I must attempt to shade the light of truth on some gray areas which have been taken as a matter of fact!

 One such that has been passed around is the idea that the vapor trail left by high altitude {over 20,000 Ft} Jet aircraft is some sinister type of chemical dispersion...                             Well as an engineer and pilot it is not the actual fact... 

Let's look at how a jet engine works: It starts with a set of high speed fan blades [the turbines assembly] which is set to spin or turn inside a tube [ the engine housing] which for all practical purposes is an air pump or blower...  Once the turbine is up to about 70% fuel is ejected into the assembly then ignites causing a fast burn due to the spool air flow, therefore producing thrust as the expanded hot gas exits the tail of the jet engine assembly... 

 Air temperature  @ high altitudes is around a minus fifty (-50 ) degrees F @ 30,000 ft  thus the hot gas leaving the jet engine leaves a vapor trail which many times can be seen from the ground on a clear day...  This is the so called Chem Trail you may see from a high altitude jet aircraft...   Since the fuel is organic it leaves a variety of elements in the discharge, much is water vapor...  

 The idea that there is some grand plan to dope or spray everyone on earth is more of a fantasy than a fact...

 First there is not enough chemicals in the world to do so ( the big chemical companies would like to be able to do so, but NADA!) Why would someone want to dope everyone including them selves? 

 Second we do not have any where enough planes to do such a task...  

 Third do you have any idea what an exuberant amount this would cost, plus the amount of manpower it would take for such an activity...  All the combined air forces and airlines in the world could not even approach this magnitude of effort...  Again to what purpose...

 Finally if you want to take time to study the wind patterns around the earth, you will see there is a large demarcation of such!  First the general air is divided into the northern and southern hemispheres and the air systems tend to stay over each half of the globe... Then there are several bands of air circulation from the Equator toward each poles; where the air moves in a certain pattern... Plus you have heard of the jet stream which operates, High Up in each hemispheric ocean of air and moves continually...   So therefore if someone were attempting to dope or poison certain people they would have a great deal of trouble targeting the right ones...

 BTW: Some years ago;  I was on the ground in Florida where there was a heavy fly over chem spray program for the Mediterranean Fruit fly...  This involved low level appox. 2500 ft spraying using slow prop airplanes...    I think I even survived!

 At least that is the way I see It!