As Donald Trump travels to Beijing this week, fentanyl and China's role in its supply chain remain a point of acrimony in bilateral relations. At a UN meeting in March, the US again accused China of failing to stop its chemical industry from selling precursors for the synthetic opioid, while China suggested the US was shifting blame for its domestic drug problem.
Yet there are growing signs that the US fentanyl crisis has turned a corner, and some experts believe that interventions in China have played a key role. 'There was a supply shock: the purity of fentanyl fell,' said Keith Humphreys, a professor at Stanford University. 'The question is why there was a supply shock. And most indicators point to China.'
Declining Overdose Deaths
Upon returning to the White House, Trump made fentanyl a foreign policy priority, designating criminal groups as foreign terrorist organizations and slapping tariffs on countries involved in its supply chain, including China, the main source of fentanyl precursors. But by summer 2023, during the Biden administration, overdose deaths at the national level had already begun to fall. By November 2025, they were down by more than a third.
The Purity Drop
Investigators are still unpicking the factors behind the decline. One theory, put forward by Humphreys and co-authors in a recent study in Science, links it to interventions in China that may have caused a long-lasting disruption to the fentanyl supply chain. The authors point to a dramatic fall in the purity of fentanyl seized by US law enforcement from May 2023 to the end of 2024, which correlates with the fall in overdose deaths. A similar drop in purity occurred in Canada, a distinct fentanyl market, suggesting the cause might originate where both source their precursors: China.
The idea that the flow of precursors was disrupted is supported by reports of cartel cooks struggling to source them, while new adulterants appeared in fentanyl on US streets, indicating experimentation with alternative synthesis pathways.
Caveats and Perspectives
There are big caveats. It is difficult to pinpoint which of China's self-reported interventions might be responsible, and it is unclear that the fall in purity caused the drop in overdose deaths. Nonetheless, Liu Pengyu, spokesperson at the Chinese embassy in Washington, said China was glad to see fentanyl overdose deaths decrease and noted that the US government's 2025 National Drug Threat Assessment 'implies that Chinese government efforts have made a contribution to addressing the fentanyl problem in the US.'
Henrietta Levin, former director for China on Biden's National Security Council, said her former colleagues saw the Science paper as showing that pressure on China had worked. 'I think China could have done more, but what they did do mattered,' she said. Further supply-side interventions are likely on the agenda at this week's summit. Ideally, these would include China changing laws to prosecute drug trafficking more easily and more action from its commerce ministry to control chemical companies' behavior. 'A lot of this comes down to enforcement,' said Levin. 'China announced export controls on various fentanyl precursors, and that's important. But Chinese chemical companies are gauging how serious the government is about enforcing those restrictions.'
Historical Lessons
Yet history shows that, as long as demand exists, supply shocks are always temporary and can have unpredictable effects, even making things worse. It was only after China put a blanket ban on fentanyl in 2019 that the supply chain evolved to loop Mexico's cartels in, who began importing precursors from China and trafficking the finished product over the US-Mexico border, almost entirely replacing their previous heroin trade. 'There's a kind of myopia here,' said Nabarun Dasgupta, director of the University of North Carolina's opioid data lab. 'That time, the geopolitics of it backfired.'
