A fun fact for the climate deniers:

If you think that a CO2 concentration of 400 parts per million can not possibly have a tangible effect, think again.

The same concentration of botulinum toxin in your body would kill you 200.000 times over. When injected, the lethal dose is 2 parts per billion (with a B) of your own body weight.

About 2000 parts per million is the lethal dose for fentanyl, for comparison.