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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

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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).

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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.

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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

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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

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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).

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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.

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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.

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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).

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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).

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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 ;

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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.

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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

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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

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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

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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

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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.

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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

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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

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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:

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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

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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.