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Summary Military deployments involve a spectrum of activities that range from peacekeeping to combat. They are defined as troop movements to a land- based location outside of the continental United States that result from a Joint Chiefs of Staff/Unified Command deployment order applied for 30 or more consecutive days. In the past, deployment risk-assessment and risk- management strategies focused primarily on combat scenarios and warfare- related mission and health impacts. However, the roles of U.S. military forces have evolved and expanded. Increasingly, U.S. troops are deployed for operations other than war, including a variety of peacekeeping, humani- tarian, and nation-building missions. Thus, the U.S. Department of Defense (DOD) now promotes a unified and comprehensive force health protection plan that advocates full consideration of all potential health hazards across the deployment spectrum and throughout the deployment process. As part of mission planning, it is necessary for operational decision makers to have information on health hazards to individual soldiers and their potential impact on the options being considered for achieving the mission (i.e., the impacts on courses of action). The U.S. Army Center for Health Promotion and Preventive Medicine (USACHPPM) has developed guidance documents for assessing environmental health hazards that could be encountered during deployment. Technical Guide 248 (TG-248) pro- vides a general approach to assessing chemical, radiological, physical, and endemic disease hazards, and Technical Guide 230 (TG-230) provides specific guidance on the chemical subset of hazards. The critical compo- nent of TG-230 is the use of military exposure guidelines (MEGs). MEGs are media- and duration-specific exposure values that indicate chemical 1
2 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS concentrations in air, water, and soil at which certain adverse health effects might begin to occur in an exposed population. Documentation of how MEGs were derived for specific chemicals is provided in Reference Docu- ment 230 (RD-230). STATEMENT OF TASK The National Research Council (NRC) was asked to independently review TG-248, TG-230, and RD-230 for their scientific validity, complete- ness, and conformance to current risk-assessment practices. The NRC assigned this task to the standing Committee on Toxicology and convened the Subcommittee on Assessing Toxicological Risks to Deployed Military Personnel. The subcommittee was asked to review the Armyâs documents and to identify deficiencies and make recommendations for improvements. The subcommittee was asked to focus specifically on the following issues: 1. The Armyâs risk assessment, hazard-ranking, and risk-management processes described in TG-230 and its supporting documents. 2. The use of pre-existing exposure guidelines developed by the NRC and other agencies and organizations and the hierarchical scheme used by the Army in selecting from those various guidelines. 3. The Armyâs approaches to deriving MEGs for criteria pollutants, lead, soil contaminants, and other chemical contaminants. 4. Technical aspects of the Armyâs risk-management framework (as presented in TG-248) regarding competing health risks from different chemicals. 5. The assumption that the military population includes susceptible subpopulations (e.g., personnel with unknown health conditions, asthma, undetected pregnancies in the first trimester) and the use of uncertainty factors in the derivation of MEGs. 6. The adjustments of exposure guideline values to account for differ- ences in exposure durations in the derivation of MEGs. 7. The exposure assumptions and mathematic models used for the derivation of MEGs for air, water, and soil contaminants. 8. Technical aspects of the Armyâs acceptable cancer risk level of 1 in 10,000. 9. The balance of emphasis between health effects that are produced immediately or soon after exposure and possible delayed effects (e.g., can- cer) in the derivation of MEGs for chemical warfare agents and toxic indus- trial chemicals.
SUMMARY 3 10. The use of a single risk-assessment methodology for assessing the toxicological risk from exposures to chemical warfare agents and toxic industrial chemicals rather than separate risk-assessment methodologies. 11. The assumption that the toxicity of a mixture of chemicals that have similar modes of action will be equal to the sum of the toxicities of individ- ual chemicals in the mixture. 12. The utility of TG-248, TG-230, and RD-230 for decision makers (who might not be knowledgeable about toxicology or the science behind the health risk-assessment process) who will be using MEGs in the field. THE ARMYâS PROCESS TO EVALUATE CHEMICAL HAZARDS The goals of TG-230 are to âcharacterize the level of health and mission risks associated with identified or anticipated exposures to chemicals in the deployment environmentâ (italics added) so that chemical threats can be appropriately considered in operational planning. To achieve those goals, USACHPPM incorporated a risk-assessment matrix (see Table S-1)âa standard component of military operational risk management that is used for risk categorizationâin its technical guides. This matrix is a qualitative classification tool that reflects four categories of severity in risk to a mili- tary mission and five categories of probability with regard to one or more military assets. The categories are used to characterize risk in terms of mission success. The risk-assessment matrix was incorporated into TG-248 and TG-230 to facilitate the characterization of chemical hazards on the same basis and in the same terminology as other operational hazards (e.g., climate condi- tions, terrain, enemy forces). TG-230 uses MEGs as the basis for classify- ing the chemical hazards. MEGs are estimated concentrations of hazardous chemicals in air, water, or soil above which individuals might experience certain types of health effects after an exposure of specified duration. Mea- sured or predicted concentrations of chemicals at the mission site are com- pared with the most relevant MEGs to determine the potential risks. FINDINGS Risk-Assessment, Hazard-Ranking, and Risk-Management Approaches The framework developed by USACHPPM in TG-248 and TG-230 for
4 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS TABLE S-1 Risk-Assessment Matrix Probability Frequent Likely Occasional Seldom Unlikely Severity A B C D E Catastrophic I E E H H M Critical II E H H M L Marginal III H M M L L Negligible IV M L L L L Definitions Hazard Severity Catastrophic (I): Loss of ability to accomplish the mission or mission failure. Death or perma- nent disability. Loss of major or mission-critical system or equipment. Major property (facility) damage. Severe environmental damage. Mission-critical security failure. Unacceptable collat- eral damage. Critical (II): Significantly degraded mission capability, unit readiness, or personal disability. Extensive damage to equipment or systems. Significant damage to property or the environment. Security failure. Significant collateral damage. Marginal (III): Degraded mission capability or unit readiness. Minor damage to equipment or systems, property, or the environment. Injury or illness of personnel. Negligible (IV): Little or no adverse impact on mission capability. First aid or minor medical treatment. Slight equipment or system damage, but fully functional and serviceable. Little or no property or environmental damage. Risk Levels E â Extremely high risk: Loss of ability to accomplish the mission if threats occur during mis- sion. A frequent or likely probability of catastrophic loss (IA or IB) or frequent probability of critical loss (IIA) exists. H â High risk: Significant degradation of mission capabilities in terms of the required mission standard, inability to accomplish all parts of the mission, or inability to complete the mission to standard if threats occur during the mission. Occasional to seldom probability of catastrophic loss (IC or ID) exists. A likely to occasional probability exists of a critical loss (IIB or IIC) oc- curring. Frequent probability of marginal losses (IIIA) exists. M â Moderate risk: Expected degraded mission capabilities in terms of the required mission standard will have a reduced mission capability if threats occur during mission. An unlikely probability of catastrophic loss (IE) exists. The probability of a critical loss is seldom (IID). Marginal losses occur with a likely or occasional probability (IIIB or IIIC). A frequent probabil- ity of negligible (IVA) losses exists. L â Low risk: Expected losses have little or no impact on accomplishing the mission. The prob- ability of critical loss is unlikely (IIE), while that of marginal loss is seldom (IIID) or unlikely (IIIE). The probability of a negligible loss is likely or less (IVB through IVE). Hazard Probability Frequent (A): Occurs very often, continuously experienced. Likely (B): Occurs several times. Occasional (C): Occurs sporadically. Seldom (D): Remotely possible; could occur at some time. Unlikely (E): Can assume will not occur, but not impossible. Unit Status Black: Unit requires reconstitution. Unit below 50% strength. Red: Combat ineffective. Unit at 50-69% strength. Amber: Mission capable, with minor deficiencies. Unit at 70-84% strength. Green: Mission capable. Unit at 85% strength or better. Source: TG-230 and U.S. Army Field Manual 3-100.12.
SUMMARY 5 assessing health and mission risks during deployment clearly attempts to ad- dress the recommendations made by DOD and past reports of the NRC and Institute of Medicine for developing a process that would incorporate consider- ation of all potential health hazards into operational decision making more thoroughly than was done in the past. The incorporation of the risk-assessment matrix into the guidance is essential because it builds health risk assessment into a process that is routinely used and is well understood throughout the military establishment. However, the subcommittee found that USACHPPMâs approach of using one set of chemical exposure guidelines (the MEGs) was inadequate for achieving the two goals of assessing mission risks and providing force health protection. Table S-2 shows that the parameters for achieving those goals are different, which makes it extremely difficult for one set of guidance values to address both goals adequately. MEGs were determined from pre-existing exposure guidelines designed to provide a reasonable assurance of safety by considering a diverse set of protec- tive assumptions and addressing uncertainties conservatively. Thus, MEGs are appropriate (with some modification) for the goal of providing force health protection. However, for the assessment of chemical risks to missions, the goal is to provide an estimate of unit status (e.g., mission capable, combat ineffec- tive, unit requires reconstitution) in the event of an exposure. Assessment of those hazards requires an understanding of casualty estimatesâwhen soldiersâ health and performance might be degraded to the extent that the mission is jeopardized. MEGs are inappropriate for making this type of assessment be- cause they are estimates of concentration thresholds below which no adverse health effects are expected to occur, not estimates of concentrations at which mission-relevant casualties would occur. Thus, the MEG threshold concentra- tions are lower (perhaps even several orders of magnitude lower) than those at which mission-relevant casualties would be expected. For that reason, mission risk levels characterized on the basis of MEGs are not comparable to the risk levels assigned to other kinds of military operational hazards and could lead to overestimating the risk that chemicals pose to the mission. A second set of chemical exposure guidelines for mission-relevant casualty prediction is needed for the assessment of mission risks. How USACHPPM might develop another set of exposure guidelines to use in parallel with the MEGs is discussed later in this summary. Use of Pre-Existing Exposure Guidelines MEGs were developed by USACHPPM for contaminants in air, water, and soil. They were derived by reviewing guidelines and health-based criteria or
6 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS TABLE S-2 Characteristics Associated with the Major Goals of TG-248 and TG-230 Health Risk Assessment Mission Risk Assessment Goal To assess impacts on indi- To predict impacts of health vidual soldier health; risks on the mission; requires requires the use of protective the use of predictive casualty exposure values estimates Effects Short- and long-term effects Primarily short-term effects Length of exposure Long-term exposure Short-term exposure Situation More like More like short-term occupational/environmental emergency planning (OSHA, EPA) Availability of data More likely to have data More qualitative assessment available to assess exposure of exposure; relies more on subjective judgment Availability of time More time to assess Decisions must be made quickly Exposure assessment Assess proportion likely to Assess proportion likely to receive exposure in excess of receive any mission-compro- MEGs mising level of exposure Number of chemicals Many of concern Limited number of concern Likelihood that Lower Higher effect(s) will occur Confidence in Higher Lower estimated exposure(s) standards from other agencies (e.g., the U.S. Environmental Protection Agency [EPA], the American Conference of Governmental Industrial Hy- gienists [ACGIH]), selecting the most relevant guidelines on the basis of a hierarchical scheme, and modifying the chosen guidelines for military use. The drawback of this approach is that the existing guidelines were designed to protect various populations that differ from deployed troops (e.g., the general population, workers) and were intended for different settings (e.g., ambient exposures, workplace, accidental releases), which made it neces- sary for USACHPPM to adjust the values to make them relevant to the deployment setting. The subcommittee found the application of these ad- justments was not sufficient to ensure that the resulting values provide comparable levels of protection among various chemicals. In addition, the
SUMMARY 7 scientific basis of the MEGs was dependent on the data and methodology that were available when the existing guidelines were developed. These limitations are illustrated in the evaluation of the three chemical categories the Army specified for particular considerationâcriteria air pollutants, lead, and soil contaminants. â¢ Criteria air pollutants. Criteria air pollutants were an important consideration for USACHPPM because they are ubiquitous and capable of causing adverse health effects in certain individuals at high ambient levels. In evaluating the long-term MEGs for those pollutants, the subcommittee found that the rationales for selecting one organizationâs guideline over another were questionable. In addition, adjustments intended to make the guideline relevant for military purposes were not applied consistently. For example, EPAâs national ambient air quality standards (NAAQS) were used to derive a long-term MEG for carbon monoxide. The NAAQS for carbon monoxide was set to protect angina patients who exercise. No adjustments were made to account for the lack of such patients among the deployed military population. In another case, an occupational standard for sulfur dioxide was used and adjusted to derive a MEG. The resulting value was lower than the NAAQS for sulfur dioxide, which were designed by EPA to protect children and individuals with pre-existing lung disease. Establish- ing a MEG lower than the NAAQS requires some justification. â¢ Lead. For lead, the subcommittee discovered an error in the drink- ing water MEGâthe World Health Organizationâs drinking water criterion, used as the basis for the MEG, was reported incorrectly by USACHPPM as 0.05 mg/L instead of 0.01 mg/L. The derivation of the soil MEG for lead also requires reanalysis, because the selected target blood lead concentration is not protective of the embryo and fetus. In contrast, many exposure as- sumptions used in the adult blood level model are overly conservative. â¢ Soil contaminants. For soil contaminants, the subcommittee iden- tified a number of concerns, including the use of older data or assumptions that have been recently updated or have been superceded by new guidance; failure to develop MEGs for volatile chemicals; flaws in the description of how dermal toxicity values are derived; and the use of a high and uncertain soil ingestion rate. In addition, soil MEGs were only established for 1-year exposures, and the subcommittee is not convinced that short-term soil MEGs are unnecessary. There are certain chemicals, such as volatile chlori- nated solvents, for which short-term soil MEGs would be appropriate to protect troops in trenches or in tents above contaminated soil.
8 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS Adjustments for Military Application In developing TG-230 and MEGs, it was necessary for USACHPPM to make assumptions about the composition of its forces, to factor in deploy- ment exposure conditions, and to select an acceptable lifetime cancer risk. Population Considerations USACHPPM considered demographic and health differences between deployed populations and the general public that might contribute to differ- ences in susceptibilities to environmental exposures. For the general public, susceptible subpopulations typically include embryos and fetuses, the very young, the elderly, individuals with pre-existing disease, and those with genetic susceptibilities. In establishing health-protective exposure values, uncertainty factors are conventionally applied to provide a margin of safety to protect the portion of the general population that might be at increased risk. In some cases, such as the NAAQS noted above, values were based on data from a susceptible subpopulation. According to the demographic information provided to the subcommit- tee, with the exception of genetic susceptibilities, deployed military person- nel include few individuals in the traditional categories of increased suscep- tibility relative to the general population. Deployed personnel span a nar- rower age range and are subject to physical requirements that should ensure that they are in better health or do not have pre-existing medical conditions that might interfere with their ability to serve during a deployment. Al- though TG-230 identifies asthmatic individuals as a subgroup that might be more susceptible to certain contaminants, it appears to the subcommittee that documentation and procedures are in place that would prevent or limit the deployment of asthmatic personnel, especially those with moderate or severe disease. Thus, the subcommittee concludes that the deployed forces should be considered healthier than the general public. On the other hand, it is reasonable to assume that the deployed military population might have a level of genetic susceptibilities similar to that found in the general popula- tion. TG-230 indicates that although women known to be pregnant are ex- cluded from deployment, there could be cases where a pregnancy is discov- ered only after deployment. In such situations, it is possible for exposures to occur during critical stages of embryo and fetal development before pregnant women have been removed from the deployment scenario. In
SUMMARY 9 addition, some chemicals could persist in the body after deployment and have a potential to affect post-deployment pregnancies. Thus, it is impor- tant that MEGs be protective against developmental effects. However, it was unclear to the subcommittee whether all of the chemicals had been screened for developmental effects. For example, some of the extant mili- tary exposure guidelines (such as the militaryâs continuous exposure guid- ance levels) are set on the basis of an assumption that only men would be exposed, so developmental effects were not considered. Exposure Adjustments USACHPPM had to adjust existing guidelines set by regulatory and other agencies for application in the military context. Key adjustments were made for exposure rates and differences in military population characteris- tics compared with the general population. For example, the activity level of deployed troops is much higher than that of the general population, such that breathing and water-consumption rates of military personnel are much higher. To account for exposure differences, simple mathematic adjust- ments were used. The subcommittee found that USACHPPM provided adequate justification for performing those exposure adjustments but ap- pears to have applied them inconsistently in some cases. For example, the inhalation adjustment factor appears to have been used in setting some, but not all, of the 14-day air MEGs. Cancer Risk The Army posed the question of whether a cancer risk of 1 in 10,000 is acceptable for establishing MEGs for carcinogens. The identification of an acceptable cancer risk level has been debated for many years. It is essen- tially a risk-management policy decision, because the selection of an ac- ceptable risk is a question of societal norms and values. Consequently, science does not directly provide an answer to the question. The subcom- mittee concluded that it would be inappropriate for it to make a judgment about how much risk the military should accept. However, the subcommit- tee decided it could help address that issue by reviewing acceptable risk levels selected by other organizations and making observations about where the Armyâs acceptable cancer risk threshold lies in comparison. The sub- committee found that risk of 1 in 10,000 falls within the range used by other
10 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL THREATS federal agencies for occupational and environmental exposures, and is sufficiently conservative to be protective for individual soldiers in the event of multiple deployments. Immediate and Delayed Health Effects The subcommittee was asked to evaluate whether appropriate consider- ation was given to immediate and delayed health effects. It was clear that USACHPPM considered long-term health consequences along with short- term effects during the development of the chemical hazard ranking scheme for mission risk assessment. However, the subcommittee found that a more formalized procedure for communicating long-term and delayed health effects simultaneously with mission risk information is needed to ensure that those potential effects are explicitly considered. In addition, the discus- sion of delayed effects highlights cancer, and places inadequate emphasis on other chronic or delayed effects (e.g., compromised immune function, infertility). Use of a Common Risk-Assessment Methodology One of the questions posed to the subcommittee was whether chemical warfare agents should be evaluated differently from toxic industrial chem- icals. The subcommittee found no reason not to apply the same risk-assess- ment methodology to those two categories of chemicals. Chemicals will have to be evaluated on a case-by-case basis, but the risk-assessment approach to evaluating them can and should be conceptually similar. Exposure Assessment MEGs are designed to be compared with measured or modeled concen- trations in the field. The subcommittee was informed that intelligence information on potential sources of chemical hazards is generally available for making predeployment risk assessments and that procedures are in place for conducting environmental sampling during deployments. However, no references are provided in TG-248 or TG-230 to documentation on how such information is to be collected and assessed. It seems appropriate that risk analysts and preventive-medicine personnel would be involved, to
SUMMARY 11 some extent, in developing exposure-assessment plans; therefore, it would be helpful if exposure-assessment guidance was compiled from existing sources and incorporated into or at least linked with TG-230 to support those personnel. The guidance should include information on exposure monitoring and modeling and on developing a sampling plan. Cumulative Risk Cumulative risk is the likelihood of occurrence of an adverse health effect resulting from exposure to multiple chemicals that have common modes of toxicity from all routes and pathways. Assessing cumulative risk is a complex task that requires assessing whether the toxic effects of chemi- cals found in a mixture produce their effects independently or produce additive, synergistic, or antagonistic effects. TG-230 assumes that total toxicity from chemicals in a mixture of toxicants with similar modes of action is equal to the sum of the weighted dose toxicities of the individual chemicals. Although that generally is accepted practice, no guidance was provided on how the cumulative risks were to be assessed other than by a qualitative notation. The subcommittee examined a number of chemicals in TG-230 that have effects that would at least summate with one another, but found that it was impossible to identify that type of potential additive action from the descriptions of symptoms and target organs provided in RD- 230. As a first step toward improving the assessment of cumulative risks, it might be practical to establish a qualitative classification scheme that identifies chemicals known to interact or cause similar effects and that might be encountered simultaneously during a deployment. Then USACH- PPM can consider incorporating quantitative approaches. Utility for Decision Makers The subcommittee was asked to consider whether the technical guides could be used by personnel who are not knowledgeable about toxicology or risk assessment. Although the technical guides provide a procedure that is intended to facilitate the consistent evaluation and interpretation of chemi- cal threats that might be encountered during deployment, the subcommittee found that professional judgment of trained personnel is necessary to use the guides properly and to effectively communicate risks to nontechnical decision makers. Another element of the task question is whether the prod-
12 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL THREATS ucts of TG-230 will be understood by decision makers so they can properly consider risks to the mission and to force health. As noted earlier, the cur- rent set of exposure guidance does not allow for adequate characterization of mission risks and will, therefore, lead to decisions based on inappropriate comparisons between chemical risks and other operational risks. RECOMMENDATIONS Use Two Sets of Exposure Guidelines The subcommittee recommends that two sets of chemical exposure values be used to assess health risks and mission risks separately. This will ensure that the guideline values are based on health considerations appropri- ate to the intended goal. Below, the subcommittee outlines how the two sets of guidelines should be derived and applied in the operational risk- management process. Exposure Guidelines for Assessing Mission Risks One goal of TG-248 and TG-230 is to characterize the levels of mission risk posed by chemicals for comparison with other operational risks. To address this goal, the subcommittee recommends the Army develop a new set of chemical exposure guidelines that provide predictive estimates of mission-relevant casualties in the event of an exposure during a mission. Such values, termed chemical casualty estimating guidelines (CCEGs) by the subcommittee, would be defined as media- and duration-specific chemi- cal concentrations expected to cause health impairments that degrade the performance of enough individuals to reduce unit strength. CCEGs should not be established from existing health-protective exposure standards, but should be derived by conducting independent evaluations of each chemical of interest and developing exposure-response and population-response data on which to base casualty estimations. Using casualty estimates (rather than health protective estimates) in conjunction with the operational risk-assess- ment matrix will provide risk-level characterizations more appropriate for comparison with other anticipated risks as well as with other chemical hazards. The following are important elements to consider in developing CCEGs: â¢ A methodology should be developed to derive CCEGs that provide
SUMMARY 13 predictive, probabilistic exposure-response information that would enable decision makers to weigh chemical threats in comparison to other mission threats as well as to other chemical hazards. CCEGs ideally would be deter- mined by modeling chemical-specific data to predict effects on unit strength at various exposure levels (e.g., probit analysis, which provides a graphic representation of a dose-response relationship in the ranges where effects are observed). â¢ CCEGs should be established for chemicals that have some finite probability of being encountered in sufficient quantities to degrade a mis- sion. â¢ CCEGs should be derived primarily for air contaminants, because inhalation is the exposure route most likely to result in incapacitation. However, there are some situations for which oral and dermal CCEGs might be necessary, such as specialized operation activities that involve exposure to contaminated water (e.g., water immersion activities). â¢ Assistance should be solicited from other agencies and organiza- tions working on health-related guidelines. Many existing exposure guide- lines (especially EPAâs acute exposure guideline levels) make key informa- tion readily available. Future working relationships between the DOD and other agencies routinely developing exposure guidelines might make the development of CCEGs more resource-effective. â¢ The methodology for deriving CCEGs and the derivation of the CCEGs themselves should be peer-reviewed. â¢ If the Army chooses to use MEGs in the interim, TG-230 should be revised to warn users regarding the deficiencies and limitations of MEGs when applied to assess mission-related performance risks. Exposure Guidelines for Assessing Health Risks Another goal of TG-248 and TG-230 is to provide force health protec- tion across a range of scenarios that might be encountered during deploy- ment, recognizing that some health risks might have to be accepted to achieve military objectives. The subcommittee found that the MEGs are conceptually appropriate for addressing health threats in terms of force health protection. However, the procedures for developing MEGs outlined in RD-230 require some modification to make the MEGs more relevant to deployment situations and more consistently protective. In addition, guid- ance should be added to TG-230 on how to apply and interpret the MEGs. The following are important elements to consider in addressing this recom- mendation:
14 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL THREATS â¢ Ideally, USACHPPM would benefit from developing an independ- ent set of principles and procedures to develop MEGs from the available toxicology data on individual chemicals. Those procedures would solidify the purpose of the MEGs and would make explicit the risk-management policy decisions that underlie the selection of studies and use of uncertainty factors that might be different from those used by other agencies. However, the subcommittee recognizes the immensity of such an undertaking and therefore suggests that revisions be conducted in a prioritized manner. Below is a general description of the types of revisions needed. Specific examples and recommendations are provided in Chapter 5 of the report. â Near-term revisions. These are revisions to improve the qual- ity of the MEGs that require relatively modest resources. They include revising the MEGs with updated values from other organizations, en- suring consistent use of uncertainty factors and adjustments relevant to the deployed population, ensuring that the MEGs are not based on data from subpopulations not expected to be among the deployed forces (e.g., asthmatics, children), and improving the documentation and use of the most relevant toxicity end points and uncertainty factors in set- ting the existing exposure guidelines. â Mid-term revisions. Revisions in this category would result in more internally consistent MEGs that are relevant to deployed popula- tions. Such revisions would involve using original source material (e.g., the critical paper selected by EPA for a reference concentration) to calculate MEGs. MEGs should also be reviewed to assess whether they protect against developmental effects. â Long-term revisions. These include developing more rigorous procedures for determining MEGs and performing the analyses. The po- tential for collaboration with other agencies that are developing exposure guidelines should be explored. For example, EPA is beginning a major effort to update its Integrated Risk Information System. It might be possi- ble to work with other agencies to establish deployment-relevant guide- lines. â¢ USACHPPM should develop a risk-management framework that focuses on what action plans (i.e., responses) are appropriate when MEGs are exceeded. Possible responses would include considering risk-manage- ment options for reducing or eliminating risks (e.g., using protective gear, moving deployed personnel to an uncontaminated area, treating water) and determining the appropriate medical follow-up (e.g., documenting the expo-
SUMMARY 15 sure in medical records, tracking exposed individuals, providing long-term care) when military personnel must bear health risks. Communication of Mission and Health Risks Because some of the decisions that must be made with the guidance of TG-230 require subjective evaluation, it is important that personnel using the guides include individuals with training in preventive medicine, toxicol- ogy, and risk assessment. Trained personnel should conduct separate analy- ses of health and mission risks. The resulting evaluations should be pro- vided to decision makers simultaneously and consideration should be given to the risk-management options available for reducing or eliminating the risks. This will help decision makers explicitly balance the competing health and mission risks with respect to the military objective. It also will help to ensure that any risk trade-offs that involve accepting some health risks to deployed personnel are recognized and that appropriate medical attention, surveillance, and follow-up are provided.