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10 Comparison of Current Guidances for TENORM in the Environment INTRODUCTION Chapters 7-9 of this report discussed guidances for naturally occurring radionuclides and TENORM in the environment developed by regulatory authorities in the United States and other countries and by national and international advisory organizations, such as the National Council on Radiation Protection and Measurements (NCRP), the Health Physics Society (HPS), the International Commission on Radiological Protection (ICRP), and the International Atomic Energy Agency (L\EA). For consistency with the purpose of this study, guidances developed by the Environmental Protection Agency (EPA) were considered separately from guidances developed by other organizations. This chapter presents summary comparisons of EPA guidances specific to TENORM with the guidances for TENORM developed by other regulatory or advisory organizations. As discussed in chapter 1, TENORM refers to naturally occurring radioactive materials (NORM) not regulated under the Atomic Energy Act whose radionuclide concentrations or potential for exposures of individuals or populations have been increased by human activities. In comparing EPA guidances for TENORM with guidances developed by other organizations, indoor radon is considered separately from other TENORM. This distinction is based on historical precedents in developing guidance on radiation protection. As described in chapter 1, it has been maintained essentially because the relationship between the increased risk of lung cancer and exposure to short-lived radon decay products in air can be estimated, with some uncertainty, directly from epidemiological studies in various groups of miners (ICRP 1993b; National Research Council 1988) 204

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COMPARISON OF CURRENT GUIDANCES FOR TENORM 205 without the need to estimate the dose to radiosensitive tissues of the lung from irradiation by alpha particles following inhalation intakes and the risk per unit dose from alpha particles. The availability of epidemiological data which directly links cancer risk with concentrations of short-lived radon decay products in air bypasses the need to consider the complexities and attendant uncertainties in describing physical and biological processes in the lung following inhalation of radionuclides, which are particularly important for alpha emitters (ICRP 1994~. A dosimetric approach to estimating lung cancer risks from radon also requires assumptions-for example, the deposition of radon decay products in the respiratory tract and the particular target cells at risk-that may be difficult to verify. Thus, both the BEIR IV Committee (National Research Council 1988) and UNSCEAR (1993) did not endorse the use of dosimetric models for calculating risks of lung cancer from exposure to radon. Radon is unique because for no other radionuclides, including other naturally occurring alpha emitters (radium, uranium, and thorium), can a complete characterization of cancer risk be obtained without estimating the dose per unit exposure and the risk per unit dose. INDOOR RADON Guidances for mitigation of exposures to indoor radon developed by EPA, regulatory authorities in other countries, and national and international advisory organizations are discussed in chapters. This section presents a summary comparison of EPA guidances for indoor radon with those developed by other organizations. Guidances for mitigation of radon in homes are summarized in table 10.1. This summary indicates that EPA's recommended mitigation level lies toward the lower end of the range of values encompassed by the guidances developed by other regulatory and advisory organizations. Some of the reasons for the differences are as follows. All regulatory or advisory organizations that have developed guidance for radon in homes have assumed about the same risk per unit exposure to short- lived radon decay products. As summarized in chapter 8, on the basis of the assumption of a relative-risk model, there are some differences in the risk per unit exposure assumed by various organizations, arising from such factors as differences in the time at which the data were evaluated (that is, differences in the observed number of lung cancers in study populations) and differences in the models for projecting future risks in study populations for people who are still alive. However, those differences are not large, and the differences among the various guidances do not reflect substantial differences of scientific opinion about risks posed by exposure to indoor radon. Rather, the differences among

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COMPARISON OF CURRENT GUIDANCES FOR TENON 207 the guidances result primarily from such factors as differences in average radon levels in homes in various countries, in judgments about maximum tolerable risks posed by exposure to indoor radon or levels of indoor radon that are reasonably achievable with available technologies for mitigating exposures, and in the population groups of concern in establishing the guidances. The differences between EPA guidance for radon in homes and NCRP and ICRP recommendations are of particular interest. As noted above, these differences do not result from substantial differences in assumptions about the risk posed by exposure to indoor radon. NCRP and ICRP recommendations were based primarily on judgments about the maximum tolerable risk or dose to individuals, and the intent was mainly to mitigate exposures of the relatively few individuals who experience the highest risks (ICRP 1993b; NCRP 1984c). NCRP's recommended mitigation level was based on an assumption that lifetime risks of fatal lung cancers greater than 0.02 from exposure to radon in homes should be avoided. NCRP also recommended that levels of indoor radon be reduced below the mitigation level in accordance with the ALARA objective (as low as reasonably achievable). Therefore, actions to reduce levels of indoor radon, once undertaken, should result in radon exposures substantially below the recommended mitigation level. ICRP's recommended mitigation level was based on the assumptions that the annual effective dose from exposure to indoor radon should not exceed about 10 mSv, which corresponds to a lifetime risk of fatal cancers of about 0.04, and that the optimized annual effective dose, based on application of the ALARA objective, should be in the range of about 3-10 mSv, taking into account the various situations in different countries. The EPA guidance also is concerned with protection of individuals who experience the highest exposures to indoor radon. However, the EPA guidance was based for the most part on considerations of average levels of radon in homes and a cost-benefit analysis of reducing these levels with available technologies (EPA and DHHS 1994~; that is, the guidance reflected a greater emphasis on reducing exposures to radon in the greatest number of homes. Thus, the difference between EPA's mitigation level and the values recommended by NCRP and ICRP is explained in part by a difference in emphasis reducing risks to individuals versus reducing risks to whole populations. Many regulatory or advisory organizations also have developed separate guidance on mitigation of indoor radon in above-ground workplaces (excluding workplaces involving operations of the nuclear fuel cycle) and schools. These guidances are summarized in table 10.2. With the notable exception of EPA guidance for radon in schools, the guidances for workplaces or schools usually are substantially higher than the corresponding guidance for

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COMPARISON OF CURRENT GUIDANCES FOR TENORM 209 homes. The increase is based on consideration of the lower residence times in workplaces and schools than in homes. Although EPA recognized the difference in residence times, the guidance for radon in homes was applied to schools primarily on the basis of a judgment that the mitigation level in homes is reasonably achievable in schools, taking into account the existing levels of radon in schools and a cost-benef~t analysis of reducing these levels (EPA and DHHS 1994~. It is also possible, although not yet demonstrated, that children, who are the primary population group of concern in schools, experience substantially higher radon risks than adults. TENORM OTHER THAN INDOOR RADON This section presents a summary comparison of EPA guidances for TENORM other than indoor radon with relevant guidances developed by other federal agencies (the Nuclear Regulatory Commission and the Department of Energy, DOE), state organizations, and advisory organizations (NCRP, HPS, and ICRP). As noted above, this comparison does not consider guidances for naturally occurring radionuclides that apply to operations of the nuclear fuel cycle or the management and disposal of uranium or thorium mill tailings, which are regulated by EPA, the Nuclear Regulatory Commission, and DOE under the Atomic Energy Act. EPA guidances for TENORM other than indoor radon are discussed in chapter 7, and the relevant guidances developed by other organizations are discussed in chapter 9. For consistency with the presentations in chapter7, guidances for TENORM other than indoor radon are divided into two categories: those which apply to multiple sources of exposure combined, including sources other than TENORM, and those which apply only to specific sources or practices involving TENORM. Guidances on Radiation Protection of the Public Applicable to TENORlVi Guidances for TENORM other than indoor radon that apply to multiple sources of exposure combined are summarized in table 10.3. These guidances generally have been developed in the context of radiation-protection standards for the public (see chapter 7~. The following points should be noted in comparing them.

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COMPARISON OF CURRENT GUIDANCES FOR TENORM 211 First, this committee has assumed that the annual dose limit of 1 mSv (100 mrem) in EPA's proposed federal guidance on radiation protection of the public (EPA 1994d), rather than the annual dose limit of 5 mSv (500 mrem) in the existing federal guidance (FRC 1960), represents EPA's current views on the maximum tolerable dose from exposure to all controlled sources combined, even though the proposed revision of the guidance has not been issued in final form. Second, the annual dose limit of 1 mSv (100 mrem) for all controlled sources combined, including TENORM and human-made radionuclides but excluding indoor radon and medical exposures, in EPA's proposed federal guidance on radiation protection of the public (EPA 1994d) is the same as the dose limit for all human-made sources combined recommended by the ICRP (1991) and NCRP (1993a). However, the NCRP and ICRP recommendations do not apply to TENORM and so are not given in table 10.3. Third, the NCRP recommendation in table 10.3 applies only to natural sources (including natural background radiation), TENORM as defined in this study, and presumably uranium and thorium mill tailings, but it does not apply to human-made radionuclides. Therefore, the Federal Radiation Council and EPA guidances in table 10.3 that apply to TENORM other than indoor radon and to human-made radionuclides but not to natural background are not directly comparable with NCRP's recommended remedial-action level for natural sources. However, given that the average annual dose from natural background excluding radon is about 1 mSv (100 mrem) (see table 2.10), NCRP's remedial action level of 5 mSv (500 mrem) normally would allow considerably higher exposures to TENORM than EPA's proposed primary dose limit of 1 mSv (100 mrem). Finally, as emphasized in chapter 7, acceptable radiation protection of the public is not defined solely in terms of compliance with a dose limit from exposure to all controlled sources combined. Rather, a basic principle of radiation protection is that the ALARA objective should be applied in reducing doses below the limit, and the ALARA objective is an integral part of all guidances listed in table 10.3. Guidances for Specific Sources or Practices Involving TENORM: Guidances that apply only to specific sources or practices involving TENORM other than indoor radon are summarized in table 10.4. As discussed in chapter 7, standards for specific sources or practices are an important means of ensuring compliance with radiation-protection standards for all controlled sources combined, including the primary dose limit and the ALARA objective. The guidances summarized in table 10.4 differ from those listed in table 10.3 in

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COMPARISON OF CURRENT GUIDANCES FOR TENORM 213 anti ~ I~ Hi. ~ ~ l

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214 GUIDELINES FOR EXPOSURE TO TENORM that they do not apply to human-made radionuclides or to natural sources other than TENORM. Guidances specifically for TENORM have been developed only by EPA, DOE, and state organizations. However, this committee also considers that the Nuclear Regulatory Commission guidance on natural uranium and thorium in soil and the HPS recommendation on cleanup standards for radium and thorium in soil are relevant to TENORM. In current ICRP (1991) and NCRP (1993a) recommendations, exposures to specific sources or practices involving TENORM other than indoor radon are considered only in the context of guidances on radiation protection of the public, which were considered in the previous section and summarized in table 10.3. The following points should be noted in comparing the guidances in table 10.4. First, as noted in chapters 6 and 7, EPA's current approach to regulating TENORM other than indoor radon is rather fragmentary because no standard or set of standards applies to all potentially important exposure situations. However, in addition to requirements for complying with any applicable regulations including those developed under the Safe Drinking Water Act, Clean Water Act, and Clean Air Act (table 10.4 - this committee has assumed that an annual dose constraint of 0.15 mSv (15 mrem) (Luftig and Weinstock 1997) represents EPA's current views on acceptable exposures to TENORM from any source. Second, it is difficult to compare EPA guidance (Luitig and Weinstock 1997) expressed in terms of dose with standards for radium-226 expressed in terms of activity per unit mass developed by other organizations (see table 10.4), because the dose from exposure to materials containing a given concentration of 226Ra can depend on the volume of the source. For example, for large volumes of contaminated surface soil, the annual dose from external exposure corresponding to the state and Conference of Radiation Control Program Directors (CRCPD) standards for 226Ra expressed in terms of activity concentrations would be about 0.6 mSv (60 mrem) or greater for continuous occupancy (see chapter 7~. Therefore, for large-volume sources, the annual dose constraint of 0.15 mSv (15 mrem) in EPA guidance should be considerably more restrictive than the state or CRCPD standards, with the exception of the standard in New Jersey. However, for much smaller sources, the external dose corresponding to a given concentration of 226Ra could be reduced considerably. For example, at the outer surface of a steel pipe that contains 226Ra contamination at 0.6 Bq/g (15 pCi/g) on the inside wall, Bernhardt and others (1996) estimated that the exposure rate would be about 2 pR/h. If the contamination is assumed to be represented by a line source, for which the dose varies inversely with the distance from the source, and if the outer surface of the pipe is assumed to be about 1 cm from the source, the exposure rate at a nominal distance of 1 m would be 0.02 ,uR/h, and the annual dose equivalent for

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COMPARISON OF CURRENT GUIDANCES FOR TENORM 215 continuous exposure at this distance, taking into account that 1 R is about 7 mSv (0.7 rem) (ICRP 1987a), would only be about 1 pSv (0.1 rurem). Similar comparisons with EPA's dose constraint would apply to the Nuclear Regulatory Commission, DOE, and HPS guidances in the form of activity concentrations. Third, in regard to EPA guidance for cleanup of Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) sites (Luttig and Weinstock 1997), this committee again emphasizes that the annual dose constraint of 0.15 mSv (15 mrem) from exposure to TENORM a/contaminated sites subject to remediation under CERCLA is a goal, rather than a regulatory limit, and the goal may be exceeded if compliance is not feasible. That consideration compounds the difficulties in comparing EPA guidance with the various state standards for cleanup of 226Ra, which are interpreted as regulatory limits. The dose criterion in EPA guidance essentially may be regarded as an upper bound on de minimis (negligible) dose, rather than a limit that must be met for specific sources or practices (see chapter 7~. Fourth, some state regulations for 226Ra include both cleanup standards and exemption levels, and the two usually are essentially the same. Thus, in effect, these regulations specify that acceptable exposures to TENORM other than indoor radon can be no higher than exposures that do not warrant regulatory control. Finally, the proposed Part N of the suggested state regulations (CRCPD 1997) also specifies conditions, not shown in table 10.4, for unrestricted release of facilities and equipment contaminated with TENORM, including limits on surface contamination for alpha and beta or gamma activity and limits on external radiation due to surface contamination. As described in chapter 9, such contamination limits also are specified in DOE requirements for unrestricted release of facilities and equipment contaminated with TENORM (DOE 1990~. However, those criteria, especially the limits on surface contamination, are not clearly related to dose and so are not easily compared with the dose constraint in EPA guidance. Bases For Differences In Guidances The information discussed in the previous two sections and summarized in tables 10.3 and 10.4 indicates that current EPA guidances for TENORM other than indoor radon often are substantially more restrictive than similar guidances developed by other organizations. That is especially the case if one compares EPA's dose limit for all sources combined with NCRP's remedial action level for natural sources (table 10.3) or EPA's preferred dose constraint for individual sources with other guidances in the form of activity concentrations of radionuclides (table 10.4~. However, as in the case of indoor radon discussed previously, all regulatory or advisory organizations that have

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216 GUIDELINES FOR EXPOSURE TO TENORM developed guidances for TENORM other than indoor radon assume essentially the same risk per unit dose from uniform exposure of the whole body on the basis of estimates by expert groups (ICRP 1991; National Research Council 1990~. As discussed in chapter 11, EPA has developed methods of risk assessment for exposure to radionuclides other than radon that differ from the approaches normally used by other organizations, and the differences in estimated risks are particularly important for internal exposure to some naturally occurring radionuclides. However, the differences between EPA guidances for TENORM other than indoor radon, especially the annual dose limit of 1 mSv (100 rurem) for all controlled sources combined and an annual dose constraint of 0.15 mSv (15 rurem) for specific practices or sources, and the guidances developed by other organizations do not result from differences in methods of risk assessment for radionuclides. That is, EPA's approach to risk assessment, as it differs from the approach normally used by other organizations, was not an important factor in developing the current EPA guidances. Thus, the differences between EPA guidances for TENORM other than indoor radon and the guidances developed by other organizations are not based on the differences of opinion about risks posed by exposure to TENORM. Rather, the differences between the guidances result in part from differences in judgments about acceptable risks from exposure to TENORM and differences in judgments about levels of TENORM in the environment that are reasonably achievable (see chapter 5~. In addition, the guidances for TENORM in the form of concentration limits for radium and thorium in contaminated soil and other materials often were based primarily on existing EPA standards in 40 CFR Part 192 for cleanup of contaminated soil at uranium or thorium mill tailings sites (see chapter 9~. SUMMARY This chapter has presented summary comparisons of guidances for controlling exposures of the public to TENORM developed by EPA with similar guidances developed by other organizations, including the Nuclear Regulatory Commission, DOE, state organizations, other countries, NCRP, HPS, ICRP, and IAEA. Guidances for indoor radon have been considered separately from guidances for TENORM other than indoor radon. EPA's current mitigation level for indoor radon is somewhat lower than the values developed in most other countries or recommended by NCRP and ICRP. However, the differences in the guidances do not result from substantial differences of scientific opinion about the risks posed by exposure to indoor radon. Rather, they result primarily from such factors as differences in average

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COMPARISON OF CURRENT GUIDANCES FOR TENORM 217 radon levels in homes, differences in judgments about maximum tolerable risks to individuals or levels of radon that are reasonably achievable after mitigation, and differences in whether a guidance focuses primarily on reduction of risks to individuals receiving the highest exposures or on reduction of risks in the whole population. In many cases, the current EPA guidances for TENORM other than indoor radon also appear to be more restrictive than the relevant guidances developed by state organizations, other federal agencies, NCRP, and HPS. However, direct comparisons of the various guidances are difficult and potentially misleading because of differences in whether exposures to natural background are included, the difference in concept between a regulatory goal and a limit, and the use of dose criteria in some guidances and activity concentrations of radionuclides in others. The differences between guidances do not reflect the differences in approaches to risk assessment for radionuclides used by EPA and other organizations. Rather, the differences in the guidances for TENORM other than indoor radon result primarily from differences in judgments about acceptable risk, differences in judgments about risks that are reasonably achievable, and judgments about the transferability of standards from one exposure situation to another. An additional consideration of importance in comparing the guidances for TENORM summarized in this chapter is that the specified quantitative criteria usually are not the most important factor in determining doses and risks that would be experienced in any exposure situation. Rather, as discussed in chapter 7, actual doses and risks usually are determined primarily by application of the ALARA objective, largely without regard for any limits or goals for exposure to TENORM that might be specified in guidances.