Explain how excessive exposure to radiation can cause harm.

Authors Avatar by sherrylima (student)

M4 – Explain how excessive exposure to radiation can cause harm.

The amount of radiation given to patients in diagnosis is dependent on how close vital organs and tissues are to the malignant tumour, there are two terms commonly used by scientists when dealing with radiation doses, absorbed dose, the amount of energy received by a mass of tissue, which is measured in kilograms (Kg), It has the unit J/Kg and is called the gray (Gy). Effective dose, if the ionising radiation types are compared using the same amounts of energy, alpha particles cause much biological damage, 20 times more damage than X-rays. In medicine radiation affects different tissues and organs in different ways and so each tissue or organ has a number which is used as a quality factor, the absorbed dose is multiplied by this number to give the figure for effective dose, also measured in J/kg b called Sievert (Sv).

Major effects of ionising radiation on the body

Injury to living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionizing radiation causes atoms and molecules to become ionized or excited. These excitations and ionizations can:

  • Produce free radicals.
  • Break chemical bonds.
  • Produce new chemical bonds and cross-linkage between macromolecules.
  • Damage molecules that regulate vital cell processes (e.g. DNA, RNA, proteins).

The cell can repair certain levels of cell damage. At low doses, such as that received every day from background radiation, cellular damage is rapidly repaired. At higher levels, cell death results. At extremely high doses, cells cannot be replaced quickly enough, and tissues fail to function.

Although a dose of just 25 rems causes some detectable changes in blood, doses to near 100 rems usually have no immediate harmful effects. Doses above 100 rems cause the first signs of radiation sickness including:

  • nausea
  • vomiting
  • headache
  • some loss of white blood cells

Doses of 300 rems or more cause temporary hair loss, but also more significant internal harm, including damage to nerve cells and the cells that line the digestive tract. Severe loss of white blood cells, which are the body's main defence against infection, makes radiation victims highly vulnerable to disease. Radiation also reduces production of blood platelets, which aid blood clotting, so victims of radiation sickness are also vulnerable to haemorrhaging. Half of all people exposed to 450 rems die, and doses of 800 rems or more are always fatal. Besides the symptoms mentioned above, these people also suffer from fever and diarhea. As of yet, there is no effective treatment--so death occurs within two to fourteen days.

Join now!

In time, for survivors, diseases such as leukaemia (cancer of the blood), lung cancer, thyroid cancer, breast cancer, and cancers of other organs can appear due to the radiation received.

Tissue Sensitivity

In general, the radiation sensitivity of a tissue is: Proportional to the rate of proliferation of its cells, Inversely proportional to the degree of cell differentiation. For example, the following tissues and organs are listed from most radiosensitive to least radiosensitive:
 

This also means that a developing embryo is most sensitive to radiation during the early stages of differentiation, and an embryo/foetus is more sensitive to radiation exposure ...

This is a preview of the whole essay