Comment by ansible

Uh, I don't know about that...

https://en.wikipedia.org/wiki/Serenity_(2005_film)

On a more serious note, anything that's going to affect behavior is going to have a dosage range. Too little absorbed, and there won't be enough effect. Too much, and that will harm / kill people in interesting ways.

With chemical weapons, you only worry about the bio-accumulating enough to kill your enemies. An enemy receiving more than a lethal dose isn't a problem.