1

Advisory Committee on the Medical Use of Isotopes (ACMUI)

Patient Release Report

December 13, 2010

Subcommittee Members: D. Fisher, Ph.D.; D. Gilley, MPA; S. Langhorst, Ph.D. (Chair); S. 

Mattmuller, MS, R.Ph, BCNP; O. Suleiman, Ph.D.; B. Thomadsen, Ph.D.; J. Welsh, M.D.; P. 

Zanzonico, Ph.D.

Charge: To evaluate patient release/human research subject release issues; to objectively review 

and analyze data, which may include state regulations and guidance as well as recommendations in 

international guidance documents; to provide a statement on the issues, including patient release to 

other than private residences and an annual rather than per-release limit on radiation doses to others 

from released individuals; and, if appropriate, to provide recommendations for improvements to 

existing NRC rules and guidance.

Summary Statements and Recommendations

1. The medical use of radioactive materials provides important diagnostic and therapeutic tools 

that have well-recognized health benefits1,2,3,4

. Use of radionuclides in medicine and patient 

access to radionuclide medical procedures, with associated public doses at or below typical 

environmental background levels, should not be burdened by excessive regulatory controls, 

including controls that may lead some practitioners to avoid their use or to deliver sub-optimal 

care (such as multiple lower-administered activity treatments) simply to comply with regulatory 

dose limits. The Subcommittee affirms that radiation doses to other individuals from 

radioactivity in released patients5 can be safely controlled by:

• the current 10 CFR 35.75 patient release criteria6

• licensees’ use of scientifically developed dose-based release calculation methods, and 

patient release instructions based on individual patient circumstances, and 

, 

• patients’ and caregivers’ understanding of and adherence to the patient release instructions.

 1 NCRP Commentary No. 11, “Dose Limits for Individuals Who Receive Exposure from Radionuclide Therapy 

Patients”, National Council on Radiation Protection and Measurements, February 1995.

2 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004. 3 NCRP Report No. 155, “Management of Radionuclide Therapy Patients”, National Council on Radiation Protection 

and Measurements, December 2006.

4 IAEA Safety Reports Series No. 63, “Release of Patients after Radionuclide Therapy”, International Atomic Energy 

Agency, 2009.

5

 Use of the term “patient” in this report is intended to also include human research subject. 6 NRC Regulation 10 CFR 35.75, “Release of individuals containing unsealed byproduct material or implants 

containing byproduct material”, Nuclear Regulatory Commission.
December 13, 2010

2

Relevant regulations should not be overly prescriptive because the licensee is best qualified to 

assess the suitability of individual patients for release post-treatment and to provide 

personalized guidance to patients to assure compliance with the applicable release criteria.

2. Current 10 CFR 35.75 patient release criteria, along with NRC RIS 2003-047

, appropriately 

balance public safety with patient access to medical treatment.

• Based on NRC conclusions documented in the final rulemaking8

• National and international scientific recommendations on patient release are consistent, in 

principle and practice, with NRC patient release regulations and guidance. 

and lack of further 

rulemaking changes to these criteria, the current patient release criteria should continue to be 

considered as per-release dose limits until modified by future rulemaking. 

• The NRC per-release 5 mSv (500-mrem) dose limit for any individual is consistent with 

ICRP and IAEA recommendations for caregivers and other members of the patient’s 

household.

• For all other members of the general public, NRC requires the licensee to provide written 

instructions to the patient on ways to keep radiation dose as low as reasonably achievable, or 

less than 1 mSv (100 mrem). Specifically, these instructions further protect children, 

pregnant women, and non-caregivers.

3. Current NRC guidance on patient release calculations9 overestimates caregiver and public doses 

because the guidance assumes unrealistically conservative assumptions. The Subcommittee 

recommends that:

• NRC guidance and assumptions should be updated, with assistance from experts, and should 

include current information on actual radiopharmaceutical biokinetics and calculated or 

measured patient dose rates. 

• Updated scientifically-based tools should be developed to assist licensees in determining and 

documenting compliance with the patient release criteria. 

• Reasonable assumptions should be employed for calculating realistic doses to people from a 

released patient. 

• In addition to private residences, release scenarios should address patient release to other 

locations (such as hotels, public transport, public events). 

4. Current NRC instructions for patient release9 should be updated, in conjunction with release 

calculation methods and assumptions, and the NRC should support research efforts to advance 

understanding and communication of circumstances that impact patient release decisions, 

instructions and perceptions. 

 7

 NRC Regulatory Issue Summary 2003-04 “Use of the Effective Dose Equivalent in Place of the Deep Dose 

Equivalent in Dose Assessments” (February 13, 2003).

8 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket No. 

RIN 3150-AE41, January 29, 1997. 9 NRC Regulatory Guide 8.39, “Release of Patients Administered Radioactive Materials”, Nuclear Regulatory 

Commission, April 1997.
December 13, 2010

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Scientific Evaluation of Patient/Human Research Subject Release Issues

Experts in radiation protection10,11 apply three fundamental principles to the use of radioactive 

materials:

• The Principle of Justification: Any decision that alters the radiation exposure situation 

should do more good than harm.

• The Principle of Optimization of Protection: The likelihood of incurring exposure, the 

number of people exposed, and the magnitude of their individual doses should all be kept as 

low as reasonably achievable (ALARA), taking into account economic and societal as well 

as medical factors.

• The Principle of Application of Dose Limits: The total dose to any individual from 

regulated sources in planned exposure situations other than medical exposure of patients 

should not exceed the appropriate limits specified.

The appropriate use of radioactive materials in medicine is accepted as doing more good than 

harm. Exposure to the patient is intentional for the direct medical benefit of the patient. Radiation 

protection experts oppose dose limits for patients because doing so may compromise the 

effectiveness of the patient’s diagnosis or treatment, and thus do more harm than good. Experts 

emphasize the physician’s informed medical justification for a patient’s medical procedure while 

maintaining the patient’s radiation dose as low as reasonably achievable, again taking into account 

economic and societal as well as medical factors.

Exposure to Other Individuals from Patients Released from Licensee Control

Patients undergoing therapeutic medical procedures using radioactive materials become a 

radiation source that may expose other individuals, and therefore warrant appropriate precautions 

for limiting doses to those individuals. Patients undergoing diagnostic radiopharmaceutical 

procedures may also expose other individuals to radiation fields. The likely dose to others from 

nuclear medicine or implant procedures is low, but not necessarily zero12,13. Individuals most 

likely to be exposed to a released patient are the patient’s family members, or other person caring 

for or comforting the patient (caregiver), who will be in physical proximity of the patient in the 

initial days following release. Reducing the need for hospital stays also provide patients, their 

families and caregivers psychological and emotional benefits of having the patient with them and of 

lowering their health care costs13,14

 10 NCRP Report No. 116, “Limitation of Exposure to Ionizing Radiation”, National Council on Radiation Protection and 

Measurements, March 1993.

. This also provides societal benefits by reducing the direct 

economic costs, and commitment, of medical resources required to retain the patient in a hospital, 

11 ICRP Publication 103, “The 2007 Recommendations of the International Commission on Radiation Protection”, 

March 2007.

12 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

13 NRC NUREG-1492, “Regulatory Analysis on Criteria for the Release of Patients Administered Radioactive 

Materials, Final Report”, by Stewart Schneider and Stephen A. McGuire, Nuclear Regulatory Commission, April 1996. 14 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket 

No. RIN 3150-AE41, January 29, 1997.
December 13, 2010

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and the indirect costs of a patient’s or their employer’s lost work time15. Exposures to other 

individuals can be effectively managed by the educated patient (or parent or guardian) after release 

if that patient follows the instructions provided by the licensee. These instructions help the patient 

to maintain doses to levels comparable to or less than variations in natural background radiation 

doses. Given the balance of personal and societal benefits gained, and the ability to maintain doses 

to others as low as reasonably achievable levels, the NRC concluded in its final rulemaking that the 

benefits outweigh the potential of small increased risks associated with the release of patients 

administered radioactive materials16,17.

Scientific Development of Current NRC Patient Release Criteria

In the early 1990s, the NRC received three petitions for rule making18,19,20 concerning the 10 

CFR 35.75 patient release criteria, which at that time included an activity-based limit and 10 CFR 

20.1301 public dose limits. In response to these petitions, the NRC initiated rulemaking to change 

patient release criteria to dose rate-based limits21. The NRC evaluated patient release criteria which 

appropriately applied the three fundamental principles previously discussed. The NRC considered 

three alternatives in its cost-benefit analysis15 of the controlling criteria for determining when a 

patient may be released from the licensee’s control:

Alternative 1 – 1 mSv (100 mrem) per year dose limit in 10 CFR 20.1301 

Alternative 2 – less than 1,110 MBq (30 mCi) or less than 0.05 mSv/h (5 mrem/h) at 1 

meter per the activity-based, which was the 1996 version of 10 CFR 35.75 22

Alternative 3 – 5 mSv (500 mrem) dose limit

NRC concluded that Alternative 3 best served the interest of patients and society16 for the 

following reasons:

1. All of the alternatives were compatible with generally accepted radiation protection 

principles.

2. Alternative 1 was dismissed due to its excessive economic costs and adverse psychological 

impact on patients and their families due to the required patient isolation.

 15 NRC NUREG-1492, “Regulatory Analysis on Criteria for the Release of Patients Administered Radioactive 

Materials, Final Report”, by Stewart Schneider and Stephen A. McGuire, Nuclear Regulatory Commission, April 1996. 16 NRC SECY 96-100: “Final Amendments to 10 CFR Parts 20 and 35 on Criteria for the Release of Individuals 

Administered Radioactive Material”, Nuclear Regulatory Commission, May 8, 1996.

17 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket 

No. RIN 3150-AE41, January 29, 1997. 18 56 FR 26945: “Carol S. Marcus; Filing of Petition for Rulemaking”, NRC Docket No. PRM-20-20, June 12, 1991. 19 57 FR 8282: “American College of Nuclear Medicine; Receipt of Petition for Rulemaking”, NRC Docket No. PRM35-10, March 9, 1992; and 57 FR 21043: “American College of Nuclear Medicine; Receipt of Amended Petition for 

Rulemaking”, NRC Docket No. PRM-35-10A, May 18, 1992. 20 59 FR 37950: “American Medical Association; Petition for Rulemaking”, NRC Docket No. PRM-35-11, July 26, 

1994. 21 59 FR 30724: “Criteria for the Release of Patient Administered Radioactive Material, Proposed Rule”, NRC Docket 

No. RIN 3150-AE41, June 15, 1994. 22 Also referred to as the “30-mCi rule”
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3. Alternative 3 was preferred over Alternative 2 because of its more favorable costeffectiveness and more positive psychological impact on patients and their families.

4. Basing patient release criteria on the dose to individuals exposed to a patient provided the 

consistent, scientific basis of dose for such decisions that treats all radionuclides on a riskequivalent basis. The 30-mCi limit (Alternative 2), which may have been appropriate for 

iodine-131 under some circumstances, was excessive for some patients and clinical 

situations using certain other radionuclides (projected doses would be well below the dose 

limit), but inadequate for other situations and radionuclides (projected doses exceed the dose 

limit).

5. Alternative 3 allowed physicians flexibility to not have to fractionate therapy doses, leading 

to improved effectiveness of treatment for the patient while avoiding unnecessary 

hospitalization associated with the 30-mCi rule23

6. Reduction of medically unwarranted hospital stays provided emotional benefits to patients 

and their families. Allowing earlier reunion of families could improve the patient's state of 

mind, which in itself improved the outcome of the treatment and led to the delivery of more 

effective health care. At the same time, the opportunity to personally care for a seriously ill 

family member was comforting to many individuals.

.

Today, the Subcommittee affirms the thorough analysis found in NUREG-1492 and its rational 

evaluation of the three alternatives. The NRC’s final decision to implement Alternative 3 as the 

patient release criteria found in 10 CFR 35.75 appropriately balanced the three fundamental 

radiation protection principles for use of radioactive materials in medicine.

Current National and International Recommendations Regarding Released Patients

The National Council on Radiation Protection and Measurements (NCRP) recommendations24

specific to release criteria for radionuclide therapy patients in place at the time NRC established the 

current 10 CFR 35.75 release criteria were as follows: 

Other Individual NCRP24 Recommended Dose Limit

Public 1 mSv/y, but 5 mSv/y may be used for infrequent 

exposures

Patient’s Family, Adults 5 mSv/y, 50 mSv/y with special training

Patient’s Family, Children and Pregnant 

Women 1 mSv/y

The NCRP also concluded in this commentary that “a contamination incident that could lead to a 

significant intake of radioactive material is very unlikely”25. The most recent NCRP Report on the 

subject maintains those same limits26

 23 In locations where the 30-mCi rule is in effect, some physicians treat thyroid cancer with multiple administrations of 

29.9 mCi of I-131 for no reason other than to avoid hospitalization of patients, thereby treating the patient in a 

protracted, less therapeutically-effective manner, which can compromise the treatment and, ultimately, the well-being of

the patient. When physicians choose to treat thyroid cancer with one administration greater than 30 mCi of I-131, 

patients can be denied treatment, some for many months, until a private hospital bed is available.

.

24 NCRP Commentary No. 11, “Dose Limits for Individuals Who Receive Exposure from Radionuclide Therapy 

Patients”, National Council on Radiation Protection and Measurements, February 1995.
December 13, 2010

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The International Commission on Radiation Protection (ICRP) recently updated its 

recommendations on limiting dose to other individuals from the release of patients after therapy 

with unsealed radionuclides27. The ICRP recommendations incorporate the concept of dose 

constraint, rather than a dose limit, as follows:

Other Individual ICRP27 Recommendations 

Public 1 mSv/y (limit)

Relatives, Visitors, and Caregivers A few mSv/episode (constraint)

Infants, Young Children, and Casual Visitor 1 mSv/y (limit)

The International Atomic Energy Agency (IAEA) also recently published a safety series report 

on the release of radionuclide therapy patients28. The IAEA endorsed the ICRP recommendations 

and further clarified its criteria in a recent position statement29.

All three of the above authoritative national and international advisory bodies agreed that the 

decision to hospitalize or release a patient should be determined on an individual basis and should 

be based on dose criteria rather than on residual-activity criteria (as with the previous 30-mCi rule). 

The physician’s decision should also take into account the patient’s wishes and medical 

condition, his or her physical and mental capacity to understand and follow instructions, 

occupational and public exposures, family considerations (including the presence of children and 

pregnant women in the household), cost, and environmental factors. These advisory bodies’ 

recommendations incorporated the concept of maintaining the dose to other individuals as low as 

reasonably achievable, and recognized the need for flexibility in the regulatory authority’s practical 

application of limits and constraints so that patient physical and psychological factors, as well as

economic and societal factors, are properly considered.

The ICRP noted that determination of the overall costs associated with various methodologies 

related to release of patients after therapy with unsealed radionuclides had generally not been 

attempted27. The ICRP stated: 

“Ideally, ‘costs’ should include psychological and adverse health consequences, as well as 

monetary costs. Cost-benefit analysis for a specific issue may vary substantially from 

country to country, but it does provide a tool that may help the optimization process.” 

 25 NCRP Commentary No. 11, “Dose Limits for Individuals Who Receive Exposure from Radionuclide Therapy 

Patients”, National Council on Radiation Protection and Measurements, February 1995.

26 NCRP Report 155, “Management of Radionuclide Therapy Patients.” National Council on Radiation Protection and 

Measurements, December 2006.

27 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

28 IAEA Safety Reports Series No. 63, “Release of Patients after Radionuclide Therapy”, International Atomic Energy 

Agency, 2009.

29 IAEA Position Statement, “Release of Patients after Radionuclide Therapy”, International Atomic Energy Agency, 

February 23, 2010.
December 13, 2010

7

The ICRP cited the NRC’s NUREG-1492 cost-benefit analysis as a scientifically appropriate 

example. 

The Subcommittee finds the current 10 CFR 35.75 release criteria to be consistent with the 

practical application of nationally and internationally recommended dose constraints and limits, and

to be in harmony with public safety, humane patient care, and cost-effective delivery of medical 

treatment.

Control of Dose to Other Individuals from Released Patients

In contrast to diagnostic nuclear medicine procedures, doses to the public, patients’ relatives, 

and others may need to be limited after some therapeutic procedures. The preponderance of peerreviewed scientific data demonstrate that the radiation dose from internal contamination of other 

individuals from released patients is far less significant than that from external exposure30,31,32,33. 

Because of its physical properties and the extent of its use, I-131 is the most likely therapeutic 

radionuclide having potential to cause radiation dose to medical staff, the public and family 

members. Therefore, the Subcommittee has focused its review on circumstances associated with I131 therapy patients.

Prior to patient release, the licensee has responsibilities established by NRC regulations and 

license conditions for controlling dose to other individuals exposed to an I-131 therapy patient. 

These controls incorporate well-established and straightforward concepts of limiting exposure: 

minimizing time, maximizing distance from the source (i.e., the patient), and, to the extent practical, 

using shielding. Controls include measures to prevent or at least minimize radioactive 

contamination; a medical facility’s use of universal precautions34,35 and infection controls36,37

effectively achieve this. The licensee has responsibility to evaluate the circumstances of the 

planned patient release to ensure compliance with 10 CFR 35.7538

 30 NCRP Commentary No. 11, “Dose Limits for Individuals Who Receive Exposure from Radionuclide Therapy 

Patients”, National Council on Radiation Protection and Measurements, February 1995.

, which permits a licensee to 

“authorize the release from its control any individual who has been administered unsealed 

byproduct material or implants containing byproduct material if the total effective dose equivalent 

to any other individual from exposure to the released individual will not likely exceed 5 mSv (0.5 

31 NRC NUREG-1492, “Regulatory Analysis on Criteria for the Release of Patients Administered Radioactive 

Materials, Final Report”, by Stewart Schneider and Stephen A. McGuire, Nuclear Regulatory Commission, April 1996. 32 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

33 IAEA Safety Reports Series No. 63, “Release of Patients after Radionuclide Therapy”, International Atomic Energy 

Agency, 2009.

34 OSHA Regulation 29 CFR 1910.1030, “Bloodborne Pathogens”, Occupational Safety & Health Administration, 

Department of Labor.

35 CDC Fact Sheet, “Universal Precautions for Prevention of Transmission of HIV and Other Bloodborne Infections”, 

Centers for Disease and Control Prevention, Department of Health and Human Services, 1996 update.

36 CDC, “Guidelines for Environmental Infection Control in Health-Care Facilities”, Centers for Disease and Control 

Prevention, Department of Health and Human Services, 2003.

37 CDC, “2007 Guidelines for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare 

Settings”, Centers for Disease and Control Prevention, Department of Health and Human Services, 2007. 38 NRC Regulation 10 CFR 35.75, “Release of individuals containing unsealed byproduct material or implants 

containing byproduct material”, Nuclear Regulatory Commission.
December 13, 2010

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rem)”. The licensee is also required to “provide the released individual, or the individual's parent or 

guardian, with instructions, including written instructions, on actions recommended to maintain 

doses to other individuals as low as is reasonably achievable if the total effective dose equivalent to 

any other individual is likely to exceed 1 mSv (0.1 rem)”. This regulatory language characterizes 

the responsibility of the licensee as ensuring that the dose to an individual from a released patient is 

not likely to exceed the specified dose limit, rather than as certitude that the dose limit will not be 

exceeded.

In the case of an orally administered therapeutic radionuclide (such as I-131 sodium iodide), 

vomiting shortly after its administration is a contamination concern. The NRC concluded in its

final rulemaking for the current 10 CFR 35.7539:

“Vomiting is seldom an important elimination route for radiopharmaceuticals after the patient 

has left the medical facility since orally administered radiopharmaceuticals such as iodine-131 

are rapidly absorbed, within a half hour, by the gastrointestinal system.”

Vomiting is a rare event, and can often be prevented by giving antiemetics to the patient prior to 

administration of the radionuclide. The risk of vomiting in public can be further mitigated by 

having the patient remain in a designated monitored area at the facility for a short period of time

post-administration, when vomiting is most likely.

Once an I-131 therapy patient is released, NRC’s regulatory control, and thus the licensee’s 

responsibilities40, ends

39

. At this point, the patient, parent or guardian assumes responsibility for 

managing radiation exposure to other individuals based on instructions provided by the licensee. 

These instructions should be straightforward and easy to follow so that the patient will understand 

how to minimize radiation doses to other individuals as low as reasonably achievable. Instructions 

include maintaining distance from other people, minimizing time in public places, measures to 

reduce the spread of radioactive contamination, and the length of time the patient should follow 

each such precaution41. As part of the implementation of the current 10 CFR 35.75 release criteria, 

the NRC worked with the Society of Nuclear Medicine (SNM) to prepare a pamphlet that provides 

practical information for patients receiving treatment with radioiodine42. The NRC noted in final 

rulemaking for the current 10 CFR 35.7539 that “American medical practice routinely depends on 

patients following instructions, such as instructions on when and how to take medications”.

As a licensee reviews the I-131 therapy patient’s post-release living and traveling 

circumstances, certain precautions may be emphasized or lengths of time adjusted for special

circumstances, such as those involving potential exposure of children or pregnant women or the 

need to use public transportation to return home or to stay in a hotel or other non-private residence 

 39 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule” (NRC Docket 

No. RIN 3150-AE41), January 29, 1997. 40 The term “licensee’s responsibilities” refers only to the control of radioactive material under NRC regulations, and 

does not include the physician’s continuing responsibilities for medical care of the patient. 41 NRC Regulatory Guide 8.39, “Release of Patients Administered Radioactive Materials”, Nuclear Regulatory 

Commission, April 1997.

42 SNM Pamphlet, “Guidelines for Patients Receiving Radioiodine Treatment,” Society of Nuclear Medicine, 1997. 

This pamphlet may be obtained from the Society of Nuclear Medicine, 1850 Samuel Morse Drive, Reston, VA 20190-

5316.
December 13, 2010

9

prior to returning home. As the IAEA noted43, “The success of a patient release program is 

critically dependent on the quality and specificity of the information provided to the patient, the 

skill with which it is communicated, and whether or not the patient believes the information 

provided.” The IAEA also advised that the precautions “should be based upon realistic models of 

behavior, including realistic occupancy factors, and should not be over-cautious”44.

The NRC adopted a dose-based limit in its final rulemaking because it “better expresses the 

NRC’s primary concern for the public’s health and safety”45. Scientists46,47 have measured doses to 

other individuals, primarily family members and other caregivers, from released I-131 therapy 

patients, and the actual doses received by these individuals are significantly less than those 

conservatively projected by the licensee as the basis for the patient release.

Use and Misuse of Conservative Assumptions in Estimating Dose to Other Individuals

With implementation of the current 10 CFR 35.75 release criteria, the NRC issued guidance48 to 

assist licensees with determining when a patient could be released, when instructions to patients 

were required, and what records must be generated and maintained. NRC guidance on calculating 

dose to other individuals was primarily based on release of an I-131 therapy patient using what is 

now judged to be very conservative assumptions49,50. As noted, the IAEA advised that these dose 

calculations should be realistic and not overly-cautious

44

. Although NRC’s 1997 guidance was

conservative, the NRC practice of establishing risk-informed and performance-based regulations51

allowed licensees the practical flexibility to use more reasonable guidance and realistic calculations 

in determining compliance with the current 10 CFR 35.75 release criteria45

.

As previously discussed, licensees must evaluate an I-131 therapy patient’s post-release living 

circumstances in order to choose reasonable specific calculation assumptions and to provide 

appropriate instructions specific for that patient. On the other hand, when performing such analyses 

for a generalized patient population, more conservative assumptions may be chosen to account for a 

greater range of living or traveling circumstances. And, experts may assume activities, distances, 

occupancy factors, and so forth, that far exceed values likely to be encountered in practice to 

 43 IAEA Safety Reports Series No. 63, “Release of Patients after Radionuclide Therapy”, International Atomic Energy 

Agency, 2009.

44 IAEA Position Statement, “Release of Patients after Radionuclide Therapy”, International Atomic Energy Agency, 

February 23, 2010.

45 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket 

No. RIN 3150-AE41, January 29, 1997. 46 Grigsby PW, Siegel BA, Baker S, & Eichling, JO. “Radiation exposure from outpatient radioactive iodine (I-131) 

therapy for Thyroid Carcinoma”. JAMA. 2000;283:2272–2274. 47 Rutar FJ, Augustine SC, Colcher D, et al. “Outpatient treatment with 131I-anti-B1 antibody: radiation exposure to 

family members”. J Nucl Med. 2001;42:907–915. 48 NRC Regulatory Guide 8.39, “Release of Patients Administered Radioactive Materials”, Nuclear Regulatory 

Commission, April 1997.

49 Siegel JA, Marcus CS, Stabin MG, “Licensee Over-Reliance on Conservatisms in NRC Guidance Regarding the 

Release of Patient Treated with I-131”, Health Physics (93:667-677), December 2007. 50 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

51 NRC “The Risk-Informed and Performance-Based Plan (RPP)”, http://www.nrc.gov/about-nrc/regulatory/riskinformed/rpp.html. 
December 13, 2010

10

thereby demonstrate that if such highly improbable scenarios are compatible with release criteria, 

then more realistic dose projections could be expected to be much lower. However, some may 

misuse the end result from such extreme calculations uncritically, that is, without consideration of 

how unrealistic the underlying assumptions are, and thus precipitate unnecessary public safety 

concerns and alarm.

An example of such a calculation is found in the latest ICRP recommendations52. The ICRP 

made this calculation to demonstrate the importance of an I-131 therapy patient taking precautions 

to reduce or prevent internal contamination of children and infants. The ICRP’s concluding 

statements accompanying this calculation are as follows:

“Contamination of infants and young children with saliva from a treated patient during the 

first few days after radioiodine therapy could result in significant doses to the child’s 

thyroid, and potentially raise the risk of subsequent radiation-induced thyroid cancer”.

“Thyroid cancer as a result of contamination (particularly with saliva) may be a significant 

risk for those under 20 years of age.”

As described in Paragraphs (68) and (69) of the ICRP report52

, the following unrealistic 

assumptions were used:

• The I-131 therapy patient (parent) does not follow the precautions given in their oral and 

written instructions to minimize contact with their own infants and children;

• The I-131 therapy patient (parent) transfers 1 milliliter (e.g., approximately 1⁄4 teaspoon) of 

saliva (55,500 Bq = 1.5 μCi) by kissing the child in the first day after therapy; and,

• The thyroid cancer incidence from this child’s calculated thyroid dose is estimated based on 

preliminary data of cancer incidence being studied in children who ingested larger amounts 

of radioactive iodine and other radionuclides in milk and vegetables contaminated from the 

Chernobyl accident53.

The ICRP report stated that actual measurements from children when parents followed appropriate 

precautions resulted in lower thyroid doses than those indicated by this calculation. In one study54, 

iodine activity was detected in only 25 of 89 children; even though some of these parents did not 

receive, understand, or follow the precautions. So even without proper instruction, 64 of the 89 

children had no detectable iodine activity.

 52 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

53 Another study of children administered diagnostic amounts (5 to 15 μCi) of I-131 found no incidence of cancer –

Dickman PW, et. al., “Thyroid Cancer Risk After Thyroid Examination with I-131: a Population-Based Cohort Study in 

Sweden”, Int. J. Cancer: 106, 580-587 (2003). 54 Barrington, S.F., O’Doherty, M.J., Kettle, A.G., et al. “Radiation Exposure of Families of Outpatients Treated with 

Radioactive Iodine (iodine-131) for Hyperthyroidism”, Eur. J. Nucl. Med. 26, 686–692 (1999).
December 13, 2010

11

The Subcommittee agrees that a released I-131 therapy patient should be instructed to take 

special precautions to minimize dose to children and pregnant women. The 1997 SNM pamphlet55

that many licensees provide to their I-131 therapy patients instructs the patient to avoid kissing the 

first few days following treatment, and to avoid prolonged physical contact, especially with children 

and pregnant women, explaining that the thyroid glands of children and fetuses are more sensitive 

to the effects of I-131 than those of adults. 

The NRC issued a Regulatory Issue Summary (RIS)56 in 2008, which included the first ICRP 

concluding statement listed above, but provided no details regarding the assumptions. The RIS also 

stated:

“However, as described in the Background section of this RIS, for some I-131 therapies, 

such as oral administration of sodium iodide I-131, the ICRP cautions that the internal dose 

to infants and young children who may come in contact with a released patient could be 

significant.”

“The guidance recommends that licensees consider not releasing patients, administered I131, whose living conditions may result in unnecessary exposure of infants and young 

children.”

The intent of this RIS was to remind licensees of precautions (established in 1997 with the current 

10 CFR 35.75 release criteria) that should be discussed with their I-131 therapy patients. The 

Subcommittee recommends that these types of caution statements should be fully explained, and

that future documents of this type should include a statement for patients to consult their physician

for additional information specific to their medical procedure.

Release of I-131 Therapy Patients to Locations other than a Private Residence

The NRC asked the ACMUI to review a draft RIS being developed to address the release of I131 therapy patients to locations other than a private residence. As part of the ACMUI’s analysis, 

the ACMUI Subcommittee calculated the radiation dose to other individuals from release of an I131 therapy patient to a hotel. Despite the possibility of misunderstanding or misuse of the 

resulting calculation and conclusions, the Subcommittee used overly conservative assumptions and 

parameters, along with reasonable ones, to demonstrate that even highly unlikely dose projections 

do not exceed the release criteria and that reasonable doses are comparable to variations in 

background radiation doses.

The example calculations, assumptions used in each case, and the results of this analysis are 

presented in the Report Appendix57

 55 SNM Pamphlet, “Guidelines for Patients Receiving Radioiodine Treatment,” Society of Nuclear Medicine, 1997. 

This pamphlet may be obtained from the Society of Nuclear Medicine, 1850 Samuel Morse Drive, Reston, VA 20190-

5316.

. The Subcommittee concluded that when a licensee assesses 

the I-131 therapy patient’s planned living situation upon release, provides the patient with simple 

56 NRC RIS 2008-11, “NRC Regulatory Issue Summary 2008-11: Precautions to Protect Children Who May Come in 

Contact with Patients Released After Therapeutic Administration of Iodine-131”, Nuclear Regulatory Commission, 

May 2008.

57 See Report Appendix, “Radiation Dose Calculations for I-131 Therapy Patients Released to a Hotel”
December 13, 2010

12

and easily understood oral and written instructions, and judges that the patient, or the patient’s 

parent or guardian, understands the instructions and is capable of complying with the recommended 

precaution actions, then the dose to any other individual exposed to the I-131 therapy patient is 

likely not to exceed 1 mSv even when released to a location other than a private residence.

The ICRP58 suggested that a patient could “stay at a nonhospital living facility, such as a hotel, 

for several days” when the patient’s home situation would put the patient in close contact with 

children due to physical or social constraints, because this “is less expensive than staying in a 

hospital”. Initial research survey results conducted with voluntary respondents from the Thyroid 

Cancer Survivors’ Association indicated that most released patients in the U.S. go to a private 

residence (approximately 94%) and only a few (approximately 5%) go to hotels59. The 

Subcommittee agrees that I-131 therapy patient release to a private residence should be encouraged, 

and that licensees should carefully evaluate patient release to other locations and communicate to 

the patient additional radiation safety precautions that may be appropriate for such locations. 

The Subcommittee discussed management of dose to other individuals exposed to multiple 

released patients as might occur with workers in a hotel near a major medical facility or workers in 

a nursing home. The NRC’s final rulemaking states that its medical experts “concluded that no 

common nuclear medicine practice, be it diagnostic, therapeutic, or a combination of the two, 

results in multiple large administrations that would be likely to cause the 5-millisievert (0.5-rem) 

dose limit to be exceeded because of multiple administrations in a year”60. The Subcommittee 

extensively discussed patient release to hotels in regard to whether:

• dose management is adequate with current patient release instructions, 

• additional guidance and patient instructions are needed, 

• there should be added regulatory criteria, and 

• this dose management would be effectively accomplished by focusing only on I-131 therapy 

patient release rather than trying to sum small doses from all radioactive material released 

patients. 

One Subcommittee member felt that no patients should be released to hotels or other similar 

locations, and one Subcommittee member felt uneasy about allowing this release. Two 

Subcommittee members felt that patients should be allowed to go a hotel, but that a licensee should, 

by NRC guidance, track and control the number of released I-131 therapy patients planning to go to 

specific hotels. Four Subcommittee members felt release to hotels was an acceptable option, and 

there was no need to track or control release to specific hotels because the realistic projected dose to 

others is small61

 58 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004 – see paragraph (106), item (v).

. The different perspectives of the Subcommittee members on how best to assure 

compliance with the applicable dose limits led us to conclude that the NRC should support a wider

discussion on this topic with the medical community and the public.

59 Vetter R, Van Nostrand D, Khorjekar G, et al, Presentation on “Use of a Patient Survey to Evaluate Compliance with 

and Quality of Instructions Given to Patients Treated with Radioiodine”, Annual Meeting of the Health Physics Society, 

Salt Lake City, Utah, June 27-July 1, 2010. 60 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket 

No. RIN 3150-AE41, January 29, 1997. 61 See Report Appendix, “Radiation Dose Calculations for I-131 Therapy Patients Released to a Hotel”
December 13, 2010

13

Annual Dose Limits versus Per-Release Dose Limits

The current 10 CFR 35.75 release criteria were developed in accordance with the NRC’s stated 

practice of implementing risk-informed performance-based regulations for licensees. The NRC 

appropriately recognized that licensees would only be able to judge “likely” doses to other 

individuals based on knowledge shared by patients of their post-release living circumstances and on 

the patients’ ability to follow instructions in maintaining these doses as low as reasonably 

achievable. Once the patient is released, the licensee no longer controls the patients’ actions, and 

patients are not accountable to NRC regulations. As stated in the final rulemaking for 10 CFR 

35.7562:

“The NRC is establishing a dose limit of 5 millisieverts (0.5 rem) total effective dose 

equivalent to an individual from exposure to the released patient for each patient release.”

The ICRP recommended dose constraint of a few mSv/episode “has often been inappropriately 

interpreted as a rigid annual dose limit”63. The Subcommittee considered the consequences of 

changes to the current 10 CFR 35.75 release criteria, which apply to all diagnostic and therapeutic 

radioactive materials administered to patients and human research subjects, from a per-release limit

to a rigid annual dose limit. The primary difficulty identified was the practicality of licensees 

tracking all doses to other individuals on an annual basis, potentially including those from multiple 

therapy administrations to the same patient in a single calendar year. The NRC concluded in their 

final rulemaking that the level of recordkeeping, even when limited to patient releases likely to 

exceed 0.1 mSv, was “an unnecessary burden”, and NRC clearly stated62:

“Each patient release is to be treated as a separate event, and licensee knowledge of previous 

administrations is unnecessary.”

The NRC published a regulatory issue summary in 2008 which stated its intent to pursue 

rulemaking to change the 10 CFR 35.75 patient release criteria from dose limits to dose per year 

limits because the “presumption that patients receive single administrations of therapeutic doses in a 

given year, which is the basis used in developing the wording for the dose limit in 10 CFR 35.75, is 

no longer valid”64. The RIS states NRC’s view of how licensees should manage patient release 

involving multiple administrations or applications in a single year. While the NRC explained that it 

would follow normal rulemaking procedures, including opportunity for public comment, this RIS 

created confusion as to whether the current 10 CFR 35.75 patient release criteria are per-release or 

annual dose limits65. 

 62 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket 

No. RIN 3150-AE41, January 29, 1997. 63 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

64 NRC Regulatory Issue Summary 2008-07: “Dose Limit for Patient Release Under 10 CFR 35.75”, March 27, 2008. 65 Prior to review of the 10 CFR 35.75 rulemaking notices in the Federal Register, polling of the Subcommittee 

members indicated that half of the members believed current release criteria were per-release dose limits and half 

believed the criteria were annual limits.
December 13, 2010

14

The Subcommittee reviewed and compared the Federal Register proposed rulemaking66 and the 

final rulemaking67 which established the current 10 CRF 35.75 patient release criteria. The NRC 

clearly stated in its proposed rulemaking that the patient release criteria would be annual dose 

limits. However, in the final rulemaking, the NRC changed the patient release criteria by dropping 

the annual limits and instead making the limits apply to each patient release. In regard to this 

change, the NRC stated67,

“Upon reconsideration, based on public comments and consultation with the ACMUI, an 

NRC medical consultant, and the NRC Visiting Medical Fellow, the NRC has decided to 

delete this requirement. A review of medical treatment practices revealed no common

practice that would result in doses exceeding the 5 millisievert (0.5 rem) limit because of 

multiple administrations in the same year to the same patient. Without the need to account 

for the dose from multiple administrations, maintaining records for the many tens of 

thousands of patients released when their dose to an individual is likely to exceed 1

millisievert (0.1 millisievert) becomes an unnecessary burden. The requirement to retain 

these records has therefore been deleted. Each patient release is to be treated as a separate

event, and licensee knowledge of previous administrations is unnecessary.”

There has been significant growth in the use of radioactive material medical procedures in the past 

20 years68, and a few medical procedures, including a few I-131 therapy procedures, are 

administered to patients more than one time within a calendar year. However, exposure from 

multiple patients undergoing diagnostic procedures continues to be low in doses to other 

individuals. Exposure to a patient undergoing multiple I-131 therapies (2 to 3) in one year is likely 

to be a low dose to other individuals because of the patient following simple instructions for their 

release. Moreover if one applies the theory of linear no threshold radiation risk, there would be no 

difference in theoretical risk of radiation dose from exposure to an I-131 therapy patient receiving 

two therapies in one calendar year versus exposure to an I-131 therapy patient receiving a therapy 

per year in two calendar years.

Based on the NRC conclusions documented in its final rulemaking67 and lack of further 

rulemaking changes to the current 10 CFR 35.75 patient release criteria, the Subcommittee 

recommends the current patient release criteria should continue to be considered as per-release dose 

limits until modified by future rulemaking. Seven Subcommittee members believe that a new 

requirement for annualized dose limits could severely limit patients’ access to appropriate medical 

care at reasonable costs

69

 66 59 FR 30724: “Criteria for the Release of Patient Administered Radioactive Material, Proposed Rule”, NRC Docket 

No. RIN 3150-AE41, June 15, 1994.

. These Subcommittee members conclude that the most effective and 

practical way to control the dose to other individuals from the release of patients administered 

radioactive materials is to support development of new guidance and other tools to assist: (a) 

67 62 FR 4120: “Criteria for the Release of Individuals Administered Radioactive Material-Final Rule”, NRC Docket 

No. RIN 3150-AE41, January 29, 1997. 68 NCRP Report 160, “Ionizing Radiation Exposure of the Population of the United States”, National Council on 

Radiation Protection and Measurements, March 2009. 69 One Subcommittee member believed that a dose limit would not be a true limit without an associated time frame. 

The remaining Subcommittee members believed strict adherence to an annual dose limit would severely limit access to 

medical care, and that the type and typical number of radioactive material medical procedures for a given patient do not 

result in excessive dose to other individuals in a calendar year. 
December 13, 2010

15

licensees in assessing, carrying out, and documenting patient release; and (b) patients in 

understanding and taking appropriate precautions for their specific living circumstances.

One Subcommittee member felt that the inconsistency and confusion over the per-release and 

annual limit was due to the regulatory nature of the regulation. A per-event limit without an annual 

limit allows an individual to receive multiple exposures. Although highly unlikely, this situation 

would be allowable. Furthermore, an annual limit that is the same as a per-release limit is 

duplicative, since the per-release limit would then be unnecessary. This one Subcommittee member 

believes the simple solution would be to increase the annual limit for a caregiver who is exposed 

more than once in a calendar year.

Petition to Return to Pre-1997 Release Criteria

The NRC was petitioned70 to replace the current dose-based release criteria and to re-instate the 

1986 10 CFR 35.75 release criteria71, widely known as the “30-mCi” rule. The NRC has also 

received other requests to return to this old rule72. The Subcommittee finds no scientific merit in 

returning to such activity-based release criteria, which have no identifiable scientific basis73. The 

Subcommittee maintains that dose-based release criteria are more scientifically rigorous than 

activity-based criteria and better protect the public by basing patient releasability on the quantity, 

dose, directly related to potential radiation hazard rather than on a quantity, activity, indirectly

related to this potential hazard. In the case of I-131 treatment of thyroid cancer, for example, the 

administered I-131 is rapidly excreted (assuming a whole-body biological half-time of only about 2 

days or less). In treating hyperthyroidism, however, 25 to 50% or more of the radioiodine localizes 

in the thyroid, and that activity is cleared from the gland (and, in turn, the body) much more slowly, 

with half-times of about 20 days or longer. Accordingly, the retained activity from the much higher 

activity (typically greater than 100 mCi) administered to the thyroid cancer patient is rapidly 

reduced to a lower activity than that retained by hyperthyroid patients (who typically receive about 

10 mCi)71. Thus, higher dose-rate irradiation of individuals persists longer for lower-activity 

treatment of hyperthyroidism than for higher-activity treatment of thyroid cancer, illustrating the 

fallacy of an idea that activity-based release criteria (i.e. the “30-mCi” rule) is more protective of 

public safety74,75,76.

In fact, the 30-mCi rule is a special case of the 1997 release criteria, based on I-131 with the 

following conditions:

 70 70 FR 75752, “Peter G. Crane; Receipt for Rulemaking”, NRC Docket No. PRM-35-18, December 21, 2005. 71 51 FR 36932, “Medical Use of Radioactive Material-Final Rule”, Nuclear Regulatory Commission, October 16, 

1986.

72 “Radioactive Roulette: How the Nuclear Regulatory Commission’s Cancer Patient Radiation Rules Gamble with 

Public Health and Safety”, A report by the Staff of Edward J. Markey (D-MA), Chairman, Subcommittee on Energy 

and Environment, Energy and Commerce Committee, U.S. House of Representatives, March 18, 2010. 73 Siegel JA, “Tracking the Origin of the NRC 30-mCi Rule”, J Nucl Med. 2000;41:10-16N. 74 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission on 

Radiological Protection, March 2004.

75 IAEA Safety Reports Series No. 63, “Release of Patients after Radionuclide Therapy”, International Atomic Energy 

Agency, 2009.

76 See Report Appendix, “Radiation Dose Calculations for I-131 Therapy Patients Released to a Hotel”.
December 13, 2010

16

• Using the physical half-life instead of the effective half-life, ignoring biological 

elimination of the radionuclide;

• Ignoring the attenuation of the radiation by the patient;

• Using the default occupancy of 0.25 rather than a value based on actual patient behavior 

information.

The 30-mCi rule also represented a “per-release” limit. Returning to the old rule simply would 

ignore physical principles as well as consideration of actual patient behavior in different living 

circumstances. Change from the 30-mCi rule to the current 10 CFR 35.75 patient release criteria in 

no way weakened the NRC rules.

NRC policy was not intended to intrude on the practice of medicine77, yet evidence exists that 

prior to adopting the 1997 risk based release criteria, the former activity-based release criteria 

adversely impacted the practice of medicine and patient care by limiting patients to only 30-mCi 

administered activities simply to allow immediate patient release. This practice essentially 

fractionates the patient’s therapy dose and reduced the effectiveness of therapy. In some countries 

where activity-based release criteria are still used, patients are effectively denied therapy for as long 

as one year because of lack of hospital rooms for overnight accommodation. The Subcommittee

commends the NRC for adopting the current-risk-based criteria.

Developing Updated Guidance in Support of Patient Release Dose Controls

The NRC guidance to licensees on patient release criteria78 was based on dose calculation 

methods and assumptions that are overly conservative and outdated. The Subcommittee 

recommends that the NRC, with assistance from experts, update the patient release guidance using 

reasonable assumptions based on an expanded list of radionuclides used in medicine, current 

radiopharmaceutical biokinetics information, and reported dose measurements from patients. 

Computer-based modes of communications, data gathering, and data processing should be used to 

develop tools and accrue data for guidance of licensees in:

• assessing various living situations, including patient release to other locations (such as 

hotels, public transport, public events), 

• calculating realistic radiation dose to others,

• choosing realistic precautions for patients to take, 

• instructing patients on these precautions and specific applications, and 

• documenting compliance with the patient release criteria.

During this review, the Subcommittee found many scholarly efforts which have advanced 

understanding and communication of real-world situations that impact patient release decisions and 

perceptions. The NRC should support research activities to better identify what aspects of patient 

release have realistic impact on doses to other individuals. As examples, the following efforts

provide insights into various aspects of patient release.

 77 65 FR 47654, “Medical Use of Byproduct Material; Policy Statement, Revision”, Nuclear Regulatory Commission,

August 3, 2000.

78 NRC Regulatory Guide 8.39, “Release of Patients Administered Radioactive Materials”, Nuclear Regulatory 

Commission, April 1997.
December 13, 2010

17

• Measurements of radiation exposure to household members from released patients79

• Surveys of patients and caregivers to determine understanding of and adherence to patient 

release instructions80

• Communication tools to help convey personalized instructions to patients81

• Credible websites providing objective, scientific information about radiation82

• Medical protocol enhancements for patient release83

Patients want access to the best health care. And while release of the I-131 therapy patient is 

most often the focus of evaluating the potential hazard to others, the I-131 patient should not be 

treated unfairly by virtue of need for I-131 therapy. Well-informed patients are self-motivated and 

sensitive to the fact that they are radioactive for a period of time, excreting radioactivity, and will 

typically do as much as possible to reduce potential exposures to family, caregivers, and other 

members of the general public. They need to be reassured that their medical procedure with 

radioactive material is safe for themselves, their family members and their caregivers, and that they 

do not represent a source of harmful radiation exposure to members of the public. Any new NRC 

guidance should be developed with the assistance of experts involved with patient release84, and 

focus on improved patient counseling rather than excessive controlling or monitoring of the patient.

Subcommittee Conclusions on Patient/Human Research Subject Release Issues

The Subcommittee commends the NRC for its leadership role in developing and implementing 

practical regulatory control of the use of radioactive materials in patients which appropriately 

applies the three fundamental radiation protection principles of justification, optimization and 

limits. Benefits from medical use of radioactive materials are many and well-recognized, 

improving the health and lives of millions of people in the U.S. These benefits far exceed the small 

theoretical risks associated with exposure from released patients.

 79 Grigsby PW, Siegel BA, Baker S, & Eichling, JO. “Radiation exposure from outpatient radioactive iodine (I-131) 

therapy for Thyroid Carcinoma”. JAMA. 2000;283:2272–2274. 80 Vetter R, Van Nostrand D, Khorjekar G, et al, Presentation on “Use of a Patient Survey to Evaluate Compliance with 

and Quality of Instructions Given to Patients Treated with Radioiodine”, Annual Meeting of the Health Physics Society, 

Salt Lake City, Utah, June 27-July 1, 2010. 81 Freidman MI, Ghesani M, “Interactive Software Automates Personalized Radiation Safety Plans for Na131I Therapy”, 

Health Physics (83 Supplement 5:S71-S84), November 2002. 82 “Radiation Answers: Answers to Questions About Radiation and You”, www.radiationanswers.org , supported by the 

Health Physics Society.

83 Khorjekar G, Van Nostrand D, Vetter R, et al, Poster on “The Relationship of Several Factors and Vomiting After 

Outpatient I-131 Therapy in Patients with Well-Differentiated Thyroid Cancer”, Society of Nuclear Medicine Annual 

Meeting, Salt Lake City, Utah, June 5-9, 2010. 84 The Subcommittee members differed in their opinions on methods needed to best counsel multiple patients in 

managing release to the same location, but agreed that it is essential for the NRC to work with the medical community 

and the public to develop reasonable and effectual guidance which minimizes impacts on patient access to these medical 

procedures. 
December 13, 2010

18

The Health Physics Society85 recently updated their position statement regarding radiation 

risk86, and stated:

“In accordance with current knowledge of radiation health risks, the Health Physics Society 

recommends against quantitative estimation of health risks below an individual dose of 5 

rem in one year or a lifetime dose of 10 rem above that received from natural sources. 

Doses from natural background radiation in the United States average about 0.3 rem per 

year. A dose of 5 rem will be accumulated in the first 17 years of life and about 25 rem in a 

lifetime of 80 years. Estimation of health risk associated with radiation doses that are of 

similar magnitude as those received from natural sources should be strictly qualitative and 

encompass a range of hypothetical health outcomes, including the possibility of no adverse 

health effects at such low levels. 

There is substantial and convincing scientific evidence for health risks following high-dose 

exposures. However, below 5–10 rem (which includes occupational and environmental 

exposures), risks of health effects are either too small to be observed or are nonexistent.”

Ongoing research efforts are exploring the effects of low-dose radiation exposures87,88 and 

examining whether health impacts exist in populations exposed to low levels of radiation89,90,91,92.

Regulatory decision-making is ultimately a politically based national policy discussion93 which 

is shaped by opinions sometimes based on the perception rather than the reality of risk94. The NRC 

remains an important leader in this national discourse 95

 85 The Health Physics Society is a nonprofit scientific professional organization whose mission is excellence in the 

science and practice of radiation safety. Since its formation in 1956, the Society has grown to approximately 6,000 

scientists, physicians, engineers, lawyers, and other professionals representing academia, industry, government, national 

laboratories, the Department of Defense, and other organizations. Society activities include encouraging research in 

radiation science, developing standards, and disseminating radiation safety information. Society members are involved 

in understanding, evaluating, and controlling the potential risks from radiation relative to the benefits.

. In light of limited health care resources, it 

is increasingly important that regulations serve not only to protect society from real hazards, but 

86 HPS PS010-2, “Radiation Risk in Perspective”, Position Statement of the Health Physics Society, revised July 2010. 87 Brooks AL, “Developing a Scientific Basis for Radiation Risk Estimates: Goal of the DOE Low Research Program”, 

Health Physics (85:85-93), July 2003. 88 Averbeck D, “Does Scientific Evidence Support a Change from the LNT Model for Low-Dose Radiation Risk 

Extrapolation?”, Health Physics (97:493-504), November 2009.

89 Shore RE, “Low-Dose Radiation Epidemiology Studies: Status and Issues”, Health Physics (97:481-486), November 

2009.

90 Dickman PW, et. al., “Thyroid Cancer Risk After Thyroid Examination with I-131: a Population-Based Cohort Study 

in Sweden”, Int. J. Cancer: 106, 580-587 (2003).

91 Ghiassi-nejad M, et al, “Very High Background Radiation Areas of Ramsar, Iran: Preliminary Biological Studies”, 

Health Physics (82:87-93), January 2002.

92 Nair RRK, et al, “Background Radiation and Cancer Incidence in Kerala, India-Karunagappally Cohort Study”, 

Health Physics (96:55-66), January 2009.

93 Locke P, “Incorporating Information from the U.S. Department of Energy Low-Dose Program into Regulatory 

Decision-Making: Three Policy Integration Challenges”, Health Physics (97:510-515), November 2009.

94 Jenkins-Smith HC, Silva CL, Murray C, “Beliefs about Radiation: Scientists, the Public and Public Policy”, Health 

Physics (97:519-527), November 2009.

95 Tenforde TS, Brooks AL, “Perspectives of U.S. Government Agencies on the Potential Role of Greater Scientific 

Understanding of Low-Dose Radiation Effects in Establishing Regulatory Health Protection Guidance”, Health Physics 

(97:516-518), November 2009.
December 13, 2010

19

that they also be based on realistic projections of the severity and likelihood, and on consideration 

of the actual costs, financial and otherwise, from overly cautious and potentially intrusive 

regulations. For radionuclide therapy that has been shown to be a safe, effective, and financially 

viable treatment for certain cancers and other serious diseases, patient release criteria and relevant 

regulations based on realistic dose projections are both conducive to public safety and promote 

access to and affordability of such therapy. The Subcommittee affirms that the current dose-based 

release criteria 10 CFR 35.75 meet these essential benchmarks. 

The Subcommittee therefore concludes that the current 10 CFR 35.75 release criteria 

appropriately balance public safety with patient access to efficacious and cost-effective medical 

treatment. The Subcommittee recommends that the NRC gather scientific data on patient behavior 

and understanding of instructions to determine the most effective instructions to enhance licensee 

communication and documentation of patient release, and to promote patient understanding. The 

Subcommittee further recommends that the NRC update patient release guidance, with assistance 

from experts, to include current information on actual radiopharmaceutical biokinetics and 

calculated or measured patient dose rates, and provide guidance for release scenarios to other 

locations other than private residences (such as hotels, public transport, public events).
December 13, 2010

20

Appendix96 – Radiation Dose Calculations for I-131 Therapy Patients Released to a Hotel 

The Subcommittee conducted a scientific analysis of radiation doses that might be received 

by hotel workers in the event that an iodine-131 (I-131) therapy patient, appropriately released 

from a medical institution, chose to stay in a hotel immediately following the release. We show 

for four scenarios what the radiation doses to hotel workers and other guests could be under 

different sets of parameters. The four scenarios are labeled unrealistic (representing an 

improbable, worst-case scenario), highly unlikely (representing a doubtful scenario, rarely

occurring), conservative (representing a possible scenario, not likely to occur), and realistic

(representing a more likely scenario for a typical patient). The four scenarios involve release to a 

hotel of (1) an I-131 cancer therapy patient (Table 1), and (2) an I-131 hyperthyroid therapy 

patient (Table 2). The assumptions and parameters used for each scenario are described in each 

table. 

Published scientific literature indicates that radiation doses to non-patients from iodine-131 

patients released after therapy may consist of two components: (1) external radiation exposure 

received by standing in close proximity to the patient, and (2) the intake of I-131 contamination 

from I-131 that leaves the patient in excreta or sweat. The literature shows that an individual’s 

radiation dose from the uptake of I-131 contamination is far less significant (less than 10%) than

the radiation dose received from external exposure to the patient 97,98,99,100. Radiation

measurements have shown that internal contamination of family members from radioactive 

patients may only be something on the order of one-millionth of the activity administered to the 

patient. Therefore, the potential radiation dose to a family member or hotel worker from 

internalized contamination left by a released I-131 patient can only be far below that which is 

possible from external doses101,102,103,104,105,106

 96 Appendix to the Advisory Committee on the Medical Use of Isotopes (ACMUI) Patient Release Report, approved 

by the ACMUI on December 13, 2010.

(also see Table 3). In addition, the likelihood of 

97 NCRP Commentary No. 11, “Dose Limits for Individuals Who Receive Exposure from Radionuclide Therapy 

Patients”, National Council on Radiation Protection and Measurements, February 1995.

98 NRC NUREG-1492, “Regulatory Analysis on Criteria for the Release of Patients Administered Radioactive 

Materials, Final Report”, by Stewart Schneider and Stephen A. McGuire, Nuclear Regulatory Commission, April 

1996.

99 ICRP Publication 94, “Release of Patients after Therapy with Unsealed Radionuclides”, International Commission 

on Radiological Protection, March 2004.

100 IAEA Safety Reports Series No. 63, “Release of Patients after Radionuclide Therapy”, International Atomic 

Energy Agency, 2009.

101 Buchan RCT, Brindle JM. “Radioiodine therapy to outpatients—the contamination hazard”. Br J Radiol 43:479–

482; 1970.

102 Hammond N, Jacobson A. An effective method to reduce the exposure to families of radioiodine therapy patients. 

Health Phys. 1982;43:89-172. 103 Jacobson AP, Plato PA, Toeroek D. “Contamination of the home environment by patients treated with iodine131: initial results”. Am J Public Health 68:230–235; 1978.

104 Plato P, Jacobson A, Homann S. “In vivo thyroid monitoring for iodine-131 in the environment”. Inter J Applied 

Radiat Isotopes. 1976;27:539-545.

105 Toeroek D, Jacobson A, Plato P. “Radiation protection of families of radioactive patients”. Health Phys. 

1978;35:911-912. 106 Chandra R, Marshall C. “Radioiodine therapy to out-patients - The contamination hazard (Letter)”. Br J Radiol. 

1971;44:557.
December 13, 2010

21

an intake following intermittent exposure to I-131 contamination of toilets and bedding is very 

small for both immediate family members and for hotel guests or workers107. Even if a hotel 

worker were not to wear gloves while cleaning a released I-131 therapy patient’s room, the risk 

of internalization of I-131 radioactivity remains low – as indicated by the data in the references 

in Footnote 101 and Table 3. 

Despite the use of these overly-cautious assumptions and parameters used in Tables 1 and 2,

the highest projected dose to a hotel housekeeper from a released cancer therapy patient is less 

than 100 mrem. For the case of a released hyperthyroid patient treated for immediate release 

under the 30-mCi rule, where the amount of I-131 administered is 17% of the amount 

administered to the cancer therapy patient (Table 2), the three-day projected doses to a hotel 

housekeeper are 67% of that from the released cancer therapy patient.

The realistic projected doses to hotel workers are very low. To give a perspective of how 

safe these projected doses are, the average U.S. dose from natural background radiation is 310 

mrem per year108, or 0.85 mrem per day. The highest realistic hotel worker dose of 1.2 mrem 

would be equivalent to an extra 1.4 days of natural background radiation. The highest realistic 

guest dose of 22 mrem would be equivalent to an extra 26 days of natural background radiation.

Use of patient-specific parameters in conjunction with realistic assumptions of behavior by 

the patient, hotel workers and other guests should be used when calculating a particular patient 

release.

 107 Personal correspondence from M.G. Stabin, Ph.D., CHP. 108 NCRP Report No. 160, “Ionizing Radiation Exposure of the Population of the United States”, National Council

on Radiation Protection and Measurements, March 2009.
December 13, 2010

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TABLE 1 –Radiation Dose Calculations to Hotel Workers and Guests from an I-131 Cancer Therapy Patient

• 175 mCi 131I-iodide administered to a post-thyroidectomy thyroid cancer patient

• Doses calculated assuming point source*: patient self-shielding** (0.13 mrem-m2

/h-mCi); laundry no shielding (0.22 mrem-m2/h-mCi)

• Total-body effective time-activity function*: 0.95 e (0.693/0.32 day) t + 0.05 e(-0.693/7.3 day) t

• Mean distance from patient to guest in adjoining room is 2.2 m (based on mid-point of 80 inch long beds + 6 inch wall), assuming no shielding

provided by walls between rooms, and assuming head to head exposure equals mid-body to mid-body exposure

• Dose contribution of possible internal radioactive contamination is considered minor and not included

* Values used are from NRC Regulatory Guide 8.39

** Patient self-shielding value from SPARKS, R.B., SIEGEL, J.A. and WAHL, R.L. (1998). “The need for better methods to determine release criteria for 

patients administered radioactive material,” Health Phys. 75(4), 385–388.

***These assumptions and parameters should be adjusted for patient-specific situations, considering patient release instructions, to calculate realistic doses.

Assumptions and 

Parameters*** Unrealistic Highly Unlikely Conservative Realistic

Time (in days) Patient Remained in Hotel

1 2 3 1 2 3 1 2 3 1 2 3

Cohort Radiation Dose to Cohort (in mrem)

Hotel Housekeeper 69 83 91 35 43 47 14 17 18 0.90 1.1 1.2

Hotel Laundry Worker 39 47 52 16 19 21 3.9 4.7 5.2 0.078 0.095 0.10

Non-Housekeeping/NonLaundry Hotel Worker or Hotel 

Guest in Non-Adjoining Room

30 36 39 20 24 26 10 12 13 0.83 0.99 1.1

Hotel Guest in Room Adjoining 

that of Patient 54 65 71 40 48 53 26 32 34 17 21 22

Parameters

Remaining activity in patient 

excreted into bed linens at 

midpoint of each day

50% per day 20% per day 5% per day

0.1% per day 

(bath linens & 

cleaning only)

Time hotel housekeeper and 

laundry worker each hold 

contaminated linens (0.3 m away)

30 minutes per day 20 minutes per day 10 minutes per day 10 minutes per day

Time hotel housekeeper, other 

workers (except laundry), and 

other guests are 1 meter from 

patient

3 hours per day 2 hours per day 1 hour per day 5 minutes per day

Additional time patient and other 

hotel guest in adjoining room are 

both in their respective beds

12 hours per day 10 hours per day 8 hours per day 8 hours per day
December 13, 2010

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TABLE 2 – Radiation Dose Calculations to Hotel Workers and Guests from an I-131 Hyperthyroid Patient

• 29.9 mCi 131I-iodide administered to a hyperthyroid patient

• Doses calculated assuming point source*: patient self-shielding** (0.13 mrem-m2

/h-mCi); laundry no shielding (0.22 mrem-m2/h-mCi)

• Total-body effective time-activity function*: 0.20 e (0.693/0.32 day) t + 0.80 e(-0.693/5.2 day) t 

• Mean distance from patient to guest in adjoining room is 2.2 m (based on mid-point of 80 inch long beds + 6 inch wall), assuming no shielding 

provided by walls between rooms, and assuming head to head exposure equals mid-body to mid-body exposure

• Dose contribution of possible internal radioactive contamination is considered minor and not included

* Values used are from NRC Regulatory Guide 8.39

** Patient self-shielding value from SPARKS, R.B., SIEGEL, J.A. and WAHL, R.L. (1998). “The need for better methods to determine release criteria for 

patients administered radioactive material,” Health Phys. 75(4), 385–388.

***These assumptions and parameters should be adjusted for patient-specific situations, considering patient release instructions, to calculate realistic doses.

Assumptions and 

Parameters*** Unrealistic Highly Unlikely Conservative Realistic

Time (in days) Patient Remained in Hotel

1 2 3 1 2 3 1 2 3 1 2 3

Cohort Radiation Dose to Cohort (in mrem)

Hotel Housekeeper 25 44 61 12 22 31 4.7 8.5 12 0.30 0.54 0.74

Hotel Laundry Worker 15 27 37 5.9 11 15 1.5 2.7 3.7 0.029 0.053 0.074

Non-Housekeeping/NonLaundry Hotel Worker or Hotel 

Guest in Non-Adjoining Room

10 17 24 6.4 12 16 3.2 5.8 8.0 0.27 0.48 0.67

Hotel Guest in Room Adjoining 

that of Patient 18 32 44 13 24 33 8.5 15 21 5.6 10 14

Parameters

Remaining activity in patient 

excreted into bed linens at 

midpoint of each day

50% per day 20% per day 5% per day

0.1% per day 

(bath linens & 

cleaning only)

Time hotel housekeeper and 

laundry worker each hold 

contaminated linens (0.3 m away)

30 minutes per day 20 minutes per day 10 minutes per day 10 minutes per day

Time hotel housekeeper, other 

workers (except laundry), and 

other guests are 1 meter from 

patient

3 hours per day 2 hours per day 1 hour per day 5 minutes per day

Additional time patient and other 

hotel guest in adjoining room are 

both in their respective beds

12 hours per day 10 hours per day 8 hours per day 8 hours per day
December 13, 2010

24

Table 3 – Summary Table of Family Doses from Buchan Reference in Footnote 101