Smoking pot can cause as much damage to cells and DNA as tobacco smoke, according to a group of Canadian researchers who are challenging the belief that marijuana is less harmful than cigarettes.
Rebecca Maertens, a researcher from Health Canada and co-author of the study, says many Canadians believe marijuana smoke is less toxic, and causes less damage than tobacco because pot is "natural."
Despite several experiments that show marijuana use to have adverse health effects, the prevalence of marijuana use in Canada has increased over the past decade, while the incidence of tobacco use has decreased.
Nearly one quarter of Canadians between the ages of 15 and 24 reported using marijuana in the previous 12 months according to 2006 Statistics Canada report — over 14 per cent of those said they used the drug on a daily basis.
The team behind this new study suggested that a lack of understanding about the dangers of marijuana plays a part in why youth are so cavalier about smoking it.
Neither marijuana nor the main psychoactive component of the plant, THC, has been shown to cause cancer.
There are, however, substances in marijuana that can be very harmful to a person, according to previous studies on the drug.
Negative health effects induced by smoking marijuana, such as chronic bronchitis, have been well documented, as have other negative health effects.
A 2007 study from New Zealand, for example, examined the effects of cannabis on lung capacity. The results suggested that marijuana smoke compromised lung efficiency between 2.5 and five times more than tobacco smoke.
Despite some knowledge surrounding marijuana's adverse effects on human lungs, researchers still have little knowledge about the plant's potential to cause lung cancer, Maertens said.
This is due in part to the difficulty researchers have had in identifying and following subjects who have smoked only marijuana, she said.
In this study, scientists exposed animal cells and bacteria separately to smoke from marijuana and tobacco plants.
Although marijuana smoke caused significantly more damage to cells and DNA than tobacco, according to the researchers, only tobacco smoke caused chromosome damage.
But marijuana advocate Marc Emery dismissed the study when contacted Wednesday night.
"Where is the proof of this DNA damage to Canadians? Are there mutations in the 15 million Canadians who have smoked marijuana in the last 45 years?" said publisher of Cannabis Culture Magazine in an e-mail to Canwest News Service.
"Cannabis consumption completely prevents Alzheimer's disease, cleans the lungs by shrinking tumours and breaks down necrotic cells and clears them out of the lungs. Millions of Canadians use cannabis for relief of symptoms of multiple sclerosis, Crohn's disease, epilepsy, chemotherapy, opiate medications, and numerous other ailments . . . This study is false and is in fact blatant lies once again from the least trustworthy source of health information in Canada — the lackeys at Health Canada."
Emery is on a cross-Canada farewell tour before he surrenders to U.S. narcotics officials to face charges in that country.
By Amy Minsky
November 23, 2009
The Windsor Star