The linked article first discusses the history of the claims then ends with this:

"The lab discovered 'Pseudomona flourescens', 'Enterobacter cloacae', and 'Serratia marcescens', one of the 'simulants' the 'London Telegraph' reported the British 'Ministry of Defence' sprayed from a ship over Dorset's population during the 1970s. Bio-warfare proponents are bolstered by Dr. Leonard Cole (Rutgers University), who testified before the US Senate about army vulnerability testing staged between 1949-1969 (and still today at Salt Lake City's 'Dugway Proving Ground').

"Agents released 'simulants' later found to be toxic from cars' exhaust pipes, wind-powered suitcases, boats, and even light-bulbs thrown New York City subway cars' tracks to test domestic vulnerability to bio-chemical warfare attacks. With proven records of populace testing behind 'Clouds of Secrecy', what's to cast doubt on contemporary high altitude spraying claims?

"Lack of evidence for one. No chemtrail conspiracy proponent has released documented lab tests of the trails' composition. Thomas still hasn't published his 'EPA' lab test results anywhere. A 'New Mexico' newspaper interviewer quoted him saying he would do so if offered grants large enough to launch proper investigations. More questionable still is his chemtrail remedy pills business. Cole isn't aware of any modern jet plane testing and considers it unlikely the military would test at such heights: results would be difficult to track over such wide areas. The aviation science underlying claims is also problematic, according to marine turbine engineer Jay Reynolds, the most notable chemtrail debunker: "If you pass almost any chemical through a gas turbine engine, the combustion temperature is like 2000 degrees. Nothing survives: it's an incinerator."

"Thomas has alluded to Air Force weather modification projects and the infamous 'HAARP'. But NASA's 'Atmospheric Effects of Aviation Project' (AEAP) determined heavy contrail activity over a New England commercial flight path is responsible for 2% more cloudiness than normal.

"The chemtrail community mirrors the UFOlogy underworld before 'The X-Files': explanatory reports are shared on message boards and poorly designed web-sites; believers continually cross-cite their work whilst including scant outside research. Debunkers are dismissed as government agents. Before missiles are aimed at unmarked jets, let's hope lab results are handy!"

A Dispassionate Look