Don’t sniff the water
Q: Did you see “Cocaine now on tap in British homes” in the Herald
A: Yes.
Q: Is it true?
A: Not so as you’d notice.
Q: Didn’t they find traces of cocaine in drinking water?
A: Up to a point.
Q: You mean no?
A: I mean they found traces of the chemical that cocaine gets broken down into
Q: And is that a drug?
A: Not really. It was one component of an unsuccessful treatment for back pain. It is restricted, because it can be turned into cocaine.
Q: How much of this stuff did they find?
A: Almost none. A few nanograms per litre
Q: What’s that in real numbers? If it was really cocaine, how long would it take you to get one dose if you drank eight glasses of water a day like the doctors recommend?
A: That isn’t actually what the doctors recommend.
Q: Well, then, “like the doctors don’t recommend?”
A: Several centuries.
Q: How can they detect such tiny amounts?
A: They use liquid chromatography to separate out each chemical, and then mass spectroscopy to basically count the molecules.
Q: Ok, impressed now. The story also mentions “significant amounts of caffeine”. What does that mean?
A: It means “insignificant amounts”, about a million times lower concentration than in a cup of decaffeinated coffee.
Q: At least this is new, though?
A: The same agency reported finding the cocaine metabolite in drinking water in 2011, based on measurements in 2009-10. (PDF, Table 6)
Q: Why is there a video of a drug bust in Spain embedded in the story?
A: Because technology.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »