 In "Smith and Jones" the Tenth Doctor says that the radiation given off by X-rays pose no real threat to Time Lords, and proceeds to absorb an amount that would be lethal to a human, which he subsequently expels through his foot.<ref name="Smith and Jones"></ref> "The End of Time" shows the Tenth Doctor as being capable of surviving (for a short period) a massive burst of radiation that would have killed anything else instantly.However, the radiation burst caused enough damage to start a regeneration.Time Lords are extremely long-lived, routinely counting their ages in terms of centuries; the Second Doctor claimed in "The War Games" that Time Lords could live "practically forever, barring accidents."