An Evaluation of Radiation Exposure Guidance for Military Operations: Interim Report (1997)

During the Cold War, the United States Army established radiation dose limits and controls for soldiers based on a scenario of global nuclear war (NATO, 1986; HQDA, 1994). Battlefields were expected to be heavily contaminated. Radiation protection standards and controls for soldiers were based on criteria that maximized immediate survival and the ability to continue the combat mission. The upper bounds of the dose limits were at the threshold for development of radiation sickness.

In the post Cold War setting, military scenarios involving radioactive contamination rarely reflect global nuclear war, but more often consider limited nuclear exchanges, terrorist actions using improvised nuclear devices, conventional explosives employed as a means of disseminating radioactive materials, or nuclear power plant accidents. In these scenarios, radioactive contamination would be more restricted geographically and the immediate risk to the health of a soldier might be much lower. Except under very rare circumstances, radiation doses under this scenario would be well below the lethal level, yet they could be above occupational dose limits that are applied to civilian workers (CFR, 1991).

The Supreme Headquarters, Allied Powers Europe (SHAPE) of the North Atlantic Treaty Organization (NATO) recognized a need to plan for potential radiation exposure of military forces in Europe during the peacekeeping mission to Bosnia. In response, SHAPE staff developed the Allied Command Europe (ACE) Directive Number 80-63, ACE Policy for Defensive Measures against Low Level Radiological Hazards during Military Operations. For convenience, we refer to this document as the ACE Directive. This embodiment of NATO's guidance for the protection of its military forces from radiation is the subject of this report.

At the request of the U.S. Army Surgeon General, the Institute of Medicine has convened an expert committee to evaluate these guidelines from scientific and ethical perspectives. This report, Part I of this committee's efforts, focuses on the scientific merit of the current NATO guidance by responding to the three-part charge:

1. Do the presently proposed NATO guidelines (dose limits, documentation, and control measures) follow generally accepted U.S. national limits and recommended guidelines for radiation protection of occupational and emergency workers?
2. Are these NATO guidelines reasonable from a scientific viewpoint?
3. How could the guidelines be improved?

The committee will report next year, in Part II, its follow-on deliberations on other critical factors, including ethics, risk perception, record keeping, training, communication, and decision making, with additional scientific information as necessary. The Army requested that the committee complete its technical review of the ACE Directive as quickly as possible, concentrating on the broader issues of ethics and law in the second year of the study. The technical recommendations we now present do not yet include these extremely important considerations.

Not surprisingly, however, we found each technical point to be associated with numerous considerations that involve societal, organizational, and personal values. The committee will spend its next year of research and deliberation in providing the Army Surgeon General with cogent and practical guidance that includes and reflects this broader philosophical context. Because of this, the current review must be considered a work in progress; it will not be complete until the final report adds the broader perspective.

In answering its charge, the committee reviews the basic principles of radiation physics and radiobiology and presents an overview of current practices in radiation protection in the civilian sector and in the Army. From this basis the committee comments on the technical aspects of the NATO guidance and makes several recommendations.

This report is about radiation protection, the aims of which are (a) to prevent the occurrence of acute health effects (e.g., cataracts in the eyes and radiation sickness) and (b) to ensure that all reasonable steps are taken to reduce the induction of potential long-term effects (e.g., cancer) to a level that is acceptable to society (ICRP, 1991a).¹ To achieve these aims, radiation doses to individuals and populations must be measured and controlled. These doses (related to the amount of radiation energy deposited in tissue per unit of mass) typically are

expressed in the international units millisievert (mSv) or milligray (mGy),² or in the traditional units, the rem and rad, respectively.

Radiation doses that exceed a minimum (threshold) level can cause undesirable effects such as depression of the blood cell-forming process (threshold dose = 500 mSv, 50 rem) or cataracts (threshold dose = 5,000 mSv, 500 rem). The scope and severity of these effects increases as the dose increases above the corresponding threshold. Radiation also can cause an increase in the incidence, but not the severity, of malignant disease (e.g., cancer). For this type of effect, it is the probability of occurrence that increases with dose rather than the severity. For radiation protection purposes it is assumed that any dose above zero can increase the risk of radiation-induced cancer (i.e., that there is no threshold). Epidemiologic studies have found that the estimated lifetime risk of dying from cancer is greater by about 0.004% per mSv (0.04% per rem) of radiation dose to the whole body (NRC, 1990).

Radioactive sources can expose the body from outside (external doses, e.g., when a diagnostic x ray is taken), or from inside (internal doses, e.g., when radioactive materials are inhaled, ingested, or enter through wounds). Gamma and x-ray radiations (and, to a lesser extent, beta radiation) are the primary contributors to external doses. Alpha and beta radiations are much more important contributors to internal doses.

Control measures to reduce or limit exposure to radiation must consider the circumstances and environment of the exposure. In discussing the influence of scenario on radiation controls, we use the ICRP (1991a, 1993) nomenclature—''intervention'' and "practice." A practice is an intentional activity in which the practitioner is routinely at risk of radiation exposure (e.g., the duties of x-ray technicians in hospitals and nuclear power plant workers). An intervention, by contrast, is an action taken to reduce radiation exposure, often by responding to an accident (e.g., the actions of firefighters who responded to the Chernobyl accident). A practice is characterized by well-defined radiation sources and work procedures; an intervention, by great uncertainty in both.

The Army has previously published guidance for control of doses from routine occupational exposures to radiation and from those associated with nuclear war. The ACE Directive is an encouraging step in developing control measures for other situations. We realize that the Directive was meant for a specific mission (Bosnia) and that the Army recognizes its limitations. The improvements recommended by the committee should be viewed as constructive and in no way diminish the significant progress that the Army has made toward the control of the complete spectrum of radiation hazards on the battlefield and in nonwartime situations. While the ACE Directive is useful as a basis for establishing guidelines to protect soldiers from the adverse effects of radiation, the committee recommends that it be revised to assure completeness and clarity.

The committee recommends that the Army:

• 1.

  Provide soldiers the same level of radiation protection as civilians working in similar environments. The ACE Directive appears to manage all military missions involving radiation exposures as interventions. While this is clearly appropriate for many missions (e.g., emergencies, radiation accidents, and operations involving hostile action), other missions can more properly be treated as routine practices, thereby affording more complete control of the radiation exposure. Missions amenable to control as practices might include security details, decontamination of vehicles, and other scenarios in which hostile action is not expected.

• 2.

  Develop and state an explicit radiation protection philosophy that defines missions as falling under the framework of either a practice or an intervention. Practices would be subject to modified requirements of the Army's existing occupational radiation protection program. It is likely that the situation in Bosnia would fall into this category. Under the committee's recommendations, soldiers would be considered radiation workers if they were assigned military duties that have the potential for radiation exposures that could result in doses in excess of the International Commission on Radiological Protection limits for the public (ICRP, 1991a)—1 mSv per year. A revision of the existing exposure guidance in the ACE Directive would govern those situations that are of an emergency nature and would be managed as interventions. In both cases, keeping doses as low as reasonably achievable would still be of primary importance.

• 3.

  Clearly state in the policy paragraph of the subsequent versions of the ACE Directive the definitions adopted for practices and interventions in the necessary military context. The procedures that follow the policy statement should address practice and intervention separately. It would seem reasonable for the commander to have the authority to determine which of these frameworks to follow based upon the military mission.

The committee recommends that the Army:

• 4.

  Not use the term low level to describe the radiation dose range of 50–700 milligray (mGy) (5–70 rad). Low level may be an appropriate descriptor when comparing these doses to those that may be experienced from the detonation a nuclear weapon. In the broader context of radiation protection, however, low level clearly implies much lower doses.

• 5.	Use terms other than no risk and normal risk for the risk state categories labeled RES 0 and RES 1A in the table of exposure guidance in Annex A of the ACE Directive. To describe any nonzero dose as no risk is incon-

• sistent with current international positions on the effects of radiation. Likewise, the term normal risk incorrectly implies no additional risk to that from natural background radiation exposure, even though such exposures are considered to contribute very small, possibly negligible, health risks.

• 6.	Avoid the term radiological hazard when describing the exposure of soldiers to radiation, unless the hazard refers to a specific detrimental effect. For most cases in the ACE Directive radiological hazard simply means radiation.

The committee recommends that the Army:

• 7.

  Develop requirements for measuring, interpreting, and responding to airborne and surface contamination (particularly that containing alpha and beta emitters). Guidance should define levels of alpha and beta contamination that would trigger use of protective equipment and actions. The ACE Directive gives only cursory consideration to this topic and the terminology used to describe the instrumentation necessary for the detection and measurement of radioactive contamination is not clear.

• 8.

  Reconsider its absolute requirement that soldiers wear protective equipment within an exclusion zone as defined in the ACE Directive . The decision to use protective equipment should be based on the potential for personal contamination with radioactive materials, externally or internally. To require respiratory protection regardless of the existence of an airborne hazard may be counterproductive to completing the mission in a timely and effective manner.

• 9.

  Make a clear distinction between military intelligence estimates and radiation risk estimates. It is unclear, in the Intelligence procedures section (NATO, 1996, §1-3.a.), whether risk (high or low) refers to (a) intelligence assessments of the likelihood of radiation contamination or (b) the magnitude of measurable levels of radiation contamination.

• 10.

  Develop explicit requirements to define when individual radiation monitoring is required in the field. The guidance on whether a soldier could enter a low-level contaminated area without individual dose monitoring is vague. It would be reasonable to require individual dosimetry for all incursions into an exclusion zone where radioactive contamination is likely.

The committee recommends that the Army:

• 11.

  Review its dosimetry capabilities and determine if they are adequate to support the use of the Operational Exposure Guidance in the ACE Directive. In order to manage soldier exposures according to the ACE Directive, all soldiers would have to have dosimeters that can measure doses as low as 0.5 mGy (0.05 rad).

• 12.

  Increase specificity of the dosimetry program guidelines in subsequent versions of the Directive (e.g., provide specific guidance on the capabilities of monitoring devices and equipment). The committee considers radiological monitoring and dose estimation for individuals, outside the occupational environment, as areas that require significant attention by the Army.

• 13.

  Not assume, as the ACE Directive does, that internal doses will be zero because respiratory protection will be used. Soldiers may receive an internal dose from inhaling or ingesting radionuclides. This may occur if they are unaware of airborne contamination and are not wearing protective equipment or if the equipment fails or is used improperly.

• 14.

  Review its capability to measure airborne radioactive contamination. The ability to measure airborne radioactivity and respond accordingly is essential to an adequate radiation protection program. The lack of exposure information for airborne hazards has proven a problem for veterans of the atmospheric nuclear test program. More recently, potential chemical exposures during the Persian Gulf War at Kamisiyah, Iraq (DoD, 1996; Schaeffer, 1996) have demonstrated how a lack of airborne exposure data creates problems with health assessment activities.

• 15.

  Expand Operational Exposure Guidance to include radiation doses from both internal and external sources of radiation. These should be expressed in terms of effective dose and be consistent with the requirements of the U.S. Nuclear Regulatory Commission. The lack of consideration of internal dose is a major shortcoming in the ACE Directive.

• 16

  Adopt the millisievert (mSv) as the standard unit of effective dose and milligray (mGy) as the unit of absorbed dose. There are three reasons for this recommendation. First, the units currently used in the ACE Directive—centigrays (cGy) and centisieverts (cSv)—are not internationally accepted scientific units. Second, by using millisieverts, all doses to individuals could be compared to one year's nominal U.S. background dose from external sources (1 millisievert). This should make it easier for soldiers to understand their exposures.3 Third, at low radiation levels, the use of the unit millisievert will reduce, albeit

• only slightly, the problems of recording doses that are much less than one and are expressed to several decimal places.

• 17.	Clearly define the time over which doses are to be accumulated for assignment of radiation exposure status (RES) levels in the Operational Exposure Guidance in Annex A of the Directive. Presumably, doses are cumulative over a career and are not reset to zero after each operation.

• 18.

  Review and revise doctrine and procedures on dosimetry to ensure individual doses are monitored and recorded for all soldiers exposed to radiation, whether from routine occupational exposure or as a consequence of uniquely military missions. While the ACE Directive requires that records of individual dose be maintained, existing Army guidance (HQDA, 1994) requires tracking only of unit doses (e.g., average doses for a platoon).

The committee recommends that the Army:

• 19.

  Include radiation doses from internal sources (e.g., from inhaled airborne radioactivity) in applying reference levels in Operational Exposure Guidance. The reference levels shown in the Operational Exposure Guidance table (Annex A) appear at least as stringent as those found in current civilian radiation protection recommendations of expert national and international advisory bodies. However, the ACE Directive misapplies the levels by assuming there will be no internal doses.

• 20.

  Clearly specify what actions are recommended at each reference level in the Operational Exposure Guidance. Although the reference levels in the Directive are generally appropriate, the actions recommended at each level lack specificity. Future versions of the Directive or its implementing instructions should specify the details of each action (e.g., when to initiate a monitoring program and what its specific requirements are).

• 21.

  Restructure the table of Operational Exposure Guidance to account for the uncertainty of dose estimates in interventions. Because of this uncertainty, the two lowest dose categories in the existing guidance are too narrow to be scientifically justified (in the environment of an intervention) and should be combined.

• 22.

  Develop separate Operational Exposure Guidance for managing practices (routine tasks involving radiation exposure) in the context of a military operation. If the Army adopts the philosophy that soldiers should receive the same level of protection as civilian radiation workers in similar environments and circumstances, the guidance in Annex A should be expanded to include dose limits and reference levels appropriate for a practice as well as an intervention.

In summary, the committee views the ACE Directive as a positive step in providing the soldier with protection against the potential adverse effects of ionizing radiation across the spectrum of radiation sources that may be encountered in military operations. In this first part of our study, we have reviewed the adverse effects attributed to radiation exposure and described methods to avoid them. Additionally, we have compared the ACE Directive with prevailing international and national philosophies of radiation protection and the existing Army framework for radiation safety.

We found that the ACE Directive is incomplete in scope and unclear in certain areas. To assist the Army in improving these areas, we have developed several recommendations. Implementation of these should provide the soldier with an acceptable level of protection from adverse effects of radiation, at least from a technical standpoint. In the second part of the study, the committee will consider those factors beyond this technical realm, that is, the ethical, moral, and legal basis for a system of radiation protection applicable to the soldier in the exercise of his or her profession.