Many people are afraid of radiation. They think of it as an invisible, man-made, lethal force, and this fear often underpins opposition to nuclear power.
In fact, most radiation is natural and life on Earth it would not be possible without it.
In nuclear energy and nuclear medicine we have simply harnessed radiation for our own use, just as we harness fire or the medicinal properties of plants, which also have the power to do damage.
Unlike of some toxins found in nature, humans have evolved to live exposed to low doses of radiation and only relatively high doses are harmful.
A good analogy for this is paracetamol: a tablet can cure your headache, but if you take a whole box at once, it can kill you.
The Big Bang, happened almost ,000 millions of years , generated radiation in the form of atoms known as primordial radionuclides (in this case primordial refers to the beginning of time).
These are now part of everything in the universe. Some have very long physical half-lives.
The half-life is the measure of how long it takes for half of its radioactivity to decay: for a radioactive form of thorium they are 14, million years, for a uranium 4, 500 million and one of potassium 1,300 millions.
Primordial radionuclides remain present today in rocks, minerals and in the soil.
Its decomposition is a source of heat inside the Earth, turning its molten iron core into a convection dynamo that maintains a magnetic field strong enough to protect us from cosmic radiation that would otherwise eliminate life on the planet.
Without this radioactivity, the Earth would have cooled down dually until it becomes a dead rocky globe with a ball of cold iron in the center and life would not exist.
Radiation from space interacts with elements in the Earth’s upper atmosphere and some minerals from the surface to produce new “cosmogenic” radionuclides, which include well-known forms of hydrogen, carbon, aluminum, and other elements.
Most decay rapidly, except for a radioactive form of carbon whose half-life is 5,700 years allows archaeologists to use it for dating by radiocarbon.
Primordial and cosmogenic radionuclides are the source of most of the radiation that surrounds us.
Plants absorb radiation from the ground and it is found in foods such as bananas, beans, carrots, potatoes, peanuts, and Brazil nuts.
The cerv Juice, for example, contains a radioactive form of potassium, but only about a tenth of that found in carrot juice.
Most of the radionuclides in food pass through our body and are eliminated, but some remain for a while (their biological half-life is the time it takes for our body to eliminate them).
That The same radioactive form of potassium emits high-energy gamma rays as it decays and escapes the human body, ensuring that we are all slightly radioactive.
Living with radioactivity
Historically, we have not been aware of the presence of radioactivity in our environment, but our bodies naturally evolved to live with it.
Our cells have developed protective mechanisms that stimulate DNA repair in response to radiation damage.
Natural radioactivity was first discovered by French scientist Henri Becquerel in 99.
The first artificial radioactive materials were produced by Marie and Pierre Curie in the decade of 1930 and have been used in science, industry, agriculture and medicine ever since.
For example, radiotherapy remains one of the most important methods for treating cancer.
To increase the potency of therapeutic radiation, researchers are currently trying to modify cancer cells so that they are less able to repair themselves.
We use radioactive material both for diagnosis and treatment in “nuclear medicine”.
Patients are injected with specific radionuclides depending on the part of the body where treatment or diagnosis is needed.
Radioactive iodine, for example, accumulates in the thyroid gland, while radium accumulates mainly in the bones.
The emitted radiation is used to diagnose cancerous tumors. Radionuclides are also used to treat cancer by directing the emitted radiation on a tumor.
The most common medical radioisotope is 99mTc (technetium), which is used in 30 millions of procedures each year worldwide.
Like many other medical isotopes, it is artificial, derived from a parent radionuclide that is itself created from the fission of uranium into a nuclear reactor.