Good graph, this shows the "harm" of certain substances, and yet Heroin is not toxic at all. The Harm comes from the addiction, the way it is used and the crimes committed to feed the need. A Heroin overdose does not poison you, it just relaxes you to the point where you stop breathing.
If you...
I remember seeing a statistic years ago that had attributed 6 deaths to Cannabis in the U.S. over a five year period, included in the stats though though were people who had fallen asleep and burnt their house down, etc. But my favourite one of the 6 deaths by Cannabis, was that of a customs...