3.3.2. Ionizing radiation

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3 3 2 radiaciones ionizantesHuman beings are exposed on a daily basis to natural radiation in the form of cosmic radiation; solar radiation; terrestrial radiation from radioactive material that may be in the soil, rocks, or minerals of the earth’s crust; and radiation from food and beverages that contain natural radioactive materials.

More than 70% of the general population’s exposure to ionizing radiation is estimated to be from natural sources. Consult information from Princeton University on the biological effects of ionizing radiation.

Radioactive substances are subject to spontaneous disintegration, which produces the phenomenon known as “ionizing radiation.” Exposure of human beings and other species to this radiation can have various effects on cells and live tissue, depending on the characteristics of the radiation, the nature of the exposure, and its duration.

The world’s major accidents involving radioactivity include the explosion of the nuclear plant at Chernobyl, in the Ukraine, on 26 April 1986. Materials on the event include:

- The causes of the Chernobyl event, describing the health effects of this event.

- A selection of photos illustrating the different stages of the accident through 20 years.

- A scientific report by WHO on the health consequences of the Chernobyl accident.

More recently, the direct impact of the major earthquake in Japan caused more than 15,000 deaths and 6,000 injuries. However, hundreds of thousands of people suffered and continue to suffer the consequences of the radioactive contamination produced. If not for the work of response personnel, this event could have been much more devastating than the nuclear accident at Chernobyl.

An accident at a nuclear plant can produce extensive environmental pollution by releasing radioactive materials into the atmosphere that spread over large regions, as particles are spread by the wind and permeate to the soil. Accidents involving a source of ionizing radiation used in industry or medicine can also contaminate, though in a more limited way.

People can be exposed in different ways—by inhalation, or by ingesting water or food (milk, vegetables, fish) from contaminated sources. Accidents can involve exposure or irradiation, or they can involve contamination. In exposure or irradiation, the risk is only to the exposed person, and is not transferable as long as the exposed person contains no radioactive elements. In contamination with a radioactive substance (for example, powder, liquid or waste), the person and even the person’s clothes can be impregnated and transfer the radiation to other people, objects, or the environment.

The harmful effects on health can be classified as acute (these are technically known as “deterministic” effects) and subsequent (“stochastic”). Deterministic effects include cutaneous burns, radiation disease, sterility, and death. Stochastic effects include cancer, and hereditary defects due to alteration of the genetic components of cells. More information can be found in the publication Public Health Consequences of Disasters (chapter 19 of which deals with accidents of nuclear reactors; see pp. 397-418).

The greatest risk of radiological emergencies is associated with medical equipment and materials—principally equipment and materials that are not regulated or registered. This type of risk can occur due to:

  • misuse of equipment;
  • loss of radioactive sources; and
  • leaks of radioactive materials.

Factors that aggravate the impact of the radiation include:

  • proximity to the source;
  • absence of a barrier;
  • exposure time;
  • quantity or dose of radiation;
  • part of the body exposed and characteristics of the person (age in particular, since the younger the person the graver the consequences of radiation, for radiation principally affects growth cells and causes genetic alterations, with the development cancer being a threat).

Lessons have been learned from major radionuclear accidents in the Americas. For more information, see (these presentations are in Spanish):

Contamination with cobalt steel (Mexico)

- Lessons learned in Goiania

- The nuclear accident in San Salvador

The following link provides a compilation of the nuclear accidents and incidents that occurred in Latin America and the Caribbean, between 1962 and 2000.

In preparedness and response planning for radioactivity emergencies, various possibilities must be taken into account. These include accidents that could occur in nuclear or industrial plants, those that could occur in medical diagnosis and treatment facilities, and those that could occur in transportation. Measures must be taken for prevention, medical care, and decontamination. For more information on the range of emergencies that can occur, potential health consequences, corrective actions, and guidelines for planning, consult the IAEA publication Arrangements for Preparedness for a Nuclear or Radiological Emergency.

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