Someone suggested this to me as a possibility. Imagine a swarm of bugs with nothing more than a small amount of poison as a payload and an injector of kinds. Kind of scary to think about.
Think about https://en.wikipedia.org/wiki/Assassination_attempts_on_Fide...
Or about https://en.wikipedia.org/wiki/Poisoning_of_Sergei_and_Yulia_...
It is double scary because they can easily be made untraceable. Like in that short story by Philip Dick that I forgot the title again.
Imagine one depositing a contact poison briefly before the target makes contact with an object.
I guess we'll all need >= 8 K surveillance footage, to try to analyze the vector.