Answer: Radiation

You did, in fact, read both today’s trivia question and answer correctly—despite how counter-intuitive it might seem that alcohol sold for human consumption is radioactive. Now, at first glance, that requirement may seem to imply the vineyards, breweries, and distilleries have to add radioactivity to their alcohol to pass some sort of test, but the reality is that the test is not for alcohol that has been fortified, if you will, with radioactive material, but that was made from naturally radioactive material to begin with.

In the U.S., there are strict laws regarding alcohol production with “natural” materials—alcohol intended for human consumption must be made from fermented plant material. Fermented plant material is naturally (and very mildly) radioactive because of tiny amounts of radioactive isotopes in the environment that are absorbed by the plants used for fermentation (such as corn, potatoes, and the malted grain seen here.) This is exactly, by the way, why bananas are one of the more radioactive plants around—bananas are high in potassium and a chunk of the potassium they suck up from the soil is a radioactive isotope.

All this begs the question of course, where exactly would people get ethanol if not from fermentation? You can create alcohol in the lab by hydrating ethene, repeating the process until you reach a high level of purity, and then chemically extracting the last of the unlinked ethene to yield pure ethanol. Where can you get lots of ethene for such a process? From petroleum. At the end of the process, the pure ethanol created by fermentation and distillation and the ethanol created from petroleum extraction are chemically identical and indistinguishable from each other—except for those tiny trace amounts of radioactivity.

When the Bureau of Alcohol, Tobacco, Firearms, and Explosives tests a sample of alcohol, then, they use the only test they have that can detect if the alcohol was fermented from recently growing plants or manufactured using oil created millions of years ago: the presence of those radioactive isotopes.