A non-living energy can cause life

Radiation and its effect on the organism

We encounter radiation everywhere in our environment. It comes from space, from the microwave, from the transmission mast or from radioactive traces in the rock. Many forms of radiation penetrate the body every day without endangering health. But some can damage cells from a certain dose. In these cases, protective measures are necessary.

The term radiation describes the propagation of waves and particles in space. It thus covers the entire spectrum of electromagnetic waves, starting with low-energy, low-frequency infrared thermal radiation in the kilohertz range. These include, for example, heat radiation from the sun or microwave radiation. The visible light that our eyes can perceive has a higher frequency with wavelengths of 400 to 700 nanometers. Short-wave UV light, which the sun sends to the earth and which can cause sunburn and, in the worst case, even skin cancer, can be dangerous.

Ionizing and non-ionizing radiation

Radiation can interact with matter depending on the type and energy content of an individual "radiation particle". Electromagnetic radiation through to UV radiation belongs to non-ionizing radiation; although they can cause particles to vibrate and thus heat substances, they cannot break the bonds within an atom or molecule. It is different with ionizing radiation, it can knock electrons out of atomic shells. What remains are ionized, i.e. charged, atoms and molecules. These can trigger further reactions and thereby damage cells or cell components in the body.

Ionizing radiation includes electromagnetic waves with a length of less than 200 nanometers such as UV, altitude, X-ray and gamma radiation. Its frequency is in the zeta heart range, i.e. \ (10 ​​^ {21} \) oscillations per second. A single radiation quantum (“photon”) of this high-energy electromagnetic radiation has an energy of a few electron volts (eV) up to several million electron volts (MeV). The cosmic radiation, also known as cosmic radiation, mainly affects molecules in the upper layers of the atmosphere. X-rays are an important tool in medicine, but the radiation dose for the patient must not be too high.

Gamma radiation

Gamma radiation occurs when many radioactive elements decay, when part of the energy is given off in the form of radiation. It has a long range and can easily penetrate matter, so thick layers of lead or concrete are required for shielding. When it passes through human tissue, some of it is absorbed. Electrons can be released from the atomic shell and the genetic material of the cells can be damaged so that they no longer divide properly. This is why so-called radiation sickness, which is triggered by brief, very high levels of radiation exposure, often only leads to death after a while.

Radioactivity is also the source of particle beams in which electrons, protons, neutrons or atomic nuclei, for example, are released instead of electromagnetic waves. They also have an ionizing effect. A distinction is made between alpha and beta radiation as well as neutron radiation.

Alpha radiation

Warning of radioactive material

Alpha radiation consists of doubly positively charged helium nuclei, each composed of two protons and two neutrons. It arises from the alpha decay of radioactive nuclei. When slow alpha particles interact with atoms, they can trap electrons from the atomic shell, and the helium nuclei become the noble gas helium.

The helium nuclei have a strong ionizing effect on matter. The distance of alpha radiation in air is short, however, depending on the energy of the particle and the prevailing air pressure, it is usually only a few centimeters. That is why a sheet of paper is enough to shield them. In order to protect yourself from alpha radiation, you should therefore keep a distance from the radiation source.

Alpha particles penetrate organic material with an energy of five electron volts (eV) up to 40 micrometers. In humans, this corresponds to the topmost layers of skin, which only consist of dead cells. The situation is much more critical when radioactive substances, in which the alpha decay takes place, are ingested in increased concentrations through food or inhalation. The radiation then arises in the body and, at high doses, can damage living cells and cause cancer.

An alpha emitter is the radioactive isotope radon-222, which occurs in the air. It arises from the decay of uranium, which is contained in small doses in rocks in the earth's crust. This means that uranium is also a natural component of mineral building materials. The concentration of radon-222 in the outside air and inside buildings is, however, well below the limit values ​​of the Federal Office for Radiation Protection. Since radon is heavier than most of the other air components, the concentration of radon is higher in basements than in other rooms. Hence the name "cellar gas" for radon.

Beta radiation

Beta radiation consists either of electrons or their positive siblings, the positrons. It arises from the beta decay of radioactive isotopes. A distinction is made between beta (+) and beta (-) decays. Beta (-) decay occurs in atomic nuclei with an excess of neutrons. One of the neutrons in the nucleus transforms into a proton, emitting an electron and an antineutrino. The beta (+) decay occurs when the number of protons is high. A proton is transformed into a neutron by emitting a positron and a neutrino.

The energy distribution of beta radiation from radioactive nuclei is very different and ranges up to two MeV. In air, the range of beta radiation from the phosphorus isotope 32 (1.7 MeV) can be up to seven meters; the range of beta radiation from tritium (19 keV), on the other hand, is only eight centimeters. Layers of denser materials such as aluminum, glass or Plexiglas shield beta radiation from a thickness of just a few millimeters.

If beta radiation penetrates the body tissue superficially, it can cause burns or skin cancer, depending on the energy content and amount. The absorption of beta emitters can cause massive damage to internal organs such as the thyroid gland. The thyroid absorbs iodine atoms of all kinds. If the ingested food contains radioactive isotopes of iodine-131 instead of the stable iodine-127 or if these are inhaled, they are stored in the thyroid gland and can cause cancer there. Under certain conditions, damage caused by iodine-131 can be prevented by taking iodine tablets (see info box: iodine tablets).

Strontium-90 accumulates in the bones because it is chemically similar to calcium and is accordingly absorbed by the body. In high doses, its radiation can lead to bone cancer and leukemia. Strontium-90 occurs in very small doses in food, the values ​​are only around 0.003 millisievert per year and are controlled by the Federal Research Institute for Nutrition and Food.

Neutron radiation

Neutron radiation is generated in particular during nuclear fission - the process by which energy is generated in nuclear reactors. Nuclear fission is only possible with heavy atomic nuclei such as uranium-235. A neutron that penetrates the uranium nucleus makes it unstable, the nucleus divides into two lighter nuclei and emits two or three neutrons, which in turn can trigger a reaction in neighboring nuclei - the nuclear chain reaction. Since the neutrons are electrically neutral, they can penetrate very deeply. When colliding with hydrogen in the tissue, recoil protons are created, which in turn have a strong ionizing effect, and gamma radiation. The effect is therefore similar to that of gamma radiation, but the probability of damage is higher at the same dose. In our environment, however, there are no natural radiation sources that emit neutron radiation.

Neutrons that are produced in nuclear power plants can be slowed down by materials with a high hydrogen content, for example water, polyethylene or paraffin. In order to capture them completely, absorbers such as boron or cadmium are then used. The resulting gamma radiation in turn requires protection made of lead or concrete.

Natural sources of radiation in our environment

Measurement of the radiation dose in Sievert

Humans are constantly exposed to a low dose of radioactive radiation. The noble gas radon-222 has already been mentioned as an example. Another source is the radioactive carbon isotope14C, also called C-14 or carbon-14, which is produced by cosmic radiation in the atmosphere. It is produced by plants through COabsorbed and thus also enters the metabolism of animals and humans. Its half-life is very high at 5730 years, it is not dangerous for humans.

We also ingest radioactive substances such as potassium-40 with our food. Potassium is an important mineral. If you add up the amounts of radioactive substances that we ingest through food and breath, the result for a person living in Germany is an average radiation dose of 2.4 millisieverts per year.

Protection against increased radiation exposure

People who are exposed to increased radiation exposure should adhere to the "four A" basic rules: The radiation must be shielded with suitable materials, the time spent in the radiation field should be as short as possible, but the distance to the source as large as possible. Finally, the activity of radiation sources that are consciously used should be kept as low as possible. Dose limit values ​​that indicate the point at which the absorbed dose is assessed as dangerous are also used for radiation protection.