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12
Conclusions and Recommendations
This chapter presents a summary of the most important conclusions and
recommendations developed from this study. The presentations in this chapter
are organized as follows: the central conclusions and recommendations of the
committee, including those which address the charge to the committee; the
context for regulation of TENORM; risk-assessment issues underlying the
regulation of TENORM; risk-management issues underlying regulations for
TENORM; the comparability of guidances and regulations applicable to
TENORM; and issues related to natural background radiation.
CENTRAL CONCLUSIONS AND RECOMMENDATIONS OF THE
COMMITTEE
1. This committee finds that the differences between the Environmental
Protection Agency (EPA) proposed and current guidelines for TENORM and
similar guidelines developed by other organizations have no scientific or
technical basis. There are some differences between various federal agencies in
how they perform risk assessment, but the differences in their guidelines
represent differences in policies for risk management.
2. This committee has not found a substantial body of relevant and
appropriate scientific information that has not been used in the development of
contemporary risk analysis for TENORM for purposes of developing and
implementing guidelines. We emphasize that properties of TENORM do not
differ from properties of other radionuclides in a way that would necessitate the
development of different approaches to risk assessment. This committee has
noted research needs related to improved understanding of the basis for high
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GUIDELINES FOR EXPOSURE TO TENORM
dose to low-dose extrapolation, particularly in the current use of the linear no-
threshold model for cancer induction. We also call for research related to the
improvement of exposure- and dose-assessment models through validation of
parameters, for better standardization of measurement methods for TENORM,
for better understanding of the effects of the chemical form and physical
structure of TENORM on dose, and for greater insight into and documentation
of the various uses and dispersal of TENORM.
3. The ALARA (as low as reasonably achievable) objective is the most
important factor in guiding agency actions aimed at radiation protection much
more important than established regulatory limits or goals. To the extent that the
ALARA objective is applied consistently to all exposure situations, all
guidances and regulations would be consistent, provided that it is recognized
that risks that are ALARA can vary considerably with the particular exposure
situation.
CONTEXT FOR REGULATION OF TENORM
1. All natural media earth, air, and water and biota, including
humans, contain naturally occurring radionuclides to some degree. Annual doses
received by residents of the United States from all sources of natural radiation in
the environment average about 3 mSv and are quite variable estimated to
range over a factor of about 4 for external sources and 20 for radon.
2. TENORM can be formed whenever NORM are moved from
inaccessible locations to sites where there is a greater possibility of human
exposure and whenever human activities process earth materials in a way that
concentrates NORM. TENORM radionuclide concentrations and volumes vary
greatly because of the diversity of sites, materials, and processes and because of
the substantial variations in leachability, sorption, and biologic availability.
Increases in radiation exposure from TENORM sources are typically local,
rawer than global, concerns.
RISK ASSESSMENT ISSUES UNDERLYING TENOR1VI REGULATION
1. The committee notes that for radiation sources related to TENORM,
including indoor radon, all regulatory and advisory groups have assumed about
the same risk coefficients. This reflects a general acceptance by the scientific
community of the linear no-threshold risk-extrapolation approach as a plausible
and useful means of developing public-health regulations. The committee does
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CONCLUSIONS AND RECOMMENDATIONS
245
not question the current suitability of the linear no-threshold model for
regulatory purposes or the need for additional research as a basis for change in
this model.
2. Exposure and dose or risk assessments used in developing standards
should be reasonably realistic; that is, they should not be intended to greatly
overestimate or underestimate actual effects for the exposure situations of
concern.
3. For the purpose of developing guidelines, it is appropriate to develop
stylized methods of exposure and dose or risk assessments for assumed
reference conditions, provided that the assumed conditions are reasonably
representative of the exposure situations of concern.
4. The chemical and physical forms of radionuclides in TENORM can
greatly influence their environmental mobility and biologic availability.
Exposure assessment for TENORM should consider such factors as
bioavailability, leachability, and radon-emanation rates. Those factors are
potentially important for developing guidelines for TENORM, and further
research to understand them better should be undertaken.
5. Risk assessments for TENORM should also consider exposures to
nonradioactive chemical agents that are often associated with TENORM.
RISK-MANAGEMENT ISSUES UNDERLYING TENORM GUIDELINES
1. All standards and guidances for radiation exposure are based
fundamentally on judgments about the acceptability of health risks to the public
or judgments about the achievability of health risks to the public. The latter,
embodied in the ALARA principle, has been the most important consideration
in controlling radiation exposures of the public for specific practices or sources,
provided that the dose limit for all controlled sources is met.
2. Other considerations that may be important in developing guidances
for radiation protection are the justification of practices (positive net benefits,
the measurability of radioactivity in the environment at levels corresponding to
the quantitative criteria in standards, and the magnitude and variability of
natural background radiation and naturally occurring radionuclides in various
environmental media.
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GUIDELINES FOR EXPOSURE TO TENORM
3. The committee notes that neither EPA, which has primary
responsibility for setting federal radiation standards, nor any other federal
agency with responsibility for regulating radiation exposures has developed
standards applicable to all exposure situations that involve TENORM. Instead,
federal regulation of TENORM is fragmentary, and many potentially important
sources of public exposure to TENORM are not regulated by any federal
agency.
4. The committee strongly cautions against generalizing numerical
guidance derived for a specific situation to another situation without sufficient
thought as to the applicability to the new circumstance. For example, the soil-
cleanup criteria developed under the Uranium Mill Tailings Radiation Control
Act have been extended to many other situations by state and federal regulatory
agencies, but many sources of TENORM have mineralogic characteristics and
processing histories that differ greatly from those of uranium mill tailings, and
therefore have different radon-emanation coefficients, leachability, and
bioavailability.
COMPARABILITY OF GUIDANCES AND REGULATIONS
POTENTIALLY RELATED TO TENORM
1. The implied health risks for the different radiation guidances and
regulations potentially applicable to TENORM vary over several orders of
magnitude.
2. Although consistency among the many guidances and regulations for
radionuclides is desirable, there are valid reasons not to expect it, including
agency differences in statutory and judicial mandates for standards, in the
regulatory bases of standards, in the applicability of standards, in the population
groups of primary concern to the standards, and in the considerations of natural
background in setting standards. Furthermore, the various guidances for
TENORM were developed at different times, and the basic assumptions about
radiation risk have changed.
3. The committee concludes that different guidances and regulations
should not be compared unless their bases and their applicability are well
understood and the quantitative criteria are interpreted properly. Otherwise,
misleading conclusions about the meaning and importance of differences in
implied risks might result.
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CONCLUSIONS AND RECOMMENDATIONS
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4. We conclude that the large differences in implied health risks among
the various guidelines and regulations do not necessarily mean that the different
standards are inconsistent with regard to the determination of an acceptable risk
to the public. The principle that exposures should be maintained ALARA,
economic and social factors being taken into account, appears to be the most
important factor in determining risks actually experienced for any controllable
exposure situation.
5. The more stringent mitigation levels for indoor radon recommended
by EPA, compared with those of most other countries and the National Council
on Radiation Protection and Measurements (NCRP) and the International
Commission on Radiological Protection (ICRP), do not result from differences
in scientific opinion about risks posed by exposure to indoor radon. Rather, they
result primarily from such factors as differences in average radon levels in
homes, differences in judgments based on cost-benefit analysis about levels of
radon that are reasonably achievable after mitigation, and differences in whether
the guidances focus primarily on reduction of risks to individuals receiving the
highest exposures or on reduction of population risks.
6. In most cases, EPA's current guidances on acceptable exposures to
TENORM other than indoor radon also are somewhat more restrictive than the
guidances developed by some of the states, the NCRP, and the Health Physics
Society. However, direct comparisons of these guidances are difficult and
potentially misleading, because of such factors as differences in whether
exposures to natural background are included, the difference between a
regulatory limit and a goal, and the use of a dose criterion in some cases but
activity concentrations of particular radionuclides in others.
7. The committee does not view the current differences in how the
agencies develop and carry out their recommendations, although perhaps
confusing, as necessarily resulting in important differences in protection of
public health. However, the committee does caution that, as the regulations are
developed and acted on, continued attention to the factors that affect radiation
dose and risk for specific TENORM situations is crucial for consistently
protective, cost-effective radiation control. In addition, further study on issues of
cost-benefit and other nonscientific concerns could be important in regulating
TENORM, given the magnitude and variability of natural background.
8. The committee has considered the disagreement between EPA and
the Nuclear Regulatory Commission over the adequacy of the Commission's
standards for unrestricted release of contaminated sites. The committee believes
that the disagreement is a matter of policy with no scientific or technical basis.
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GUIDELINES FOR EXPOSURE TO TENORM
The difference between EPA's proposed annual dose constraint of 0.15 mSv and
the Commission's dose constraint of 0.25 mSv cannot reasonably be regarded as
significant, particularly when the Commission also requires that the ALARA
objective be applied in reducing doses below 0.25 mSv. Furthermore, the
difference between 0.15 mSv and 0.25 mSv normally cannot be distinguished
reliably in a dose assessment. The disagreement over the need for a separate
groundwater-protection standard consistent with existing standards for
radioactivity in drinking water also is a matter of differences in policies for risk
management.
9. EPA and the Nuclear Regulatory Commission have worked together
to produce a valuable document on risk harmonization that effectively
summarizes their similarities and differences in the approach to radiation
protection. The committee commends the agencies for having done so and
recommends that they pursue this approach further. The committee recognizes
the different objectives and histories of the two agencies, but it is good public
policy to reconcile the existing differences in approaches to risk management
with an eye to better, more timely, and more efficient compliance activities by
the regulated community, and greater acceptance by Congress and the public.
ISSUES RELATED TO BACKGROUND RADIATION
1. The committee concludes that background radiation levels of NORM
are highly relevant to regulation of TENORM because the radionuclides being
regulated as TENORM are identical with those in nature. Arguments concerning
small differences in the target regulatory level at small fractions of the natural
background tend to pale into insignificance in comparison with natural
background levels and their local and regional variations.
2. Considering only external photon exposure, the committee notes that
EPA's proposed 0.15-mSv (15-mrem) standard is equivalent to an incremental
increase in the concentration of radium-226 in soil of about the usual natural
background level of 0.04 Bq/g (1 pCi/g). In view of the ubiquitousness of 226Ra
in soil and the substantial local variation in natural background, it is likely to be
difficult to implement a 0.15-mSv (15-mrem) soil-cleanup standard for radium,
particularly when the contamination is only marginally above the local
background. That is especially the case if potential exposures to indoor radon
are included in complying with the standard.
3. As a practical matter, the implications of existing levels and
variability of natural radionuclide concentrations and doses received by humans
should receive careful consideration in the regulation of TENORM.
Representative terms from entire chapter:
exposure situations
