I got going looking into this subject on the Internet this morning. Here are a few things that I can definitely establish.
First of all its a pretty large controversy. What I mean by that is that quite a lot of people have strong opinions to express about it, on both sides. There are quite elaborate descriptions, dedicated websites and videos on the pro side, mostly suggesting aluminates and barium salts are being deliberately spread into the atmosphere by the US military, possibly for weather control, possibly for radar shielding, or possibly for population control, with attempts at proof. On the denial side there is also a very lot of material, most of it consists of a priori denial and subsequent attempted debunking.Second of all, it can be pretty well established that aluminum is natural to be found in the body though it serves little purpose, but bodies can uptake enough aluminum to be poisonous and destructive. It is commonly added to municipal water systems during the process of antisepsis. Further aluminum compounds can be uptaken via acidic foods in contact with aluminum cookware. It is also commonly found in medicines and over-the-counter preparations such as antiperspirants. Aluminum poisoning can affect organs, muscles, and especially bones and the brain.
Third, I'm not set up to remove it from my environment. The best way would be to drink and cook only with distilled water, but the only device I have that I could use for distilling is, well, my cast aluminum pressure canner. Oops. Distilling water is quite energy-intensive, that's why its so rare for water systems to employ sea water.
Fourth, I have flown extensively in commercial jetliners over a period of decades, and I always take the window seat because I love to look out and see the different point of view, I love the shapes of clouds from across or above, I also love the aerial views of territories resembling maps, a long-time love of mine. From my own observations I can definitely state that commercial flights are going higher and higher than they used to, that commercial flights never release contrails (its now common to see other commercial planes from cruising altitudes these days), and that wide contrails or "chemtrails" at altitudes slightly above cruising altitudes are something I've only been starting to notice for the last few years.
Finally, I have to unleash stinging criticism for the folks on both sides of this debate. Everything I read and saw appeared to have been produced by people who already had their own minds made up and were attempting to influence other people. Thus there is no science going on at all. Just as a reminder, the first step in the scientific process is observation. Before you make your mind up, go out and do some tests. If there is a definite, recent uptick in chemical spraying then it perforce must be showing up in our rainwater. How about some extensive testing of aluminum and barium concentrations in rainwater over affected areas and then a comparison with rainwater in places where the supposed chemtrails are not happening, such as Addis Ababa or Reykyavik? Lets all find out for sure what's going on before we try to influence others, eh?