When you buy a natural diamond, you're also buying a risk of cancer and various diseases, because all natural diamonds contain trace amounts of thorium and uranium. This is due to the fact that diamond crystallization occurs deep within the Earth's mantle, where these radioactive elements are naturally present

Trace amounts of thorium and uranium are literally everywhere on the land surface of the planet.

This is moot sans the "source that you quoted" and some stats and studies.

For interest, Australia: https://www.ga.gov.au/bigobj/GA13928.pdf

India, Mali, Fiji, Africa, Americas, etc have similar trace amounts across their surfaces that are detectable from an aircraft 80m above ground level traveling at 70 m/second.

"Radiation: it's everywhere"