It's nothing to be scared about but it is concerning to some of us, more than anything it's the lack of transparency that's concerning.
Rebuildables really aren't that difficult but I believe someone mentioned that one or more of the Kanger tanks is glass and ss.
I agree. I'm more upset about the lying than I'm about actual materials used in Aspire line. That fiberglass/ceramic in their coils worries me more than the brass chimney, actually.
I never worried about plastics myself--even Kayfuns come with plastic tanks. Eliquids don't get hot in the tank--if they do, you're doing it wrong.

And most of our ejuices come in plastic bottles, anyway. We drink water, juice and milk from plastic bottles...
Aerotanks are ss and glass--I use them and I like them. The ProTanks are chromed something or other--they are not ss, but they also don't have internal threads inside the chimney, like Nautilus, so the chrome stays there pretty much undisturbed and unscratched.
No need to be scared--just be informed and choose your vaping hardware wisely. There's always risk--I choose to avoid unnecessary, avoidable risk, as a general rule.