Comment Re:Doesn't matter (Score 3, Informative) 341
It's not even a matter of whether a particular substance is a "pollutant" or "toxic". Many necessary substances can be harmful if present in high concentrations. You can die just by drinking too much water. That doesn't mean that water's a pollutant, even though too much can kill you. The argument that carbon dioxide is not a pollutant because plants need it is similarly confused -- too much of a good thing can be harmful.
To get to the heart of the matter, the EPA considers any harmful emission to be a pollutant, even if the substance emitted is necessary for life.