Essay:CO2 levels - a human perspective

I wasn't really sure what to use as the title for this essay; I mean human perspective as in using the concentration of substances in a human body in order to put CO2 concentrations in the atmosphere into perspective. Feel free to suggest a better title, or to point out any errors (knowing me there'll probably be quite a few...) or substances I've missed.

Why I'm writing this
A common argument used by opponents of athropogenic climate change is that with a concentration of "just" 400 parts per million (ppm), CO2 couldn't possibly have an effect great enough to cause any major damage to the Earth/it's inhabitants. To highlight how absurd this argument is I'm going to compose a list of substances which at that very same concentration in the human body (i.e. 400 milligrams per kilogram body mass) would most likely kill you.


 * Botox.
 * Caffeine.
 * Aspirin.
 * Nicotine.
 * Plutonium-210.
 * LSD.