Absorbed dose is defined as the amount of energy deposited by ionizing radiation in a substance. Absorbed dose is given the symbol D. The absorbed dose is usually measured in a unit called the gray (Gy), which is derived from the SI system. The non-SI unit rad is sometimes also used, predominantly in the USA.
Examples of Absorbed Doses in grays
We must note that radiation is all around us. In, around, and above the world we live in. It is a natural energy force that surrounds us. It is a part of our natural world that has been here since the birth of our planet. In the following points we try to express enormous ranges of radiation exposure, which can be obtained from various sources.
- 0.05 µGy – Sleeping next to someone
- 0.09 µGy – Living within 30 miles of a nuclear power plant for a year
- 0.1 µGy – Eating one banana
- 0.3 µGy – Living within 50 miles of a coal power plant for a year
- 10 µGy – Average daily dose received from natural background
- 20 µGy – Chest X-ray
- 40 µGy – A 5-hour airplane flight
- 600 µGy – mammogram
- 1 000 µGy – Dose limit for individual members of the public, total effective dose per annum
- 3 650 µGy – Average yearly dose received from natural background
- 5 800 µGy – Chest CT scan
- 10 000 µGy – Average yearly dose received from natural background in Ramsar, Iran
- 20 000 µGy – single full-body CT scan
- 175 000 µGy – Annual dose from natural radiation on a monazite beach near Guarapari, Brazil.
- 5 000 000 µGy – Dose that kills a human with a 50% risk within 30 days (LD50/30), if the dose is received over a very short duration.
As can be seen, low-level doses are common for everyday life. The previous examples can help illustrate relative magnitudes. From biological consequences point of view, it is very important to distinguish between doses received over short and extended periods. An “acute dose” is one that occurs over a short and finite period of time, while a “chronic dose” is a dose that continues for an extended period of time so that it is better described by a dose rate. High doses tend to kill cells, while low doses tend to damage or change them. Low doses spread out over long periods of time don’t cause an immediate problem to any body organ. The effects of low doses of radiation occur at the level of the cell, and the results may not be observed for many years.