element. There may be several isotopes of an ypes of Radiation element. Hydrogen, for instance, has three isotopes: TAlpha radiation consists of positively charged hydrogen-1 (common hydrogen), hydrogen-2 particles comprising two protons and two neutrons, (deuterium) and hydrogen-3 (tritium). which are emitted by radionuclides of heavy elements such as uranium, radium, radon and adioactivity and Radiation plutonium. International Atomic Energy Agency and Although many nuclides are stable, most are R Alpha World Health Organization not. Stability is determined mainly by the balance radiation between the number of neutrons and the number of travels only BASICS OF RADIATION protons a nucleus contains. An unstable nucleus has a few AND RADIATION PROTECTION excess energy and will spontaneously disintegrate at centimetres random by emitting radiation. Different nuclei in air and is adiation is a fact of life: all around us, all the release their energy in different ways, in the form of blocked by R time. We live in a naturally radioactive world. electromagnetic waves — gamma or X rays — a sheet of paper. Alpha radiation is not able to But how much do physicians, nurses and medical and/or streams of particles, i.e. beta or alpha penetrate skin. If an alpha emitting substance is technicians who may have to respond in a radiation particles. This taken into the body, it will release all its energy to emergency know about what radiation is, what it 14 140 spontaneous C β Ba β, γ the surrounding cells. Alpha-emitters can be does and how to protect against it? This leaflet is 6 56 disintegration 5730 y 12.8 d harmful to humans if the materials are inhaled, directed at medical personnel and outlines basic of nuclei is 14 140 swallowed or absorbed through open wounds. Beta concepts of radiation and radiation protection. N La β, γ called radio- 7 57 radiation consists of electrons, which are much stable activity and toms and Elements 40.3 h smaller than alpha particles and are able to penetrate 140 the excess AAll matter consists of atoms. Nearly all of an Ce deeper. It can be stopped by a sheet of metal or 58 energy emitted atom’s mass is concentrated in the nucleus, which stable glass or by ordinary clothing. Beta radiation can is a form of consists of positively charged protons and penetrate human skin to the ‘germinal layer’, where ionizing radiation. The process of disintegration is electrically neutral neutrons. Negatively charged new skin cells are produced. If beta emitters remain termed radioactive decay and the unstable nuclide particles called electrons orbit the nucleus. Atoms on the skin for a long period of time, they may which disintegrates and emits radiation is called a have equal numbers cause skin injuries. Gamma radiation is radionuclide. All radionuclides are uniquely of protons and electromagnetic wave energy. Its range in air is long identified by the type of radiation they emit, the electrons and are and its penetrating power substantial. Dense energy of the radiation, and the half-life. The electrically neutral. materials such as lead and concrete are good activity — used as a measure of the amount of a The total number of barriers against gamma rays. X ray radiation is radionuclide present — is expressed in a unit called protons and neutrons similar to gamma radiation but is usually produced the becquerel (Bq): one becquerel is one is called the mass artificially by bombarding a metal target with disintegration per second. The half-life is the time number. Since the electrons in a vacuum (in an X ray tube). Dense required for the activity of a radionuclide to number of protons is unique to each element, the materials such as lead stop X rays. Neutron decrease to half of its value by decay. Half-lives for element together with the mass number specify each radiation consists of neutrons and is not in itself radionuclides range from tiny fractions of a second nuclide. The nuclides of an element — atoms with ionizing radiation. However, if a neutron hits a to millions of years. the same number of protons but different numbers nucleus, it may activate it or cause the emission of a of neutrons — form what are called isotopes of that gamma ray or charged particle, indirectly giving adiation and Living Tissue internal and may be incurred by various exposure rise to ionizing radiation. Neutrons are more RWhen radiation passes through matter it pathways. External exposure may be due to direct penetrating than gamma rays and can be stopped deposits some of its energy in the absorbing irradiation from a sealed source or due to only by a thick barrier of, for example, concrete, material by ionization or contamination, i.e. airborne radionuclides or Charged particles water or paraffin. excitation of the atoms. It is radionuclides deposited onto the ground or onto ionization of atoms in tissue, clothing and skin. Internal exposure may result adiation Dose accompanied by chemical Electrical interactions from the inhalation of radioactive material in air, the Radiation damage to tissue depends on the R changes, that causes the harmful ingestion of contaminated food or water, or absorption of energy from the radiation or on the biological effects of radiation. Ionization contamination of an open wound. Effective Absorbed dose dose of radiation received, For instance, when ionizing protection from external exposure is provided by: 1) Energy imparted by radiation called the absorbed dose. to standard mass of tissue radiation passes through cellular limiting the time spent near the source of radiation; [Gy] Absorbed dose is expressed Chemical changes tissue, it produces charged 2) moving away from the source of radiation; and 3) in a unit called the gray (Gy). water molecules. These break shielding from the source, the effect of which The damage producing Equivalent dose up into free radicals, which are Biological effects depends on the type of radiation emitted and the Absorbed dose weighted potential of a given absorbed for harmfulness of different highly reactive chemically and can alter important nature of the shielding material used. In types of radiation [Sv] dose depends on the type of molecules such as deoxyribonucleic acid (DNA) in contaminated areas, protective clothing helps to radiation. An absorbed dose cells. Radiation can also ionize DNA molecules prevent external body contamination and Effective dose from alpha particles, for Equivalent dose weighted directly. These effects of ionization can lead to appropriate respiratory protection helps to prevent example, is more harmful for susceptibility of biological effects, including cell death and abnormal internal contamination. Eating, drinking and different tissues to harm than the same dose from beta [Sv] cell development. smoking should be forbidden in contaminated areas. radiation. To put all ionizing radiation on common ground with regard to adiation Effects a Radiation Emergency potential for causing harm, a radiation weighted RThere are two main types of radiation health InAny physician may have to take care of dose called the equivalent dose is introduced. The effects. Deterministic effects occur only if the dose victims of radiation exposure. A patient who has unit is the sievert (Sv). The equivalent dose is equal or dose rate (i.e. the dose per unit time) is greater been exposed only to an external source of radiation to the absorbed dose multiplied by a radiation than some threshold value. The effects occur early and is not contaminated poses no radiation hazard to weighting factor. For gamma rays, X rays and beta and are more severe for higher doses and dose rates. others and no precautions are needed. If the patient particles, the factor is set to 1. For alpha particles Examples are acute radiation syndrome, skin burn is contaminated internally, precautions are needed the factor is 20. In addition, the risk of harm is not and sterility. If the dose is low or delivered over a when dealing with excreta, but he/she does not the same for the various tissues in the body. For longer period of time, there is a greater opportunity represent a direct hazard to others unless the intake example, it is lower for the bone surfaces than for for the body’s damaged cells to repair themselves; was extremely large and involved gamma emitters. the tissue of the breast. This can be taken into however, harmful effects may still occur. Effects of If the patient is externally contaminated, proper account by taking the equivalent dose in each of the this type, called stochastic, are not certain to occur, procedures (e.g. wearing vinyl gloves and mask, major organs and tissues of the body and weighting but their likelihood increases for higher doses, covering the patient with a blanket or sheet, it by a factor related to the risk of harm for that whereas the timing and severity of an effect do not washing hands and keeping them away from the organ or tissue, called the tissue weighting factor. depend on the dose. Examples are cancers of mouth) help to prevent the spread of contamination The sum of the weighted equivalent doses is called various types. and inadvertent ingestion by physicians, nurses or the effective dose. The effective dose gives a broad others. adiation Exposure and Radiation Protection indication of the detriment to health. RExposure of a person may be external or