Decontamination Strategies, Methods, and Related Technical Challenges for Remediation Following a Wide-Area Bacillus anthracis Spore Contamination Incident


Decontamination Strategies, Methods, and Related Technical
Challenges for Remediation Following a Wide-Area Bacillus anthracis

Spore Contamination Incident

Purpose

This technical brief provides decision makers with a practical summary of recent US EPA
scientific information and data related to remediation strategies and methods following a wide-
area Bacillus anthracis spore contamination incident.

Summary

This technical brief is a summary of US EPA research publications providing input to solving the
technical challenges involved with remediating a large urban area following a contamination
incident involving spores of B. anthracis, the causative biological agent for anthrax disease. The
research topics included in this summary are as follows:

•	Attenuation and transport of B, anthracis spores in an outdoor environment, with
implications for remediation

•	Decontamination studies evaluating the following aspects:

O spore inactivation efficacy
O spore removal efficiency

O field demonstrations for remediation of specific infrastructure
O decontamination issues specific to outdoor materials and conditions
O increasing decontamination capacity for wide-area events

•	Large-scale spray application of decontaminants

•	Modelling tools for wide-area decontamination decision making, prioritization, and
planning

D

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Introduction

The US EPA's Homeland Security Research Program helps to develop remediation capabilities to
recover from wide-area contamination originating from natural disasters, intentional releases,
or accidents involving oil or hazardous substances. These hazardous substances can include
chemical, radiological, nuclear, and biological materials (such as B. anthracis spores). The
homeland security research program develops remediation tools with consideration for
efficacy, safety, resource demand, logistics, training, and availability of the technology (US EPA,
2020).

Following a large, outdoor release of B. anthracis spores, assessments will be needed to
determine the extent of the contamination and the expected efficacy of various
decontamination techniques. If remediation is not 100% effective, i.e., if low levels of spores
are still present in certain locations, multiple lines of evidence may be used to determine if
additional decontamination is needed (US EPA, 2021; EPA/600/R-21/124).

After the initial wide-area release and deposition of spores onto surfaces, B. anthracis spores
may continue to spread through the air due to reaerosolization (US EPA, 2014; EPA/600/R-
14/259). Spore transport may also occur over the surface and through the subsurface
environment due to precipitation events. Without any remediation, over time the area
contamination may enlarge while the quantity of the spores per unit area may diminish.
Decisions will need to be made whether decontamination is even necessary for some areas,
based on several criteria, such as risk, cost, decontamination efficacy, and sampling/detection
limits. Risk may be low if exposure is inconsequential, and/or if medical countermeasures are in
place, e.g., the use of vaccines or antibiotics.

In general, remediation measures for a wide-area B. anthracis contamination incident may
consist of applying chemicals to inactivate the spores; physical removal of the spores or
materials containing the spores for off-site treatment and/or disposal; allowing attenuation of
the spores from exposure to sunlight and other natural phenomena; and any combination of
the above. All these approaches are discussed below.

Persistence and natural attenuation of B. anthracis spores and vegetative cells

In a wide-area release of 6. anthracis spores, natural attenuation or inactivation of the spores
may occur if the spores are directly exposed to sunlight. Although B. anthracis spores are
known to persist in soil for decades, they may become inactivated upon exposure to solar
radiation (National Response Team, 2022). In laboratory tests using simulated sunlight, B.
anthracis spores on glass were inactivated to nearly a 4 logio reduction (LR) in just a few days,
while there was minimal inactivation of spores in soil after 2 months (Wood et al., 2015).

Certain chemical or environmental conditions found naturally in soils (US EPA, 2014; 600/R-
14/216), or chemicals (referred to as germinants) added intentionally to soils or other matrices,
can initiate conversion of B. anthracis spores to vegetative cells. Vegetative cells are less
resistant to chemical or environmental inactivation than bacterial spores, and so the vegetative

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
cells could then be inactivated more easily via natural attenuation processes. In a study
examining this phenomenon, vegetative B. anthracis cells persisted less than 12 hours on wood,
concrete, and glass, and no more than 5 days in soil, without any exposure to sunlight (US EPA,
2014; R-14/150).

In a study to assess the recovery of B. anthracis surrogate spores over time in the outdoor
environment as a function of sampling method and material, several orders of magnitude loss
in recovery of spores occurred after 210 days (Mikelonis et al., 2020). The study authors
suggested diminished recovery of spores at the same location over time was due to
transport/removal of spores from the area of interest and/or inactivation by ultraviolet light
from the sun.

Movement of spores through the air

In general, air dispersion models predict that an aerosol release of a particulate contaminant
(such as B. anthracis spores) would result in higher surface deposition in the immediate area of
the release to progressively lower levels as the distance from the release increases (US EPA,
2020; R-20/338).

Once spores have settled on surfaces after the initial release, they can be reaerosolized and
spread further, depending on several factors and phenomena (US EPA, 2014; EPA/600/R-
14/259). Vehicles, human movement, and other fomites are significant drivers of
reaerosolization (US EPA, 2016; R-16/129). Temperature, relative humidity, air movement, and
physical disruption also affect the amount of reaerosolization and tracking of spores from
contaminated to uncontaminated areas (US EPA, 2012; R-12/064). Thus, in planning
remediation approaches following a wide-area release, decontamination procedures should
consider the possibility that spores can be reaerosolized from contaminated areas to areas that
were previously uncontaminated or previously decontaminated.

Correspondingly, spores have been demonstrated to migrate from the outdoor environment to
contaminate the interior of buildings. One study conducted to assess aerosol infiltration into
buildings found that Indoor/outdoor particle count ratios ranged from 0.3-0.6 (Rodes et al.,
2009). Spores may also migrate in the opposite direction, i.e., they may exfiltrate from the
interior of a contaminated building to the outdoor environment during decontamination
(Silvestri et al., 2015).

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Figure 1. Small wind tunnel used to assess reaerosolization of bacterial spores off materials

Movement of spores via surface water runoff

EPA research has shown that bacterial spores can be further distributed over the outdoor
surface environment due to precipitation events (Mikelonis et al,, 2020; spore surface
interactions). Laboratory tests showed that up to 15% removal of spores from asphalt and
concrete materials occurred after an hour of simulated rainfall (Mikelonis et al., 2021; rainfall
wash-off).

The modeling of B. anthracis spore wash-off and transport processes can help to determine
areas where contamination is likely to persist over time or where spores may accumulate in
overland flow following a wide-area contamination incident. This may inform decisions about
remediation and sampling activities. Surface flow will eventually enter stormwater
infrastructure, with spores moving in unanticipated ways due to flow control structures, routing
systems, and redirection to storages (Shireman et al., 2021). Measures for containment of
stormwater runoff to prevent spore migration to allow for further eventual treatment are being
developed (Mikelonis et al., 2021; stormwater containment).

Techniques to Remove Spores from Outdoor Surfaces

Following a wide-area incident, spores can be physically removed from roadways and other
outdoor surfaces via water spraying techniques. Such techniques could include the collection of
spores using street sweeping/washing equipment. In a pilot-scale study using a walk behind
floor scrubber to represent a street sweeper, surrogate B. atrophaeus spores were removed
from surfaces with an efficiency of 74-99% when dispensing water, depending on the surface

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
material (asphalt or concrete). When the model street sweeper dispensed decontaminants such
as dichlor or pH-amended bleach (PAB), over 7 LR was achieved on the surfaces. However, it
should be noted that in nearly all the tests, spores were reaerosolized (US EPA, 2018;
EPA/600/R-18/271 2018).

In another study using a parking lot as the test surface, it was shown that a pressure washer
could remove an average of 12.5% of spores from the surface, compared to approximately only
1.3% with just the use of a garden hose. It was also found that certain wash aids improved the
removal efficiency, but only by 1-2% compared to tap water alone (Mikelonis et al., 2021;
influence of wash aids).

In tests using a garden hose equipped with a brass nozzle (~ 4 liters per minute at 1 foot
distance), and spraying either tap water, surrogate brackish water, or surrogate seawater (no
detergent), removal efficiency of B. atrophaeus spores from marine grade aluminum was about
90%, with the type of water having no effect. When spores were inoculated onto a rubber
material, removal efficiency ranged from around 2-3 LR, depending on the type of water
sprayed (US EPA, 2022A).

Wash water may be generated during site remediation activities, such as for spore removal
purposes as discussed above, and for equipment or PPE decontamination (US EPA, 2019; Tech
Brief S-19/067). This wash water may be collected using procedures similar to stormwater
collection, and then subject to treatment. The EPA has developed several treatment methods
designed to overcome operational challenges associated with bio-contaminated wash water
(US EPA, 2019; Tech Brief S-19/067). Wash water that is not collected would aid in the transport
of spores through the environment, similar to spores on exterior surfaces entrained in
stormwater during precipitation events.

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Figure 2. Rainfall simulator test apparatus to assess wash-off of spores from outdoor materials

Decontamination Efficacy Using Chemical-Based Decontaminants

Although the efficacy of a decontaminant is critical in its selection, there are other criteria for
selecting a decontamination method. These may include whether the technology has been
demonstrated at full-scale, its cost, its availability (technology, chemicals, expertise, personnel),
material compatibility, health and safety issues (most decontamination chemicals are
hazardous), and environmental impacts. The EPA has extensively evaluated the efficacy of
decontamination technologies (mostly chemical based) for B. anthracis spore inactivation and
in 2019, published a review of their and others' research in this area (Wood and Adrion, 2019).
That review provided a synthesis of liquid and gaseous-based chemical decontaminants, as well
as a few physical-based techniques, that are commercially available and could be used at a
relatively large scale (e.g., following a wide-area event), in that review, decontamination
efficacy data were discussed and presented as a function of material, environmental conditions,
and decontaminant application conditions such as chemical concentration and contact time.

6

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
The most likely and effective decontaminant gases or fumigants that would be employed in a
wide-area event would include chemistries such as chlorine dioxide (CIO2, methyl bromide
(MeBr), hydrogen peroxide vapor (HPV), and formaldehyde. The more common and effective
liquid-based decontaminants that would likely be used include those utilizing hypochlorous-acid
chemistry (diluted bleach, PAB, dichlor, and calcium hypochlorite) or peroxides (e.g.,
concentrated hydrogen peroxide (> 35%), peracetic acid (PAA), and activated sodium
persulfate). Liquid decontaminants can be applied via numerous techniques, e.g., as a spray,
immersion, gel, foam, fog, or wipe. Lesser-used but effective sterilant techniques that may have
niche uses following a wide-area event include ultraviolet light (in the C range, e.g., produced
from mercury lamps), ozone gas, ethylene oxide, and ionizing radiation.

Field Studies Conducted for Decontamination of Specific Infrastructure

Small Building Interiors

As mentioned above, in a wide-area release of B. anthracis spores, the interior of houses and
buildings may become contaminated through various means of infiltration. Several field studies
have been completed to demonstrate the decontamination of small structure interiors. In the
large multiagency Bio-response Operational Testing and Evaluation (BOTE) study, the
decontamination of a 2-story office building was demonstrated using three different
decontamination techniques, which included CIO2 gas, HPV, and the powered-spraying of PAB
(US EPA, 2013; 600/R-13/168). The building was tented to minimize the loss of decontaminant
chemicals to the exterior.

MeBr gas was effective in the field scale demonstration for the decontamination of a 1,444 m3
building. In that demonstration, no damage to the building or its contents was observed (Serre
et al., 2016). Following fumigation, the MeBr was collected with activated carbon (Wood et al.,
2016) to minimize its release to the atmosphere.

The simple-to-use decontamination technology referred to as low concentration hydrogen
peroxide vapor (LCHPV) was demonstrated in a full-scale test house (Mickelson et al., 2019).
This technique is inexpensive and developed from commercial, off the shelf (COTS) equipment
and chemicals, and if implemented by lay personnel (home or business owners), would greatly
increase decontamination capacity following a wide-area release of B. anthracis spores.

Subway infrastructure

The decontamination of a mock subway tunnel and station was successfully demonstrated
using two different decontamination techniques (fogging of diluted bleach and powered-
spraying of PAB) as part of the large multiagency Underground Transport Restoration
Operational Technology Demonstration (UTR-OTD) study (US EPA, 2017; EPA/600/R-17/272).
Also, as part of the UTR project, the use of MeBr to decontaminate an out of service subway
railcar was successfully demonstrated (US EPA, 2017; EPA OEM report March 15, 2017).

Several other decontamination studies conducted under the UTR program for subway materials
and systems etc., are summarized in a previous Tech Brief (US EPA, 2018; EPA/600/S-18/286).
One laboratory study showed that PAB and diluted bleach could be used to successfully

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
decontaminate concrete, ceramic tiles, painted steel surfaces, and ballast materials taken from
a subway system. The study showed that efficacy depended on the free available chlorine (FAC)
concentration, presence of grime, and other parameters (US EPA, 2018; EPA/600/R-18/251). In
another study (US EPA, 2014; EPA/600/R-14/226), fumigating with either CIO2 gas or HPV was
successful in decontaminating subway concrete, with the presence of grime not impacting
efficacy.

Maritime infrastructure

Under the Analysis for Coastal Operational Resiliency (AnCOR) program funded by the
Department of Homeland Security, Science and Technology Directorate, the EPA conducted lab-
, pilot- and field scale testing of decontamination options for the US Coast Guard (USCG) and
maritime-related assets. In case of a wide-area release of B. anthracis at a port city, the US Coast
Guard would likely be the lead federal agency for response activities within the coastal zone. The
overall purpose of this multi-agency program was to develop and demonstrate capabilities and
strategic guidelines to prepare the U.S. for a wide-area release of a biological agent, including
mitigating effects on USCG facilities and assets.

Following an anthrax release impacting a USCG base or station, it would be imperative for the
USCG to rapidly return to service their marine assets such as patrol boats and cutters. As part of
the AnCOR program, the EPA conducted a field-level demonstration of three methods that
could be used to decontaminate a USCG vessel contaminated with B. anthracis. Prior to the
application of each decontamination procedure, PAB was applied to the exterior surfaces of the
boat down to the water line. After spraying the PAB, the USCG boat was further
decontaminated with either MB fumigation, PAA fog, or LCHPV. The MB and PAA fog
decontamination rounds resulted in no positive samples for the B. anthracis surrogate being
used, and with LCHPV, only a few samples were positive. In all three test rounds, none of the
test electronics were impacted by the decontaminants (US EPA, 2021).

One of the lab studies conducted under the AnCOR program evaluated the efficacy of the Navy
ship-based decontaminant calcium hypochlorite, aka high-test hypochlorite (HTH), on outdoor
materials (asphalt and concrete) and USCG boat-related materials, using B. atrophaeus as a
surrogate for B. anthracis. In 90% of the tests, the HTH solution (~ 24,000 parts per million FAC)
decontaminated the material such that no spores were detected. This contrasts with PAB, in
which only about 40% of the test results achieved no spores detected (US EPA, 2022A).

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Figure 3. Field test demonstration of Coast Guard patrol boat decontamination

Difficult-to-Decontaminate Outdoor Materials and Conditions of Concern

Soil

The efficacy of a decontaminant in inactivating B. anthracis spores is highly dependent on the
material with which the spores are associated, and soil remains one of the most difficult
materials to decontaminate. This is due to its relatively high organic content, other variable
chemical constituents and physical properties such as density, particle sizes, and porosity
(Wood and Adrion, 2019). The EPA has been evaluating soil decontamination methods for over
10 years. Some oxidant-based decontaminants such as hypochlorous acid/hypochlorite and
PAA (US EPA, 2014; EPA/600/R-14/189) performed poorly in decontaminating soil, while other
oxidants such as CIO2 gas and activated sodium persulfate (US EPA, 2017; R-17/343) were found
to be relatively effective. Several alkylating decontaminants have been demonstrated to be
effective in decontaminating soil, including MeBr (US EPA, 2017; R-17/343), metam sodium (US
EPA, 2013), and formaldehyde (Richter et al., 2022). In general, decontamination efficacy has
been shown to diminish with soil depth.

Ex-situ treatment of B. anf/7rac/s-contaminated soil (e.g., excavation/removal of soil followed by
off-site treatment such as incineration) is another remediation option, although this approach
may aerosolize and disperse the B. anthracis spores during the excavation and transport

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
processes and cause further cross contamination. Thus, in-situ treatment of soil contaminated
with B. anthracis spores, such as with the chemical decontaminants discussed above, or with
the use of thermal techniques, are remediation options that would potentially avoid the
aerosolization of spores. Wood et al. (2020) demonstrated the feasibility of using dry heat to
decontaminate soils contaminated at the surface with B. anthracis. Lastly, the addition of
chemicals to induce germination of B. anthracis spores to the vegetative cell form, which is
known to be less resistant than spores to environmental stressors and chemical inactivation,
has been investigated as a soil decontamination option as well.

Dirt/grime on materials

Like soil, the presence of organic material in the form of dirt/grime on the surface of other
materials may diminish a decontaminant's efficacy, especially if the decontaminant is an
oxidant-based liquid. However, lab-scale studies have shown mixed results from the impact of
grime, possibly due to variations in the grime recipe used, materials, and the decontaminants
evaluated. For example, three studies (EPA/600/R-12/591; US EPA, 2014; EPA/600/R-14/226;
EPA/600/R-16/038) using either PAB, HPV, or CIO2 gas demonstrated little to no impact of
grime on decontamination efficacy, while a study investigating MeBr (EPA/600/R-17/187)
showed that higher concentrations and/or longer contact times were required to achieve 6 LR
on grimed materials. In a study investigating the use of bleach-based decontaminants for
subway materials, the presence of grime diminished efficacy by 1-3 orders of magnitude.

Vegetation

A study was conducted to assess decontamination options for vegetative materials, and found
that under some conditions, both dichlor- and PAA-based spray decontaminants were effective
(no samples were positive for bacterial spores) for small plants (US EPA, 2022B). Pine bark and
sod/grass were more difficult to decontaminate than the plants, although PAA was generally
more effective than dichlor. Tests were also conducted to assess any detrimental impacts that
the decontaminants (PAA and dichlor) may have on the plants (phytotoxicity). While none of
the small plants died during the month-long observations following exposure to the
decontaminant, there were some mixed results with respect to other phytotoxic effects that
varied by plant type, decontaminant, and the type of phytotoxic effect. No obvious trends in
effects were noted.

Tests conducted specifically for outdoor materials (asphalt, concrete, brick, wood)

Materials used in outdoor infrastructure are typically porous and may be comprised of organic
matter, making their decontamination difficult. Two separate studies were conducted to
evaluate decontamination efficacy for such materials, including asphalt, concrete, brick, and
wood. In one study (US EPA, 2015; EPA 600/R-15/101), several conditions were found in which
activated sodium persulfate was an effective decontaminant for the four materials, with
concrete being the most difficult.

Concrete was also found to be the more difficult material to effectively decontaminate in
another study to evaluate the efficacy of dichlor, PAB, and diluted bleach for the same four
materials (US EPA, 2021; EPA 600 R-21/004). In that study, diluted bleach and dichlor produced

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
similar efficacy results, while the PAB was generally iess effective. Decontamination was most
successful on the brick material

Vehicles

Following a wide-area B, anthracis incident, many vehicles may become contaminated and left
unattended in the impacted area. Vehicles contain a broad array of materials and components
that may need to be decontaminated (EPA/600/R-19/068). in addition, many vehicle parts are
electrical or mechanical, and contain sensitive materials, making decontamination even more
difficult due to material compatibility issues.

Cold temperatures

Following a wide-area release of B. anthracis spores, decontamination may need to be
undertaken at relatively colder temperatures. Several decontamination studies have confirmed
that in most cases (not all), achieving sufficient efficacy at 10 °C or below typically requires
longer contact times and/or higher concentrations of the decontaminant active ingredient than
what would be required if the decontamination testing occurred at the more typical lab
ambient test temperatures of 20-25 °C. This was found to be the case when fumigating with
CI02 (US EPA, 2016; 600/R-16/038) and MeBr (US EPA, 2016; EPA/600/R-17/187). The efficacy
of PAA fog diminished with lowering temperature as well (Richter et a!., 2018). Tests with
formaldehyde vapor showed that at 10 °C, lower concentrations were achieved, resulting in
reduced efficacy (Choi et a I., 2020). However, there were a few studies that showed minimal
impact in reducing temperature. In one study evaluating PAB (using various formulations to
lower the freezing point) at cold temperatures, it found minimal difference in efficacy for tests
conducted at 0°, 10 °, and 25 °C (U.S. EPA, 2017; EPA/R-17/211). In a study evaluating
formaldehyde solution to decontaminate soil, lowering the temperature from 24 to 10 °C did
not affect efficacy in one set of conditions evaluated (Richter et al., 2022).

Figure 4. Laboratory tests to evaluate decontamination of vegetation

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Expanding decontamination capacity with easy to use, readily available
equipment and chemicals

Following a wide-area release of B. anthracis spores, the time required to recover from the
incident will be limited by many factors, including the availability of decontamination resources
(equipment, chemicals, expertise, personnel). One way to increase decontamination capacity is
to develop techniques that can be implemented using readily available, COTS equipment and
chemicals, and that don't require extensive expertise or training in their use. These techniques
are sometimes referred to as "self-help" or "low-tech" approaches and may only require a trip
to the local hardware store. These approaches could potentially be implemented by
homeowners, small business owners, and/or their remediation contractors. Several examples
of these techniques are summarized below.

Low concentration hydrogen peroxide vapor

The LCHPV approach (Wood et al., 2016) uses COTS aqueous solutions of hydrogen peroxide
disseminated with COTS equipment such as humidifiers or foggers. In lieu of relatively high
concentrations with short contact times, concentrations of 25-50 parts per million HPV coupled
with contact times of several days have been shown to be effective in inactivating B. anthracis
spores. As discussed above, this technique has been successfully demonstrated at full-scale for
decontaminating a house, a Coast Guard boat, and a vehicle.

Off the shelf cleaning products

Several ready to use cleaning solutions comprised of at least 2% sodium hypochlorite were all
effective against a B. anthracis surrogate on several types of materials (US EPA, 2015;
EPA/600/R-15/228). In this same study, germicidal bleach with a dilution of 1:5 provided
satisfactory sporicidal activity. Based on this research, subsequent decontamination studies
involving diluted bleach typically utilize it with an FAC level of around 20,000 parts per million.

Clothes washing and drying

After a wide-area release, personal clothing may become contaminated with the biological
agent. Clothes washers and dryers with a suitable decontamination solution are a potential self-
help practice to reduce and/or inactivate biological spores from common clothing material. In a
study to evaluate this, it found that a 1% chlorine bleach solution coupled with a laundry
detergent was indeed effective in inactivating spore contamination from fabric materials when
using an 18-minute wash cycle. The study also found that using a clothes dryer was not advised
since it provided no additional spore reductions beyond using a washer and resulted in the
reaerosolization of spores (US EPA, 2020; EPA/600/R-20/217).

Pool and spa chemicals

Sodium dichloro-s-triazinetrione, also known as dichlor, is a widely available granular pool
disinfection chemical that can be prepared as a sporicide by simply mixing with water. When
prepared at a concentration of 2% FAC, it was evaluated for decontamination efficacy for
outdoor materials and compared to the more well-known decontaminants PAB and diluted
bleach (US EPA, 2021; EPA/600/R-21/004). It was found in that study that dichlor and diluted

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
bleach achieved similar levels of decontamination efficacy for the materials tested and were
more effective than PAB.

Cleaning methods to remove spores

Although cleaning approaches are primarily meant to remove or trap bacterial spores and not
necessarily inactivate them, lab tests have shown that floor cleaning cloths can remove up to
99.9% of bacterial spores from surfaces (US EPA, 2017; EPA/R17/126), and that wet-vacuum
carpet cleaners removed up to 99.99% of spores from carpet (US EPA, 2013; EPA/600/R-
13/217).

Use of solid-based decontaminants

The ability to timely remediate wide-area B. anthracis contamination will be limited by several
factors, including a sufficient supply of decontaminant chemicals. The quantity of
decontaminant chemicals available can be broadened by including the use of solid-phase bulk
chemicals, in which water is added at the point where decontamination will take place. The use
of dry chemical precursors will have the added benefit of reducing transportation costs and
hazards. Several dry powder decontaminant chemicals (some are discussed above) include
dichlor (US EPA, 2021; EPA 600 R-21/004), calcium hypochlorite (US EPA, 2022A), and sodium
persulfate (US EPA, 2015; EPA/600/R-15/101). Sodium chloride (table salt) added to water can
be used to generate a hypochlorous-acid based decontaminant by passing an electrical current
through an electrochemical cell containing the brine solution (US EPA, 2011; EPA/600/R-
11/124). This technology was found to be effective against B. anthracis spores on hard, non-
porous inorganic materials. Other dry chemical decontaminant options include PAA precursor
chemicals such as peracetyl borate and diperadipic acid (US EPA, 2018; EPA/600/R-18/157).

Spray Application of Liquid Decontaminants at Large Scale

Following a wide-area release of B. anthracis spores, large-scale commercial, agricultural, and
industrial types of spray equipment would likely be used to apply liquid decontaminants to
roadways, building exteriors, and the surfaces of other infrastructure. Such sprayers were
evaluated for their potential use to apply decontaminants in a subway system (US EPA, 2017;
EPA/600/R-17/156). Large radial fan type sprayers and a dust suppression spray cannon were
down selected for further evaluation. While the equipment was found to adequately spray
surfaces to obtain sufficient decontamination efficacy, the issue of material compatibility of
sprayer components (e.g., pump diaphragm) with the corrosive decontaminants was another
finding of the project.

A database of commercial equipment that could potentially be used in response to a wide-area
B. anthracis contamination incident has been developed. (US EPA 2022C;
https://radar.epa.gov/widget/11796291-7778-43ff-84d9-190ecc2db583). The equipment inventory
includes that which could be used for sampling and decontamination (among other response
categories), such as the use of large commercial sprayers. The intent was to pre-collect and

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
rank equipment that could be used in the event of such an incident by already conducting
market surveys and assessments. After an incident, responders can query the tool to identify
equipment options.

Figure 5. Test demonstration of large radial fan sprayer

Wide-area decontamination related planning tools and models

Recovering from a wide-area release of B. anthracis spores becomes a large problem of
resource allocation, optimization, and prioritization. Several tools and models have been
developed to address these issues and are briefly summarized below.

The Prioritization Analysis Tool for All-Hazards and the Analyzer for Wide-area Effectiveness
(PATH/AWARE) was developed under the Department of Homeland Security's Integrated
Biological Restoration Demonstration program and was further demonstrated for the Wide-
area Recovery and Resiliency Program (US EPA, 2021; EPA/600/R-21/096).

The Stochastic Infrastructure Remediation Mode! was developed to dynamically model the
interdependencies of critical infrastructure sectors and allows the user to draw statistical
conclusions specific to an incident. This model allows for all infrastructure sectors to be
modeled, considers the realistic variability of the impact of an incident, and predicts the time
required to restore each sector to its original operating efficiency (US EPA, 2021; EPA/600/R-
21/096).

The Wide-Area Decontamination Tool (WADT) calculates cost, time, and other resource
demands associated with the remediation (sampling, decontamination, waste disposal, etc.) of
a wide-area biological incident (US EPA, 2022D). The model utilizes EPA's bio-decontamination
compendium to provide estimates of decontamination efficacy for various decontaminants
applied to different materials, to determine if multiple treatments are needed. The predicted
costs and time requirements are based on actual costs and time requirements determined from
previous field studies.

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
The Remediation Data Repository (RADAR) tool (US EPA, 2019; EPA/600/C-19/114, July 2019)
provides a simple, online interface to search EPA's Homeland Security Research Program data.
The purpose of RADAR is threefold: 1) to provide support to cleanup and recovery operations,
2) to inform research and facilitate use of results, and 3) to provide models and software tools
with the most up-to-date research.

The Decon Strategy and Technology Selection Tool (US EPA, 2014) is used to support making
recommendations on how to decontaminate buildings contaminated with chemical or
biological agents. This tool is available upon request. Other response support tools, such as
those for sampling and waste management, can be found at https://www.epa.gov/emergency-
response-research.

Conclusions

In the event of a large outdoor release of B. anthracis spores, there are several tools and
strategies that could be implemented in the lengthy and costly remediation process that would
follow. Modeling and planning software has been developed by EPA and others to assist with
prioritization and optimization of resources and the selection of decontamination approaches
that would be needed for such an unprecedented event. These decontamination strategies and
techniques could include natural attenuation of the spores, physical removal, and/or
inactivation of the spores via chemical and physical based technologies. The EPA has conducted
extensive bench-, pilot-, and field-scale testing of all these approaches. Studies have been
conducted and technologies demonstrated for the decontamination of building interiors and
other infrastructure, as well as for the decontamination of outdoor areas and materials. Many
factors affect how efficacious a decontaminant is in inactivating or removing B. anthracis
spores, with the material the spores are contaminating a primary consideration. Outdoor
materials (e.g., soil, vegetation, concrete) and vehicles, as well as the outdoor environment
itself (with issues like cold temperatures), present daunting challenges for remediation. Spores
will move through the air and surface environments over time and may contaminate previously
uncontaminated or decontaminated areas. Current research efforts include analyzing the
availability and feasibility of using existing, commercially available, large-scale spray equipment
that could be used to apply liquid decontaminants over large outdoor areas and infrastructure.
The EPA has also taken the approach of trying to build decontamination capacity for such an
event by emphasizing and evaluating the use of low-tech, low cost, readily available
decontamination techniques.

Disclaimer

The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development, produced this document. This document underwent review prior to approval for
publication. Note that approval does not necessarily signify that the contents reflect the views

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
of the Agency. Mention of trade names, products or services does not convey official EPA
approval, endorsement, or recommendation.

References

Choi YW, Sunderman MM, McCauley MW, Richter WR, Willenberg ZJ, Wood JP, Calfee MW.
2020. "Decontamination of Bacillus Spores with Formaldehyde Vapor Under Varied
Environmental Conditions". Appl Biosafety.
https://www.liebertpub.com/doi/10.1089/apb.21.926975

Mikelonis AM, Abdel-Hady A, Aslett D, Ratliff K, Touati A, Archer A, et al. 2020. "Comparison of
surface sampling methods for an extended duration outdoor biological contamination study".
Environ Monit Assess, 192: 455.

Mikelonis AM, Ratliff K, Youn S. 2020. "Laboratory results and mathematical modeling of spore
surface interactions in stormwater runoff". J Contam Hydro, 235.

Mikelonis AM, Calfee MW, Lee S, Touati A, Ratliff K. 2021. "Rainfall washoff of spores from
concrete and asphalt surfaces". Water Resources Research, 57, e2020WR028533.

Mikelonis AM, Fuller C, Ratliff K, Touati A, Calfee MW. 2021. "Influence of wash aids on Bacillus
removal from an asphalt parking lot using two spray-based washing methods". J Appl Microbiol,
00: 1-8. DOI: 10.1111/jam.15405.

Mikelonis AM, Hawley RJ, Goodrich JA. 2020. "Emergency response to stormwater
contamination: A framework for containment and treatment". J Environ Mgmt, 280.

Mickelsen RL, Wood JP, Calfee MW, Serre S, Ryan S, Touati A, Delafield FR, Aslett LD. 2019.
"Low-concentration hydrogen peroxide decontamination for Bacillus spore contamination in
buildings". Remediation, 30: 1.

National Response Team. Quick Reference Guide: Bacillus anthracis (Causes anthrax). February
2022. Available at:

https://www.nrt.Org/sites/2/files/NRT%20CBRN%20BIO%20UPDATE%20Anthrax%20QRG FINA
L%202022%2002%2016.pdf.

Richter WR, Wood JP, Wendling MQS, Rogers JV. 2018. "Inactivation of Bacillus anthracis
Spores to Decontaminate Subway Railcar and Related Materials Via the Fogging of Peracetic
Acid and Hydrogen Peroxide Sporicidal Liquids." J Environ Mgmt, 206: 800-806.
https://doi.Org/10.1016/i.ienvman.2017.ll.027.

Richter WR, Sunderman MM, Willenberg Z, Calfee MW, Serre S, Wood JP. 2022. "Effectiveness
of formaldehyde in various soil types as a wide-area decontamination approach for Bacillus

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
anthracis spores", https://doi.org/10.1371/iournal.pone.0277941

Rodes CE, VanOsdell DW, Portzer JW, Seagraves J, Hahn I, Henkle SW, Wiener RW. 2009.
"Building characterization and aerosol infiltration into a naturally ventilated three-story
apartment building". J Environ Monit, 11: 2180-2191.

Serre S, Mickelsen L, Calfee, MW, Wood, JP, Gray MS, Scheffrahn RH, Perez R, Kern WH Jr.,
Daniell N. 2016. "Whole-building decontamination of Bacillus anthracis Sterne spores
by methyl bromide fumigation". J Appl Microbiol, 12080.

Shireman J, Ratliff K, Mikelonis AM. 2021. "Modeling radionuclide transport in urban overland
flow: a case study". Urban Water Journal, DOI: 10.1080/1573062X.2021.1968007.

Silvestri EE, Perkins S, Lordo R, Kovacik W, Nichols T, Yoder Bowling C, Griffin D, Schaefer FW.
2015. "Observation of the Migration of Bacillus Spores Outside a Contaminated Facility During a
Decontamination Efficacy Study". J Bioterror Biodef, 6: 2.

U.S. Environmental Protection Agency. October 2011. "Evaluating a Decontamination
Technology Based on the Electrochemical Generation of Anolyte Solution against B. anthracis
Spores". EPA/600/R-11/124.

U.S. Environmental Protection Agency. December 2012. "Evaluation of Reaerosolization of
Bacillus Spores from a Sod Matrix". EPA/600/R-12/064.

U.S. Environmental Protection Agency. August 2012. "Assessment of Liquid and Physical
Decontamination Methods for Environmental Surfaces Contaminated with Bacterial Spores:
Evaluation of Spray Method Parameters and Impact of Surface Grime". EPA/600/R-12/591.

U.S. Environmental Protection Agency. December 2013. "Bio-Response Operational Testing and
Evaluation (BOTE) Project - Phase 1: Decontamination Assessment". EPA/600/R-13/168.

U.S. Environmental Protection Agency. August 2013. "Technology Evaluation Report
Decontamination of Soil Contaminated with Bacillus anthracis Spores". EPA/600/R-13/110.

U.S. Environmental Protection Agency. October 2013. "Determination of the Efficacy of Spore
Removal from Carpets using Commercially-Available Wet/Vacuum Carpet Cleaning Systems".
EPA/600/R-13/217.

U.S. Environmental Protection Agency. July 2014. "Environmental Persistence of Vegetative
Bacillus anthracis and Yersinia pestis". EPA/600/R-14/150.

U.S. Environmental Protection Agency. September 2014. "Literature Review on Mechanisms
that Affect Persistence of Bacillus anthracis in Soils". EPA/600/R-14/216.

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
U.S. Environmental Protection Agency. August 2014. "Interactions of CIO2 and H2O2 Fumigants
with Dirt and Grime on Subway Concrete". EPA/600/R-14/226.

U.S. Environmental Protection Agency. September 2014. "Determination of the Difference in
Reaerosolization of Spores off Outdoor Materials". EPA/600/R-14/259.

U.S. Environmental Protection Agency. August 2014. "Decontamination of Soil Contaminated
with Bacillus anthracis Spores". EPA/600/R-14/189.

U.S. Environmental Protection Agency. July 2014. "Decontamination Strategy and Technology
Selection Tool (Decon ST)", https://www.epa.gov/sites/default/files/2020-
03/documents/508deconst - decontamination decision support tool.pdf.

U.S. Environmental Protection Agency. July 2015. "Decontamination of Outdoor Materials
Contaminated with Anthrax Using Sodium Persulfate or Chloropicrin". EPA/600/R-15/101.

U.S. Environmental Protection Agency. September 2015. "Assessment of Bacillus spore
inactivation on indoor surfaces using commercially available cleaning products". EPA/600/R-
15/228.

U.S. Environmental Protection Agency. October 2016. "Developing a Table of Forces for Human
Activity as it Relates to Reaerosolization". EPA/600/R-16/129.

U.S. Environmental Protection Agency. June 2016. "Chlorine Dioxide Fumigation of Subway
Materials Contaminated with B. anthracis Surrogate Spores: Impact of Environmental
Conditions and Presence of Dirt and Grime on Decontamination Efficacy". EPA/600/R-16/038.

U.S. Environmental Protection Agency. September 2017. "Underground Transport Restoration
(UTR) Operational Technology Demonstration (OTD)". EPA/600/R-17/272.

U.S. Environmental Protection Agency. March 15, 2017. "Subway Railcar Decontamination with
Methyl Bromide".

U.S. Environmental Protection Agency. September 2017. "Assessment of the Decontamination
of Soil Contaminated with Bacillus anthracis Spores Using Chlorine Dioxide, Methyl Bromide, or
Activated Sodium Persulfate". EPA/600/R-17/343.

U.S. Environmental Protection Agency. May 2017. "Decontamination of Subway Infrastructure
Materials Contaminated with Biological Spores Using Methyl Bromide". EPA/600/R-17/187.

U.S. Environmental Protection Agency. August 2017. "Evaluation of Spray-Based, Low-Tech
Decontamination Methods under Operationally Challenging Environments: Cold
Temperatures". EPA/600/R-17/211.

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
U.S. Environmental Protection Agency. June 2017. "Operational Testing of Floor Cleaning Cloths
for Household Remediation Following a Large-Scale Biological Contamination Incident".
EPA/600/R-17/126.

U.S. Environmental Protection Agency. August 2017. "Evaluation of Commercially-Available
Equipment for the Decontamination of Bacillus Anthracis Spores in an Urban Subway System."
EPA/600/R-17/156.

U.S. Environmental Protection Agency. October 2018. "Decontamination Options for Restoring
Subway Systems following a Bacillus anthracis Contamination Incident". EPA/600/S-18/286.

U.S. Environmental Protection Agency. August 2018. "Evaluation of the Removal and
Inactivation of Bacterial Spores on Outdoor Surfaces Using a Small-Scale Street Sweeper".
EPA/600/R-18/271.

U.S. Environmental Protection Agency. August 2018. "Bleach-Based Biodecontamination of
Subway Materials". EPA/600/R-18/251.

U.S. Environmental Protection Agency. July 2018. "Evaluation of Diperadipic Acid as a Surface
Decontaminant for Spore-Forming Biological Agents" EPA/600/R-18/157.

U.S. Environmental Protection Agency. May 2019. "Research Results to Enhance Management
of Bacillus anthracis Contaminated Wash Water". EPA/600/S-19/067.

U.S. Environmental Protection Agency. January 2019. "Management and Disposal of Vehicles
Following a Wide-Area Incident: Literature Review and Stakeholder Workshop". EPA/600/R-
19/068.

U.S. Environmental Protection Agency. July 2019. "The Remediation Data Repository (RADAR)
Tool". EPA/600/C-19/114.

U.S. Environmental Protection Agency. October 2020. "Dispersion Modeling Systems Relevant
to Homeland Security Preparedness and Response". EPA/600/R-20/338.

U.S. Environmental Protection Agency. September 2020. "Washing/Drying of Clothing
Contaminated with a Biological Agent Such as Bacillus anthracis". EPA/600/R-20/217.

U.S. Environmental Protection Agency. May 2021. "Understanding Detection Limits Within the
Interim Clearance Goal for Bacillus anthracis Contamination". EPA/600/R-21/124.

U.S. Environmental Protection Agency. May 2021. "Inactivation of a Bacillus anthracis Spore
Surrogate on Outdoor Materials Via the Spray Application of Sodium Dichloro-s-triazinetrione
and Other Chlorine-Based Decontaminant Solutions". EPA/600/R-21/004.

U.S. Environmental Protection Agency. 2021. "U.S. Coast Guard Vessel Decontamination

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Demonstration". Washington, DC.

U.S. Environmental Protection Agency. September 2021. "Interconnected Infrastructure
Modeling Investigation". EPA/600/R-21/096.

U.S. Environmental Protection Agency. 2022A. "Evaluation of Decontaminants pH-Adjusted
Bleach and High-Test Hypochlorite for US Coast Guard Assets Following a Biological Agent
Release." EPA/600/R-22/027.

U.S. Environmental Protection Agency. 2022B. Spray Decontamination of Vegetation with
Sporicidal Liquids for the Inactivation of Bacillus anthracis Surrogate Spores and Phytotoxicity
Assessment. EPA/600/R-22/051.

U.S. Environmental Protection Agency. 2022C. "Commercial Equipment for Urban Biological
Decontamination". Available at: https://radar.epa.gov/widget/11796291-7778-43ff-84d9-
190ecc2db583

U.S. Environmental Protection Agency. 2022D. "Wide-area Decontamination Tool".
EPA/600/R-22/049.

Wood JP, Meyer KM, Kelly TJ, Choi YW, Rogers JV, Riggs KB, et al. 2015. "Environmental
Persistence of Bacillus anthracis and Bacillus subtilis Spores". PLoS ONE, 10(9): e0138083.
doi:10.1371/journal. pone.0138083.

Wood JP, Clayton MJ, McArthurT, Serre SD, Mickelsen L, Touati A. 2015. "Capture of methyl
bromide emissions with activated carbon following the fumigation of a small building
contaminated with a Bacillus anthracis spore simulant". J Air Waste Manage Assoc, 65(2):
145-153.

Wood JP, Calfee MW, Clayton M, Griffin-Gatchalian N, Touati A, Ryan SP. Mickelsen L, Smith L,
Rastogi V. 2016. "A simple decontamination approach using hydrogen peroxide vapour for
Bacillus anthracis spore inactivation". J Appl Microbiol. 121: 1603-1615.
doi:10.1111/jam.13284.

Wood JP, Adrion AC. 2019/Tteview of Decontamination Techniques for the Inactivation
of Bacillus anthracis and Other Spore-Forming Bacteria Associated with Building or Outdoor
Materials". Environ Sci Technol, 53(8): 4045-4062.

Wood JP, Touati A, Abdel-Hady A, Aslett D, Delafield F, Calfee MW, Silvestri E, Serre S,
Mickelsen L, Tomlinson C, Mikelonis A. 2020. "Decontamination of soil contaminated at the
surface with Bacillus anthracis spores using dry thermal treat". J Environ Mgmt.
https://doi.Org/10.1016/i.ienvman.2020.111684.

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------
Contact Information

For more information, visit the EPA website at https://www.epa.gov/emergency-response-
research/publications-homeland-security-research-topics.

Technical Contact: Joseph Wood (wood.ioe@epa.gov)

General Feedback/Questions Contact: (CESER@epa.gov)

21

U.S. Environmental Protection Agency, ORD

EPA/600/S-22/075 | September 2022

-------