accumulate in
any structure that limits the free exchange of indoor and outdoor air.
There are two general categories of sources that can generate
significant amounts of radon within a building: radium-bearing soil or
rocks naturally situated beneath or near the building and radium-
bearing materials used in construction or as fill beneath or near the
building. Although exposure to radon from sources of the first kind may
be enhanced or reduced by building location, design, or construction,
these factors usually are not subject to direct Federal or State
control. Exposure to the second category of sources (radium-bearing
materials placed in or near a building) may be subject to direct
regulatory control or alleviation through Federal or State programs.
The numerical limits for individual dose proposed in this guidance
do not include the contribution from indoor radon produced by either of
the above categories of sources. EPA and the Centers for Disease
Control have provided separate advice to the public for protection
against exposure to indoor radon in A Citizen's Guide To Radon (EPA
document 402-K92-001, May 1992, and subsequent editions) and EPA has
published a series of other technical publications, pursuant to Pub. L.
100-551 (Oct. 28, 1988, 102 Stat. 2755, amending the Toxic Substances
Control Act, 15 U.S.C. Secs. 2601-2692). That advice is consistent with
this proposed guidance, where applicable.
Finally, these recommendations apply only to the management of
normal operations of facilities and devices that may expose members of
the public to radiation: that is, to controllable exposure to radiation
and releases of radionuclides that may expose the general public.
Normal operations include both those conditions that are expected to
occur with certainty as well as those that may be predicted to occur
with a reasonably large probability (e.g. anticipated operational
occurrences at nuclear reactors), but not conditions with a very low
probability of occurrence, such as the unintended re-entry of a
satellite containing radioactive materials. These recommendations also
do not apply to nuclear incidents, such as a major accident at a
nuclear facility or the result of terrorist activity, or to exposure
resulting from acts of war. Guidance for establishing radiological
emergency response plans and for making radiation protection decisions
during nuclear incidents has been provided by EPA in the Manual of
Protective Action Guides and Protective Actions for Nuclear Incidents
(EPA-520/1-75-001-A), pursuant to regulations issued by the Federal
Emergency Management Agency (47 FR 10758, March 11, 1982). Additional
guidance has been provided by the Food and Drug Administration on the
prophylactic use of potassium iodide during radiological emergencies
(47 FR 28158, June 29, 1982) and on the use of food and animal feed
contaminated by an incident (47 FR 47073, October 22, 1982, and,
jointly with the Department of Agriculture, 51 FR 23155, June 25,
1986).
Exposure to radiation as a medical patient, which may occur for
diagnostic or for therapeutic purposes, is not covered by these
recommendations. Recommendations of the Administrator of EPA and the
Assistant Secretary for Health of the former Department of Health,
Education, and Welfare concerning diagnostic use of radiation, approved
by President Carter in 1978, are provided in Radiation Protection
Guidance to Federal Agencies for Diagnostic X Rays (43 FR 4377).
Additional specific recommendations and guidance on patient selection,
evaluation of radiation exposure, quality assurance, and related topics
have been published by the Department of Health and Human Services.
However, decisions on the diagnostic or therapeutic use of radiation
are the responsibility of individual patients and their physicians, and
such decisions should be based on the benefits and risks of the use of
radiation for the conditions specific to each patient. Since those
decisions will involve considerations quite different from those
addressed here--exposure of the general public to a variety of sources
of general societal benefit--these recommendations do not apply to
exposure of patients.
These recommendations also do not apply to occupational exposure.
Federal agencies should normally regulate or manage the exposure of
workers in accordance with Radiation Protection Guidance to Federal
Agencies for Occupational Exposure (52 FR 2822), approved by President
Reagan in 1987.\1\ However, when workers can be exposed under
conditions that also apply to members of the public (e.g., when the
public has unlimited access to the work site), the source of such
exposure should be controlled in conformance with these proposed
recommendations for protection of the general public.
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\1\In some situations the distinction between members of the
public and workers will have to be carefully considered. A ;useful
test for determining whether individuals should be considered
workers or members of the public is whether or not their presence in
the exposure situation in question is within the scope of their
employment.
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The Need for Revision of the 1960 Guidance
Since the current guidance was issued in 1960, knowledge of the
effects of ionizing radiation on humans has increased substantially.
The BEIR Committee of the National Academy of Sciences--National
Research Council conducted major reviews of the scientific data on
health risks of low levels of ionizing radiation in 1972 and again in
1980.\2\ Portions of the information presented in the latter report
were expanded in a 1988 publication on risks from exposure to alpha
radiation.\3\ A comprehensive, major new review was completed in
1990.\4\ Similar reviews have been published by the United Nations
Scientific Committee on the Effects of Atomic Radiation in 1977, 1982,
1986, and 1988.\5\ The most important results from these reviews,
carried out over a period of more than two decades, are that, although
estimates of the nature and general magnitude of the risks from
radiation have not undergone fundamental revision, estimates of the
principal risk, that of cancer, have increased roughly threefold and
have become more certain.
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\2\The Effects on Populations of Exposure to Low Levels of
Ionizing Radiation, National Academy of Sciences, Washington, D.C.,
1972; The Effects on Populations of Exposure to Low Levels of
Ionizing Radiation; 1980, National Academy Press, Washington, D.C.,
1980.
\3\The Health Risks of Radon and Other Internally Deposited
Alpha-Emitters, National Academy Press, Washington, D.C., 1988.
\4\Health Effects of Exposure to Low Levels of Ionizing
Radiation, National Academy Press, Washington, D.C., 1990.
\5\Sources and Effects of Ionizing Radiation, United Nations,
New York, 1977; Ionizing Radiation: Sources and Biological Effects,
United Nations, New York, 1982; Genetic and Somatic Effects of
Ionizing Radiation, United Nations, New York, 1986; Sources,
Effects, and Risks of Ionizing Radiation, United Nations, New York,
1988.
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While our knowledge of the effects of radiation has become more
definitive, the extent of our use of radiation has increased and our
policies for regulating it have evolved. Prior to 1960, major uses of
radiation were limited, and the primary concern of radiation protection
was to ensure that doses to those few individuals that were affected
did not exceed limits on dose from all sources combined. Since then,
the numbers and types of man-made radiation sources have greatly
increased, and, at the same time, public concern about environmental
contaminants of all kinds has become an important influence in their
management. Of particular significance is that the focus of the many
environmental policies and laws that have emerged during the past two
decades has been more on improving the levels of control of individual
sources of contamination than on establishing a single acceptable level
of risk to individuals from all sources combined. This shift of concern
has led to the development of new concepts for determining the
appropriate level of control of specific kinds of sources. For
radiation sources, it has meant that attention has been focused on
assessing the potential impact of each source, or class of similar
sources, on populations and on the capabilities and costs of controls
to reduce that impact. The result has been the promulgation of a series
of regulatory requirements that are based on the specific
characteristics of particular classes of sources of public exposure to
radiation. These requirements invariably have been more restrictive
than those required to meet the existing Federal guidance on dose to
individuals from all sources combined.
Concurrent with the improved understanding of the effects of
ionizing radiation and the evolution of its regulation, international
and national advisory groups have refined and revised their basic
recommendations on radiation protection. In 1977, the International
Commission on Radiological Protection (ICRP) published revised
recommendations\6\ that have since been adopted, in whole or
substantial part, in most developed countries. In 1990, the ICRP issued
revised general recommendations\7\ that, for control of exposure of the
general public, expanded on those issued in 1977, notably in the areas
of policy for control of individual sources and the methodology for
expressing doses and risks from radiation. National bodies have also
contributed to the evolution of radiation protection practice. In the
U.S., the most recent (1993) recommendations of the National Council on
Radiation Protection and Measurements (NCRP)\8\ are, in most cases,
consistent with those of the ICRP. The changes in the recommendations
of these organizations reflect the improved understanding of effects on
health of ionizing radiation, new methodologies for evaluating doses
and risks from ionizing radiation, developing public policy on
acceptable levels of risk, and refinements in the application of basic
radiation protection principles to the regulation of individual sources
of exposure of members of the public.
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\6\Recommendations of the International Commission on
Radiological Protection, ICRP Publication 26, Pergamon Press,
Oxford, 1977.
\7\1990 Recommendations of the International Commission on
Radiological Protection, ICRP Publication 60, Pergamon Press,
Oxford, 1991.
\8\Limitation of Exposure to Ionizing Radiation, NCRP Report No.
116, National Council on Radiation Protection and Measurements,
Bethesda, MD, 1993.
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All of the above developments--improved estimates of radiation
risk, experience in regulating the constantly expanding complex of
applications of ionizing radiation, and the evolution of improved basic
concepts and methodology for radiation protection--have contributed to
the need for this proposed revision of the 1960 guidance.
Effects of Radiation on Human Health
Effects on human health of concern from exposure to low levels of
ionizing radiation may be divided into three categories.\9\ The first
of these encompasses all forms of cancer (including leukemias). Cancers
associated with radiation are not distinguishable from those associated
with other causes. Although radiogenic cancers are observed in humans
over a range of higher doses,\10\ it is necessary to infer the risk of
cancer at the exposure levels normally encountered by members of the
public because there is insufficient information to draw direct
conclusions based on observations of cancer at these levels.
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\9\A fourth category of effects, designated ``non-stochastic,''
occurs at dose levels higher than those addressed by these
recommendations. They are of importance for managing the response to
nuclear accidents (see EPA-520/1-75-001-A, op. cit.).
\10\We use the general term ``dose'' to mean the dose
equivalent, effective dose equivalent, committed dose equivalent, or
committed effective dose equivalent, with the precise meaning to be
inferred from the text. When precision is important, we use the full
term. In 1990 the International Commission on Radiological
Protection adopted new terminology (and definitions) for these
quantities: equivalent dose in place of dose equivalent, and
effective dose in place of effective dose equivalent. Although these
terms are simpler and are acceptable for use, we use the older, more
explicit terms.
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The second category encompasses hereditary effects (mutations)
induced in the reproductive cells of exposed individuals and
transmitted to their descendants. The severity of hereditary effects
ranges from inconsequential to debilitating or fatal. Although such
effects are observed in studies of animals at high doses, excess
hereditary effects have not yet been confirmed in epidemiological
studies of the descendants of exposed human populations.
Both cancer and hereditary effects are postulated to be caused by
``stochastic'' (i.e. random) direct or indirect interactions of
ionizing radiation with the genetic materials in living cells. In view
of the extensive, albeit incomplete, scientific evidence supporting
this view, including much theoretical and experimental radiobiology, it
is commonly assumed that at low levels of exposure the probability of
incurring either cancer or most serious hereditary effects increases
linearly with dose, without a threshold. The severity of such effects
is not believed to be related to the amount of dose received. That is,
it is the probability of occurrence of a cancer or an hereditary
effect, not its severity once it has been induced, that is assumed to
be dependent upon the size of the dose.
The risks to health from exposure to low levels of ionizing
radiation have been reviewed by the National Academy of Sciences, as
noted earlier, in a series of reports published between 1972 and 1990.
Regarding cancer, there continues to be divided opinion on how to
interpolate between the absence of radiogenic cancers at zero dose and
the observed effects of radiation (mostly at higher doses than those
normally encountered) to estimate the most probable effects of the
doses actually encountered by members of the public.\11\ A
preponderance of scientists believe that the available data best
support the use of a linear model for estimating the effect of such
doses. Some scientists, however, believe that other models provide
better estimates. These differences of opinion have not been totally
resolved by studies of the effects of radiation in humans, the most
important of which are those of the Hiroshima and Nagasaki atom bomb
survivors. Over the last decade an extensive reevaluation of the doses
and effects in these survivors has been carried out. With respect to
cancer, this reevaluation has strengthened the evidence for use of the
linear model at doses near background levels.
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\11\The risk of interest is not that at or near zero dose, but
that due to small increments of dose above the pre-existing
background level. Background in the U.S. is typically about 3 mSv
(300 mrem) effective dose equivalent in a year, or 0.2 Sv (20 rem)
in a lifetime. Approximately two thirds of this dose is due to
radon, and the balance comes from cosmic, terrestrial, and internal
sources of exposure.
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These studies have also resulted in increased estimates (roughly
threefold between 1972 and 1990) of the most probable risk of cancer
from environmental levels of radiation. Nonetheless, the estimated
number of health effects induced by incremental doses of radiation
comparable to natural background levels remains small enough, relative
to the number that already occur from other causes, that in all
likelihood it will never be possible to detect them in human
epidemiological studies. This lack of detectability does not mean,
however, that such effects on health do not occur. In the absence of
reliable evidence to the contrary, the Agency believes that it is
appropriate, for radiation protection purposes, to assume that at and
just above the level of natural background the risk of cancer and most
serious hereditary effects increases linearly with increasing dose,
without a threshold. That is, we assume that any increase in exposure
to ionizing radiation carries the potential for causing harm to health.
This assumption has been employed in the development of this guidance,
and is consistent with current as well as historical practice for
radiation protection world-wide.
The third category of health effects involves those exposed in
utero. It has long been believed that the unborn are more sensitive
than are adults to the induction of cancer by radiation. The unborn are
also subject to various radiation-induced physical malformations.\12\
Recent studies, however, have drawn renewed attention to the apparently
greater risk of severe mental retardation from exposure of the unborn.
These studies indicate that the sensitivity of the fetus is greatest
during the period from 8 weeks to 15 weeks after conception, and
continues at a lower level during the period 16 to 25 weeks.\4\ The
risk of less severe mental retardation--manifested as a lowered
Intelligence Quotient--is similarly elevated during these periods.
Although it is not clear to what extent the occurrence and degree of
retardation are proportional to the dose (or whether there is a
threshold dose for these effects), it is prudent to assume, for
regulatory purposes, that there is a linear, non-threshold relationship
between these effects and the dose delivered to the fetus during these
periods.
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\12\These include small head circumference (microcephaly), brain
size (microencephaly), eye malformations, and intrauterine growth
retardation.
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For radiation protection purposes EPA assumes, using a linear, non-
threshold model, an estimated risk to an average member of the U.S.
population of 5 x 10-2 fatal cancers per sievert\13\
(5 x 10-4 fatal cancers per rem) delivered at low dose rates.\14\
(That is, we estimate that if 100,000 people chosen at random from the
U.S. population were each given a uniform dose of 1 mSv (0.1 rem) to
the entire body at a low rate of exposure, five cases of fatal cancer,
on average, would occur during their remaining lifetimes, in addition
to the roughly 20,000 cases that normally would occur from other
causes.) The risk of inducing severe hereditary effects in their
offspring is estimated to be smaller than that for cancer, namely, on
the order of 10-2 per sievert (10-4 effects per rem).\15\ The
risk of severe mental retardation from doses to a fetus is estimated to
be greater per unit dose than the risk of cancer in the general
population--5 x 10-1 per sievert (5 x 10-3 per rem)\16\--but
the period of susceptibility is very much shorter.
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\13\The traditional special unit for dose equivalent has been
the rem. The special unit sievert (Sv) in the International System
of Units, adopted in 1979 by the General Conference on Weights and
Measures, is now in general use throughout the world. The RPGs
recommended here may be expressed in either of these units. One
sievert is equal to 100 rem. The prefix ``milli'' (m) means one
thousandth.
\14\``Low dose rates'' here means dose rates on the order of or
less than those from background radiation (see footnote 11). This
value for the risk from such doses incorporates a dose rate
effectiveness factor of two.
\15\The risk of severe hereditary effects in the first two
generations, for exposure of the reproductive part of the
population, is estimated to be 5 x 10-3 per Sv (5 x 10-5
per rem). For all generations the risk is estimated to be
1.2 x 10-2 per Sv (1.2 x 10-4 per rem). For exposure of
the entire population, which includes individuals past the age of
normal child-bearing, each estimate is reduced to 40% of the cited
value.
\16\The risk for mental retardation during the 8th through 15th
week [estimated to be 4 x 10-1 per Sv (4 x 10-3 per rem)]
plus the risk during the 16th through 25th week [estimated to be
10-1 per Sv (10-3 per rem)].
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The National Academy of Sciences has judged the 90% confidence
limits for their most recent estimates of the risk of cancer to be
about a factor of three greater and a factor of two less than their
estimate of the most probable value. They also observe that, at the low
doses and dose rates of concern in this guidance, the possibility that
there may be no risk cannot be ruled out, since epidemiological data
cannot rigorously exclude the existence of a threshold. The numerical
values of risks of genetic abnormalities and mental retardation are
somewhat less well established. In spite of uncertainties in the data
and its analysis, however, estimates of the risks from exposure to low
levels of ionizing radiation are better characterized than those for
virtually any other environmental carcinogen.
Basic Principles
In recommending the 1960 Federal guidance, the Federal Radiation
Council said: ``Fundamentally, setting basic radiation protection
standards involves passing judgment on the extent of the possible
health hazard society is willing to accept in order to realize the
known benefits of radiation'' (25 FR 4402). The need to make this
judgment led to three basic principles that have governed radiation
protection for many decades in the United States and in most other
countries. Although the precise formulation of these principles has
evolved over the years, their intent has remained essentially
unchanged.
The first principle is that any activity involving the exposure of
people to ionizing radiation should be sufficiently beneficial to
society to warrant the exposure; i.e., a finding should be made that an
activity causing exposure is ``justified.''
The second is that, for justified activities, exposure of people
should be ``as low as reasonably achievable.'' This principle commonly
has been designated by the acronym ``ALARA'' in the United States, and
is called ``optimization'' of radiation protection in international
practice.
The third is that, even for justified and optimized exposures, the
maximum dose to any individual should be limited so as not to exceed an
acceptable level of risk. This is referred to as ``limitation.''
The objective of the first two principles is to minimize
(consistent with benefits and costs) the estimated total harm (i.e.
health detriment) in the entire population from each source of
exposure; they do not, however, limit the way that harm is distributed
among individuals. They are, in this sense, ``source-related''
radiation protection requirements. The purpose of the third principle,
that of limitation of the maximum allowed dose, is to provide an upper
bound on risk to individuals. This principle, which is an ``individual-
related'' requirement, may be carried out in two ways: first, through
limitation of the potential dose from all sources of exposure combined,
and second, through additional more specific limitations on the doses
from individual sources.
The following seven proposed recommendations directly express,
expand upon, and implement these three basic principles in light of
current improved knowledge of the risks of radiation and of the variety
and extent of uses of radiation. In particular, they reflect lower
upper limits on dose to individuals from all sources combined, they
make explicit the need for further limitation of doses from individual
(or classes of) sources of exposure that is more restrictive than that
for all sources combined, and they introduce improved methods for
assuring that all of the various components of risk associated with
radiation exposure are accounted for in radiation protection
requirements for limiting exposure of the public.
Recommendation 1
There should be no exposure of the general public to ionizing
radiation unless it is justified by the expectation of an overall
benefit from the activity causing the exposure. Justified activities
may be allowed, provided exposure of the general public is limited
in accordance with these recommendations.
The principle that activities causing exposure of the general
public should produce a net societal benefit has long formed a
cornerstone of radiation protection policy, even though the judgment of
net benefit is not easily made. The 1960 Federal guidance states:
``There should not be any man-made radiation exposure without the
expectation of benefit resulting from such exposure* * *,'' and ``It is
basic that exposure to radiation should result from a real
determination of its necessity.''
Other advisory bodies have used language which has essentially the
same meaning. In its 1990 revision of international guidance, the ICRP
said ``* * *no practice* * *should be adopted unless it produces
sufficient benefit to the exposed individuals or society to offset the
radiation detriment it causes.'' When it addressed this issue in 1975,
the NCRP said, ``* * *all exposures should be kept to a practicable
minimum; * * *this principle involves value judgments based upon
perception of compensatory benefits commensurate with risks, preferably
in the form of realistic numerical estimates of both benefits and risks
from activities involving radiation and alternative means to the same
benefits.''\17\
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\17\Review of the Current State of Radiation Protection
Philosophy, NCRP Report No. 43, National Council on Radiation
Protection and Measurements, Bethesda, MD, 1975.
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These recommendations would continue the requirement for
justification in terms of an overall benefit. An obvious problem in
making this judgment is the difficulty of assessing, in comparable
terms, costs (including risks) and benefits. Given this situation,
informed value judgments may be necessary, and, in fact, are usually
all that is possible.
The determination that a particular activity involving exposure of
the general public is justified is often a complex process. Commonly,
it is not made by those directly responsible for radiation protection
decisions. For a few activities, like the x-ray examination of feet for
shoe-fitting practiced many years ago, agreement that there is not a
net benefit was easy to achieve. The decision was simplified in that
example because the risks and benefits accrued to the same individuals.
This is usually not the case. In extreme cases the determination can be
far more complex. For a major industrial application of radiation, for
example, the determination may involve not only the benefits and the
costs (direct, health, and environmental) of construction, operation,
waste disposal, accidents, and eventual decommissioning, but also the
tradeoffs between the activity and the economic, societal,
environmental, and resource implications of alternative means to
achieve the same result.
In any case, for a major activity the analysis should make a
reasonable demonstration that the benefit associated with the proposed
activity clearly outweighs the risks associated with the use of
ionizing radiation, including those associated with normal operations,
reasonably possible incorrect operation or management, and disposal of
wastes over the life cycle of the activity. When the consequences can
be significant, the analysis should include low probability events and
exposure pathways.
The process of balancing these factors may eventually involve
congressional, executive, and judicial inputs. One vehicle for
assisting such decision-making is the National Environmental Policy Act
of 1969 which, in effect, requires Federal agencies to assess and
consider the above factors for any major Federal action that could
significantly affect the quality of the human environment. Others
include the regulatory analysis process pursued by Federal agencies
(Executive Order 12866; 58 FR 51735, October 4, 1993), and decision
processes of public and professional bodies, such as public utility
commissions and professional medical groups. However, in making these
recommendations EPA does not propose to specify how or by whom
justification should be determined, but simply that the detrimental
effects of radiation, as well as other detrimental effects, should be
considered along with the benefits in any situation where an initial
decision is being made that involves significant exposure of the
general public to radiation.
Recommendation 2
A sustained effort should be made to ensure that doses to
individuals and to populations are maintained as low as reasonably
achievable.
The idea that exposure to radiation should be kept to a practical
minimum became a basic requirement in radiation protection early in the
century, shortly after the recognition that harm from radiation is not
limited to the skin damage that occurs at relatively high doses. The
concept was first applied to exposure of individual workers, primarily
in medical and research applications, since early uses of radiation did
not involve large populations. Later, after the commencement of nuclear
weapons testing and introduction of the widespread use of nuclear
power, it was applied to the exposure of populations--first to
safeguard the genetic pool and, later, after the assumption that cancer
induction is a stochastic process became accepted as a prudent premise,
also to reduce the presumed incidence of cancer. The requirement is now
taken to be the logical and necessary consequence of the assumption of
a linear relationship between exposure to radiation and the risks of
cancer and hereditary effects at the dose levels addressed by these
recommendations.
The phrase ``as low as reasonably achievable'' (ALARA) is used to
designate a general principle that exposure to radiation should be
controlled so as to achieve the lowest level reasonably attainable. The
1960 FRC guidance applied the concept to keeping dose to the individual
as low as practicable, and expressed it as a responsibility to be
carried out by the user of radiation. In these proposed recommendations
the ALARA principle is broadened to apply to collective doses in
populations as well, and in this broader application serves as a
principal basis for the implementation of ALARA through regulatory
practice. This use of the ALARA principle is customarily designated
``optimization'' of radiation protection. Optimization may be carried
out through regulatory determinations for whole classes of similar
sources, as in the establishment of standards for environmental
releases from nuclear power facilities, or, more directly, in the
determination of operating requirements for a specific facility.
Depending on the nature of the source, optimization may involve use of
simple or complex decision tools for balancing public health and
economic concerns to determine the optimal level of control. The basic
elements required for optimization are the values placed on avoiding
the estimated health detriments and the direct costs of control, as a
function of various levels of protection. In reaching a final
optimization determination, however, a variety of other economic and
societal factors may also have to be considered, such as the
distribution of health detriment over populations and over time, and
the technical feasibility and overall economic impact of controls. In
rare cases, the optimization process could result in the need to make
tradeoffs between larger doses to a few individuals (within the limits
specified in Recommendations 3 and 4) and many small doses in large
populations.
At the dose levels involved in the comparison of alternatives for
determining ALARA levels, linearity is assumed, and effects on public
health may be estimated from the collective dose in populations. In
cases where it is necessary to estimate the total public health
detriment from long-lived radionuclides, collective dose will often
have to be projected into the future, or in distant populations.
Regulatory decisions on ALARA levels should take into account such
projections when their contribution is both a significant part of the
total collective dose from the activity under examination and its
uncertainty is not large compared to the differences in collective dose
among the alternatives being examined. In some cases, it may be
appropriate to estimate effects on public health as a function of time
or distance, and to take their distribution in time or distance into
account in decisionmaking. However, it will never be appropriate to
apply an arbitrary cutoff to such projections based solely on the level
of dose to individuals, or on the distance from the source or in time;
such cutoffs would have the effect of preempting the decision-making
process before the magnitude and distribution of the avoidable impact
on health has been estimated.
In some situations, a decision to refrain from applying controls
may be the appropriate outcome of an ALARA determination. Such a
finding for an individual practice, or for a group of practices meeting
specified requirements, may be used as one criterion for exemption from
regulatory control. However, in addition to a finding that the total
health detriment in populations is not large enough to justify control,
it is also necessary to ensure that individual exposures are
sufficiently small, in view of the stipulations of Recommendation 4,
not to warrant regulation. Exemptions that satisfy each of these
criteria would be consistent with these proposed recommendations.
Although the ALARA principle is relevant to a wide variety of
radiation protection activities, these tend to fall into two general
categories. The first is that emphasized above, the establishment of
regulatory levels of control over individual sources or categories of
sources by Federal (or State) agencies. The second, and equally
important, is making management decisions in day-to-day operations at
facilities where ionizing radiation or radioactive materials are
present. The selection of regulatory limits for facilities, as well as
the day-to-day management of sources, in a manner consistent with the
ALARA principle are discussed further in connection with Recommendation
4.
Recommendation 3
The preceding recommendations address the need for justification
and optimization of activities that involve exposure of the general
public. The third basic radiation principle, limitation of maximum dose
to individuals, is addressed by the next two recommendations.
Recommendation 3 limits the sum of doses to any individual from all
radiation sources combined, through the Radiation Protection Guide
(RPG) for the general public; and Recommendation 4 addresses limitation
of doses from individual sources, through the establishment of source-
specific authorized limits.
The RPGs established in 1960 and 1961 consist of separate limits on
dose to the whole body and bone marrow (0.5 rem in a year, each), the
thyroid and bone\18\ (1.5 rem in a year, each), and the gonads (5 rem
over 30 years, average in the U.S. population). Those recommendations
(except that for the gonads) were based on the concept of limiting the
dose to the most critically exposed organ of the body.\19\ That is, it
was assumed that if dose to the critical organ was limited to an
acceptable level, then doses to other parts of the body would also be
acceptably low. One consequence of this approach is that exposure of
the body to external sources of radiation and exposure to internal
radioactivity are addressed by separate limits, and therefore the risks
from such exposures can be additive. Further, when several different
organs are exposed to internal radiation simultaneously, only the part
of the body receiving the highest dose relative to its RPG is decisive
for limiting the dose. That is, the risks associated with exposure of
other parts of the body are not considered in applying a dose limit
based on the critical organ approach. The 1960 limit for dose to the
gonads was based on an entirely different consideration, that of
limiting the incremental rate of mutation in the entire genetic pool of
the U.S. population. The incremental level of mutation deemed
unacceptable was on the order of a few per cent.
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\18\The guidance also included an approximately equivalent RPG
for bone in terms of radium-226 in the adult skeleton (0.003
micrograms).
\19\This was an incomplete set for this scheme of protection,
since many relevant parts of the body were not assigned RPGs. The
1960 RPGs for workers, by contrast, did comprise a complete set,
and, for the general public, the missing values for other parts of
the body were generally taken as \1/10\ of the corresponding
occupational values.
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These recommendations would replace the system described above with
the risk-weighted dose limitation system introduced by the ICRP in
1977\6\. The ICRP system takes into account the individual contribution
of each exposed part of the body to total risk. It does so by assigning
to each organ or tissue of the body a weighting factor that is
proportional to the risk per unit dose of inducing cancer or, for the
reproductive organs, to the risk per unit dose of inducing hereditary
effects in offspring. The risk limit is then expressed in terms of the
sum of weighted dose equivalents to all parts of the body, a quantity
called the ``effective dose equivalent'' (EDE).\20\ A limit in terms of
the EDE therefore reflects both the distribution of doses among the
various organs and tissues and their assumed relative sensitivities to
cancer and hereditary effects. Further, the EDE does not differentiate
exposures from external and internal sources; it includes both.
---------------------------------------------------------------------------
\20\The weighting factors are normalized so that the risk
associated with a given EDE is equal to that from a uniform dose of
the same magnitude to the whole body.
---------------------------------------------------------------------------
The effective dose equivalent is defined formally in footnote (b)
to Recommendation 3 and proposed weighting factors are listed in Notes
5 and 6, in the formal statement of proposed recommendations at the end
of this notice. These factors reflect the organ-specific risks of
lethal cancer, and, for the reproductive organs, the risk of serious
hereditary effects in the first two generations of offspring. They are
the same weighting factors as those adopted in Federal guidance on
radiation protection for workers in 1987. Although our current best
estimates for these effects on health would lead to somewhat different
values, the differences are sufficiently small that new weighting
factors are not proposed as part of these recommendations. The Agency
has made this choice for several reasons. First, it should be noted
that changes in the weighting factors, based on new estimates for
mortality, would have no effect on the level of risk represented by a
given dose to the whole body, since the sum of the weighting factors
is, by definition, normalized to unity. (If these factors were adjusted
to take into account non-lethal cancers or other factors such as age at
incidence the risk level could change, but, for the same reason, this
change would be small.) Thus, the general level of risk achieved would
not be affected. Second, the ICRP has recently published revised
weighting factors that, in addition to incorporating updated
information on risks of mortality, also consider other factors such as
morbidity, i.e., the risk of non-lethal cancer (but do this without
changing the recommended dose limit).\7\ We are reviewing those
weighting factors, as well as our own estimates of organ-specific risk
factors. Finally, extensive new tabulations, for each of over 700
radionuclides, of dose factors for various chemical forms and routes of
exposure have recently been completed using the existing weighting
factors.\21\ Regulations using these dose factors are being implemented
by EPA, NRC, and DOE. Changing the weighting factors for many of these
regulations will require formal rulemaking. EPA will keep these
considerations under review, will continue to review the choice of
weighting factors as new information becomes available, and will issue
guidance on improved weighting factors from time to time, following
review by and consultation with affected Federal agencies.
---------------------------------------------------------------------------
\21\These are specified in Note 7 to the Recommendations.
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Recommendation 3, which specifies the proposed new RPG for the
general public, consists of three parts. We first set forth the text of
the recommendation and some explanatory details, and then discuss the
basis for the choice of the value of the RPG and other related matters.
The first part of Recommendation 3 reads:
The combined radiation doses incurred in any single year from
all sources of exposure covered by these recommendations should not
normally exceed a Radiation Protection Guide of 1 mSv (100 mrem)
effective dose equivalent to an individual. The Radiation Protection
Guide applies to the sum of the effective dose equivalent resulting
from exposure to external sources of radiation during a year and the
committed effective dose equivalent incurred from the intake of
radionuclides during that year.
This recommendation would replace the 1960 and 1961 RPGs for dose
equivalent to the whole body and specified parts of the body by a
single RPG of 1 mSv (100 mrem) effective dose equivalent in a year. In
so doing, it would create a single limit for combined dose from
external and internal radiation.
Certain radionuclides, if inhaled or ingested, may remain in and
continue to irradiate the body for many years. This proposed
recommendation incorporates the use of ``committed'' dose into guidance
for the general public (this concept was introduced into Federal
radiation protection guidance for workers in 1987). It provides that
Federal agencies should base control of annual intake of such
radionuclides upon the future dose that may result over time (that is,
the committed dose), not just the ``annual'' dose accrued during the
first year following intake. This would assure that, in regulating
annual intake of such materials by members of the public, account is
taken of the additional risks committed from doses that will be
delivered in future years. The standard period for which committed dose
is calculated is proposed to be taken as 50 years, as in the Agency's
previous recommendations for workers. Although there are a few
radionuclides from which doses can accrue for longer periods, the risk
associated with intake of such radionuclides will be conservatively
estimated, compared to the risk from a comparable external dose,
because of the combined effect of the distribution over time of
committed dose and the latency period for expression of cancer.
The proposed RPG is expressed in terms of both the new special SI
unit ``sievert'' and the historically-used special unit ``rem.'' It is
not the intent of these recommendations to express a preference for
either system of units, but merely to recognize the existence and
acceptability of both. Federal agencies would be free to use either
unit under these recommendations, but should specify conversion factors
between the two systems in new regulations.
The second part of Recommendation 3 reads:
The Radiation Protection Guide may not be reasonably achievable
in some unusual situations. It may be exceeded temporarily in
situations that are not anticipated to recur chronically and when
Recommendations 1 and 2 are satisfied, provided that the radiation
dose incurred in any year does not exceed 5 mSv (500 mrem) effective
dose equivalent.
It is not anticipated that this provision would be used frequently.
In the past, doses to members of the public at or near such levels have
been uncommon, and the Agency expects this to continue to be true. We
have identified two examples of situations in which such doses are
known to occur now, and might reasonably be permitted to exceed the
RPG. The first is through the incidental exposure of a family member,
household member, or friend to a patient being treated (or diagnosed)
using radioactive materials, for certain medical procedures (primarily
in the treatment of thyroid cancer using\131\I). The second involves
the exposure, in some unusual cases, of individuals living near
radioactive contamination that has not yet been cleaned up. This almost
invariably involves naturally-occurring materials, often from mining or
milling operations. In situations where temporary relocation is not an
acceptable alternative it may not be practical to complete such cleanup
without exposing a few members of the public to doses exceeding 1 mSv
(100 mrem) in a year. This provision is not intended for use as a limit
in dealing with short-term emergency situations arising from nuclear
accidents; these are governed by the Protective Action Guides for
nuclear incidents (EPA-520/1-75-001-A).
The third part of Recommendation 3 reads:
Continued exposure of an individual over substantial portions of
a lifetime at or near the level of the Radiation Protection Guide
should be avoided. This will normally be achieved through
conformance of individual sources to Recommendations 2 and 4.
In recommending an RPG of 1 mSv (100 mrem) in a single year, it has
been necessary to balance the practical regulatory need for an RPG
expressed in terms of annual dose against the public health objective
of adequately limiting lifetime risk. We anticipate that satisfying the
criteria specified in Recommendations 2 and 4 will almost invariably
achieve this objective. However, in the unlikely event that
circumstances were such that continued exposure at or near the RPG over
substantial portions of a lifetime could occur, this portion of
Recommendation 3 explicitly expresses the criterion that chronic
exposure at such levels should be avoided.
Basis for the Radiation Protection Guide
In the latter part of the twentieth century, society has become
increasingly unwilling to accept risks imposed by activities that
produce environmental pollutants. Many of the benefits of
industrialized society, however, are brought about by activities that
carry with them some unavoidable elements of risk. This is especially
the case for so-called ``non-threshold'' pollutants like radiation, for
which it is assumed that there are no risk-free levels. The risk to an
individual from exposure to ionizing radiation, as discussed above, is
assumed to depend linearly upon the radiation dose, without a
threshold. Under current guidance the average member of the public now
receives, from all the sources to which that guidance has consistently
been applied, only a very small dose--less than 0.01 mSv (1 mrem) in a
year.\22\ The average risk of fatal cancer incurred from such an
exposure is estimated to be somewhat less than 5 in ten million.
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\22\During the period 1960 to the present, the current RPG has
not consistently been applied to exposure due to natural sources.
The primary examples are building materials and radon in domestic
groundwater supplies; these contribute additional average effective
dose equivalents to the U.S. population of 0.035 mSv (3.5 mrem) and
0.01-0.06 mSv (1-6 mrem), per year, respectively. Tobacco smoke
contributes a further, at present incompletely characterized, dose.
(These estimates are derived from Ionizing Radiation Exposure of the
Population of the United States, National Council on Radiation
Protection and Measurements Report 93, Bethesda, MD (1993).)
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The cumulative risk to society associated with the variety of
current uses of radiation is now governed by the dual requirements that
each use be justified and that its effect on public exposure minimized
by optimizing radiation protection. These requirements would be
continued and strengthened under proposed Recommendations 1 and 2.
Typically, this would result in a distribution of annual doses from
each source of radiation exposure ranging from zero for most members of
the population to a maximum value (established under Recommendation 4)
accruing to a small number of individuals. The RPG serves as an upper
bound on the highest doses resulting from the sum of all such
distributions. As such, it acts as a limit on the annual increment of
risk, now and in the future, to the theoretically most exposed
individual with typical consumption and other relevant behavior habits.
In selecting the proposed value for the RPG the Agency has had to
consider a number of judgmental factors: the relation between a limit
on annual dose and the implied lifetime risk; the degree of protection
achieved through the application, by regulatory authorities, of
optimization to the derivation of source limits, as well as their
consideration of the various possibilities for multiple exposure to
current and future sources, under Recommendation 4; and, finally, the
record to date on the operational application of ALARA (i.e., the
difference between source limits and the doses actually experienced).
It is anticipated that the proposed RPG, applied in the context of
these proposed recommendations, would, under most circumstances, result
in lifetime risks to the most exposed members of the public from man-
made radiation in the environment of less than one in ten thousand.
This expectation is based on past experience under current radiation
protection guidance, cited above, coupled with the improvements in
protection proposed here--most particularly those proposed under
Recommendations 2, 3, and 4. Recommendation 2 strengthens the
requirement that doses be maintained as low as reasonably achievable;
Recommendation 3 reduces the RPG; and Recommendation 4 requires source-
specific limits that take into account the present and future potential
for doses from other sources (and are therefore normally only a
fraction of the RPG). EPA has, in a number of previous actions,
concluded that a lifetime risk level no greater than about one in ten
thousand provides an acceptable level of protection. These include the
National Emission Standards for Hazardous Air Pollutants (NESHAPs), the
National Primary Drinking Water Standards, and the Agency's guidelines
for site-specific risk management under the Comprehensive Environmental
Response, Compensation, and Liability Act (``Superfund''). These
recommendations propose that this level of protection is also
appropriate for application in this Federal Radiation Protection
Guidance for Exposure of the General Public and would be achieved
through the cumulative application of these recommendations.
In addition, the proposed five-fold reduction in the RPG and the
accompanying requirement that it be applied to the sum of external and
committed internal doses would assure that maximum risks permitted to
even the most highly exposed individuals are greatly reduced, compared
to those permitted under the current RPGs. Although not many people are
exposed near the RPG, a few cases of such high risks do now exist.
These are usually associated with technologically enhanced exposure to
natural radioactive materials. Examples include phosphate mining
residues in Idaho and Florida, radium processing wastes in New Jersey,
Illinois, and Colorado, and uranium mill tailings at publicly
accessible locations in a number of western states. Under the current
RPGs, annual doses due to external exposure up to 5 mSv (500 mrem) are
permitted, in addition to organ doses from internal exposure up to 15
mSv (1500 mrem), depending on the organ and the radionuclide. Such
doses imply lifetime risks up to 250 in one million for each year of
external exposure, and up to 40 in one million for each year of
internal exposure. The proposed RPG of 1 mSv effective dose equivalent
would limit the incremental lifetime risk associated with each year of
combined external and internal exposure to 50 in one million, a
significant reduction in risk.
Finally, the Agency notes that the proposed RPG is consistent with
levels found acceptable and in use by the international community. A
value of 1 mSv per year is recommended as the upper bound on doses to
members of the public by both the ICRP and the International Atomic
Energy Agency, and is in common use throughout the world.
To provide a perspective on the above levels of risk, it may be
noted that the average American is exposed annually to an effective
dose equivalent of about 3 mSv (300 mrem) from natural background
radiation, including an average contribution of about 2 mSv (200 mrem)
from radon in homes. This exposure is three times the proposed RPG, and
each year's exposure corresponds to an incremental lifetime risk of 150
in one million. Although the average level of exposure to natural
background provides perspective, it does not, however, provide a
justification for the RPG, since it represents an uncontrollable source
of risk, and the RPG applies to controllable sources.
The levels of risk assumed to be associated with radiation exposure
may also be compared to involuntary and voluntary risks actually
incurred in common activities. For example, the essentially involuntary
risk of dying of a household accident averaged about 110 in a million
per year, between 1980 and 1990, and the average probability of dying
of an automobile accident in the same decade, a voluntary risk, was 240
in a million per year. We emphasize that all of these examples are
provided for perspective only, and that the existence of other risks,
voluntary or involuntary, is not a justification for any particular
incremental radiation risk.
EPA recognizes that some of the assumptions that underlie the
proposed RPG are not readily quantified, or are based on experience
that may not accurately predict the future. We will continue to review
exposure of the general public, with a view to initiating
recommendations for any further modification of these recommendations
that may be warranted to ensure that low risks to individuals are
maintained.
Other Matters Related to the Radiation Protection Guide
In developing these recommendations, EPA also considered risk to
the unborn from exposure of pregnant women. It is clear that, in
general, the fetus is more sensitive to many environmental carcinogens,
mutagens, and teratogens than are adults, because the rate of cell
division in their developing organs is far greater. This appears to be
the case for radiation as well, which can act in any of these three
ways. Of these risks, the most important at the levels of exposure
addressed by these recommendations is mental retardation due to
exposure to radiation during the eighth to fifteenth weeks of
gestation, as discussed earlier.
In considering the importance of the risk of mental retardation to
the choice of the RPG, we note that the sensitive period for inducing
this effect represents a very small part (0.2%) of a normal lifetime,
the time span addressed by the risk limitation contemplated by these
recommendations. This sensitive period should be considered in
conjunction with the observation that sources governed by these
recommendations typically yield exposure that is uniformly distributed
in time, and almost never yield high-level, short-duration doses.
(Accidents are not addressed by this guidance.) Based on these two
observations, coupled with the numerical values for radiation risks
cited earlier, EPA concludes that the risk of mental retardation from
the relatively small exposure of the unborn that would accumulate
during the short period of sensitivity before birth will be smaller
than the risk of cancer associated with the very much longer period
following birth, during which time a relatively much larger exposure to
sources governed by these recommendations could accumulate. EPA
believes, further, that it is not appropriate to base a general limit
for members of the public on the highly unlikely circumstance that the
entire RPG is delivered during the short period of significantly
elevated susceptibility of the unborn. We conclude, therefore, that
these proposed recommendations would provide adequate protection of the
unborn without specifying a separate limit specifically for this
purpose.
An opposite situation is posed in considering the risk to members
of the population who are within one or two decades of the end of a
normal lifetime. In this case the risk, instead of being higher, is
lower. The risk of cancer in this population approaches being an order
of magnitude smaller than the risk to an average member of the
population, and the risk of genetic consequences is normally no longer
present. EPA has not proposed a higher RPG for this population because,
as noted for the case of the unborn, these recommendations are based on
limiting the risks that accrue over a lifetime, not on a yearly basis.
The RPG is expressed as an annual limit simply for ease of
implementation. We also note that a limit that was different for
different ages of members of the public would pose severe
implementation difficulties.
Implementation of measures for assessment and control of internal
exposure to radionuclides commonly makes use of intake-to-dose
conversion factors. EPA has previously tabulated such values for use in
implementing the Federal Guidance for Protection of Workers, in Federal
Guidance Report No. 11, Limiting Values of Radionuclide Intake and Air
Concentration, and Dose Conversion Factors for Inhalation, Submersion,
and Ingestion (EPA-520/1-88-020). The dose conversion factors in this
report and its subsequent editions also apply to intake of
radionuclides by members of the general public. For external sources,
exposure-to-dose conversion factors are tabulated in Federal Guidance
Report No. 12, External Exposure to Radionuclides in Air, Water, and
Soil (EPA 402-R-93-081).
These dose conversion factors are appropriate for application to
any population adequately characterized by the set of values for
physiological parameters developed by the ICRP and collectively known
as ``Reference Man.''\23\ The actual dose to a particular individual
from a given intake is dependent upon age and sex, as well as other
characteristics. As noted earlier, implementing limits for the general
public expressed as age and sex dependent quantities would be
difficult. (Clearly, it would be impracticable to conduct an annual
survey of age and sex at every location of a potential source of public
exposure.) More importantly, the variability in dose due to these
factors is comparable in magnitude to the uncertainty in our estimates
of the risks which provide the basis for our choice of the RPG. For
this reason EPA believes that, for the purpose of providing radiation
protection under the conditions addressed by these recommendations, the
assumptions exemplified by Reference Man adequately characterize the
general public, and a detailed consideration of age and sex is not
generally necessary. The most obvious exception is for large doses
delivered in a short period of time, as in an accident, for which case
the appropriate response is addressed by separate EPA recommendations
(EPA-520/1-75-001-A).
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\23\ICRP No. 23 Report of the Task Group on Reference Man, 1974.
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The proposed RPG is sufficiently small that the dose any organ
might receive will be far below threshold levels for non-stochastic
health effects (i.e. effects on health, such as burning of the skin,
cataracts, impairment of fertility, and more serious effects which can
lead to early death, all of which only occur when threshold levels of
dose that are greater than 0.5 Sv (50 rem) are exceeded). That is,
adequate protection of every organ from non-stochastic health effects
is automatically ensured by the proposed RPG. These recommendations
therefore do not include separate limits to prevent the occurrence of
non-stochastic effects.
The sum of weighted organ doses that comprises the effective dose
equivalent does not include an allowance for cancers induced by
irradiation of the skin. In some circumstances, however, in the
assessment of total health detriment in populations, dose to the skin
may be large enough to warrant consideration of fatal cancers due to
skin dose. These proposed recommendations provide for adding to the
effective dose equivalent a term that is the product of the dose
equivalent to skin (averaged over the entire skin surface) and a
weighting factor of wskin=0.01 in such cases.
Recommendation 4
Recommendation 4 consists of two parts. The first reads:
Authorized limits for sources should be established to ensure
that individual and collective doses in current and future
populations satisfy the objectives of this guidance. These limits
may be developed for categories of sources or for specific sources.
Authorized limits for sources should normally limit doses to a
fraction of the Radiation Protection Guide for all sources combined.
Authorized limits are standards, regulations, technical
specifications, or other requirements established by a responsible
authority to ensure that the objectives of this guidance with respect
to limitation of doses will be satisfied. Implementation of the ALARA
requirement (Recommendation 2) will involve consideration of collective
doses to populations,\24\ of control mechanisms, and of other factors
that will differ for each category of sources, and will usually lead to
control levels that result in doses to individuals less than the RPG
(Recommendation 3). However, there are many different categories of
activities using radiation that can lead to exposure of members of the
public. These currently include medical uses of radiation and their
supporting activities; nuclear electric power facilities and their
supporting fuel cycle facilities; research and industrial users;
weapons production, storage, and disposal facilities; technologically-
enhanced exposure to natural radiation sources; consumer products;
space applications; disposal sites for radioactive wastes; and
decommissioned sites at which radioactive materials were formerly used.
It is therefore also necessary to ensure that total doses to
individuals, who may be exposed not only to more than one source in a
given category in a few cases, but more often to a number of different
categories of sources at one time, are not likely to exceed the RPG. It
is not intended that this objective be implemented through
apportionment of the RPG among categories of sources; this would be
impracticable. Rather, this consideration, which must encompass the
potential for doses to the general public both now and in the future,
will necessarily be a broad judgment, based on general observations of
the characteristics of existing activities, projections for their use
in the future, and the potential for presently unidentified future
uses.
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\24\These recommendations are not intended to require numerical
limits for collective dose. Although the determination of ALARA
levels necessarily involves optimization of the collective dose, the
regulations that implement these levels can be expressed in terms of
individual or collective dose, total or concentration of activity
released, installation and use of specified controls, or any other
specification that the regulatory authority finds appropriate.
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To implement these objectives, authorities responsible for limiting
exposure of the public should govern sources through use of
``authorized limits'' established either for categories of similar
sources or for specific sources. In establishing these authorized
limits, since the ALARA process considers actual costs and capabilities
of controls, it is important that assessments of doses to individuals
and populations be carried out realistically and comprehensively. Such
assessments should contain neither unnecessarily unrealistic
assumptions that overestimate doses nor omit any significant
contributions to risk or detriment, since either of these would
invalidate the ALARA determination. Further, authorities should
consider, in addition to the design capabilities of facilities for
control of releases, expected departures from anticipated design
performance. Finally, in the case of authorized limits established for
broad categories of sources, the judgments will often necessarily be
broad and may lead to somewhat higher values, with further
implementation of the ALARA process left to management of the
individual sources within a category.
Authorized limits currently exist for a wide variety of sources, at
levels that are fractions of the proposed RPG. For example, in 1977 EPA
established general limits for dose received from all radionuclides,
combined, via all exposure pathways, combined, from most facilities
involved in the nuclear fuel cycle combined, including power reactors,
in 40 CFR Part 190. The principal limit, 25 millirem (0.25 mSv) per
year to the whole body, is 25% of the proposed RPG. Additional site
specific limitations are established, for example, by the Nuclear
Regulatory Commission in license conditions for individual commercial
reactor sites, or in requirements for specific types of facilities,
such as low level waste sites in 10 CFR Part 61. EPA has recently
established source-specific limits for doses from all radionuclides,
combined, via all air pathways from individual sources of radionuclide
emissions, including all Federal facilities, in 40 CFR Part 61. These
generally require limiting doses to 10 millirem (0.1 mSv) per year
effective dose equivalent, or 10% of the proposed RPG. Finally, the
national drinking water standards at 40 CFR Part 141 limit doses from
water at the tap to 4 millirem (0.04 mSv) per year whole body or organ
dose from all man-made radionuclides, or 4% or less of the proposed
RPG. In each of these cases, the regulatory process, under the current
recommendations, supplemented in some cases by additional statutory
requirements, has resulted in requirements ensuring that maximum dose
to individuals from a specific source or category of sources is a small
fraction of the proposed RPG for dose from all sources combined.
Although this situation is anticipated to continue, we believe it is
prudent to note explicitly that authorized limits should normally
satisfy this condition.
Once such authorized limits are established, it will no longer be
necessary to further evaluate contributions to doses from any other
source as part of the management of the operations of a specific
source. These requirements thus serve to avoid the need to perform
detailed, and in some cases very difficult to validate, evaluations of
the combined incremental doses from other sources at individual sites.
Conversely, if these requirements are exceeded (or are absent), then
such evaluations may be necessary to assure conformance to the RPG
(Recommendation 3).
The second part of Recommendation 4 reads:
Sources should be designed not to exceed authorized limits, and
should be operated so as to maintain doses to members of the general
public as low as reasonably achievable within such limits.
The ALARA principle applies not only to the establishment of
authorized limits, but also to detailed management of facilities where
sources of radiation are prepared, employed, stored, or transported.
This is necessary and appropriate because authorized limits must
usually provide flexibility for anticipated deviations from design
performance, and controls usually can perform better than their design
limits. Thus, exposure of the general public, even if a source conforms
to authorized limits, will not be ALARA when lower exposures are
reasonably achievable.
As exemplified by the performance of many facilities over the past
two decades, doses to the public usually can be maintained far below
authorized limits through responsible and skillful control of radiation
sources. This has required careful management and supervision of
radiation protection activities, including the choice and
implementation of radiation control measures for sources of exposure of
members of the public, training in procedures to control such exposure,
and monitoring, assessment, and reporting of exposure levels and doses
at appropriate on-site and off-site locations. The routine management
of a facility and decisions on how, or whether, particular actions
should be carried out can, in the aggregate, be as (or more)
significant for radiation protection of the public as the design of the
facility and choice of its authorized limit.
The selection of authorized limits and the application of the ALARA
principle to operations requires technically informed judgments. Thus,
the practice of ALARA must be the responsibility primarily of those
persons who control and manage sources of radiation under the oversight
of the responsible public authorities; that is, it should not be the
responsibility of individual members of the public, who are not
familiar with radiation protection practices. For example, consumer
products containing radioactive materials, and instructions for their
use and disposal, should be designed to maintain radiation doses that
are ALARA, and members of the public who use them should not have to
rely upon their own judgment on this issue. The ALARA principle must be
implemented by those who are directly responsible for radiation
protection, or who are otherwise professionally responsible for health,
safety, and environmental protection aspects of radiation sources.
Recommendation 5
Risks associated with exposure of the general public to
radiation that may occur due to Federal agency decisions, and the
policies upon which these decisions are based, should be made known
to the public in a timely fashion as part of the decision process.
The degree of detail and type of information made available should
be appropriate to the potential radiation exposures involved.
Information on risks should encompass estimates of the risks of
effects on health over time, and of the uncertainties in such
estimates. Information on policies should include reference to this
Federal radiation protection guidance for the general public and
other relevant Federal policies.
To judge the validity and acceptability of decisions about Federal
activities which not only bring benefits but also pose risks, the
public requires clear and, to the extent possible, quantitative
information. In the case of proposed Federal actions involving exposure
to radiation, this includes information on the biological effects of
radiation, on the levels of risk associated with exposures that may
result from the actions, and on the Federal policies that underlie the
action.
Requirements for the development and presentation of these kinds of
information may be found in the National Environmental Protection Act
(NEPA), 42 U.S.C. Secs. 4231 et seq.; Title III of the Superfund
Amendments and Reauthorization Act (SARA), 42 U.S.C. Secs. 9601 et
seq.; the Administrative Procedure Act, 5 U.S.C. Secs. 551 et seq.; and
in other legislation. Such information serves to assist the public in
becoming constructively involved in the decision process and in
influencing the public policy issues that affect them.
It is the purpose of this recommendation to ensure that, when
Federal agencies formulate policies and make decisions that influence
the exposure of the general public, information that will adequately
inform the public during the decision-making process is made available
by them in a timely manner. Although it is not intended to require
general dissemination of information concerning ongoing operations, nor
to require major public information distribution efforts, such
activities are encouraged whenever it is reasonable to carry them out.
Recommendation 6
Assessments and records appropriate to the origin and magnitude
of expected doses and the exposed population should be performed and
maintained to demonstrate conformance with requirements which
implement these recommendations. The types and accuracy of methods
and procedures used in these assessments should be reviewed
periodically to ensure that they are appropriate and are being
competently applied.
Control of exposure of the public is normally ensured through
analysis of releases from sources and modeling of environmental
transport to hypothetical ``critical groups'' of the general public
assumed to receive the greatest exposure. Unlike the situation for
workers exposed occupationally, it is usually neither appropriate nor
feasible to physically monitor doses to individual members of the
public. Such dose rates and concentrations may be determined by
measurement of radioactive effluents, mathematical modeling of the
dispersal of radionuclides in the environment, or both.
Assessments and records required to ensure conformance with these
recommendations will vary, depending upon the nature of the source of
exposure. Responsible authorities will have to determine what is needed
to ensure that exposures of members of the public actually are
maintained within authorized limits and are ALARA. In some cases,
comprehensive radiation assessment programs will be needed which
include trained personnel, facility and environmental measurements,
audit procedures, and maintenance of records. In many cases
conservative assumptions, such as the assessment of doses to a
hypothetically most exposed individual, may be used to simplify the
demonstration of compliance. In still others, simple operational
procedures will suffice.
This recommendation intentionally allows flexibility with respect
to what should be assessed and recorded, so that the responsible
authorities will be able to design optimal programs for each situation.
This is intended to avoid, in particular, burdensome requirements for
situations in which individual doses and detriments to populations are
very low. At the same time, assessments and recordkeeping must be
adequate to document that requirements which implement these
recommendations have been satisfied.
Recommendation 7
Exceptions to Recommendation 3 for planned exposure to radiation
should be made only for highly unusual circumstances, and only when
the Federal agency having jurisdiction has carefully considered the
reasons for making them in light of these recommendations. If
Federal agencies authorize any exception to these values, they
should make it a matter of public record.
This proposed guidance applies to emissions and exposure of the
general public under normal circumstances. In developing these
recommendations, EPA has considered situations that might normally
arise. It is not possible to foresee all contingencies, however, and
highly unusual situations may occur when exceptions to the limiting
values of Recommendation 3 are appropriate. This recommendation
provides that if such circumstances should arise, Federal agencies
should carefully consider the balance of the guidance, including the
information requirements of Recommendation 5, and make a public record
of any authorized exception to Recommendation 3 (e.g., by publishing a
notice in the Federal Register or in a local newspaper of general
circulation).
Implications of these Recommendations
It is expected that these proposed recommendations could be
implemented relatively easily, since most of them are already, in large
part, in effect. For example, most sources are already regulated in
such fashion that exposures of members of the public are a small
fraction of the proposed Radiation Protection Guide of 1 mSv (100 mrem)
in a year, and we are aware of no regulated sources that exceed the
proposed RPG. Perhaps the most significant implication of these
recommendations would be to promote consistency between Federal
agencies by clarifying the basic considerations to be taken into
account in the development of new standards and regulations, and in
their implementation. The recommendations modernize the methodology for
expressing dose, and clarify the relationship of the RPG to standards
and regulations for sources, as well as the various applications of the
principle that doses should be maintained ``as low as reasonably
achievable,'' and they provide, for the first time as a part of their
basis, numerical estimates of the various risks from low levels of
ionizing radiation.
Implementation of the proposed recommendations would require only
minimal changes in Federal regulations, and should be achievable over a
short period of time. Many of the changes called for are largely
already well under way, major examples being the revisions recently
made by the Department of Energy in their Order No. 5400.5, and those
recently promulgated by the Nuclear Regulatory Commission in 10 CFR
Part 20. It is expected that Federal agencies will have little
difficulty in identifying and correcting any remaining problem areas,
and in providing necessary flexibility and transition periods, to avoid
undue impacts that might inhibit prompt implementation of new guidance.
We note in passing that in some cases (notably in the regulation of
exposure of the public from the transportation of radioactive
materials) conformance to existing guidance is based upon the
assumption of ``reasonably foreseeable'' scenarios for the spatial and
temporal relationship between radioactive materials and members of the
public, and that because of this assurance the RPG will never be
exceeded cannot be given with absolute certainty. These recommendations
do not propose any changes in this regard, and EPA expects that in such
cases the same approach to protection would continue to be employed to
achieve conformance to these new recommendations.
The anticipated costs of implementing these recommendations are
primarily those that would be incurred by the various agencies in
modifying their own regulations. These are not expected to be
substantial, since most of the necessary methodological changes have
already been implemented in connection with the revised Federal
guidance for occupational exposure issued in 1987. Unlike the situation
for occupational exposure, where the need to reduce the doses received
by a few highly exposed workers to conform to lower limits may lead, in
some cases, to the hiring and training of additional workers, there are
few direct implementation costs involved here, since most sources are
already regulated to well within the proposed new requirements.
This guidance would not supersede any statutory responsibilities of
the agencies that would implement these recommendations, and in some
situations application of these recommendations could be superseded by
specific statutory requirements. In addition, it does not create any
new authority. As noted earlier, it is the purpose of this Federal
guidance to provide a common framework to help ensure that the
management of exposure to radiation in the United States is consistent
and adequately protective. This can be carried out through regulations
applicable to the public sector, through orders applicable to the
internal operations of Federal agencies, through guidance, or by any
other practicable means. The individual Federal agencies, based on
their statutory and administrative mandates, have determined, and would
continue to determine, the details of specific regulations, orders,
guidance, or other actions, the parties responsible for implementing
them, and the means to do this.
The proposed recommendations differ from current guidance in
significant ways. The Radiation Protection Guide for maximum radiation
dose to a member of the public in a year is reduced by a factor of
five, from 500 mrem to 1 mSv (100 mrem). The concept of risk-based
weighting of doses to different parts of the body is adopted, and the
committed dose is introduced as the primary basis for control of
internal exposure. The RPG now applies to the sum of external and
internal exposure. Increased emphasis is placed on keeping justified
exposure as low as reasonably achievable (ALARA), and on the
comprehensive consideration of doses in populations near and distant,
now and in the future. The establishment of authorized limits for
sources or categories of sources that are derived giving consideration
to the wide variety of potential sources and their future implications
for exposure that, combined, must be maintained within the RPG, and
from the comprehensive application of ALARA, is recommended. The
proposed recommendations recognize, for the first time in this Federal
guidance, the importance of public information and of assessing and
recording public exposures. Finally, these recommendations would bring
U.S. radiation protection policy into conformance with that in general
international use. EPA expects these changes would strengthen the
overall system for radiation protection of the members of the public in
the United States.
These recommendations would replace those portions of current
Federal Radiation Protection Guidance (25 FR 4402) that apply to
protection of the general public from ionizing radiation. It is
expected that individual Federal agencies, on the basis of their
knowledge of specific sources of exposure of the general public, would
use this new guidance as the basis upon which to revise or develop
detailed standards or regulations, to the extent that they have
regulatory or administrative jurisdiction. Pursuant to my
responsibilities under Executive Order 10831, the Atomic Energy Act of
1954, as amended, and Reorganization Plan No. 3 of 1970, I would
propose to keep informed of Federal agency actions to implement this
guidance and to interpret and clarify these recommendations, and, in
consultation with affected Federal agencies, from time to time amend
the clarifying notes to reflect new technical information, as necessary
to promote a consistent and effective Federal program of protection of
the public from radiation.
Request for Comments
EPA requests comments on any and all aspects of these proposed
recommendations. We would, for example, appreciate comment on the
overall approach to protection of the public embodied by these
proposals, which would continue and expand upon the approach
recommended for protection against the effects of exposure to radiation
by national and international professional advisory bodies, and which
has formed the basis for previous guidance to Federal agencies. In
addition to general comments, we are also particularly interested in
commenter's views on the following specific matters:
1. Should EPA consider a lower or higher value for the Radiation
Protection Guide (RPG); e.g., 0.3, 0.5, or 1.5 mSv (30, 50, or 150
mrem)? What would be the rationale for such a value? If a lower value
is adopted would it be necessary to modify Recommendation 4, and, if
so, how could it be modified to retain flexibility to provide for
possible future beneficial uses?
2. Is it necessary to provide, in Recommendation 3, for temporary
exposures as high as 5 mSv (500 mrem). What specific examples of
situations that justify this proposed provision currently exist, or
have a high probability of occurring in the future?
3. Should the guidance recommend a single maximum risk (or dose)
level for individual sources, under Recommendation 4, which would serve
as an upper bound on all ALARA determinations? If this approach were
adopted, would the RPG in Recommendation 3 become superfluous?
4. Should the recommendations provide guidance on the kinds of
situations under which it would be appropriate for a Federal agency to
invoke Recommendation 7. Are there foreseeable situations that require
the existence of this proposed provision?
5. Should EPA initiate proposals to update the weighting factors
for effective dose now. If so, what basis or values for these factors
should we consider?
6. Has EPA correctly characterized the cost of implementing these
recommendations. If not, what specific costs have we not identified,
what is their estimated magnitude, and what is the basis for this
estimate?
7. These proposals do not express a preference between historical
radiation units, commonly used in health physics practice, and the new
system of units (SI) now in scientific and international health physics
use. Should they?
8. These proposed recommendations do not address protection of
animals and plants. Are the proposed levels adequate to protect all
plant and animal species? If not, what level would provide adequate
protection? Is protection at the level of species the appropriate
choice?
EPA will carefully consider all written responses to this request
for comments, and we encourage interested parties to present their
views at the public hearing that will be held on these proposals.
Following these hearings we will, after consulting with affected
Federal agencies, formulate and transmit final recommendations to the
President for revisions to Federal radiation protection guidance for
exposure of the general public.
Dated: December 14, 1994.
Carol M. Browner,
Administrator.
Proposed Recommendations
The following recommendations are made for the guidance of Federal
agencies in the formulation of regulations and conduct of programs for
the protection of the general public from ionizing radiation. Their
objective is to ensure that exposure to ionizing radiation is
restricted to levels that will not produce undue risk to individuals or
undue harm in populations.a The recommendations apply to radiation
exposure other than that from background radiation or received as a
patient in the practice of the healing arts, as a worker, or as the
result of an accident. (See Notes 1 and 2.)
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\a\The term ``risk,'' as used here, means the statistical
probability of harm to the health of an individual from exposure to
radiation. ``Harm in populations'' from exposure to radiation,
called the radiation ``detriment'', means the mathematical
expectation of harm in the population, taking into account the
probabilities and the severities of different deleterious effects.
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1. There should be no exposure of the general public to ionizing
radiation unless it is justified by the expectation of an overall
benefit from the activity causing the exposure. Justified activities
may be allowed, provided exposure of the general public is limited in
accordance with these recommendations.
2. A sustained effort should be made to ensure that doses to
individuals and to populations are maintained as low as reasonably
achievable. (See Note 3.)
3. The combined radiation doses incurred in any single year from
all sources of exposure covered by these recommendations should not
normally exceed a Radiation Protection Guide of 1 mSv (100 mrem)
effective dose equivalentb to an individual.c The Radiation
Protection Guide applies to the sum of the effective dose equivalent
resulting from exposure to external sources of radiation during a year
and the committed effective dose equivalent incurred from the intake of
radionuclides during that year. (See Notes 4 through 7.)
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\b\Effective dose equivalent is a derived quantity defined as
the risk-weighted sum of dose equivalents to specified organs and
tissues.
Dose equivalent is the product of the absorbed dose and a
quality factor which varies with the energy and type of radiation.
In the system of quantities of ionizing radiation historically in
use in the United States, the unit of dose equivalent is the
``rem.'' In the international system (S.I.), the corresponding unit
is the ``sievert'' (Sv). One sievert equals 100 rem.
The effective dose equivalent, HE, incurred in a given
period of time is the sum of the effective dose equivalent,
HE,ext, received from external exposure in that period and the
committed effective dose equivalent, HE,50, incurred from the
intake of radionuclides during that period. That is,
E=HE,ext + HE,50 =T
wt(H,ext + HT,50),
where wT is a weighting factor for organ or tissue T;
HT,ext is the dose equivalent from external irradiation
averaged over organ or tissue T; and HT,50, the committed dose
equivalent, is the sum of all dose equivalnts, averaged over organ
or tissue T, that may accumulate over an individual's anticipated
remaining lifetime (taken as 50 years) from radionuclides retained
within the body. The weighting factors satisfy the condition
T wt = 1.
The word ``dose'', when used alone in these recommendations, is
intended to carry the specific dose unit implied by the surrounding
text.
\c\The term ``individual'' means a typical member of any
critical group of most highly exposed members of the general public;
it refers to persons with typical consumption and other relevant
behavior habits.
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The Radiation Protection Guide may not be reasonably achievable in
some unusual situations. It may be exceeded temporarily in situations
that are not anticipated to recur chronically and when Recommendations
1 and 2 are satisfied, provided that the radiation dose incurred in any
year does not exceed 5 mSv (500 mrem) effective dose equivalent.
Continued exposure of an individual over substantial portions of a
lifetime at or near the level of the Radiation Protection Guide should
be avoided. This will normally be achieved through conformance of
individual sources to Recommendations 2 and 4.
4. Authorized limitsd for sources should be established to
ensure that individual and collective doses in current and future
populations satisfy the objectives of this guidance. These limits may
be developed for categories of sources or for specific sources.
Authorized limits for sources should normally limit doses to a fraction
of the Radiation Protection Guide for all sources combined. (See Note
8.)
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\d\Authorized limits are standards, regulations, or other
requirements established by a responsible authority for categories
of sources or for a specific source.
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Sources should be designed not to exceed authorized limits, and
should be operated so as to maintain doses to members of the general
public as low as reasonably achievable within such limits.
5. Risks associated with exposure of the general public to
radiation that may occur due to Federal agency decisions, and the
policies upon which these actions are based, should be made known to
the public as part of the decision process. The degree of detail and
type of information made available should be appropriate to the
potential radiation exposures involved. Information on risks should
encompass estimates of the risks of effects on health over time, and of
the uncertainties in such estimates. Information on policies should
include reference to this Federal radiation protection guidance for the
general public and other relevant Federal policies.
6. Assessments and records appropriate to the origin and magnitude
of expected doses and the exposed population should be performed and
maintained to demonstrate conformance with requirements which implement
these recommendations. The types and accuracy of methods and procedures
used in these assessments should be reviewed periodically to ensure
that they are appropriate and are being competently applied.
7. Exceptions to Recommendation 3 for planned exposure to radiation
should be made only for highly unusual circumstances, and only when the
Federal agency having jurisdiction has carefully considered the reasons
for making them in light of these recommendations. If Federal agencies
authorize any exception to these values, they should make it a matter
of public record.
Notes
The following notes are provided to clarify application of the
above recommendations:
1. Background radiation includes natural sources of background
radiation, such as cosmic radiation and radiation from naturally-
occurring radionuclides undisturbed by human activities, as well as
radiation from certain other sources of exposure beyond Federal
regulatory control, such as residual fallout from past nuclear
accidents and weapons tests.
2. People may, by technological means, enhance their exposure to
natural radiation sources that might otherwise be considered sources of
background radiation. Technologically-enhanced exposures to natural
radiation are usually controllable, in that they may be avoided or
reduced by taking reasonable actions. Unless specifically noted, these
recommendations apply to controllable technologically-enhanced exposure
to such natural radiation sources.
3. The admonition to maintain doses ``as low as reasonably
achievable'' includes consideration of economic and societal factors,
and applies to radiation exposure that may occur now or in the
foreseeable future. In making this judgment for doses to populations,
any incremental doses to individuals that are avoidable and which make
a significant contribution to collective dose should be considered.
4. Although indoor radon from proximate natural sources is
considered technologically-enhanced exposure to natural radiation,
Recommendations 3 and 4 of this guidance do not apply to such exposure.
Specific advice for protection against exposure to indoor radon is
provided in A Citizen's Guide To Radon (EPA document 402-K92-001 and
subsequent editions) and in other EPA technical publications.
5. The following values of the weighting factors wT may be
used to implement these recommendations:
Gonads........................................................... 0.25
Breasts.......................................................... 0.15
Red bone marrow.................................................. 0.12
Lungs............................................................ 0.12
Thyroid.......................................................... 0.03
Bone surfaces.................................................... 0.03
Remainder........................................................ 0.30
(``Remainder'' applies to the five other organs with the highest doses
(of the liver, kidneys, spleen, brain, thymus, adrenals, pancreas,
stomach, small intestine, and upper or lower large intestine, but
excluding skin, lens of eye, and extremities). The weighting factor for
each such organ is 0.06.)
6. The sum of weighted organ doses that comprises the effective
dose equivalent does not include an allowance for the induction of
fatal cancers in skin. In cases where dose to skin is large enough to
consider such effects, this may be done by adding to the effective dose
equivalent a terme that is the product of the skin dose equivalent
(averaged over the whole body) and a weighting factor wskin =
0.01.
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\e\Since the sum of the weighting factors is normalized to
unity, addition of a further factor would strictly require
adjustment of the other factors. In practice, the addition of this
small factor for skin does not warrant any change.
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7. The exposure-to-dose conversion factors tabulated in Federal
Guidance Report No. 11 (EPA-520/1-88-020), Federal Guidance Report No.
12 (EPA 402-R-93-081), and their subsequent editions should be used for
determining conformance to these recommendations. In addition,
dosimetric models and conventions and models for reference persons
specified by the International Commission on Radiological Protection
(ICRP) may be used. Under special circumstances, other factors may be
used when such factors are more appropriate on the basis of well-
established scientific evidence.
8. To ensure that specific sources or categories of sources,
including their installed control capability, are designed and operated
to achieve as low as reasonably achievable levels of exposure, a
variety of quantitative and qualitative analysis and decision methods
may be used to determine authorized limits. These, in addition to
considering radiation detriment and risk, and direct costs, may also
take into account societal and other economic factors. Statutory
requirements may impose additional constraints on the selection of
authorized limits.
[FR Doc. 94-31618 Filed 12-22-94; 8:45 am]
BILLING CODE 6560-50-P