This element is locked in tiny zircons within the granite. While it stays within the zircon for a period of time, being a very small atom, helium escapes the zircon within a few thousand years.
Animals and people eat plants and take in carbon-14 as well.
When granite rock hardens, it freezes radioactive elements in place.
The most common radioactive element in granite is Uranium-238.
Cosmic rays enter the earth's atmosphere in large numbers every day.
For example, every person is hit by about half a million cosmic rays every hour.