evidence: The conspiracy theory that the U.S. government is intentionally spraying toxic chemicals into the air has persisted for nearly two decades. The baseless claims often refer to so-called "chemtrails" and say that the condensation trails behind airplanes are part of an atmospheric spraying program meant to depopulate the world. A new, related claim says the government has admitted to the spraying, citing a video of former CIA Director John Brennan.