Terrestial helium isn't produced by nuclear fusion. It's produced by nuclear decay. As you may know, you get alpha, beta and gamma radiation from decay. Gamma rays are just energetic photos. You typically need thick lead and/or concrete to shield you from them. Beta radiation is high energy electrons. A thin sheet of steel will shield you from those.

And lastly we have alpha radiation, which is just a Helium nucleus. A sheet of paper will generally block alpha radiation.

Some materials are really strong alpha emitters. A good example is Polonium-210 where almost all of its energy from decay is in the form of alpha radiation. This is why Po-210 is so lethal when ingested, which has been used for that purpose [1].

But this means if you produce a lump of Polonium-210, it's basically radiating Helium. The source of almost all of the Earth's Helium is from uranium and thorium decay.

[1]: https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvine...