I asked a question regarding the phenomenon of "contact high", which is sometimes dismissed as psychological, and sometimes accepted as real, here: Can you get high from second-hand marijuana smoke?
I found that second-hand marijuana exposure is known to affect drug-tests, and this is why a threshhold is set at 50ng per unit blood (whatever it was) for someone to have been considered actively smoking marijuana. I was asking to see if there are established psychoactive effects at concentrations of 4 ng, 1 ng, or even .1 ng. I am curious about the literature, I couldn't find the answer by googling.
I think this is obviously notable, and I think sklivvz just doesn't like me. Could someone reopen the question. If the question is badly phrased, I'm sorry. I feel kind of foggy today, as this question was inspired by unfortunate recent events.