Caveats about Countermeasures for
Treatment of Internal Radiation Contamination

• Information Sources
• General Caveats
• Clinical Issues
• Conceptual Issues
• References

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Information Sources

• REMM Radiation Countermeasures for Treatment of Internal Contamination table is derived from three primary sources
  • For approved medical countermeasures
    • US Food and Drug Administration (FDA)
  • For non-FDA approved medical countermeasures
    • Management of Persons Contaminated with Radionuclides: Handbook (NCRP Report No. 161, Vol. I), National Council on Radiation Protection and Measurements, Bethesda, MD, 2008.
    • Population Monitoring and Radionuclide Decorporation Following a Radiological or Nuclear Incident (NCRP Report No. 166), National Council on Radiation Protection and Measurements, Bethesda, MD, 2011.
• Additional advice on the management of internal contamination may be obtained from
  • Radiation Emergency Assistance Center/Training Site (REAC/TS) at 865-576-1005 or orise.orau.gov/reacts/index.html
  • Armed Forces Radiobiology Research Institute (AFRRI)
  • US Food and Drug Administration
  • Centers for Disease Control and Prevention

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General Caveats

• This table is intended as a guide to the selection of medical therapy, and does not represent official policy of HHS.
• Most of the medical countermeasures listed in this table have not been approved by the US Food and Drug Administration (FDA) for the listed use.
• For FDA-approved drugs, consult the official package insert for detailed prescribing information.
• For details concerning the use of non-FDA approved drugs, consult the NCRP 161 reference cited above. This table presents summary data included in that monograph.
• Off-label use of medical countermeasures or use of non-FDA approved drugs to treat internal contamination carries an unknown risk-benefit ratio and warrants extreme caution.
• Except as indicated in the official package insert, there is very little information about using these medical countermeasures in infants and children.
• Decisions to use medical countermeasures to treat internal contamination should be made in conjunction with medical radiation or medical toxicology experts.

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Clinical Issues

• Treatment of internal contamination
  • Is based on the radionuclide(s) involved (see tables)
  • Should occur in consultation with a professional who is knowledgeable about treating radiological injuries such as a hospital Radiation Safety Officer, nuclear medicine physician, radiation oncologist, and/or a toxicologist
• Therapeutic objectives
  • Decrease radiation absorbed dose
  • Reduce the risk of future biological effects.
• Many of the countermeasures listed in the table on REMM have an unfavorable risk-to-benefit ratio when used to treat persons having low levels of internal contamination.
• Most authorities do not recommend treatment of internal contamination when the body burden is less than one annual limit of intake (ALI)⁸.
• Treatment is strongly recommended when the body burden exceeds 10 ALI.
• For internal contamination levels greater than 1 ALI and less than 10 ALI, clinical judgment dictates treatment of internal contamination.

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Conceptual Issues

• Annual Limit of Intake (ALI)
  • According to NCRP, ALI is an operational quantity defined originally by ICRP as the level of intake of radionuclide activity that would irradiate a person to the annual limit set by the ICRP for occupational (workplace) exposure⁷.
  • Per NCRP, this number is usually considered to be 0.05 sievert (5 rem) effective dose and 0.5 sievert (50 rem) equivalent dose to any exposed tissue. This equivalent dose is thought to be not only below the threshold at which deterministic health effects occur but also low enough to limit the incidence of stochastic health effects.
  • The ALI concept assumes continuous low level uptake, as could happen with an occupational exposure. The ALI concept was developed to protect workers, not members of the general public.
  • ALI was never intended for use as a measure of intake for persons internally contaminated as a result of radiological or nuclear incidents and certainly not for members of the public during events such as accidents or terrorist incidents, when intake might occur over a very short period of time.
  • Nevertheless, the ALI concept has been used by some clinicians when considering when to initiate countermeasures for individual members of the public who have been internally contaminated with radioactive materials as a result of a terrorist incident or unintentional event (e.g., transportation accident).
• Clinical Decision Guide (CDG)
  • NCRP has updated its guidance on the management of persons internally contaminated with radionuclides.^{1, 2, 3} This update supersedes previously published guidance from NCRP⁵ and introduces a new operational quantity - the Clinical Decision Guide (CDG) - to replace the ALI as a decision-making tool. CDG values represent thresholds for initiating treatment with medical countermeasures and take into account both the acute (deterministic) and chronic (stochastic) effects of internalized radionuclides. CDGs for children (0-18 years) and pregnant women are defined as one-fifth the derived adult value.
  • See NCRP Report No. 161 and NCRP Report No. 166 for details about using CDG values for internal contamination with specific radionuclides.
  • Wiley AL Jr. Use of Clinical Decision Guidance as a New Public Health Tool for the Medical Management of Internal Contamination in Radiological Mass Casualty Scenarios. Radiat Prot Dosimetry. 2016 Sep;171(1):124-8. [PubMed Citation]
  • Alves Dos Reis A, Ha WH, Kukhta B, Li C. Monitoring and Dose Assessment for Children Following a Radiation Emergency Part I: Reference Values for In Vitro Bioassay. Health Phys. 2017 Mar;112(3):282-293. [PubMed Citation]
• Early Internal and External Dose Magnitude Estimation (REAC/TS, 07/2017)
  • Focuses on external and internal contamination and compares ALI and CDG.
  • Describes methods for rapidly estimating internal and external radiation dose magnitudes that can be used to help guide early medical management.
  • Includes quick reference tables and examples of how to apply the mathematical formulas.
• Help understanding ALI, effective dose, committed dose, and regulations
  • NRC definition of ALI
  • Nucleonika wiki definition of ALI
  • REMM definition of "effective dose"
  • Wikipedia definition of "committed dose"
  • REAC/TS ORISE glossary
  • NRC glossary
  • EPA: Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion, Federal Guidance Report No. 11, September, 1988
  • NRC: Standards for Protection Against Radiation
  • Regulations for Worker Protection from US Government Agencies (external exposure and internal contamination)

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References

NCRP

1. Population Monitoring and Radionuclide Decorporation Following a Radiological or Nuclear Incident, (NCRP Report No. 166), National Council on Radiation Protection and Measurements, Bethesda, MD, 2011.
2. Management of Persons Contaminated with Radionuclides: Handbook (NCRP Report No. 161, Vol. I), National Council on Radiation Protection and Measurements, Bethesda, MD, 2008.
3. Management of Persons Contaminated with Radionuclides: Scientific and Technical Bases (NCRP Report No. 161, Vol. II), National Council on Radiation Protection and Measurements, Bethesda, MD, 2010.
4. Management of Terrorist Events Involving Radioactive Material (NCRP Report No. 138), National Council on Radiation Protection and Measurements, Bethesda, MD, 2001.
5. Management of Persons Accidentally Contaminated with Radionuclides (NCRP Report No. 65), National Council on Radiation Protection and Measurements, Bethesda, MD, 1980.

ICRP

6. Protecting people against radiation exposure in the event of a radiological attack. (ICRP Publication 96), International Commission on Radiological Protection, 2005.
7. Limits for Intakes of Radionuclides by Workers (ICRP Publication 30), International Commission on Radiological Protection. (Note: ICRP Publication 30 includes 10 separate documents published between 1979 and 1988. All are listed on ICRP Publications, but online access may be limited to libraries with electronic subscriptions.)

Other

8. Dose assessment of inhaled radionuclides in emergency situations (Public Health England [PHE], formerly Health Protection Agency [HPA]/United Kingdom and Treatment Initiatives After Radiological Accidents (TIARA) project/European Commission, August 2007)

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