According to countless chemtrail research theories , trails left in the sky by high-flying govt. aircraft are dangerous chemical or biological agents deliberately sprayed for reasons undisclosed to the general public.

There are however, numerous researchers claiming that a global covert program is underway, made possible through political, commercial, and government interests working in collusion to release extremely toxic material into the atmosphere ostensibly to "combat global warming."

How valid are these vague claims regarding chemtrails being a dangerous govt. agenda?