Contrails are not worth investigating when the investigation will turn up Zero. Other subjects have other circumstances. My rejection of the jab was founded on the fact that I caught them lying early in the game about the safety of hydroxychloroquine---and paying attention to those who were obtaining cures using it. Leaded gasoline was outlawed, but I cannot recall any clear evidence of public harm from it. It results in hardship with the need for high-octane fuel in airplane piston engines. (Now we just get to breathe organic poisons instead of metallic ones. Methyl-tert-butane, anyone?) DDT was unfairly condemned by a publicity campaign based on fudged information, and its banning led to the deaths of millions of children in the Third World. I don't know about monosodium glutamate, but do not recall any controversy in particular. And, of course, everyone is terrified of radioactivity and we've had nuclear power stupidly curtailed for half a century.

I am not opposed to caution, but there have been too many cases of things being banned or shunned or imposed based on propaganda campaigns by those with an axe to grind. The whole "green" movement is a case in point, where industry itself is throttled for the sake of a magical fear, unsupported by "the science."

But let them study to their hearts' content. Just be prepared for the conclusion to be "nothing here," and live with it. Here's a pretty decent debunking website that provides a lot of education: https://skepticproject.com/articles/chemtrails/.