RADIOISOTOPES

1. Dangers associated with radioisotopes

Radiation produced during the decay of radioisotopes (notably γ-rays and high-energy β-rays) is of very high energy, and is called IONIZING RADIATION. This can cause atoms to ionize:

The ions produced in this way cause damage to sensitive organic substances in the cell, eventually leading to the death of cells. This is called SOMATIC DAMAGE, and can result in severe short-term or long-term effect. Alternately, damage can be caused to the DNA in reproductive cells, leading to GENETIC DAMAGE which may then be transmitted to subsequent generations. This is one way in which mutations can arise, and such mutations nearly always possess undesirable characteristics.

γ-Rays are not the only sources of dangerous ionizing radiation: X-rays also fall into this category. α-Emitters are also dangerous if they get into the body, as the α-particles are heavy and can transfer their kinetic energy to large number of atoms, causing them to ionize. Within the human body, α-emitters such as polonium-210, Po210, are extremely dangerous. Polonium can concentrate in vital organs, and deliver the radiation right where it can cause the most damage (). Outside the body, α-particles cannot penetrate through the skin.

What is all the fuss about "uranium enrichment"?

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3. Uses for radioisotopes

Radioisotopes have the same chemical properties as non-radioactive isotopes of the same element, and thus various compounds can be labeled with minute amounts of a radioisotope, which are easily detectable and quantified. This leads to a number of uses, four of which are given below.

The radiocarbon produced in the atmosphere is spread throughout the atmosphere and the oceans, thus forming a "reservoir" of radiocarbon. Living organisms pick up this isotope, which "labels" all tissues. In living organisms, the 14C/12C ratio is about 1x10-12. When the organism (a tree, for example) dies, the uptake of 14C ceases, and the radioactive carbon atoms undergo β-decay at a known rate: ()

The residual radioactivity of a sample of wood from that tree can be measured and an estimated age for the specimen determined, either by measuring the residual radioactivity, or, more accurately, by actually counting the remaining 14C atoms by a technique known as "accelerator mass spectrometry". This method is widely used in archaeology, and is limited to samples not exceeding about 50 000 years in age (). For longer periods of time, other isotopes are used. It is untrue to say "radioactive carbon is used to date dinosaur fossils"!

3. Additional questions