Nuclear Health and Safety: Consensus on Acceptable Radiation Risk to the
Public Is Lacking (Letter Report, 09/19/94, GAO/RCED-94-190).
Differences exist in the limits on human exposure to radiation set by
federal agencies, such as the Nuclear Regulatory Commission and the
Environmental Protection Agency, raising questions about the precision,
credibility, and overall effectiveness of federal radiation standards
and guidelines in protecting public health. Taken together, the
radiation standards that have been developed reflect a lack of overall
interagency agreement on how much radiation risk to the public is
acceptable. GAO found at least 26 different draft or finalized federal
radiation standards or guidelines. Agencies also do not agree on how to
calculate radiation protection standards.
--------------------------- Indexing Terms -----------------------------
REPORTNUM: RCED-94-190
TITLE: Nuclear Health and Safety: Consensus on Acceptable
Radiation Risk to the Public Is Lacking
DATE: 09/19/94
SUBJECT: Standards evaluation
Radiation exposure hazards
Interagency relations
Radioactive waste disposal
Environmental monitoring
Hazardous substances
Regulatory agencies
Radiation safety
Safety regulation
Safety standards
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Cover
================================================================ COVER
Report to the Chairman, Committee on Governmental Affairs, U.S.
Senate
September 1994
NUCLEAR HEALTH AND SAFETY -
CONSENSUS ON ACCEPTABLE RADIATION
RISK TO THE PUBLIC IS LACKING
GAO/RCED-94-190
Lack of Consensus on Public Radiation Risk
Abbreviations
=============================================================== ABBREV
CIRRPC - Committee on Interagency Radiation Research and Policy
Coordination
DOE - Department of Energy
EPA - Environmental Protection Agency
FDA - Food and Drug Administration
GAO - General Accounting Office
ICRP - International Commission on Radiological Protection
NCRP - National Council on Radiation Protection and Measurements
NRC - Nuclear Regulatory Commission
OMB - Office of Management and Budget
WLM - working level month
Letter
=============================================================== LETTER
B-257016
September 19, 1994
The Honorable John Glenn
Chairman, Committee on Governmental Affairs
United States Senate
Dear Mr. Chairman:
As you know, over several decades federal agencies have developed
numerous radiation protection standards to help protect the public
from radiation exposures resulting from nuclear operations,
environmental contamination, and the disposal of nuclear waste. As
new standards continue to be developed, potentially immense
regulatory costs could be associated with decisions on acceptable
levels of radiation risk at U.S. nuclear facilities and sites, and
regulators may be faced with controversial trade-offs between
radiation health effects and affordability. To help address these
issues, you requested that we examine questions of consistency
related to federal agencies' radiation standards.
As agreed with your office, we specifically examined the degree of
consistency and compatibility in (1) the various limits on public
exposure to radiation included in the federal radiation standards and
(2) the various protective strategies associated with the standards.
In addition, we focused on whether the standards as a whole provide a
coherent, complete federal framework for public radiation protection.
RESULTS IN BRIEF
------------------------------------------------------------ Letter :1
Differences exist in the limits on human exposure to radiation set by
federal agencies,\1 raising questions about the precision,
credibility, and overall effectiveness of federal radiation standards
and guidelines in protecting public health. Taken together, the
radiation standards that have been developed reflect a lack of
overall interagency consensus on how much radiation risk to the
public is acceptable. Because the standards have different
regulatory applications and are based on different technical
methodologies, the estimated risks to the public that are associated
with these standards and guidelines vary considerably.
Over the years, agencies have not agreed on calculation methods and
radiation protection strategies to support their regulations and
guidelines. As a result, agencies may engage in time-consuming
disagreements on which protection levels are appropriate and at what
costs, and regulators may have difficulty in assessing clearly the
overall health impacts and cost-effectiveness of their radiation
standards.
Differences in radiation limits and risks, calculation methods, and
protective strategies reflect the historical lack of a unified
federal framework for protecting the public from radiation exposure.
Historically, interagency coordination of radiation protection
policy, principally through the Environmental Protection Agency (EPA)
and the presidential Committee on Interagency Radiation Research and
Policy Coordination, has been ineffective. Time-consuming and
potentially costly dual regulation of nuclear licensees has been an
issue between EPA and the Nuclear Regulatory Commission (NRC), and
standards for major sources of radiation have been lacking for years
because interagency disagreements have delayed the completion of
regulations. EPA and NRC have recently begun an effort to
"harmonize" their respective calculation methodologies and protective
strategies in order to avoid duplicative regulation. It remains to
be seen whether this effort will be sustained and broadened to
include effective participation by other agencies and the Committee
on Interagency Radiation Research and Policy Coordination.
--------------------
\1 The limits often involve dose limits and estimates of risks to the
public. Dose is a measure of radiation energy absorbed in tissue.
Risk, as generally used in this report, refers to the chance of a
premature human fatality from a radiation-caused cancer.
BACKGROUND
------------------------------------------------------------ Letter :2
Although low-level ionizing radiation surrounds us continually,\2 its
dangers remain elusive. We are immersed in nuclear radiation, mostly
from natural sources, including the cosmos and soil. Also, buildings
and certain industrial and governmental activities in the United
States regularly expose us to smaller amounts of radiation. On the
average, according to the National Council on Radiation Protection
and Measurements, the U.S. population receives a radiation dose of a
little more than one-third of a rem a year,\3 mostly from natural
background radiation. Exposure to small amounts of radiation is
believed to cause fatal cancer or hereditary defects in human beings,
but verification of this causal relationship is difficult. While
about 1 in 5 deaths that occur in the U.S. population are from all
types of cancer, the chance of dying from natural background
radiation (principally radon) in a lifetime has been estimated at 1
in 100. Exposures resulting from human-generated sources of
radiation (excluding exposures resulting from medical sources, which
generally are not clearly limited) pose a still smaller estimated
lifetime risk of cancer death.\4
Various federal laws and regulations (or standards) and nonbinding
guidelines on radiation protection are developed and administered by
EPA, NRC, and other agencies. EPA has a mandate dating from a 1970
presidential reorganization plan not only to regulate environmental
contamination, including radioactive contamination, but also to
advise the President on radiation policy. NRC is generally
responsible for regulating civilian uses of nuclear materials in the
United States. In addition, under the Atomic Energy Act, the
Department of Energy (DOE) issues and enforces standards for its
nuclear facilities around the country. Other participants in the
formulation of U.S. radiation protection policy include the
Committee on Interagency Radiation Research and Policy Coordination
(CIRRPC), within the President's Office of Science and Technology
Policy; the Office of Management and Budget (OMB); state governments;
and numerous nongovernmental and international organizations. (See
app. I.)
Federal radiation protection policy has been a matter of longtime
congressional interest. In 1980, in response to congressional
concerns about federal radiation protection policy coordination, the
President created a federal radiation policy council. However, the
council was soon thereafter abolished by the incoming presidential
administration. In 1982, you introduced legislation to create a
federal interagency council on radiation protection. This
legislation was not enacted, but the administration established
CIRRPC in 1984. More recently, Senate Governmental Affairs Committee
oversight hearings in 1993 and GAO reviews have indicated continuing
problems with various matters, such as the fragmented regulation of
medical radiation and years of delay in developing EPA's radiation
protection standards, because of low priority and a lack of
coordination. For example, in June 1993 we recommended that for
groundwater protection standards for inactive uranium-processing
sites, EPA and OMB meet to resolve differences impeding the issuance
of standards. In August 1994, we recommended that EPA complete work
on developing cleanup standards for radionuclides by the end of
1995.\5
--------------------
\2 Ionizing radiation is rays and atomic particles with enough energy
to knock electrons free from (or ionize) atoms.
\3 Rem is an abbreviation for roentgen equivalent man and is a unit
of measurement for radiation doses to human beings.
\4 The estimated chance is about 1 in 3,000, based on a risk factor
adopted by the International Commission on Radiological Protection.
\5 Radioactive Waste: EPA Standards Delayed by Low Priority and
Coordination Problems (GAO/RCED-93-126, June 3, 1993) and Nuclear
Cleanup: Completion of Standards and Effectiveness of Land Use
Planning Are Uncertain (GAO/RCED-94-144, Aug. 26, 1994).
DIFFERENCES IN FEDERAL
RADIATION EXPOSURE LIMITS
------------------------------------------------------------ Letter :3
The exposure limits and risks associated with the federal radiation
standards and guidelines differ, in part because the standards rely
on different calculation methods and protective strategies. The
standards often contain different numerical limits on radiation
exposure to the public and often reflect different estimated
acceptable risks. As a result, taken together the limits present an
imprecise picture of how much public health risk from exposure to
low-level radiation is acceptable.
DIFFERENT LIMITS AND
ASSOCIATED RISKS
---------------------------------------------------------- Letter :3.1
At least 26 different draft or final federal radiation standards or
guidelines contain numerical radiation limits, most administered by
either EPA or NRC. Some of the radiation limits agree numerically,
but others differ; still others are not expressed in comparable
units, as shown by the selected public protection standards listed in
table 1.\6 The estimated risks associated with these limits vary
considerably. (Standards and guidelines for public, source-specific,
and occupational exposure are listed in app. II.) The different
risks shown in the table are indicative of the standards' different
regulatory applications. In particular, the risks relate to various
sources of exposure, such as the uranium fuel cycle, miscellaneous
environmental sources, and occupational sources. The risks also
reflect various modes of controlling exposure, such as setting
requirements for nuclear site design and operations or setting limits
on releases, emissions, environmental concentrations, and doses.
For example, NRC's general public exposure limit of 0.1 rem per year
applies to regulated radiation sources, such as those used in
research laboratories and hospitals, and results in an implied
lifetime estimated risk of about 1 in 300. The lower (0.025 rem per
year) limit on public exposure from nuclear operations in EPA's
uranium fuel cycle regulation is for a single operational activity;
this limit is based primarily on the consideration of practicable
technologies for controlling radioactive effluents, according to an
EPA official. This limit results in an implied lifetime estimated
risk of about 1 in 1,000. EPA's still lower (0.01 rem per year) air
pollution limit is for a single environmental medium and is based on
EPA's legally mandated estimates of the level of risk that will (1)
be safe or acceptable considering only health-based factors and (2)
protect public health "with an ample margin of safety," considering
costs, feasibility, and other relevant factors.\7 EPA's air pollution
limit has an implied lifetime estimated risk of about 1 in 3,000.
These three examples demonstrate the lack of overall interagency
consensus on how much radiation risk to the public is acceptable.
Table 1
Differing Federal Limits on Public
Radiation Exposure
Estimated lifetime
Standard or risk of premature
guideline/agency Limit cancer death\a
------------------ ------------------ --------------------
General public 0.1 rem/yr. 1 in 300
limit/NRC
Low-level waste/ 0.025 rem/yr. 1 in 1,000
NRC
Indoor radon/EPA 4 picocuries per 1 in 40
liter
concentration
limit\b
Uranium mill tailings/EPA
------------------------------------------------------------
Radium 5 picocuries per 1 in 50\c
gram
Radon 20 picocuries per 1 in 14,000\d
square meter per
second release
rate
Uranium fuel 0.025 rem/yr. 1 in 1,000
cycle/EPA
Spent fuel, transuranic waste disposal/EPA
------------------------------------------------------------
All pathway 0.015 rem/yr. 1 in 2,000
Groundwater 0.004 rem/yr. 1 in 7,000
Containment 1,000 deaths in 1 in 36,000\e
10,000 years
Air pollution/EPA 0.01 rem/yr. 1 in 3,000
Drinking water/EPA (proposed)
------------------------------------------------------------
Radium 20 picocuries per 1 in 14,000
liter
concentration
limit
Radon 300 picocuries per 1 in 5,000
liter
concentration
limit
Beta/photon\f \0.004 rem/yr.\ 1 in 7,000
Superfund cleanup/ \Risk range goals 1 in 15,000 to 1 in
EPA of 10\-4 to 10\-6 1,500,000
\g
------------------------------------------------------------
\a For purposes of comparison, the estimated risks in the table are
derived from commonly used assumptions (e.g., a cancer death risk of
5x10\-4 per rem to an individual continuously exposed over a 70-year
lifetime). The estimated risks may differ from those derived by
agencies, which used various assumptions in setting standards. Some
estimated risks are to individuals, and others are to larger defined
populations. Risks are rounded.
\b A picocurie is one-trillionth of a curie. A curie is a unit of
radioactivity equal to 3.7x10\10 radioactive disintegrations per
second.
\c Based on exposure to an individual residing on-site after cleanup.
The estimated risk to an individual off-site could be considerably
less.
\d Based on average population exposure. According to EPA and DOE,
the estimated risk to a maximally exposed individual could be
considerably greater.
\e Based on an NRCs assumption of a population of 250,000.
\f Beta particle and photon radioactivity from man-made radionuclides
in community water systems.
\g 10\-4 to 10\-6 = 1 in 10,000 to 1 in 1,000,000 risk of cancer
incidence. In the risk column, risks have been converted to express
the cancer mortality risk. The dose limit is determined on a
site-specific basis, depending upon the exposure pathways,
radionuclide, total inventory, and site's characteristics.
Source: Derived by GAO in part from CIRRPC, NRC, EPA, and DOE data.
--------------------
\6 For purposes of comparison, the risks in table 1 have been derived
on the basis of commonly used assumptions, including a risk factor
adopted by the International Commission on Radiological Protection.
The use of different assumptions could result in considerably
different risk estimates.
\7 According to EPA's draft guidance on general public exposure to
radiation, limits on single sources of radiation should logically be
a fraction of general public protection limits.
DIFFERENT CALCULATION
METHODS BEHIND THE LIMITS
---------------------------------------------------------- Letter :3.2
Differences in the various radiation exposure limits point in part to
the lack of interagency agreement on the technical assumptions
underlying various standards. These assumptions are key elements of
the dose and risk calculation methods used by agencies in deriving
the limits. In practice, agencies' calculation methods often differ,
giving different results. These methods can be theoretical, drawing
upon scant actual data. They may incorporate different hypotheses,
scenarios, assumptions, and mathematical simulations (models).\8 For
example, EPA and NRC use different scenarios for depicting how human
exposure may occur, including different assumptions about prospective
human intrusion into a site and the period of human exposure.
Assumptions that result in overestimating the risk may sometimes be
used in these scenarios. Such overestimations can lead to levels of
regulatory dose and risk limitation that require large expenditures
for compliance but do not necessarily significantly reduce the health
risk to the public. Also, as a result of these methodological
differences, standards may be difficult to compare to one another,
and their overall technical credibility may be questioned.\9
To date, agencies have taken limited steps to ensure that their
calculation methods have sufficient consistency. For example,
interagency guidance exists on preferable dose and risk coefficients
to be used in calculations, but not on preferred environmental models
("pathway" and "exposure" models) to be used. According to EPA and
NRC, a degree of consistency exists in the limits and in the
technical methods supporting them, and both agencies are working to
further ensure such consistency. The two agencies recently
identified both similarities and differences in their technical
methods in a joint analysis, including differences in the risk levels
they have considered acceptable.\10
--------------------
\8 A major overall assumption is that even the smallest dose of
radiation may be harmful--a generally accepted but unproven
hypothesis.
\9 The details of uncertainties and inconsistencies in the technical
methods supporting the standards are discussed in app. IV.
\10 Generally, NRC has considered a lifetime risk of 1 in 1,000 to be
acceptable, while EPA has strived for a lesser risk of 1 in 10,000.
DIFFERENT PROTECTIVE
STRATEGIES BEHIND THE LIMITS
---------------------------------------------------------- Letter :3.3
Different limits and calculation methods are indicative of the
different protective strategies that agencies have used over the
years in their radiation standards and guidelines. Often these
strategies--or conceptual approaches--require that numerical dose and
risk limits be supplemented with considerations of economic, social,
technical, and other factors.
Agencies have independently developed different approaches, according
to different traditions and legal mandates. Some of their approaches
may be categorized as either "top down" or "bottom up." The top-down
protective strategy involves setting an "upper bound" or limit, but
reducing dose and risk well below it, in site-specific compliance
situations, to a reasonably achieved lower level; the limit is
reduced on the basis of various factors, such as economic and social
considerations and technical feasibility.\11 NRC and DOE have
consistently favored the top-down approach in their standards (for
example, in NRC's general public protection standard).
Conversely, the bottom-up strategy has been used to control certain
specific environmental radiation sources. It involves setting a
lower, relatively more stringent dose or risk goal (a desirable
target, not a limit). The goal is to be pursued through use of the
"best available technology" to control exposure or remove
environmental contamination. Under this approach, if the goal is not
achievable, on the basis of considerations of technical feasibility,
cost, and other factors, the regulator may decide to accept a less
stringent level of achieved protection. This strategy is reflected
in some EPA regulations, such as the regulation on drinking water
contamination. In addition, under the Atomic Energy Act and various
environmental laws, EPA implements numerous other protective
approaches.\12
Also, EPA uses different protective strategies drawn from the
separate traditions of regulating chemical and radioactive
contaminants. On the basis of its tradition of regulating chemicals,
EPA has generally set a risk of 1 in a million that an individual
will develop cancer in a lifetime as a goal for remediation\13 and
has considered a risk of greater than 1 in 10,000 to be potentially
excessive. In some cases, EPA has also used these risk goals in
connection with radiation protection.
Using the top-down, bottom-up, and other strategies, agencies have
set lower limits over the years. In so doing, they have increasingly
supplemented numerical dose and risk limits with considerations of
economic, social, technical and other factors in deciding on
acceptable human exposure levels. Such decisions incorporate input
from various interested parties, resulting in negotiated radiation
exposure protection levels that represent overall social value
judgments. In part because agencies use different calculation
methods and protective strategies, these negotiations can involve
time-consuming interagency disagreements on dose limits, risks, and
cost considerations. For example, recent negotiations between EPA
and DOE on cleaning up thorium contamination at a DOE Superfund site
in New Jersey in part involved technical arguments about whether the
cleanup level should be 5 or 15 picocuries per gram above natural
background concentration levels. The decision on the remediation
level included options involving multimillion-dollar differences in
projected cleanup costs.
Interagency guidance has not been adopted to help structure the
process of incorporating cost and benefit considerations into
agencies' protective strategies. As a result, regulators and others
are unable to assess clearly the overall health impacts and
cost-effectiveness of their strategies and standards.\14 While cost
and benefit analyses are important to agencies' protective
approaches, they can be complex and potentially controversial in use.
For example, they may address not only the risk and cost of serious
health effects, but also less quantifiable social factors. Such
factors may include ethical concerns, equitable sharing of costs and
benefits, perceived public aversion to radiation at any exposure
level, and costs and benefits that could accrue to people who have
been defined as not within the at-risk population. The analyses
supporting such considerations may be complex and quantitative, or
they may be simpler, involving professional judgment and social and
political considerations. In either instance, agencies may be
subject to criticism if their cost-benefit analyses are perceived as
being inequitable or unfairly placing monetary values on human
lives.\15
Because agencies have not agreed on dose and risk calculation methods
and protective strategies (including cost-benefit analysis approaches
to support these strategies), regulators may not have assurance that
their standards have better protected the public health at an optimal
cost. On the one hand, even though lower radiation limits may
involve costly implementation, they still may represent prudent
decision-making, because even the lowest human exposures to radiation
may be assumed to be potentially harmful. On the other hand, because
the relatively stringent protection levels in some federal radiation
regulations have not been definitely shown to be associated with
health effects in populations, it is not readily apparent that lower
limits have necessarily resulted in significantly better protection
of public health at an optimal cost. Thus, agencies' radiation
standards and protective approaches ultimately reflect an overall
lack of interagency consensus on how much radiation risk to the
public is acceptable.
This lack of consensus has implications for the difficult regulatory
decisions that EPA, NRC, DOE, and other agencies will face in
upcoming years as they develop new standards to address nuclear
cleanup and disposal at sites around the country. Such decisions may
involve trade-offs between affordability and radiation protection, as
well as potentially immense regulatory costs. Regulatory areas
involved in such decisions may include low-level waste, cleanup of
residual radioactive contamination, nuclear facility decommissioning,
high-level waste storage, and potentially even indoor radiation in
residences.
--------------------
\11 This strategy is often called the "as low as reasonably
achievable" approach.
\12 In general, the laws themselves do not prescribe either risk
limits or protective strategies, although they may imply the use of a
particular protective strategy.
\13 According to one estimate, this risk is in the range of the
estimated chance that a given airline flight will result in a crash
or that a person will be struck by lightning in his or her lifetime.
\14 The calculated dollar values associated with radiation risk
reduction may vary widely from one regulation to another. For
example, according to a 1992 OMB comparative analysis, in two EPA
standards (for radionuclides in uranium mines and for covering/moving
uranium mill tailings at active sites) such values ranged from about
$3.4 million to about $45 million per premature death avoided,
respectively.
\15 For the most part, agencies have not established preferred
regulatory cost-benefit ratios (for example, dollar values per
avoided dose) that they consider applicable to compliance with their
radiation standards. An exception is NRC's suggested benchmark of up
to $1,000 per person-rem, which is intended to guide licensees in
designing protection into nuclear reactors. This amount converts to
a estimated $2 million expended per hypothetical death avoided.
LACK OF A UNIFIED FRAMEWORK FOR
FEDERAL RADIATION PROTECTION
------------------------------------------------------------ Letter :4
Differing federal radiation exposure limits have resulted from a
historical lack of a unified interagency framework of radiation
protection standards and protective strategies. Because of
ineffective policy coordination over many years, agencies have to a
degree gone their own ways in radiation protection. As a result,
problems with overlapping regulation of nuclear licensees have
developed, and agencies have engaged in lengthy disagreements on the
merits of draft radiation regulations, leaving areas of public
protection without clear coverage for years.
For example, EPA and NRC, the two principal agencies involved in
issuing radiation standards, have engaged in ongoing disagreements on
jurisdictional and philosophical issues, including protective
strategies. Also, in recent years EPA and CIRRPC have coordinated
federal radiation policy ineffectively. Although both EPA and CIRRPC
have a coordinating role, EPA has a mandate to issue guidance and
advise the President on radiation health matters. According to the
Deputy Director of EPA's Criteria and Standards Division, Office of
Radiation and Indoor Air, while EPA has had the authority to take the
lead in formulating radiation policy, historically it did not do so.
Coordination between EPA and CIRRPC on radiation policy matters has
been and continues to be limited, and in general EPA deals directly
with other agencies on radiation policy rather than through the forum
of CIRRPC. Various federal and state officials whom we interviewed
said that the lack of interaction between EPA and CIRRPC has impeded
interagency coordination of radiation protection policy.
As a result of this historical situation, problems with overlapping
regulation of nuclear licensees have developed and become more
apparent. In some instances, radiation standards duplicate others or
potentially conflict with other agencies' responsibilities in their
coverage. In such cases, often involving EPA and NRC, time-consuming
clarification of responsibilities may be necessary and costly dual
regulation of licensees may occur.\16 In other cases, standards have
not been finalized for years, leaving areas of public protection
without clear limits. For example, several EPA regulations on the
handling and disposal of radioactive waste and cleanup of
contamination have been in development or under review for up to 10
years or more--some have still not been issued--because of such
issues as legal concerns, coordination, and the setting of
priorities.\17
Some EPA and NRC initiatives related to policy coordination have
recently been undertaken. For example, EPA has recently led an
interagency effort to develop federal cleanup standards for
radiologically contaminated sites, including DOE sites. Other
agencies involved in the effort include NRC, DOE, and the Department
of Defense. In April 1993, EPA and DOE signed an agreement under
which DOE would provide $1.5 million in funding to EPA for greater
resources to develop and complete the standards. Also, NRC, in
coordination with EPA, has been developing standards for
decommissioning NRC-licensed facilities. In addition, EPA has
developed draft presidential guidance on radiation protection for the
general public to replace existing guidance issued by the Federal
Radiation Council in 1960. The new guidance updates the suggested
limit on public exposure (from 0.5 rem to 0.1 rem annually), and it
makes various recommendations that EPA expects will clarify basic
considerations to be taken into account in the development of new
radiation standards--thereby promoting consistency among federal
agencies. According to an EPA official, the guidance will be
published for public comment in the Federal Register in the fall of
1994.
Furthermore, EPA and NRC agreed in a March 1992 memorandum of
understanding to, among other things, strive to avoid unnecessarily
duplicative or piecemeal regulatory requirements for NRC licensees
and to actively explore ways to harmonize risk goals and cooperate in
developing a mutually agreeable approach to risk assessment
methodologies for radionuclides. They intended to issue a joint
report in January 1994 describing their specific goals and efforts,
but the report is still in draft form. According to an EPA official,
it is unclear when the report might be finally issued. The draft
contains recommendations generally aimed at encouraging both agencies
to (1) better agree on risk limits and (2) harmonize their approaches
to radiation regulation.
These several efforts at policy coordination are important, but so
far they represent limited steps toward a unified, ongoing,
comprehensive framework for interagency radiation protection policy.
In particular, the EPA-NRC harmonization effort has only begun to
address and potentially resolve issues related to calculation
methods, protective strategies, and acceptable risks. EPA and NRC
officials said that the issues addressed in the harmonization effort
are challenging, and they could not predict the long-run success of
the effort. They agreed that the effort should at some point be
broadened to include other federal agencies.
--------------------
\16 For example, as discussed in app. I, potentially costly
conflicts have arisen between EPA's and NRC's regulations affecting
the nuclear medical community.
\17 Details of regulatory overlap and delays in completing standards
are discussed in app. I.
CONCLUSIONS
------------------------------------------------------------ Letter :5
The public's health and safety, potentially costly regulatory
decisions, and the general credibility of nuclear regulation depend
in part on the ability of EPA and NRC, along with other agencies, to
work toward achieving a more unified federal framework for radiation
protection standards. As radiation standards have become more
stringent over the years, regulators have been faced in an era of
budgetary constraints with decisions involving difficult, judgmental
trade-offs between limiting expenditures and reducing radiation risk
to the public. In such circumstances, agencies need to reach better
agreement on radiation dose and risk calculation methods as well as
the overall strategies they use in federal standards and guidance to
protect public health. In addition, they need ongoing radiation
protection policy guidance from EPA, in cooperation with other
agencies and CIRRPC. At present, it is apparent that agencies'
radiation standards and protective approaches ultimately reflect a
general lack of interagency consensus on acceptable radiation risk to
the public.
To date, agencies have taken limited steps to agree on dose and risk
estimation methods and protective strategies. EPA's and NRC's
efforts to better harmonize their standards and protective strategies
could bring important results if those efforts can be sustained.
However, the issue of differing protective strategies is complex, and
for many years EPA, NRC, and other federal agencies have not
effectively coordinated their radiation policies. Therefore, unless
the harmonization effort is given ongoing attention and broadened to
include the effective participation of other agencies and CIRRPC, it
may not go very far toward achieving interagency consensus on federal
radiation protection policy. In such an instance, congressional
reconsideration of the merits of the present federal interagency
framework for formulating and coordinating radiation protection
policy may be warranted.
RECOMMENDATION
------------------------------------------------------------ Letter :6
To better unify federal radiation protection policy, we recommend
that the Administrator, EPA, in cooperation with the Chairman, NRC,
take the lead in sustaining and broadening the ongoing EPA-NRC
harmonization effort to include the effective participation of other
agencies and CIRRPC in pursuing interagency consensus on preferred
radiation dose and risk calculation methods and radiation protection
strategies, as well as an overall consensus on how much radiation
risk to the public is acceptable.
SCOPE AND METHODOLOGY
------------------------------------------------------------ Letter :7
To develop this report, we interviewed knowledgeable EPA, NRC, DOE,
and CIRRPC officials and examined documents provided by them related
to radiation protection standards and radiation dose and risk
calculation. We also interviewed nongovernment officials with
knowledge in the area of radiation effects and examined technical
literature related to radiation dose and risk calculation methods and
protective strategies. For purposes of risk comparison, we compiled
a list of federal radiation standards and guidelines and calculated
the radiation risks associated with them, in part on the basis of
data from NRC, EPA, and CIRRPC.
AGENCY COMMENTS
------------------------------------------------------------ Letter :8
We distributed a draft fact sheet reflecting the contents of this
report to the mentioned above officials and numerous other
knowledgeable government and nongovernment officials in the area of
radiation protection for their informal review. Those providing
informal comments included EPA's Deputy Director, Criteria and
Standards Division, Office of Radiation and Indoor Air; branch chiefs
within NRC's Regulatory Applications and Low-Level Waste Management
and Decommissioning divisions; DOE's Director, Air, Water, and
Radiation Division, Office of Environmental Guidance; a senior
science-policy adviser at the Committee on Interagency Radiation
Research and Policy Coordination; state radiation control directors;
an official of the Natural Resources Defense Council; and members of
the National Council on Radiation Protection and Measurements and the
Health Physics Society. As requested, we did not obtain written
agency comments on the report.
On the basis of these officials' comments, which were generally
technical in nature, changes were made to improve the accuracy of the
report. Numerous commenters, including EPA, NRC, and DOE officials,
generally agreed that better coordination of federal agencies'
radiation dose and risk calculation methods and protective strategies
would be helpful. In addition, EPA and NRC officials concurred that
their ongoing harmonization effort should eventually include the
participation of other federal agencies.
---------------------------------------------------------- Letter :8.1
As arranged with your office, unless you publicly release its
contents earlier, we plan no further distribution of this report
until 30 days after the date of this letter. At that time, we will
send copies of this report to the Administrator, EPA, the Chairman,
NRC, and other interested parties. We
will make copies available to others on request. Please contact me
at (202) 512-3841 if you have any questions. Major contributors to
this report are listed in appendix V.
Sincerely yours,
Victor S. Rezendes
Director, Energy and
Science Issues
FRAMEWORK FOR CONTROLLING
RADIATION EXPOSURE
=========================================================== Appendix I
Sources of public exposure to radiation that are controlled under
federal regulations include emissions from the nuclear power industry
and federal production operations, miscellaneous environmental
sources, and commercial applications. In addition, occupational
exposures are subject to separate standards. The standards include
those that provide for general radiation protection under the Atomic
Energy Act of 1954 and those relating to subsequent laws passed to
control human exposure from specific practices not covered under that
act. Under Reorganization Plan No. 3 of 1970, the Environmental
Protection Agency (EPA) succeeded the Federal Radiation Council
(established in 1959 under section 274 of the Atomic Energy Act) and
assumed its duties of providing a federal policy on human radiation
exposure, advising the President with respect to radiation health
matters, and issuing environmental protection standards and guidance
for federal agencies. The Nuclear Regulatory Commission (NRC), as
the principal regulator of the U.S. commercial nuclear industry
since the dissolution of the Atomic Energy Commission in 1974, is
responsible for regulation of most civilian uses of nuclear materials
in the United States. In this role, it issues radiation standards
for public and occupational protection.
In addition, other agencies, including the Department of Energy
(DOE), the Department of Health and Human Service's Food and Drug
Administration (FDA), the Department of Labor's Occupational Safety
and Health Administration, and the Department of the Interior's Mine
Safety and Health Administration, regulate certain radiation sources
and practices. Federal agencies participate in health and research
related coordination initiatives through the Committee on Interagency
Radiation Research and Policy Coordination (CIRRPC), made up of 18
participating agencies and chartered in 1984 within the President's
Office of Science and Technology Policy. CIRRPC serves as a forum in
which the agencies' radiation policy officials can discuss and
resolve radiation policy issues. In addition, the Office of
Management and Budget (OMB) reviews agencies' proposed regulations,
including those related to radiation protection, prior to their
issuance.
In addition to the federal protection framework, states have a
regulatory role, and non-government and international organizations
have an advisory role. Some state responsibilities for regulating
radiation are related to materials that are not federally regulated,
and others have been assumed by the the states under agreement with
NRC. States coordinate their protection efforts with the federal
government through the Conference of Radiation Control Program
Directors. Other national and international organizations involved
in radiation protection matters include the congressionally chartered
National Council on Radiation Protection and Measurements (NCRP), the
National Research Council's Committees on the Biological Effects of
Ionizing Radiation, the International Commission on Radiological
Protection (ICRP), the United Nations Scientific Committee on the
Effects of Atomic Radiation, the International Atomic Energy Agency,
and the Nuclear Energy Agency of the Organization for Economic
Cooperation and Development.
EXAMPLES OF OVERLAPPING OR
INCOMPLETE COVERAGE
--------------------------------------------------------- Appendix I:1
Without a unified radiation protection policy framework, agencies
issue duplicative, potentially conflicting regulations. For example,
EPA, NRC, and DOE have issued potentially duplicative (and in some
respects potentially contradictory) regulations and guidelines
according to different laws and their individual agency
jurisdictions. All three have also issued limits on public exposure
to radiation. Also, EPA's limits on public exposure to uranium mill
tailings are virtually identical to those of NRC (both of which
implement the Uranium Mill Tailings Radiation Control Act), and both
of these regulations potentially duplicate mill-tailings-related
provisions of EPA regulations implementing the Clean Air Act. (All
three regulations set "design guide" limits on radon releases from
tailings piles at 20 picocuries per square meter per second.)
Overlapping standards reflect individual legal mandates and
independent development by agencies to fulfill their different
responsibilities.
Potentially duplicative regulations, administered by different
agencies, require clarification and may be costly for those
conducting nuclear operations to implement. For example, EPA and NRC
have been administratively engaged for years in addressing issues
related to their dual regulation of uranium mill tailings under the
regulations outlined above. Likewise, in regulating mixed hazardous
and radioactive wastes under both NRC's regulation for land disposal
of radioactive waste and the Resource Conservation and Recovery Act,
they are attempting to resolve issues pertaining to radioactive
materials that were not considered when that act was developed.
As another example, conflicts have arisen between provisions of EPA
and NRC regulations as applied to radioactive emissions generated by
operations of the nuclear medical community.\1 These regulations may
require the use of dual, potentially conflicting compliance
strategies by medical institutions. On the one hand, under NRC's
regulation, annual permissible releases of numerous radionuclides are
subject to specific quantitative regulatory limits. On the other
hand, under EPA's regulation, the licensee must supply data on annual
possession quantities or concentration levels, or use computer
models, to demonstrate compliance with a general annual atmospheric
exposure limit of 0.01 rem. Industry representatives estimated in
1990 that it would cost about $100 million annually to comply with
both NRC's and EPA's regulations.
Also, federal radiation standards are incomplete in their coverage,
in part because some major radiation sources are not clearly subject
to federal exposure limits. Such sources principally include natural
radiation and radiation used in the diagnostic and therapeutic
practice of nuclear medicine. These sources account for about 98
percent (83 percent and 15 percent, respectively) of all annual
radiation doses to the U.S. population. Among the principal natural
sources are radon (which accounts for about two-thirds of natural
background radiation), cosmic rays, other terrestrial radiation, and
in-body radiation. The principal medical sources are diagnostic
x-rays and accelerator-related radioisotopes used in nuclear
medicine.
In general, although natural sources are estimated to be a much
higher risk to the average individual compared to nuclear industry
related sources of radiation, they are not systematically controlled.
It is not considered practical to regulate natural background
radiation, although in some instances exposure to radon is regulated
because its natural presence in the environment has been altered by
human intervention. Also, EPA and the Mine Safety and Health
Administration have in place nonbinding guidelines and regulations,
respectively, on acceptable radon levels in mining operations, and
EPA has issued guidelines on indoor radon limits (4 picocuries per
liter) beyond which corrective actions are suggested.
Of the two principal medical sources, x-rays account for about
three-fourths of the average annual exposures to humans. To the
extent that medical practices release radioactive materials into the
environment, they come under applicable regulations administered by
the NRC and EPA. However, most medicine-related radiation exposure
is received by patients in quantities that are intentional (as with
diagnostic x-rays) and discretionary--not specifically limited in
dose. For example, under FDA guidance on diagnostic x-ray exposures,
the use of x-rays should maintain exposures at levels "as low as is
reasonably achievable without loss of requisite diagnostic
information."
Also, the disposal of wastes from certain radioactive materials used
in medical, industrial, military, and commercial applications is not
federally regulated. Such materials, including radium and certain
other naturally occurring or accelerator-produced materials, do not
come under NRC control under the Atomic Energy Act. The regulation
of these materials generally has been left to the individual states,
which in some cases have inconsistent requirements or do not regulate
them. Many states have expressed a need for federal standards for
the disposal of these materials. In the 1980s, EPA drafted such
standards under the authority of the Toxic Substances Control Act,
but it has not yet issued them, as discussed below.
--------------------
\1 40 C.F.R. 61 and 10 C.F.R. 20.
INCOMPLETE COVERAGE BECAUSE OF
INCOMPLETE REGULATIONS
--------------------------------------------------------- Appendix I:2
The lack of a unified radiation protection policy may also lead to
gaps in regulatory coverage because regulations have not been
completed in a timely manner. For example, as we reported in 1993,
several EPA regulations relating to handling and disposing of
radioactive waste have been envisioned for years but not completed
because of problems with legal concerns, coordination, and the
setting of priorities among agencies, including principally EPA, NRC,
DOE, and OMB.\2 The unfinalized regulations are as follows:
In 1985, EPA issued high-level waste standards. They were legally
challenged and partially remanded by a federal court in 1987, in
part for further consideration of their interrelationships with
the Safe Drinking Water Act. The regulations were finally
reissued, as applicable to DOE's Waste Isolation Pilot Plant, in
December 1993. EPA has a mandate under the Energy Policy Act of
1992, in consultation with the National Academy of Sciences, to
develop and issue separate high-level waste disposal standards
for a future site (possibly DOE's Yucca Mountain site) by the
end of 1994.
In 1983, EPA published notice of its intent to issue low-level
waste disposal standards, sent a draft to OMB for its review in
1988, and hoped to resubmit the standards to OMB by the end of
1993. According to an EPA official, these standards are still
in draft form, and EPA expects to submit them again to OMB in
the fall of 1994.
In 1984, EPA proposed to federally regulate the disposal of
naturally occurring and accelerator-produced nuclear wastes
under the Toxic Substances Control Act and submitted a draft
rule to OMB in 1988. However, DOE raised concerns that the rule
did not adequately address how such wastes would be disposed of
or who would be responsible for doing so. According to an EPA
official, there are no plans at present to resubmit a proposed
rule to OMB.
In 1983, EPA issued standards for active and inactive uranium
processing sites, but the groundwater provisions for inactive
sites were remanded in 1985, and EPA resubmitted them to OMB in
1987 and again in 1991. According to an EPA official, OMB
returned them to EPA in 1993, and EPA revised and resubmitted
them in May 1994.
In 1986, EPA published notice of its intent to develop standards
for cleanup of land and facilities contaminated with residual
radiation. As stated in our recent report, Nuclear Cleanup:
Completion of Standards and Effectiveness of Land Use Planning
Are Uncertain (GAO/RCED 94-144), EPA now plans to issue draft
standards for comment in the spring of 1995.
Technical and cost issues raised in the interagency review process
have also been a factor in the failure to complete these regulations.
For example, in 1988 NRC questioned EPA's draft low-level waste
standards because in its view the estimated health benefit from the
standards did not justify the costs. In 1991, DOE commented that the
proposed standards could be implemented only at very large costs,
with very little benefit. According to an NRC official, depending in
part on the regulatory protection approach adopted, low-level-waste
disposal costs at sites with larger waste quantities could be as high
as about $50 million per site.
Both technical issues and questions of regulatory consistency have
affected the development of EPA's high-level waste standards. EPA
developed "probabilistic" containment requirements for the standards
that required the implementing agency to predict the probability of
the radioactive releases occurring and the consequences of such
releases over 10,000 years. NRC and DOE raised various issues
concerning this requirement, including doubts about the feasibility
of attempting to make statistically valid predictions far into the
future. DOE and NRC eventually agreed that the standards probably
could be implemented after EPA added language to the standards that
did not require absolute proof of compliance.
In addition, on the basis of a legal challenge by environmental
groups and several states, the First Circuit Court of Appeals ruled
in 1987 that EPA, among other things, had not adequately considered
its own safe drinking water regulations in setting individual
protection limits in the high-level waste standards. The court
vacated and remanded the standards to EPA in part because of
deficiencies in their promulgation. Before EPA could complete its
revision of these provisions, in October 1992 the Congress enacted
legislation reinstating all but two parts of the original disposal
regulations and directing EPA to issue final high-level disposal
regulations that will be applicable to noncommercial high-level
nuclear waste. These final regulations were issued on December 20,
1993.
--------------------
\2 Radioactive Waste: EPA Standards Delayed by Low Priority and
Coordination Problems (GAO/RCED-93-126, June 3, 1993).
FEDERAL RADIATION EXPOSURE LIMITS
========================================================== Appendix II
Estimated lifetime
Standard or Type/effective risk of premature
guideline/agency date Limit cancer death\a
------------------ ------------------ ------------------ --------------------
General standards/guidelines
--------------------------------------------------------------------------------
1. General public/ Regulation (10 0.1 rem/yr. 1 in 300
NRC C.F.R 20), 1993
2. General public/ Guidance, 1960 0.5 rem/yr. 1 in 60
EPA
3. General public/ Proposed guidance 0.1 rem/yr. 1 in 300
EPA (draft)
4. General public/ Proposed 0.1 rem/yr. 1 in 300
DOE (draft) regulation (10
C.F.R. 834)
Source-specific standards/guidelines
--------------------------------------------------------------------------------
5. Uranium mill Regulation (10
tailings/NRC C.F.R. 40), 1985
Radium 226: 5 pCi/ 1 in 50\b
g
Radon: 20 pCi/ 1 in 14,000\c
m\2s
6. Reactor Regulation (10
effluent design/ C.F.R. 50, App.
NRC I), 1975
Liquid: 0.003 rem/ 1 in 10,000
yr. total body
Gaseous: 0.005 1 in 6,000
rem/yr. total body
7. High-level Regulation (10 0.1 rem/yr. 1 in 300
waste repository C.F.R. 60), 1983
operations/
NRC
8. Low-level Regulation (10 0.025 rem/yr. 1 in 1,000
waste/NRC C.F.R. 61), 1983
9. Air pollution/ Regulation (40 0.01 rem/yr. 1 in 3,000
EPA C.F.R. 61), 1989,
1991
10. Drinking water Regulation (40 Beta/photon\d\: 1 in 7,000
(interim)/ C.F.R. 141), 1977 0.004 rem/yr.\
EPA
10a. Drinking Proposed
water (draft)/EPA regulation (40
C.F.R. 141)
Radium: 20 pCi/l 1 in 14,000
Radon: 300 pCi/l 1 in 5,000
Beta/photon\d: 1 in 7,000
0.004 rem/yr.
11. Uranium fuel Regulation (40 0.025 rem/yr. 1 in 1,000
cycle/EPA C.F.R. 190), 1979-
83
12. Spent fuel, Regulation (40
high-level, C.F.R. 191), 1994
transuranic waste
disposal/
EPA
All pathway: 0.015 1 in 2,000
rem/yr.
Ground water: 1 in 7,000
0.004 rem/yr.\d
Containment: 1,000 1 in 36,000\e
deaths in 10,000
yrs.
13. Uranium mill Regulation (40
tailings/EPA C.F.R. 192), 1983
Radium 226: 5 pCi/ 1 in 50\b
g
Radon: 20 pCi/ 1 in 14,000\c
m\2s
14. Ocean dumping/ Regulation (40 Alpha emitters: Not available
EPA C.F.R. 220), 1977 1.35x10\-3 Ci/kg,
10\8 kg/yr. rate
15. Superfund Regulation (40 10\-4 to 10\-6 1 in 15,000 to 1 in
cleanup/EPA C.F.R. 300) risk range goals\f 1,500,000
16. Mining Regulation (40
effluents/EPA C.F.R. 440), 1983
Radium 226 Not available
(dissolved): 10
pCi/l/day
Uranium: 0.004 g/ Not available
l/day
17. Indoor radon/ Guidance 4 pCi/l action 1 in 40
EPA level
18. Low-level Proposed All pathway: 0.025 1 in 1,000
waste/EPA (draft) regulation (40 rem/yr.
C.F.R. 193)
19. Proposed 0.015 rem/yr. 1 in 2,000
Decommissioning/ regulation
NRC (draft)
20. Cleanup/ Proposed 0.015 rem/yr. 1 in 2,000
EPA(draft) regulation
Occupational standards/guidelines
--------------------------------------------------------------------------------
21. Occupational/ Regulation (10 5 rem/yr. 1 in 8\g
NRC C.F.R. 20)
22. Occupational/ Guidance, 1987 5 rem/yr. 1 in 8\g
EPA
23. Radon in Guidance, 1971 4 WLM/yr.\.h 1 in 16
uranium mines/EPA
24. Occupational/ 5 rem/yr. 1 in 8\g
DOE Regulation (10
C.F.R. 835), 1993
25. Under-ground Regulation (30 Radon: 4 WLM/yr. 1 in 16
mines/MSHA C.F.R. 57), 1977
26. Occupational/ Regulation (29 5 rem/yr. 1 in 8\g
OSHA C.F.R. 1910.96),
1971
--------------------------------------------------------------------------------
\a For purposes of comparison, the estimated risks in the table are
derived from commonly used assumptions (e.g., a cancer death risk of
5x10\-4 per rem to an individual continuously exposed over a 70-year
lifetime; for workers, 50-year exposure). The estimated risks may
differ from those derived by agencies, which used various assumptions
in setting standards and guidelines. Some estimated risks are to
individuals, and others are to larger defined populations. Risks are
rounded.
\b Based on exposure to an individual residing on site after cleanup.
The estimated risk to an individual off-site could be considerably
less.
\c Based on average population exposure. According to EPA and DOE,
the estimated risk to a maximally exposed individual could be
considerably greater.
\d Beta particle and photon radioactivity from man-made radionuclides
in community water systems.
\e Based on an NRC assumption of a population of 250,000.
\f 10\-4 to 10\-6 = 1 in 10,000 to 1 in 1,000,000 risk of cancer
incidence. The goals in the risk column have been converted to
express cancer mortality risk. The dose limit is determined on a
site-specific basis, depending upon exposure pathways, radionuclide,
total inventory, and site characteristics.
\g Based on a 50-year working lifetime.
\h WLM = working level month, equivalent to about 100 picocuries per
liter of radon in equilibrium with its progeny for 170 hours of
worker exposure.
Source: Derived by GAO in part from CIRRPC, NRC, EPA, and DOE data.
A principal source is "A Compendium of Major U.S. Radiation
Protection Standards and Guides: Legal and Technical Facts,"
prepared for CIRRPC by W. A. Mills, D. S. Flack, F. J.
Arsenault, and E. F. Conti (Oak Ridge Associated Universities, ORAU
88/F-111, July 1988).
COMPARATIVE RADIATION RISKS
========================================================= Appendix III
Table III.1 compares various estimated risks associated with selected
radiation standards and guidelines for public protection. It
expresses these risks as a fraction or multiple of the estimated risk
from natural background radiation (which has been assigned a value of
1 for comparison purposes). The table shows that some radiation
standards or guidelines are set considerably higher--and some
considerably lower, approaching zero--in comparison to the estimated
risks from natural background radiation.
Table III.1
Comparative Risks Associated With
Radiation Standards, Guidelines, and
Exposures
Fraction or
multiple of
natural
background Standard, guideline, or exposure
------------ ------------ --------------------------------
3.3 Uranium mill tailings standard
2.5 Federal residential radon
guidance
1.7 EPA general public guidance of
0.5 rem/yr.
1.0 Natural background (including
radon)
0.7 Average indoor radon exposure
0.3 General public standard of 0.1
rem/yr.
0.08 Environmental standard of 0.025
rem/yr.
0.02 Radium standard in drinking
water
0.01 Drinking water standard of 0.004
rem/yr
0.003 Negligible risk level per NCRP\a
0.000005 High-level waste containment
standard\b
------------------------------------------------------------
\a NCRP Report No. 91, 1987.
\b Based on average risk in the U.S. population.
Source: Adapted by GAO from D. C. Kocher, "Perspective on the
Historical Development of Radiation Standards," Health Physics, vol.
61, no. 4, 1991.
UNCERTAIN SCIENCE AND METHODS
BEHIND THE STANDARDS
========================================================== Appendix IV
Federal radiation limits are based in part on estimates of dose and
risk\1 as well as on economic and social policy considerations. The
estimation methods behind the limits can be theoretical, drawing upon
limited actual data on radiation sources and their effects on humans.
These methods incorporate various assumptions and mathematical
simulations (models), and agencies have taken only limited steps to
ensure that the many assumptions and models they use to conduct the
assessments are reasonably consistent.
--------------------
\1 Dose is a measure of radiation energy absorbed in tissue. Risk,
as generally used in this report, is the chance that a person will
die prematurely from a radiation-caused cancer.
UNCERTAIN SCIENCE
-------------------------------------------------------- Appendix IV:1
The science that supports the limits is complex, difficult, and
multidisciplinary. It involves conceptual modeling of the
interactions of low-level radiation with the surrounding environment
and the human body.\2 The limits often rely less on actual
measurement of such interactions than on judgments or assumptions.
For example, two basic parameters underlying the limits--radiation
dose and radiation risk--are often estimated rather than directly
measured, and they involve mathematical estimation methods that
incorporate unknowns and large uncertainties.\3
The estimation of a dose to a person living near a radiation source
includes examining the type and quantity of radioactive material that
might be released from the source, how it might move through the
environment and into contact with the person, and how radioactive
materials might be absorbed into body organs or tissue. To a large
extent, direct measurement or validation of these phenomena
(especially exposure) is not possible or practical. Instead,
detailed scenarios and conceptual models are developed--based on best
judgment and evidence--to explain these phenomena. Then, consistent
with the conceptual models, mathematical models (and the numerical
factors or parameters they require) are developed for determining
deposition into the aquatic or terrestrial environment by means of
various routes or "pathways," either directly to human beings or
indirectly through reconcentration in the food chain. Many details
of these conceptual and mathematical models must be inferred or
assumed in order to get a numerical result--a dose estimation.
The use of different assumptions can lead to large variations in
results. The use of "reasonable" versus "worst case" scenarios can
result in dose estimates that vary by up to 100 times or much more.
If an agency uses "realistic" assumptions, it may invite criticism
that its dose estimates do not adequately protect public health; the
use of conservative assumptions, on the other hand, can lead to large
expenditures on dose and risk limitation without necessarily bringing
compensating benefits in reduced health risk to the public. In the
past, OMB has argued that agencies have applied assumptions too
conservatively, thereby overstating risks by 1,000 or even a million
times. EPA policy in implementing Superfund has been that when in
doubt, the risk should be overstated rather than understated.
The estimated dose is used in estimating risk. Essentially, risk
estimation converts the dose into a numerical projection of the
chance that a given dose will cause premature cancer death. Because
the process of radiation carcinogenesis is understood mainly in
theoretical terms and has not been directly verified, risk
calculations rely on predetermined multipliers (estimates of risk per
unit dose called "risk factors") derived from research into the
incidence of radiation-caused cancers. Principally, such research
involves observations of the numbers of cancers of different kinds
that arise in irradiated groups. Through the use of statistical
estimation techniques, the cancer incidence detected in these groups
may be projected to the other populations. However, studies of
irradiated groups typically involve extrapolations--from larger to
lower doses, or from one population to another--whose validity may be
questioned, and they lack sensitivity--they are inherently unable to
detect small health effects, such as those associated with low-level
radiation. To some, a single numerical risk estimate gives a
misleading impression of precision because any such estimate is
likely to be based on highly uncertain data.\4
To illustrate the lack of sensitivity in such studies of irradiated
groups, using an International Commission on Radiological Protection
(ICRP) risk factor and an assumed 70-year lifetime, a continuous low
exposure level of 0.1 rem (the general federal public protection
limit) might result in 350 radiation-caused cancer deaths in a
population of 100,000 over a lifetime. As a practical matter, 350
additional radiation-caused cancer deaths in a U.S. population of
100,000 would probably not be detectable, given that about 20,000
deaths from all types of cancers could be expected to occur in that
population.
As a result, federal radiation limits (however precise they may
appear to be numerically) reflect a series of theories and
assumptions about radiation effects. They are inherently imprecise,
confronting fundamental scientific questions that may be answered
only incrementally in coming years. According to a CIRRPC official,
validation of low dose radiation effects may advance through
experimental studies of cancer at the cellular and molecular levels.
--------------------
\2 A low-level dose has been estimated to be somewhere below 10 rem.
It is not known for certain whether doses below this level are
detrimental to human health. The carcinogenic effects of low-level
radiation have not been directly proved. They have been predicted
statistically on the basis of higher doses to populations, such as
the Japanese survivors of World War II bombings. It is assumed that
even the smallest dose of radiation may be harmful, an assumption
commonly known as the linear no-threshold hypothesis.
\3 Even less direct knowledge exists about the impact of
nonradioactive pollutants in the environment.
\4 According to the National Council on Radiation Protection and
Measurements (Report No. 96, 1989), if the dose is accurately known,
best estimates of risk can be made within a statistical uncertainty
factor of about 2 for all cancers combined for whole-body external
radiation.
DIFFERENCES IN ESTIMATION
METHODS
-------------------------------------------------------- Appendix IV:2
Various theories, scenarios, and techniques have been developed among
agencies to help in estimating doses and risks. The estimation
methods and assumptions used by agencies in setting radiation limits
and assessing compliance with them have similarities and differences.
Methodological similarities include, for example, the fact that EPA
and NRC usually consider the same general pathways of exposure, and
both agencies translate exposure and intakes into dose and risk using
internationally accepted techniques. In addition, EPA has issued
federal guidance on parameters for agencies to use in calculating
external and internal exposure and dose. Likewise, CIRRPC has issued
guidance on risk factors that agencies may use in risk estimation.
Methodological differences include EPA's and NRC's use of different
exposure scenarios, including different assumptions about inadvertent
intrusion, reliance on institutional controls, and period of
exposure. Also, EPA, NRC, and DOE have different models for
estimating the dose to an individual living on a radiologically
contaminated site. The models incorporate differing assumptions and
give results that may differ considerably, by up to 100 times or much
more.\5 EPA and NRC use some different risk coefficients, and in some
cases they use considerably different dose and risk conversion
factors.
EPA, NRC, and DOE have issued separate guidance on estimating doses
and risks for the use of those implementing their regulations. For
example, NRC and DOE have developed generic models that are suggested
for use in environmental dose assessments. EPA has issued Superfund
risk assessment guidance and exposure assessment guidance. Also, NRC
has issued (1) a technical methodology for translating contamination
into dose and (2) Regulatory Guide 1.109, which prescribes models and
assumptions to be used in license applications for constructing
nuclear power reactors and in checking releases during operations
against design specifications. Also, under its air pollution
regulation, EPA requires the use of certain computer codes in
demonstrating compliance with regulatory requirements for airborne
radioactive emissions.
However, the use of particular exposure scenarios, exposure routes,
and assumptions for dose estimation is generally not prescribed in
regulations. In part, this reflects the idea that there is no simple
formula or "cookbook" for dose and risk estimation. On the other
hand, differences in agencies' methods may reflect on the technical
credibility of their dose and risk estimates and standards. In their
harmonization initiative, EPA and NRC are beginning to explore the
idea of ensuring the use of more consistent assumptions and
mathematical simulations in setting exposure limits and regulating
compliance with them. For example, they are considering the use of
the same dose and risk factors and the use of consistent exposure
scenarios.
--------------------
\5 For example, differences related to external dose, inhalation, and
ingestion pathways were found in a 1993 DOE-sponsored analysis.
MAJOR CONTRIBUTORS TO THIS REPORT
=========================================================== Appendix V
RESOURCES, COMMUNITY, AND ECONOMIC
DEVELOPMENT DIVISION, WASHINGTON,
D.C.
Jim Wells, Associate Director
Duane Fitzgerald, Nuclear Engineer
Gerald E. Killian, Adviser
Dave Brack, Evaluator-in-Charge
Victor J. Sgobba, Adviser