Radiation poisoning is a rare but challenging condition. Dependence on nuclear energy and the expanded use of radioactive isotopes in industry and medicine have increased the possibility of accidental exposures. Ionizing radiation is generated from a variety of sources. Particle-emitting sources produce beta and alpha particles and neutrons. Ionizing electromagnetic radiation includes gamma rays and x-rays. In contrast, magnetic fields, microwaves, radio-frequency waves, and ultrasound are examples of nonionizing electromagnetic radiation.
Management of a radiation accident depends on whether the victim is contaminated or only irradiated. Irradiated victims pose no threat to health care providers and can be managed with no special precautions. In contrast, contaminated victims must be decontaminated to prevent the spread of radioactive materials to others and the environment.
A terrorist “dirty bomb” (dispersion bomb) will likely contain commonly acquired radioactive materials such as the following: americium (alpha emitter, found in smoke detectors and oil exploration equipment); cobalt (gamma emitter, used in food and mail irradiation); iridium (gamma emitter, used in cancer therapy); strontium (gamma emitter, used in medical treatment and power generation); and cesium (gamma emitter, used to sterilize medical equipment and for medical and industrial uses). Psychological effects (eg, panic) may overshadow medical concerns because significant acute radiation exposure by contamination is generally confined to the immediate blast area. Long-term exposure may increase the risk for cancer while adequate decontamination can be problematic, potentially making the blast area uninhabitable.
Mechanism of toxicity
Radiation impairs biological function by ionizing atoms and breaking chemical bonds. Consequently, the formation of highly reactive free radicals can damage cell walls, organelles, and DNA. Affected cells are either killed or inhibited in division. Cells with a high turnover rate (eg, bone marrow and epithelial coverings of skin, GI tract, and pulmonary system) are more sensitive to radiation. Lymphocytes are particularly sensitive.
Radiation causes a poorly understood inflammatory response and microvascular effects after moderately high doses (eg, 600 rad).
Radiation effects may be deterministic or stochastic. Deterministic effects are associated with a threshold dose and usually occur within an acute time frame (within a year). Stochastic effects have no known threshold and may occur after a latency period of years (eg, cancer).
Toxic dose. Various terms are used to describe radiation exposure and dose: R (roentgen) is a measure of exposure, whereas rad (radiation absorbed dose) and rem (radiation equivalent, man) are measures of dose. In the United States, rad is the unit of radiation dose commonly referred to in exposures, whereas rem is useful in describing dose-equivalent biological damage. For most exposures, these units can be considered interchangeable. The exception is alpha particle exposure (eg, plutonium), which causes greater double-stranded DNA damage and a higher rem compared with rad. The International System of Units (SI units) has largely replaced the rad and rem nomenclature. For conversion purposes, 1 gray (Gy) = 100 rad and 1 sievert (Sv) = 100 rem.
Acute effects. Exposure over 75 ...