25. Exposures

Understanding the terrorist threat and detecting clues that an attack has occurred are critical to reducing morbidity and mortality.

Early detection, rapid decontamination, and immediate control over the radius of exposure are critical elements in the management of nuclear, radiologic, chemical and/or biologic exposures.

Protection of first responders, healthcare personnel, and the public is as important as caring for exposed individuals in order to minimize the overall impact of nuclear, radiologic, chemical and/or biologic exposures.

Common Causes to Remember

Toxic exposures as a result of warfare, terrorism, or occupational accidents typically fall into four broad categories.

Nuclear: detonation of an atomic bomb (e.g., World War II)

Radiologic: acute exposure to high doses of ionizing radiation (e.g., Chernobyl)

Chemical: exposure to one of several natural or engineered chemical agents (e.g., sarin)

Biologic: contact with highly pathogenic organisms (e.g., anthrax)

Epidemiology

The Global Incident Map (http://www.globalincidentmap.com) displays the enormity of the current global threat of terrorism.

High explosive events remain the most common type of terrorist activity and are therefore easy to detect; a higher index of suspicion is required to identify most nuclear, radiologic, chemical, and biologic (NRCB) attacks.

Nuclear and radiologic exposures

Two major databases track radiation accidents: Oak Ridge Institute for Science and Education (ORIS) in the United States and Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in Europe.

Between 1944 and 2000 ORIS and IRSN reported between 417 to 580 radiation accidents, with approximately 3,000 cases of acute radiation syndrome (ARS) and between 127 to 180 fatalities.

Approximately 10 million “sealed sources” of radioactive material exist in 50 countries; of the 612 “sealed sources” that were reported lost or stolen since 1995, 254 have not been recovered.

Chemical exposures

In 2008, there were 8,000 reported cases of organophosphate poisoning in the United States, resulting in 12 deaths; each year, almost 3 million people are exposed to organophosphate toxicity worldwide, resulting in over 300,000 fatalities.

The most common cause of cyanide poisoning in the United States is related to household fires; ~35% of all fire victims are reported to have dangerously elevated cyanide levels.

Between 1983 and 1988, chemical agents used in the Middle East resulted in excess of 15,000 fatalities.

Biologic exposures

World Health Association modeling predicts that 50 kg of anthrax aerosolized over an urban population of 5 million would result in 250,000 individuals contracting disease and 100,000 fatalities.

US Congressional Office of Technology Assessment estimates that 100 kg of aerosolized anthrax spores released over Washington, DC could result in 130,000 to 3 million deaths, matching the lethality of a nuclear weapon.

In 1984, the intentional use of salmonella to cause disease in over 750 people in Oregon highlighted the vulnerability of the US food and water supply and the potential to use common pathogens as biologic weapons.

Key Pathophysiology

Nuclear and radiologic exposures

Nuclear explosions are obvious and considered “overt” events; release of radionuclear material into the food/water supply or into ventilation systems is considered a “covert” event.

Mixed “overt” and “covert” events include the use of radiologic dispersion devices (“dirty bombs”), where the explosion would be rapidly detected, but the presence of radiation would only be apparent if detectors are used by first responders.

Most commonly used predictor of acute symptoms is the whole-body absorbed dose of gamma radiation (Gy = gray units).

Radiation sickness is caused by exposure to radiation doses > 0.1 Gy over a short period of time (e.g., > 0.1 Gy/h).

Chemical exposures

Most likely to occur within enclosed spaces (e.g., shopping malls) since effects of chemicals dissipate rapidly when victims are removed from the area of exposure.

Easily detectable in the sense that symptoms are rapid in onset and multiple people in close proximity will have similar presentations.

Each major category has specific mechanisms of action:

Asphyxiants (suffocation agents): interfere with the availability of oxygen for cellular respiration (e.g., hydrogen cyanide, arsine)

Cholinesterase inhibitors (nerve gases): inhibit acetylcholinesterase activity (e.g., sarin, VX)

Pulmonary irritants (choking agents): act directly by damaging upper airway and pulmonary tissue (e.g., chlorine, ammonia)

Vesicants (blistering agents): cause direct chemical burns in epithelial tissue; interfere with DNA synthesis and cell division (e.g., sulfur mustard, Lewisite)

Handheld chemical detectors exist; they are more accurate than handheld biologic detectors, but less reliable than radiation detectors

Biologic exposures

Terrorist use of biologic weapons would likely be through aerosol dissemination given the significantly higher likelihood of mass casualties.

The US Centers for Disease Control have identified a number of pathogens that could be used in biologic terrorism and ranked them:

Category A: can be grown easily in large quantities, are particularly well suited to airborne dissemination, and are resistant to destruction (e.g., anthrax, small pox)

Category B: moderately easy to spread, may require enhanced diagnostic or surveillance techniques to monitor, and generally less destructive than Category A (e.g., ricin, brucellosis)

Category C: include pathogens that could be engineered for mass dissemination because of ease of availability and have significant potential for morbidity and/or mortality (e.g., hantavirus, multidrug-resistant tuberculosis)

The US anthrax letter incidents in 2001 presented a novel method of biologic terrorism, which is less effective than high-volume aerosolized delivery, but is significantly more covert.