|
||||||||||||||||
|
||||||||||||||||
The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. 2
|
||||||||||||||||
 |
 |
Page 27 |
 |
 |
 |
|
| ||||||||||||||||||||||||||||||||
|
|
|||||||||||||||||||||||||||||||
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 27
2
Review of the Army’s
Technical Guidance
This chapter reviews the approach used in Technical Guide 248 (TG-
248) and Technical Guide 230 (TG-230) for assessing and characterizing
chemical hazards for deployment decision making. First, important aspects
of risk comparison that were identified in previous reports of the National
Academies are briefly revisited. Second, the adequacy of the technical
guides for providing appropriate characterizations of health and mission
risks from exposure to chemicals is evaluated.
EARLIER ACADEMIES REPORTS ON DEVELOPING
RELIABLE COMPARATIVE RISK ASSESSMENTS
FOR DEPLOYMENTS
The Institute of Medicine report Protecting Those Who Serve (IOM
2000) and the National Research Council report Strategies to Protect the
Health of Deployed U.S. Forces: Analytical Framework for Assessing Risks
(NRC 2000) provide a number of recommendations relevant to developing
a systematic process to prospectively evaluate non-battle-related risks asso-
ciated with deployment activities and settings. For example, NRC (2000)
specifically recommends that the conceptual paradigm for quantitative risk
assessment described in Risk Assessment for the Federal Government:
Managing the Process (NRC 1983) be used as a basis for developing a U.S.
27
OCR for page 28
28 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
Department of Defense (DOD) framework for assessing risks to deployed
forces. Use of that paradigm would “facilitate integration of the results of
hazard-specific assessments and tracking of the complex process of simulta-
neous consideration of multiple threats … and [would aid in] developing
risk management strategies, including trade-offs” (NRC 2000). That rec-
ommendation follows from a more detailed discussion of related issues in
which the following key points are made:
• “Troops during deployment could become exposed to a number of
threats simultaneously. Exposures that are individually tolerable without
appreciable risk might not be so when several are experienced together, and
the question of interactions among agents looms particularly large for de-
ployment risk assessment” (NRC 2000, p. 41)
• “The NRC (1983) paradigm for risk assessment … is readily adapt-
able to deployed forces protection … to analyze (1) the likelihood of the
presence of a hazard associated with a deployment; (2) the likelihood of
releases of agents into the environment; (3) the likelihood that troops will
suffer exposure (of various magnitudes), given the releases; and (4) the
likelihood that health effects will be caused among them, given the expo-
sure. … [E]fforts would be focused on how activities and practices come to
present threats, how likely it is that threats will be manifested in practice,
and how mitigating one risk might raise other risks” (NRC 2000, p. 43)
• “[R]isk analysis must be content to say what can be said and not
only to acknowledge the inevitable remaining uncertainty, but to try to
characterize that uncertainty so that appropriate perspectives on the mean-
ing and robustness of the analysis are expressed. … Characterization of
uncertainty and the limitations of available data are important to all risk
analysis, but they might play an especially important role in the analysis of
deployment threats, where high-consequence decisions might require taking
one risk to avoid others, Risk management approaches exist to help make
such decisions, but when the risks to be compared are quite uncertain, or
uncertain to different degrees, good characterizations of uncertainty is [sic]
necessary in order to arrive at sound solutions” (NRC 2000, pp. 60-61;
italics added).
• “… the establishment of ‘conservative’ estimates of dose-response
relations, that is, those designed to err on the side of safety when faced with
uncertainty about how to project expected human responses from available
data, might not be appropriate for certain military uses. When risks cannot
be avoided and decisions are made to accept some risks rather than others,
or to bear some risk in furtherance of a more fundamental military objec-
tive, it is important to make these trade-off decisions with unbiased esti-
OCR for page 29
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 29
mates of the impacts of various courses of action. In other applications,
such as the setting of health-protective exposure standards for application
in less severe circumstances, conservative estimates might be much more
acceptable. … [Analyses should be] conducted and … results presented, so
that different uses appropriate for different risk-management settings can be
made” (NRC 2000, pp. 66-67; italics added).
• “A final special aspect of risk analysis for deployment is the large
role that risk-risk comparisons must play. Given the high level of tactical
risk that might be inherent in the deployment situation, some health and
safety risks may be appropriate to avoid or mitigate even greater risks.
Determining how to optimize the trade-offs requires simultaneous consider-
ation of the spectrum of risks faced by deployed troops, along with the
possibility that actions taken to avoid or ameliorate some risks might exac-
erbate others” (NRC 2000, pp. 83-84; italics added).
• “[DOD decisions concerning deployed military personnel involve
issues including] the need to call for individual troops to put life, limb, and
health at risk in the interests of the military mission and the nation at large;
[and] problems of trading off possibilities of health effects in later life with
immediate risks of casualties and impacts on military mission of military
capabilities … If the risk analysis is to effectively contribute to such deci-
sions, it will require an articulation of a doctrine on how risk trade-offs are
to be considered. In addition, DOD should attempt to articulate a set of
principles on how the balance of long-term risks to the troops and risks to
the military mission should be approached” (NRC 2000, p. 89; italics
added).
These key points highlight the importance of using a comprehensive,
quantitative risk-assessment paradigm as the basis for a formal framework
for the integrated management of risks to deployed personnel, particularly
in view of the multiple exposures, chemicals, toxic end points, and/or
sources of uncertainty likely to be involved. The italicized portions focus
on the critical need for comparative risk analysis that would allow com-
manders to make trade-off decisions concerning uncertain risks in the con-
text of potentially competing goals, ranging from combat success to preven-
tive public or occupational health, that might differ in urgency. Such trade-
offs should reflect unbiased assessments of net risk associated with alterna-
tive courses of action (NRC 2000). The same recommendation appears in
an earlier NRC report, Science and Judgment in Risk Assessment (NRC
1994), which states that “decisions involving risk-trading or priority setting
... should take into account information on uncertainty in quantities being
ranked so as to ensure that such trades do not increase expected risk.”
OCR for page 30
30 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
THE ARMY’S RISK-ASSESSMENT GUIDANCE
FOR DEPLOYMENT
Description
Technical Guide 248 (TG-248)
TG-248 (USACHPPM 2001) outlines the processes and tools that
could be used to evaluate and communicate all categories of occupational
and environmental health (OEH) and endemic disease (ED) hazards in
accordance with the military operational risk-management (ORM) process
discussed in Chapter 1. TG-248 focuses on the first two steps of the ORM
process, identifying OEH/ED hazards and assessing the threat they pose to
the mission in terms of their probability and severity. TG-248 was designed
to enable preventive-medicine personnel to express the risks from each
OEH/ED hazard in the same metric used for other more traditional military
hazards (e.g., enemy forces, mechanical problems) as well as other OEH/
ED hazards so that decision makers can make rational comparisons of the
various risks faced during deployment and make decisions about courses of
action.
The approach used by the U.S. Army Center for Health Promotion and
Preventive Medicine (USACHPPM) is necessarily different from those used
for traditional occupational or environmental risk assessments because
military decision making must consider mission impact in addition to indi-
vidual health risk. Thus, TG-248 facilitates classification of OEH/ED haz-
ards using a standard component of military ORM—the risk-assessment
matrix (see Table 2-1). The risk-assessment matrix is a qualitative classifi-
cation scheme that reflects four categories of “severity” of risk to a military
mission and five categories of “probability” with regard to one or more
military assets and/or soldiers. These two dimensions are combined to
comprise 20 cells that are separated into four qualitative categories of
mission-related risk: extremely high, high, moderate, and low. These risk
categories pertain specifically to the qualitative likelihood of mission suc-
cess, which refers to mission-specific military goals including, but not
limited to, the minimization of health risks to deployed military personnel.
Technical Guide 230 (TG-230)
TG-230 (USACHPPM 2001a) adapts the generalized framework of TG-
248 and proposes a specific process to evaluate the chemical subset of
OCR for page 31
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 31
TABLE 2-1 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.
OCR for page 32
32 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
OEH/ED hazards. In the first step of this process, chemical hazards are
identified through available intelligence data, field sampling, and/or expo-
sure modeling. Potential chemical hazards are then prioritized on the basis
of whether they pose no threat, a health threat, or a medical threat. Health
threats are hazards that could result in adverse health effects in an individ-
ual. Medical threats are those health threats that have the potential to render
a field unit ineffective for combat or for other mission-related activities.
Threats of chronic or delayed disease (e.g., cancer, liver disease, or kidney
disease) are categorized as threats of concern to the command, which are
generally considered health threats, but on occasion could be considered
medical threats. Each chemical is categorized by comparing measured or
predicted concentrations of that chemical with its most relevant military
exposure guideline (MEG). MEGs are estimated chemical concentrations
above which certain types of adverse health effects might begin to occur in
individuals within the exposed population after a continuous, single expo-
sure of specified duration. They were designed to address the wide variety
of exposure scenarios that could be encountered during deployment, rang-
ing from catastrophic release of a large amount of chemical to regional
pollution. MEGs were developed by modifying the existing exposure stan-
dards set by other agencies for application to the military context. The
process by which MEGs were derived is described in Reference Document
230 (RD-230) (USACHPPM 2001b). That process is evaluated by the
subcommittee in Chapter 5.
Chemical threats are further categorized by using a hazard severity
ranking chart that refers to the four categories of severity defined by the
risk-assessment matrix. The severity ranking charts provided in TG-248
and TG-230 also incorporate specific ranges of probabilities of symptoms
grouped by severity category (see Tables 2-2 and 2-3). Chemical risks are
finally classified using the risk levels defined in the military risk-assessment
matrix. The risk levels correspond to “unit status” levels that are color
coded. Unit status refers to effective unit strength expressed as a percentage
(see Table 2-4). In both guidance documents, these probabilistic unit
strength levels are related to hazard severity levels and hazards probability
categories, but those relationships are made quantitatively explicit in TG-
230 insofar as that document defines the hazard probability categories dis-
cussed above in terms of corresponding troop exposure probability ranges
(see Table 2-5). A confidence level is then assigned to the risk estimate by
using criteria outlined in TG-248 (see Table 2-6). That judgment is made
by considering key sources of uncertainty associated with the risk assess-
ment, such as the quality of the field sampling data and understanding of the
exposure conditions.
OCR for page 33
OCR for page 34
OCR for page 35
OCR for page 36
OCR for page 37
OCR for page 38
OCR for page 39
OCR for page 40
OCR for page 41
OCR for page 42
OCR for page 43
OCR for page 44
OCR for page 45
OCR for page 46
Representative terms from entire chapter:
chemical risks
TABLE 2-2 TG-230 Chemical Hazard Severity Ranking Chart for Military Deployments
Associated Health Outcome
Magnitude of Chemical Concentration
Attributable to Exposure Hazard Severity
Air Water Soil (General)a Onset of Symptoms Rank Hazard Type
<1-year MEG
34
TABLE 2-2 Continued
Associated Health Outcome
Magnitude of Chemical Concentration
Attributable to Exposure Hazard Severity
Air Water Soil (General)a Onset of Symptoms Rank Hazard Type
b c
>1-hour sig- — — 10-25% of personnel might During the mission CRITICAL MEDICAL
MEG experience severe illness or THREAT
irritation and more noticeable
but #1-hour
sev-MEG degradation of performance
capabilities;
Other personnel will, at least,
suffer some mild effects
>1-hour sev- —b —c >25% of personnel might CATASTROPHIC
MEG experience severe,
incapacitating effects;
Fatalities will begin to occur
just above the sev-MEG for
air exposur and will increase
as concentrations increase
a
Percentages are very uncertain and will vary by chemical and by other confounding factors.
b
Concentrations greater than the MEG might result in hazard severity from marginal to catastrophic if certain chemicals are present in large
enough quantities and there is sufficient consumption. Additional information in the “Notes” column of the MEG tables should be evaluated
regarding effects of higher levels of exposure.
c
Soil is unlikely to represent a hazard that would yield a medical threat. Additional information in the “Notes” column of the MEG tables should
be evaluated for data regarding higher levels of exposure.
Abbreviations: min-MEG, minimal effects level; sig-MEG, significant effects level; sev-MEG, severe effects level.
Source: Modified from USACHPPM 2002a.
TABLE 2-3 TG-248 Hazard Severity Ranking Chart for Military Deployments
Nature of Individual Health Effects Associated with Exposures Near the Guideline
Symptoms Occurring
After the Mission Symptoms Occurring During the Mission
Percent of Exposed
People to Exhibit Chronic or Permanent Mild Illness or Injury or Illness That Impairs Incapacitation or
Symptoms (Attack Rate) Injury or Diseasea Temporary Irritationb Functional Capabilities Death
>50% Marginal Critical Catastrophic Catastrophic
31-50% Negligible Marginal Critical Catastrophic
10-30% Negligible Marginal Marginal Critical
<10% Negligible Negligible Marginal Critical
a
For example, cancer.
b
Reversible, short-term, nuisance.
Source: Modified from USACHPPM 2001.
35
36 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
TABLE 2-4 TG-230 Risk Level Definitions
Defined Consequencea Unit Statusb,c
Risk Level
Extremely Expected loss of ability to accomplish the Black (unit requires re-
high mission constitution)
Unit below 50% strength
High Expected significant degradation of mis- Red (combat ineffective)
sion capabilities in terms of the required Unit at 50-69% strength
mission standard, inability to accomplish
all parts of the mission, or inability to
complete the mission to standard if haz-
ards occur during the mission
Moderate Expected degraded mission capabilities in Amber (mission capable,
terms of the required mission standard with minor deficiencies)
will have a reduced mission capability if Unit at 70-84% strength
hazards occur during mission
Low Expected losses have little or no impact Green (mission capable)
on accomplishing the mission Unit at 85% strength or
better
a
Field Manual 100-14 (U.S. Department of the Army 1998)
b
Field Manual 3-100.12 (U.S. Department of the Army 1997)
c
The unit rates provided under “Unit Status” are to be determined by the commander. Charts
similar to the example hazard probability and severity ranking charts presented in Tables 2-
1, 2-2, and 2-3 should be aligned with the acceptable risk levels provided by the commander.
Source: USACHPPM 2000a.
Finally, using all the information at hand, the threat category is re-eval-
uated in terms of whether the chemical poses no threat, a health threat, a
threat of concern to the command, or a medical threat. The purpose of this
final step is to provide perspective on which hazards pose greater opera-
tional threats when comparing threats that have similar risk estimates.
TABLE 2-5 TG-230 Chemical Hazard Probability Ranking Chart for
Military Deployments
Percent of Personnel That Will Experience Exposures to Concentrations Equal To or
Greater Than the MEGa
75 %
Unlikely Seldom Occasional Likely Frequent
a
Determination of the percent of personnel exposed to a chemical or mixture specifically
above a guideline level can be based on modeling, gridding, or generalized assumptions.
Source: USACHPPM 2002a.
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 37
TABLE 2-6 TG-230 Example Criteria for Assigning Confidence Levels
Confidence Level Criteria
High Sampling data quality is good
Field activity patterns are well known
True exposures are reasonably approximated
Knowledge of the symptoms of hazard exposure relative to
guideline is well known
No important missing information
The predicted health outcome is plausible or already demon
strated
Medium Field data quality is good
Field exposures are likely to be overestimates of true exposures
due to incomplete data coverage relative to actual expo
sure durations
Detailed information is lacking regarding true personnel activ
ity patterns in the field
Symptoms are well known for each individual hazard, but some
scientific evidence suggests that the combined effects of
all hazards may exacerbate symptoms
Predicted health outcome is plausible
Low Important data gaps and/or inconsistencies exist
Exposure conditions are not well defined
Field personnel activity patterns are basically unknown
Predicted health outcome is not plausible because it is not
consistent with real-world events/experience
Source: USACHPPM 2002a.
Evaluation1
The risk-management framework presented in TG-230 and TG-248
reflects much of the guidance and recommendations provided by the NRC
(2000) and IOM (2000). DOD, and in particular USACHPPM, is to be
commended for developing a risk-management framework that implements
the recommendations contained in those reports. The generalized frame-
work in TG-248 also comprises innovative features that are suited for prac-
tical use in the field. The framework attempts a quantitative implementa-
tion of a matrix approach to assess risk levels that are implied by different
categories of hazard severity and hazard probability. It uses familiar cate-
gories previously defined in DOD’s overall approach to military risk man-
agement, as described in field manuals FM 100-14 and FM 3-100.12. This
1
Minor errata and inconsistencies found in TG-248, TG-230, and RD-230 are discussed
in Appendix A.
38 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
framework is particularly well-suited to convenient characterization and
evaluation of individual health or medical threats and simple comparisons
of those individual threats, provided comparable levels of uncertainty are
involved.
When applied to assess chemical risks in TG-230 (Table 2-2), the
framework enables the use of a simple, tabular approach to characterize
exposure scenarios chemical by chemical in terms of a corresponding cate-
gorical risk level that in turn refers to a corresponding range of unit strength
(expressed as a percentage). The approach also incorporates traditional
procedures used to identify noncompliance with occupational safety and
health guidelines pertaining to chemical exposures that are expected to
produce health effects (i.e., hazards of “negligible” severity). The latter
involves the use of MEGs to assess the significance of field exposures to
specific chemicals.
Overall, the subcommittee found that TG-248 provides a reasonable
categorization process for assessing OEH/ED hazards within the context of
ORM. The process allows for predicting impacts on missions and making
reasonable comparisons between the potential hazards, be they hazards to
equipment, troops, or some other facet of deployment. However, the
chemical-risk guidance (i.e., the MEGs) in TG-230 is inconsistent with the
intent of TG-248 and could lead to mischaracterization of the significance
of chemical risks in comparison with other deployment risks. This potential
for mischaracterization is the result of USACHPPM’s attempt to use one set
of exposure guidelines (i.e., MEGs) for the dual purposes of “charac-
teriz[ing] the level of health and mission risks associated with identified or
anticipated exposures to chemicals in the deployment environment”
(USACHPPM 2001, p.1; italics added). These conflicting purposes could
lead to different interpretations and uses of the MEGs. For example, RD-
230 states the following:
In some cases, exposures greater than the MEG can induce immedi-
ate adverse health effects, in other cases exposures greater than the
MEG simply indicate that there is an increased likelihood that a
health problem could arise either during or post deployment … In
general, environmental concentrations equal to, or slightly greater
than the specified MEG are expected to result in the specified type
and degree of health effects in none to a small portion of individu-
als in the exposed military population. In some cases, MEG repre-
sents a purely “protective” level where health effects should not be
observed at all.
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 39
The subcommittee summarized the differing goals of mission and health
risk assessment in Table 2-7. The table shows that the parameters for
achieving each of those goals are quite different from each other on all
levels. Those differences make it extremely difficult for one set of guidance
values (MEGs) to adequately address both sets of goals.
The risk-assessment matrix used in TG-230 is a device for categorizing
chemical risks in terms of mission impact (e.g., mission capable, combat
ineffective) so that chemical hazards can be weighed against and compared
with other hazards to missions (e.g., mechanical failures, weather). To
make comparative assessments among all potential deployment hazards, it
is important to assess all hazards in terms of their potential impact on unit
strength. Assessment of those hazards requires an understanding of the
chemical exposure levels at which casualties that would render the unit
ineffective might begin to occur. MEGs are inappropriate for making this
type of assessment because they are health protective values that provide an
estimated threshold at which health effects might begin to occur. Those
threshold concentrations could be several orders of magnitude below those
that would be anticipated to produce enough casualties to compromise a
mission. Thus, mission risks characterized using the MEGs would not be
comparable to the risk levels assigned to other operational hazards using the
risk-assessment matrix. See example in Box 2-1. The subcommittee be-
lieves that separate sets of chemical risk assessment guidance are needed for
assessing mission and health risks. Those assessments should be presented
simultaneously to help decision makers balance the necessary trade-offs
between the mission’s needs and potential health impacts presented by the
deployment mission under consideration.
Mission Risk Assessment
To assess mission risks, it will be necessary for USACHPPM to de-
velop a set of unbiased, predictive estimates of casualties that might occur
if the unit is exposed to a particular concentration of a chemical. The sub-
committee has termed such values chemical casualty estimating guidelines
(CCEGs) and recommends that they be used instead of MEGs to character-
ize mission risks using the ORM categorization scheme. CCEGs would be
media and duration-specific chemical concentrations expected to cause
health impairments that degrade the performance of enough individuals to
reduce unit strength, also known as medical threats. As discussed in more
detail in Chapter 4, CCEGs cannot be established from existing exposure
40 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
TABLE 2-7 Characteristics Associated with the Major Goals of TG-248
and TG-230
Health Risk Assessment Mission Risk Assessment
Goal To predict impacts of health
To assess impacts on indi-
risks on the mission; requires
vidual soldier health; re-
the use of predictive casualty
quires the use of protective
estimates
exposure values
Effects Short- and long-term effects Primarily short-term effects
Length of exposure Long-term exposure Short-term exposure
Situation More like occupa- More like short-term
tional/environmental (OSHA, emergency planning
EPA)
Availability of data More likely to have data avail- More qualitative assessment of
able to assess exposure exposure; relies more on
subjective judgment
Availability of time More time to assess Decisions must be made
quickly
Exposure Assess proportion likely to Assess proportion likely to
assessment receive exposure in excess of receive any mission-
MEGs compromising level of
exposure
Number of Many of concern Limited number of concern
chemicals
Likelihood that Lower Higher
effect(s) will occur
Confidence in Higher Lower
estimated
exposure(s)
standards, but should be derived by conducting independent evaluations of
each chemical and developing exposure-response and population-response
information to make casualty estimations. Although this will be a signifi-
cant undertaking, the number of chemicals and the scope of the data needed
for evaluation are expected to be far less than those that were required to set
the MEGs.
USACHPPM should further prioritize the general risks posed by spe-
cific media of exposure, including air, soil, and water, and the available
risk-management options for various durations of missions. For example,
water contamination could be a serious risk for long-term missions, espe-
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 41
BOX 2-1 Scenario: Securing a River Crossing
The mission is to secure a major river crossing. If the enemy succeeds in crossing
the river, thousands of lives will be lost. The commander has the choice of two routes
to get to the crossing. One is a very rugged road that poses a threat to the mission be-
cause of potential vehicle roll-over, mechanical failure, and other hazards related to
terrain impacts on vehicles. The other route is paved but goes by a chemical plant that
has structural damage and is believed to be leaking chemical X. Chemical X can cause
irritation of the mucous membranes and respiratory system, headache, and nausea that
could impair the functional capabilities of the troops. In addition, chemical X is associ-
ated with potential long-term effects.
To decide which route to take, the commander needs to know the potential terrain
risks and chemical risks to the unit. For the terrain risks, the commander will be provided
with an assessment of whether enough vehicles will be disabled during the rugged terrain
crossing such that an insufficient number of troops and equipment will be able to reach
and secure the river crossing. For a comparable assessment of chemical risks, a predic-
tion is needed of whether the exposure incurred by passing the chemical plant will disable
enough troops to the extent that they could not perform their duties. However, using the
current set of guidance, it would be impossible to get a chemical assessment comparable
to the terrain assessment, because the relevant MEG for chemical X in TG-230 will not
be a casualty estimate but a health protective guideline. The short-term MEGs for
chemical X will define a level at which respiratory irritation, headache, and nausea would
begin to occur, and using them as benchmarks in conjunction with the risk-assessment
matrix would result in overestimating the risk that chemical X poses to the mission. In
addition to the assessment of risks to the mission, the commander will also need to be
informed of the long-term health risks posed by chemical X.
cially when establishing a base of operations. However, water contamina-
tion generally is the easiest to mitigate by avoidance, treatment, or use of
alternative sources. Air contamination is probably the most important con-
sideration for short-term missions. Short-duration releases of chemical
warfare agents or deliberate releases of toxic industrial chemicals could
have immediate acute effects. A general example of risks prioritization on
the basis of duration of exposure and mitigation options is provided in
Table 2-8. USACHPPM should use a similar scheme to establish a set of
criteria for CCEGs. A preliminary characterization of those guidelines is
provided in Box 2-2.
Important issues to consider in developing CCEGs include the follow-
ing:
• Risk should be defined as an unbiased or “best” estimate. When an
integrated quantitative approach is used to estimate risk and its uncertainty,
an appropriate corresponding attribute of a risk or casualty number to esti-
42 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
TABLE 2-8 General Prioritizations of Exposure Routes in Relation to
Exposure Duration and Possible Mitigation
Exposure Dura-
Routes of Exposurea and Mitigation
tion
Short mission Air Soil Water
Respirator PE (booties) Avoid
Long mission Water Air Soil
Treatment Filtered shelter Avoid
a
In order of decreasing risk, left to right.
mate would be its expected value, or “population mean,” defined mathemat-
ically as the arithmetic average of all possible likelihood-weighted values.2
• TG-230 makes it clear that “unit strength” should refer not only to
directly affected personnel but also to individuals affected to a lesser extent
2
“Likelihood” weights in this context mean probabilities from a distribution that reflects
uncertainty in a true but unknown value that must be estimated. Expected values have two
key properties that do not generally apply to other measures of central tendency, such as
medians or modes. First, the arithmetic mean of a random sample of observed values of any
uncertain variable always provides an unbiased (i.e., not systematically error-prone) estimate
of the (unknown) expected value of that variable. Second, the expected value of any func-
tion of uncertain but statistically independent input variables can always be estimated conve-
niently (at least to a first order of approximation) by calculations that involve only estimates
of the expected value of each separate input variable. If a function of independent input
variables is “linear” (i.e., involves only the sum, difference, product, and/or ratio of those
variables), then the expected value of the function always exactly equals the function of the
expected values of the input variables. For example, using e(z) to denote “the expected
value of an estimated variable z,” if a total number (n) of casualties is estimated as the
product of independent and uncertain variables representing concentration (c), potency (q),
and number (x) of potentially exposed personnel, then it will always be true that e(n) = e(c)
× e(q) × e(x), regardless of the shapes of the distributions that characterize uncertainty in c,
q, and x, respectively.
These two useful properties of expected values can be applied conveniently to compare
alternative courses of action (say, COA1 vs COA2) expected to generate two corresponding
numbers (N1 vs N2) of casualties. A reasonable and consistent rule often used for this type
of decision is to always reject COA2 if e(N2 - N1) > 0. This rule by definition minimizes
the expected number of predicted casualties (Raiffa 1970). By virtue of the expected-value
properties mentioned above, this rule always can be re-expressed validly in a form that
conveniently involves only the expected value of each separate casualty prediction—namely,
always reject COA2 if e(N2) > e(N1). Although more elaborate decision rules can be used
to account for the shape of the distribution of uncertainty in the difference (N2 - N1) rela-
tive to a specified set of risk-aversion preferences, complex rules of this type typically
require quantitative uncertainty analysis methods likely to be impractical for most current
military operational risk-management contexts.
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 43
BOX 2-2 CCEG Characteristics
• Include chemicals likely to be encountered in sufficient quantities to degrade
mission effectiveness.
• Include health effects that are manifested within minutes, hours, or several days
that could immediately affect the functioning of troops (e.g., loss of cognitive ability, loss
of visual acuity, significantly reduced cardiopulmonary functioning, muscular weakness)
performing a mission. Does not include long-term health effects (e.g., cancer).
• Consider exposure time frames of hours, days, and weeks, rather than months
or years.
• Relate to the military population, which includes generally healthy adult men
and women with typical variations in genetic susceptibilities.
• Provide exposure-response and population-response information, insofar as
possible. Include concentrations likely to cause effects in humans, along with a descrip-
tion of the severity and incidence expected. This information would enable chemical
threats to be weighed in comparison to other mission threats (e.g., Table 3-1 in TG-230
would be more useful).
• Provide guidance primarily for the air exposure pathway, because troops have
no choice but to breathe the air (except when gas masks are used). Theoretically, the
water pathway might influence CCEGs, but the availability of alternative sources of
water makes it relatively less important. Water exposure scenarios of special concern
should be identified and addressed. Soil also deserves some consideration, but is unlikely
to be a significant source of exposure.
and support personnel required to tend to directly affected personnel. The
multiplication of hazard severity probabilities (i.e., illness likelihood
ranges) by hazard probability ranges clearly is not intended to yield corre-
sponding defined-target ranges of “fractional unit incapacitation” (i.e., the
opposite of unit strength, as defined in TG-230). Therefore, USACHPPM
must consider developing CCEGs that provide an assessment of overall unit
incapacitation with increasing exposure levels. (TG-230 also mentions that
severe toxic effects will lead to increased medical support requirements for
affected personnel, but it was not clear to the subcommittee how that sup-
port necessarily would reduce unit effectiveness, insofar as required medical
support personnel would be performing their intended function.)
• The need for a categorical confidence-level scheme (high vs me-
dium vs low) in TG-248 and TG-230 should be reconsidered. The assign-
ment of confidence levels is not a recommendation in the ORM process
presented in Field Manual 3-100.12 (DOD 2001), so other operational risks
will not be assigned confidence levels. It is unclear how decision makers
are to interpret a specified confidence level, particularly a low one, when
trying to balance competing operational risks. A low confidence in the risk
characterization gives no indication of whether actual risk might be higher
44 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
or lower than the predicted risk. Furthermore, it is unclear how confidence
level description for chemical risks would be of value to decision makers
if confidence levels are not assigned to other operational risks.
Chapter 4 presents more specific guidance for developing CCEGs and
discusses how the guidelines should be applied.
Health Risk Assessment
Another goal of TG-230 is to provide force health protection, with the
understanding that mission success has primacy over some health risks that
might be considered unacceptable under less hazardous conditions. With
some modifications, MEGs can be used to fulfill that goal. To that end,
MEGs would be concentrations of chemicals in air, water, and soil that can
be used to estimate the potential impact of field exposures on soldier health
during deployments. A preliminary characterization of MEGs is presented
in Box 2-3. MEGs would be used to determine the appropriate management
actions that could be taken to avoid or mitigate risks. Depending on the
particulars of the deployment scenario, commanders could decide whether
the benefits of the mission outweigh the possible health risks to individual
soldiers. In cases where commanders decide to accept the health risks to
soldiers, MEGs could be used to determine what kinds of health-manage-
ment actions to take, such as documenting exposures in soldiers’ records,
conducting additional environmental sampling, or conducting follow-up
health monitoring. Chapter 5 provides a more detailed description of how
MEGs should be derived and applied.
BOX 2-3 MEG Characteristics
• Include a large number of chemicals likely to be present in deployments.
• Include concerns over longer-term health of individuals, but recognizing that
exposures at these levels would have no to minimal impact on immediate missions.
• Include virtually all exposure durations from 1 hour to 1 year.
• Relate to the military population.
• Indicate protective levels (i.e., levels assumed to represent no adverse effects
or very low risk) for the exposure durations of interest.
• Provide guidance for management actions when MEGs are exceeded.
REVIEW OF THE ARMY’S TECHNICAL GUIDANCE 45
RECOMMENDATIONS
• TG-230 should be revised to provide separate guidance on assess-
ing chemical hazards for the purposes of mission and health risk assess-
ment.
• For the purposes of mission risk assessment, risks should be evalu-
ated within the context of mission success. The subcommittee recommends
the development of chemical casualty estimating guidelines (CCEGs) to
provide an appropriate basis for comparison with other mission hazards.
CCEGs would be media and duration-specific chemical concentrations
expected to cause health impairments that debilitate the performance of
enough individuals to significantly reduce unit strength and effectiveness.
They would be predictive values that provide unbiased quantitative
exposure-response and population-response information that enables com-
manders to compare the risks from chemical threats to those from other
mission threats (e.g., combat casualties, logistical problems) using the same
metric. The goal is to provide reasonably accurate estimates of impacts on
unit strength. Chapter 4 provides guidance on how to derive CCEGs.
• CCEGs should be developed for a subset of the chemicals for which
MEGs have already been derived. Chemicals should be selected on the
basis of their potential as immediate medical threats to missions. Warfare
agents and high-production-volume industrial chemicals with high toxico-
logical potency are the most likely candidates. Inhaled volatile chemicals
or toxic particulate matter also are likely to fall into that category, although
chemical exposures by ingestion and skin contact should likewise be con-
sidered.
• The need for assigning confidence levels to mission-risk estimates
should be reconsidered.
• For the purposes of health protection, chemical risks should be
assessed independently of operational goals. USACHPPM’s current set of
military exposure guidelines (MEGs) are health-protective values that, with
some modification, could fulfill that need. MEGs should be used to define
risk-management actions that can be taken to avoid or mitigate potential
health risks. Chapter 5 expands on this recommendation.
• Mission-risk and health-risk information should be provided to
decision makers simultaneously, so that risks can be balanced explicitly and
appropriate management actions can be taken.
• As guidance on applying TG-248 to other OEH/ED hazards (e.g.,
radiological and biological hazards) is developed, USACHPPM should
consider combining all of the guidance into a single document to facilitate
consideration of cumulative risks from all environmental hazards.
46 TECHNICAL GUIDES ON ASSESSING AND MANAGING CHEMICAL HAZARDS
REFERENCES
DOD (U.S. Department of Defense). 2001. Risk Management. Multiservice Tactics,
Techniques and Procedures. FM 3-100.12. MCRP 5-12.1C. NTTP 5-03.5. AFTTP(I)
3-2.34. Air Land and Sea Application Center. U.S. Army Training and Doctrine
Command, Fort Monroe, VA; Marine Corps Combat Development Command, Quan-
tico, VA; Navy Warfare Development Command, Newport, RI; and Headquarters Air
Force Doctrine Center, Maxwell Air Force Base, AL. [Online]. Available:
http://www.adtdl.army.mil/cgi-bin/atdl.dll/query/download/FM+3-100.12 [accessed
Dec. 2, 2003].
IOM (Institute of Medicine). 2000. Protecting Those Who Serve: Strategies to Protect the
Health of Deployed U.S. Forces. Washington, DC: National Academy Press.
NRC (National Research Council). 1983. Risk Assessment in the Federal Government:
Managing the Process. Washington, DC: National Academy Press.
NRC (National Research Council). 1994. Pp. 161-244, 516-518 in Science and Judgment
in Risk Assessment. Washington, DC: National Academy Press.
NRC (National Research Council). 2000. Strategies to Protect the Health of Deployed U.S.
Forces: Analytical Framework for Assessing Risks. Washington, DC: National Acad-
emy Press.
Raffia, H. 1970. Decision analysis: introductory lectures on choices under uncertainty. 2nd
Ed. Harvard University Press, Cambridge, MA.
USACHPPM (U.S. Army Center for Health Promotion and Preventive Medicine). 2001.
Guide for Deployed Preventive Medicine Personnel on Health Risk Management.
Technical Guide 248. U.S. Army Center for Health Promotion and Preventive Medi-
cine. August 2001. [Online]. Available: http://chppm-www.apgea.army.mil/ deploy-
ment/ [accessed November 25, 2003]
USACHPPM (U.S. Army Center for Health Promotion and Preventive Medicine). 2002a.
Chemical Exposure Guidelines for Deployed Military Personnel. Technical Guide 230.
U.S. Army Center for Health Promotion and Preventive Medicine. January 2002.
[Online]. Available: http://chppm-www.apgea.army.mil/deployment/ [accessed No-
vember 25, 2003]
USACHPPM (U.S. Army Center for Health Promotion and Preventive Medicine). 2002b.
Chemical Exposure Guidelines for Deployed Military Personnel. A Companion Docu-
ment to USACHPPM Technical Guide (TG) 230 Chemical Exposure Guidelines for
Deployed Military Personnel. Reference Document (RD) 230. U.S. Army Center for
Health Promotion and Preventive Medicine January 2002. [Online]. Available:
http://chppm-www.apgea.army.mil/deployment/ [accessed November 25, 2003]
U.S. Department of the Army. 1997. Operational Terms and Graphics. Field Manuel No.
FM 101-5-1/MCRP 5-2A. Headquarters, Department of Army, U.S. Marine Corps,
Washington, DC. September 30, 1997.
U.S. Department of the Army. 1998. Risk Management, Field Manual No. 100-14. U.S.
Department of the Army, Washington, DC. April 23, 1998.