I became a real cross-country skier a decade ago, on the eve of a big race. I stood before the register at my local ski shop, coveting a matchbook-size, yellow sliver of ski wax priced at $5 a gram, feeling my pulse race, my fingers quavering as I thrilled over the glory and speed this little wafer of magic could bring once I ironed it into the base of my skis. I laid down a hundred bucks for that wax, and I’m almost certain I covered 50 kilometers a few minutes faster thanks to it. How could I not have? Fluorinated ski wax is so eerily effective that, in describing it, fellow skiers at times drift toward the rhetoric of religion. “It’s the most joyous thing I’ve ever experienced,” Andrew Gardner, until recently the head coach of Nordic skiing at Middlebury College, says of gliding on fluorinated boards. “It’s so completely unnatural.”

The fastest fluoro wax contains a synthetic fluorine-based compound—perfluorooctanoic acid, or PFOA, which boasts eight fully fluorinated carbon molecules in its long backbone. The compound’s star is fluorine. This element forms a tighter chemical bond with carbon than any other, and it creates, essentially, a shield against the ski-slowing moisture that pervades snow most thoroughly when temperatures approach or rise above 32F. Once bonded with carbon, fluorine is exquisitely unreactive; it scarcely sticks to anything. That’s why PFOAs are a key ingredient in Teflon. When firefighters spray foam laced with PFOAs onto a blaze, it has a suffocating effect…