Also consider the natural radiation exposure (natural radiation). It can be divided into external and internal irradiation. External radiation we are exposed to when travelling by plane, through the action of cosmic rays. For example, when hikes in the mountains You will be exposed to higher exposure to natural background radiation than the sea level. In other words, wherever we are, we still exposed to small radiation background (0.08 – 0.3 mSv/h). Such exposure is deemed acceptable. The internal exposure accounts for about 2/3 of the effective equivalent dose that a person receives from natural radiation sources that enter the organism with food, water and air.
The most significant contribution in natural irradiation of the person makes a radioactive gas radon, which accounts for 3/4 annual effective equivalent dose of radiation to human exposure. Radon is released from the bowels of the widely but unevenly, lodging in the rooms which is not ventilated. Also contains some building materials and some deep artesian water sources. Very great danger is water vapour radon content in the lungs, for example in the bathroom where he and his number is 3 times higher than the concentration of radon in the kitchen, and 40 times higher than in the room. In short, more often ventilate the premises.