SAN FRANCISCO — For years, a divisive debate has raged in the United States over the health consequences of nicotine e-cigarettes. During the same time, vaping of a more contentious substance has been swiftly growing, with scant notice from public health officials.
Millions of people now inhale marijuana not from joints or pipes filled with burning leaves but through sleek devices and cartridges filled with flavored cannabis oils. People in the legalized marijuana industry say vaping products now account for 30 percent or more of their business. Teenagers, millennials and baby boomers alike have been drawn to the technology — no ash, a faint smell, easy to hide — and the potentially dangerous consequences are only now becoming evident.
Most of the patients in the outbreak of severe lung illnesses linked to vaping — which has left 1,479 people sick and 33 dead so far — vaped THC, the ingredient in marijuana that makes people high. Until more information is known, officials at the Centers for Disease Control and Prevention have warned people not to vape cannabis products.
To some scientists, and even industry leaders, warning signs have been apparent for years as vaping cannabis grew in the shadows, propelled by a patchwork of regulations, a wave of state-by-state legalization and a soaring supply of low-cost marijuana.
While the government and researchers poured resources into studying e-cigarettes, federal rules sharply limiting research into the health effects of cannabis — because it is classified as a controlled substance with a high potential for abuse — have left a void in scientific knowledge about what THC vaping does to the lungs.
Last year, Dr. Neal Benowitz, a professor of medicine and a researcher on nicotine and vaping at the University of California, San Francisco, sent a letter to Congress warning of the risks posed by leaving a hugely popular practice unstudied.
“Very little is known about the safety or effects of vaped cannabis oil,” he wrote, cautioning that some ingredients mixed into the oils “could have harmful, toxic effect on users, including the potential for causing and/or promoting cancer and lung disease.”
“It’s disgraceful,” Dr. Benowitz said in a recent interview as reports of hospitalizations and deaths from vaping-related lung illnesses mounted. “I’m not able to take products we think are potentially harmful and do analysis. I can buy a vape device around the corner, but I can’t bring it into the lab and test it.”
Even members of the legalized marijuana industry acknowledge the lack of hard science about the cannabis vaping products they sell.
“There’s a glaring gap in trying to understand this product,” said Jerred Kiloh, president of the board of the United Cannabis Business Association, which represents 165 marijuana dispensaries in California, where marijuana was legalized for recreational use in 2016.
Mr. Kiloh, who owns the Los Angeles dispensary Higher Path, said he believed that the vape pens sold in his stores and in other licensed and regulated stores are likely safe because the ingredients were measured and tested by the state. The Bureau of Cannabis Control did not return calls asking for comment.
Vaping oils typically include other additives, solvents and flavor enhancers, and health investigators believe some such ingredients, including vitamin E acetate, could be responsible for some of the lung illness cases. The problem of unknown and potentially dangerous additives, Mr. Kiloh and others said, is vastly worse in a soaring black market in the nearly 40 states where recreational marijuana is still illegal.
Even in states where the drug is legal, counterfeit cartridges are cheaper than the licensed, tested and taxed products. It is hard for legal players who pay taxes to compete. A regulated vape pen with half a gram of THC costs $55, compared with $25 or less on the street for an untested product.
“We don’t know what the chemical composition is,” Mr. Kiloh said, “and we especially don’t know what the chemical composition is once it’s been combined, heated and inhaled.”
No Ash, No Rolling Papers
In the earliest days of cannabis vaping, a small group of innovators saw the technology as a safer way to help medicinal marijuana patients. They hoped that vaping — which entails heating THC so that it turns to an aerosol — would be less harmful to the lungs than inhaling combusted marijuana.
But that ethos quickly gave way to a different lure: the pure convenience of vaping, which allowed users to avoid rolling joints, spilling ash, giving off a telltale smell — or getting caught. Vape pens brought the sheen of high technology to a drug associated with hippies and grunge, along with the discretion of, say, texting beneath the dinner table.
“You could vape in a police station and no one would even know, not that you’d want to do that,” said a 35-year-old man outside Harvest, a marijuana dispensary in San Francisco, who declined to give his name because he said he did not want to hurt his job-hunting prospects.
Other Harvest customers said they once embraced vaping but now have doubts. “It’s convenient, neat, easy. No lighter,” said Michael, who, with his wife, Laurie, both in their 70s, declined to give a last name because they didn’t want their teenage granddaughter to know about their habit.
With news of vaping-related hospitalizations and deaths, though, Laurie was growing concerned. So this time she came to Harvest to buy flower, the old-fashioned bud rolled in joints. It was a switch the couple said they would continue while they await more vaping science.
Others were undeterred. Cynthia Valdivia, 34, bought a THC vape cartridge after using one to try marijuana for the first time this summer. She said she was not worried about what she bought from a legal store.
“There’s someone behind the brand and they don’t want to kill people,” she said. “They want their money.”
The market has flourished in the absence of regulation, said Eric N. Lindblom, a former tobacco official at the Food and Drug Administration. The federal government, he said, has been unsure of how to respond to state legalization of marijuana, and the uncertainty has left a void of regulation, research and enforcement.
“Only now that we have this special, extra weird mystery crisis with the disease and deaths is there now interest in doing something,” he said.
Some think it may be too late.
“The market has run amok,” said Carlos de la Torre, the owner of Cornerstone Wellness, a dispensary in Los Angeles.
Mr. de la Torre came to the cannabis business in 2007 after a career in television advertising. That year he opened his shop in a Los Angeles suburb, selling marijuana flower and edibles to customers with medical cards.
“At the time, I don’t think vaping really existed,” he said.
Not commercially, at least. There was a rich and informal history among a narrow band of regular marijuana users who bathed weed in alcohol to extract THC — so-called honey oil or hash oil. That was the domain of the “biker, LSD, hippie crowd,” said David Downs, the California bureau chief of Leafly, a cannabis news and product website.
The first commercial marijuana vaping brand was called the Volcano, and it was the brainchild of a German entrepreneur, Markus Storz, who obtained a patent for it from his native country in 1999.
The Volcano came to the United States in 2003, and it is aptly named. It is built on a sturdy, triangular-shaped base — “the kind of thing that sat on a coffee table and weighed a pound,” Mr. de la Torre said.
It heated marijuana flower until the THC baked off as vapor. A user then inhaled the aerosol from a large plastic bag attached to an inhalation pipe.
Industry insiders thought it might be healthier than smoking a joint because burning marijuana contains carcinogens like tar and carbon monoxide. “If we were really helping cancer patients, then adding carcinogens was not helpful,” said Mr. Kiloh, who in 2003 opened his first medical dispensary, Green Cross, in San Francisco, seven years after California legalized marijuana for medical purposes.
Federal research restrictions allow the study of marijuana under certain conditions, and scientists at the University of California, San Francisco, found that the Volcano produced less carbon monoxide and tar compared with smoking marijuana.
The Volcano was built around inhalation of pure marijuana vapor, created by heating the plant itself. In a few years, the technology would change in a fundamental way.
“What happened was that the oil came next,” Mr. Kiloh said.
Entrepreneurs began to extract oil by bathing the leaf in ethanol or butane, filtering out the solid material that remained and then evaporating the solvent to leave the concentrated oil. Another method used carbon dioxide, which, when pressurized, creates a fluid that can be used to extract the oil. (There is no “toxicological” research about the relative health effects of the different methods, according to Christopher Havel, an analytical chemist at U.C.S.F. who works with Dr. Benowitz).
Once extracted, the THC oil could then be heated up using a small battery, kept in a cartridge or penlike case, creating aerosol, which is then inhaled from one end of the device. Consumers fell in love.
As marijuana became legal in a growing number of states, a new area of entrepreneurship burgeoned. Businesspeople found they could use the entire plant to extract oil rather than throw away stems and other parts discarded by smokers, which maximized the value of the crop.
The oil also could be mixed with other additives to give flavor, to create the effect of big puffs of smoke or just to cut the THC to substitute less expensive chemicals.
At the time, Mr. Kiloh was dubious: What was in these things? The packages either did not list ingredients or, if they did, the labels seemed untrustworthy, he said, because the oil sometimes smelled off.
Sometimes he would test the product and discover the THC had been watered down, initially with propylene glycol, which is used in fog machines, to add a smokey luster.
“People started getting greedy,” Mr. Kiloh said, describing the early vape pen manufacturers around 2012. “You didn’t know how much was propylene glycol and how much was THC.”
After initially carrying the vape pens in his dispensary, Mr. Kiloh temporarily pulled them from his shelves.
“I didn’t want to sell them,” Mr. Kiloh said. “What people said for the next three or four months was, ‘Can you bring them back?’” But he told them he wasn’t sure the pens were safe.
Mr. Downs, of Leafly, said the worry was valid. “It’s very clear innovation has eclipsed the sophistication of consumers as well as regulators and investigators,” he said. “We’ve been engaging in an uncontrolled mass experiment with inhaling concentrations of cannabinoids.”
In states that legalized marijuana, farmers could grow the crop openly, creating a vast, lower-cost supply that flooded not just legal markets but spilled into illegal ones, said Beau Kilmer, director of the Rand Drug Policy Research Center.
Prices plummeted. While national figures are hard to come by, Rand’s research shows that an oversupply in Oregon caused the price per pound to fall more than 50 percent, from $1,250 in 2016 to $500 in 2018.
Much of the product went to oil.
“The fastest growing segment of the market is extract for inhalation,” Mr. Kilmer said.
And researchers remain in the dark. In August, the Drug Enforcement Administration loosened rules to allow some scientific institutions to apply to grow their own marijuana for study. However, the restrictions still prevent researchers like Dr. Benowitz from examining the kind of THC oil sold widely on the legal and black markets.
He summed up what little is known about vaping THC oil: “All we know is that there weren’t many problems until recently.”