We are all radioactive, so let’s stop being afraid of it. Radiation is even in foods such as bananas, beer, beans, carrots, potatoes, peanuts.
Many people are afraid of radiation, viewing it as an invisible, artificial, and deadly force, and this fear often underlies opposition to nuclear power. In fact, most radiation is natural and life on Earth 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, both of which have the power to harm. Unlike some naturally occurring toxins, humans have evolved to live with exposure to low doses of radiation and only relatively high doses are harmful. A good analogy for this is paracetamol – one tablet can cure your headache, but if you take a whole box all at once it can kill you.
The Big Bang, nearly 14 billion years ago, generated radiation in the form of atoms called primordial radionuclides (primordial meaning since the beginning of time). These are now part of everything in the universe. Some have very long physical half-lives, a measure of how long it takes for half of their radioactivity to decay: for a radioactive form of thorium it is 14 billion years, for a uranium 4.5 billion and a potassium of 1.3 billion.
The primordial radionuclides are still present in rocks, minerals and soils today. Their decay 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 shield us from cosmic radiation that would otherwise wipe out life on Earth. Without this radioactivity, the Earth would have gradually cooled to become a dead, rocky globe with a cold iron ball in its center and life would not exist.
Radiation from space interacts with elements in the Earth’s upper atmosphere and certain surface minerals to produce new “cosmogenic” radionuclides, including forms of hydrogen, carbon, aluminum and other well-known elements. Most decay quickly, except for a radioactive form of carbon whose half-life of 5,700 years allows archaeologists to use it for radiocarbon dating.
Primordial and cosmogenic radionuclides are the source of most of the radiation that surrounds us. Radiation is picked up from the ground by plants and occurs in foods such as bananas, beans, carrots, potatoes, peanuts and Brazil nuts. Beer, for example, contains a radioactive form of potassium, but only about a tenth of that found in carrot juice.
Radionuclides from food largely pass through our body, but some remain for periods of time (their biological half-life is the time for our body to eliminate them). This same radioactive form of potassium emits high-energy gamma rays as it decays which escape the human body, ensuring that we are all mildly radioactive.
Living with radioactivity
Historically, we have been oblivious to the presence of radioactivity in our environment, but our bodies have 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 1896. The first man-made radioactive materials were produced by Marie and Pierre Curie in the 1930s and have since been used in science, industry, l agriculture and medicine.
For example, radiotherapy is still one of the most important methods for treating cancer. To increase the power of therapeutic radiation, researchers are currently trying to modify cancer cells to make them less able to repair themselves.
We use radioactive materials for both diagnosis and treatment in “nuclear medicine”. Patients receive injections of specific radionuclides depending on where in the body treatment or diagnosis is needed. Radioactive iodine, for example, accumulates in the thyroid gland, while radium accumulates mainly in the bones. The radiation emitted is used to diagnose cancerous tumors. Radionuclides are also used to treat cancers by targeting their emitted radiation to a tumour.
The most common medical radioisotope is 99mTc (technetium), which is used in 30 million procedures every year worldwide. Like many other medical isotopes, it is man-made, derived from a parent radionuclide which itself is created from the fission of uranium in a nuclear reactor.
Radiation scare could boost fossil fuels
Despite the benefits that nuclear reactors offer us, people fear the radiation they create, either due to nuclear waste or accidents such as Chernobyl or Fukushima. But very few people have died from nuclear power generation or accidents compared to other primary energy sources.
We are concerned that the fear of radiation is undermining climate change mitigation strategies. For example, Germany currently generates around a quarter of its electricity from coal, but considers nuclear power unsafe and is shutting down its remaining nuclear power plants.
But modern reactors create minimal waste. This waste, as well as waste inherited from old reactors, can be immobilized in cement and glass and stored deep underground. Radioactive waste also does not generate carbon dioxide, unlike coal, gas or oil.
We now have the understanding to harness radiation safely and use it for our benefit and that of our planet. If we fear it too much and reject nuclear power as a primary energy source, we run the risk of depending longer on fossil fuels. It is what, not radiation, endangers us and the planet.
(By Bill Lee, Bangor University and Gerry Thomas, Imperial College London)