Smoking marijuana may be more harmful to lungs than smoking cigarettes, study finds

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People who smoke marijuana were more likely to have certain types of lung
damage than people who smoked cigarettes, according to a new study that
reviewed lung scans of smokers. The researchers who led the study say
their findings suggest smoking marijuana may be more harmful than people
realize.

The Centers for Disease Control and Prevention estimates at least one-
fifth of Americans have tried marijuana at least once. With more states
legalizing the drug, it has become the most commonly used drug that is
still illegal at a federal level.

Some health effects, such as brain development issues, high blood
pressure, and increased risk of heart attacks and strokes, have been
studied. However, according to Dr. Albert Rizzo, lung doctor and chief
medical officer of the American Lung Association, “We don’t know the long-
term effects of marijuana as we do for the long-term effects of tobacco."

Researchers from Ottawa Hospital General in Canada compared approximately
150 lung scans from marijuana smokers, tobacco-only smokers and
nonsmokers. The study found that rates of emphysema, airway inflammation
and enlarged breast tissue were higher in marijuana than in tobacco
smokers.

The scans showed that 75% of the marijuana smokers had emphysema. Slightly
less than 70% of tobacco-only smokers had emphysema, while only 5% of
nonsmokers had it.

Emphysema, a form of chronic obstructive lung disease (COPD), is the third
leading cause of death in the U.S.

“There are air sacs in your lungs that are getting bigger than they
should. As they get bigger, they are less efficient than they should be
for gas exchange,” Rizzo said. The condition is caused by long-term
exposure to irritants such as smoke, leading to irreversible lung damage.

“Marijuana smokers had more emphysema, a disease that causes difficulty
breathing, than heavy tobacco smokers and nonsmokers,” said Dr. Giselle
Revah, study co-author and cardiothoracic radiologist.

Doctors say there are several reasons marijuana might cause more lung
damage than tobacco.

“Marijuana smokers breathe in more deeply, and they hold their breath
longer, before they exhale. You combine the irritating effect of longer
exposure and deeper inhalation of these toxins," Rizzo said.

Tobacco smoke is also filtered, but marijuana smoke is not. All of these
factors contribute to inflammation and irreversible damage, doctors say.

“Anything you inhale that could irritate the lungs would not be advisable,
so I would recommend they stop,” Rizzo said. However, he recognizes that
some users have medical necessity -- for those individuals, he recommends
a discussion with your doctor, who may be able to convert you to another,
safer form of the drug, such as an ingestible form.

“There is a public perception that marijuana is safe. This study signals
that marijuana could be more harmful than people realize,” Revah said.

Alicia Zellmer, M.D., and Joy Liu, M.D., are resident physicians in
Internal Medicine and members of the ABC News Medical Unit.

https://abcnews.go.com/Health/smoking-marijuana-harmful-lungs-smoking-
cigarettes-study-finds/story?id=93283206