breathable air becoming a diminishing resource, page-4

Hardly seems so surprising to me - as CO2 increases (not in dispute) and as land and natural vegetation is cleared (also not in dispute) and fossil fuels are burnt (not in dispute - they are factories for taking C and O2 and making CO2) then it makes sense that the O2 concentration will decrease. Oxygen is one of the most abundant elements on the planet, although much of this is in the earth's crust in molecular form. This decrease is probably not significant over time. I would humbly suggest that www.helium.com with its "cartoonify yourself" ads is probably not a credible source of scientific information or comment, but if you do want to find a hare-brained theory then the internet is definitely the place to be!