I provided the Wikepedia definition to help clarify what pollution is - I had read the entire thread btw.
Although global increases in CO2 are far short of toxic levels its very invisibililty etc. means that it can present problems in localised pockets - as with an excess of almost anything I suppose.
That's why we advise parents to take care with kids & plastic bags. So too with too many people in a small & poorly ventilated enclosure. Put millions of people into a small atmospheric bubble [eg 25m in Mexico City] & you even need massive fan systems to ventilate the place or people just start dying!
