Abstract Environmental tritium are natural and anthropogenic origins, the distribution has spread in atmosphere, hydrosphere and biosphere as a variety of chemical forms. The natural tritium is produced by nuclear reactions of neutron with N and O in the upper atmosphere, the production rate changes with 11-year cycle of the solar activity. The production and radioactive decay of natural tritium is balanced on the whole earth, results in the inventory of about 1 EBq. Anthropogenic tritium by nuclear weapons testing had been released in 1950s–1960s, at highest intensity just before the Partial Test Ban Treaty in 1963, and the total release would be 186 EBq. In accordance with a peaceful use of nuclear energy, tritium has been releasing to the environment as airborne and liquid effluents from nuclear power plants and nuclear fuel reprocessing plants. The release from the nuclear power plants depends on the reactor type. Other sources are the tritium production facility of military purpose and the consumer products that use tritium as luminescent energy and disposed to landfill site. Internal dose is only concerned on tritium due to low decay energy, suggesting tritium concentrations in drinking water and food are critical for dose evaluation.