Monday Article #28 : Radiation: Good or Bad?

Radiation is defined as the emission or transmission of energy in the form of waves or particles through space or through a material medium. Through time, it has been perceived by many as a word with a negative connotation. However, in reality, we are constantly exposed to low levels of radiation known as background radiation, which is present on Earth at all times. Majority of this radiation occurs naturally from minerals either in the ground, soil, water and so on. This is known as terrestrial radiation. The human body even contains some of these naturally occurring radioactive minerals.

What actually causes adverse health effects is known as ionising radiation. This, in high doses, like any other toxins, can be lethal to the human body. Ionising radiations are high energy emissions that are robust enough to remove an electron from an atom or molecule, thus rendering them into an “ionised” state. This type of radiation is generally powerful enough to alter the structure of our body’s cells and lead to serious health issues. This is why we are advised not to have many X-rays per year - because the body is affected and has to repair itself afterwards. The extent of the potential damage depends on the duration of exposure, the radioactive isotopes involved, characteristics of the victim and so on.

On the electromagnetic spectrum shown below, there are two major categories of radiation, namely ionising and non-ionising. Ionising radiation has a short wavelength and a high frequency, thus it is high in energy. This explains why these rays produce enough energy to shake an electron off an atom with the ability to alter the chemical bonds and structure of a biological matter. Non-ionising radiation, on the other hand, has a longer wavelength and a lower frequency, hence lower energy. This type of radiation does not have enough energy to “kick” an electron off an atom hence it is generally perceived as safe. It is also classified as “non-thermal” because of the lack of heat energy.

What happens if we are exposed to high levels of ionising radiation?

After radiation exposure when radiation energy is released into the absorbing material, an electron would be displaced from its usual orbit and emitted from its atom. Electrons can be forced from their orbit by energy from radiation with a process called ionisation or electrolytic dissociation. This results in highly unstable ions called radicals. These radicals react with neighbouring atoms or molecules almost instantaneously.

In the human body, penetrative radiation can break H2O to produce OH radicals that are known to be the most potent in attacking various biomolecules including DNA, the genetic blueprint. Radiation also can directly hit DNA to produce radicals resulting in DNA strand breaks. Besides cell death or cell repairment, this often leads to severe genetic mutation and brings carcinogenic

(cancer-causing) effects.

The major types of DNA damage induced by ionising radiation include base and sugar damage, single-strand breaks, double-strand breaks, clustered DNA damage, and covalent intrastrand or interstrand crosslinking.

Case study: Chernobyl Disaster

The 1986 Chernobyl disaster was a nuclear accident that occured in the Chernobyl Nuclear Power Plant in the north of the Ukrainian SSR in the Soviet Union due to a flaw in the design of the nuclear reactor. This accident reached the maximum severity of 7 on the International Nuclear and Radiological Event Scale (INES), rated as the worst nuclear disaster in the history of the world. The accident caused the largest uncontrolled radioactive release into the environment ever recorded for any civilian operation, and large quantities of radioactive substances were released into the air for about 10 days. Two radionuclides, the short-lived iodine-131 and the long-lived caesium-137, were particularly significant for the radiation dose they delivered to members of the public. Radiation doses on the first day caused 28 deaths within 3 months. The doses received by the emergency respondent firefighters and power plant workers were high enough to result in acute radiation syndrome (ARS), which occurs if a person is exposed to an extremely high dose of radiation within a short time frame (usually minutes). The early symptoms of ARS are usually nausea, vomiting and a loss of appetite. In the following few hours or weeks, these initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follow.


Article by: Joyce Ong

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