Plutonium Bacon?

      The headline went splashing though social media last week: World Health Organization Says Bacon As Deadly As Plutonium.

      It sounds awful.  Did they really say that?  Not exactly.  The report does classify processed meat  as carcinogenic in their highest-danger classification, Group 1, along with asbestos and plutonium.  But it's not a scale of deadliness-per-unit volume, only of how well-linked a substance is to causing cancer.  It's confusing and has prompted articles trying to explain what it means and generally succeeding.

      Here's the thing to know: "The dose makes the poison."  Paracelsus wrote that in 1538 -- and he was right.  A cross-grained iconoclast after my own heart, he valued practical experience and rigorous experiment as pathways to accurate knowledge.  Plutonium has an LD50 -- the amount that will kill half those who ingest it it -- of 0.00032 grams per kilogram of body weight; if bacon were composed of pure sodium nitrate (it's not), its LD50 would be 0.18 g/kg (source).

      I'm using toxicity as a crude proxy for carcinogenic qualities; this is fast, sloppy and inaccurate, but it lets us compare orders of magnitude easily.  A speck of plutonium with your breakfast is a very big problem, while a speck of bacon is not.  It appears there's a threshold level for processed meat: eating too much bacon is indeed bad; eating a little bacon, you can treat as a manageable risk, the same as driving a car or hanging out with your friends and family. (Not everyone agrees how much bacon is too much or how little is just right.)

      If you're having bacon bits for breakfast in place of oatmeal and washing them down with hot bacon fat, you're in trouble.  If you're averaging one strip of bacon or less in the morning, you take far higher risks every day in the shower.

      (Details for geeks: most risky activities have a linear relationship between increasing frequency or volume and increasing risk -- except at the very low end, where things get nonlinear: maybe even a tiny dab will do you in; maybe mitigating strategies work up to a point [sunscreen/hat]; maybe the risk goes to zero ahead of the volume, or the slope even reverses [water intake, for example, where too much can eventually be as deadly as too little].  Understanding these low-end-of-the-curve behaviors is essential to managing risk intelligently.)