Paper A NOVEL METHOD FOR QUICK

Paper A NOVEL METHOD FOR QUICK ASSESSMENT OF INTERNAL AND EXTERNAL RADIATION EXPOSURE IN THE AFTERMATH OF A LARGE RADIOLOGICAL INCIDENT Downloaded from https://journals.lww.com/health-physics by BhDMf5ePHKav1zEoum1tQfN4a+kJLhEZgbsIHo4XMi0hCywCX1AWnYQp/IlQrHD33D9/FQ5Fz8mGgcaSLhFGKJ3JwYrILbsqH9Nm79NcXsI= on 07/20/2018

Geoffrey Korir1 and P. Andrew Karam2

Abstract—In the event of a significant radiological release in a major urban area where a large number of people reside, it is inevitable that radiological screening and dose assessment must be conducted. Lives may be saved if an emergency response plan and radiological screening method are established for use in such cases. Thousands to tens of thousands of people might present themselves with some levels of external contamination and/or the potential for internal contamination. Each of these individuals will require varying degrees of radiological screening, and those with a high likelihood of internal and/or external contamination will require radiological assessment to determine the need for medical attention and decontamination. This sort of radiological assessment typically requires skilled health physicists, but there are insufficient numbers of health physicists in any city to perform this function for large populations, especially since many (e.g., those at medical facilities) are likely to be engaged at their designated institutions. The aim of this paper is therefore to develop and describe the technical basis for a novel, scoring-based methodology that can be used by non-health physicists for performing radiological assessment during such radiological events. Health Phys. 115(2):235–251; 2018 Key words: contamination; dose assessment; emergencies; radiological; emergency planning

INTRODUCTION IN THE event of a large-scale radiological or nuclear incident, adequate resources and know-how will almost undoubtedly be scarce. There will be time-constraint issues as well as a shortage of professional health physicists to perform radiological assessments and to recommend decorporation 1 Radsafe Technologies Ltd., P.O. Box 28826, Nairobi, Kenya; 2Karam Consulting, LLC, 530 82nd St., Apt. 2F, Brooklyn, NY 11209. The authors declare no conflicts of interest. For correspondence contact: P. Andrew Karam, 530 82nd St, Apt. 2F, Brooklyn, NY 11209, or email at [email protected]. (Manuscript accepted 28 November 2017) 0017-9078/18/0 Copyright © 2018 Health Physics Society

DOI: 10.1097/HP.0000000000000858

agents where applicable. Therefore, it will be vitally important to quickly determine who received radiation doses of clinical significance, either from a high uptake of radioactive material or through external radiation exposure. The procedure described herein is designed to be robust and reliable for those who report exposure immediately, unlike those who report days later after undergoing self-decontamination. The group will have a clear memory of the circumstances under which they were exposed. This method is meant to be flexible enough to accommodate those exposed to gamma-emitting radionuclides, which can be measured outside the body, as well as those exposed to alpha, beta, and low-energy gamma-emitting radionuclides that do not penetrate the skin. Obviously, the results will be more accurate with reliable information; at the same time, conservative assumptions are made to allow for inaccurate data, and as such the proposed dose assessment is much more likely to be an overestimate than an underestimate. Radionuclides that become incorporated into the body might remain for long periods of time (americium, for example, will remain in the body for a lifetime) and can deliver a high dose of radiation to the person affected. Accordingly, it is important to quickly determine whether or not an uptake has occurred and, if so, if it might be clinically significant. National Council on Radiation Protection and Measurements (NCRP) Report 161 defined the clinical decision guide (CDG) as being the “maximum, once-in-a-lifetime intake of a radionuclide that represents a stochastic risk, as judged by the calculated effective dose over 50 y for intake by adults and up to age 70 y for intake by children, that is in the range of risks associated with guidance on dose limits for emergency situations (DOE 2008; FEMA 2008; ICRP 1991; NCRP 1993, 2005, 2008), and avoidance of deterministic effects as judged by the calculated 30‐day RBE-weighted absorbed doses to red marrow and lungs, with allowance for the significant uncertainties often involved in an initial evaluation of the chemical and physical form of a radionuclide and the level of activity taken into the body during an incident.” This exposure level will serve as the basis for 235

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concluding that a person’s radiation exposure will require consideration in formulating a short-term treatment plan and decorporation therapy. The lowest radiation exposure that has a degree of clinical significance is 0.25 Sv (25 rem),3 which is recognized in the development of the CDG in NCRP Report 161, Management of Persons Contaminated with Radioactivity (NCRP 2008). METHODOLOGY General Under this system, both quantitative and qualitative data will be assessed and will be scored according to a methodology that will be described in detail in the following sections. Scoring systems are commonly used in medical practice: from birth when newborns are scored using the Apgar system (Apgar 1953) through adulthood when scores from well-known and long-running studies are used (Framingham Risk Score), when the Glasgow Coma Score is used for patients who fall into a coma (Teasdale and Jennett 1974), and when the Eagle Score is used to estimate the risk of a patient dying during heart surgery (L’Italien et al. 1996). Scoring systems are accepted in medicine to help physicians quickly and discerningly make consistent clinical decisions; it is equally appropriate to use a scoring system for radiation dose assessment for the very same reasons. This scoring system will be used to quickly determine whether a person has received so little exposure to radiation that medical treatment is clearly unnecessary, so much exposure that medical treatment is clearly needed, or an intermediate (or indeterminate) exposure that requires additional assessment via in vitro bioassay, whole-body counting, or some other applicable techniques. If the number of contaminated persons is relatively small, or if the decorporation agent is present in large quantities, the decision could be made to presumptively treat even those people with intermediate levels of radioactive material uptake with decorporation agents. Some factors will result in the assumption that a person requires presumptive decorporation therapy. These include contaminated wounds and the presence of injected radioactive material (i.e., embedded radioactive fragments). Please note that, in this section, scoring values (points) are assigned in each category to be discussed. The derivation and justification of these point assignment suggestions for internal contamination is presented in the Discussion section of this study. Assessment and scoring of qualitative factors for internal radiation exposure Internal radiation exposure is a function of the amount of radioactive material ingested, inhaled, absorbed through 3

NCRP Report 161 uses traditional units of rem, which are provided in parentheses.

August 2018, Volume 115, Number 2

skin and open wounds, or injected through the skin and into the body. These are the first-order factors that can be measured or estimated relatively quickly, and the information can be used to develop a first approximation of the amount of uptake and subsequent radiation exposure. There are additional factors to consider (as discussed, e.g., in EPA 1988), including particle size, solubility, chemical form, the biokinetics of the element(s) in question, and route of intake, among others. For the purposes of this study, these were considered to be second-order factors that cannot be as easily estimated and will not be taken into consideration. This study proposes an approach that will use both quantitative and qualitative data to help determine the amount of radioactive material uptake into the body. Qualitative information from those being evaluated includes factors such as external injuries observed, proximity to explosion, presence of dust or debris on skin and clothing, and descriptions of sensory information (e.g., what they smelled, saw, felt, etc.). The assessment of these factors will be scored so as to assess the possibility of internal radiation exposure. • Injuries: 0 points if there are no injuries, 1 point for light injuries with no contaminated wounds, 2 points for moderate injuries with no contaminated wounds, and 3 points for serious injuries with no contaminated wounds. Automatic referral for decorporation is recommended if there are any contaminated wounds or if there are any embedded radioactive fragments. • Location with respect to proximity to the site of the release: 0 points for long distance from point of release (e.g., the release took place several kilometers downwind of the person’s location), 1 point for distances greater than 2 km downwind or greater than 500 m laterally, 2 points for distances greater than 250 m and less than 500 m in any direction, and 3 points for distances closer than 250 m in any direction. • Dust or debris on skin and clothing: 1 point for light intermittent dust on skin and clothing, 2 points for light dust over the majority of the body, and 3 points for moderate to heavy dust on the majority of the body or solid debris on clothing, in hair, or stuck to skin. • Smell or taste of dust or smoke from the explosion: 1 point if the person vaguely smelled or tasted smoke or dust, 2 points for persistent smell or taste of dust or smoke during and after evacuation, and 3 points for heavy smell of dust or smoke sufficient to cause coughing or choking. The last two factors do not have a 0‐point option because trace contamination might not make an impression or an individual might not have noticed it due to other factors. A consolidated flow chart for evaluating internal qualitative and quantitative exposure factors is presented in Fig. 1.



Quick assessment of internal and external radiation exposure c G. KORIR AND P.A. KARAM

Assessment and scoring of quantitative factors for internal radiation exposure Quantitative data includes measurements of contamination levels on the outside of the body (assessed by measuring skin contamination and contamination around the mouth and nose) as well as inferences about internal

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contamination based on count rates from radioactive material in the lungs as measured on the chest or back. • Facial contamination is the amount of contamination measured near the nose and mouth using a pancaketype Geiger-Mueller (GM)4 detector and will be scored as follows: > 50,000 cpm will receive a score of 4 points; 5,000–50,000 cpm will receive a score of 3 points; 2 points will be awarded for 500–5,000 cpm; and those with < 500 cpm will receive 1 point. Decontamination, assessment of skin contamination levels, and lung counting will follow for those with more than 500 cpm of skin contamination if resources permit. For alpha-emitting radionuclides these values should be reduced by a factor of 10, and lung counting will not be performed. • Skin contamination is based on the highest amount of contamination measured on the skin using a pancaketype GM and will be scored as follows: 4 points will be scored for those with > 100,000 cpm; contamination between 10,000–100,000 cpm will receive 3 points; count rates of 1,000–10,000 cpm will be given a score of 2 points; and < 1,000 cpm will receive a score of 1 point. As noted in the previous bullet, decontamination and lung counts will follow for anyone with more than 1,000 cpm if resources permit. For alpha-emitting radionuclides these values should be reduced by a factor of 10, and lung counting will not be performed. Measurement and scoring of chest or abdomen counts In vivo bioassay measurements are performed in the form of chest or abdomen anteroposterior (AP) or posterior-anterior (PA) position counting of gamma radiation of sufficient energy to penetrate the body. It is noted that the count rates for a given level of internal contamination are similar for AP and for PA measurements; at the same time, it is also noted that modesty and/or cultural factors might restrict the ability of screeners to easily obtain AP (chest) measurements. Accordingly, the count rates noted below reflect the lower of the values provided in Bolch et al. (2012), so that it does not matter whether measurements are obtained on contact with the chest or the back and are referred to as “lung counts.” The measured lung count rate will produce the last of the quantitative measurements to be used for this initial scoring process. Urine sample collection can be taken as part of this process; however, measuring and interpreting the samples will be performed at a national accredited facility and not in the setting anticipated in the procedure applied here [e.g., a high-throughput community reception center (CRC)]. 4

Fig. 1. Flow chart for evaluating internal qualitative and quantitative exposure factors.

The values in this paper assume that the instrument being used is a pancake-type GM. Use of a different instrument such as a sodium iodide detector will require adjusting these values to reflect the appropriate counting efficiency and using the appropriate data from Bolch et al. (2012).



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Bolch et al. (2012) calculated the count rate representing an uptake of 1 CDG using common handheld radiation survey instruments, which were used to develop the graphs for dose estimation in a CRC or at the hospital shortly after a radiological event. These are shown in Fig. 2a–l.


A large number of radionuclides are in common use for medical, research, and industrial purposes. Many of these radionuclides are relatively short-lived or are typically used in small quantities; the great majority of these are very uncommon, pose little threat to the health and safety of

Fig. 2. (a) Abdomen/chest AP/PA counts from 60Co inhalation. (b) Abdomen/chest AP/PA counts from 60Co inhalation. (c) Abdomen/chest AP/PA counts from 60Co inhalation. (d) Abdomen/chest AP/PA counts from 60Co inhalation. (e) Abdomen/chest AP/PA counts from 137Cs inhalation. (f) Abdomen/chest AP/PA counts from 137C inhalation. (g) Abdomen/chest AP/PA counts from 137C inhalation. (h) Abdomen/chest AP/PA counts from 137C inhalation. (i) Abdomen/chest AP/PA counts from 192Ir inhalation. (j) Abdomen/chest AP/PA counts from 192Ir inhalation. (k) Abdomen/chest AP/PA counts from 192Ir inhalation. (l) Abdomen/chest AP/PA counts from 192Ir inhalation. www.health-physics.com



those exposed, have fairly short half-lives, and/or tend to be used in activities that are too low to cause widespread contamination. For this reason, the majority of radionuclides in common use are not considered to pose a significant threat for use in a terrorist attack. In 2003, the International Atomic Energy Agency (IAEA) developed a list of radionuclides that could potentially be present in sufficiently high quantities to be considered dangerous, summarizing them in Table I.2 of IAEA-TECDOC-1344 (IAEA 2003). This was published after the terrorist attacks on 11 September 2001 and after the arrest of the purported “dirty bomber” in 2002, and the nuclides listed in this report were adopted by the U.S. Nuclear Regulatory Commission (NRC) and incorporated into Table 1 of 10 CFR 37 (NRC 2013). Characteristics that are thought to make a radionuclide a potential threat for use in a terrorist attack include: • Half-life sufficiently long to require remediation rather than waiting for decay. • Sources of sufficiently high activity to pose a health risk and/or to permit contamination of large areas. • Sources in relatively common use so that they are relatively easy to obtain legally or illicitly. Of the radionuclides listed in Table 1 of 10 CFR 37 (category 1 and category 2 threshold), there are three gammaemitting radionuclides (60Co, 137Cs, and 192Ir) that are considered likely candidates for use in a radiological dispersal device (RDD) and that can be detected within the body using a pancake GM detector if there are significant count rates (137Cs is also released during nuclear reactor accidents). The lung counting results can be used to approximate radiation exposure (committed effective dose equivalent, CEDE), and the scoring points are as follows:

Table 1. CDG values for selected radionuclides.a Adults Nuclide 60

Co

137

Cs

192

Ir

241

Am

a

Children and pregnant women

Intake

Form

CDG (MBq)

CDG (mCi)

CDG (MBq)

CDG (mCi)

Inhalation Inhalation Inhalation Ingestion Inhalation Inhalation Inhalation

Type M Type S Type F Soluble Type M Type S Type M

35 15 58 28 59 50 9.3 kBq

950 400 1600 760 1600 1400 0.25

7 3 11.6 5.6 11.8 10 1.9

190 80 320 152 320 280 0.05

Type F materials: Deposited materials that have a fast rate of absorption into blood. Type M materials: Deposited materials that have a moderate rate of absorption into blood. Type S materials: Deposited materials that have a slow rate of absorption into blood.

• • • •

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1 point for < 0.2 CDG or 50 mSv. 5 points for 0.2–1 CDG or 50–250 mSv. 15 points for 1–2 CDG or 250–500 mSv. 25 points for > 2 CDG or 500 mSv.

In addition, please note that the counting technique and scoring mentioned here can be adapted for use with other radiation detectors [e.g., NaI(Tl) ], with other radionuclides (e.g., 131I or 241Am), and/or for counting other parts of the body (e.g., thyroid or abdomen). Please note that the point values assigned are not intended to reflect the likely radiation exposure received, as the measurement methodology is too imprecise to be used for this purpose. Rather, the points assigned are intended to reflect the likelihood that the person exposed might have received enough exposure to warrant administration of decorporation agents that might be in short supply, as well as to help medical caregivers prioritize treatment for radiation exposure. For the point assignments provided above, for example, 15 points or more are assigned for a count rate that reflects an intake of 1 CDG and higher; in the Discussion section it is noted that a score of 15 points and higher calls for administration of decorporation agents. Thus, a lung count resulting in 15 points is sufficient to call for decorporation in and of itself. For persons with lower counts, decorporation will still be recommended if other qualitative and quantitative factors (e.g., contamination levels, proximity to event, etc.) are consistent with the lung counts. This helps to reduce the possibility that a spurious lung count (from, for example, a nearby contaminated person or a momentary fluctuation in background count rate) could cause a person to be erroneously administered possibly scarce decorporation agents. Neither alpha- nor beta-emitting radionuclides can be detected via chest scan because of the radiation’s inability to penetrate the wall of the chest or abdomen. Some alpha and beta emitters also emit gamma radiation, which might be externally detectable (although low-energy gamma emitters such as 241Am are likely too weak to penetrate easily and be reliably detected with a pancake GM). For the purposes of this study and because it may not be possible to perform a chest count for low-energy internal alpha or beta emitters, the scoring for these radionuclides will be determined by adjusting the scores from external contamination and qualitative assessment. Table 1 summarizes the CDG values from NCRP Report 161 for selected radionuclides (NCRP 2008). From the data presented one can derive the lung counts that will result from quantitative measurements on which this procedure is based. Bolch et al. (2012) calculated the count rate representing an uptake of 1 CDG using common handheld radiation survey instruments. These CDG values can



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be used for preliminary dose assessment shortly after a radiological event in a CRC or at the hospital.


• Persons with no injuries will be assigned a score of 0 points.

DISCUSSION Derivation of internal dose scores from qualitative factors In addition to quantitative factors, there are qualitative indicators of possible (or probable) internal exposure that can be used in conjunction with (and in support of ) the quantitative factors discussed above. It is acknowledged that qualitative information by its nature could be prone to systematic errors. However, it is proposed that even unreliable information is information and is preferable to having no information at all. In some cases (e.g., a person who went home to change clothing and self-decontaminate and who was exposed to only alpha- or beta-emitting radionuclides), qualitative information may be the only information available. In such cases, rapid dose assessment of any sort will be impossible in the absence of qualitative information such as that described in the study. Presence of injuries from shrapnel and/or flying debris Persons close enough to the explosion to be injured are likely also close enough potentially to have inhaled or ingested contaminated dust or debris. Injection (via embedded fragments) and/or absorption into open wounds are also possibilities for persons sufficiently close to the scene of an explosion. The risk of internal radioactive contamination is greatest for those close enough to have been injured. • Persons with embedded radioactive fragments or with contaminated wounds will be assumed to require decorporation therapy because, in these cases, it is known that radioactive material is (or has been) in direct contact with blood, and it is assumed that an uptake has occurred. In addition, those with contaminated injuries or embedded fragments are injured and will be receiving medical care, so it is reasonable to administer decorporation agents presumptively to minimize exposure. Those with sufficiently serious injuries must be stabilized and sent for medical treatment without regard to radiological factors (NCRP 2008). They must be sent for medical treatment at the earliest opportunity and the administration of decorporation agents should be considered as soon as medically feasible. • Persons with moderate injuries and who do not appear to have embedded radioactive fragments or contaminated wounds will be assigned a score of 3 points. • Persons with light injuries and who do not appear to have embedded radioactive fragments or contaminated wounds will be assigned a score of 2 points. • Persons with light injuries and who do not appear to have embedded radioactive fragments or contaminated wounds will be assigned a score of 1 point.

Proximity to explosion or scene of attack Proximity to the detonation of an RDD or to the scene of a radiological release increases the risk of intake. For example, airborne radionuclide concentrations will be higher—and the potential for inhalation or ingestion will be higher—for those close to the site of a radiological release (overt or covert). Similarly, as contamination is spread from the scene of a radiological release, the contamination levels (and the potential for exposure) will be higher for those closer to the scene. Thus, for those who can accurately remember their location at the time of their exposure, proximity to the site of the release can provide useful qualitative information. A number of organizations have published guidance on safe stand-off distances from a variety of explosive charges, from pipe bombs to tractor-trailer rigs. For the purposes of this document it is assumed that the release was due to an explosive RDD with an explosive charge equivalent to 1,814 kg of trinitrotoluene (TNT). The U.S. Federal Emergency Management Agency (FEMA) has published reports and training documents on explosive effects, including the Reference Manual to Mitigate Potential Terrorist Attacks Against Buildings (FEMA 2003). According to this document, the detonation of a small delivery truck containing this amount of explosive can cause broken glass to a distance of about 610 m, can shatter glass with sufficient force to embed fragments in victims to a distance of 152 m, and the blast itself can cause injuries to a distance of 122 m. The size of the assumed device is the same as that used in the 1995 Oklahoma City bombing (Michel and Herbeck 2002). While not the largest terrorist bomb ever used (the bombs used to attack the Marine barracks in Beirut in 1983 and the Khobar Towers in 1996 were equivalent to 9,072 kg of TNT), this device was among the largest such terrorist bombs used in the United States. This size device is also the largest that can be carried in a rental vehicle such as a panel van or small delivery truck that does not require a special license (e.g., commercial driver’s license) to hire (NYDMV 2015). A smaller device will not distribute radioactive material as far, making this a fairly conservative assumption. While individual fragments of shrapnel can be thrown a considerable distance, the majority of contamination debris spread from an explosive RDD will not be traveling on ballistic trajectories. Studies performed by Musolino et al. (2013) suggest that the majority of the contamination will be thrown to a distance no more than about 250 m and that the radioactive plume can expose members of the public to lesser degrees of inhaled radioactive material to a distance of




2,000 m. Accordingly, Musolino et al. (2013) recommend establishing initial “hot zone” boundaries at a distance of 250 m, and establishing a shelter-in-place zone at a distance of 500 m in all directions and at a distance of 2,000 m downwind of an explosion. These distances are consistent with those noted in the FEMA document mentioned in the previous paragraph (FEMA 2003). For the purposes of this technical report the distances noted in Musolino et al. (2013) will be used for scoring. • Persons who can reliably place themselves at a distance of less than 250 m will be assigned 3 points. • Persons who can reliably place themselves at a distance of greater than 250 m and less than 500 m will be assigned 2 points. • Persons who can reliably place themselves at a distance of greater than 500 m and less than 2,000 m in the downwind direction will be assigned 1 point. • Persons who were outside the distances noted above will be assigned 0 points. Presence of dust or debris on clothing or in the hair Explosions produce dust and debris; these will be blown outward by the blast or carried downwind. Contamination from an explosive RDD can be expected to travel in a similar manner. Although those appearing at the CRCs might have first changed clothing, showered, or both, they could nevertheless provide qualitative information about the amount of contamination that was on their clothing and body before their self-decontamination. Thus, the presence of dust or debris can be used as a proxy for the amount of contamination that might have settled onto a person’s body. • Heavy dust and debris is defined as the majority of a person’s clothing and/or skin being coated with a thick layer of dust. Debris is defined as solid particles, chips, splinters, and so forth that might be embedded in the clothing or adhered to the skin. Persons with heavy dust and debris will be assigned a score of 3 points. • Moderate dust and debris is defined as a significant amount of a person’s skin and/or clothing being coated with dust. Persons with moderate dust and debris will be assigned a score of 2 points. • Light dust or debris is defined as a minor amount of a person’s skin or clothing having sparse or intermittent dust. Persons with light dust and debris will be assigned a score of 1 point. • Persons with no dust or debris on their skin or clothing will be assigned 0 points. Person smelled or tasted smoke or dust As noted above, the presence of smoke or dust can serve as a proxy for the presence of contamination. Persons who report having smelled or tasted dust or smoke can be assumed to have also been exposed to inhaled or ingested

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radioactive material, because radioactive particles are likely to be caught up in the same blast wave and air currents as the dust and smoke. Making the assumption that exposure to dust and smoke carries with it exposure to airborne radionuclides is, thus, a conservative assumption. • Persons who report noticing a strong smell or taste of smoke or dust will be assumed to have been exposed to the most airborne contamination. These people will be assigned a score of 3 points. • Persons who report noticing a moderate smell or taste of smoke or dust will be assumed to have been exposed to intermediate levels of airborne contamination. These people will be assigned a score of 2 points. • Persons who report noticing the smell or taste of smoke or dust only lightly or intermittently will be assigned a score of 1 point. • A 0-point score in this category is not recommended, as a light or intermittent smell of smoke or dust might not be remembered. DERIVATION OF INTERNAL DOSE SCORES FROM QUANTITATIVE FACTORS Skin contamination The presence of skin contamination, at the very least, indicates that a person was exposed to radioactive contamination and indicates the potential for an intake. In addition, some radionuclides (e.g., isotopes of iodine) are readily absorbed through the skin, and skin contamination with such radionuclides is very frequently associated with an uptake. Not only that, but in a violent event such as a terrorist bombing, there is the potential for injuries that, if contaminated, can introduce contamination directly into the body. Finally, contaminated skin—especially that of the hands—can transfer contamination to food or drink that can be ingested, not to mention the possibility of direct ingestion if the person contaminated puts their fingers into their mouth (e.g., nail biting, thumb sucking, etc.). Because of this, persons with skin contamination are considered to be at greater risk of internal contamination. However, skin contamination alone will not be sufficient to refer a person for decorporation; rather, it will call for the collection of further qualitative and quantitative data, and this, in turn, might yield a sufficiently high score to refer a person for decorporation. Persons with no detectable skin contamination will receive a score of 0. In the absence of sufficiently high scoring on qualitative factors (e.g., they reported having smelled or tasted smoke and dust) such persons may be sent home with no further actions required. However, it is noted that the absence of skin contamination might also be due to a person having self-evacuated and selfdecontaminated prior to reporting for screening. Therefore,



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the absence of skin contamination does not necessarily indicate that a person was never contaminated. For this reason, a lack of skin contamination alone is insufficient reason to send a person home without further assessment. Skin contamination levels, especially those that call for further action, must be chosen with care. On the one hand, levels must be sufficiently low as to minimize the risk of uptake and to minimize radiation dose to the skin from the contamination (VARSKIN 5; Hamby et al. 2014). On the other hand, limits that are too low can lead to the unnecessary decontamination or assessment of persons who are likely at no risk; this in turn can take valuable time and resources (e.g., limited supplies of decorporation agents) from those who might be more in need of care. For example, following the Fukushima reactor accident the initial limit for skin contamination was 6,000 cpm. When it became clear that, with this limit, more people were being referred for decontamination than could be accommodated at local facilities, the Japanese government revised the release limit to 13,000 cpm and later to 100,000 cpm.5 The Conference of Radiation Control Program Directors (CRCPD) developed and published a guidance document that includes recommended skin contamination levels that call for various actions (CRCPD 2006). Their recommended release levels, based on using pancake GM probes at 2.54 cm from the radiation source, were: • “With contamination up to 1,000 cpm, allow individuals to leave; instruct them to go home and shower. • If the event is large and if adequate decontamination resources are not available, the release level can be increased to 10,000 cpm. Instruct people to go home and shower. • Send people with contamination levels greater than 10,000 cpm to a designated decontamination area. • People contaminated to levels greater than 100,000 cpm are likely to have internal contamination and should be identified as a priority for follow-up for internal contamination.” These levels are appropriate for use in designated decontamination and screening locations such as CRCs, especially if the default survey instrument used is a pancaketype GM probe or equivalent. Facial contamination The presence of contamination on the face increases the likelihood of an intake, because it indicates that a person’s breathing zone was contaminated and that the contamination may have been introduced into the body through the nose or mouth. In addition, a person with facial contamination who eats or drinks can potentially spread the facial contamination into the food or drink where it can subsequently be ingested. For these reasons, the presence of contamination 5

Japanese government news reports from 11 March 2011 to 13 April 2011; available from the corresponding author on request.


on the face (especially the mouth and nose) increases the likelihood that internal contamination is present. Conversely, the absence of facial contamination is not conclusive since a person might have showered or washed their face before reporting for screening. According to NCRP Report 161, nasal swabs can indicate that radioactive material might have been inhaled (NCRP 2008). This report (and sources cited within) suggests that the amount of activity on a swab of both nostrils might be approximately 5% of the total amount of activity inhaled into the deep lungs. However, this report also notes that there are a great number of factors that reduce the efficacy of nasal swabs as a method for estimating uptake. For example, a person who is a mouth breather (due to heavy exertion, clogged sinuses, etc.) will have less activity deposited in the nose. Similarly, blowing the nose, a cold that causes the nose to run, or the absorption of soluble radionuclides into the body through mucus membranes can all reduce the accuracy of nasal swabs. In Report 161 NCRP states that “because of the highly variable and rapidly changing nature of nasal retention, NCRP is not recommending the use of nasal swab results as a sole criterion when making decisions concerning dose intervention among members of the public following a radiation mass casualty incident.” While external monitoring of the nose and mouth can be performed relatively quickly, obtaining nasal swabs is somewhat more time consuming, and the swabs must then be counted using appropriate equipment. For these reasons, as well as for the concerns noted by the NCRP, the interpretation of nasal swab counts is not included in this paper. While such counts can be used as an indicator of the potential for an uptake, the results can only be used semiquantitatively to indicate the need for further examination. Although this information cannot be used in a quantitative manner, contamination of the mouth and nose is a stronger indicator of the possibility of an uptake than is the presence of skin contamination. Accordingly, the threshold levels for scoring have been reduced to reflect this, as can be seen by comparing the scoring shown for contamination of skin, nose, and mouth indicated above in the Methodology section. Chest or abdominal counts A definite indication that radionuclides have been ingested into the body is their presence in the lungs or abdomen; this would be revealed by performing a chest or abdominal count. It is important to note that the results of such a count are useful only if they are obtained after the removal of all contamination on the clothing and skin.6 6

A recent (June 2017) accident in Japan led to what was initially thought to be a significant plutonium inhalation. In fact, more detailed evaluation determined that there was little or no internal contamination; the initial counts were apparently due almost entirely to external contamination that was not completely removed prior to screening.




The presence of skin or clothing contamination will lead to overestimating the amount of internal contamination and the resulting dose. In addition, chest or abdominal counts are useful only if the radionuclides inhaled or ingested emit gamma radiation with a sufficiently high energy to penetrate the body to reach the detector. In addition, when a pancaketype GM detector is used, the gamma energy must be sufficiently high to be detected with this probe. Accordingly, it is not appropriate to attempt to quantify internal 241Am or internal alpha- and beta-emitting radionuclides by performing a chest count using a GM pancake probe. A number of documents have been developed over the years that help relate chest or abdominal count rate measured with various instruments to radionuclide uptake (e.g., NCRP 2010). More recently, Bolch et al. (2012) revisited this subject in a more comprehensive manner. The numerical results were published as a series of handbooks on the website of the Centers for Disease Control and Prevention; it is these values from Handbooks G and H that are used in this document (CDC 2012). Bolch et al. discuss a number of factors involved in using external radiation readings to determine internal contamination levels and the concomitant exposure. These include the energy of the emitted radiation and its attenuation by the body, the body size of the person being monitored, counting efficiency for the detector in question for the emitted gamma energy, and so forth. All other factors being equal, for example, a smaller person will have less tissue overlying radioactive material in the lungs, and the same amount of activity will yield a higher count rate. Since radiation dose is a measure of energy deposition per unit mass, a smaller person has less mass and requires less radioactive material to receive the same radiation exposure as in a larger person. At the same time, radiation from inhaled radionuclides is less attenuated when escaping from a smaller person with less overlying mass between the lungs and the skin. For example, the count rate from the chest of a man who has inhaled enough 60Co to produce a dose of 0.05 Sv, measured 1 d postinhalation, will be about 1,820 cpm, while the same 60Co quantity will result in a count rate from an adult woman of 2,070 cpm. From the energy emission perspective, the higherenergy 60Co gammas (1.17 and 1.33 MeV) are less attenuated by overlying body tissues than is the 0.662 MeV gamma from 137Cs, and the lower-energy gammas deposit less energy per decay, so it requires more 137Cs to produce the same dose as 60Co. Count rates for men and women for a 0.05 Sv uptake of 137Cs are 630 and 568 cpm, respectively; they are 4,670 and 3,480 cpm, respectively, for men and women who have inhaled enough 192Ir (which has even lower-energy gammas than 137Cs) to produce this same exposure.

243

Bolch et al. provide values for count rate on the abdomen and chest, both AP and PA, at a number of times postexposure from 0.5 h to 30 d (Bolch et al. 2012). The count rate corresponding to a particular level of dose drops monotonically with time, reflecting both accumulated dose (thus reducing the amount of remaining activity required to produce a given exposure) and the absorption and redistribution of radionuclides in the body with time. It is unlikely that any persons will be evaluated for internal radioactive contamination in less than 12 h postexposure, and evaluations might continue for a week or longer. When plotted (as shown in Fig. 3), the curve of count rate (normalized to time 0) versus elapsed time begins to flatten out at a time of about 2 d for 60Co, 137Cs, and 192Ir. To be conservative it is suggested that one use the count rate at a time of 4 d postexposure when applying this procedure in the aftermath of a sudden event that exposes large numbers of people (e.g., RDD attack or the release of large amounts of radioactive material from a nuclear power plant). This is conservative in that anyone evaluated sooner than 4 d postexposure will have higher counts (and therefore a lower dose) than expected by making this assumption. Given that the target survey rate for a CRC location is 1,000 persons per location per hour, a system of six locations will require about 170 h (about 1 wk) to survey the anticipated 1 million people expected to desire screening. The 4 d point is midway through this period of time, and the count rate at this point is only about 10–20% higher than the count rate 7–10 d postexposure. The count rate at the 4 d point is about 30–60% of the count rate at 12 h postexposure. With respect to the area counted, the count rate measured AP (i.e., with the detector on the back) is consistently lower than the count rate measured PA for both men and women. This means that performing a chest count is more sensitive than placing the detector on a person’s back, giving a lower detection level. However, given that both men and women will be surveyed and there might be insufficient numbers of trained females performing the surveys, it is assumed that women will

Fig. 3. Normalized lung counts vs. time.



244

Health Physics


The count rates shown in Tables 3a and 3b make it clear that a pancake-type GM detector is capable of detecting an inhalation uptake of 60Co, 137Cs, or 192Ir that would produce a dose of 0.05 Sv. Typical background count rate for a pancake GM is between 50–100 cpm, and the lowest count rate in these tables is about 300 cpm, 3–6 times the normal background. Thus, a pancake GM is easily capable of detecting and quantifying a 0.05 Sv uptake in both men and women after 4 d have elapsed. Because these count rates are calculated, they are directly proportional to the calculated dose, and in theory it is possible to determine radiation exposure from the measured count rate. A word of caution against this, however: due to both measurement uncertainties and uncontrollable variables (such as body weight and build), trying to determine exposure any more precisely than in 0.05 Sv increments is not recommended. Note also that the count rates provided by Bolch et al. (2012) include more significant figures than can be justified in making measurements in the field, given the uncertainties inherent in performing a relatively quick count with a handheld pancake GM probe. It is suggested that no more than two significant figures can be justified, given these uncertainties. Tables 3a and 3b list three gamma-emitting radionuclides that can be detected from

be surveyed with the detector held in contact with the back. The term “lung count” is used to allow for counting the chest or the back. Finally, the size of the particles inhaled affects the retention of particles in the lungs. In general, smaller particles have a higher surface-area-to-volume ratio, and these particles dissolve more quickly than do larger particles. Therefore, a lung count performed after 4 d on a person who has inhaled 5 mm particles will give a higher count rate (all other factors being equal) than will a lung count on a person who inhaled 1 mm particles. Depending on the solubility and biokinetics of the radionuclide(s) inhaled, this means that inhaling smaller particles should produce a lower dose to the lung, but possibly a higher dose to the whole body. Tables 2a–f, containing data presented in Bolch et al. (2012), summarize some of the factors discussed above. Tables 3a and 3b summarize the relevant data from Bolch et al. (2012) to compare the count rates AP vs. PA for particle sizes of 1 and 5 mm on both men and women at a time of 4 d postinhalation. Tables 3a and 3b show that, for 60Co, 137Cs, and 192Ir, neither particle size nor survey location make a significant difference in the count rate corresponding to uptakes that will produce doses of 0.05, 0.25, and 0.5 Sv in both men and women.

Table 2a. Chest (AP) and back (PA) count rates for adult men and women corresponding to uptakes of 0.05, 0.25, and 0.5 Sv, following inhalation of 1 mm (AMAD) particles of 60Co as measured with a pancake-type GM, for various times postinhalation. Co inhalation, 1 mm AMAD (cpm)

60

0.05 mSv Male Time (hr) 0.5 1 2 4 6 8 10 12 14 16 18 20 24 48 72 96 120 144 168

0.25 Sv Female

Male

0.50 Sv Female

Male

Female

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

2750 2570 2270 2130 2130 2120 2110 2080 2050 2010 1960 1920 1820 1350 1100 984 930 901 882

1940 1830 1700 1620 1590 1570 1550 1520 1500 1480 1450 1430 1390 1210 1130 1080 1060 1040 1020

3270 3090 2880 2720 2630 2560 2490 2430 2360 2300 2240 2180 2070 1640 1450 1370 1320 1290 1270

2000 1930 1820 1710 1660 1620 1580 1540 1510 1480 1450 1430 1380 1180 1090 1040 1020 997 981

13,700 12,900 11,300 10,700 10,600 10,600 10,500 10,400 10,200 10,000 9820 9590 9120 6740 5490 4920 4650 4510 4410

9700 9170 8490 8090 7950 7840 7730 7620 7500 7390 7270 7160 6950 6070 5640 5420 5280 5180 5100

16,400 15,400 14,400 13,600 13,200 12,800 12,500 12,100 11,800 11,500 11,200 10,900 10,400 8220 7270 6840 6620 6470 6360

9980 9660 9080 8560 8290 8080 7890 7720 7560 7410 7270 7130 6890 5900 5440 5210 5080 4980 4900

27,500 25,700 22,700 21,300 21,300 21,200 21,100 20,800 20,500 20,100 19,600 19,200 18,200 13,500 11,000 9840 9300 9010 8820

19,400 18,300 17,000 16,200 15,900 15,700 15,500 15,200 15,000 14,800 14,500 14,300 13,900 12,100 11,300 10,800 10,400 10,200 10,000

32,700 30,900 28,800 27,200 26,300 25,600 24,900 24,300 23,600 23,000 22,400 21,800 20,700 16,400 14,500 13,700 13,200 12,900 12,700



PA 20,000 19,300 18,200 17,100 16,600 16,200 15,800 15,400 15,100 14,800 14,500 14,300 13,800 11,800 10,900 10,400 10,200 9970 9810


245

Table 2b. Chest (AP) and back (PA) count rates for adult men and women corresponding to uptakes of 0.05, 0.25, and 0.5 Sv, following inhalation of 5 mm (AMAD) particles of 60Co as measured with a pancake-type GM, for various times postinhalation. Co inhalation, 5 mm AMAD (cpm)

60

0.05 mSv Male Time (hr) 0.5 1 2 4 6 8 10 12 14 16 18 20 24 48 72 96 120 144 168

0.25 Sv Female

0.50 Sv

Male

Female

Male

Female

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

5630 5130 4300 3930 3930 3920 3890 3820 3730 3630 3520 3400 3150 1900 1260 981 863 808 778

3030 2760 2390 2180 2120 2080 2030 1980 1930 1880 1830 1770 1680 1250 1050 961 916 888 868

6050 5560 4980 4570 4370 4200 4030 3860 3700 3540 3390 3250 2970 1890 1410 1220 1130 1090 1060

3210 3050 2740 2470 2340 2240 2160 2080 2010 1940 1870 1810 1690 1220 1010 913 868 842 824

28,000 25,600 21,500 19,700 19,600 19,600 19,400 19,100 18,700 18,200 17,600 17,000 15,800 9520 6300 4910 4320 4040 3890

15,200 13,800 12,000 10,900 10,600 10,400 10,200 9920 9660 9390 9130 8870 8380 6260 5260 4800 4580 4440 4340

30,200 27,800 24,900 22,800 21,900 21,000 20,200 19,300 18,500 17,700 17,000 16,200 14,900 9430 7070 6100 5670 5450 5310

16,100 15,200 13,700 12,300 11,700 11,200 10,800 10,400 10,000 9700 9370 9050 8470 6090 5030 4570 4340 4210 4120

56,000 51,300 43,000 39,300 39,300 39,200 38,900 38,200 37,300 36,300 35,200 34,000 31,500 19,000 12,600 9810 8630 8080 7780

30,300 27,600 23,900 21,800 21,200 20,800 20,300 19,800 19,300 18,800 18,300 17,700 16,800 12,500 10,500 9610 9160 8880 8680

60,500 55,600 49,800 45,700 43,700 42,000 40,300 38,600 37,000 35,400 33,900 32,500 29,700 18,900 14,100 12,200 11,300 10,900 10,600

32,100 30,500 27,400 24,700 23,400 22,400 21,600 20,800 20,100 19,400 18,700 18,100 16,900 12,200 10,100 9130 8680 8420 8240

Table 2c. Chest (AP) and back (PA) count rates for adult men and women corresponding to uptakes of 0.05, 0.25, and 0.5 Sv, following inhalation of 1 mm (AMAD) particles of 137Cs as measured with a pancake-type GM, for various times postinhalation. Cs inhalation, 1 mm AMAD (cpm)

137

0.05 mSv Male Time (hr) 0.5 1 2 4 6 8 10 12 14 16 18 20 24 48 72 96 120 144 168

0.25 Sv Female

Male

0.50 Sv Female

Male

Female

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

1330 1250 1140 1020 941 876 823 779 743 712 687 665 630 540 509 492 481 473 467

791 754 742 712 682 657 636 619 604 592 581 572 557 512 493 481 472 465 460

2010 2000 1910 1670 1440 1250 1100 969 869 785 715 657 568 369 319 300 290 284 280

1030 1020 980 872 771 688 620 566 523 488 459 435 399 325 308 299 293 289 285

6660 6250 5720 5120 4710 4380 4110 3890 3710 3560 3430 3320 3150 2700 2550 2460 2410 2370 2340

3960 3770 3710 3560 3410 3290 3180 3090 3020 2960 2910 2860 2780 2560 2460 2400 2360 2330 2300

10,000 9980 8560 8330 7190 6250 5480 4850 4340 3930 3580 3290 2840 1840 1600 1500 1450 1420 1400

5170 5080 4900 4360 3850 3440 3100 2830 2610 2440 2290 2170 1990 1630 1540 1490 1460 1440 1430

13,300 12,500 11,400 10,200 9410 8760 8230 7790 7430 7120 6870 6650 6300 5400 5090 4920 4810 4730 4670

7910 7540 7420 7120 6820 6570 6360 6190 6040 5920 5810 5720 5570 5120 4930 4810 4720 4650 4600

20,100 20,000 16,100 16,700 14,400 12,500 11,000 9690 8690 7850 7150 6570 5680 3690 3190 3000 2900 2840 2800



PA 10,300 10,200 9800 8720 7710 6880 6200 5660 5230 4880 4590 4350 3990 3250 3080 2990 2930 2890 2850

246

Health Physics


Table 2d. Chest (AP) and back (PA) count rates for adult men and women corresponding to uptakes of 0.05, 0.25, and 0.5 Sv, following inhalation of 5 mm (AMAD) particles of 137Cs as measured with a pancake-type GM, for various times postinhalation. Cs inhalation, 5 mm AMAD (cpm)

137

0.05 mSv Male Time (hr) 0.5 1 2 4 6 8 10 12 14 16 18 20 24 48 72 96 120 144 168

0.25 Sv Female

Male

0.50 Sv Female

Male

Female

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

1510 1420 1290 114 1050 976 915 863 821 785 754 728 685 568 527 507 495 486 480

809 802 797 767 733 705 681 660 643 616 604 586 531 507 494 485 478 472 467

2010 2000 1910 1670 1440 1250 1100 969 869 785 715 657 568 369 319 300 290 284 277

1030 1020 980 872 710 688 620 566 523 488 459 435 399 325 308 299 293 289 285

7560 7080 6430 5720 5250 4880 4570 4320 4110 3930 3770 3640 3420 2840 2640 2530 2470 2430 2400

4050 4010 3990 3830 3670 3520 3400 3300 3220 3140 3080 3020 2930 2650 2540 2470 2420 2390 2360

10,000 9980 9560 8330 7190 6250 5480 4850 4340 3930 3580 3290 2840 1840 1600 1500 1450 1420 1400

5170 5080 4900 4360 3850 3440 3100 830 2610 2440 2290 2170 1990 1630 1540 1490 1460 1440 1430

15,100 14,200 12,900 11,400 10,500 9760 9150 8630 8210 7850 7540 7280 6850 5680 5270 5070 4950 4860 4800

8090 8020 7970 7670 7330 7050 6810 6600 6430 6160 6040 5860 5310 5070 4940 4850 4780 4720 4670

20,100 20,000 19,100 16,700 14,400 12,500 11,000 9690 8690 7850 7150 6570 5680 3690 3190 3000 2900 2840 2770

PA 10,300 10,200 9800 8720 7100 6880 6200 5660 5230 4880 4590 4350 3990 3250 3080 2990 2930 2890 2850

Table 2e. Chest (AP) and back (PA) count rates for adult men and women corresponding to uptakes of 0.05, 0.25, and 0.5 Sv, following inhalation of 1 mm (AMAD) particles of 192Ir as measured with a pancake-type GM, for various times postinhalation. Ir inhalation, 1 mm AMAD (cpm)

192

0.05 mSv Male Time (hr) 0.5 1 2 4 6 8 10 12 14 16 18 20 24 48 72 96 120 144 168

0.25 Sv Female

Male

0.50 Sv Female

Male

Female

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

7530 6910 6300 5920 5770 5650 5520 5400 5270 5150 5020 4900 4670 3580 3020 2740 2600 2510 2440

4060 3600 3290 3010 2830 2690 2570 2470 2390 2320 2260 2200 2110 1800 1660 1580 1530 1480 1450

11,100 10,400 9500 8200 7240 6470 5830 5300 4870 4500 4180 3910 3480 2250 1820 1630 1540 1480 1440

5480 5060 4590 3960 3500 3150 2860 2630 2450 2300 2170 2070 1900 1490 1340 1270 1220 1190 1160

37,600 34,600 31,500 29,600 28,900 28,200 27,600 27,000 26,400 25,700 25,100 24,500 23,300 17,900 15,100 13,700 13,000 12,500 12,200

20,300 18,000 16,500 15,100 14,200 13,500 12,900 12,400 12,000 11,600 11,300 11,000 10,500 9000 8300 7900 7630 7420 7230

55,500 52,200 47,500 41,000 36,200 32,300 29,100 26,500 24,300 22,500 20,900 19,600 17,400 11,200 9080 8150 7690 7400 7190

27,400 25,300 22,900 19,800 17,500 15,700 14,300 13,200 12,300 11,500 10,900 10,300 9520 7440 6720 6350 6120 5940 5790

75,300 69,100 63,000 59,200 57,700 56,500 55,200 54,000 52,700 51,500 50,200 49,000 46,700 35,800 30,200 27,400 26,000 25,100 24,400

40,600 36,000 32,900 30,100 28,300 26,900 25,700 24,700 23,900 23,200 22,600 22,000 21,100 18,000 16,600 15,800 15,300 14,800 14,500

111,000 104,000 95,000 82,000 72,400 64,700 58,300 53,000 48,700 45,000 41,800 39,100 34,800 22,500 18,200 16,300 15,400 14,800 14,400



PA 54,800 50,600 45,900 39,600 35,000 31,500 28,600 26,300 24,500 23,000 21,700 20,700 19,000 14,900 13,400 12,700 12,200 11,900 11,600


247

Table 2f. Chest (AP) and back (PA) count rates for adult men and women corresponding to uptakes of 0.05, 0.25, and 0.5 Sv, following inhalation of 5 mm (AMAD) particles of 192Ir as measured with a pancake-type GM, for various times postinhalation. Ir inhalation, 5 mm AMAD (cpm)

192

0.05 mSv Male Time (hr) 0.5 1 2 4 6 8 10 12 14 16 18 20 24 48 72 96 120 144 168

0.25 Sv Female

0.50 Sv

Male

Female

Male

Female

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

7530 6910 6300 5920 5770 5650 5520 5400 5270 5150 5020 4900 4670 3580 3020 2740 2600 2510 2440

4060 3600 3290 3010 2830 2690 2570 2470 2390 2320 2260 2200 2110 1800 1660 1580 1530 1480 1450

13600 12800 11600 10100 8990 8110 7370 6740 6210 5760 5360 5010 4420 2610 1940 1670 1540 1470 1420

6090 5660 5090 4380 3880 3490 3190 2940 2740 2570 2430 2310 2110 1570 1370 1270 1210 1180 1140

37,600 34,600 31,500 29,600 28,900 28,200 27,600 27,000 26,400 25,700 25,100 24,500 23,300 17,900 15,100 13,700 13,000 12,500 12,200

20,300 18,000 16,500 15,100 14,200 13,500 12,900 12,400 12,000 11,600 11,300 11,000 10,200 9000 8300 7900 7630 7420 7230

68,000 63,900 58,000 50,400 45,000 40,500 36,800 33,700 31,100 28,800 26,800 25,000 22,100 13,100 9720 8330 7700 7350 7120

30,400 28,300 25,500 21,900 19,400 17,500 15,900 14,700 13,700 12,800 12,100 11,500 10,600 7840 6830 6350 6070 5880 5720

75,300 69,100 63,000 59,200 57,700 56,500 55,200 54,000 52,700 51,500 50,200 49,000 46,700 35,800 30,200 27,400 26,000 25,100 24,400

40,600 36,000 32,900 30,100 28,300 26,900 25,700 24,700 23,900 23,200 22,600 22,000 21,100 18,000 16,600 15,800 15,300 14,800 14,500

136,000 128,000 116,000 101,000 89,900 81,100 73,700 67,400 62,100 57,600 53,600 50,100 44,200 26,100 19,400 16,700 15,400 14,700 14,200

PA 60,900 56,600 50,900 43,800 38,800 34,900 31,900 29,400 27,400 25,700 24,300 23,100 21,100 15,700 13,700 12,700 12,100 11,800 11,400

triage should keep in mind that higher scores might warrant higher priority for treatment for the radiological exposure.

within the body using a pancake GM detector, the significant count rates, and the corresponding number of points to be assigned for each range of count rates. In the scoring system presented in the next section, the approximate radiation exposure (CEDE) associated with these values are: • 1 point < 0.05 Sv (< 0.2 CDG). • 5 points 0.05–0.25 Sv (0.2–1 CDG). • 15 points 0.25–0.5 Sv (1–2 CDG). • 25 points > 0.5 Sv (> 2 CDG).

COMPREHENSIVE SCORING SYSTEMS AND ACTIONS TO BE TAKEN The previous section described information that will be collected during the radiological assessment process, how that information (both quantitative and qualitative) will be evaluated, and how that information will be scored. The scoring for these qualitative and quantitative factors is summarized in Tables 4, 5a, and 5b; upon completion of scoring, each of the qualitative and quantitative factor scores will be added to calculate the sum. What is even more important than the scoring, however, is the interpretation of these scores and the actions that will be taken as a result.

Additionally, anyone with a score of 15 points or higher or any exposure that is likely to lead to a dose of 0.25 Sv or higher will be referred for decorporation therapy. Thus, lung counts that correspond to a dose of 0.25 Sv or higher will receive a score of 15 points. Those performing radiological

Table 3a. Count rate, pancake GM, 6 cm, 4 d postexposure, male, inhalation. 60

137

Co (Type M, cpm)

1 μm Dose (Sv) 0.05 0.25 0.50

192

Cs (Type F, cpm)

5 μm

1 μm

Ir (Type M, cpm)

5 μm

1 μm

5 μm

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

984 4920 9840

1080 5420 10,800

981 4910 9810

961 4800 9610

492 2460 4920

481 2400 4810

507 2530 5070

494 2470 4940

1090 5460 10,900

1180 5920 11,800

876 4380 8760



PA 1000 5010 10,000

248

Health Physics


Table 3b. Count rate, pancake GM, 6 cm, 4 d postexposure, female, inhalation. 60

137

Co (Type M, cpm)

1 μm Dose (Sv) 0.05 0.25 0.50

192

Cs (Type F, cpm)

5 μm

1 μm

Ir (Type M, cpm)

5 μm

1 μm

5 μm

AP

PA

AP

PA

AP

PA

AP

PA

AP

PA

AP

1370 6840 13,700

1040 5210 10,400

1220 6100 12,200

913 4570 9130

300 1500 3000

299 1490 2990

311 1560 3110

307 1540 3070

1630 8150 16,300

1270 6350 12,700

1670 8330 16,700

In addition, the dose assessment process described in this document is intended to help quickly sort people into appropriate treatment categories based on the information available shortly after a radiological emergency: (1) those people who show evidence of sufficient radionuclide uptake, or sufficient radiation dose, to have a potential clinical (in the short term) or public health (in the long term) impact; (2) those who require additional assessment via further in vivo or in vitro bioassay; or (3) those whose exposure is too low to be of clinical significance and who can be sent home without further medical assessment. Appropriate evaluation and refinement of the dose estimate as well as appropriate actions will likely continue for weeks, months, and even years following the radiological event. Based on the NCRP Report 161 concept of CDG, it is recommended that all persons with an uptake of greater than 1 CDG be referred for decorporation therapy, and this should continue until their radionuclide burden is reduced to 0.2 CDG or lower, unless advised otherwise by the attending physician and/or the local radiological advisory committee (NCRP 2008).

PA 1270 6350 12,700

The next section discusses how to evaluate and make a decision based on the scores assigned during the initial doseassessment process and how to refine these dose estimates to ensure that each person receives proper medical assessment and follow-up actions appropriate for their exposure. NCRP Report 161 emphasizes that medical injuries must take priority over radiological concerns. This is reasonable as many medical problems pose an immediate threat to life or health, while a person exposed to a lethal dose of radiation might live for several weeks following the exposure (NCRP 2008). Thus, gravely injured persons must be treated for their injuries and stabilized first. Radiological information shall be recorded to be used when the radiological assessment and decorporation or treatment actions are performed at a later stage when the patient is in stable condition. Finally, note that the radiological assessment discussed in this study is only the first step of a long process and that any person who has had exposure to high doses of radiation (in excess of 0.25 Sv) or who has had an uptake of radioactive material should be evaluated on a recurring basis until

Table 4. Consolidated scoring for qualitative factors. Category

0 points

Injuries to person No injuries

1 point

2 points

3 points

Comments

Light injuries with no contaminated wounds

Moderate injuries Serious injuries Automatic referral for with no contaminated with no contaminated decorporation if there wounds wounds is any contaminated wound OR if there are any embedded radioactive fragments Proximity to Distant from Greater than 2 km Greater than 250 Closer than 250 m Distances based on explosion point of release downwind, greater and less than 500 m in any direction Musolino et al. (2013) (e.g., attack than 500 m laterally in any direction and on explosive takes place in stand-off distances another borough) in FEMA (2003) Dust or debris on No zero-point Light intermittent Light dust over Moderate to heavy No zero-point option skin and clothing option since dust on skin and majority of body dust on majority of since trace contamination trace contamination clothing body, solid debris might not be visible. might not make an on clothing, in hair, Assumes some might impression or because or stuck to skin practice self-decon person might not at home. have noticed due to other factors Persistent smell Smelled or tasted No zero-point option Vaguely aware of Heavy smell of dust or smoke for same reson noted smelling or tasting or taste of dust or dust or smoke smoke during and from explosion for dust or debris smoke or dust sufficient to cause after evacuation coughing or choking www.health-physics.com



Table 5a. Consolidated scoring for facial and skin contamination levels as measured using a pancake-type GM. cpm

Points

Action

Facial contamination 100,000

5

Continue screening — scan mouth and nose Continue screening — scan mouth and nose, perform chest count, decontaminate (if resources permit) Continue screening — scan mouth and nose, perform chest count, decontaminate

Skin contamination 50,000

5

Continue screening — perform chest count Continue screening — perform chest count, decontaminate (if resources permit) Continue screening — perform chest count, decontaminate

evaluation provides no additional useful information or until the amount of radioactive material remaining in their body is reduced to levels that no longer pose a significant radiation exposure. This continuing evaluation may include (but need not be limited to) more precise bioassay (both in vitro and in vivo), counting using instruments with higher sensitivity and accuracy, and additional techniques such as those described below under “Other dose assessment options.” Immediate referral for decorporation without scoring Some forms of exposure are sufficiently serious to warrant presumptive decorporation therapy without any initial assessment. This would include persons with contaminated wounds, embedded radioactive fragments, and similar injuries. The rationale is that with such persons, it is safe to assume that there is sufficient uptake to warrant decorporation therapy; at the same time, it is unlikely that there will be so many such persons as to place a strain on potentially limited emergency resources.

249

High scores (> 15 points)—refer for medical care (e.g., decorporation) Any person with a score of 15 points or higher from the internal exposure score should be referred for decorporation therapy with an appropriate decorporation agent (NCRP 2008, 2010). Decorporation therapy should follow medical stabilization and should, in turn, be accompanied by continuing bioassay measurements to track the elimination of radionuclides from the body and to reassess the amount of activity remaining in the body. In addition, there will likely be a need for repeated rounds of decorporation therapy, depending on the amount of activity taken up, the nuclide(s) involved, and the biokinetics of those nuclides. Decorporation should be halted when the residual radionuclide activity is reduced to 0.2 CDG or lower. Intermediate scores (5–15 points)—refer for further medical assessment or decorporation if available Persons with intermediate levels of uptake cannot be sent home without further assessment, but in a resourcelimited environment (i.e., when there are inadequate supplies of decorporation agents to treat a large number of people), it may be impossible to send them all for decorporation therapy. If there are adequate supplies to treat people in this category, then it is prudent to refer everybody with more than 5 points for decorporation therapy and to continue working to refine their dose estimates during this time. If further assessment indicates a minor level of uptake (less than 0.2 CDG), then this therapy may be discontinued. Low scores (< 5 points)—send home and refer to the family physician It is likely that the majority of people reporting for dose assessment will have little or no exposure to either internal or external radiation. In Goiania, Brazil, for example, over 112,000 people requested radiological screening; of this number, fewer than 400 required medical attention (IAEA 1988). Given that the only persons who are expected to be sent for dose assessment are those with evidence of skin contamination or radiological uptake, it is likely that a higher fraction of those at the dose assessment station are likely to require follow-up; however, it is still expected that the majority will have low scores indicating low or no radiation exposure. Persons with less than 5 points for internal exposure

Table 5b. Scoring for lung counts as measured with a pancake-type GM. 1 point Nuclide 60

Co

137

Cs Ir

192

5 points

15 points

25 points

Male

Female

Male

Female

Male

Female

Male

3,000

250

Health Physics

should be given informational materials and then sent home and advised to follow up with their family physician. Other dose assessment options—as time and resources permit If there is any question regarding the proper course of action to take with any person who has received a high internal or external radiation exposure, the physician(s) should contact an appropriate expert organization such as the Radiation Emergency Action Center/Training Site (REAC/TS; https://orise.orau.gov/reacts/) or International Atomic Energy Agency (https://www.iaea.org/) for advice. For information, the U.S. Department of Health and Human Services Radiation Emergency Medical Management (REMM) website (https://www.remm.nlm.gov) should be contacted. There is a large literature base on radiation dose assessment (e.g., Brackett et al. 2008) and the treatment of radiation injury. In brief, the common methods that are available for refining dose estimates are discussed in detail in the references of this study and in the medical literature. Ideally, information collected using methods discussed in the literature can be used in conjunction with information collected when using this study, and this consolidated set of information will yield a more accurate dose assessment than those depending on any one single method. Additional information could be obtained from in vitro bioassay (urinalysis, fecal sampling, blood sampling, etc.), in vivo bioassay (whole-body scanning, thyroid counting, etc.), chromosome aberration analysis (e.g., Garty et al. 2010), lymphocyte depletion kinetics, and radiation exposure prognosis charts (e.g., Flynn and Goans 2012; DHHS 2018). Lenhart (2012) addresses this in great detail; the chapter authored by Blakely (2012) is particularly useful.

CONCLUSION In the aftermath of any large-scale radiological event, there will be a need to be able to rapidly screen large numbers of people to identify those who are at risk and require radiological assessment, those for whom no action is needed, and those requiring referral for further examination to determine their need for decorporation. By using both quantitative and qualitative measures and assigning scores to these various parameters, even a person who is not trained in radiation safety can quickly determine which category a person falls into. One can note that qualitative factors are inherently uncertain and, in many cases, are subject to poor memory; for this reason, assigning fewer points for qualitative factors than for quantitative factors is recommended. One may also note that some radionuclides (low-energy gamma emitters and all alpha and beta emitters) are unable to penetrate the chest wall to reach the detector—consequently,


chest counting for internal contamination is ineffective for these radionuclides. In addition, it is further noted that by being conservative with both qualitative and quantitative factors, one can be comfortable that nobody who requires decorporation therapy will be inappropriately denied treatment. This study has presented each of these factors and discussed how to assign points for each parameter. It has further discussed the evaluation of these points and relevant actions to be taken. Finally, the study has mentioned additional dose assessment methodologies and how they can be incorporated into the dose assessment process to refine dose estimates as further information becomes available.

Acknowledgments—The authors would like to thank Sigurdar Magnusson, Armin Ansari, and Dick Toohey for their valuable feedback and encouragement during the course of this work.

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