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��22. THE EFFECTS OF RADIATION ON THE HUMAN BODY EXERCISE 1 Fill each gap with a missing preposition. Radiation is energy that moves through space or matter 1) ______________ a very high speed. This energy can be 2) ______________ the form of particles, such as alpha or beta particles, which are emitted from radioactive materials, or waves such as light, heat, radiowaves, microwaves, x-rays and gamma rays. Radioactive materials, also known as radionuclides or radioisotopes, are atoms that are unstable. In nature, there is a tendency 3) ______________ unstable atoms to change into a stable form. As they change form, they release radiation. Radiation that can produce ions when it interacts 4) ______________ matter is called ionizing radiation. Ions are the charged particles that are produced when electrons are removed 5) _______________ their positions in the atoms. Alpha particles, beta particles, x-rays and gamma rays are forms of ionizing radiation. On the other hand, radiation that is not capable 6) _____________ producing ions in matter is known as nonionizing radiation. Radiowaves, microwaves, heat waves, visible light and ultraviolet radiation are forms of nonionizing radiation. Ionizing radiation affects health when it causes changes 7) _______________ the cells of the human body. It does this 8) ______________ breaking the chemical bonds that hold together groups of atoms called molecules. For example, DNA molecules, which contain a person s genetic information, control the chemical and physical functions of human cells. If damaged, the DNA molecules are able to repair the damage 8) _______________ most cases; but in some instances, damage to DNA molecules will affect the ability of the cells to do their work and to pass information 10) _______________ new cells. EXERCISE 2 Put the words in bold in the correct form. Health effects from radiation Generally speaking, there are two types of health effects from radiation threshold and non-threshold effects. THRESHOLD EFFECTS High doses of radiation received in a short period of time result in effects that are 1) NOTICE ____________________ soon after exposure. These are known as threshold effects. A certain dose range must be exceeded before they can occur. These effects include radiation 2) SICK ____________________ and death, cataracts, 3) STERILE ____________________, loss of hair, reduced thyroid function and skin radiation burns. The 4) SEVERE ____________________ of these effects increases with the size of the dose. NON-THRESHOLD EFFECTS There are other health effects of radiation that generally do not appear until years after an exposure. It is 5) ASSUMPTION ____________________ that there are no threshold doses for these effects and that any radiation exposure can increase a person s chances of having these effects. These are called non-threshold effects. They can occur in the person who receives the radiation dose or in that person s children. In the latter case, they are known as genetic effects. Genetic Effects No increase of genetic effects from radiation exposure have been found in humans. However, there have been a number of animal 6) INVESTIGATE ____________________ that have shown that exposure to fairly high doses of radiation increases the chances of genetic effects in the 7) SPRING ____________________ of the exposed animals. Even though genetic effects have not been found to increase in exposed human populations, it is safer to assume that there is an increased chance of these effects, even at low radiation doses. Fetal Effects The embryo/fetus is particularly sensitive to radiation. Some studies have shown increases in the rates of 8) CHILD ____________________ cancer in children exposed to radiation before birth. Cancer Cancer is the most common non-threshold effect of high radiation doses in humans. The cancers caused by radiation are no different from cancers due to other causes. Radiation has been found to induce cancer in most body tissues and organs. Different tissues and organs, however, show varying degrees of sensitivity. The tissues and organs showing high sensitivity include bone marrow (leukemia), breasts, thyroid glands and lungs. In contrast, there is no clear evidence that radiation causes cancer of the cervix or prostate. Some people are more sensitive to 9) HARM ____________________ effects of radiation than others. There are a number of factors that influence an individual s sensitivity to radiation. These factors include age, gender and genetic factors. Age In general, exposed children are more at risk than adults. Breast cancer risk among women exposed to radiation is greatest among women who were exposed before age 20, and least when exposure occurred after menopause. Also, exposed children are at greater risk of radiation-induced thyroid cancer than adults. Gender In women, the risk of breast and 10) OVARY ____________________ cancers from radiation is high, but there is no clear evidence that radiation causes breast or prostate cancers in men. Females are also seen to have more radiation-induced thyroid cancer than males. Genetic Factors Individuals with certain pre-existing genetic diseases have increased sensitivity to radiation, especially if they receive radiation therapy. For example, children genetically 11) PREDISPOSITION ____________________ to cancer of the retina and who are treated with radiation are at increased risk of developing bone cancer following 12) TREAT ____________________. EXERCISE 3 Match the opposites. 1 to affect a to demonstrate 2 to induce b to observe 3 to decrease c to examine 4 to occur d to reduce 5 to develop e to influence 6 to show f to get 7 to investigate g to harm 8 to receive h to cause 9 to damage I to evolve 10 to notice j to happen LISTENING You will hear a conversation between two people who have just met at the party. they are talking about tourism. Write YES next to opinions which the man expresses and NO next to opinions he does not express. 1 Tour operators make too much money out of package holiday. 2 Tourism usually improves life for the inhabitants of poor countries. 3 Responsible tour operators accommodate their clients in a variety of locally-owned hotels. 4 Hotels should support local industries and services. 5 The woman should look for a job in the tourist industry. 6 Visitors to developing countries should spend more money outside their hotels. 7 The food in local restaurants is healthier than hotel food.

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