HONG KONG — China has a major meth problem. The drug can be a pick-up, a pastime, or something that builds trust—or addiction. It mostly comes from North Korea and it’s been flooding northeastern provinces for years. Domestic distribution networks then move the drug west and south to reach more users.

I have seen workers abuse it in Chinese electronics factories so they can stay awake when trudging through unending shifts. Camgirls (models who perform or strip online for a fee) and karaoke hostesses smoke it with their clients, who call the practice “ice-skating.” Businessmen who dabble in too many vices share it for a brotherly bond. Chinese celebrities apprehended in drug crackdowns often admit to using meth.

Production of this speed was once organized by the Democratic People’s Republic of Korea as a way to keep its foreign currency slush fund afloat. The operation was overseen by Bureau 39 (also called Office 39 and Room 39), a secretive component of the Kim regime that does anything from forging high-quality American currency to running a chain of restaurants. More heinous is the production and sale of narcotics.

Poppy farms existed in North Korea in the 1970s, and the DPRK developed an opiate production program for export. But major floods and agricultural disasters devastated the crops. Switching to something that could be made in a lab quickly and in large quantities provided two benefits: It suited the regime’s need to raise large amounts of foreign currency, and domestic use of meth killed the actual, physical hunger of a starving population.

Aside from narcotics and counterfeit currency, knockoff pharmaceuticals and cigarettes contribute to the illicit income of the DPRK. In all, Bureau 39’s illicit activities might be adding as much as $1 billion to Pyongyang’s coffers every year.

At home, North Koreans might see meth as something of a luxury. During Chuseok, a festival to give thanks for bountiful harvests that doubles in the North as a chance to offer bribes, beef and meth were popular gifts for officials.

The DPRK is hugely reliant on China. The two Peoples’ Republics have messy ties, but it’s one of the few meaningful relationships that the DPRK has. Beijing provides aid to Kim Jong-un, and traders from North Korea cross into China to conduct business. China is the Kim family’s backer on the world stage, propping up the hermit kingdom’s economy despite its belligerence.

North Korean meth used to be trafficked by DPRK officials, but after a series of scandals and subsequent denials, the practice of delivering drugs through diplomatic cargo was largely abandoned by the mid-1990s. Production persisted, but distribution was handled by Asian crime rings that took on some of the Kim regime’s dirty work. Pushing large shipments of meth into northeastern China via regular trade routes was the natural move.

Then, things shifted in Pyongyang. “There's some evidence that in the mid-to-late 2000s, the government decided to close some of the larger, export-oriented, regime-supported manufacturing facilities,” said Sheena Greitens, non-resident senior fellow of the Brookings Institution, in an interview with The Daily Beast. “When that happened, chemists and others set up private facilities, either repurposing equipment or copying from what they’d learned in the state factories. They then tapped into the existing black market inside North Korea and the cross-border smuggling networks into northeastern China to distribute their products.”

Within North Korea, there is an incredible proliferation of crystal meth. Defectors who have reached South Korea estimate up to 80 percent of residents in some towns have used the drug. In 2013, a study by North Korea Review estimated over 40 percent of meth users in the DPRK are addicted. More recently, the wives of North Korean Party cadre have apparently been trying out a drug diet, turning an ugly thing into a fad.

China acknowledges the meth problem in its northeastern corner, but doesn’t spell out where the drugs come from. Information about the DPRK is treated as a sensitive item in China, so news about North Korean meth is virtually unheard of in state media.

What is reported is ripped from South Korean reports, and is more about the middlemen who handle meth shipments rather than the source.

Meanwhile, China has waged a high-profile war on drugs at home, with a heavy focus on synthetic drugs. That has put a squeeze on the DPRK’s meth revenue, and the decline in seizures suggests official production facilities may have been slowly shutting down.

The North Korean health system lacks drug education and treatment, but the regime now discourages its citizenry from using meth by appealing to their patriotic duties. Greitens said the North Korean government shapes the message by pointing out drug use leads to weakness, which can then be exploited by foreign powers, much like what China faced in the bitterly remembered 19th-century Opium Wars.

In 2010, Chinese police seized $60 million worth of North Korean meth, likely only a fraction of what was actually shipped worldwide. In a 2013 report on international narcotics control, the U.S. State Department says “there have been no confirmed reports of large-scale drug trafficking involving DPRK state entities since 2004,” and suggests that “state-sponsored trafficking may have ceased or been sharply reduced, or that the DPRK regime has become more adept at concealing state-sponsored trafficking of illicit drugs.”

But that did not take into account the underground activity. With few alternate employment options, and despite shutdowns, crackdowns, and sanctions, the chemists behind decades of meth production in North Korea have set up their own operations.

“Manufacturing methamphetamine requires relatively little in the way of sophisticated equipment; it can be manufactured in a bathtub in someone's home,” said Greitens. “That’s one reason why it was relatively easy to privatize (or partially privatize) production inside North Korea.”

“Evidence from my interviews with people involved in the manufacturing and distribution of methamphetamine made inside North Korea,” said Greitens, “consistently indicates that the precursor chemicals are coming from China via cross-border illicit trading and smuggling networks.”

All this happens even though the governments of China and North Korea aren’t on the best of terms. After Pyongyang announced its supposed H-bomb detonation in early January, U.S. Secretary of State John Kerry spoke to his Chinese counterpart, Wang Yi, and made clear that China’s approach to North Korea has failed. He urged China to end “business as usual with North Korea.”

Maybe Beijing heard that plea. In late January, Wang Yi agreed to move ahead with a United Nations resolution condemning the DPRK for this latest nuclear test, although it looks like China will not agree to expanded sanctions on North Korea. “Our position will not be swayed by specific events or the temporary mood of the moment,” Wang said.

Meanwhile, when it comes to their own “temporary mood,” more and more Chinese are relying on North Korean chemistry.