[gonvaled]

My point is that anything is poison, depending on dosage. Even water, the basis of terrestian life, although I know I am stretching the analogy there.

But yes, water will destroy your cellular membranes if exposed to it in big quantities for a long time. Those are chemical (biological) effects.

[qubex]

(I'm just picking your brain because now I'm curious.)

How about a noble gas? Presumably those are chemically inert enough to not cause anything chemical/biological at all?

[gonvaled]

Nature does not care about our definitions, and properties are usually on a gray scale, not black-white. Inert gas have very low reactivity [1], but they can still react:

> Nonetheless, low reactivity—instead of no reactivity, as had formerly been thought—characterizes the rare gases. One of the factors governing the reactivity of an element is its electron configuration, and the electrons of the noble gases are arranged in such a way as to discourage bonding with other elements.

That said, I would probably classify noble gases as perfectly safe, since damage from exposure to them will more likely come from mechanical interactions, and not biological / chemical.

[1] http://www.encyclopedia.com/science-and-technology/chemistry...