Those of you enamored of mystery novels and/or crime shows may have heard the little phrase, "The poison is the dose." All too true - and now you'll have an actual scientist's perspective on it. And you'll also have a very useful question to ask:
What’s it do?
That’s the first thing I think when I hear someone say something is a toxin. There is no single “toxic” reaction out there. Every toxicologically active chemical entity out there has its own mechanism, its own target. Some are more recoverable than others, some have pretty dire consequences; some we have antidotes for, some not. Some exert an effect quickly, while others can take their time. They can target any physiological system, or multiples. Cause death, permanent injury, reversible injury, minimal harm, or anywhere in the middle. Locally, regionally, systemically. There are many, many examples of different actions that a given compound could do. The severity of the effects is important to evaluate.
Lob that one at the next idiot who starts going on about toxins. There are other questions answered there that are equally grenade-like and shall prove quite useful when people babble about all of those awful toxins making all of us sick although they're only found in vanishingly small quantities, if at all, in our vaccines.
And then remind them of that old crime show/mystery novel truism: the poison is the dose. Not just any old dose will do.