Where helium comes from

Global helium supplies are under threat - if demand continues to increase at the projected rate, world helium reserves could run out within 62 years. Atmospheric helium provides an interesting context for highlighting the impact of fission and fusion processes on our environment. Around 7% of the helium-4 (the most common isotope of helium) in the Earth’s atmosphere is thought to have been produced from nuclear fusion in the Big Bang; the remainder is formed from the radioactive decay of uranium into thorium within the Earth. Around 190 grams of helium-4 are outgassed from the Earth’s surface every second.