X-ray Hazards
The biological effects of radiation are thought of in terms of their effects on living cells. For low levels of radiation, the biological effects are so small they may not be detected in epidemiological studies. The body repairs many types of radiation and chemical damage. Biological effects of radiation on living tissue may result in a variety of outcomes, including:
Cells experience DNA damage and are able to detect and repair the damage.
Cells experience DNA damage and are unable to repair the damage. These cells may go through the process of programmed cell death, or apoptosis , thus eliminating the potential genetic damage from the larger tissue.
Cells experience a nonlethal DNA mutation that is passed on to subsequent cell divisions. This mutation may contribute to the formation of a cancer.
Cells experience "Irreparable DNA Damage." Low level ionizing radiation may induce "Irreparable DNA damage" (leading to replicational and transcriptional errors needed for neoplasia or may trigger viral interactions) leading to pre-mature aging and cancer.
Other observations at the tissue level are more complicated. These include and in some cases, a small radiation dose reduces the impact of a subsequent, larger radiation dose. This has been termed an 'adaptive response' and is related to hypothetical mechanisms of hormesis.
Chronic radiation exposure
Exposure to ionizing radiation over an extended period of time is called chronic exposure. The natural background radiation is chronic exposure, but a normal level is difficult to determine due to variations. Geographic location and occupation often affect chronic exposure.
Acute radiation exposure
Acute radiation exposure is an exposure to ionizing radiation which occurs during a short period of time. There are routine brief exposures, and the boundary at which it becomes significant is difficult to identify. Extreme examples include:
Instantaneous flashes from nuclear explosions.
Exposures of minutes to hours during handling of highly radioactive sources.
Laboratory and manufacturing accidents.
Intentional and accidental high medical doses.
The effects of acute events are more easily studied than those of chronic exposure.
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