> Your exhalations are only pollution when they destabilize healthy levels. So that’s a bit of a straw man concern.

So CO2 is not a pollutant because it is a product of breathing.

Regarding,

> Dumb argument. Is water a pollutant because of the drowning risk?

It might be counter intuitive - because water is not a risk in most contexts. But on another planet where water is an unusual corrosive, then of course it could be a pollutant.

And even on Earth, if some production system kept pumping our environment full of water as a side effect of some process, to the point of endangering or killing ecosystems, in that context it would be a pollutant.

A pollutant is when the accumulation of some left over of a process significantly alters and harms its environment.

Pollutant is a statement about some material’s impact in its context. It isn’t something inate, without context.