Among U.S. President Donald Trump’s first actions after returning to office in January 2025 was imposing new tariffs on Canada, China, and Mexico, which he accused of sending fentanyl to the United States. The allegation against Canada was completely unfounded. China’s role in the story, however, is more complex. Beginning in 2015, the U.S. opioid overdose epidemic accelerated dramatically with the arrival of fentanyl imported at first directly from China and later manufactured in Mexico using cheap, Chinese-produced chemical precursors.
In 2000, 17,000 people in the United States died of drug overdoses, with only about 780 involving synthetic opioids such as fentanyl. Two decades later, fatal drug overdoses reached 92,000. By mid-2023, that figure had peaked at 111,000 over the previous 12 months, and 70 percent involved fentanyl. But unexpectedly, in June 2023, these gruesome numbers began to plummet. By September 2025, fatal drug overdoses over the past 12 months had fallen by almost 40 percent, to 73,000—well below the 2020 figure. The number of deaths involving fentanyl fell by nearly 50 percent. Canadian opioid overdoses declined more or less in parallel with those in the United States.
At first, some drug-policy experts thought the shift was just a return to baseline after the COVID-19 pandemic, when fear, grief, and social isolation led to increased drug use and a spike in overdose deaths. But the decline’s timing does not match up with the waning of these stressors: the downturn began well after COVID lockdowns had ended, and deaths kept dropping for two years. In an article we published in Science with our colleagues Kasey Vangelov, Harold Pollack, and Bryce Pardo, we found that the supply of fentanyl in both the United States and Canada constricted at around the same time as the downturn in overdose deaths. Because illegal fentanyl consumed in the United States is primarily imported from Mexico, whereas fentanyl consumed in Canada is also manufactured in Canada, the timeline raises the intriguing possibility that the supply shock came from China, which provides the precursor chemicals that underpin North American fentanyl production.
China is a source of the problem but also, potentially, of the solution. An effective crackdown by Chinese authorities on manufacturers of the critical chemicals needed to make fentanyl has the potential to reduce the U.S. fentanyl problem substantially. And if China has the power to constrain illegal drug actors, this could make fentanyl control an enduring feature of negotiations between Washington and Beijing, resulting in more collaboration—or friction, depending on whether overdoses rise or fall. Either way, to make successful policy, U.S. politicians need to get more curious about the full drug-supply chain.
OUT OF STOCK
The problem of illegally manufactured fentanyl is largely confined to North America. Fentanyl entered the Canadian and U.S. illegal opiate markets around 2014 because drug dealers in those two countries found it efficient to substitute cheap fentanyl for the more expensive heroin that previously dominated. Back then, there was little specific demand for fentanyl, and that demand could usually be satisfied by diverting fentanyl from the health-care system.
Initially, fentanyl was consumed mainly by heroin users, and it massively increased their death rate. The pool of potential consumers—and the number of fentanyl-related deaths—grew when dealers began marketing fentanyl via counterfeit pills, which reached populations that shunned injecting drugs. Other dealers began mixing it into methamphetamine and cocaine, many of whose consumers had not developed a tolerance to opioids.
Just as multiple factors drove up fentanyl deaths, more than one factor likely contributed to the decrease in deaths beginning in late 2023. Previous explanations have tended to focus on factors that reduced demand for fentanyl, such as more and better treatment options, increased availability of the overdose rescue drug naloxone, and a decline in use driven by fear of the drug. But none of these demand-side factors adequately explain the sudden, widespread downturn in drug deaths in both the United States and Canada. For example, naloxone became available over the counter in the United States in 2023, but that did not produce a corresponding increase in naloxone distribution, and at any rate, Canada had already taken that step many years earlier, in 2016.
China is a source of the drug problem but also, potentially, of the solution.
By contrast, trends in conventional supply indicators unexpectedly turned down at roughly the same time deaths did. Seizures of fentanyl by the U.S. Drug Enforcement Administration and U.S. Customs and Border Patrol started to fall in the second half of 2023. Likewise, the identification of fentanyl in laboratory analyses of drugs seized by state and local police agencies peaked in the first half of the year, then fell by 15 percent over the next six months. Fentanyl identifications continued falling through the end of 2024. They fell in Canada as well, by ten percent in the second half of 2023 compared with the first half of that year. A third supply indicator, the purity of seized fentanyl (in both powder and pill form), had been steadily rising before June 2023 but then suddenly started to decline, according to the DEA’s 2025 National Drug Threat Assessment.
An unconventional indicator of illicit fentanyl supply corroborates the theory of a supply shock. On the social media platform Reddit, the forum r/fentanyl allows 38,000 users to discuss use of the drug and share advice about how to deal with its risks. Related forums, such as r/heroin and r/opiates, also occasionally include discussions of fentanyl. We combed these discussions for mentions of a fentanyl “drought.” Before September 2023, there were few such mentions. Then, the frequency jumped 15-fold before the end of the year. There was no such increase in mentions of “drought” in reference to methamphetamine, for example, suggesting that Reddit users were having more trouble finding fentanyl in particular.
Multiple factors could have contributed to a fentanyl supply shock. In Mexico, one powerful faction of the Sinaloa cartel, which the U.S. government considers the principal producer of fentanyl bound for the United States, publicly announced in July 2023 that it was prohibiting independent labs from producing and selling fentanyl on its turf. Soon thereafter, small independent labs did indeed shut down; some independent producers of the drug were found dead. Furthermore, the DEA and U.S. Customs and Border Patrol were making more cases against high-level traffickers, which could have made trafficking less efficient and disrupted the delivery of fentanyl to the United States.
But developments in Sinaloa do not adequately explain why fatal fentanyl overdoses also fell in Canada, where illegal fentanyl is primarily manufactured domestically, not imported from Mexico or the United States. Canadian fentanyl production uses precursor chemicals from China, just as Mexican producers do. (Precursors in North America are strictly controlled and therefore have no legal markets. China, on the other hand, has the world’s largest chemical industry and looser restrictions.) Therefore, it seems possible that these downward trends in fentanyl supply and overdose deaths are linked to reduced flows of precursor chemicals from China.
CONTROLLING THE CHEMISTRY
There is no way to accurately analyze the flow of chemical precursors without information from Beijing. Accessing transparent and credible data on the conduct of the Chinese government is generally challenging, and this is certainly the case with regard to its actions against precursor producers. Chinese authorities want to protect their reputation for independent decision-making and do not want to appear to be acting at the behest of the U.S. government. For example, in the early 2000s, China tightened environmental regulations but rarely highlighted its moves in international negotiations.
Nonetheless, in May 2019, China added fentanyl to its list of controlled substances, which impeded the domestic production of the drug (although not of its precursor chemicals). The policy seems to have largely eliminated the direct importation of fentanyl into North America from China. Then, beginning in 2023, Chinese authorities appear to have clamped down on the manufacture of chemical precursors as well. That year, the U.S. Department of State’s international narcotics bureau found that Chinese authorities investigated 274 cases and seized about 1,000 tons of precursor chemicals. This represents a 42 percent increase from 2022. There were also efforts to shut down websites advertising precursors.
In the second half of 2023, as U.S.-Chinese relations started to recover from the tension created by U.S. House Speaker Nancy Pelosi’s visit to Taiwan a year prior, China began taking additional actions to regulate precursors, both alone and in cooperation with the United States. Chinese law enforcement agencies stepped up the management and supervision of precursor chemicals, including by improving licensing procedures, increasing inspections, and implementing new technologies. After the meeting between U.S. President Joe Biden and Chinese Leader Xi Jinping in November 2023, the two agreed to cooperate on counternarcotics. China’s National Narcotics Control Commission issued a warning against supplying precursors, especially to North America. The Chinese government also ramped up controls on fentanyl precursors to comply with the United Nations’ counternarcotics treaties. (It was only in June 2025, however, that Beijing came into full compliance.) According to the DEA, these moves by Chinese authorities may well have made Chinese precursor producers wary of supplying controlled precursors to international customers.
Chinese authorities seized about 1,000 tons of precursor chemicals in 2023.
Other explanations cannot be entirely dismissed: the decline in overdose deaths in the United States started a bit earlier than did regulation and enforcement actions in China, although some might argue that substantial operations in the second half of 2023 must have been preceded by earlier efforts. Further, foreign policy analysts such as Vanda Felbab-Brown, the director of the Brookings Institution’s Initiative on Nonstate Armed Actors, maintain that if Beijing were responsible for blunting the U.S. fentanyl epidemic, Chinese officials would have been very public about it from the beginning.
On the other hand, Beijing had some motives to keep its efforts out of the public eye. If it touted its successes, it would be tacitly admitting to an earlier failure to control its fentanyl exports. And even if Chinese actions helped, the flow of fentanyl to North America was not completely eliminated; Trump might well still have used China’s fentanyl involvement to justify imposing tariffs. After all, the fact that Canada does not export appreciable amounts of fentanyl to the United States did not stop the president from slapping tariffs on imports from Canada.
It is also puzzling that the decline in fentanyl overdose deaths has lasted so long. Control efforts do not usually drive down supply by so much or over such a long period because drug producers and traffickers tend to be highly adaptive. A decrease in the supply of precursor chemicals from China would, in theory, induce a shift toward importing precursors from elsewhere. India, for example, is home to the world’s second-largest pharmaceutical industry. Although more transparent and better monitored than its Chinese counterpart, it is inconsistently regulated, arguably even corrupt. Yet there is still little evidence that India has become a regular source for North American fentanyl refiners.
Conceivably, coincidentally parallel efforts in both Canada and Mexico to stymie fentanyl production could have driven the death-rate declines. Canadian enforcement has had conspicuous successes, including record seizures of precursors in 2022 and the shutdown of multiple superlabs, particularly beginning in 2024. Shifts in Canadian supply indicators are only broadly consistent with those in the United States; they do not pivot on the same day.
KNOW YOUR ENEMY
The overall pattern, however, is suggestive of involvement by Beijing. And considering a Chinese role in blunting the fentanyl epidemic in North America matters. If Chinese actions to control the supply of chemical precursors contributed to the recent decline in overdose deaths, it may stand as a rare example of quiet superpower cooperation saving tens of thousands of lives. It may also reflect internal dynamics of China’s government—dynamics that analysts would do well to try to better understand.
Unfortunately, political factors within the United States may unreasonably inhibit attempts to understand the possibility that Chinese efforts affected the U.S. fentanyl crisis. Some prominent elected officials in Washington simply believe that supplying the United States with cheap fentanyl is part of China’s campaign against its most important strategic rival. The public health field and academia are also generally hostile to any policy aimed at controlling illicit drug supply. The excesses of the war on drugs—namely the high rates of incarceration it drove, disproportionately among racial minorities—have cast a shadow over a whole array of supply-control policies. These powerful voices thus bridle at crediting precursor controls with even modest success.
If China’s actions did not constrict the fentanyl supply, then the mystery of what did drive down deaths only underscores how little Washington and Beijing understand about the forces they are trying to manage. In part, this reflects the extraordinary unwillingness of either Democratic or Republican administrations to invest in regular monitoring programs that would provide insight into the dynamics of drug markets. Amazingly, even as drug overdoses soared to catastrophic levels, some of the major monitoring programs were abandoned. But improved data systems would help nations understand and interdict global supply chains for illicit drugs, especially if implemented in cooperation with the international community. What is certain is that fentanyl is no longer just a public health emergency. It is a reminder that in a fragmented world, even chemistry has become geopolitics.
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