recent cases of anthrax spores deliberately spread through the mail
reminded all Americans, and especially managers of federal and state
agencies responsible for public health and safety, about potential
terrorism with chemical and biological weapons. The anthrax cases
have also underscored the need for safer and more efficient methods
to decontaminate offices and homes of deadly biological agents.
During the late 1990s, scientists
at the Department of Energy national laboratories foresaw the need
for a safe, reliable, and easily deployable decontaminating agent
that could be used for civilian defense against biological and chemical
terrorism. DOE managers agreed with the scientists and asked them
to use their expertise in chemistry, biology, and environmental
protection to develop new decontamination products and procedures.
Lawrence Livermore responded
to this request with a team formed from the Environmental Protection
Department and three directoratesChemistry and Materials Science;
Nonproliferation, Arms Control, and International Security; and
Biology and Biotechnology Research. The team of diverse experts
developed a compound called L-Gel (the L is for Livermore), which
combines a mild, commercially available oxidizer with a silica gelling
agent to create a substance that coats walls, ceilings, and other
materials like a paint, effectively decontaminating the coated surface.
The material is nontoxic,
noncorrosive, easy to manufacture, easily deployable, and relatively
inexpensive (about $1 to cover a square meter). Tests at Livermores
laboratories and field trials at both federal and foreign facilities
have shown that L-Gel has been extremely effective at decontaminating
all classes of chemical warfare agents as well as surrogates for
biological warfare agents.
Livermore technology transfer
specialists are currently engaged in negotiations with several companies
to license the manufacturing and marketing of L-Gel. If negotiations
proceed apace, government agencies could have the material by the
end of the fiscal year (September 30) to respond to any terrorist
incident involving chemical or biological agents.
cross section of a bacterial spore, such as anthrax, shows its
hard, multilayered coats, which both make the spore difficult
to kill and allow it to remain dormant for many years.
Needs for Civilians
to L-Gel development leader Ellen Raber, a geochemist and head of
Livermores Environmental Protection Department, several decontaminating
agents are effective against either chemical or biological warfare
agents. However, these materials, which are mainly strong chemicals,
were developed by the military for battlefield use, and they pose
environmental and health risks when used in civilian settings. At
the minimum, they can damage everyday materials such as furniture
and office equipment.
Other methods that have been
used in civilian settings have serious drawbacks. For example, solutions
of laundry bleach work well as decontaminants but are very corrosive.
Incineration and irradiation have obvious practical limitations
in office settings or face public resistance. Chlorine dioxide gas,
used late last year to decontaminate the Hart Office Building that
houses members of the U.S. Senate, is a laborious process and poses
a safety risk to workers. It also requires the gassed building to
be neutralized before people can reenter.
The Livermore team focused
on finding an effective decontaminating agent and application system
that is safe to use, does not damage commonly used materials and
surfaces, is friendly to the environment, and is effective against
both chemical and biological warfare agents. We wanted something
that was less corrosive than bleach, that is easy to apply, and
that does not leave workers with a huge cleanup job, Raber
Raber points out that speed
of decontamination, which is all-important in military applications,
is less important in civilian applications, where decontamination
times of one to several hours may be adequate. More important in
a civilian scenario are ease of application, minimal training required
for use, moderate expense, and environmentally acceptable byproducts.
The team also recognizes
that the new product needs to be effective in three potential settings
of a terrorist incident against civilians: an outdoor location such
as a stadium, a semienclosed place such as a subway station, and
an enclosed space such as an office building. Using the decontaminating
material on interior surfaces can have quite different requirements
from those appropriate for outdoor use, where natural attenuation
from environmental conditions (for example, ultraviolet radiation
from sunlight) might well be adequate for effective decontamination.
biocidal effect of peroxymonosulfate, the oxidizer in L-Gel,
is seen on this nutrient agar plate of Bacillus subtilis spores
(surrogates for anthrax). Three spots of silica gel were added
to the plate. Two of the spots contained peroxymonosulfate and
one (at right) did not. The peroxymonosulfate-containing gel
inhibited spore germination in the zone surrounding the gel,
even leaching into the agar.
with the Oxidizer
The development effort began
with Livermore scientists Ray McGuire and Don Shepley evaluating
several acidic oxidizer solutions that could degrade chemicals into
nontoxic, environmentally acceptable components. (Oxidizing solutions
do not completely destroy chemical agents but rather break key chemical
bonds to render the toxic compound inactive.) The oxidizers considered
could be deployed in liquid spray systems or incorporated into compatible
gels for clinging to surfaces such as ceilings and walls.
McGuire chose an acidic rather
than a basic oxidizer solution, primarily to aid the decontamination
of VX, a potent nerve agent. Acidic oxidizer solutions are also
known to be effective at decontaminating certain biological warfare
agents, including bacterial spores, which are extremely difficult
to kill because of their hard, multilayered coats. The coat allows
a spore to remain in a dormant state for many years until, under
the right environmental conditions, it transforms into a live organism.
Anthrax is the most
difficult biological agent to kill because of its resistant outer
coat, says Raber. An oxidizer in acidic solution breaks down
the proteins that are found in anthrax coats. Once the oxidizer
gets through to the nucleus, its molecules destroy strands of the
anthrax DNA or RNA.
The goal was to find the
most effective oxidizer at the lowest effective concentration. The
oxidizers that were evaluated included potassium permanganate, peroxydisulfate,
peroxymonosulfate, hydrogen peroxide, and sodium hypochlorite. The
oxidants were evaluated in laboratory tests on chemical warfare
surrogates for such agents as VX, sarin (used in the Tokyo subway
terrorist incident), and sulfur mustard (used during World War I).
Livermore bioscientist Paula
Krauter evaluated the same group of oxidizers on surrogate biological
agents and toxins that would likely be used in terrorist attacks.
Bacillus subtilis was used for spore-forming agents such
as anthrax, Pantoea hericola was the surrogate for plague,
and ovalbumin was the surrogate protein for botulinum toxin.
The initial laboratory tests
showed that potassium peroxymonosulfate was more than 99 percent
effective at oxidizing both chemical and biological warfare surrogates
that were placed on common materials such as carpet, wood, and stainless
steel. The results led to the selection of Oxone, a commercial product
manufactured by DuPont, which contains potassium peroxymonosulfateits
active ingredientin a water solution. Previous research at
U.S. military laboratories had demonstrated the effectiveness of
Oxone in decomposing both VX and mustard-type agents, but the compound
had not been previously tested on biological agents.
Paula Krauter applies L-Gel to contaminated panels
of different materials to test the gels effectiveness.
Adds Staying Power
The team recognized that
spraying water-based solutions of Oxone would not be effective in
all cases. Consequently, McGuire and Mark Hoffman investigated carrier
materials that would thicken the oxidizer so it would better cling
to walls, ceilings, and other surfaces to increase contact time
with the biological or chemical agent.
Hoffman chose colloidal amorphous
silica as the carrier material for several reasons. First, unlike
crystalline silica, which is toxic, colloidal amorphous silica is
safe to use and is found in many household paint formulations. Also,
silicon dioxide colloidal particles are commercially available,
dont require manufacturing in a special facility, and, because
they are chemically inert, are compatible with oxidant solutions.
When mixed with the oxidizer, the gel can be applied with simple
delivery systems, such as paint sprayers. After application, it
thickens and tends not to sag or flow down walls or drip from ceilings.
Finally, silica gel materials can be easily vacuumed up after they
Livermore chemists have
extensive experience with colloidal silica gel. From the late 1960s
to the late 1980s, the chemists developed a series of extrudable
high explosives based on the gelling of energetic liquids. Although
this research did not advance to the explosives production stage,
the development effort provided useful experience for working with
silica-gel materials. It was a logical step to adapt this work to
the gelling of aqueous oxidizers for candidate decontaminants, says
Hoffman. Our research with high explosives gave us a good
feel for working with silica gels.
Hoffman selected Cab-O-Sil
EH-5 fumed silica as the gelling agent. The final formulation was
named L-Gel 115, which is a formulation of aqueous Oxone solution
gelled with 15 percent EH-5 silica gel. The viscosity can be varied,
depending on the application. Under development is a second formulation,
called L-Gel 200, which contains 10 percent t-butanol cosolvent
to promote penetration on surfaces with heavily coated paint or
was tested against surrogate spore-forming bacteria at the Soldier
Biological and Chemical Command at the U.S. Army Dugway Proving
Ground, Utah. In one test, surrogate organisms were placed on
six 40-square-centimeter panels of acoustic ceiling tile, tightly
woven carpet, fabric-covered office partition, painted wallboard,
concrete slab, and painted metal. L-Gel reduced the number of
live spores on most test panels by an average of 99.988 percent.
second test at the Dugway Proving Ground in Utah tested L-Gel
in a mock office setting.
Tests Prove Effectiveness
The final L-Gel 115 formulation
was subjected to a series of tests at Livermore facilities using
surrogates of potential terrorist chemical and biological agents.
The tests involved placing surrogate chemical and biological agents
on various common materialsvarnished wood, painted steel,
glass, fiberglass, and carpetadding L-Gel to the surface,
allowing the gel to dry for 30 minutes to several hours, and then
determining the percentage of surrogate that had been decontaminated.
L-Gel proved greater than 99 percent effective on all surfaces and
for all agents.
The Livermore biological
researchers also tested L-Gel on safe strains of the deadly biological
agents Bacillus anthracis (anthrax) and Yersinia pestis
(plague). These strainsSterne and Strain D27, respectivelycould
be safely used in experiments because they are nonvirulent, that
is, they do not contain the genes that create the lethal toxins
present in the real organisms. (See the article entitled Tracking
Down Virulence in Plague about research on sources and pathways
of virulence in organisms.) The researchers used the agar plate
resistance test, a standard technique to measure the efficacy of
antibiotics. In this test, about one million cells (or spores, in
the case of B. anthracis) were combined with liquid agar,
then poured onto a petri dish containing nutrients for cell growth.
The strains were also tested against dilutions of L-Gel, which proved
more than 99.9 percent effective in killing the cells and spores.
L-Gel also was tested against
surrogate spore-forming bacteria in two field exercises. In December
1999, researchers Krauter and Tina Carlsen participated in biological
warfare field tests that were conducted by the Soldier Biological
and Chemical Command at the U.S. Army Dugway Proving Ground, Utah.
The tests compared the ability of several decontamination materials
to inactivate surrogate organisms placed on six 40-square-centimeter
panels of acoustic ceiling tile, tightly woven carpet, fabric-covered
office partition, painted wallboard, concrete slab, and painted
metal. Each panel was contaminated with about 10 billion spores
per square meter.
is shipped premixed as a semisolid. It is reliquefied to a house-paint
consistency by vigorously shaking it by hand or using a power
After L-Gel was applied,
the panels were swabbed about 24 hours later. The number of live
spores on most test panels was reduced by an average of 99.988 percent.
In October 2000, Krauter
and Hoffman participated in a biological warfare agent room-decontamination
exercise that was conducted again at the Dugway Proving Ground.
The tests used full-scale, mock offices constructed in an abandoned
building. Flooring was divided into quarters consisting of carpet,
vinyl tile, varnished oak, and painted concrete. Walls consisted
of stucco, wood paneling, plasterboard, and carpet, and the ceiling
was constructed of suspended ceiling tile. The room was contaminated
with 4 grams of spores. After application of L-Gel, about 400 samples
were collected from multiple locations in the room. L-Gel reduced
the number of spores by about five orders of magnitude and, in these
experiments, did not damage office surfaces, with the exception
of bleaching some rust on ceiling supports.
L-Gel was also independently
tested on real chemical warfare agents at four locations from October
1998 to October 2000. The tests were conducted at the Military Institute
of Protection, Brno, Czech Republic; Edgewood Chemical and Biological
Forensic Analytical Center, Maryland; the Defense Evaluation and
Research Agency, United Kingdom; and the Soldier Biological and
Chemical Command at Dugway. Field tests showed that L-Gel was a
more effective decontaminant of real VX, GD (nerve agent), and sulfur
mustard than the current military standard, calcium hypochlorite,
on such materials as acrylic-painted metal, polyurethane-coated
oak flooring, and indooroutdoor carpet.
Two of the field trials also
demonstrated that the L-Gel 200 formulation has improved penetration
and thus promotes solution and oxidation in thickened chemical agents.
L-Gel 200 was tested on real chemical warfare agents such as thickened
distilled mustard and thickened soman (persistent nerve agent) as
part of the Restoration of Operations series of experiments at Dugway
Proving Ground. The agents were applied on steel test panels, Air
Force airground equipment paint, and Navy shipboard coating.
Clean Is Clean Enough?
When a terrorist attack on civilians potentially involves
biological or chemical warfare agents, decision makers
will need to make fast and informed choices about how
to respond. A team of Livermore researchers from the Safety,
Security, and Environmental Protection Directorate has
developed a process that guides users to make the best
emergency response decisions involving notification, identification,
characterization, decontamination, and cleanup.
In 1998, at the
request of DOEs Office of Nonproliferation and National
Security, the team developed a biological agent decontamination
plan in the form of a flowchart. It was then used
in a recommendation from the Environmental Protection
Agency to the National Security Council, the Presidents
principal forum for considering national security and
foreign policy issues. In 2001, the Livermore team added
chemical warfare agents to the plan, now termed the Chemical
and Biological Agent Decision Process.
The process helps
users to determine what actions need to be taken at the
outset; if an actual or potential impact to health, property,
or the environment exists; whether or not decontamination
is needed; what steps should be taken and when; and how
to verify that cleanup and remediation are complete so
that the area can be designated as safe to reenter or
Under the process,
each of four phases (notification, first responder, characterization,
and decontamination/remediation) progresses to the next
phase as soon as all its issues have been addressed. The
format includes numerous yes/no decision points and links
to more detailed information on specific topics. The decision
process takes into account different environments, such
as an outdoor site, and considers individuals in the general
population who may be at higher risk for illness and injury.
Raber, head of Livermores Environmental Protection
Department, the biological agent decontamination plan
addresses a need by several federal agencies for an up-to-date
summary of information necessary to evaluate acceptable
decontamination levels and procedures. The goal of the
plan is to help minimize the number of deaths and illnesses,
damage to the natural and built environment, and the extent
of economic damage (for example, crop or livestock damage)
resulting from a biological terrorism incident.
the plan, Livermore experts did a thorough literature
search and consulted with colleagues at the U.S. Army,
the U.S. Environmental Protection Agency, and federal
health agencies, including the U.S. Public Health Service.
The team noted that responding to a civilian event involves
different priorities than those for a military setting.
For example, during a battle, quick decontamination is
critical so soldiers can continue their mission. In a
domestic urban scenario, however, considerations of public
health and environmental issues are usually more important
than immediate decontamination. Also, the decontamination
process may need to be staged, with cleanup of gross contaminationfor
example, of puddles of toxic materialsfollowed by
more localized decontamination, such as cleaning up materials
The flowchart is structured so that cleanup criteria
are dependent upon the decontamination site. Much stricter
criteria are necessary for indoor settings such as offices
or homes than for outdoor scenarios where wind, sunlight,
temperature, and rain may effectively decontaminate
biological agents, toxins, and chemical warfare agents.
Raber says the
decision process must include answering the question,
How clean is clean enough? In this respect,
it is more difficult to establish target cleanup levels
for biological agents than for chemical agents, in large
part because of public acceptance and perception issues.
She notes that the public may demand zero living organisms
after decontamination, but achieving such a level may
not be practical or necessary. In the case of anthrax,
for instance, it takes about 6,000 inhaled anthrax spores
to cause respiratory anthrax. Furthermore, some biological
agents such as anthrax are already indigenous to many
farming communities and exist without incident. Zero
concentration of a biological agent and zero risk, in
many cases, are clearly not a necessity, she says.
Raber also points
out that it is possible to do a poor job of decontamination
and to make it look good by doing a poor job of sampling
and analysis. In the end, decontamination must
be defensible to regulatory agencies and to the public.
With L-Gels excellent
performance demonstrated in both laboratory and field trials, it
was time to partner with one or more commercial firms that could
manufacture the material quickly and efficiently. Fortunately, says
Raber, L-Gel is simple to manufacture. Its comparable
to mixing paint. L-Gel is relatively noncorrosive (its pH
is about 4, similar to that of vinegar or lemon juice), and Environmental
Protection Agency testing shows its residual materials to be nonhazardous.
It also meets the Department of Transportations nonhazardous
and noncorrosive requirements and is stable during shipping.
L-Gel is premixed and then
shipped and stored as a semisolid resembling Jello at room temperature.
If unopened, its shelf life is expected to exceed a year. It is
reliquefied to the consistency of house paint by vigorous shaking
by hand or a power stirrer.
It can be applied with any type of commercially available spray
device, whether airless or compressed-air units, with any stainless-steel
Although L-Gel clings to
walls and ceilings, it does not harm most painted surfaces or carpets.
Decontamination takes about 30 minutes. When dry (in about 1 to
6 hours), the gel residue, unreacted oxidizer, and decontaminated
chemical or biological agents can simply be vacuumed up and discarded
as nonhazardous waste. For outdoor use, no cleanup is required.
Raber says L-Gel compares
favorably to other decontamination methods that have been used recently
to kill anthrax spores. The tried-and-true method is a bleach solution.
However, bleach is extremely corrosive to metal surfaces and must
be used with care by cleaning crews.
A foam developed at Sandia
National Laboratories in New Mexico has also been effective for
decontaminating chemical and biological agents. This material is
sprayed on surfaces like a firefighting foam. Most of the foam dissipates,
and the residual material is then washed off. It has been used to
clean offices of Congress and at ABC News. Raber suggests that L-Gel
and the Sandia foam could work in tandem, with L-Gel sprayed on
walls and ceilings and the Sandia foam applied to large pieces of
equipment and floors.
Chlorine dioxide, used to
decontaminate U.S. Senate offices, is a gas that kills bacteria
but also is hazardous to human health and thus must be applied by
trained personnel. Afterward, its vapors must be sucked out of rooms
and then filtered through an ascorbic acid bath to decompose it.
Raber notes that gases and aerosols have clear advantages for decontaminating
ventilation systems and hidden spores, and research needs to continue
to find an environmentally safe gas or aerosol that is effective
for these applications.
Irradiation, popular in Europe,
kills bacteria and spores and is effective in decontaminating mail,
food, and other objects. However, the method requires large machines,
which are essentially small accelerators, and is not currently viable
for large-scale room decontamination.
chemist Mark Hoffman uses a household paint sprayer to apply
L-Gel to a test panel.
News about L-Gel has spread
rapidly, and Raber has been interviewed by several newspapers, television
stations, and National Public Radio. She has also received a large
number of inquiries from emergency response groups across the country
interested in additional information and samples.
The developmental work for
L-Gel 115 is complete, and Rabers team has begun to develop
a new formulation to decontaminate ventilation systems. Right
now, we dont have an easy way to decontaminate air ducts,
she says. The team is working on an encapsulation method to aerosolize
L-Gel (make it into tiny droplets) so that it could be blown into
In the meantime, licensing
of L-Gel manufacture is well under way, and Raber is hopeful that
major organizations will soon have an important yet nontoxic new
weapon to counter any biological or chemical attack.
Key Words: anthrax,
biological warfare, Chemical and Biological Agent Decision Process,
chemical warfare, decontamination, L-Gel, peroxymonosulfate.
information, contact Ellen Raber (925) 422-3985 (email@example.com).