What are vaping-associated illnesses and why are doctors concerned?

Health officials in the United Stateshave flagged hundreds of serious respiratory illnesses among people who use e-cigarettes, including six deaths. For doctors in Canada, the sudden illness adds to their concerns that people wrongly assume vaping products are harmless.

E-cigarettes heat liquid that usually contains nicotine into a vapour drawn into the lungs.

What's in e-liquids?

E-cigarette liquids includesolvents such aspropylene glycol and vegetable glycerin to dissolve nicotine or cannabis compounds.

Under the federal Tobacco and Vaping Products Act, promotion of flavours like candy or "strawberry cheesecake"that may be appealing to young peopleare restricted.

Federal authorities consider the ingredients safe to consume as food. But our lungs are only equipped to inhale clean air.

In the latest cases in the U.S., federal and state officials are investigating how and why inhaling oily droplets while vaping triggered pneumonia in a few people.

"Our lungs are never meant to have fat in it," said Dr. Dilini Vethanayagam, a respirologist at the University of Alberta.

"When we inhale something that we shouldn't, like lipids [fats] that don't clear well after it's inhaled, it kind of lines the alveolar sacs that are meant for respiration," Vethanayagam said. "Over time if you're vaping on a daily, weekly basis, it can accumulate further. So death is just one aspect of the tip of the iceberg."

What is the illness under investigation in the U.S.?

Patients have gone to hospital with cough, chest pain, shortness of breath, fatigue and vomiting.

Many of the cases in the U.S. haveinvolved severe, life-threatening illnesses in previously healthy people. Many neededoxygen, and some needed ventilation to recover.

What's going on in people sickened in the U.S.?

At first, the medical community thought the pneumonia was caused by legionella or another microbe. But these tests all came back negative.

"It was only later that people appreciated that this was actually a chemical insult to the lungs that was creating this illness," said Dr. Richard Stanwick, chief medical health officer for Island Health in Victoria.

Vethanayagam and her co-authors at McMaster University in Hamilton reported a woman who had "lipoid pneumonia" after vaping cannabis in 2000.

Doctors have also reported this non-infectious type of pneumonia from inhaling or aspirating other oils, including petroleum jelly smeared around kids' noses.

No single device, ingredient,additive or pathway to illness has been identified in the U.S. investigation.

Most of the patients say they vaped products containing tetrahydrocannabinol(THC) from cannabis, which gives users a high. Others said they vaped only nicotine, and still others said they vaped both THC and nicotine.

Greater awareness likely also prompted more clinicians in the U.S. to report suspected cases, leading the count to jump. As of Sept. 11, the CDCreported380confirmed and probable casesacross 36states and the U.S. Virgin Islands, up from 193 in 22 states nearly threeweeks ago.

"This is a medical mystery that is really being aggressively pursued," Stanwick said.

Health Canada said Thursday there are no confirmed or suspected cases of thepulmonary illnesses in this country.

What other health problems are associated with vaping?

For starters, nicotine dependence.

"Any tobacco product use, including e-cigarettes, is unsafe for youth. Nicotine can harm the developing adolescent brain," Dr. Robert Redfield, director of the U.S. Centers for Disease Control and Prevention, said in a statement.

Nicotine is powerfully addictive, said Dr. Theo Moraes, a staff respirologist at the Hospital for Sick Children in Toronto.

Moraes said while someone starting cigarettes may cough, vaping doesn't have the same "noxious feedback" for people to stop.

"You can deliver a fair chunk of nicotine in a pod, sometimes the equivalent of a pack or two packs of cigarettes and so for a young person you can get a fair amount of nicotine and quickly become addicted to it."

Nicotine also harms the cilia in the lungs that clear mucus, which is important for the lungs to function properly, Moraes said.

Tobacco smoke is associated with 50 or more carcinogens compounds that cause cancer. Heating vapour also produces cancer-causing chemicals such as benzene, saidStanwick.

The CDC said vaping solutions contain a number of chemicals that could also pose risks, such as ultrafine particles,diacetyl , a flavouring chemical that has been linked to lung disease, heavy metals and volatile organic compounds.

Some studies suggest vaping can also affect the heart.

"The advice is to find a safer way if you are dependent on psychoactive substances, whether it's THC or nicotine, to find a safer way of ingesting the product until we can at least sort this out," Stanwick said.

As a pediatrician, Stanwick also urged federal and provincial governments to regulate vaping devices the same way as tobacco in terms of restrictions on promotion and marketing including elimination of point-of-sale ads and enforcement against underage sales.