In a national survey of nearly 1,000 college students conducted earlier this year by Butler University in Indianapolis, more than half said they had used a Juul, the leading e-cigarette brand and prime target of regulators. An annual study by the University of Michigan found that the use of vaping products for nicotine and marijuana had doubled among college students between 2017 and 2018, one of the largest proportional increases since the study of adult drug use began more than 40 years ago.

In the face of mounting lawsuits from states, Juul has halted sales of mint and other flavored pods popular with teenage vapers, but many students said they had simply switched to other brands that offer fruity flavors and discounted vaping devices, some as cheap as 99 cents.

At the same time, the outbreak of lung injuries largely attributed to vaping products containing THC has convinced many students to return to old-school marijuana joints, bongs and pot pipes. One dealer, a student who started selling his own THC oil in January, said he has experienced financial and social fallout as sales have plummeted.

“You try to sell it at a party now, and at least one guy will come up to you and pontificate that you’re killing people,” said the dealer, who declined to be identified to avoid legal trouble.

While denying that his product was harmful, he conceded that he did not really know what the marijuana extract contained. “We buy it off the dark web,” he said. “We have no idea who’s selling it to us.”

One recent evening, The Cloud 9 vape shop near campus was doing a brisk business as students came in to buy cheap disposables and pods in flavors like “iced mango bomb” and “berry lemonade.”

Puffing on a device from behind the counter, Josh Evans, 21, said he was unfazed by the rash of lung injuries. He said he started vaping in college, a habit that replaced an addiction to dipping, which he started while playing baseball in high school.