Foods contain radioactive substances.
The various elements contained in foods are used to maintain human and animal life. A typical element contained in food is potassium. Potassium is an essential element for living organisms. A certain percentage however consists of potassium-40, which emits radiation. The figure shows the amount of potassium-40 contained in 1 kg of food.
Japanese people are exposed to approximately 1 mSv per year from radioactive substances contained in foods eaten on daily basis. In addition, in Japan, people are exposed to approximately 1 mSv per year from space and the earth, so their exposure from the natural world totals approximately 2 mSv. Note that the becquerel is a unit indicating how much radiation is emitted from an object. The sievert is a unit used when thinking about the effects of radiation.