The word “chemtrails” was not invented by a conspiracy theorist, it was invented by the US Air Force. A microfiche has been found in the Oklahoma Library system of an Air Force manual dating back to 1990, which uses the word “Chemtrails” in its title and describes the various experiments pilots will be conducting with the aerosol release of various noxious substances, some relating to cloud-seeding and weather modification such as silver iodide and others, in conjuction with the HAARP project, such as barium-fluoride.
Here is a link to the manual: http://chemtrailsplanet.files.wordpress.com/2013/03/chemtrails-chemistry-manual-usaf-academy-1999.pdf
The spraying of toxic barium salts in the atmosphere relates to scalar weapons systems (HAARP), which behave like targeted gravitational fields and act as anti-ballistic shields.
The list of substances listed in this manual to be used in these USAF experiments include: aluminum 3, aluminum hydride, barium-fluoride, beryllium, cyanide, hydrochloric acid, various ions, including ions of copper, iron 2, lithium ions, nickel perchlorate (rocket fuel), phosphorous tri-fluoride, silver iodide, sodium ions and single-valence metals.