Yahoo! News – Bush Under Fire for CO2 Climate Threat Downgrade – At issue is whether CO2 is a “pollutant”. I don’t know the legal definition of “pollutant” as it relates to the United States’ Clean Air Act, but Merriam-Webster says a pollutant is “something that pollutes”. OK, that’s common sense. And it defines pollute as “to make physically impure or unclean”. So, if you consider CO2 to be “unclean”, then it is indeed a pollutant.
But CO2 is odorless, invisible, naturally occurring, and critically important for the health of trees, plants, and every food crop grown on planet Earth. That sure doesn’t sound like “unclean” to me. So from the standpoint of the English language, I have to agree with the Bush administration on this one – I don’t believe CO2 is a “pollutant”. If you required photosynthesis for life (and we all indirectly do) I think you’d agree. That said, there is the concept of “too much of a good thing”. And regardless of whether CO2 is a pollutant by my definition, it is true that it can kill you.