Radiation

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

Biological effects
Radiation was often harmful or fatal to most life and could cause mutations. Some organisms could withstand large amounts of radiation, such as the Foamasi. (DW: The Leisure Hive) Time Lords could absorb, withstand and expel great doses of certain types of radiation; the Tenth Doctor said he used to play with Röentgen bricks in the nursery. (DW: Smith and Jones) Others could absorb and regenerate with it, such as the Kastrians (DW: The Hand of Fear) and the Daleks on Skaro, whose evolution led to them becoming dependent on a constant supply of radiation. (DW: The Daleks)

An Exxilon fuel pod was left in ancient Earth Incan civilisation, causing mutations in the populace and leading to Huitzilin gaining great powers. (NA: The Left-Handed Hummingbird) The Solonians used thaesium radiation to cause the "mutations" that were part of their life cycle. (DW: The Mutants)

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

The effects of radiation could be combated by ingesting an anti-radiation pill. (DW: Destiny of the Daleks)

Radioactive locations

 * Argolis had a radioactive atmosphere from a nuclear war with the Foamasi. (DW: The Leisure Hive)
 * 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. (EDA: 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. (DW: The Dominators)
 * Romana and the Fourth Doctor suffered from radiation on Skaro. Romana, to escape the Daleks, faked dying from radiation. (DW: Destiny of the Daleks)
 * Messaline had a relatively high level of radiation; this was eradicated by terraforming. (DW: The Doctor's Daughter)
 * Oseidon had the highest radiation level in the galaxy of Mutter's Spiral. (DW: The Android Invasion)
 * The Petrified Forest of Skaro had a high radiation level from a past nuclear war between the Thals and the ancestors of the Daleks. (DW: The Daleks)
 * The Third Doctor regenerated due to radiation exposure on Metebelis III. (DW: Planet of the Spiders)
 * The Tenth Doctor regenerated due to radiation exposure caused by taking Wilfred Mott's place in a radiation containment chamber. (DW: The End of Time)