Radiation

Radiation was energy produced by materials and by physical interactions, such as the contact of matter with anti-matter.

Biological effects
The radiation resulting from the explosion of a Jagaroth ship in the distant past of Earth triggered the beginning of life from a nearby pool of primordial soup. (TV: City of Death)

Radiation was often harmful or fatal to most life and could cause mutations. In many life forms, including Gallifreyans, it induced radiation sickness. (TV: "The Survivors", Destiny of the Daleks)

Nonetheless, Time Lords could absorb, withstand and expel great doses of certain types of radiation; the Tenth Doctor said he used to play with roentgen bricks in the nursery. (TV: Smith and Jones) Although this is not the case for humans, as they can be rendered sterile if a lead apron is not given to them.

Other species could absorb and regenerate with it, such as the Kastrians (TV: The Hand of Fear) and the Daleks on Skaro, whose evolution led to them becoming dependent on a constant supply of radiation. (TV: The Daleks) Following the Daleks' defeat in the Thal-Dalek battle, the incubation level of the Dalek City was automatically sealed off with the Dalek Supreme and the gestating embryos being placed in suspended animation. As a result of the decades that they spent in the radiation-free environment, the Daleks overcame their dependence on it. (AUDIO: Return to Skaro) Nevertheless, radiation could still prove harmful to the Daleks. When "Rusty" was damaged, a crack in his power supply began leaking trionic radiation that began killing him and affected his mind, turning him into a "good Dalek." When the Twelfth Doctor stopped the radiation leak, Rusty immediately returned to normal. (TV: Into the Dalek) When on the planet Omnia, the Daleks were forced to contend with vitanium radiation, forcing them to act either through emissaries or with specially shielded casings. The Sixth Doctor noted however that vitanium radiation was harmless to nearly all other forms of organic life. (AUDIO: Emissary of the Daleks)

Some organisms could withstand large amounts of radiation, such as the Foamasi. (TV: The Leisure Hive)

An Exxilon fuel pod was left in ancient Earth Incan civilisation, causing mutations in the populace and leading to Huitzilin gaining great powers. (PROSE: The Left-Handed Hummingbird)

The Solonians used thaesium radiation to cause the "mutations" that were part of their life cycle. (TV: The Mutants)

The Cybermen showed a weakness to radiation, which Ben Jackson and the team at the base Snowcap used to their advantage when the Cybermen invaded Earth in 1986. The radiation in the chamber of the Z-Bomb instantly affected them so they could not ensure the bomb was dismantled before their home planet Mondas was destroyed. (TV: The Tenth Planet)

On Wengrol, radiation from the star Mortain caused mutations in the genetically modified Yend. (PROSE: The Sons of the Crab)

The effects of radiation could be combated by ingesting certain types of medicine such as an anti-radiation pill, (TV: Destiny of the Daleks, PROSE: Plague of the Cybermen) or the Thals' anti-radiation drug. (TV: The Daleks)

Radiation could be used as a therapy against other kind of illness, such as the infective Lazar's disease. (TV: Terminus)

After Eldrad was executed in an obliteration module, the Kastrian's hand ended up on Earth where it was discovered one hundred and fifty million years later by Sarah Jane Smith. Under Eldrad's influence, she took it to Nunton Experimental Complex where, by absorbing radiation, the Kastrian restored itself. (TV: The Hand of Fear)

In one possible future where Earth became Orphan 55, radiation was at least partially responsible for mutating the survivors of humanity into the Dregs. (TV: Orphan 55)

Sociological effects
The Thousand Year War between the Thals and the Kaleds initially saw nuclear weapons used. The fallout from this caused disfigurement on both sides, with those affected being cast out to preserve racial purity. (TV: Genesis of the Daleks)

The war between the Argolins and the Foamasi saw the former become sterile. This dictated the field of scientific study the Argolins attempted to save their species. The Tachyon Recreation Generator was a product of their research. (TV: The Leisure Hive)

Radioactive locations
On the planet Janus Prime, radiation made the sand glow blue. It also destroyed a human body's lipids, making skin sticky to the touch and changing to a jelly-like texture. Upon death, the body lost cohesion and collapsed into a porridge-like substance. (PROSE: The Janus Conjunction)

On Dulkis, the Dulcians irradiated an island to see the effects. When the Dominators landed there, they absorbed the radiation from the island into a storage tank, allowing them free access to the area. (TV: The Dominators)

Skaro's atmosphere was polluted because of the fallout consequent the neutronic war, enough to affect the First Doctor and Susan Foreman. (TV: The Daleks) Romana II and the Fourth Doctor suffered from radiation on Skaro. Romana, to escape the Daleks, faked dying from radiation. (TV: Destiny of the Daleks)

Argolis had a radioactive atmosphere from a nuclear war with the Foamasi. (TV: The Leisure Hive)

The Forbidden Zone was a section of Terminus that only the Garm would regularly enter. It was created by a radiation leak. (TV: Terminus)

Messaline had a relatively high level of radiation; this was eradicated by terraforming. (TV: The Doctor's Daughter)

Oseidon had the highest radiation level in the galaxy of Mutter's Spiral. (TV: The Android Invasion)

The petrified jungle of Skaro had a high radiation level from a past nuclear war between the Thals and the ancestors of the Daleks. (TV: The Daleks)

The Third Doctor regenerated due to radiation exposure on Metebelis III. (TV: Planet of the Spiders)

The Sixth Doctor noticed a suspicious presence of radiation near the planet Lakertya and avoided it. However, his future self sent a psychic signal to him to go there despite the unknown danger, setting in motion a plan to stop the Valeyard and free himself from the influence of the Nathemus through his own demise. He regenerated due to the radiation exposure, which was actually being released from several beams fired on the TARDIS by - a kind not lethal to humans, only causing his then-companion Melanie Bush to pass out, but indeed lethal to Time Lords, resulting in his death. (AUDIO: The Brink of Death, TV: Time and the Rani)

Owen Harper died after he was exposed to a radiation fallout at a nuclear power plant in Cardiff. He was able to stop the fallout from reaching the rest of Cardiff with help from Toshiko Sato who shortly died after from her own injuries. (TV: Exit Wounds)

The Tenth Doctor regenerated due to radiation exposure caused by taking Wilfred Mott's place in a radiation containment chamber. (TV: The End of Time)

Because of an ongoing nuclear war, Atrios was contaminated by radiation. Some areas, such as K-Block, were more affected than others. Its inhabitants moved around with wrist Geiger counters. (TV: The Armageddon Factor)

The ruins of Klimtenburg's church became irradiated after a Cyber-ship crashed into it and the housing of the reactor shattered. The reactor shut down so it was not too severe but the villagers, being from the 19th century, were unaware of the danger and collected pieces of the reactor which they made into jewellery. (PROSE: Plague of the Cybermen)

In one possible timeline, the Earth, known as Orphan 55, was radioactive due to the climate changes and nuclear war that had devastated the planet. Kane stated that the radiation levels had dropped enough by the time that the Thirteenth Doctor and Team TARDIS visited that it was safe to go outside on the planet's surface for short periods of time. (TV: Orphan 55) In a parallel world, the southern half of England was left heavily irradiated after a replica of the RMS Titanic had crashed into Buckingham Palace. (TV: Turn Left)

In the Federation universe, the planet Aprilia III had a unique radiation belt that rendered transporters non-functional. (COMIC: Assimilation²)

Behind the scenes

 * James Johnson's "headcanon" for his Time War-era Reconnaissance Dalek, which was featured on the cover of Gallifrey: War Room 1: Allegiance, established that its Focusing Emitter reduced the radiation signature of its death ray.