. "Summary." Review of the Army's Technical Guides on Assessing and Managing Chemical Hazards to Deployed Personnel. Washington, DC: The National Academies Press, 2004.
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Review of the Army’s Technical Guides on Assessing and Managing Chemical Hazards to Deployed Personnel
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, humanitarian, 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) provides 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 component of TG-230 is the use of military exposure guidelines (MEGs). MEGs are media- and duration-specific exposure values that indicate chemical
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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
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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 Army’s documents
and to identify deficiencies and make recommendations for improvements.
The subcommittee was asked to focus specifically on the following issues:
1. The Army’s 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 Army’s approaches to deriving MEGs for criteria pollutants,
lead, soil contaminants, and other chemical contaminants.
4. Technical aspects of the Army’s 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 Army’s 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.
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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 ARMY’S PROCESS TO EVALUATE CHEMICAL HAZARDS
The goals of TG-230 are to “characterize the level of health and mission
risks associated with identified or anticipated exposures to chemicals in the
deployment environment” (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)—a
standard component of military operational risk management that is used
for risk categorization—in 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
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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 – 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 – 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 – 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 – 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.
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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 USACHPPM’s
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 estimates—when soldiers’
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
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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
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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 consideration—criteria air pollutants, lead,
and soil contaminants.
• 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 organization’s guideline over
another were questionable. In addition, adjustments intended to make the
guideline relevant for military purposes were not applied consistently. For
example, EPA’s 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.
• Lead. For lead, the subcommittee discovered an error in the drink-
ing water MEG—the World Health Organization’s 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.
• 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.
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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
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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 military’s 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 Army’s 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
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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
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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-
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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:
• A methodology should be developed to derive CCEGs that provide
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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).
• CCEGs should be established for chemicals that have some finite
probability of being encountered in sufficient quantities to degrade a mis-
sion.
• 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).
• Assistance should be solicited from other agencies and organiza-
tions working on health-related guidelines. Many existing exposure guide-
lines (especially EPA’s 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.
• The methodology for deriving CCEGs and the derivation of the
CCEGs themselves should be peer-reviewed.
• 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:
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14 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL THREATS
• 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.
— 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.
— 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.
— 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.
• 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-
OCR for page 15
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.
