Tritium costs $ 30 thousand per gram. It is used to write self-luminous signs "exit" in theaters, schools and offices. Tritium is a radioactive isotope of hydrogen (hydrogen-3, 3 H) with an atomic mass of 3 (one proton, two neutrons). The half-life of tritium is 12.34 years. For decays, tritium is converted into helium, giving off the rather intense beta radiation. True energy of beta particles are relatively small, so when you find out the body (external radiation) tritium is not a serious threat. Another thing is that the internal exposure (by ingestion of tritium inside the human body with air or water) can pose a serious threat to health. The fact that tritium, an isotope of hydrogen being chemically behaves like hydrogen, and therefore it can replace hydrogen in all the compounds with oxygen, sulfur, nitrogen, easily penetrating into the cytoplasm of every cell. In this case, emitted by tritium beta radiation can cause seriously damage to the genetic apparatus of cells. Studies on the behavior of tritium in biological objects show sometimes thousand-fold accumulation in living organisms and food chains. Fortunately, in natural terrestrial ecosystems (excluding the bowels of the planet), there is almost no tritium. Only trace amounts of the interaction of cosmic radiation with atmospheric gases are produced. On the Earth there can hardly be typed more than 1 kg of natural tritium. However, in recent decades, the main source of tritium are the nuclear power plants. Tritium is a major component of the radioactive liquid effluents and gaseous emissions of most nuclear power plants, as it is virtually impossible to filter. This leads to the contamination of the soil, groundwater and surface water around the plant. It has long been shown that in the vicinity of some U.S. plants tritium content in the needles of the trees on the windward side is 10 times greater than the downwind, direct proof that this plant is the source of tritium. These and other specific features can be attributed to tritium among the most radiation-hazardous long-lived nuclides, which can contaminate the biosphere, not only in the direct placement of the source, but also regionally and globally. Obviously, these considerations led to the incorporation of tritium into the list of monitored radiological parameters in the new EU directive on drinking water quality.