What poisons are in marijuana?

There are no poisons in marijuana. Poison can be added to marijuana, but that is a very rare, almost unheard of, occurrence.

For decades, there have been rumors that marijuana is often laced with dangerous drugs, like PCP. But there is no truth to these rumors. These rumors don't even make sense. No drug dealer on earth would give drugs away for free, by adding them to marijuana and selling it for the same price as regular marijuana. Drug dealers do not give drugs away for free, EVER.

It is certainly possible that there have been instances of marijuana being laced with poison or PCP. But it is certainly not a common occurrence.