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3
Approach to the Task
The organizing principles, themes and structure for this study are derived from two sources. First, the state -
ment of task asks the Institute of Medicine (IOM) to determine “the potential long-term health effects of exposure
to burn pits in Iraq and Afghanistan” and to design a future study of long-term health effects in veterans who may
have experienced these exposures. Although the statement of task specifies that Joint Base Balad (JBB) in Iraq
be considered as an example of a military base with a burn pit, it is clear that the Department of Veterans Affairs
(VA’s) interest extends to all military personnel deployed to bases in Iraq and Afghanistan who may have been
exposed to burn pit emissions. These dual objectives shaped the committee’s comprehensive search for information
on relevant exposures and health outcomes, as well as its highly focused analyses of data and information from
military reports specific to JBB and other burn pit locations.
Second, meeting the statement of task objectives entailed an in-depth examination of a substantial body of
information on exposure to combustion products and health effects. For example, the health effects literature on
dioxin-like compounds and particulate matter (PM) is vast, and they are but two of the numerous and diverse
environmental agents likely to be found in burn bit emissions. Similarly, a cursory review of the scientific litera -
ture reveals a wide range of health outcomes—cancer, pulmonary disease, cardiovascular disease, neurological
effects—in human populations exposed to environmental agents found in combustion products, singly and in mix -
tures. Comparable studies on laboratory animals often complement and supplement the data from human studies.
Effective use of this wide-ranging literature requires a systematic approach. The “risk assessment paradigm”
introduced in the seminal report Risk Assessment in the Federal Government, Managing the Process (NRC 1983)
offers a simple, flexible template. Drawing on advances in the theory and practice of risk assessment in the regu -
latory context, subsequent reports and guidelines have modified and expanded the paradigm to take into account
issues specific to, for example, air pollutants (NRC 1994), ecological risk (EPA 1998), and the relationship between
risk assessment and decision-making (NRC 2009). This paradigm, now called a conceptual framework, has been
updated with more emphasis on problem formulation and improvements in technologic analyses and to provide
more guidance on expanding the utility of risk assessments (NRC 2009). As shown in Figure 3-1, this paradigm
calls for several analyses:
• xposure assessment—including the analysis of exposures, qualitative and quantitative, currently experi-
E
enced or anticipated under existing or expected conditions;
23
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24 HEALTH CONSEQUENCES OF EXPOSURE TO BURN PITS
• azard identification—which requires determining whether exposure to a particular environmental agent
H
has the potential to increase the incidence of an adverse health effect and, for particular exposure conditions,
which agents can lead to adverse effects, thus requiring follow-up through dose–response or exposure-
response analysis; and
• xposure–response/dose–response or toxicity assessment—which quantifies the relationship between the
E
exposure or dose in humans and the incidence of adverse effects or health outcomes in human populations
or laboratory animals; and Risk characterization—which synthesizes and integrates data and information to
develop a quantitative estimate of the incidence of the effect in a given population, along with a discussion
of related qualitative considerations, strengths, limitations, and uncertainties.
This report is organized around the assessment process with modifications to address the specific issues
raised in the statement of task. As shown in Figure 3-2, the process focuses first on research and data collection
related to exposures at JBB, health effects that might result from those exposures, and health outcomes in other
human populations exposed to some of the environmental agents found in ambient samples and potentially emit -
ted by the JBB burn pit. Based on this information, assessments are then made on potential exposures and health
effects that might occur in relevant populations. Rather than conduct a formal, quantitative risk assessment and
risk characterization, the committee prepared a synthesis and summary of key findings and applied that informa -
Research Risk Assessment
Laboratory and field
Hazard identification
observation of adverse
(What adverse health
health effects and
effects are associated
exposures to particular
with the agent?)
agents
Dose-response assessment
(What is the relationship
Risk characterization
Information on between dose and the
(What is the estimated
extrapolation methods for probability of an
incidence of the
high to low dose and occurrence of adverse
adverse effect in a
effects in animals or the
animal to human
given population?)
incidence of adverse
effects in humans?)
Exposure assessment
(What exposures are
Field measurements,
currently experienced by
estimated exposures,
or anticipated for the
characterization of
population under existing
populations
or expected conditions?)
FIGURE 3-1 Elements of the risk assessment paradigm.
SOURCE: Adapted from NRC (1983, 2009).
fig 3-1.eps
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25
APPROACH TO THE TASK
Data Collection and Review Summary and Synthesis New Study Design
Information on types and
quantities of materials
burned during the time of
pit use (Chapter 2)
Analysis of air monitoring
Synthesis of key
data collected at Joint Base
information on
Balad (Chapter 4) Quality potential long-term
Study design elements and
Relevance health effects in
feasibility considerations
Weight-of-
Anticipated health effects military personnel
(Chapter 8)
the-evidence
from exposure to air exposed to burn
pollutants found at Joint pits (Chapter 7)
Base Balad (Chapter 5)
Studies of health effects in
similar populations with
similar exposures
(Chapter 6)
FIGURE 3-2 Approach to the statement of task: The types of information reviewed and the process used to develop this report.
fig 3-2.eps
tion to suggest design elements for a future epidemiologic study to address data gaps. The resulting three-stage
analytical process is outlined below:
1. Data collection and review: For this report, the “exposure assessment,” “hazard identification,” and “dose–
response” tasks in the 2009 framework are merged as “data collection and review” activities focused on
chemicals detected in air monitoring at JBB and on smoke exposures per se. These activities revolve around
two closely related but distinct topics: exposure and health effects. The in-depth review begins with iden -
tifying and selecting agents and corresponding reliable studies to be given priority for evaluating health
outcomes potentially associated with burn pit exposures. This includes establishing criteria for evaluating
the quality and relevance of the studies along with their limitations and uncertainties (see Chapters 4, 5,
and 6).
2. Synthesis: Assessing “the potential long-term health effects of exposure to burn pits in Iraq and Afghanistan”
requires the identification and evaluation of the key findings from the comprehensive review of environ -
mental monitoring data and health effects information. One focus is on identifying which, if any, of the
many environmental agents detected in the air at JBB are present in toxicologically significant quantities,
and which, if any, are associated with the burn pit, and determining the reliability of those data. Another
focus is the major findings on health effects seen in other similarly exposed populations as discussed in
Chapter 6, including the extent to which these populations experienced exposures relevant (with respect
to chemical composition and level of exposure) to those at JBB. A related question is how comparable
those populations are to military personnel stationed at JBB. This synthesis includes a discussion of the
committee’s confidence in the quality and utility of these findings for the VA (see Chapter 7).
3. New study design: The exposure–response information developed in Chapters 5 and 6, combined with infor-
mation on the potential exposures of JBB personnel discussed in Chapter 4, provide the basis for evaluating
feasibility and design issues specific to an epidemiologic study to assess health outcomes associated with
exposure to burn pit emissions at JBB and other burn pit sites (see Chapter 8).
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26 HEALTH CONSEQUENCES OF EXPOSURE TO BURN PITS
Each of the following sections corresponds to one of the three steps in the analytical process. The next section,
“Data Collection and Review,” outlines the kinds of data and information needed to evaluate long-term health effects
in line with the statement of task and related risk assessment principles, and explains the principles and processes
guiding the evaluation and selection of data presented in the remainder of the report. In the section titled “Sum -
mary and Synthesis,” the committee summarizes and highlights critical findings from the previous section. In the
final section, “New Study Design,” this information is used to propose design elements for a future epidemiologic
study of health effects in veterans who may have been exposed to burn pit emissions at JBB.
DATA COLLECTION AND REVIEW
Data collection for this report centered on two general topics: first, information on environmental releases
and concentrations of combustion products at JBB and the resulting potential human exposures, and second, the
potential for long-term health effects resulting from those exposures. Principles and methods guiding the commit -
tee’s assessment of the data are outlined in the following sections.
Environmental Exposure
Exposure assessment requires characterization of the frequency, magnitude, and duration of exposure to an
agent of concern in an exposed population (NRC 2010). The committee began assessing possible burn pit emis -
sion exposures by reviewing Department of Defense (DoD) air monitoring data collected at JBB and attempting
to determine whether the air pollutants detected during the sampling periods could be attributed to the burn pits or
might possibly originate from other sources, either natural or anthropogenic (see Chapter 4). Three DoD documents
were used to characterize ambient concentrations: the 2008 Screening Health Risk Assessment Burn Pit Exposures,
Balad Air Base, Iraq and Addendum Report (Taylor et al. 2008), a second addendum to the report (CHPPM and
AFIOH 2009), and a follow-up Screening Health Risk Assessments study in 2010 (USAPHC 2010). The com-
mittee asked for and received from DoD raw air-sampling data collected in 2007 and 2009 to help in identifying
potential sources of the air pollutants. The raw data was not only useful for determining which chemicals were
tested for in the samples, but they were also useful in determining which chemicals were found at concentrations
above the analytical detection limit. Those chemicals present above the detection limit were considered to warrant
further assessment.
The committee recognized that air quality in a region is affected by many factors, such as temperature,
humidity, meteorological events, and atmospheric inputs from both natural sources such as dust storms and from
anthropogenic sources such as power plants, agriculture, and industrial facilities. Thus, the committee asked for
and received from DoD meteorological information for the JBB area during the air monitoring periods.
The location and activities of the military personnel stationed at JBB was also a factor for assessing exposure.
The committee noted that not only did the personnel work on the base, but they also lived there and thus were
potentially exposed to the burn pit emissions 24 hours a day, 7 days a week, although potentially at different levels
during on- and off-work hours. Furthermore, it was assumed that some personnel would have greater exposure to
burn pits either because they actually worked in the pits or may have had a job that required them to work near
the pit. The committee did not ask the DoD for specific information regarding the number of military personnel
that worked at or in close proximity to the burn pit. Because JBB had both Army and Air Force personnel, and
the base was used as a transit stop for some personnel, the duration of exposure to the burn pit emissions was also
highly variable. The committee assumed that some unknown number of personnel would experience high exposure
to burn pit emissions based on their military occupation specialty and their housing location and other personnel
might have relatively low exposure.
Potential Long-Term Health Effects
Assessing potential long-term health effects from exposure to environmental agents depends on two closely
related but different aspects of exposure. The environmental exposure information developed in Chapter 4 describes
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27
APPROACH TO THE TASK
the occurrence and concentration of environmental agents in external media, in this case air. This information
can provide a starting point for evaluating internal exposure—the presence and behavior of agents in living
systems—and the biological response to that exposure. Alternatively, the information may be used directly in
exposure-response evaluations without a full evaluation of dose. Ideally, however, assessment of health effects
includes data on internal dose—the amount of agent in the tissues of the organism. Many factors determine internal
dose, including the concentration of the agent in environmental media, the physical and chemical properties of the
agent, and individual metabolic processes of the organism. Information on the majority of these exposure factors
for military personnel living and working at JBB is unavailable or incomplete. Thus, the committee conducted its
review assuming that deployed personnel were exposed to burn pit emissions primarily through inhalation and
they received some unquantified internal dose of the chemicals present in burn pits emissions. The committee
recognized that some dermal and ingestion exposure was possible, albeit at relatively minor levels. However, the
lack of data on contaminant levels in soil, food, water, and surfaces at JBB precluded further consideration of
ingestion and dermal routes of exposure.
Studies on Health Effects
For chemical mixtures such as burn pit emissions, toxicity and other health effects data on the mixture itself
are generally scarce or nonexistent. In view of this paucity of data, the committee focused on studies of exposure
to individual chemicals, and exposure to similar mixtures in surrogate populations. First, studies of exposure to
known individual chemicals in laboratory animals provide information on health effects (or lack thereof) attribut -
able to specific chemicals at relevant exposure levels (Chapter 5). These studies can be important sources of both
qualitative (the nature and range of health effects observed such as cancer, neurological effects, and reproductive
effects) and quantitative (dose–response or exposure–response relationships) information on health effects in
test animals associated with exposure to specific chemicals under controlled laboratory conditions. However, the
extent to which animal studies are predictive of health effects (or lack of effects) in humans varies considerably.
The variety of materials burned at JBB produced a complex mixture of chemicals of differing toxic poten -
tial, occurring in different amounts and physical forms. The emissions from the burn pits were also mixed with
numerous air pollutants from other local and regional sources such as industry and dust storms. Based on the air
monitoring data analyzed in Chapter 4, the committee determined the likely adverse health effects that might be
associated with those chemicals found above the analytical detection limit or that otherwise were expected to
pose the greatest risk to JBB personnel. To identify potential health effects from these exposures, the committee
relied on published summaries from diverse sources, including IOM and NRC reports, government reports such
as toxicological profiles from the Agency for Toxic Substances and Disease Registry, and established databases
such as the U.S. Environmental Protection Agency’s (EPA’s) Integrated Risk Information System (IRIS). 1 The
committee did not re-examine the underlying data or methodology for these sources; rather, it relied on them as
well established sources of health effects information (see Chapter 5).
Epidemiologic Studies
Given the lack of information on health effects that may result from exposure to burn pit emissions per se, the
committee sought information on health effects from epidemiologic studies of other (non-Balad) human popula -
tions exposed to smoke, combustion products, or other complex chemical mixtures that include at least some of
the chemical constituents present in burn pit emissions (see Chapter 6). The committee gave special attention to
studies involving other military populations, firefighters, and residents living near municipal waste incinerators.
Those studies provide data on demographically similar populations (relatively young and healthy, and predomi -
1 Although scientists throughout the world use the IRIS database for its valuable toxicity and risk information, many IRIS profiles need to be
updated to take into account new pollutant-specific data and advances in methodology or to correct inaccurate values (NRC 2008). Although
the committee recognizes these concerns and the resulting uncertainties they create, these values, with those from other health agencies, are
the best readily available data for assessing pollutants emitted from open burning.
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28 HEALTH CONSEQUENCES OF EXPOSURE TO BURN PITS
nantly male) exposed to similar pollutants (chemical mixtures produced by burning). In selecting studies for this
report, the committee focused on factors such as exposure duration, populations of interest, criteria for identifying
key studies, and determining categories of association between exposures and health effects.
Exposure Duration
In general, the available studies involved one of three exposure–response patterns: (1) medium-term expo -
sure (6 months to a year) to higher pollutant levels that might increase the risk of chronic disease later in life
(medium-term exposure/long-term health effects); (2) short-term exposure (over a few days) to higher pollutant
levels that might increase the risk of chronic disease later in life (acute exposure/long-term health effects); and
(3) short-term exposure to higher pollutant levels that might increase the risk of an acute adverse health event
immediately following or shortly after exposure (acute exposure/acute health effects). For relevance to veterans
of the current conflicts, the committee focused on long-term health outcomes that persist after exposure ceases,
rather than acute health effects.
Populations of Interest
Assessing potential future effects of exposure in a particular population such as JBB personnel depends on
available information for that population together with observational data on effects in theoretically similar popula-
tions exposed under generally comparable conditions. Three occupational populations were of special interest to
the committee because of their exposure to complex mixtures of combustion products potentially similar to burn
pit emissions: firefighters (wildlands and urban), municipal waste incinerator workers, and military personnel from
several earlier deployments (Bosnia, Kuwait, Iraq, Afghanistan). The IOM has evaluated the scientific literature
on military personnel deployed to the 1990–1991 Persian Gulf War in previous reports (IOM 2005, 2006, 2010),
which this report incorporates by reference where appropriate. Residents living in the vicinity of municipal waste
incinerators were also included in the committee’s deliberations as personnel at JBB not only work on the base
but live there as well with the potential for 24-hour exposure. Finally, the committee sought, but did not find,
epidemiologic information on health effects seen in Iraqi civilians living near bases with burn pits or other sources
of combustion products, such as local waste burning operations or wild fires.
Selection of Key Studies
The studies reviewed in Chapter 6 are designated “key” or “supporting” depending on several criteria as
described in that chapter. Consistent with previous IOM reports (IOM 2010), to be designated “key” a study had
to include information about the putative exposure and specific health outcomes, demonstrate rigorous methods,
include methodological details sufficient to allow a thorough assessment, and include an appropriate control or
reference group. A “supporting” study typically had methodologic limitations, such as lack of a rigorous or well-
defined diagnostic method or lack of an appropriate control group. The committee’s evaluations of key and sup -
porting studies used in reaching its conclusions are described in greater detail in Chapter 6.
Categories of Association
The committee considered the studies identified in Chapter 6 in terms of the strength of the apparent associa -
tion between the exposures to combustion products and potential health effects. As detailed in Chapter 6, the five
categories used by the committee represent different strengths of association and different levels of confidence in
the potential relevance and utility of each study. The validity of an observed association is likely to vary with the
extent to which common sources of spurious associations can be ruled out as contributing factors. Accordingly, the
criteria for each category express a degree of confidence based on the extent to which sources of error were reduced.
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APPROACH TO THE TASK
SUMMARY AND SYNTHESIS
Understanding the potential for long-term health effects associated with human exposure to burn pit emis -
sions depends on the reliability and utility of the available data on exposures at JBB and other burn pit locations,
as well as exposure and outcome data from studies on other populations exposed to some of the same combustion
products, singly or in mixtures. Each of the three main data sources—data specific to JBB, other military reports,
and the peer-reviewed literature—provides useful and relevant information, but each has major limitations.
In this section, the committee summarizes and highlights key findings on materials burned at JBB and other
military burn pit locations, health effects data on the combustion products detected at JBB, and studies on health
effects in non-Balad populations potentially exposed to similar chemicals. The committee comments on its con -
fidence in these findings and on their usefulness in providing the VA with information for medical follow-up and
future studies. The committee also considers the possible impact of co-exposure to combustion products from local
and regional air pollution sources other than the JBB burn pit.
NEW STUDY DESIGN
The statement of task directs the committee to “examine the feasibility and design issues for an epidemiologic
study of veterans exposed at the Balad burn pit.” Two recent IOM reports on other military populations offer useful
models. First, a study on depleted uranium in military and veteran populations (IOM 2008) identifies key features
of a well-designed epidemiology study of potential health effects associated with environmental exposure.
Second, the review of the DoD’s Enhanced Particulate Matter Surveillance Program (NRC 2010) identifies
exposure assessment as a central element in the study design for that proposed study because “if data are not avail -
able to characterize exposure, any study of association between health outcomes and exposure will not provide
valid results.” Any study of JBB exposures is necessarily incomplete because of the limited exposure information
available. Specifically, the military collected environmental samples at fixed locations, but the relation to individual
exposures may be difficult to ascertain, be subject to large uncertainties, or both. Since the JBB burn pit was closed
in 2009, no additional opportunities are available to collect environmental or personal monitoring data on burn pit
emissions at JBB, although it is still possible to conduct air monitoring, including personal monitoring, at other
military sites with operational burn pits.
Epidemiologic studies conducted at JBB and other bases with burn pits have substantial acknowledged limita -
tions (for example, lack of adequate follow-up for the diagnosis of conditions with long latency such as chronic
bronchitis, emphysema, systemic lupus erythematosus, and cancer). Taking these considerations and the key find -
ings in this report into account, the committee closes with a discussion of design issues for a future epidemiologic
study of the JBB population and outlines a proposed approach for that study.
REFERENCES
CHPPM (U.S. Army Center for Health Promotion and Preventive Medicine) and AFIOH (U.S. Air Force Institute for Opera -
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USACHPPM Report No. 47-MA-08PV-08/AFIOH Report No. IOH-RS-BR-TR-2008-0001. Aberdeen Proving Ground,
MD: U.S. Army Center for Health Promotion and Preventive Medicine. August.
EPA (U.S. Environmental Protection Agency). 1998. Guidelines for ecological risk assessment. EPA/630/R-95/002F. Wash-
ington, DC: Risk Assessment Forum.
IOM (Institute of Medicine). 2005. Gulf War and health: Volume 3. Fuels, combustion products, and propellants. Washington,
DC: The National Academies Press.
IOM. 2006. Gulf War and health: Volume 4. Health effects of serving in the Gulf War . Washington, DC: The National Acad-
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IOM. 2008. Epidemiological studies of veterans exposed to depleted uranium: Feasability and design issues . Washington, DC:
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NRC. 1994. Science and judgment in risk assessment. Washington, DC: National Academy Press.
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