Late last month, the 18-year-old student athlete in Gurnee, Illinois, was hospitalized after using e-cigarettes for more than a year and a half. Now his lungs are similar to those of a 70-year-old adult, doctors told him.

"It was scary to think about that -- that little device did that to my lungs," Adam said, remembering the news from his doctors about his lung health.

Adam is among the hundreds of e-cigarette users in the United States who have been sickened with mysterious vaping-related lung illnesses , many of them young people. Investigators haven't yet identified the cause of the illnesses.

Amid calls for more regulation, the Trump administration now plans to remove flavored e-cigarettes -- except tobacco flavor -- from the marketplace.

"Why is that important? We are seeing an absolute surge in high school and middle school kids using these flavored products," US Health and Human Services Secretary Alex Azar said in a video statement on Wednesday. "Mint, menthol, fruit flavor, alcohol flavor, bubble gum."

The US Food and Drug Administration announced on Wednesday that more than a quarter of high school students this year have reported using e-cigarettes and the "overwhelming majority" reference using popular fruit and menthol or mint flavors, according to preliminary data from the National Youth Tobacco Survey.

Adam, who vaped nicotine and THC products, said he isn't sure his lungs will ever be back at 100% -- and he worries whether he will ever be able to wrestle again.

"I was a varsity wrestler before this and I might not ever be able to wrestle because that's a very physical sport and my lungs might not be able to hold that exertion. ... It's sad," Adam said.

'We must act swiftly'

There are more than 450 possible cases of lung illness associated with using e-cigarettes across the United States, according to the US Centers for Disease Control and Prevention , which has called this an "outbreak."

Health officials have also confirmed six deaths -- in California, Illinois, Indiana, Minnesota, Oregon and Kansas -- in connection to vaping-related lung illnesses.

While the illnesses and deaths have occurred in both young people and older adults, experts have warned of a rise in vaping among youth.

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"We must act swiftly against flavored e-cigarette products that are especially attractive to children," Acting FDA Commissioner Dr. Ned Sharpless said in the announcement, adding that the FDA will take additional steps to address youth use of tobacco-flavored products still on the market, if young people begin to use them.

"The tremendous progress we've made in reducing youth tobacco use in the US is jeopardized by this onslaught of e-cigarette use. Nobody wants to see children becoming addicted to nicotine, and we will continue to use the full scope of our regulatory authority thoughtfully and thoroughly to tackle this mounting public health crisis."

Separate surveys also suggest that most teens think e-cigarettes are safe.

Adam certainly thought vaping was safe when he started using e-cigarettes, he said. One of his favorite flavors was mango.

'It tasted good and it gave a little head high'

"I first started vaping just to fit in, because everyone else was doing it," Adam said, adding that the flavors appealed to him, especially mango.

"It didn't taste like a cigarette," he said. "It tasted good," and provided a little buzz due to the nicotine

The vaping began about a year and a half ago, he said, and he would pick up e-cigarette products, such as those of the Juul brand, from his neighborhood gas station.

"They didn't card me," he said.

"He would wake up in the morning and would puff on that Juul and then cough," said Adam's mother, Polly Hergenreder.

"He would hit it several times throughout the day. My son was going through a pod and a half every other day, or a day and a half."

Experts say that one Juul pod -- a cartridge of nicotine-rich liquid that users plug into the dominant e-cig brand -- delivers the same amount of nicotine to the body as a pack of cigarettes. "That's smoking a lot of cigarettes," Polly said.

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Eventually, Adam said that he went from vaping over-the-counter e-liquids to vaping THC or tetrahydrocannabinol, which is the main psychoactive component of marijuana. Adam would get the THC from "a friend" or dealer.

Over time, Adam said that he developed shivers and couldn't control them. Then, the vomiting began.

"I was just nonstop throwing up every day for three days," he said. "Finally I went to the pediatrician."

At first, doctors did not connect Adam's symptoms to his vaping. He was given anti-nausea medication, but he said that his vomiting did not stop. After visiting various physicians, he finally saw someone who asked if he was "Juul-ing" and using THC.

"I answered honestly," Adam said. "I said I was."

The team overseeing Adam's care performed a CT scan of his stomach and noticed something unusual about the lower portion of his lungs. The doctors then took an X-ray of his lungs.

"That's when they saw the full damage," Adam said.

"If I had known what it was doing to my body, I would have never even touched it, but I didn't know," he said about vaping. "I wasn't educated."

'If we did not bring Adam in ... his lungs would have collapsed'

Adam was admitted to the hospital in late August.

"If his mom had not brought him to the hospital within the next two to three days, his breathing could have worsened to the point that he could have died if he didn't seek medical care," said Dr. Stephen Amesbury, a pulmonologist and critical care physician at Advocate Condell Medical Center in Illinois, who was one of the doctors who saw Adam.

"It was severe lung disease, especially for a young person. He was short of breath, he was breathing heavily," Amesbury said. "It was very concerning that he would have significant lung damage and possibly some residual changes after he heals from this."

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Adam's mother Polly spent the following six days in the hospital with her son, who was connected to IVs and was provided oxygen through nasal tubes.

"The doctors did tell us that if we did not bring Adam in when we brought him in, his lungs would have collapsed and he would have died," Polly said.

Yet, she added, "you should always try to find the silver lining," and for her family, that is to use Adam's experience to educate others about the risks of vaping.

Adam is now home from the hospital and "it's still difficult to even do normal activities, like going upstairs. I still get winded from that," he said.

Even though he is still recovering -- including doing breathing treatments -- Adam has focused on sharing his story. Through his advocacy, he said that he has even convinced some of his friends to stop vaping.

"I'm getting better each day," he said. "I don't want to see anybody in my situation. I don't want to see anybody in the hospital for as long as I was."

Lawsuit filed

On Friday, Adam filed a lawsuit against Juul Labs and the gas station that allegedly sold him Juul products when he was underage.

The lawsuit alleges Juul "sought to fill the void left by big tobacco by creating a new-age electronic cigarette." By using social media, the lawsuit alleges, "JUUL was able to easily target and manipulate youth by using advertisements designed to fulfill powerful psychological needs like popularity, peer acceptance, and a positive self-image -- the same techniques used by big tobacco in decades past."

In a statement, Antonio Romanucci, an attorney at Romanucci & Blandin, the firm that filed the lawsuit, said, "To put it mildly, Adam didn't stand a chance to avoid getting hooked on these toxic timebombs."

In response to the lawsuit, Ted Kwong, a spokesperson for Juul Labs, said the company is committed to eliminating combustible cigarettes, and that its product is intended to be a "viable alternative" for adult smokers.

"We have never marketed to youth and do not want any non-nicotine users to try our products. We have launched an aggressive action plan to combat underage use as it is antithetical to our mission," the statement said, including halting the sale of non-tobacco and non-menthol-based flavors in traditional retail stores, enhancing online age verification and shutting down its Facebook and Instagram accounts, among other steps.

"It was our hope that others in the category would self-impose similar restrictions to address youth usage," the statement said.

There really isn't enough vaping history to say what's going to happen'

The federal investigation into the link between vaping and severe lung illnesses is ongoing and has not identified a cause, but all reported cases have indicated the use of e-cigarette products and some patients have reported using e-cigarettes containing cannabinoid products, such as THC.

There are also separate investigations being conducted in separate states.

New York health officials said last week that extremely high levels of the chemical vitamin E acetate were found in nearly all cannabis-containing vaping products that were analyzed as part of the investigation. At least one vape product containing this chemical has been linked to each person who fell ill and submitted a product for testing in the state.

Laboratory tests conducted at the New York State Department of Health's Wadsworth Center in Albany showed "very high levels" of vitamin E acetate in the cannabis-containing samples, the state health department announced.

Vitamin E acetate is now "a key focus" of the state's investigation into the illnesses, the New York Department of Health said. Some of the products that have been found to contain vitamin E acetate are candy-flavored vapes.

Juul has maintained that its products are intended to convert adult smokers to what it described in the past as a less-harmful alternative. In other communications, the company says it cannot make claims its products are safer, in line with FDA regulations.

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Another study, published in the journal Radiology in August, foud that vaping temporarily impacts blood vessel function in healthy people. Using MRI scans, it found, for example, changes in blood flow within the femoral artery in the leg after just one use. The researchers couldn't determine which chemical might be responsible for the changes they observed.

There are many questions that remain to be answered, according to Amesbury.

"We're very early in the stages of finding out what problems may come up from vaping," he said. "We're finding these acute, severe illnesses now, but there really isn't enough vaping history to say what's going to happen 10, 20, 30 years down the road."