[geofft]

So can alcohol, but countless offices have beer fridges.

And, relevantly for an article on microdosing, so can anything at high doses, including water (e.g., Jennifer Strange) and oxygen (e.g., Apollo 1).

[lmm]

It wasn't the oxygen that killed the Apollo 1 astronauts, it was the fire. Oxygen can be toxic at high pressures (which is why deep divers use a mix with helium replacing some of the oxygen) but AIUI breathing 100% oxygen at ordinary atmospheric pressure is fine.