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technical BRIEF
BUILDING A SCIENTIFIC FOUNDATION FOR SOUND ENVIRONMENTAL DECISIONS
Exposure Assessment of Livestock Carcass
Management Options During Natural Disasters
Introduction
Proper management of
livestock carcasses
following large-scale
mortalities protects
humans, wildlife, and
the environment from
chemical and
biological hazards. In
support of the National
Response Framework,
the U.S. Department of
Homeland Security
(DHS) Science and
Technology Directorate funds research in collaboration the U.S. Environmental Protection
Agency's (USEPA's) Homeland Security Research Program (HSRP) and the U.S. Department
of Agriculture's (USDA's) Animal and Plant Health Inspection Service (APHIS) to support the
proper management of animal carcasses following major environmental incidents involving the
agricultural sector. Mass livestock mortalities can result from a natural disaster, foreign animal
disease (FAD) outbreak, chemical or radiological incident, or other large-scale emergencies.
As a product of the collaborative research between USEPA, DHS, and USDA, this research
brief summarizes an evaluation of livestock carcass management options following a natural
disaster through a comparative exposure assessment. This assessment helps to inform a
scientifically-based selection of environmentally protective methods in times of emergency.
Future phases of this project will examine a FAD outbreak and chemical or radiological
incidents.
In actual natural disasters, many site-specific factors contribute to potential chemical and
microbial exposures from carcass management activities. The exposure estimates presented
in this summary should not be interpreted as "actual" exposures associated with the
management options. However, site managers can use these findings, in conjunction with site-
specific factors, to make informed decisions about which carcass management options would
minimize risks to human health and the environment for specific locations.
U.S. Environmental Protection Agency
Office of Research and Development, Homeland Security Research Program
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Evaluation Approach
The livestock carcass management options included in this exposure assessment are seven
well-established methods with sufficient capacity for large-scale carcass management: on-site
open burning (pyre), on-site air-curtain burning, on-site unlined burial, on-site composting, off-
site fixed-facility incineration, off-site landfilling, and off-site carcass rendering.
Conceptual models were developed for all seven carcass management options to identify
potential exposure pathways resulting from implementation of those carcass management
options to address a hypothetical natural disaster scenario (USEPA, 2017).
With the three off-site options, all releases to the environment are restricted by, and are
assumed to comply with, applicable U.S. federal regulations. Therefore, chemical and
microbial releases from off-site commercial facilities are assumed to be adequately controlled.
The number of potential chemical and microbial exposure pathways in conceptual models for
the three off-site management options are lower than for the four on-site options. These
differences are the basis of a Tier 1 ranking (first tier ranking of the seven carcass
management options based on the level of regulatory pollution controls) shown in Table 1.
Table 1. Tier 1 Ranking of Livestock Carcass Management (Offsite vs. Onsite) Options
Tier 1
Ranking
Management
Options
Exposure Pathways3
Controls and Limits to
Environmental Releases
Chemical
Microbial
Rank 1:
Negligible to
minimal
exposure -
releases
regulated to
levels safe
for human
health and
the
environment
Incineration
6
6
Air emissions regulated under the Clean
Air Act (CAA), including pollution control
equipment (e.g., scrubbers, filters), with
tall stacks to prevent localized deposition;
residuals (i.e., ash) managed under the
Resource Conservation and Recovery Act
(RCRA); wastewater managed under the
Clean Water Act (CWA).
Rendering
3
2
Releases to air and to water regulated
under the CAA and CWA, respectively.
Landfilling
2
2
Landfill design and operation regulated
under RCRA; controls include leachate
collection and methane recovery.
Rank 2:
Open Burning
10
10
Uncontrolled and unregulated combustion
emissions; possible releases from
combustion ash if managed on site.
Higher
exposure
potential -
uncontained
Air-curtain
Burning
10
10
Partially controlled but unregulated
combustion emissions, possible releases
from combustion ash if managed on site.
Burial
6
6
Uncontrolled leaching from unlined burial;
slow gas release to air.
releases to
the
environment
Compost
Windrow
6
6
Partially controlled releases from compost
windrow (minor leaching, runoff, and gas
release to air); where finished compost is

Compost
Application
2
1
tilled into soils, potential runoff and
erosion from amended soil.
a Higher number (10) indicates potential for higher exposure and risk and a low number indicates less potential
for exposure. The number of exposure pathways does not necessarily indicate the relative level of exposure
among the management options because the potential levels of exposure vary substantially by pathway.
Exposure rankings by management option are presented in Table 2.
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The top section of Table 2 shows that the Tier 1 assessment for chemicals did not rank the off-
site options relative to each other. In a Tier 2 assessment for the on-site management options,
potential exposures are ranked relative to one another for a hypothetical site, using a
standardized set of environmental conditions, assumptions about the scale of mortality, and
how the carcass management options are designed and implemented. Chemical and microbial
exposures are assessed independently due to fundamental differences in characteristics
influencing transport and fate and in their effects on human health and the environment.
For chemicals, Tier 2 rankings are based on a quantitative assessment in which different
methods are applied to estimate combustion releases to air and subsequent deposition to
ground level and to assess fate and transport in surface and subsurface soils, groundwater,
and an on-site lake. Exposures were assessed for humans breathing airborne chemicals and
ingesting chemicals in drinking water, home grown foods, and fish caught in the on-site lake.
Some options were not distinguishable from each other given data gaps and uncertainty in
modeling. Those options have, therefore, the same relative rank.
Table 2. Ranking of Livestock Carcass Management Options for Chemicals
Tier 1 Description
Management Option
Principal Rationale
The qualitative Tier 1
assessment distinguishes the off-
site options from the on-site
Off-site Rendering
Carcasses processed into useful
products; wastes released under
permits; availability decreasing.
options based on level of
regulatory control. The off-site
options are considered to pose
lower risk than the on-site
options, which have uncontrolled
environmental releases. The off-
site options are not ranked
relative to each other.
Off-site Landfill
Carcass leachate contained and
methane captured; landfills at
capacity are closed and new ones
built.
Off-site Incinerator
Destruction of materials; air
emissions are regulated; ash is
landfilled.
Tier 2 Description
Rankb
Management
Option
Principal Rationale

1
Compost
Windrow
Bulking material retains most
chemicals.
The quantitative Tier 2
assessment ranks the on-site
options relative to each other by
comparing ratio of estimated
exposures (from data on source
1
Burial
Soils filter out chemicals traveling
toward groundwater.
2
Air-curtain
burning
Similar release profiles; emissions
sensitive to type and quantity of
emissions and fate and transport
modeling) with toxicity reference
values (TRVs).
2
Open Pyre
burning
fuels used and burn temperature.
3
Compost
Application
If no offset from lake; mitigate with
offset and erosion controls.
b Rank 1 poses the lowest relative risk and higher numbers indicate higher relative risk.
In the Tier 2 assessment for microbes, three pathogenic microbes were evaluated to represent
prions, bacterial spores, and bacterial cells. For these microbes, all estimated exposures were
below available exposure benchmark values. However, because of significant uncertainty
about the initial concentration of the pathogenic microbes in healthy livestock, the Tier 2
rankings for microbes are based on the degree of thermal destruction and containment
provided by the carcass management options. These rankings assume prions could survive
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more management options than spores, and bacteria that do not form spores were most
susceptible to thermal inactivation. Thermal destruction can be applied as a criterion for both
the on-site and off-site options. Tables 3 and 4 show the microbial exposure rankings for Tier 1
and Tier 2, respectively. Although the on-site options are not ranked relative to the off-site
options, some will offer thermal destruction comparable to or greater than off-site options.
Table 3. Tier 1 Ranking of Off-site Livestock Carcass Management Options for Microbes
Tier 1 Description
Rankc
Management
Option
Principal Rationale
The qualitative Tier 1
assessment distinguishes the
H
Off-site
Incinerator
Thermal destruction of all microbes,
ash is landfilled
off-site options from the on-site
options based on level of
regulatory control. Among the
off-site options, rankings are
based qualitatively on the level
of thermal destruction. Off-site
M
Off-site
Rendering
Thermal inactivation of all microbes
except prions, workers protected
from prion exposure with the use of
personal protective equipment
(PPE).
options are not ranked relative to
on-site options, although some
will offer thermal destruction
comparable to or greater than
off-site options.
L
Off-site Landfill
Containment, including liner,
leachate collection, cover material,
but no thermal destruction; when
capacity is reached, landfill is
closed and new ones built.
Abbreviations: H = Highest rank; M = Middle rank; L = Lowest rank.
c Relative and absolute risks from microbial pathogens depends on initial concentrations in healthy
cattle, which is unknown.
Table 4. Tier 2 Ranking of On-site Livestock Carcass Management Options for Microbes
Tier 2 Description
Rankde
Management
Option
Principal Rationale
Rankings in the Tier 2
assessment are based on
quantitative exposure dose
1
Air-curtain
Thermal destruction of all microbes
2
Open Pyre
Thermal destruction of all microbes
except prions
estimates for a limited number of
exposure pathways. For those
pathways and the microbes
assessed, all estimated
exposure doses were below the
available IDso values for each
representative microbe (<7, 3-4,
3
Compost:
•	Windrow
•	Soil application
Thermal inactivation of most
microbes during windrow
decomposition phase, incomplete
activation of spore-forming
microbes and prions with some
decay/inactivation expected before
the application of finished compost
and ~ 1 order of magnitude
lower than the IDso for
Escherichia coii, Bacillus
anthracis, and prions,
respectively). Therefore, the
rankings reflect the extent of
thermal destruction.
4
Burial
No thermal inactivation of any
microbes, some decay expected
Abbreviations: IDso = infectious dose for 50 percent of the exposed population.
d Rank 1 poses the lowest relative risk and higher numbers indicate higher relative risk.
e Relative and absolute risks from microbial pathogens depends on initial concentrations in healthy
cattle, which is unknown; qualitative ranking is based on thermal destruction and containment.
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Uncertainties in the Exposure Assessment
Tables 5, 6, and 7 summarize three types of "uncertainties" in the exposure assessment:
•	Parameters with Moderate to High Natural Variation
•	Uncertain Parameter Values or Models
•	Simplifying Assumptions.
Table 5. Moderate to High Natural Variation in Parameter - Potential Bias from Selected
Values
Key Topic
Selected Parameter Value
Bias
Rationale
Natural Disaster Scenario
Scale of
Mortality
¦Mortality of 100 cattle at one farm with a
total weight of 50 tons to match the
environmental impact statement. Large-
scale mortalities could limit availability
of or access to resources.
Possibly High
Underestimate
¦ The scale of mortality is likely to be "small"
relative to mass mortalities for which
emergency measures at a state and federal
level would be required. In general, larger
mortalities result in greater potential
releases and exposures.
Site Setting and Environmental Conditions
Surface Water
¦ Hypothetical farm layout includes a
100-acre lake that is large enough to
support recreational or subsistence
fishing.
Variable
Overestimate
¦ Site design is likely to overestimate
exposure. In particular, exposure is
overestimated for sites without a fishable
pond or lake.
Groundwater
¦ Contaminants leached from the burial
trench, temporary storage pile, and
buried combustion residuals can reach
groundwater.
Variable
Overestimate
¦ The depth to an underground aquifer is
likely to be deeper than 1 m. Although the
domestic well exposure pathway is possible,
a domestic well is not likely to be shallow
enough to directly intersect leachate from
surface sources.
Meteorological
Conditions
¦ One year of meteorological data from a
weather station in Iowa, chosen to
represent a moderate climate in the
U.S. agricultural heartland.
Moderate
Over- or
Underestimate
¦ The meteorological data used for this
assessment could over- or underestimate
relevant conditions in other areas of the
country.
Soil Type and
Properties
¦ Recommended default soil properties
were chosen to reflect national
average conditions. Soil properties
influence how quickly leachate and
rainwater can flow through soils
vertically and how likely it is for
chemicals and microbes to sorb to soil
particles.
Moderate
Over- or
Underestimate
¦ Although the soil conditions were chosen to
represent national average conditions, sites
with different soils could have higher or
lower rates of vertical water movement and
capacity to adsorb chemicals or viruses.
Exposure Receptors and Estimation
Human
Receptors
¦ Exposures are assessed for three
types of farm residents: infants who
consume drinking water in their
formula, young children (age 1-2 years
old), and adults.
Neutral
¦ Although exposures might be over or
underrepresented for receptors or receptor
populations included in the assessment, the
approach includes a range of age
categories and is based on EPA exposure
assumptions.
Exposure
Factors
¦ Exposure factors (e.g., ingestion rates,
body weights) are mean values.
Neutral
¦ Means are used so that exposure is not
over or underestimated by this aspect of the
approach.
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Table 6. Uncertainty in Parameter Value(s) Selected
Parameter
Description
Uncertainty
Rationale for Uncertainty
Category
Natural Disaster Scenario

¦ Chemicals included in the assessment
were identified from relevant published
sources.

¦ Chemicals included in the assessment
Chemicals
Low
does not necessarily include all
potential chemicals of interest from
actual carcass management.
Microbial Agents
¦ Microbial agents included microbes
present in healthy livestock. Among
those three representative agents were
selected for exposure estimation:
prions, Bacillus anthracis, and £ coli
0157:H7.
Low
¦ The three microbial agents were
selected to represent three organisms
with three distinct characteristics (e.g.,
persistence). Exposures for various
organisms may be over or under
estimated.
Carcass Management Options
Combustion Fuels
¦ Types and amounts of fuels affect the
composition and amounts of emissions
to air and combustion residuals.
Moderate
¦ Combustion fuel assumptions could
contribute to over or underestimation of
exposure.
Ash Disposal
¦ Combustion ash is managed on site,
buried in place using in the assumed
length and width of the combustion
units.
High
¦ Exposures are overestimated if
combustion ash is not disposed of on
site.
Releases and Release Rates
Releases
Estimates
¦ Data to characterize the composition,
quantity, and rate of releases are very
limited.
High
¦ Actual releases can vary significantly
due to many factors (e.g., unit design,
environmental conditions).
Animal Vectors
¦ Chemicals or microbes can be
transported by insects, birds, or
mammals that come in contact with
carcasses before or during
management. Quantitative evaluation
of animal vectors not included.
Moderate
¦ Exclusion of animal vectors from the
assessment causes potential
exposures to be underestimated. This
uncertainty impacts the composting
option more that burial or the
combustion-based options.
Fate and Transport Modeling
Models
¦ Various screening-level models and
calculations to estimate chemical fate
and transport through air, water, soil,
and terrestrial and aquatic food chains.
High
¦ Data and methods can individually
contribute to estimation of exposures.
Usage of conservative assumptions
and approaches likely result in over-
estimates of possible exposures.
Chemical
Properties and
Other Inputs
¦ Modeling uses various chemical
properties and numerical inputs (e.g.,
soil properties, food web composition).
Moderate
¦ Uncertainties might be present in input
parameters. Many modeling inputs
generally uses central-tendency
values.
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Table 7. Simplifying Assumptions - Effects on Exposure Estimates
Key Topic
Simplifying Assumption
Effect
Rationale for Effect
¦ Natural Disaster Scenario
Type of
Livestock
Affected
¦ Any livestock type can suffer mortalities from
natural disasters. Body size ranges from small
to large and animal density varies with farming
practices. Livestock species differ in terms of
body composition, which can affect combustion
temperature and residual materials and affect
rate of decomposition for other options.
Moderate Over-
or Underestimate
¦ Body composition varies among
species, but variability is limited
by the general similarity in
warm-blooded vertebrate
bodies.
¦ Site Setting and Environmental Conditions
Site Layout
¦ Conceptual models and site layout were
designed to include all feasible complete
exposure pathways.
Moderate
Overestimate
¦ Overestimate exposure as the
layout assumes a worst-case
exposure for each possible
pathway.
Carcass Management Options
Off-site Carcass
Management
Options
¦ Off-site carcass management facilities comply
with applicable regulations and that those
regulations are protective of human health and
the environment.
Low
Underestimate
¦ Underestimated where the
facilities do not comply with
applicable regulations.
Design of On-
site
Management
Units
¦ Design of on-site management options are
based on 50 short tons of carcasses. For larger
mortalities, the spatial pattern and nature of
environmental releases could be different.
Moderate Over-
or
Underestimates
¦ Carcass management units
could lead to over- or
underestimation of exposure.
Carcass
Handling Before
Management
¦ Workers who handle livestock carcasses are
assumed to use recommended personal
protective equipment (PPE).
Moderate
Underestimate
¦ Exposure to workers is
underestimated if no PPE is
used.
Temporary
Storage Pile
¦ Carcasses are stored in a pile on bare earth for
48 hours during preparations for further
management.
Moderate Under-
or Overestimates
¦ If animals are in the temporary
pile for more time, exposures
from the storage pile are
underestimated and exposures
from subsequent management
are overestimated (and vice
versa).
Carcass
Transportation
¦ Exposures due to carcass transportation are
considered insignificant and are not used in
ranking the carcass management options.
Low
Underestimate
¦ If carcass transportation results
in a significant exposure, the
assessment underestimates
overall exposure.
Fate and Transport Modeling
Runoff from
Compost
Application
¦ Application site is immediately adjacent to the
lake.
High
Overestimate
¦ Overestimates runoff to the lake
and human exposure to any
metals in the compost.
Exposure Receptors and Estimation
Homegrown
farm Products
¦ Farm residents are assumed to consume only
home-grown products.
Moderate
Overestimate
¦ Farm residents also rely on
store-bought foods.
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Conclusions
Off-site options, including incineration, landfilling, and rendering, are subject to air, water, and
solid waste regulations designed for adequate health and environmental protection. This
assessment finds that, when properly designed and implemented, the four on-site carcass
management options as well as the off-site options are unlikely to cause adverse health or
environmental effects.
The Tier 2 assessment provides a scientifically based understanding of the relative
contribution of specific exposure pathways, hazardous agents, and steps in carcass
management processes. These insights can assist selection of environmentally protective
livestock carcass management methods in the event of a natural disaster. The assessment
also can aid selection and priority setting for mitigation and best management practices to
assist State regulators and communities to prevent, prepare for, respond to, and recover from
emergencies. The overall outcome of exposure assessments will help development of a
decision tool to support selection of management methods in times of emergencies by
providing scientifically-based information on potential hazards to human health, livestock,
wildlife, and the environment.
Additional Information
U.S. EPA. Exposure Assessment of Livestock Carcass Management Options During Natural
Disasters. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-17/027, 2017
(URL: https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryld=335655)
Contact information
For more information, visit the EPA Web site at http://www2.epa.gov/homeland-securitv-
research
Technical Contact: Sandip Chattopadhyay, Ph.D. (chattopadhvav.sandip@epa.gov)
General Feedback/Questions: Kathy Nickel (nickel.kathv@epa.gov)
U.S. EPA's Homeland Security Research Program (HSRP) develops products based on scientific research and
technology evaluations. Our products and expertise are widely used in preventing, preparing for, and recovering
from public health and environmental emergencies that arise from terrorist attacks or natural disasters. Our
research and products address biological, radiological, or chemical contaminants that could affect indoor areas,
outdoor areas, or water infrastructure. HSRP provides these products, technical assistance, and expertise to
support EPA's roles and responsibilities under the National Response Framework, statutory requirements, and
Homeland Security Presidential Directives.
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