A man smokes marijuana during a gathering to welcome back marijuana advocate Marc Emery in Windsor, Ontario
A man smokes marijuana outside Windsor City Hall during a gathering to welcome back marijuana advocate Marc Emery (not seen) who is released from an American prison for selling marijuana seeds in the U.S., in Windsor, Ontario August 12, 2014. Emery jailed for five years in a U.S. federal prison for shipping marijuana seeds across the border returned to his homeland on Tuesday, as laws regulating the drug in both countries have slowly been relaxed. REUTERS/Rebecca Cook

Even if their group has denied to give their participation to a government campaign, doctors in Canada remain against smoking marijuana, be it for medicinal purposes or not.

Canadian doctors stood on their ground that smoking marijuana is bad for the health. "Smoking one joint is already equivalent to smoking 10 cigarettes," Dr Deborah Hellyer, a respirologist from Windsor, Ontario, said.

On Wednesday, delegates who attended the Canadian Medical Association's general council meeting had formally voted their opposition to the smoking of any plant substance.

Dr. Louis Hugo Francescutti, CMA president, citing a 2008 study, said a man's lungs has a "natural cleaning and repair system and traps cancer-causing chemicals" in the airways. Smoking generally impedes these functions. And all the more once a person smokes marijuana.

Marijuana smoke, Francescutti said, while it has the same chemicals found in tobacco smoke, its percentage are however substantially in higher levels than the latter.

Read: Canada's Anti-Marijuana Campaign Thumbed Down by Very Own Doctors

An example is the level of ammonia which was found to be twenty-times higher in marijuana smoke than in tobacco smoke.

"I firmly believe physicians are here to promote health and ... we should be outspoken on this," Hellyer said.

John Ludwig, a physician in Omemee, Ontario, said the Canadian doctors' recent vote should not be used by politicians as a sneaky way of opposing medical marijuana because their group had long been opposed to any form of smoking.

"We shouldn't be supporting something harmful, and smoking is harmful," Atul Kapur, president of Physicians for a Smoke-Free Canada, said, noting good evidence on the use of marijuana for medical purposes has yet to be identified and established.

Two-thirds of delegates present during that CMA general council meeting approved of the motion opposing smoking all plant materials.

The CMA is composed of Canada's 80,000 doctors.