At a white elephant party I attended a few years ago, by far the most popular item—amid the scented candles and picture frames—was a half-full bottle of codeine, brought by a friend who figured her old meds could provide someone with a bit of holiday cheer. This might not have been the most ethical (or legal) way to dispose of a prescription medication. But I remember wondering, "Well, what should you do with unused prescriptions?" If you flush the stuff, does a fish somewhere downstream end up stoned? So I poked around a bit to find out exactly what the deal is.

Can I toss my extra prescription meds down the toilet? As recently as a few years ago, that was the default. But now pretty much everyone agrees it's a bad idea, because some of the more than $230 billion worth of prescription drugs used by Americans every year will make it through the sewage treatment process and into the waterways. (The Food and Drug Administration still recommends flushing OxyContin, Percocet, morphine, and a couple of dozen other drugs so kids and pets can't fish 'em out of the trash.)