Defense Against Toxic Weapons: Protecting Health Care Providers

Defense Against Toxic Weapons: Protecting Health Care Providers

by David R. Franz

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.