Thoron radiation

From Memory Alpha, the free Star Trek reference

Thoron radiation is a type of radiation with many uses. It has been used primarily as a method of interfering with sensors and transporter systems (DS9: "Emissary", "The Way of the Warrior"; VOY: "Basics, Part II", "The Cloud"), seen as a byproduct of alien appearances (DS9: "If Wishes Were Horses"; VOY: "Sacred Ground"), used for medical purposes (VOY: "Basics, Part II", "Flashback"), and used as a basis for weaponry (although it can result in instability in the weapon) (VOY: "Retrospect", "Warlord").

High levels of thoron radiation are found around the Nechisti shrine. (VOY: "Sacred Ground")

Antithorons can be generated on a large scale by Intrepid-class starships and have been used both to interfere with force fields and decontaminate planetary crusts prior to mining. (VOY: "Hunters", "Tattoo") Thoron radiation may also hinder transporter operations, presumably by interfering with sensor readings.

To 21st century science, thoron is a naturally-occurring radioactive isotope created by the decay of thorium. It is also known as radon-220, has a very short half-life of about one minute, exists as a gas at room temperature, and produces alpha radiation. It presents a radiation health hazard in nature much like radon, but is sometimes used in radiotherapy. To 24th century science, thoron radiation appears to be something wholly distinct from simple alpha radiation.