Delta Radiation

Delta Radiation is a type of radiation. Delta radiation can be very deadly and cause profound neurological damage; it is one of the only things that can kill the "eel creatures" in Xindi-Reptilian rifles. (ENT: "The Shipment") It can also be released when a J-class ship's baffle plate ruptures; Fleet Captain Christopher Pike's terrible injury occurred in such an incident aboard a training vessel. The exposure left him crippled and confined to a wheelchair in the mid-2260s. (TOS: "The Menagerie, Part I")

Exposure to delta rays can also weaken metals such as Viterium. (DS9: "Valiant")

The warp engines of the ships of the Terran Empire's Imperial Starfleet in the Mirror Universe generate excessive delta radiation, which shorten the lives of engineers working with them by an estimated ten years per one year of exposure. As a chief engineer, Charles Tucker had the misfortune of being exposed to large amounts of delta radiation, leaving him scarred and disfigured for life. Tucker himself sardonically noted that the radiation exposure would ensure that his "grandkids glow in the dark." (ENT: "In a Mirror, Darkly")

In 2369, Doctor Julian Bashir exposed a sample of the aphasia virus, grown on triagar solution, to a delta ray field at 120 millivolts. (DS9: "Babel")

In reality, delta radiation is a particle radiation comprised of secondary electrons emitted when ionizing radiation passes through matter.