Marijuana smoke more harmful to lungs of tobacco smokers, US study finds

Marijuana smoke more harmful to lungs of tobacco smokers, US study finds
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Smoking marijuana while also being a tobacco smoker may result in increased damage to the respiratory system, a preliminary study published in Radiology, a journal of the Radiological Society of North America, has found.

The study compared chest scans of 56 people who smoke both tobacco and marijuana with lung scans of 33 heavy cigarette smokers who have been smoking for over 25 years. Scans from 57 non-smokers with no preexisting conditions were used as controls for the study.

"There’s a public perception that marijuana is safer than tobacco, and this study raises concern this may not be true," said lead study author Dr Giselle Revah, an assistant professor in the department of radiology at the University of Ottawa in Ontario.

Presence of emphysema

The authors assessed the presence of emphysema, a disease of the small airways that causes damage to the air sacs in the lungs, in the subjects of the study.

The 8% difference between those who smoke only tobacco and those who smoke both marijuana and tobacco may seem small, but the researches say it is significant.

"It suggests that marijuana has additional effects on the lungs than tobacco alone," Revah said. Although it was not clear from this study whether it is the combination or marijuana itself that causes the increased damage.

Another concern raised by the study was the age of the combination smokers, many of who were much younger than 50.

"These patients presumably had less lifetime exposure to smoke, except they’re even sicker than those who are heavy tobacco smokers and have been doing it longer," Revah said.

Revah did note the limitations of the study, least of all its size, but also the fact that it is unknown how much or using which methods the smokers of marijuana used. This gives clues for further research, for example, tobacco is typically smoked with a filter while weed is not.

Weed is inhaled longer than tobacco

"If you’re smoking an unfiltered joint, more particulates will reach the airways, get deposited and become irritants, which is why you see the mucus and the inflammation," she said. She added that tobacco smokers exhale quicker than marijuana smokers, as the latter often hold their breath to maximise the high.

"People usually have a longer breath hold and a higher puff volume, so they are holding in the larger volume of smoke for a longer period of time," she said. "That could lead to micro-trauma of those airspaces. These are all questions for future research."

Carol Boyd, founding Director of the Center for the Study of Drugs, Alcohol, Smoking & Health at the University of Michigan, had previously told CNN that she is often approached by parents and teenagers asking if vaping cannabis is "okay" and better than cigarettes.

"‘You are fooling yourself," is Boyd's answer.

"We know that inhaling hot tobacco/cannabis smoke into your lungs is unhealthy and can cause bronchitis or life-threatening breathing problems... You seem to believe that heating chemicals (including carcinogens) into a vapour and inhaling them is healthy? My answer is, ‘No, it is not a healthy behavior,"


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