Have a read of the information found at this link primax
http://www.wrh.noaa.gov/fgz/science/contrail.php?wfo=fgz It should help clear up some things for you. Whilst I disagree with this conspiracy theory choosing instead to believe in the laws of physics it is openly documented that the British government did experiment with chemical spraying of the population to the east of England between 1953 and 1964
http://www.bbc.co.uk/insideout/east/series10/week9_spraying_war_extra.shtml