Chemtrails again, what is the real truth about this ?

I don't really know whether these planes are all military or civilian or a mixture of both, the only fact I can go on is that the sky seems always white, never blue any more and the trails left by planes last a lot longer than they did in the eighties, that I've seen the trails start and stop as if turned on and off by a switch, that I have had worsening breathing problems, and worse of all, I have noticed a lot more people I know have died prematurely with cancer over the last ten years in line with the appearance of these chemtrails.

Have you noticed any of these things ?