The Health Effects Of Radioactive Elements

Nuclear radiation isn't just a single phenomenon, and the effects differ between elements, depending on the kind of radioactive decay they undergo and the parts of the body in which they concentrate.

Often three things fall under the catch-all term "radiation:" gamma rays, which are high energy photons (light), beta particles, which are electrons and positrons, alpha particles, which are helium nuclei, and neutrons.

Generally speaking, gamma radiation is dangerous at high doses but can be blocked by good shielding. Neutrons can be slowed down and stopped by shielding as well, usually an element that absorbs them such as cadmium or a material like water. Alpha particles don't penetrate the skin, but can be ingested or inhaled.

What follows is a quick guide to which elements are most common (and of most concern).

Strontium-90 has a half-life of 29 years. Non-radioactive strontium is harmless, but the radioactive form is a health risk because it behaves similarly to calcium. Even though most strontium is excreted, about a fifth of it stays in the body and concentrates in the bones and bone marrow. The result can be cancers. The radiation, like iodine, is in the form of beta decay, which turns it into yttrium-90, which then becomes zirconium.

Caesium-137 has a half-life of about 30 years. Caesium is a problem because it melts at relatively low temperatures – about 28 degrees C (83 degrees F) and can turn into small particles that can travel on the winds. Caesium dissolves in water and is toxic, even without being radioactive. While it is expelled from the body in a relatively short time – half is gone in one to four months – the chemical’s toxicity combined with the radioactivity can lead to cancers. The element tends to concentrate in bone and muscle tissue. Treatment to speed expulsion of Caesium involves giving patients Prussian blue, a chemical dye that binds to Caesium.

Plutonium (Pu) is used in nuclear reactors and weapons. In the Fukushima Daiichi reactor it is on the fuel rods as mixed-oxide, or MOX, fuel. There are several isotopes of Plutonium that nuclear reactions generate, among them plutonium-242, 240, 239 and 238. All have long half-lives, ranging from 87 years for Pu-238 to 376,000 years for Pu-242. Pu-239 and 240 last 24,100 and 6,560 years, respectively.
Plutonium, with its longer half-life, isn’t as “hot” as other radioactive elements. Radiation from plutonium is largely emitted as alpha particles, which can’t easily penetrate skin but can cause damage when inhaled or ingested. According to Dr. Ira Helfand, president of Physicians for Social Responsibility, a particle that weighs only a few millionths of a gram can cause cancer if it is inhaled. Plutonium can also be absorbed by bones and the liver after inhalation, as some forms dissolve and enter the bloodstream.

Iodine-131 is an isotope of Iodine. Iodine is essential in controlling metabolism, and concentrates in the thyroid gland, which is in the throat. Iodine-131 is a product of nuclear fission reactions, and has a half-life of about eight days, which means half of the element will decay into xenon-131 in that amount of time (xenon-131 is stable). While the half-life is short, the high concentrations of iodine in the thyroid can increase the risk of thyroid cancer from the radiation emitted by the iodine, which is largely in the form of gamma rays, electrons and positrons.

To slow iodine uptake in the body, people who may be exposed to radioactive iodine are given potassium iodide tablets, which saturate the body with non-radioactive iodine.