Target Levels for
Radiation Decontamination of People
- Contamination is not the Same as Exposure
- What Factors May Affect the "Target Level Selected For Decontamination"?
- Nomenclature is Important in Understanding the Issues
- Key Guidance Documents Recommend Different "Target Levels for Decontamination" of People
- Selected List of Key Guidance Documents About "Target Levels for Decontamination" of People
Contamination is not the Same as Exposure
- What is external contamination?
- This page is about external contamination only.
- What is internal contamination?
- What is exposure?
What Factors May Affect the "Target Level Selected for Decontamination"?
- Nature and location of the incident
- Where and when the survey is conducted
- Number of people who need to be surveyed vs. number of people available and qualified to do radiation surveys
- Number of working, calibrated survey meters
- Type of radiation detected by the survey meters available (alpha, beta, gamma) and settings (sensitivity) of the survey equipment
- Type of contamination (alpha, beta, gamma) that needs to be surveyed and the radioisotope identified.
- Pattern of contamination identified (e.g., loose, fixed, both; generalized/widespread vs. "spot" contamination)
Nomenclature is Important in Understanding the Issues
- Decontamination avoids potential health effects
- Deterministic effects - dose threshold exists below which effect does not occur
- Earliest effects - erythema, acute exudative radiodermatitis, the latter being most important
- Intermediate/later effects - skin ulceration from a hot particle, skin ulcer with fibrosis
- Stochastic effects - no threshold dose exists below which the effect will definitely not occur and the probability of occurrence is directly (but not necessarily linearly) proportional to the dose received
- Long term effects - skin cancer, many other cancers
- What is a screening level?
- A rapid assessment level, where action is warranted to prevent adverse effects and then quickly separate people that need more immediate decontamination
- Often performed before decontamination and is meant for high throughput of personnel
- What is monitoring level?
- A more deliberate monitoring level, often post initial decontamination, or when the number of victims to be surveyed is small.
- This monitoring is performed to look for lower levels of contamination, often taking much longer to perform.
- See REMM information on: How to Perform a Survey
- What a radiation survey meter reads, i.e., how many (what percent) of the disintegrations have been detected by the meter.
- Instrument-specific conversion factors (measuring counting efficiency) correlate CPM detected by the meter to DPM, and/or to other values used for radiation protection e.g., exposure rate in air (roentgen), absorbed dose rate in people (gray, sievert).
- Loose contamination
- Easily dislodged; removable by brushing off, washing or changing clothes.
- Fixed contamination
- "Stuck" onto the skin surface (or hair) so that neither brushing nor washing dislodges the radioactivity.
- Normal skin growth and skin sloughing typically removes fixed skin contamination in about 2 weeks.
Key Guidance Documents Recommend Different "Target Levels for Decontamination" of People
- Various US and international agencies have recommended "target levels for radiation decontamination" of people during incidents of various kinds, sizes, and venues.
- See table below showing decontamination targets published by various professional groups and government agencies
Documentation β/γ Screening Criteria Contamination Radionuclide Skin-to-Detector Separation Contamination Extent Exposure Time FEMA-REP-22 1,000 cpm fixed/ 10,000 cpm loose above bkg Cs-137/Ba-137m 2.54 cm 0.2 cm2 spot with widespread 14 days fixed/36 hours loose CRCPD Handbook 10,000 cpm above bkg Cs-137/Ba-137m 2.54 cm Widespread Not specified EPA 2017 PAG Manual 2x bkg Not specified Not specified Not specified 12 hours IAEA Operational Interventional Levels (OILs) for Reactor Emergencies β: 1,000 cps
γ: 1 Sv/h
Light Water Reactor emergency mix β 2 cm
γ: 10 cm
Not specified Not specified NCRP Report No. 161 10,000 Bq/cm2
Sr-90 1 cm 0.2 cm2 spot with widespread Not specified NCRP Report No. 165 600,000 dpm/cm2 Sr-90 1 cm Not specified Not specified
NCRP Report No. 166 1,000 cpm Sr-90 1 cm Not specified 24 hours
Source of table above: Caleigh Samuels, "Review of Current External Radiation Contamination Criteria" from presentation March 2019 to NCRP PAC 3 Committee. Presentation entitled: "Monte Carlo simulations evaluating suggested external contamination screening criteria for radiological and nuclear emergencies".
- Recommendations differ, producing confusion about what to do. (See Selected References List below.)
- REMM attempts to highlight the issues and provide context for understanding the problem.
- Readers are encouraged to consult the original documents in the Selected References List below to learn about the issues in detail.
- Professional responders using radiation survey meters should understand the significance of "meter readings" and "target values" for decontamination as they relate to
- Type of radiation being detected (alpha, beta, gamma)
- Specific kinds of meters and
- Sensitivity (efficiency) of the meter
- Parameters of the survey: probe speed, distance from probe to contamination, and path width for detecting "spot" decontamination
- Probe type (e.g., "pancake", "hot-dog"); window-type (e.g., side or end reading); window thickness; area (cm2) of probe; whether or not probe covers were used
- See pictures of various survey meters and probes at the last few pages of this document (PDF - 829 KB).
- Whether the focus of the survey of an individual is "spot" or "widespread" contamination
- Whether the survey is addressing is "fixed" or "loose-plus fixed" contamination
- How the survey instrument responds when it is stationary over a "hot spot" vs. following a continuous path over whole body survey
- Particulars of the incident
- Size of the incident and number of patients who need attention vs. the size of the decon team available with working equipment
- Whether the site doing decon is performing "initial surveillance" triage decon for a large number of people or later-stage monitoring decon for people who have had previous decon elsewhere
- Recommendations in the Selected Reference List of guidance documents below will help parse the issues noted above.
- In a large incident, senior leaders, consulting with radiation protection specialists, will recommend clear and specific "targets for decontamination levels" for specific venues and circumstances, and these may change over time if circumstances change during the incident.
- Understand that in some very large incidents, especially in cold weather, incident managers may recommend that large numbers of potentially contaminated patients get indoors, change clothes and/or shower first either at home or designated areas before undergoing formal surveys with a radiation detection meter and additional decontamination, if necessary.
- Understand that recommendations for "target levels for decontamination" of people are NOT the same as those for vehicles, equipment, possessions, buildings, ground during the early or Recovery Phase of an incident.
- NCRP is expected to publish in 2014 a document on the Recovery Phase of an incident which addresses this issue.
Selected List of Key Guidance Documents about
"Target Levels for Decontamination" of People
- Population Monitoring in Radiation Emergencies: A Guide for State and Local Public Health Planners, April 2014.
- In the 2014 guide, see especially: Appendix D: Radiological Screening Criteria - External Contamination.
- This guidance updates the previous Draft Guidance from 2007.
- Geiger-Muller Radiation Detectors Job Aid (PDF - 430 KB) (HHS/CDC)
- Guidance for Traveler Screening at Ports of Entry Following an International Radiological Incident (PDF - 1.69 MB) (CDC/NARR)
- Federal Emergency Management Agency, Contamination Monitoring Standard for a Portal Monitor Used for Radiological Emergency Response, FEMA-REP-21, (PDF - 62 KB) (FEMA, March 1995)
- Federal Emergency Management Agency, Contamination Monitoring Guidance for Portable Instruments Used for Radiological Emergency Response to Nuclear Power Plant Accidents, FEMA-REP-22, (PDF - 233 KB) (FEMA, October 2002)
- Minimal detectable concentrations with typical radiation survey instruments for various contaminants and field conditions. (PDF - 7.47 MB) (NUREG-1507, June 1998)
- Decision Making for Late-Phase Recovery from Major Nuclear or Radiological Incidents, (NCRP Report No. 175), National Council on Radiation Protection and Measurements, Bethesda, MD, 2014.
- Population Monitoring and Radionuclide Decorporation Following a Radiological or Nuclear Incident, (NCRP Report No. 166), Bethesda, MD, 2011.
- Responding to a Radiological or Nuclear Terrorism Incident: A Guide for Decision Makers (PDF - 1.61 MB) (NCRP Report No. 165), Bethesda, MD, 2010.
- Management of Persons Contaminated with Radionuclides: Scientific and Technical Bases (NCRP Report No. 161, Vol. II), Bethesda, MD, 2010. Chapter 5: Performing Surveys and Controlling Personnel and Area Contamination.
- Management of Persons Contaminated With Radionuclides: Handbook (NCRP Report No. 161, Vol. I), Bethesda, MD, 2008.
- Key elements of preparing emergency responders for nuclear and radiological terrorism (NCRP Commentary No. 19), Bethesda, MD, December 2005. Purchase required.
- PAG Manual: Protective Action Guides and Planning Guidance for Radiological Incidents, EPA-400/R-17/001 (PDF - 1.48 MB) (EPA, January 2017)
- Handbook for responding to a radiological dispersal device first responder's guide - the first 12 hours (Conference of Radiation Control Program Directors, Inc., September 2006) (Decontamination Guidelines, pages 35-38)
- Criteria for use in preparedness and response for a nuclear or radiological emergency, General Safety Guide, No. GSG-2, (PDF - 1.45 MB) (FAO, IAEA, ILO, PAHO, WHO, March 2011)
- Manual for First Responders to a Radiological Emergency (PDF - 2.2 MB) (CTIF, IAEA, PAHO, WHO, October 2006)
- Generic Procedures for Medical Response During a Nuclear or Radiological Emergency (PDF - 2,224 KB) (IAEA, WHO, July 2005)
- Koenig KL, Goans RE, Hatchett RJ, Mettler FA Jr, Schumacher TA, Noji EK, Jarrett DG. Medical treatment of radiological casualties: current concepts. Ann Emerg Med. 2005 Jun;45(6):643-52 [PubMed Citation]