I added that because the first two responses seemed to be confused.
Anyway, uncommon household uses can also be a safety concern. People still do occasionally get poisoned by mixing ammonia and bleach even despite the repeated warnings.
Talking about the constituent parts is similarly relevant when you’re heating something to significant temperatures. Many reasonably safe substances really shouldn’t be tossed on a bond fire etc. For other things it’s not the substance itself that’s a concern but impurities from the manufacturing process. People often think of past recalls as companies doing something dumb, but I think we underestimate how difficult it is to get this stuff right.
And table salt is made out of Sodium and Chlorine, one of which is explosive when mixed with water, and the other is used to gas soldiers in trenches if you're into committing war crimes.
What matters is what effect the particular chemical has when you put it through common household uses, not the effect of its constituent parts.