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technical BRIEF
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Review of Bacillus anthracis (Anthrax) Studies for
Dose-Response Modeling to Estimate Risk
INTRODUCTION
Bacillus anthracis, the causative agent of
inhalation anthrax, is one of the most highly
studied biological threat agents (Wilkening
2006), yet consensus is still lacking on an
appropriate dose-response relationship to
describe the human health effects from low
dose exposures (Taft and Mines 2012). Dose-
response relationships can be an important
element in the development of protective
actions and decontamination strategies after a
bioterrorism event (Executive Office of the
President 2009). For example, dose-response
relationships can assist in the identification of
environmental concentrations where protective
actions may be necessary to arrest the development of inhalation anthrax in exposed
individuals.
A commonly cited dose-response number is the infectious dose that could cause illness in 50%
of the exposed population (ID50). Unfortunately, due to the very high mortality associated with
inhalational anthrax, there are no dose-response data available to estimate any anthrax specific
infectious doses such as the ID50(Leffel and Pitt 2006). There are dose-response studies in the
literature that report anthrax lethal doses such as the lethal dose that could cause death in 50%
of the exposed population (LD50). However, all of the reported lethal dose-response data come
from experimental animal exposure studies because there are no human dose-response data in
the available literature. Even for those limited events where inhalation anthrax has been
diagnosed (e.g., occupational settings in animal hair mills, 2001 anthrax letters event,
Sverdlovsk accidental release (Wilkening 2006)), there were no corresponding environmental
dose-response data collected as part of the epidemiological investigation.
This technical brief identifies current challenges in the development of a B. anthracis dose-
response relationship specifically for low dose exposures, summarizes available dose-response
data sets for inhalation exposures in commonly used animal models and observational data
gathered from human epidemiological studies, and assesses the usability of the identified dose-
response data sets for modeling low dose exposures.
U.S. Environmental Protection Agency
Office of Research and Development, Homeland Security Research Program
EPA/600/S-12/681
October 2012
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REVIEW OF AVAILABLE DOSE-RESPONSE DATA SETS FOR MODELING LOW
DOSE EXPOSURES
To support the development of a B. anthracis dose-response relationship for low dose
exposures, a review of published or other open-source reports containing B. anthracis inhalation
lethality dose-response data from acute exposure studies (i.e., exposures of one 24-hour period
or less) of the guinea pig (Table 1), rabbit (Table 2), and nonhuman primate (Table 3) were
conducted. No human dose-response data were identified for acute B. anthracis exposure. Data
from lethality dose-response studies using multiple dose exposures (i.e., more than one dose in
an exposure period greater than 24 hours) were also identified for guinea pig, rabbit, and
nonhuman primate receptors; observational data from epidemiological studies of multiple dose
exposures in an occupational setting were found for humans (Table 4).
The primary purpose of this evaluation was to identify published, open source dose-response
data sets and provide a preliminary assessment of their data usability for modeling low dose 6.
anthracis exposures. Dose-response data were included in these tables if (1) dose-response
data and/or summary statistics (i.e., LD50) were reported, and (2) dose and response were
concurrently measured and reported from the same study population. Tables identify the study
authors and year of publication, study details, and an assessment of the data usability for
modeling low dose exposures. The "Highest Dose or Highest Dose Group without Reported
Death" column identifies the reported dose that represents the highest dose for which no
individual in the identified dose group or lower dose groups were reported to have died from the
tested (animal) or observed (human) exposure. If data were reported on an individual basis, the
column identifies the highest reported dose for which no individual died at that dose or lower
dose levels. The identified doses are not analogous to a No Observable Adverse Effect Level
(i.e., NOAEL) as adverse effects other than death can occur with B. anthracis exposure and
were not captured when lethality was the only measure of effect.
Dose-response data must have included a measure of environmental air concentration or
inhalation dose; dose data that were derived from modeled estimates of air concentration data
(e.g., Meselson et al. 1994) were not included. Re-analyses of previously published data were
also not included in these data tables (e.g., Haas 2002, Bartrand et al. 2008).
Data usability for modeling low dose exposures was assessed by the development of a data
usability score for each dose-response data set or summary statistic reported from the identified
publication. Data usability scores were assigned into one of three categories: high data usability
identified by green shading in the data usability cell of the table, medium data usability identified
by yellow shading, and low data usability identified by red shading. Figure 1 identifies the
scoring questions and describes the process to assign the data usability for modeling low dose-
exposures. Scores were assessed using only published data. It is important to recognize that
studies that received a low data usability score in this assessment may be of very high quality
relative to their originally intended purpose. However, the data usability score presented here is
an assessment of the applicability of the published data specific to modeling low dose
exposures to support site-specific risk-based decisions.
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To Develop Data Usability for Modeling Low Dose Exposures Rating:
Assign one point for each question that can be answered "yes" for the identified data set and/or reported
summary statistic and identify rating based on numerical score and answers to specific questions that trigger
an automatic usability rating.
1) Are dose-response raw data available?
2) Are particle size distribution data or identification of single spore particles reported based on
measurements during testing?
3) Are there dose groups with a less than a 50% lethality rate or is there an overall lethality rate of less 50% is
doses reported for individuals?
4) Were real-time methods used during the exposures to derive inhalation rates?
5) Is the dose group number (n > 5) or total number tested for individual dose measurements (n > 12)
sufficient for dose-response modeling?
Data Usability
Rating for Modeling Low Dose
Exposures
Question Answers that Automatically
Assign Usability Rating for Modeling
Low Dose Exposures
Not Applicable
Not Applicable
Numerical Score for Usability for
Modeling Low Dose Exposures
3 or 4
Figure 1. Scoring system to assign data usability score for modeling low dose
exposures.
GUINEA PIG DOSE-RESPONSE STUDIES
There were no identified guinea pig dose-response studies that were assigned a high data
usability score for modeling low dose exposures (Table 1). The primary areas of weakness were
a lack of identified particle size (e.g., Altboum et al. 2002; Barnes 1947), a lack of real-time
methods to derive inhalation rates (e.g., use of allometric equation to estimate inhalation rate in
Druett et al. 1953), or a lack of dose information (e.g., Barnes 1947; Day et al. 1962; Young et
al. 1946). As part of earlier efforts to evaluate available guinea pig dose-response data, the
U.S. Environmental Protection Agency's (EPA) National Homeland Security Research Center in
conjunction with the US Army Public Health Command developed the Pathogen Information
Catalog (PI-CAT) (EPA 2009) to compile unclassified data for selected biological threat agents.
A report was generated that evaluated PI-CAT data for the guinea pig and a conducted a
benchmark dose analysis of selected data sets (EPA 201 Oa).
RABBIT DOSE-RESPONSE STUDIES
Two studies conducted by EPA (2011 and 2012) that were designed to develop dose-response
data for modeling low dose exposures were the only studies receiving a high data usability
rating for the rabbit animal model (Table 2) for the purpose of this evaluation. The majority of the
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identified studies received a medium to low data usability score for modeling low dose exposure
because the dose-response data were control group data with no survivors (e.g., Little et al.
2004, Pitt et al. 2001) or doses were not reported specific for dose groups or individuals (e,g,
Barnes 1947, Zaucha etal. 1998).
NONHUMAN PRIMATE DOSE-RESPONSE STUDIES
There was one published nonhuman primate study (Lever et al. 2008) that received a high
usability data rating (Table 3). The main reasons for lower data usability ratings for the other
identified studies were a lack of reported doses for dose groups or individuals (e.g., Estep et al.
2003; Ivins et al. 1998; Vasconcelos et al. 2003; Young et al. 1946) or a lack of reporting of the
particle size distribution (e.g, Rossi et al. 2008; Twenhafel et al. 2007). Druett et al. (1953)
received a medium data usability rating because the inhalation rates were only derived from
allometric equations. A number of these reported dose-response data sets originated from
studies designed to evaluate pathology of inhalation anthrax (e.g., Twenhafel et al. 2007;
Vasconcelos et al. 2003) or efficacy of medical countermeasures (e.g., Friedlander et al. 1993;
Ivins et al. 1998). By design, many of these studies would not be expected to produce data sets
with the necessary characteristics to assess dose-response relationships, especially for
modeling low dose exposures needed to support risk-based site-specific decision making.
Given the limited published data of high usability for modeling low dose exposures for the
nonhuman primate, the PI-CAT (EPA 2009) was again queried for available data. Additional
data sets were identified and evaluated for development of dose-response relationships
specifically for low dose exposures; the outputs of this modeling were published (EPA 201 Ob;
Taft and Mines 2012). However, the two dose-response data sets that were also reported in
EPA (201 Ob) and Taft and Mines (2012) did not include identification in the publications of dose-
response raw data due to distribution limitations maintained by the originators of the data.
MULTIPLE EXPOSURES DOSE-RESPONSE STUDIES
There were considerably fewer dose-response data sets published describing multiple dose
exposure to B. anthracis for observations in human and animal dose-response data (Table 4).
The EPA's (2012) multiple dose rabbit study was assigned a high data usability rating for
modeling low dose exposures. The remaining identified studies were all assigned low data
usability ratings due to a lack of sufficient individuals tested (e.g., Albrink and Goodlow 1959;
Dahlgren et al. 1960) or a lack of real-time methods to derive inhalation rates (e.g., Albrink and
Goodlow 1959; Brachman et al. 1966; Dahlgren et al. 1960). One study identifying human
exposure data for a multiple dose exposure to B. anthracis was identified (Dahlgren et al. 1960)
and included in Table 4. This epidemiological study reported B. anthracis air concentrations
over a two-day period and the lack of inhalation anthrax observed in exposed workers was
noted. However, data interpretation is complicated by the fact that approximately 30% of the
exposed individuals were vaccinated at the time of the testing in one mill and 100% vaccinated
in the second mill. The study was rated low data usability because of the low number of
individuals exposed and a lack actual individual exposure doses and inhalation rates.
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SUMMARY
The reported experimental animal anthrax lethal dose-response data in the literature are highly
variable with the LD50s ranging from 102 to 106. Historically, the animal exposure studies were
conducted to assess weapons potential or to test the effectiveness of countermeasures such as
antibiotics or vaccines. Therefore, these studies were often conducted with one-time (acute)
exposure at very high doses, which makes them less applicable for estimating the potential
human health risk posed by repeated exposures at low doses. Different techniques are
required to most accurately extrapolate animal lethal doses to corresponding human
consequences. The technique that is required depends on the animal model used and whether
dose estimates were derived from environmental concentrations, inhaled doses, intranasal
administrations, and/or different exposure durations. It is therefore critical to evaluate what the
reported historical literature dose numbers actually represent and how they were derived, as
well as the limitations for the intended application.
The methods used for the experimental animal inhalation exposure study have advanced
significantly, and recent dose-response studies using these contemporary techniques are more
applicable for modeling low dose exposures and estimating potential human health risks.
However, there has been only one recent applicable study that evaluated the dose-response of
repeated low doses of B. anthracis. Additional dose-response studies targeting repeated
exposures are still needed before the potential risk posed by repeated exposure to residual
spores following anthrax contamination events can be adequately addressed.
Overall, the differences in reported experimental methodologies, strain virulence, host
susceptibilities, and uncertainties extrapolating animal data to humans make the selection of
one specific lethal dose or infectious dose number nearly impossible. Until adequate dose-
response studies targeting repeated low doses are conducted, quantifying risks of exposure to
B. anthracis is hampered by the lack of sufficient dose response data.
LIST OF TABLES
Table 1. Available Dose-Response Data for Acute Exposure of the Guinea Pig 7
Table 2. Available Dose-Response Data for Acute Exposure of the Rabbit 11
Table 3. Available Dose-Response Data for Acute Exposure of the Nonhuman Primate 13
Table 4. Available Dose-Response Data for Multiple Dose Exposures of Guinea Pigs, Rabbits,
Nonhuman Primates, and Humans 17
CONTACT INFORMATION
For more information, visit the EPA Web site at www.epa.gov/nhsrc
Technical Contact: Sarah Taft (taft.sarah@epa.qov)
General Feedback/Questions: Kathy Nickel (nickel.kathv@epa.gov)
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If you have difficulty accessing this PDF document, please contact Kathy Nickel
(Nickel.Kathy@epa.gov) or Amelia McCall (McCall.Amelia@epa.gov) for assistance.
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Table 1. Available Dose-Response Data for Acute Exposure of the Guinea Pig
Author and
Year
Altboum et
al. 2002
Barnes
1947
Druett et
al. 1953
Strain and
Particle Size
Vollum,
Particle Size
Not Reported
ATCC 6605,
Particle Size
Not Reported
Strain Not
Reported, 98%
Single Spore
Particles
M36 (Vollum),
Single Spore
Particles
M36 (Vollum),
3.5 [im
Particles
Doses Tested (Units)
2 x 107 CPU
2xl06CFU
2 x 105 CPU
2 x 104 CPU
2 x 103 CPU
2 x 102 CPU
3 x 106 CPU
3 x 105 CPU
3 x 104 CPU
3 x 103 CPU
3 x 102 CPU
3 x 10 CPU
7.5xl05Spores/l
6.56 xio5 Spores/I
7.05 xio5 Spores/I
0.168 x 106 Single Spores - minutes/I*
0.346 x 106 Single Spores - minutes/I
0.646 x 106 Single Spores - minutes/I
1.000 x 106 Single Spores - minutes/I
0.26 x 106 Organisms - minutes/I
0.44x10 Organisms- minutes/I
0.17x10 Organisms- minutes/I
0.29 x 106 Organisms - minutes/I
0.44x10 Organisms- minutes/I
0.52x10 Organisms- minutes/I
0.69x10 Organisms- minutes/I
Number per
Dose Group
8
9
20
32
40
40
20
20
20
20
20
LD50 Reported
for Study Data
(95% Confidence
Limit)
4 x 104 CPU
8 x 104 CPU
Not Reported
0.34 xio6 Single
Spores —
minutes/I
0.36 x 106
Organisms -
minutes/I
Highest Dose or
Highest Dose
Group Without
Reported Death
2xl03CFU
3x10 CPU
Lethality in All
Tested Dose Groups
Lethality in All
Tested Dose Groups
Lethality in All
Tested Dose Groups
Reported as
Environmental
Concentration,
Inhaled Dose, or
Intra nasal
Administration
Intranasal
Administration
Environmental
Concentration
Environmental
Concentration
Environmental
Concentration
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
Medium: Particle
size not reported
based on
measurement,
Lack of real-time
methods to
derive inhalation
rates
Medium: Particle
size not reported
based on
measurement,
Lack of real-time
methods to
derive inhalation
rates
Medium: Lack of
real-time
methods to
derive inhalation
rates
Medium: Lack of
real-time
methods to
derive inhalation
rates
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Author and
Year
Druett et
al. 1953
Strain and
Particle Size
M36 (Vollum),
M36 (Vollum),
8 |am Particles
M36 (Vollum),
12 |am
Particles
M36 (Vollum),
3.6 [im
Particles with
18 Spores per
Particle
M36 (Vollum),
8.4 |am
Particles with
19 Spores per
Particle
M36 (Vollum),
11.6 [im
Particles with
Doses Tested (Units)
0.597 x 106 Organisms - minutes/I
0.269 x 106 Organisms - minutes/I
0.374 x 106 Organisms - minutes/I
0.125 x 106 Organisms - minutes/I
1.025 x 106 Organisms - minutes/I
1.34 x 106 Organisms - minutes/I
0.385 x 106 Organisms - minutes/I
0.231 x 106 Organisms - minutes/I
7.32 x 106 Organisms - minutes/I
2.28 x 106 Organisms - minutes/I
3.39 x 106 Organisms - minutes/I
4.78x10 Organisms- minutes/I
1.72 x 10 Organisms - minutes/I
3.16x10 Organisms- minutes/I
12.19 x 106 Organisms - minutes/I
2.84x10 Organisms- minutes/I
1.87x10 Organisms- minutes/I
5.8x10 Organisms- minutes/I
12.8 x 106 Organisms - minutes/I
7.65 x 106 Organisms - minutes/I
1.66 x 106 Organisms - minutes/I
1.39 x 106 Organisms - minutes/I
1.1 x 106 Organisms - minutes/I
Number per
Dose Group
40
40
ACl
40
LD50 Reported
for Study Data
(95% Confidence
Limit)
6
0.49 x 10
3.8 x 106
Organisms —
5.7xl06
Organisms -
minutes/I
Note: Used
recalculated
results for Table
8.
Not Reported
Highest Dose or
Highest Dose
Group Without
Reported Death
Lethality in All
Lethality in All
Tested Dose Groups
Lethality in All
Tested Dose Groups
Lethality in All
Tested Dose Groups
Reported as
Environmental
Concentration,
Inhaled Dose, or
Intra nasal
Administration
Environmental
Concentration
Environmental
Concentration
.
Environmental
Concentration
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
Medium: Lack of
real-time
real-time
methods to
Medium: Lack of
real-time
methods to
derive inhalation
rates
Medium: Lack of
real-time
methods to
derive inhalation
rates
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Author and
Year
Barnes
1947
Brachman
etal. 1960
Day et al.
1962
Strain and
Particle Size
18 Spores per
Particle
Strain Not
Reported, 98%
Single Spore
Particles
Strain and
Particle Size
Not Reported
V1B, Particle
NMD 2. 5 |am
NH6, Particle
NMD 2.5 |am
Doses Tested (Units)
Not Reported
Not Reported
Number per
Dose Group
Not Reported
Not Reported
6 to 10
Animals
6 to 10
Animals
LD50 Reported
for Study Data
(95% Confidence
Limit)
370,000 Spores
50,000 Inhaled
Spores
6.5 x 102 Spores
(3.9xl02tol.3x
104 Spores)
5.8x 104 Spores
(3.6xl04to2.1x
105 Spores)
9.8 x 103 Spores
(5.5xl03to2.1x
104 Spores)
3.0 x 103 Spores
(2.2xl02to4.2x
104 Spores)
4.4x 104Spores
(1.3xl04tol.5x
105 Spores)
5. Ox 104Spores
(3.1xl04to8.1x
104 Spores)
Highest Dose or
Highest Dose
Group Without
Reported Death
Not Reported
Not Reported
Reported as
Environmental
Concentration,
Inhaled Dose, or
Intra nasal
Administration
Inhaled Dose
Inhaled Dose
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
Low: Dose-
response raw
data not
reported, Lack of
real-time
methods to
derive inhalation
rates
Low: Dose-
response raw
data not
reported, Particle
size not based on
measurement
Low: Dose-
response raw
data not
reported, Lack of
real-time
methods to
derive inhalation
rates
Low: Dose-
response raw
data not
reported, Lack of
real-time
methods to
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Author and
Year
Young et al.
1946
Strain and
Particle Size
Detrick25,
Single Spore
Particles
Doses Tested (Units)
Not Reported
Number per
Dose Group
16
LD50 Reported
for Study Data
(95% Confidence
Limit)
7. Ox 104Spores
(3.9xl04tol.2x
105 Spores)
3.8x 104Spores
(1.7xl04to6.8x
104 Spores)
19 x 104 Spores/I
Highest Dose or
Highest Dose
Group Without
Reported Death
Not Reported
Reported as
Environmental
Concentration,
Inhaled Dose, or
Intra nasal
Administration
Environmental
Concentration
(5-Minute
Exposure)
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
derive inhalation
rates
Low: Dose-
response raw
data not
reported, Lack of
real-time
methods to
derive inhalation
rates
Druett et al. (1953) uses the term "dosage" (Nt) to describe the product of environmental concentration and period of exposure (e.g., Nt x 10" = 0.168); for ease in reading
table, this term has been recorded as Nt (e.g., 0.168 x 106)
CPU - Colony forming unit
I - Liter
LD50- Lethal Dose for 50% of the Tested Population
NMD - Number Median Diameter
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Table 2. Available Dose-Response Data for Acute Exposure of the Rabbit
Author and
Year
U.S.
Environmental
Protection
Agency 2011
Barnes 1947
Little etal.
2004
Pitt etal. 2001
Strain and
Particle Size
Ames, MMAD
(GSD) for Each
Dose Group
0.96 |am (1.33),
0.82 |am (1.48),
0.92 |am (1.57),
0.87 |am (1.59),
1.12 |am (1.33),
and 1.12 |am
(1.31),
Respectively
Strain Not
Reported, 98%
Single Spore
Particles
Ames, Particle
Size Not
Reported
Ames, Particle
Size of MMAD
1.2 |am
Doses Tested (Units)
2.00 CFU/animal
2.86xl02CFU/animal
2.06 xio3 CFU/animal
2. 54 xio4 CFU/animal
2. 75 xio5 CFU/animal
8.27 xio6 CFU/animal
Not Reported
Compilation of 4 Separate
Experiments with Reported Average
Doses Not Distinguished Between
Control and Treatment Groups,
166.2 + 95.77 (Mean + SD) x LD50,
467.4 + 379.7 (Mean + SD) x LD50,
156.7 + 97.5 (Mean + SD) x LD50,
228.7 + 106.0 (Mean + SD) x LD50
where LD50= 1.1 x 105 Spores
Average Dose of
269.4 + 258.9 (Mean + SD) x LD50
where LD50= 1.1 x 105 Spores
Reported Average Dose for Both
Control and Treatment Groups of
133 + 51 (Mean + SD) x LD50 where
LD50 = 1.1 x 105 Spores
Number
per Dose
Group
5
Not
Reported
31
8
8
LD50 Reported
for Study Data
(95%
Confidence
Limit)
5.18xl04CFU
(95% Fieller's
Confidence
Interval, 6.14x
103 CFU to 7.27
x!05CFU)
600,000 Spores
Not Calculable
Not Calculable
Highest Dose or
Highest Dose
Group Without
Reported Death
2.06 x 10s CFU
Not Reported
No Survivors in
Control Groups
No Survivors in
Control Groups
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Inhaled Dose
Inhaled Dose
Inhaled Dose
Data Usability for
Modeling Low Dose
Exposures (Red,
Yellow, or Green
and Reason(s) for
Rating)
High: All data
usability elements
present
Low: Dose-response
raw data not
reported, Lack of
real-time methods
to derive inhalation
rates
Low: Dose-response
raw data not
reported, Lack of
real-time methods
to derive inhalation
rates, 100%
lethality
Low: Dose-response
raw data not
reported, Lack of
real-time methods
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Author and
Year
1998
Strain and
Particle Size
Strain and
Particle Size Not
Reported
Doses Tested (Units)
Reported Average Dose for Both
Control and Treatment Groups of 84
+ 42(Mean+SD)xLD50
where LD50 = 1.1 x 105 Spores
Not Reported
Number
per Dose
Group
10
Not
Reported
LD50 Reported
for Study Data
(95%
Confidence
Limit)
1.05 x 105 CPU
Highest Dose or
Highest Dose
Group Without
Reported Death
Not Reported
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Data Usability for
Modeling Low Dose
Exposures (Red,
Yellow, or Green
and Reason(s) for
Rating)
to derive inhalation
rates, 100%
lethality
Low: Dose-response
raw data not
reported, LD50
reported for
different data set
than discussed in
publication
CPU - colony forming unit
GSD - Geometric Standard Deviation
[im- micron
LD50 - Lethal Dose for 50% of the tested population
MMAD - Mass Median Aerodynamic Diameter
SD-Standard Deviation
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Table 3. Available Dose-Response Data for Acute Exposure of the Nonhuman Primate
Author and
Year
Lever et al.
2008
Druett et al.
1953
Twenhafel et
al. 2007
Strain, Particle
Size, and
Animal Model
Ames, Particle
Size in the 1 to 3
[im Range,
Marmoset
M36 (Vollum),
Single Spore
Particles, Rhesus
Macque
M36 (Vollum),
12 [im Particles,
Rhesus Macque
Ames, Particle
Size Not
Doses Tested (Units)
1.9 x 105 CPU
l.lx!05CFU
1.4 x 105 CPU
1.6 x 104 CPU
1.5 x 104 CPU
1.2 x 104 CPU
2.4 x 104 CPU
3.7 x 103 CPU
2.5 x 103 CPU
2.3 x 102 CPU
4.2 x 102 CPU
1.4 x 101 CPU
0.0293 x 106 Single Spores - minutes/I
0.0321 x 106 Single Spores - minutes/I
0.0453 x 106 Single Spores - minutes/I
0.0573 x 106 Single Spores - minutes/I
0.0648 x 106 Single Spores - minutes/I
0.0670 x 106 Single Spores - minutes/I
0.1000 x 106 Single Spores - minutes/I
0.1250 x 106 Single Spores - minutes/I
0.1660 x 106 Single Spores - minutes/I
0.251 x 106 Organisms - minutes/I
0.320 x 106 Organisms - minutes/I
0.422 x 106 Organisms - minutes/I
0.615 x 106 Organisms - minutes/I
0.682 x 106 Organisms - minutes/I
1.760 x 106 Organisms - minutes/I
3.310 x 106 Organisms - minutes/I
3.74 x 106 Organisms - minutes/I
204 CPU
2.2 x 103 CPU
Number
per Dose
Group
1
8
8
8
8
8
8
7
6
8
1
LD50 Reported
for Study Data
(95%
Confidence
Limit)
1.47 x 103 CPU
(7.19 to 2. 95 x
105CFU)
0.045 x 106
Single Spores -
minutes/I
Not Calculable
Highest Dose or
Highest Dose
Group Without
Reported Death
1.4x10^11
Lethality at All
Tested Dose
Levels
Lethality in
Lowest Tested
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Environmental
Concentration
Inhaled Dose
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
High: All data
usability elements
present
Medium: Lack of
real-time methods
to derive
inhalation rates
Medium: Particle
size not reported
-------
Author and
Year
Albrinkand
Goodlow
1959
Glassman
1966
Brachman et
al. 1960
Estep et al.
2003
Strain, Particle
Size, and
Animal Model
Reported,
African Green
Monkey
Vollum
Particle Size
Ranged from
1.05 to 1.4
NMD,
Chimpanzee
Strain Not
Reported,
Particle Size
Reported to be
< 5 |am,
Cynomolgus
Monkey
Strain and
Particle Size Not
Reported,
Unspecified
Monkey
Ames,
Cumulative
Doses Tested (Units)
3.2 x 103 CPU
4.9 x 103 CPU
5.5 x 103 CPU
9.8 x 103 CPU
2.2 x 104 CPU
2.6 x 104 CPU
2.8 x 104 CPU
3.5 x 104 CPU
9.8 x 106 CPU
1.0 x 107 CPU
32,800 Viable Spores
34,350 Viable Spores
39,700 Viable Spores
66,500 Viable Spores
Not Reported
Not Reported
Not Reported
Number
per Dose
Group
1
Not
Reported
Not
Reported
Not
Reported
LD50 Reported
for Study Data
(95%
Confidence
Limit)
Not Reported
4,130 Spores
(95%
Confidence
Interval of
1,980 to 8,630
Spores)
6,000 Inhaled
Spores
10,900 CPU
(Fieller's95%
Highest Dose or
Highest Dose
Group Without
Reported Death
Individual Dose
of 204 CPU
34,350 Viable
Spores
Not Reported
Not Reported
Not Reported
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Inhaled Dose
Inhaled Dose
Inhaled Dose
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
based on
measurement,
Lack of real-time
methods to derive
inhalation rates
Low: Number of
total individuals
from which dose
measurements
were obtained
less than 12, Lack
of real-time
methods to derive
inhalation rates
Low: Dose-
response raw data
not reported, Lack
of real-time
methods to derive
inhalation rates
Low: Dose-
response raw data
not reported,
Particle size not
reported based on
measurement
Low: Dose-
response raw data
-------
Author and
Year
Friedlander et
al. 1993
Ivins et al.
1996
Ivins et al.
1998
Rossi et al.
2008
Strain, Particle
Size, and
Animal Model
MMAD for Both
Strains 1.31 mm
[sic] and GSD of
1.8, Rhesus
Macaque
Vollum,
Cumulative
MMAD
Collectively for
Both Strains
1.31 mm [sic]
GSD of 1.8,
Rhesus
Macaque
Vollum,
MMAD
1.2 [im, Rhesus
Macque
Ames, Particle
Size Not
Reported,
Rhesus Macque
Ames, Particle
Size Not
Reported,
Rhesus Macque
Ames, Particle
Size Not
Doses Tested (Units)
Not Reported
4.0 + 1.6 x 105 (Mean + SD) Spores
Not Reported
93 + 63 (Mean + SD) x LD50 where LD50
= 5.5 x 104 Spores
210,000 CPU
210,000 CPU
Number
per Dose
Group
Not
Reported
10
Not
Reported
3
LD50 Reported
for Study Data
(95%
Confidence
Limit)
Confidence
Interval of
1,320 to
241,000)
6,750 CPU
(Fieller's95%
Confidence
Interval of 21
to 116,000)
Not Reported
5.5 x 104
Spores
Not Calculable
(l.lx!04CFU
LD50 reported
Highest Dose or
Highest Dose
Group Without
Reported Death
Not Reported
9/10 Control
Animals Died
Not Reported
No Survivors in
Control Group
Lethality at All
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Inhaled Dose
Inhaled Dose
Inhaled Dose
Inhaled Dose
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
not reported
Low: Dose-
response raw data
not reported
Low: Dose-
response raw data
not reported, Lack
of real-time
methods to derive
inhalation rates
Low: Dose-
response raw data
not reported, LD50
reported for
different data set
than discussed in
publication
Low: Dose-
response raw data
not reported, Lack
of real-time
methods to derive
inhalation rates
Low: Total
number of
-------
Author and
Year
Vasconcelos
eta 1.2003
Young et al.
1946
Strain, Particle
Size, and
Animal Model
Reported,
African Green
Monkey
Ames, Particle
Size Between 1
and 2 |am
MMAD,
Cynomolgus
Monkey
Detrick 25,
Single Spore
Particles,
Unspecified
Monkey
Doses Tested (Units)
520,000 CPU
630,000 CPU
750,000 CPU
11,200,000 CPU
12,800,000 CPU
15,900,000 CPU
18,900,000 CPU
Not Reported
Not Reported
Number
per Dose
Group
14 Total
Animals
16
LD50 Reported
for Study Data
(95%
Confidence
Limit)
for different
data set than
discussed in
publication)
61,800 CPU
(95%
Confidence
Interval of
34,000 to
110,000)
20 xlO4 Spores
Highest Dose or
Highest Dose
Group Without
Reported Death
Tested Dose
Levels (1 Survivor
and 1 Death at
210,000 CPU)
Not Reported
Not Reported
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Environmental
Concentration
(5-Minute Exposure)
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
animals tested
less than 12,
Particle size not
reported based on
measurement,
Lack of real-time
methods to derive
inhalation rates
Low: Dose-
response raw data
not reported, Lack
of real-time
methods to derive
inhalation rates
Low: Dose-
response raw data
not reported, Lack
of real-time
methods to derive
| inhalation rates
Druett et al. (1953) uses the term "dosage" (Nt) to describe the product of environmental concentration and period of exposure (e.g., Nt x 10"6 = 0.168); for ease in reading
table, this term has been recorded as Nt (e.g., 0.168 x 106)
CPU - colony forming unit
GSD - Geometric Standard Deviation
I - Liter
LD50- Lethal Dose for 50% of the Tested Population
mm- millimeter
MMAD - Mass Median Aerodynamic Diameter
NMD - Number Median Diameter
SD - standard deviation
[im - micron
-------
Table 4. Available Dose-Response Data for Multiple Dose Exposures of Guinea Pigs, Rabbits, Nonhuman Primates, and Humans
Author and
Year
U.S.
Environmental
Protection
Agency 2012
Albrinkand
Goodlow 1959
Strain and
Particle Size
(Receptor)
Ames, MMAD
(GSD) for Each
Dose Group
0.79 |am (1.52),
0.82 |am (1.53),
0.86 |am (1.49),
Respectively;
New Zealand
White Rabbit
Vollum rB,
Particle Size
NMD of 1.4
|am,
Chimpanzee
Doses Tested [for animal
receptor] or Doses Observed
[human receptor] (Units) and
Number of Exposures
2.91 x 102 CPU with 15
Exposures
1.22 x 103 CPU with 15
Exposures
1.17 x 104 CPU with 15
Exposures
Dose 1: 32,800 Viable Spores
Dose 2: 90,300 Viable Spores
Dose 1: 34,350 Viable Spores
Dose 2: 112,000 Viable Spores
Number per
Dose Group
7
1
1
LD50 Reported for
Study Data
Accumulated LD50of
8.1 x 103 CPU (95%
Fieller's Confidence
Interval, 2.3 x
103 CPU to 3.6 x
107 CPU),
Average Daily Dose
BMDL50of2.60xl03
CPU, Accumulated
Dose BMDL50 of 4.40
x 104 CPU
Not Reported
Highest Dose or
Highest Dose
Group Without
Reported Death
2.91 x 102 CPU
Dose Group, 1.12
x 103 CPU Highest
Individual Daily
Mean Dose Not
Associated with
Death
Dose 1: 32,800
Viable Spores
Dose 2: 90,300
Viable Spores
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Inhaled Dose
Inhaled Dose
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
High: All data
usability elements
present
Low: Total number
of animals tested
less than 12, Lack
of real-time
methods to derive
inhalation rates
-------
Author and
Year
Brachman et al.
1966
Brachman et al.
1966
Strain and
Particle Size
(Receptor)
Strain Not
Reported,
Particle Size
Reported to be
< 5 |am,
Cynomolgus
Monkey
Strain Not
Reported,
Particle Size
Reported to be
< 5 |am, Guinea
Pig
Doses Tested [for animal
receptor] or Doses Observed
[human receptor] (Units) and
Number of Exposures
Daily Doses Not Reported, 3
Exposure Runs of Various
Lengths < 47 Days, Differing
Exposure Sources and
Concentrations
First Run: 16,962 Total B.
anthracis Particles over 47
Days
Second Run: 4,959 Total B.
anthracis Particles over 41
Days
Third Run: 947 Totals.
anthracis Particles over 55
Hours + 1,347 Totals.
anthracis Particles over 31
Hours
947 Total 6. anthracis Particles
over 55 hours + 1,347 Total B.
anthracis Particles over 31
hours (Dose Reported as
Inhaled Dose of Monkey)
2 Multiple Day Exposures
Number per
Dose Group
st r-
1 Exposure
Run: 32
Monkeys
-.nd r-
2 Exposure
Run:
31 Monkeys
.
3 Exposure
Run: 28
Monkeys with
Sacrifice of 6
Monkeys During
Exposure Period
47
LD50 Reported for
Study Data
Not Reported
Not Calculable
Highest Dose or
Highest Dose
Group Without
Reported Death
Not Reported
All Survivors
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
1
Inhaled Dose
Inhaled Dose
Low: Dose-
response raw data
not reported,
Particle size not
reported based on
measurement Lack
of real-time
methods to derive
inhalation rates
Low: Dose-
response raw data
not reported,
Particle size not
reported based on
measurement Lack
of real-time
methods to derive
inhalation rates
-------
Author and
Year
Dahlgren et al.
1960
Strain and
Particle Size
(Receptor)
Strain Not
Reported,
Environmental
Concentration
Reported for
All Particles
and Particles <
5 [im, Human
Doses Tested [for animal
receptor] or Doses Observed
[human receptor] (Units) and
Number of Exposures
Inhaled Dose
Day 1: Pennsylvania
1,300 Viable Particles in 8
Hours with 510 Viable Particles
< 5 [im in Size
Day 2: Pennsylvania
620 Viable Particles in 8 Hours
with 410 Viable Particles <5
[im in Size
2-Day Exposure
Inhaled Dose
Day 1: New Hampshire
620 Viable Particles in 8 Hours
with 140 Viable Particles < 5
[im in Size
Day 2: New Hampshire
2,200 Viable Particles in 8
Hours with 690 Viable Particles
< 5 [im in Size
2-Day Exposure
Number per
Dose Group
Not Reported
Not Reported
LD50 Reported for
Study Data
Not Reported
Not Reported
Highest Dose or
Highest Dose
Group Without
Reported Death
Asserted that
1,300 Inhaled
Spores for All
Particle Size
Measurement or
510 Inhaled
Spores for
Particles < 5 [im
or Less for an 8-
hour Exposure
Was Not
Associated with
Human Inhalation
Anthrax
Reported as
Environmental
Concentration or
Inhaled Dose
(Comment)
Data Usability for
Modeling Low
Dose Exposures
(Red, Yellow, or
Green and
Reason(s) for
Rating)
Inhaled Dose
Low: Lack of real-
time methods to
derive inhalation
rates, Total
number of
individuals tested
less than 12
Human data collected in epidemiological, observational studies in an occupational setting.
BMDL50 - lower limit of a one-sided 95% confidence interval on the benchmark dose at a benchmark response level of 50%
CPU - colony forming unit
GSD - Geometric Standard Deviation
LD50- Lethal dose for 50% of the tested Population
MMAD - Mass Median Aerodynamic Diameter
NMD - Number Mean Diameter
[im- micron
-------
Featured EPA Publications and products
> U.S. Environmental Protection Agency (EPA). (2012). Multiple daily low dose Bacillus
anthracis inhalation exposures in the rabbit. Washington, DC: U.S. Environmental
Protection Agency. EPA/600/R-11/145
> Taft SC and Mines SA. (2012). Benchmark dose analysis for Bacillus anthracis inhalation
exposures in the nonhuman primate. Accepted in Risk Analysis. Published online at
doi: 10.1111/j. 1539-6924.2012.01808.x
> U.S. Environmental Protection Agency (EPA). (2011). Acute low dose Bacillus anthracis
inhalation exposures in the rabbit. Washington, DC: U.S. Environmental Protection
Agency. EPA/600/R-11/075
> U.S. Environmental Protection Agency(EPA) and U.S. Army Public Health Command
(Provisional). (2010). Pathogen information catalogue (PI CAT) tool. Washington, DC:
U.S. Environmental Protection Agency. EPA/600/C-10/008
> U.S. Environmental Protection Agency (EPA). 2010. Benchmark dose analysis for
Bacillus anthracis inhalation exposures in the nonhuman primate and application to risk-
based decision making. Washington, DC: U.S. Environmental Protection Agency.
EPA/600/R-10/138
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