Radiation

On average, people in the Netherlands are exposed to 1.6 milliSievert (mSv) of natural background radiation per year. In other countries this may be higher or lower. For most people in Europe, the dose is between 2 and 5 mSv per year. In Finland, the figure is considerably higher: 7.5 mSv per year. The differences are related to soil conditions; the soil in Finland, for instance, contains a lot of granite, while the distance to the sun also plays a role. Your job, any medical treatment and any examinations you may undergo can also influence the amount of radiation you are exposed to. A pilot, who is often closer to the sun, may receive an additional 5 mSv per year. If you take a transatlantic flight yourself, you will receive about 0.05 mSv. And a ski instructor as much as 8 mSv per season. At higher altitudes, the atmosphere above a person is thinner and therefore offers less-effective protection. An X-ray will expose you to approximately 0.1 mSv of radiation. On average, every Dutch person receives 1 mSv per year as a result of air travel and treatments or examinations with radioactive substances. Together with the natural background radiation, we receive approximately 2.6 mSv of radiation per person per year in the Netherlands.

Radioactivity is the emission of ionising radiation by substances. To understand what this means, we need to look at the atoms that make up the substances. Atoms are the smallest chemical building blocks in the world around us. Radioactive substances contain atoms that are unstable and may emit radiation. By emitting radiation, a new atom is created. The emission of radiation continues until a stable atom is formed. Once all atoms have become stable, the substance is ‘decayed’ and can no longer emit radiation. Some radioactive substances decay quickly, within seconds, while others take hundreds of thousands of years. For example, the uranium contained in the earth is still radioactive today.

Ionising radiation is a collective term for high-energy radiation. It is also popularly referred to as radioactive radiation. The ionising radiation comes from space (from stars), is emitted by radioactive substances or is produced by devices. A well-known example of such a device is the X-ray machine in the hospital. Ionising radiation can have harmful effects on people or the environment and should therefore be used with care.

No, there are different types of radiation. The most common ones are alpha, beta and gamma radiation. Each type of radiation has its own specific properties. Alpha radiation, for instance, is already stopped by a sheet of paper and cannot travel more than 5 to 6 cm in air. While a 1.30-metre thick concrete wall may sometimes be necessary to stop gamma radiation.

Natural radiation or background radiation is radiation emitted by naturally radioactive substances. These substances can be found closeby in the earth (e.g. uranium) or in the concrete we use to construct buildings. Natural sources of radiation are even found in our own bodies. Some natural radiation comes from far away, e.g. from the sun, other stars and supernovas. Background radiation is not equal everywhere on earth. Some places naturally have more radioactive substances in the ground and have a much higher level of background radiation than others. Height also plays an important role: the higher up you are, the less atmosphere there is to protect you against cosmic radiation. Finland, for instance, has lots of granite in its ground. Granite contains considerable uranium levels. A Finn receives an average of 7.5 mSv (milliSievert) of background radiation, while a Dutchman receives an average of 1.6 mSv per year. The highest level of background radiation is measured in Ramsar, a city in the north of Iran. People there are exposed to a background dose of up to 260 mSv per year: over one hundred and sixty times more than in the Netherlands.