It has been established that the basic background radiation on the planet (at least so far) is created due to natural sources of radiation. According to scientists share of natural radiation sources in the total dose accumulated average person throughout life, is 87%. The remaining 13% comes from sources created by man. Of these, 11.5% (or almost 88.5% of "artificial" component of radiation dose) is formed through the use of radioisotopes in medicine. And only the remaining 1.5% are the result of the effects of nuclear explosions, emissions from nuclear power stations, leakage from storage of nuclear waste and other cases
Among the natural sources of radiation first place confidently takes Radon, causes up to 32% of the total radiation dose.
This radioactive gas, perfectly transparent, has neither taste nor smell. Radionuclide gas radon-222 (along with iodine-131, tritium (3H) and carbon-14) are not detected by conventional methods. If there is reasonable suspicion of the presence of the above radionuclides, such as radon, it is necessary to use special equipment for measurements.
What is the danger of radon? As a gas, it enters the body through breathing and can cause adverse health effects, first of all - lung cancer. According to the US Public Health Service (US Public Health service) radon - the second most important cause of lung cancer in people after smoking.
Radon is formed in the interior of the Earth resulting from the decay of uranium, which, though in small quantities, but is a part of almost all types of soils and rocks. During radioactive decay of uranium is transformed into radium-226, from which, in turn, is formed and radon-222. Especially high uranium content (up to 2 mg / l) in granitic rock. Accordingly, in areas where the primary rock-forming element is granite, and you can expect the high content of radon. Radon seeps slowly from the depths to the surface, where once dispersed in the air, with the result that its concentration is negligible and poses no danger.
Problems occur when there is insufficient air exchange, for example, in homes and other buildings. In this case, the content of the radon enclosed room can reach dangerous concentrations. Since radon enters the building from the ground, in the west during the construction of foundations in the "radon" areas are widely used special protective membrane, preventing the infiltration of radon. However, even the application of the membrane does not give absolute protection. In the case where the supply water for the home are used well, radon enters the house with water and may also accumulate in significant quantities in kitchens and bathrooms. The fact that radon is very soluble in water and in contact with underground water radon, they quickly saturate the latter. In the US, the level of radon in groundwater ranged from 10 to 100 becquerels per liter (or similar Units), in some areas reaching up to hundreds or even thousands of Bq / l.
On the one hand, it falls with the water in the human digestive system, and on the other hand, people inhale secreted radon water during use. The fact that at the moment when water flows from the tap, radon is released therefrom, whereby the concentration of radon in the kitchen or bathroom may be 30-40 times greater than the level in the other areas (for example in the living room).
The second (inhalation) exposure Radon method is considered more dangerous to health.
Agency for the US Environmental Protection Agency (USEPA) recommends as the recommended limit value of radon content in water at a level of 300 pCi / l (which is 11.1 Bq / l ), Which, however, has not found yet reflected in the US national water quality standard (this parameter is not specified). In the recently published Radiation Safety Standards limit the level of radon in water, which has required intervention, set at 60 Bq / kg.
Yes, and quite effectively. One of the most effective ways to combat radon - aeration of water ( "bubbling" water with air bubbles, in which almost the entire radon literally "fly away in the wind"). Therefore, those who use tap water worry virtually nothing, as is standard aeration water treatment process at the municipal water treatment plants. As individual users downhole water, the studies USEPA, showed sufficiently high efficiency of the activated carbon. Filter based on the quality of activated carbon can remove up to 99.7% of radon. It is true over time, this figure falls to 79%. The use of coal to filter water softener ion exchange resins allows to increase the latter figure to 85%.