Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 106
7
Environmental Protection Agency Guidances and
Regulations for Naturally Occurring Radionuclides
The primary purpose of this chapter is to review existing and proposed
Environmental Protection Agency (EPA) guidances and regulations that apply
to control of routine exposures of the public to naturally occurring
radionuclides. As discussed in chapter 2, the naturally occurring radionuclides
of primary concern in radiation protection of the public include isotopes of
uranium, thorium, and radium and their radiologically important shorter-lived
decay products.
EPA guidances and regulations reviewed in this chapter include those
that apply either to TENORM or to naturally occurring radionuclides associated
with operations of the nuclear fuel cycle, which are not included in TENORM as
defined in this study. No distinction is made in this review between TENORM
and NORM associated with the nuclear fuel cycle because the intent is to
indicate the variety of approaches used by EPA in regulating naturally occurring
radionuclides for any exposure situations of concern. In chapter 10, EPA
guidances and regulations that apply specifically to TENORM are summarized
and compared with guidances for TENORS developed by other organizations.
The guidances and regulations considered in this review apply only to
situations in which routine exposures to naturally occurring radionuclides are
affected by human activities; they do not apply to naturally occurring
radionuclides in their undisturbed state. This review is not concerned with EPA
guidances on control of radiation exposures in the workplace (EPA 1987a) or
responses to accidental releases of radionuclides to the environment (EPA
1992a).
EPA's guidances and regulations that apply to control of routine
exposures of the public to naturally occurring radionuclides may be divided into
two categories:
106
OCR for page 107
GUIDANCES AND REGULATIONS FOR NORM
· Guidance on radiation protection of the public, which applies to all
specified controlled sources of exposure combined.
.
practices.
Guidance or regulations that apply only to specific sources or
107
This review of EPA guidances and regulations emphasizes the quantitative
criteria that apply to naturally occurring radionuclides and the basis for these
criteria.
In addition to the specific guidances and regulations, this chapter
discusses the health risks to the public that correspond to the quantitative criteria
in different guidances and regulations, the important issue of consistency of
standards in regard to limits on risk, and the relationship between the
quantitative criteria in the various guidances and regulations and the doses or
risks experienced in actual exposure situations.
GUIDANCE ON RADIATION PROTECTION OF THE PUBLIC
EPA is responsible for developing guidance for all federal agencies on
standards for radiation protection of the public. These standards apply to all
specified controlled sources of exposure combined, excluding indoor radon, but
do not apply to natural background radiation and to beneficial medical
exposures. EPA has issued proposed federal guidance on radiation protection of
the public (EPA 1994d) to replace the guidance developed many years ago by
the Federal Radiation Council (FRC 1961; 1960~. Although the proposed
guidance has not been issued in final form, the committee has assumed that it
represents EPA's current views on the basic, minimal requirements for radiation
protection of the public. Therefore, the proposed guidance is given greater
emphasis in this study than the existing FRC guidance.
EPA's proposed federal guidance on radiation protection of the public
includes the following provisions of interest to this study:
. There should be no radiation exposure of the general public
unless it is justified by the expectation of an overall benefit from
the activity causing the exposure.
· Doses to individuals and populations should be as low as
reasonably achievable (ALARA).
OCR for page 108
108
GUIDELINES FOR EXPOSURE TO TENORM
.
The annual effective dose equivalent to individuals from all
controlled sources combined, including sources not associated with
operations of the nuclear-fuel cycle but excluding indoor radon,
should not normally exceed 1 mSv (100 mrem).
· Annual effective dose equivalents to individuals up to 5 mSv
(500 mrem) may be permitted, with prior authorization, in unusual,
temporary situations.
· Continued exposure over substantial portions of a lifetime at
or near 1 mSv (100 mrem) per year should be avoided.
· Authorized limits for specific sources or practices should be
established to ensure that the primary dose limit of 1 mSv
(100 mrem) per year for all controlled sources combined and the
ALARA objective are satisfied, and the authorized limit for any
source or practice normally should be a fraction of the dose limit
for all controlled sources combined.
The provisions listed above would apply to naturally occurring
radionuclides, including TENORM, other than indoor radon, whenever
exposures of the public are affected by human activities. However, to ensure
compliance with these provisions, especially the primary dose limit for all
sources of exposure combined, exposures to human-made radionuclides also
would need to be taken into account.
EPA's proposed federal guidance was based in large part on
recommendations on radiation protection of the public developed previously by
the International Commission on Radiological Protection (ICRP 1977) and the
National Council on Radiation Protection and Measurements (NCRP 1987c). In
addition, the emphasis in the proposed guidance on the use of authorized limits
for specific sources or practices at a fraction of the primary dose limit for all
sources of exposure combined, to help ensure compliance with the primary dose
limit and the ALARA objective, conforms to current recommendations of ICRP
(1991) and NCRP (1993a).
The existing federal guidance on radiation protection of the public
(FRC 1961; 1960), which EPA's proposed guidance would replace, includes the
following provisions of interest to this study:
· There should not be any exposure to human-made radiation
without the expectation of benefit from such exposure.
OCR for page 109
GUIDANCES AND REGULATIONS FOR NORM
. Every effort should be made to encourage keeping radiation
doses as far below recommended limits as practicable.
· For external exposure, the annual dose equivalent to the whole
body of individuals should not exceed 5 mSv (500 mrem), and the
dose equivalent to the gonads for average individuals in exposed
populations should not exceed 50 mSv (5,000 mrem) in 30 y, that
is, an average annual dose of 1.7 mSv (170 mrem).
· For internal exposure, the annual dose equivalent to
individuals should not exceed 5 mSv (500 mrem) to bone marrow
and 15 mSv (1,500 mrem) to bone or the thyroid, and the annual
dose equivalents to these organs for average individuals in exposed
populations should not exceed one-third of these values.
109
EPA's proposed federal guidance on radiation protection of the public
differs from the existing FRC guidance in several important respects.
First, the proposed guidance is explicit that it would apply to all
controlled sources of exposure combined (except as noted), including sources
not associated with operations of the nuclear fuel cycle. The existing FRC
guidance is not explicit on this point and has not been applied consistently to
sources not associated with operations of the nuclear fuel cycle, especially to
important sources of exposure to TENORM (EPA 1 994d).
Second, the existing FRC guidance specifies dose limits for the whole
body and the critical organ, and separate dose limits are specified for external
and internal exposure. The proposed guidance would replace the dose limits for
the whole body and the critical organ and the separate dose limits for external
and internal exposure with a single limit on effective dose equivalent from
external and internal exposure combined. The effective dose equivalent is
intended to be proportional to stochastic risk posed by any exposure without
regard for the distribution of doses among different organs or tissues.
Third, in most cases, the limit on annual effective dose equivalent of
1 mSv (100 mrem) in the proposed guidance is expected to correspond to lower
allowable exposures than the existing FRC guidance on dose limits for the
whole body or the critical organ from either external or internal exposure. The
reduction in the maximum allowable exposures was based on information on the
risk per unit dose that was not available when the FRC guidance was developed
and on a judgment about an upper bound on acceptable risk posed by exposure
to all controlled sources combined (see chapter 5~.
Finally, the separate dose limit for the gonads of average individuals in
the FRC guidance, which was intended to limit the induction of severe genetic
effects in exposed populations, would no longer be specified. In the proposed
OCR for page 110
110
GUIDELINES FOR EXPOSURE TO TENORM
guidance, the genetic risk would be taken into account in the weighting factor
for the gonads used in defining the effective dose equivalent (ICRP 1977~.
The essential purpose of EPA's proposed federal guidance on radiation
protection of the public is to limit incremental health risks to exposed
individuals and populations to levels that society generally regards as
acceptable. In selecting the primary dose limit of 1 mSv (100 mrem) per year
from exposure to all controlled sources combined, EPA considered several
judgmental factors. These factors included the lifetime risk corresponding to
the limit on annual dose, the degree of additional protection that would be
achieved by the application of ALARA by regulatory authorities for specific
sources or practices and by the consideration of the possibilities for multiple
exposures to current and future sources, and the record on the operational
application of the ALARA objective in reducing actual doses to levels below
authorized limits (EPA 1994d).
The lifetime risk corresponding to the primary dose limit of 1 mSv
(100 mrem) per year can be estimated by assuming continuous exposure over
70 y at the dose limit and a risk of fatal cancers per unit dose for members of the
public of S x 10-s per millisievert (S x 10-7 per millirem) (EPA 1994c; NCRP
1993a; ICRP 1991~. On the basis of those assumptions, the lifetime risk of fatal
cancers would be about 4 x 10-3. This value is somewhat higher than the lifetime
risk of about 10-3 that ICRP (1977) judged to be an upper bound on acceptable
risk posed by radiation exposure on the basis of data on other involuntary risks
that the public has accepted in everyday life (see chapter 5~.
However, as emphasized in the proposed federal guidance (EPA
1994d), compliance with the primary dose limit of 1 mSv (100 mrem) per year
does not, by itself, provide acceptable radiation protection of the public;
compliance with the ALARA objective also is a central tenet of radiation
protection. Indeed, as a result of the establishment of authorized limits for
specific sources or practices at a fraction of the primary dose limit and further
vigorous application of the ALARA objective at specific sites, the average
annual effective dose equivalent to individuals in exposed populations within
80 km (SO miles) of operating nuclear facilities is only about 0.5 ,uSv
(0.05 mrem) (NCRP 1987a). That dose corresponds to a lifetime risk of fatal
cancers of only about 2 x 10-6, or lower by a factor of 2,000 than the risk
corresponding to the primary dose limit. Furthermore, doses to individuals
receiving the highest exposures, although they might substantially exceed the
average dose in exposed populations, normally are only about 10% of the
primary dose limit or less (EPA 1989d).
Thus, although the purpose of the proposed federal guidance is to limit
risks posed by radiation exposure, an acceptable risk is not defined by the
primary dose limit alone. For most exposure situations, the acceptability of risks
is defined primarily by application of the ALARA objective, which involves
OCR for page 111
GUIDANCES AND REGULATIONS FOR NORM
111
judgments about doses to individuals and populations that are reasonably
achievable for specific sources or practices and at specific sites. Even though
compliance with the ALARA objective can be defined to some extent by
authorized limits for specific sources or practices at a fraction of the primary
dose limit, application of the objective at each site is a process, not a result that
can be specified a priori in regulations.
An additional factor taken into account by EPA in judging that the
primary dose limit of 1 mSv (100 mrem) per year and reductions in dose below
the limit to meet the ALARA objective would provide acceptable risks to
individuals and populations was the unavoidable risk posed by exposure to
natural background radiation. The average effective dose equivalent from all
natural sources including cosmic rays, cosmogonic and terrestrial
radionuclides, radionuclides in the body, and indoor radon is about 3 mSv
(300 mrem) per year in the United States (see table 2.10~. The primary dose
limit proposed by EPA thus corresponds to about one-third of the average dose
from natural background radiation, for which the estimated lifetime risk of fatal
cancers is about 10-2. Although the average dose from exposure to natural
background does not provide a justification for the primary dose limit for all
controlled sources combined, it does provide a perspective for judging whether
the dose limit for all controlled sources is reasonable (see chapter 5~.
GUIDANCE AND REGULATIONS FOR SPECIFIC SOURCES OR
PRACTICES
EPA is authorized under several environmental laws to establish
guidance or regulations for controlling radiation exposures of the public to
specific sources or practices (see chapter 6~. As noted in the previous section,
authorized limits for specific sources or practices (also called source constraints
or dose constraints) are an important means of ensuring compliance with the
primary dose limit for all controlled sources combined and the ALARA
objective in radiation-protection standards for the public.
EPA's guidances and regulations for specific sources or practices can
be divided into the following categories (the legal authority for establishing
guidance or regulations in each category is given in parentheses):
· Operations of uranium fuel-cycle facilities (Atomic Energy
Act).
· Radioactivity in drinking water (Safe Drinking Water Act).
· Radioactivity in liquid discharges (Clean Water Act).
OCR for page 112
112
GUIDELINES FOR EXPOSURE TO TENORM
· Uranium and thorium mill tailings (Uranium Mill Tailings
Radiation Control Act; Atomic Energy Act).
· Radioactive waste management and disposal (Atomic Energy
Act).
· Remediation of radioactively contaminated sites
(Comprehensive Environmental Response, Compensation, and
Liability Act, CERCLA; Atomic Energy Act).
· Airborne emissions of radionuclides (Clean Air Act).
· Indoor radon (Indoor Radon Abatement Act).
In addition, EPA may, under the Toxic Substances Control Act
(TSCA), regulate naturally occurring and accelerator-produced radioactive
materials (NARNI), including TENORS, which are not subject to regulation
under the Atomic Energy Act; and NARM wastes also could be regulated under
the Resource Conservation and Recovery Act (RCRA). EPA has not developed
proposed regulations specifically for NARM under either TSCA or RCRA.
The following sections review existing or proposed guidances and
regulations for specific sources or practices developed by EPA Mat apply to
naturally occurring radionuclides. The relevant quantitative criteria in the
guidances and regulations are presented, and the bases for the criteria are
discussed. The criteria that apply to naturally occurring radionuclides, including
EPA's proposed federal guidance on radiation protection of the public discussed
above, also are summarized in table 7.1. After He discussions of the guidances
and regulations, the possibility of regulating NARM under TSCA or RCRA is
discussed.
OCR for page 113
G UIDANCES AND BEG ULA TIONS FOR NOW
Table 7.1. Summary of EPA guidances and regulations applicable to naturally occurring
radionuclidesa
113
Guidance or regulation Quantitative criteriab
=
Proposed federal Annual effective dose equivalent
guidance on radiation of 1 mSv
protection of the public
(EPA 1994d)C
Standards for operations Annual dose equivalent of
of uranium fuel-cycle 0.25 mSv to whole body,
facilities (40 CFR Part 0.75 mSv to thyroid, and
190) 0.25 mSv to any other organ
Interim standards for Concentration of 5 pCi/L for
radioactivity in 226Ra plus 228Ra~
community drinking
water systems (40 CFR Concentration of 15 pCi/L for
Part 141) gross alpha-particle activity,
including 226Ra but excluding
radon and uraniums
Proposed revisions of Concentration of 20 pCi/L for
interim standards for 226Ra and 228Ra separately
radioactivity in
community drinking- Concentration of 20 ~g/L for
water systems (EPA uranium
1997; 1991a)
Concentration of 15 pCi/L for
gross alpha-particle activity,
excluding 226Ra, uranium, and
222Rnd
Annual effective dose equivalent
of 0.04 mSv from all beta- or
gamma-emitting radionuclides,
excluding 228Ra
Comments
Dose limit applies to all
controlled sources of exposure
combined, excluding indoor
radon and beneficial medical
exposures.
Based on considerations of
maximum tolerable risk to
individuals and ability of
authorized limits for specific
sources or practices and
further application of ALARA
objective to reduce doses well
below limit.
Based primarily on doses
judged reasonably achievable
with available effluent-control
technologies.
Based primarily on cost-
benefit analysis for reducing
existing levels of naturally
occurring radionuclides in
drinking water.
Based primarily on revised
cost-benefit analysis for
reducing existing levels of
naturally occurring
radionuclides in drinking
water.
OCR for page 114
4
Table 7.1. (continued)
GUIDELINES FOR EXPOSURE TO TENORM
Guidance or regulation Quantitative criteria Comments
Standards for Concentrations in daily effluents
radioactivity in liquid of 10 pCi/L for dissolved 226Ra,
discharges (40 CFR Part 30 pCi/L for total 226Ra, and
440) 4 mg/L for uraniums
Average concentrations in daily
effluents over 30 d of 3 pCi/L for
dissolved 226Ra, 10 pCi/L for
total 226Ra, and 2 mg/L for
uraniums
Standards for uranium or Annual average release rate of
thorium mill tailings (40 222Rn to air of 20 pCi/m2 per
CFR Part 192) second or concentration of 222Rn
in air outside disposal site of
0.5 pCi/L
Average concentrations of 226Ra
in soil above background over
any area of 100 m2 of 5 pCi/g in
top 15 cm or 15 pCi/g below
15 cm
Concentration of radon decay
products indoors including
background of 0.03 WL, with
objective of 0.02 WLe
Indoor gamma radiation level
above background of 20 ,uR/hf
Concentrations in groundwater of
5 pCi/L for 226Ra plus 228Ra,
15 pCi/L for gross alpha-particle
activity, and 30 pCi/L for 234U
plus 23sU~
Annual dose equivalent from
thorium-processing operations as
in uranium fuel-cycle standards
(40 CFR Part 190)
Limits apply to liquid
discharges from mines or mills
used to produce or process
uranium, radium, or vanadium
ores.
Based primarily on available
effluent- control technologies.
Releases during uranium-
processing operations and
from uranium mill tailings
disposal sites before end of
closure period must comply
with dose constraint in 40
CFR Part 190 and
concentration limits for liquid
discharges in 40 CFR Part
440.
Based primarily on
background levels of
radioactivity in western
United States and objective of
reducing exposures of the
public to as close to
background levels as
reasonably achievable;
groundwater-protection
requirements are based on
current and proposed
drinking-water standards (40
CFR Part 141).
OCR for page 115
GUIDANCES AND HULA TIONS FOR NOW
Table 7.1. (continued)
115
Guidance or regulation Quantitative criteria Comments
Standards for 1~ ta: ~ cs m~u n~ be I
management and storage Nuclear Regulatory Commission
of spent fuel, high-level or Agreement States, annual dose
waste, and transuranic equivalent of 0.25 mSv to whole
waste (40 CFR Part 191 ) body, 0.75 mSv to thyroid, and
0.25 mSv to any other organ
For DOE facilities not regulated
by Nuclear Regulatory
Commission or Agreement
States, annual dose equivalent of
0.25 mSv to whole body and
0.75 mSv to any organ
Standards for disposal of Cumulative releases to accessible
spent fuel, high-level environment per 1,000 MTHM
waste, and transuranic of 100 Ci for 226Ra 234U 23sU
waste (40 CFR and 238U 10 Ci for 230Th and
,
Part 191)8 232Th; and 1,000 Ci for 2l0Pbh
Annual effective dose equivalent
in accessible environment from
all exposure pathways of
0.15 mSv'
Levels of radioactivity in
underground sources of drinking
water in accessible environment
as specified by MCLs in
drinking-water standards (40
CFR Part 141 )'
Standards for cleanup of Goal of compliance with
radioactively ARARs, TBCs, and lifetime
contaminated sites cancer risk of 10~; limits that
(CERCLA and 40 CFR must be achieved by cleanups
Part 300) without regard for other factors
are not specified
Based primarily on doses
judged reasonably achievable
with available effluent-control
technologies; dose constraint
is consistent with uranium
fuel-cycle standards (40 CFR
Part 190).
Cumulative release limits were
based on 1,000 health effects
in US population, which was
judged reasonably achievable.
Dose constraint for individuals
was based on judgment about
acceptability of risk and
feasibility of achieving
specified dose.
Groundwater protection
requirement was based on
general strategy of protecting
resource consistent with
current drinking-water
standards.
Based on goal of complying
with relevant requirements
under other environmental
laws and achieving
consistency with cancer risks
corresponding to other laws
and regulations (such as Safe
Drinking Water Act and Clean
Air Act).
OCR for page 116
116
Table 7.1. (continued)
GUIDELINES FOR EXPOSURE TO TENORM
Guidance or regulation ! Quantitative criteria T Comments i|
Standards for airborne Annual effective dose equivalent
emissions of of 0.1 mSv for many DOE and
radionuclides (40 CFR non-DOE federal facilities, but
Part 61) excluding dose from 222Rn and its
decay products, and for
emissions of 222Rn from
underground uranium mines
Annual emissions of deco from
elemental phosphorus plants of
2 or 4.5 Cih
Emission rate of 222Rn from
specified radium-bearing
materials of 20 pCi/m2 per
seconds
Guidance on radon in Mitigation for radon
homes (EPA and DHHS concentrations above 4 pCi/L~
1994) Mitigation for radon
concentrations of 2-4 pCi/L if
] concentrations can be reduced
below 2 pCi/L~
aGuidances or regulations that do not specifically apply only to naturally occurring radionuclides
apply to human-made and naturally occurring radionuclides combined. Guidances or regulations
that apply only to human-made radionuclides are not given in the table.
bCriteria expressed in terms of dose equivalent apply to individual members of the public. Criteria
expressed in terms of quantities other than dose are given in the units presented in the guidance or
Based primarily on lifetime
cancer risk to maximally
exposed individuals of 104
and average lifetime risk in
exposed populations of 10-6.
Based on protection of
individuals receiving highest
exposures and cost-benefit
analysis for reducing existing
levels of rar1nn in hc)meq
regulation, and the conversion to SI units is indicated in a footnote.
CProposed guidance would replace existing guidance of Federal Radiation Council (FRC 1961
1960), which essentially specifies limit on annual dose equivalent of 5 mSv.
41 psi = 0.037 Bq.
el Working Level (WL) = 2.08 x 10-s J/m3.
fl R= 2.58 x 10~ C/kg.
"Standards apply for 10,000 years after disposal.
hi Ci = 0.037 TBq.
Standard applies only to undisturbed performance of disposal system (that is, absent human
intrusion).
1 ;
OCR for page 146
146
GUIDELINES FOR EXPOSURE TO TENORM
Those elements are embodied, for example, in the requirements of the
Safe Drinking Water Act and CERCLA and their implementing regulations. The
Safe Drinking Water Act essentially sets a goal of zero risk to the public posed
by exposure to radionuclides and other carcinogens in drinking water, but the
goal clearly cannot be achieved at any cost. The act then requires that the legally
enforceable standards (MCLs) be set as close to the goal of zero risk as possible,
with technical feasibility and costs of removing radionuclides from public
drinking-water supplies taken into account. The requirements of CERCLA and
its implementing regulations (40 CFR Part 300) include compliance with
ARARs and a lifetime cancer risk of 10-4 as goals for remediation of
contaminated sites (Luftig and Weinstock 1997; Clay 1991), but these goals can
be relaxed on the basis of many considerations, including that achieving the
goals is not feasible.
It cannot be overemphasized that the concept of a limit, as embodied in
radiation protection standards for the public developed under the Atomic Energy
Act, is fundamentally different from the concept of a goal, as embodied in
radiation standards developed under some other environmental laws. A goal for
acceptable risk does not define any kind of a limit on acceptable (tolerable) risk
that must be met without regard for cost or other relevant factors. Therefore, it is
potentially misleading, and could be inappropriate, to compare quantitative
criteria in the form of limits with criteria that are goals. For example, it is not
particularly meaningful to compare the limit on lifetime cancer risk of about
4 x 10-3 corresponding to the primary dose limit of 1 mSv (100 mrem) per year
for exposure over 70 years in EPA's proposed federal guidance on radiation
protection of the public with the risk goal of 10-4 for cleanup of contaminated
sites under CERCLA unless the fundamental difference in concept between the
two is recognized.
An example of the importance of a judicial mandate in establishing
standards is provided by the standards for airborne emissions of radionuclides
developed under the Clean Air Act. The court of appeals mandated that the
standards be based on considerations of acceptable risks to the public, whereas
other standards for specific sources or practices developed by EPA have been
based primarily on considerations of the achievability of risks (cost-benef~t
analysis). However, the standards developed under the Clean Air Act are
reasonably consistent with most other standards that were based on the
achievability of risks, in part because the lifetime risks of about 10-4 to 10-6
judged by EPA to be acceptable for airborne emissions also were reasonably
achievable and because the risks judged by EPA to be acceptable for airborne
emissions were comparable with the risks corresponding to other standards that
were based on the achievability of risks.
OCR for page 147
GUIDANCES AND REGULATIONS FOR NORM
Differences in Primary Bases of Standards
147
As discussed earlier, some radiation standards were based primarily on
judgments about acceptable health risks to the public, and others primarily on
judgments about the achievability of risks. There is no a priori reason to expect
that risks corresponding to the two types of standards would be consistent.
The importance of the different bases of standards is illustrated by a
comparison of EPA's proposed federal guidance on radiation protection of the
public with the standards for radionuclides in drinking water. As indicated in
table 7.2, the drinking-water standards for naturally occurring radionuclides
correspond to lifetime risks of about 10-4, whereas the primary dose limit of
1 mSv (100 mrem) per year in the proposed federal guidance corresponds to a
lifetime risk of about 4 x 10-3. The primary dose limit is based on an assumption
about the maximum acceptable (tolerable) risk posed by radiation exposure
whereas the drinking-water standards (MCLs) are based essentially on a cost-
benefit analysis of removal of radionuclides from public drinking-water
supplies. In general, standards based primarily on risks judged to be acceptable
should not be compared with standards based primarily on risks judged to be
reasonably achievable unless the difference between the two concepts is
recognized.
Differences in Applicability of Standards
In many cases, the risks corresponding to various guidances and
regulations appear to be inconsistent essentially because the standards differ in
their applicability. Some of the ways in which differences in the applicability of
standards are important are discussed below.
Perhaps the most important difference in the applicability of standards
is shown by a comparison of EPA's proposed federal guidance on radiation
protection of the public-specifically, the primary dose limit of 1 mSv
(lOOmrem) per year, which applies to all controlled sources of exposure
combined except for indoor radon and medical exposures with any other EPA
guidances or regulations developed under any environmental laws, which apply
only to specific sources or practices. A standard for all sources of exposure
combined is not directly comparable with standard for a specific practice or
source. Indeed, except for indoor radon, the risks corresponding to standards for
specific sources or practices should be substantially less in most cases than the
risk corresponding to the primary dose limit for all sources combined (EPA
1994d). In this regard, it should be noted that no guidance or regulation for
hazardous chemicals specifies a limit on risk posed by exposure to all controlled
sources combined. That is, for hazardous chemicals, there is no standard
analogous to the primary dose limit in radiation-protection standards; rather, all
OCR for page 148
148
GUIDELINES FOR EXPOSURE TO TENORM
standards for hazardous chemicals in the environment apply only to specific
exposure situations. Furthermore, for any particular situation (such as
contaminants in drinking water or airborne emissions of hazardous air
pollutants), hazardous chemicals often have been regulated only individually.
A second important difference is that the various standards for specific
sources or practices apply to different exposure situations. Most standards for
specific sources or practices were based primarily on judgments about
environmental levels, releases, or doses (and therefore risks) that are reasonably
achievable for the exposure situations of concern (application of the ALARA
objective). There is no a priori reason to expect risks judged reasonably
achievable for one exposure situation (such as releases from operating nuclear
facilities) to be consistent with risks judged reasonably achievable for a different
situation (such as radioactive waste disposal). Indeed, it is primarily in the
interest of achieving some degree of consistency in regulation that the
quantitative criteria contained in standards that apply to different exposure
situations often are about the same.
A third important difference is that standards developed under the
Atomic Energy Act generally apply to all release and exposure pathways
combined for the exposure situations of concern, whereas standards developed
under other environmental laws often apply only to particular release and
exposure pathways. For example, the dose constraint for operations of uranium
fuel-cycle facilities (40 CFR Part 190) developed under the Atomic Energy Act
applies to all release and exposure pathways, whereas standards for radioactivity
in drinking water developed under the Safe Drinking Water Act (40 CFR
Part 141) apply only to a single environmental medium (water) and a single
exposure pathway, and standards developed under the Clean Air Act (40 CFR
Part61) apply only to airborne releases. The one exception for standards
developed under laws other than the Atomic Energy Act is the cancer-risk goal
of 10-4 for remediation of contaminated sites under CERCLA (40 CFR
Part 300~; in this case, the goal applies to all release and exposure pathways
combined at a particular site. In general, it should not be expected that the risks
corresponding to standards that apply only to a single release or exposure
pathway would be consistent with the risks corresponding to standards that
apply to all release and exposure pathways combined.
Differences in Population Groups of Primary Concern
Some standards are concerned primarily with protection of maximally
exposed individuals; others are concerned primarily with protection of whole
populations, that is, individuals in the population receiving an average exposure.
For a given exposure situation, doses and risks for maximally exposed
OCR for page 149
GUIDANCES AND GULL TIONS FOR NOW
149
individuals generally will be higher than those for average individuals in the
population. Therefore, the standards might differ substantially depending on the
population group of primary concern.
Examples of standards that are concerned primarily with protection of
maximally exposed individuals include the dose constraints in standards for
operations of uranium fuel-cycle facilities (40 CFR Part 190) and management
and disposal of spent fuel, high-level waste, and transuranic waste (40 CFR
Part 191~. Another example is the risk goal of 10-4 in standards for cleanup of
contaminated sites under CERCLA (40 CFR Part300~. The standards for
airborne emissions of radionuclides (40 CFR Part 61) took into account both the
maximum individual risk and the average risk in the exposed population, but the
dose constraint that applies to many sources is concerned primarily with
protection of maximally exposed individuals.
The clearest example of a standard that is concerned with protection of
whole populations, rather than maximally exposed individuals, is the
containment requirements for disposal of spent fuel, high-level waste, and
transuranic waste (40 CFR Part 191~. The limits on cumulative releases of
radionuclides over 10,000 y were based on an assumed number of health effects
in the entire US population, without regard for risks to individuals who might
reside near disposal sites, which are limited by a separate dose constraint. The
drinking-water standards for radionuclides (40 CFR Part 141) also are
concerned with protection of whole populations because the standards were
derived on the basis of a cost-benef~t analysis in which all individuals were
assumed to ingest the same amount of drinking water.
Another example of the importance of the population group of concern
in establishing standards is provided by current guidances on mitigation of
radon in homes, specifically the EPA action level of lSOBq/m3 (4pCi/L)
compared with the NCRP-recommended action level of about 370 Bq/m3
(10 pCi/L) discussed in chapter 8. EPA and NCRP both were concerned with
mitigation of risks to the relatively few individuals who reside in homes in
which the levels of radon greatly exceed the US average. However, the two
organizations arrived at different action levels largely because EPA also was
concerned with reduction of exposures in the greatest number of homes, and
EPA developed its action level on the basis of a cost-benefit analysis for
reduction of levels of indoor radon in all homes.
Differences in Considerations of Natural Background
In some cases, the health risks corresponding to various guidances and
regulations appear to be inconsistent essentially because some standards are
concerned with exposures to naturally occurring radionuclides and others are
not. Given the relatively high doses and risks posed by exposure to natural
OCR for page 150
150
GUIDELINES FOR EXPOSURE TO TENORM
background radiation (see chapter 2), the risks corresponding to various
guidances and regulations can differ substantially depending on whether the
standards include exposures to natural background.
The clearest examples of the importance of natural background in
establishing standards are the regulations for control and cleanup of residual
radioactive materials at uranium and thorium mill tailings sites (40 CFR
Part 192) and the federal guidance on indoor radon (EPA and DHHS 1994~.
Both standards are concerned with exposures to naturally occurring
radionuclides that have been increased by human activities, and knowledge of
background levels of naturally occurring radionuclides was important in
developing the standards. In either case, background levels result in relatively
high doses and risks, and it clearly is impractical for the standards to require
reductions in concentrations to levels below background. Therefore, it is
reasonable that the risks corresponding to the mill tailings standards and the
guidance on indoor radon are considerably higher than the risks corresponding
to other standards that do include contributions from natural background, such
as standards for operations of uranium fuel-cycle facilities (40 CFR Part 190)
and waste management and disposal (40 CFR Part 191~.
Other Considerations in Comparing Standards
Two additional factors have resulted in differences in risks
corresponding to various guidances and regulations for controlling radiation
exposures of the public.
First, the various guidances and regulations were developed at different
times, and judgments about the acceptability of doses and risks have changed
considerably over time. For example, when the standards for operations of
uranium fuel-cycle facilities (40 CFR Part 190) were developed in the middle
1970s, the primary dose limit for all controlled sources combined was 5 mSv
(SOOmrem) per year (FRC 1961; FRC 1960), the risk of fatal cancers was
assumed to be about 1 x 1O-s per millisievert (ICRP 1977), and standards for
radionuclides and hazardous chemicals developed under environmental laws
other than the Atomic Energy Act had not been issued or did not yet have an
influence on radiation standards developed under the Atomic Energy Act. Since
then, the primary dose limit for all controlled sources combined has been
reduced to 1 mSv (100 mrem) per year, the assumed risk of fatal cancers has
increased to 5 x 1O-s per millisievert (EPA 1994c, NCRP 1993a; ICRP 1991),
and a judgment by EPA that a lifetime risk of about 10- is an upper bound on
acceptable risk for specific sources or practices has been increasingly
incorporated into radiation standards on the basis of precedents in regulations
developed under other environmental laws (such as the Safe Drinking Water
Act, the Clean Air Act, CERCLA). Thus, there has been a tendency in recent
OCR for page 151
GUIDANCES AND REGULA TIONS FOR NORM
151
years to develop increasingly stringent radiation standards, as illustrated by
EPA's use of a dose constraint of 0.15 mSv (15 mrem) or 0.1 mSv (10 mrem)
per year, in contrast with the earlier use of a dose constraint of 0.25 mSv
(25 mrem) per year.
Second, the dosimetric quantities used in radiation standards have
changed over time. The earliest standards were expressed in terms of dose to the
whole body or the critical organ. A weakness of this approach is that the dose
criteria generally do not correspond well to a particular risk, especially for
nonuniform irradiations of the body. However, later standards are expressed in
terms of the effective dose equivalent, which was intended to be proportional to
risk for any uniform or nonuniform irradiations of the body (ICRP 1977~. The
differences between organ doses and the effective dose equivalent are important
mainly for ingestion and inhalation exposures. For most radionuclides, the
effective dose equivalent per unit activity intake is substantially less than the
dose to the critical organ; furthermore, the ratio of the two doses depends on the
particular radionuclide (Eckerman and others 1988~. But those differences are
important only if dose criteria are compared; they are not important when the
corresponding risks are compared, provided that conversion of organ dose to
risk takes into account the dose in all tissues irradiated.
Summary of Issues of Consistency of Standards
There are several important reasons why the risks corresponding to the
many guidances and regulations for controlling radiation exposures of the public
appear to be inconsistent and why it is unreasonable to expect the risks to be
consistent. The considerable variability in risks embodied in the various
guidances and regulations is explained in large part by differences in legislative
and judicial mandates for setting standards, differences in the primary bases of
standards, differences in the exposure situations to which the standards apply,
differences in the population groups of primary concern, and differences in the
accounting of natural background radiation.
The important conclusion to be drawn from these discussions is that
risks corresponding to different guidances and regulations should not be
compared unless the bases of the standards and their applicability are well
understood and the standards are interpreted properly. Otherwise, inappropriate
and misleading conclusions about the meaning of differences in risks embodied
in the standards can result.
OCR for page 152
152
GUIDELINES FOR EXPOSURE TO TENORM
RELATIONSHIP BETWEEN STANDARDS AND DOSES
EXPERIENCED
Previous discussions in this chapter and chapter 5 have addressed the
primary bases of standards (limits on levels of radionuclides in environmental
media, releases to the environment, doses, or risks) in guidances and regulations
for controlling radiation exposures of the public and the consistency of the
standards with regard to the corresponding lifetime risks. This section considers
the important question of the relationship between the standards and the doses
and risks that would be experienced by exposed individuals and populations.
These considerations provide important insights into the single unifying
principle namely, the ALARA objective-that is the most important in
determining actual risks, irrespective of the differences in risks corresponding to
the various quantitative criteria in guidances and regulations.
A discussion of the quantitative criteria in guidances and regulations
that does not consider other factors that are important in controlling exposures
of the public gives the impression that the criteria by themselves defame
acceptable risks. That impression is misleading. Irrespective of the particular
environmental law under which any guidance or regulation is developed, the
doses and risks experienced by exposed individuals and populations are not
determined primarily by compliance with the quantitative criteria alone. This
important point is illustrated in the following paragraphs.
EPA's proposed federal guidance on radiation protection of the public
(EPA 1994d) incorporates the three basic principles of radiation protection set
forth by ICRP (1991) and NCRP (1993a):
· Justif cation of exposures (positive net benefit).
· Reduction of exposures of individuals and populations to as low
as reasonably achievable (ALARA), economic and social factors
being taken into account, also referred to as optimization of
exposures (ICILY 1991; 1977~.
· Limitation of dose to individuals from all controlled sources
combined.
The ALARA objective is implemented in part by establishing standards for
specific sources or practices that limit doses for the exposure situations of
concern to a fraction of the dose limit for all controlled sources combined, and
further site-specific reductions in dose based on ALARA considerations
OCR for page 153
GUIDANCES AND ~GUlATIONS FOR NOW
153
generally are required. The important point is that the ALARA objective
essentially defines a site-specif~c process for dose reduction, and the result of
the process generally cannot be defined and quantified in advance in
regulations.
The power of the ALARA objective in reducing doses to the public is
seen by examining doses that result from operations of nuclear facilities that are
regulated under the Atomic Energy Act. The average individual dose in exposed
populations is only about 0.05% of the primary dose limit for the public of
lmSv (lOOmrem) per year from all controlled sources combined (NCRP
1987a); and doses to individuals who receive the highest exposures normally are
no more than about 10% of the primary dose limit and often are substantially
less (EPA 1989d). Therefore, for the important case of releases from operating
nuclear facilities, the doses and risks experienced by most members of the
public are determined largely by vigorous application of the ALARA objective,
but the primary dose limit and even, in many cases, the authorized limits for
specific sources or practices at a fraction of the dose limit are rather unimportant
in determining actual doses and risks.
A similar example is provided by the requirements for cleanup of
contaminated sites under CERCLA and its implementing regulations (40 CFR
Part 300~. In considering acceptable risks at contaminated sites, considerable
attention normally is given to the preliminary remediation goals, including the
goal for lifetime cancer risk of 10-4 (Luftig and Weinstock 1997; Clay 1991~.
However, far less attention has been given to the result that the negotiated
cleanup levels at most sites, as incorporated in the ROD, correspond to risks
substantially above the goal of 10 ~ (EPA 1994b; Baes and Marland 1989~. The
actual cleanup levels judged to be acceptable at any site are based on a decision
process that is similar to applications of the ALARA objective under the Atomic
Energy Act. Therefore, for the important case of cleanup of contaminated sites,
the acceptable risks at any site are determined primarily by site-specif~c
application of the ALARA objective, not by the risk goal specified in
regulations.
Another example is provided by the standards for radioactivity in
drinking water (40 CFR Part 141) developed under the Safe Drinking Water
Act. These standards are important because they apply to drinking-water
systems used by more than half the US population and generally are being
applied to protection of groundwater resources at new waste-disposal sites and
at contaminated sites undergoing remediation. Although the standards specify
limits (MCLs) on allowable radioactivity in community drinking-water systems,
it is important to emphasize that the MCLs were based on judgments about
levels of radioactivity that could be achieved, given existing levels in sources of
drinking water throughout the United States and the effectiveness of available
methods for water treatment, rather than an a priori judgment about acceptable
OCR for page 154
154
GUIDELINES FOR EXPOSURE TO TENORM
risks posed by drinking water. Therefore, the MCLs are based essentially on
ALARA considerations. Furthermore, the drinl~ing-water standards are subject
to change periodically on the basis of reconsideration of the costs and benefits
of water treatment (EPA l 991 a).
These discussions illustrate the following important points. Although
guidances and regulations for controlling radiation exposures of the public
contain quantitative criteria that define limits or goals for acceptable doses or
risks for the exposure situations of concern, the doses and risks that would be
experienced by individuals and populations are, in most cases, not determined
by these criteria. For most important exposure situations, actual doses and risks
that would be experienced are determined primarily by application of an
ALARA process, whose outcome generally cannot be quantified in regulations.
In most cases, actual limits or goals for dose or risk specified in guidances and
regulations, although they represent important statements of principle and
although they define an upper or lower bound on dose or risk for applying the
ALARA objective, are relatively unimportant in determining actual outcomes.
Viewed in that way, all guidances and regulations for controlling
radiation exposures of the public developed under any laws have as their
unifying principle the objective that exposures from any source or practice
should be as low as reasonably achievable (ALARA). To the extent that the
ALARA objective is applied consistently in all cases and it is recognized that
doses and risks that are ALARA can vary considerably depending on the
particular source or practice, all guidances and regulations will be consistent
with regard to doses and risks actually experienced.
SUMMARY
This chapter has reviewed EPA's existing or proposed guidances and
regulations that apply to control of routine exposures of the public to naturally
occurring radionuclides. No particular distinction has been made in this review
between standards for naturally occurring radionuclides associated with
operations of the nuclear fuel cycle, which are developed under the Atomic
Energy Act, and standards for TENORM, which are developed under
environmental laws other than He Atomic Energy Act and are the main concern
of this study. This review has emphasized the standards that apply to naturally
occurring radionuclides and the bases of the guidances or regulations.
This chapter also discussed the health risks corresponding to the
quantitative criteria in the guidances and regulations that apply to naturally
occurring radionuclides. The risks corresponding to the different guidances and
regulations vary over several orders of magnitude, owing primarily to:
OCR for page 155
G UIDANCES AND REG ULA TIONS FOR NORM
· Differences in statutory and judicial mandates for standards,
especially the difference between the traditional regulatory approach
under the Atomic Energy Act, which emphasizes a limit on radiation
dose and reduction in doses below the limit to as low as reasonably
achievable (ALARA), and the regulatory approach under other
environmental laws. These laws often emphasize a goal for risk and
allowance for an increase (relaxation) in risks above the goal based
primarily on technical feasibility and cost.
· Differences in the primary bases of standards, that is, the
consideration that some standards are based primarily on an a priori
judgment about risks that are acceptable whereas other standards are
based primarily on a judgment about risks that are reasonably
achievable.
· Differences in the applicability of standards, especially the
considerations that some standards apply to all sources of exposure
combined, whereas other standards apply only to specific sources or
practices. The various standards for specific sources or practices
apply to different exposure situations with different risks that are
reasonably achievable.
· Differences in the population groups of primary concern in
developing standards, particularly whether the standards emphasize
protection of maximally exposed individuals or protection of
individuals who receive the average dose in exposed populations.
· Differences in the considerations of natural background,
especially whether background levels of radioactivity are important
in establishing the standards.
155
It is important to understand those factors when judging the meaning of
differences in health risks corresponding to the various guidances and
regulations.
An important conclusion from the discussions in this chapter is that the
large differences in health risks corresponding to the various EPA guidances and
regulations do not necessarily mean that the different standards are inconsistent
with regard to defining an acceptable risk to individuals or populations. Without
regard for the differences in standards, as summarized above, the principle that
exposures of individuals and populations should be ALARA is the most
important factor in determining risks actually experienced for any controllable
exposure situation. That is, largely without regard for the limits or goals
OCR for page 156
156
GUIDELINES FOR EXPOSURE TO TENORM
specified in various guidances and regulations, application of the ALARA
objective is the most important factor in determining acceptable risks.
Therefore, to the extent that the ALARA objective is applied consistently to all
exposure situations, all guidances and regulations would be consistent with
regard to risks actually experienced, provided that it is also recognized that risks
that are ALARA can vary considerably depending on the particular exposure
situation.
Representative terms from entire chapter:
drinking water
