Alpha particles, which produce dense ionization, can only travel 1 or 2 centimeters in air and only up to about 70 micrometers into tissue. The penetrating power of alpha particles is very poor and can be stopped completely by a piece of paper. Since the outer layers of skin are dead and generally thicker than 70 micrometers, alpha particles externally would not generally cause biological damage. On the other hand, alpha particles that enter into the body present a more serious situation because the alpha particles are now adjacent to live tissue and could cause serious biological damage within that 70-micrometer track length. Inhalation and ingestion of alpha particles are therefore the primary concern with respect to personal protection. If a patient has been exposed to alpha radiation but is not contaminated, there is no need for personal protection whatsoever. However, if the patient has been contaminated with alpha-containing material, then removal of clothing and washing should be sufficient to protect the medical personnel from risk. In addition, application of a face mask and standard “universal precautions” (which will be described later in this chapter) should be sufficient for this purpose.

Beta particles have a range of energies, and their penetrating power depends on the initial energy of the particle concerned. There tends to be a range or spectrum of energies for beta particles. Beta particles typically travel 1 to 3 meters in air and just a few millimeters into tissue. Beta particles of higher energies can penetrate deeper into tissue. With internal intake of beta particles, the depth of penetration into live tissue would be the same. These particles can cause severe beta burns of the
skin as was seen in the Chernobyl accident. They may also cause severe internal damage if they enter the body via inhalation, ingestion, or wounds. To shield against beta particles, a light material such as aluminum is all that is required. In fact, it is preferable to use materials such as aluminum to prevent Bremsstrahlung radiation. Bremsstrahlung radiation occurs when beta particles come under the influence of a positive nucleus. As a result of such close proximity and bending around the nucleus, they slow down. As this occurs, it gives off heat and x-ray electromagnetic radiation. This is more likely to occur if a heavy material is used, such as tungsten. This is the principle of an x-ray machine.

Gamma rays, as with ordinary x-rays, penetrate right through the body. The gamma radiation interacts with the biological tissues and causes damage. Therefore this type of radiation can produce the acute radiation syndrome (Chapter 16). Shielding required for this type of radiation requires lead, concrete, or depleted uranium. Shielding attenuates this type of radiation but does not completely shield against it; however, the amount of gamma rays that penetrates the shield is so small that it is of no biological significance. An important point to mention here is that if a patient who has been irradiated by gamma rays only, this patient is not radioactive and is of no danger to the medical staff. The opposite may actually be true: the medical staff, with the bacteria they normally carry, can endanger an immunocompromised patient. The reason in mentioning this point is that there have been a few cases around the world where patients have been refused admission into the hospital because of concerns that they might contaminate the hospital. In these cases, there is no contamination, and there is no residual irradiation on the patient. There is therefore no danger the hospital or hospital staff. Consider a routine chest radiograph. After patients have a chest x-ray, they do not walk out of the x-ray department radioactive. The same principle applies to gamma exposures.

Criticality accidents involving neutron exposures may actually cause the patient to become radioactive. The sodium in our body has an affinity to capture neutrons, and in so doing it changes from the normal Na-23 to radioactive Na-24, which has a half-life of 15 hours. This can be detected simply by placing an instrument on the abdomen of the patient and having the patient bend over the instrument. The axillae may also be used for this purpose. The instrument will then detect any secondary gamma radiation. Neutrons are highly penetrating and are shielded by material of high hydrogen content such as wax or polystyrene.

Time is an important factor with respect to exposure; ideally the time spent in a radiation environment should be as short as possible. Experts, either at the scene of the incident or at the hospital emergency department, set specific limits of dose for responders in an emergency. The fact that such threshold levels are set does not mean that the responders really receive this dose of radiation. Ideally, one should rotate staff so that the dose is “shared,” keeping individual doses to a minimum. There is a much greater risk of exposure to high doses at the incident scene than in the hospital emergency department. In the hospital environment, the dose received by hospital staff is generally low. Nevertheless, the practice of rotating staff is important in both settings.

Distance is an important factor to take into consideration when dealing with radiation. A useful rule of thumb is to remember the inverse square law: by doubling the distance the dose is reduced to a quarter. In practical terms, the radiation dose will be markedly reduced if one works a few extra feet from the radiation source. If one considers being one foot away from a radioactive source and the dose recorded from the instrument reads 80 cGy (centi-Gray) by doubling the distance to 2 feet the instrument would read 20 cGy, a quarter of the original dose. By doubling the distance again to 4 feet, the dose would again be reduced by a quarter to 5 cGy. Therefore, by increasing the distance to 4 feet, the dose has reduced from 80 cGy to 5 cGy, for a total reduction in dose of 75 cGy.

When working very close to a contaminated patient, the converse of the inverse square law applies. If performing surgery or otherwise working in close proximity to the patients, the doses increase by the same “inverse square” principle. By halving the distance the dose would go up fourfold. As one approaches the source, the dose rapidly rises. On actual direct contact with the source, the dose could be very significant. It is important to remember to never pick up a source with your fingers, no matter how small it is. When working directly on wounds, it is preferable to use 6-inch swab forceps not your fingers. The dose resulting from direct contact of the wound with your fingers could be significant compared to the dose 6 inches away using forceps.

The quantity of radiation can be modified rapidly in a contaminated radiation incident simply by removing the clothing. This is particularly important if a large number of contaminated casualties arrive at your facility. Taking off the clothing reduces the contamination of the patient by approximately 85% to 90%. Each individual’s clothing should be double-bagged using polyethylene bags, which are labeled with the patient’s name, date of birth, and time the clothing was removed. This clothing must not be kept in the emergency department but instead should be placed outside the hospital in a designated area as determined by the health physicist. In this way, a build-up of radioactive material in the emergency department can be avoided, and
the staff will not be exposed to unnecessary irradiation. It is also important to remove all radioactive waste from the emergency department as soon as possible.

The preceding discussion endeavors to illustrate how the important principles of time, distance, shielding, and quantity of radiation are the key concepts to remember in protecting hospital personnel.

Emergency departments are often accustomed to receiving occasional chemical casualties, and usually a small area of an emergency department is designated for decontamination and care of these patients. Such a small area will most likely not be adequate in a terrorist event. Most of the area in the emergency department will be required for this type of event, remembering that it is easy to scale down but very difficult to scale up in an emergency. It is essential for the emergency disaster plan to include the possibility of radiation incidents. In a terrorist event, the number of people arriving at the emergency department may range anywhere from just a few people to a crowd involving thousands of people. With most serious disasters around the world, only the most seriously injured people have stayed at the accident site for initial triage. The vast majority of patients either found the hospital on their own or used public transportation. This was seen in the 1995 Japanese terrorist attack with sarin nerve agent. In that incident, approximately 500 people were taken to the hospital by the general public before the first ambulance arrived. Therefore, it is important that the hospital’s emergency plans be designed to cater to large numbers of people who require triage and decontamination.