Teen vaper: 'I would have died that night'

(SOUNDBITE) (English) EX-VAPER, SIMAH HERMAN, SAYING:

"Two days I would have died. If I didn't go to the hospital that Thursday, I would have died in my bed that night, 100 percent. It's just not worth it."

That's 18-year-old Simah Herman, and this is Herman just last month: on life support at UCLA Medical Center, the result of vaping, as Herman's mother explains.

(SOUNDBITE) (English) SIMAH HERMAN'S MOTHER, STACY HERMAN, SAYING:

"She had 8 IVs in her body, tons and tons, arms and legs, all over, lines going in, 8 different lines with all the different medications and they still couldn't kill off what was poisoning her insides. They still didn't know - not until she was released did they say, 'We ruled everything out and it looks like it must be from this vaping."

The U.S. investigation into hundreds of cases of life-threatening lung illnesses related to vaping has turned up a curious abnormality: Many of the victims had pockets of oil clogging up cells responsible for removing impurities in the lungs.

Where vaping's toxic oil comes from is still unclear.

One possibility: The oil deposits are residue from inhaling vaping oils, such as those containing the marijuana ingredient tetrahydrocannabinol - or THC - or vitamin E acetate.

Dr. Robert Tarran of the University of North Carolina School of Medicine is among the researchers examining lung cells from patients similar to Herman.

(SOUNDBITE) (English) PHYSIOLOGIST AND VAPING EXPERT ROBERT TARRAN, SAYING:

"One of the things we found there is a wide variety some liquids are more toxic than others and we found there is a correlation the more flavors in a liquid the more likely it was to be toxic. But there's also an incredible diversity of flavors. So in 150 e-liquids we found about 200 different chemical constituents. And so really the flavors e-liquid really are all over the map."

Herman's mother had it explained to her this way from Simah's doctor at UCLA.

(SOUNDBITE) (English) SIMAH HERMAN'S MOTHER, STACY HERMAN, SAYING:

"She said your lungs don't want to be wet. This vape is a vaporizer, it's inhaling liquid into your lungs so they know that's not good already so the vape mechanism is the bad part. Then we know oil in your lungs is bad because you're heating it up. It's like you're cooking french fries, you cook them in the pot, you make your french fries in the hot oil and that oil that's left, you leave it in the fridge, that oil is going to congeal and it's going to turn into a solid fat. Well, that solid fat coating your lungs makes it really hard to breathe."

Investigators at the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration have not ruled out conventional nicotine liquids as the cause.

The CDC says youth and young adults should not use e-cigarettes.

Herman was in such dire straits she started an anti-vaping campaign from her hospital bed - posting photos of herself on Snapchat.

(SOUNDBITE) (English) EX-VAPER, SIMAH HERMAN, SAYING:

"At any point, your lungs can start failing on you and you have no idea it's happening until the point where you can't take your last breath."

Leading makers of nicotine e-cigarettes, including Juul Labs, British American Tobacco and Imperial Brands said last week their products did not contain Vitamin E compounds.

The outbreak in vaping-related illnesses has killed 8 people in the U.S. and sickened 530 people so far.

On Friday Walmart announced it will no longer sell e-cigarettes.