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Defense Against Toxic Weapons: Protecting Health Care Providers
by David R. Franz
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Defense Against Toxic Weapons
Answers to Often-Asked Questions
PROTECTING HEALTH-CARE PROVIDERS
For the same reason that decontamination is only moderately
important after personnel are exposed to a respirable toxin aerosol,
health-care providers are probably at only limited risk from
secondary aerosols. Because toxins are not volatile, casualties can,
for the most part, be handled safely and moved into closed spaces
or buildings, unless they were very heavily exposed. Prudence
dictates, however, that patients be handled as chemical casualties
or, at a minimum, that they be washed with soap and water. The
risk to health-care providers is of greater concern with some agents.
Secondary exposure might be a hazard with very potent bacterial
protein toxins, such as botulinum toxin or the staphylococcal
enterotoxins. (Note that decontamination and isolation of patients
or remains could be much more important and difficult after an
attack with a bacteria or virus that replicates within the body.)
Remains of persons possibly contaminated with toxins should be
handled as chemically contaminated remains. For the most part,
toxins are more easily destroyed than chemical agents, and they are
much more easily destroyed than spores of anthrax. Chemical
disinfection of remains in 0.2% sodium hypochlorite solution for
10 minutes would destroy all surface toxin (and even anthrax
spores), greatly reducing the risk of secondary exposure.
SAMPLE COLLECTION: General Rules for Toxins
Identifying toxins or their metabolites (break-down products) in
biological samples (blood, urine, feces, saliva or body tissues) is
difficult for several reasons. In the case of the most toxic toxins,
relatively few molecules of toxin need be present in the body to
cause an effect, therefore, "finding" them requires extremely
sensitive assays. Secondly, the most toxic, and most likely to be
seen on the battlefield, are proteins, a class of molecules which our
bodies break down and process. Therefore, these toxins and pieces
of them after breakdown often "blend into the scenery" of the body
and, at some point, are no longer identifiable.
Typically, we must look for the toxin itself or its metabolites, not
an antibody response, as can be done with infectious agents. It is
very unlikely that anyone receiving a lethal dose of any of the
toxins would live long enough to be able to mount an antibody
response. However, with certain protein toxins (ricin and the
staphylococcal enterotoxins) that are highly immunogenic and less
lethal, one might expect to see antibodies produced in soldiers who
received a single exposure and survived. These might be seen as
early as two weeks after exposure.
Certain toxins can be identified in the serum of animals, therefore
probably humans, exposed by inhalation. Blood samples should be
collected in sterile tubes and kept frozen, or at least cold,
preferably after clotting and removal of cells. If collected within the
first day, swab samples taken from the nasal mucosa may be useful
in identifying several of the toxins. These too, should be kept cold.
As a general rule, all samples that are allowed to remain at room
temperature (approximately 75-80 F) or above for any length of
time will have little value.
Biological samples from patients are generally not as useful for
diagnosis of intoxications as they ar for diagnosis of infectious
diseases. The same is true of postmortem samples. The literature
suggests that botulinum toxins can be isolated from liver and
spleen, even when they cannot be isolated from blood. We can
identify ricin with immunoassays in extracts of lung, liver, stomach
and intestines up to 24 hours after aerosol exposure. We have
identified high doses of ricin in fixed lung tissue of aerosol-
exposed laboratory animals by immunohistochemical methods. The
staphylococcal enterotoxins can be detected by immunoassay in
bronchial washes. Like blood and swab samples, postmortem tissue
or fluid samples should be kept cold, preferably frozen, until they
can be assayed.
Environmental samples from munitions or swabs from
environmental materials should be placed in sealed glass or Teflon~
containers, and kept dry and as cold as possible. Handling a dry or
powdered toxin can be very dangerous, because the toxin may
adhere to skin and clothing and could be inhaled.
TOXIN ANALYSIS AND IDENTIFICATION
Immunological and/or analytical assays are available for most of the
toxins discussed in this document. Immunological methods,
typically enzyme-linked immunosorbent assays (ELISA) or
receptorbinding assays, are sensitive to 1-10 nanograms/milliliter
and require approximately 4 hours to complete; these are being
developed as the definitive diagnostic tests for deployment.
Analytical (chemical) methods are sensitive at low microgram to
high nanogram amounts, and take approximately 2 hours to run,
plus time for instrument setup and isolation or matrix removal
when necessary; the latter can add days to the process. A small,
sensitive, far-forward, fieldable assay for several toxins has been
developed and similar kit assays are being developed for many of
the other toxins described in this document. The polymerase chain
reaction (PCR) technique, which provides very sensitive means of
detecting and identifying the genetic material (DNA) of any living
organism, can be used to detect remnants of the bacterial, plant or
animal cells that might remain in the crude, impure toxin one would
expect to find in a weapon. Finally, a new method of combining
immunoassays with PCR may allow us to detect extremely small
quantities of the toxins themselves. In their present state, PCR
assays are primarily suited for use in the reference laboratory.
WATER TREATMENT
Questions often arise regarding the protection of water supplies
from toxins. It is unlikely that a typical small-particle aerosol attack
with toxins would significantly contaminate water supplies.
Furthermore, as a general rule, direct contamination of water
supplies by pouring toxins into the water would require that it be
done downstream of the processing plant and near the end user,
even for the most toxic bacterial toxins-and normal chlorination
methods are effective against some of the most potent toxins.
Because of dilution, adding toxins to a lake or reservoir would be
unlikely to cause human illness. Natural production of algal toxins
(e.g., microcystin) in stagnant bodies of water could produce
enough toxin to cause illness if that water were used for drinking.
The following methods of water purification have been tested for
the toxins listed.
Reverse osmosis systems are effective against:
Ricin-64,000 daltons (molecular weight)
Microcystin-1,000 daltons
T-2-466 daltons
Saxitoxin-294 daltons
(Botulinum toxin-150,000 daltons and SEB-28,494 daltons not tested: expect same result)
Coagulation/flocculation
Not effective for removing ricin, microcystin, T-2 or saxitoxin from water.
Chlorine
Five milligrams/liter (5 parts per million) free, available chlorine (household bleach) for 30 minutes destroys botulinum toxin. This concentration does not inactivate ricin, microcystin, T-2 or saxitoxin.
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