New Study Compares Marijuana Toxicity With Other Stuff

A new study on marijuana toxicity is out.  Christopher Ingraham at the Washington Post notes that the study suggests that " marijuana may be even safer than previously thought."  He writes:

    Researchers sought to quantify the risk of death associated with the use of a variety of commonly used substances. They found that at the level of individual use, alcohol was the deadliest substance, followed by heroin and cocaine.

    And all the way at the bottom of the list? Weed — roughly 114 times less deadly than booze, according to the authors, who ran calculations that compared lethal doses of a given substance with the amount that a typical person uses. Marijuana is also the only drug studied that posed a low mortality risk to its users.

The study is Comparative risk assessment of alcohol, tobacco, cannabis and other illicit drugs using the margin of exposure approach, by Dirk Lachenmeier (Dresden University of Technology) and Jürgen Rehm (University of Toronto).

Studies showing the relative harms of alcohol and marijuana are always nice.  But I'm not sure this one does much that's useful.  It's not my field of expertise, but it's not a new clinical study.  Rather, it's taking a bunch of data we already have and applying a different measuring stick (the "margin of exposure" standard) to it.  MOE is (as I understand it) the ratio between the usual dose and the harmful dose of a substance.  It was developed as a method for determining how much of a particular contaminant in a food creates a risk that justifies regulation.  I'm not sure how that has much to tell us about how any individual substance ought to be regulated.  Actual toxicity to the subject isn't the controlling factor in legalization -- if it were, rat poison would be banned.

The authors acknowledge their "novel" approach and the lack of actual good data to really make these comparisons.  And their charts certainly look good.  But I'm not sure I get why this particular view adds anything.  If I'm missing something, let me know.