Radiation

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

Biological effects
Radiation is often harmful or fatal to most life and can cause mutations. Some organisms can withstand large amounts of radiation, such as the Foamasi (DW: The Leisure Hive). Also, Time Lords had the ability to absorb, withstand, and expel large amounts of certain types of radiation: as stated by the Tenth Doctor, he used to play with Röntgen bricks in the nursery. (DW: Smith and Jones) Others could actually absorb and regenerate with it, such as the Kastrians (DW: The Hand of Fear) or beings such as the Daleks on Skaro, whose evolution led (at various points) to them becoming dependent on a constant supply of radiation. (DW: The Daleks)

Similarly, an Exxilon fuel pod was left in ancient Earth Incan civilization causing mutations in the populace and leading to Huitzilin gaining massive 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)

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 as a result of a nuclear war with the Foamasi. (DW: The Leisure Hive)
 * On the planet Janus Prime, the radiation on the planet made its sand glow blue. It also destroyed a (human) body's lipids, making skin sticky to the touch until it turned into 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 its effects. When the Dominators landed there, they absorbed the radiation from the island into a storage tank, allowing them free-roam of the area. (DW: The Dominators)
 * Romana and The Doctor suffered from radiation on Skaro, and Romana, to escape the Daleks' clasp, faked dying due to radiation. (DW: Destiny of the Daleks)
 * Messaline had a relatively high level of radiation; this was however eradicated via terraforming methods. (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 as a result of 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, taking the place of Wilfred Mott. (DW: The End of Time)