Terror attacks using nuclear or radiation-related devices are an unequivocal threat in the twenty-first century and are capable of having unique medical and psychological effects. This chapter will focus on the most probable scenarios of possible attacks and the medical principles of handling such threats.
There are two major categories of potential terrorist incidents with widespread radiologic consequences. The first is the use of radiologic dispersal devices. This could cause a purposeful dissemination of radioactive material without nuclear detonation by using conventional explosives with radionuclides, attacking fixed nuclear facilities, or attacking nuclear-powered surface vessels or submarines. Malfunctioning nuclear weapons that are detonated with no nuclear yield (nuclear "duds") and installation of radionuclides in food or water are also possible means of generating a terror attack. The second and less probable scenario is the actual use of nuclear weapons. Each scenario has its own medical aspects, including "conventional" blast or thermal injury, introduction to a radiation field, and exposure to either external or internal contamination from a radioactive explosion.
Types of Radioisotopic Radiation
Isotopes of atoms with uneven numbers of protons and/or neutrons are typically unstable; such isotopes discharge particles or energy to matter, a process that is defined as radiation. The main radiation types are alpha, beta, gamma, and neutrons.
Alpha (α) radiation consists of heavy, positively charged particles that contain two protons and two neutrons. Alpha particles usually are emitted from isotopes with an atomic number of ≥82, such as uranium and plutonium. Due to their large size, alpha particles have limited penetrating power. Fine obstacles such as cloth and human skin usually can stop them from penetrating into the body, and they represent a small risk with external exposure due to their limited penetration. If they somehow are internalized, alpha particles can cause significant cellular damage in their immediate proximity.
Beta (β) radiation consists of electrons, which are small, light, negatively charged particles (about 1/2000 the mass of a neutron or proton). They can travel only a short finite distance in tissue, depending on their energy. Exposure to beta particles is common in many radiation accidents. Radioactive iodine released in nuclear plant accidents is the best known member of this group. Plastic layers and clothing can stop most beta particles, and their penetration is measured to be a few millimeters. A large quantum of energy to the basal stratum of the skin can cause a burn that is similar to a thermal burn and is treated as such.
Gamma (γ) rays and x-rays (both photons) are similar. Gamma rays are uncharged electromagnetic radiation discharged from a nucleus as a wave or photons of energy. X-rays are the product of abrupt mechanical deceleration of electrons striking a heavy target such as tungsten. Gamma rays and x-rays have similar properties, (i.e., no charge and no mass, just energy). Both travel easily through matter, sometimes called penetrating radiation, and are the principal type of radiation that causes total-body exposure. If the energy of gamma rays and x-rays is the same, their biologic effects will be the same.
Neutron (η) particles are heavy and uncharged, often emitted during nuclear detonation. They possess a wide energy range; their ability to penetrate tissues is variable, depending on their energy. They are less likely to be present in most scenarios of radiation bioterrorism.
The ionization resulting from protons, electrons, and gamma rays is either a direct or an indirect (i.e., mediated through water) effect of particles or photons on DNA. Ionization of DNA resulting from neutrons is secondary to the neutrons knocking electrons out of their atomic orbit and the formation of free radicals, which can also damage DNA directly.
The commonly used units of radiation are the rad and the gray (Gy). The rad (radiation absorbed dose) is energy deposited within living matter and is equal to 100 ergs/g of tissue.
The traditional rad has been replaced by the Syst`me Internationale (SI) unit of the gray; 100 rad = 1 Gy.
Whole-body exposure represents deposition of radiation energy over the entire body. Alpha and beta particles have limited penetration and do not cause significant noncutaneous injury unless emission results from an internalized source. Whole-body exposure from gamma rays, x-rays, or neutrons, which can penetrate through the body (depending on their energy), can result in damage to multiple tissues and organs. The tissue damage is proportional to the radiation exposure of the specific organ or tissue.
External contamination is a result of fallout of radioactive particles that land on the body surface, clothing, skin, and hair. This is the dominant element to consider in the mass casualty situation resulting from a radioactive terrorist strike. The common contaminants primarily emit alpha and beta radiation. Alpha particles do not penetrate beyond the skin and thus have minimal systemic effects. Beta emitters can cause significant cutaneous burns and scarring. Gamma emitters not only may cause local damage but also can cause whole-body radiation exposures and injury. The medical treatment is primarily decontamination of the body, including wounds and burns, to prevent the contamination from becoming internalized. Removing the contaminated clothing reduces the contamination significantly and is a first step in the decontamination process. Generally, patients will not constitute a significant radiation hazard to health care providers, and lifesaving treatment should not be delayed for fear of secondary contamination of the medical team. Any damage to health care personnel will depend directly on the duration of exposure and will be inversely proportional to the square of the distance from any radioactive source. Gowns that can be easily removed are essential to protect health care personnel.
Internal contamination will occur when radioactive material is inhaled or ingested or is able ...