It’s the big threat. A cheap, white powder — 50 times more powerful than heroin — which kills more than 70,000 people each year in the United States and countless others across the rest of the Western Hemisphere. EL PAÍS, in a long-term investigation that spanned two continents and included interviews with anti-drug czars in the U.S. and China, visited the clandestine laboratories in Sinaloa, where fentanyl is manufactured. In the vicinity of these Mexican labs, addicts serve as guinea pigs for drug traffickers. This newspaper has gathered testimonies about how this lethal substance crosses the border to the north and spreads like a plague through the streets of the most powerful country in the world. The trafficking of fentanyl is part of a global network with one foot in China, which the White House has declared war on