Radiation Effects on Humans

Everybody knows that exposure to radiation can result in harmful effects on human health; courtesy accidents like the Three Mile Island accident (1979) and the Chernobyl Disaster (1986) that the world has witnessed over the last century or so. Basically, the severity of the effects of radiation on human body is determined by the amount of exposure, the ability of the radiation to harm the organ tissue, the organ that is affected, etc.

How Does Radiation Affect the Human Body?

Basically, there exist two different types of radiation - ionizing radiation (which includes alpha particles, beta particles, neutrons, etc.), and non-ionizing radiation (which includes visible light, infrared waves, radio waves, thermal radiation, etc.) It is the exposure to ionizing radiation, i.e. any radiation which has the ability to displace electrons from atoms or molecules which, in turn, results in production of ions, that has adverse effects on the human body. The unit used to measure a person's exposure to radiation is referred to as 'rem' (Roentgen equivalent in man). It is the total dose of radiation in rems which determines how radiation would affect the body. The harmful effects of radiation range from mild effects such as nausea and hair loss to severe effects such as hemorrhage and cancer. Severe exposure can even result in death of the individual.

Mild Radiation Sickness
Even though radiation exposure of up to 100 rems doesn't have any major implications of the body as such, temporary reduction in white blood cells can be observed in some cases. Some scientists also state that exposure as little as 20 rems can result in possible chromosomal damage in a long term. Exposure above 100 rems can result in mild radiation sickness - the symptoms of which start surfacing a few hours after the exposure. These include nausea, headache, diarrhea, fatigue, etc. The loss of white blood cells - which is much more prominent at this level of exposure, eventually hampers the resistance levels of the body and makes the person vulnerable to a range of other health problems. Diagnosis of mild radiation sickness is a difficult task as its initial symptoms like flu and headache go unnoticed in most of the cases unless the loss of white blood cells results in major problems.

Severe Radiation Sickness
If the exposure is above 200 rems, the person will experience severe radiation sickness and may even suffer a hemorrhage. The person may also experience temporary hair loss in clumps at this level of exposure. Approximately, 10-35 percent of those exposed to this amount of radiation end up dying. Any amount of exposure exceeding 300 rems can result in damage to bone marrow and small intestine. In this case the chances of person surviving are even less, with half of the people who are exposed to this level of radiation succumbing to its effects on various organs of the body within a period of 30 days. Furthermore, approximately 70-90 percent of the people who are exposed to radiation in excess of 400 rems end up dying as a result of organ failure.

Exposure above 1000 rems can have even serious implications on the body. When the person is exposed to this level of radiation exposure, the small blood vessels in the body are damaged and this invariably results in his death. The chances of survival for a person who is subjected to radiation exposure exceeding 1000 rems are less than 10 percent. As the brain cells don't reproduce, they don't get damaged directly unless the person is exposed to radiation above 5000 rems. At this level of exposure, radiation kills the nerve cells and small blood vessels in the brain - which in turn causes seizures and results in the person's death. All these effects of radiation on the basis of amount of exposure are based on studies. It is virtually impossible to say how much radiation dose the person has been exposed to, and that makes it even more difficult to deal with the situation.

Long Term Effects of Radiation Exposure
Radiation effects on DNA, wherein radiation exposure results in mutation of cells is one of the most prominent effect of ionization radiation in the long run. The mutations in this case can be teratogenic (which affects only the individual who was exposed) or genetic (the effects of which are passed on to the next generation). Radiation also results in changes to the genetic structure of the cells which results in abnormal cell growth, which eventually results in the formation of cancerous tumors. The aftereffects of Chernobyl disaster and Three Mile Island accident are seen even today with several people still suffering from health problems that are attributed to radiation exposure from these incidents.

When we talk about radiation effects, we most often take into consideration the effects of nuclear radiation on humans. However, radiation caused by x-ray exposure and radiation therapy is also known to be harmful for the body, and therefore there is a set limit up to which a person can be exposed to radiation even in the field of medicine. This limit is set with the objective of preventing acute exposure and limiting it to acceptable levels, as exposure beyond these limits can make the person vulnerable to various harmful effects of radiation.