The proof is in the pee. A federally funded study has confirmed, not surprisingly, that marijuana use went up in Washington state after its first legal pot stores opened in 2014. In fact, consumption appeared to double, at least in one major city, over three years — a conclusion scientists reached by way of the unglamorous work of analyzing raw sewage. “It’s stinky,” said lead author Dan Burgard, a chemist at the University of Puget Sound. “But we’ve worked with urine, we’ve worked with wastewater, and we’ve worked with port-a-potties. It’s not as bad a port-a-potties.” The research entailed driving...