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Radiation

Radiation definition:

Radiation is defined as a transmission or emission of energy in the form of waves or particles through space or through a material medium according to physics.

Radiation has dual nature photons (particles) and waves.

Types of radiation:

  1. Electromagnetic radiation: radio waves, microwaves, infrared, visible light, ultrasound, x-rays, & gamma radiation.
  2. Particle radiation: alpha radiation beta radiation, neutron radiation.
  3. Acoustic radiation: seismic waves and ultrasonic waves.
  4. Gravitational radiation: radiation that takes the gravitational waves formation.

Radiation is further categorized in ionizing radiation and non-ionizing radiation.

Ionizing radiation: The radiation which dissociate the matter into ions by breaking chemical bonds. The energy carried by ionizing radiation is very high i.e. >10eV, and able to ionize the molecule and atoms.

Non-ionizing radiation: The radiation which is not able to dissociate or ionize the atoms and molecules.

Sources of radiation

Natural source of ionizing radiation: We get natural radiation from the food we eat, the air we breathe, the water we drink ever the human body give off the radiation i.e. infrared radiation. The ionizing radiation produced from natural and man-made radioactive materials. At present the environment contain natural occurring radioactive elements like uranium, thorium, actinium and potassium-40. These elements exist in the material that makes the planet Earth. We also get radiation from the atmosphere this radiation comes from outer space and known as cosmic radiation.

There are the types of natural source of radiation:

  1. Terrestrial radiation: The radiation which comes from the soil, rocks or mountains in which the natural radioactive materials continuously dissociates and gives radiation.
  2. Sun: This source gives ultraviolet radiation which is very harmful to all living things.
  3. Internal radiation: This type of radiation is received within the body of the various mammals by the ingestion of the food particles and some ions present on their bodies like Ca2++ Mg2+ K+ Cl etc.
  4. Cosmic radiation: They are the major natural source of radiation which is continuously providing external exposure to all the living beings. The major source of this radiation is Earth’s atmosphere and magnetic field originating from the gravitational force of the Earth. People living at sea levels receives an average dose of about 0.3milli sievert while the people living at high altitudes may receive a radiation does up to 0.02-0.08 milli sievert.
  5. Radon gas: It is a gas which is present in the form of a radio nuclei originates from the Earth’s crust. This gas is produced from the decay of uranium238, when this gas is inhaled by the living beings it causes respiratory system disorders with alpha particles. This gas causes cancer in both smokers and non-smokers.
  6. Sources from food and drinks: Food materials and water may contain radioactive particles which is easily transferred into the alimentary canal of living being. Many non-vegetarian food materials contain high amount of lead and polonium which gives high radiation dose to the internal structure and organs. For example: fish, red meat, lichen etc.

Artificial source of ionizing radiation: the artificial radiation is that radiation which is produced artificially for the various purpose. There are three main sources for artificial ionizing radiation:

  1. Medical devices: The use of radiation in hospital to diagnose various disease place an important role to provide high amount of radiation dose to the world population. Approximately 98% radiation is produced from the artificial sources.
  2. Diagnostic radiology: The diagnostic radiology produces the image of internal anatomical structures by using x-ray machines, CT scan machines and fluoroscopy machine. These imaging modalities using the ionizing radiation and contributes in radiation exposure. Interventional radiology or Cath lab department also uses radiation producing devices for the diagnosis and treatment of blood vessels.
  3. Nuclear medicine: In nuclear medicine department the radioactive materials or drugs are used. They are introduced into the body of humans and produce images of internal structures. The nuclear medicine department is mainly concern with the treatment of malignancy disorders.
  4. Radiotherapy/radiation therapy: The radiation therapy department use a very high amount of radiation for the treatment of the cancer and benign tumors. Radiation therapy machine uses the radioactive material cobalt 60.

Radiation units

  1. Roentgen: It is the amount of radiation that ionizes fixed amount of gas or air. This is the unit of the radiation exposure. This radiation unit of radiation exposure is measured in coulomb/kg.
  2. Curie: This radiation unit is defined as the rate of disintegration of a radio nuclei material which is measures as 3.7×1010 Becquerel.
  3. RAD (Radiation Absorbed Dose): It is the amount of radiation absorb per unit mass of the absorbing medium.
  4. REM (Roentgen Equivalent Men): It is the amount of radiation received by a tissue or organ which is equal to the standard dose.

Radiation protection:

There are the main principles of radiation protection:

  • Distance: Distance is the first principle of the radiation protection. When the distance from the radiation source is increased the radiation dose of the living beings the radiation reduces to half. Therefore, the distance should be maintained from a radiation source.
  • Time: Time is the second principle of the radiation protection. When the time of radiation exposure is minimum then the effect due to radiation will be minimal. Therefore, the exposure time will be minimally used.
  • Shielding/radiation protection devices: The term shield refers to the protection of any biological tissue or organ from any type of radiation. Many devices are used to protect humans from radiation, which includes eye-shield, thyroid-shield. Mammary shield and gonadal shield. These radiation protection devices are filled with lead of different thickness.

Radiation side effects or radiation hazards

Radiation side effects (Biological effects): These effects may damage cells and may produce any abnormality after the deposition of ionizing radiation into the tissue and structures. There are the following radiation side effects:

  • Somatic effects: These cells are present in the entire body, the radiation effect on these cells effects the rate of the cell division. These cells have mitochondria, Golgi bodies and cell nuclei. These components are very sensitive to radiation exposure, their function and growth are affected by radiation exposure and may cause death of the cells. There are three types of somatic effects:
  1. Immediate effects: These radiation side effects can be seen within a week or in the day of the radiation exposure. These side effects include hair loss, redness to the skin and skin burn or radiation burn.
  2. Intermediate effects: These radiation side effects can be seen within one or up to three months. These side effects include the digestive system problems, and also effect the function of bone marrow and secretion of the hormones and enzymes.
  3. Delayed effects: These radiation side effects can be seen after 2 months o up to 1 year after the radiation exposure. These effects may produce carcinogenic disorders, fetal abnormalities and shortening of life. This type of radiation side effects is not irreversible.
  • Genetic effects: This radiation side effect may affect the genes and chromosomes of the gonadal cells that effects the future generations. Genetic information for the production and function of an organ is present in the chromosome of germ cells i.e. sperm and ovum. These radiation side effects may immediate or delayed depending on the amount of radiation exposure.

Radiation sickness: The radiation sickness is the damage to the human body caused by a large dose of radiation exposure.