Researchers find smoking marijuana presents bronchital risks, but less chance of lung cancer compared to cigarettes
By Sarah Khan
Oct. 6, 2010 1:57 a.m.
The act of smoking a marijuana joint is similar to puffing on a cigarette.
Both substances have been known and used for hundreds of years, and their potential risks have long been hot topics of debate among lawmakers.
Yet the jury is still out on whether marijuana shares similar health risks as cigarette smoking.
For this reason, UCLA researchers like Dr. Donald Tashkin are looking to compare the effects of marijuana and cigarettes on the lungs.
When Tashkin, a professor in the David Geffen School of Medicine, started studying marijuana 30 years ago, he expected to find heavy marijuana smokers suffering from many of the same diseases that chronic cigarette smokers suffer from, such as lung cancer and emphysema.
In many ways, this hypothesis was a natural one to make.
“Marijuana leaves contain the same carcinogens as tobacco,” said Dr. Michael Roth, a medical school professor who is studying marijuana’s effect on the lungs and immune system. “So when you smoke those, you’re smoking the same carcinogens as if you were smoking tobacco.”
Marijuana smokers also hold the smoke in their lungs for a longer period of time to experience a “high,” Tashkin said.
Smoking like this can deposit four times as much carcinogenic tar in the lungs, he added.
Research has shown that both heavy marijuana and cigarette smokers are at a greater risk for developing chronic bronchitis, a constant inflammation of the large airways. This condition often leads to coughing, wheezing and difficulty breathing, Tashkin said.
In his research, Tashkin also came across documented cases of marijuana smokers suffering from various head and neck cancers.
Although these reports were not as reliable as controlled academic studies, marijuana’s chemical content seemingly pointed to an increased risk of cancer and chronic obstructive pulmonary disease, which is associated with heavy cigarette smoking.
But Tashkin’s study gave researchers some unex pected results.
When Tashkin took lung cell samples from marijuana smokers, he found no link between heavy marijuana smoking and an increased risk of lung cancer or emphysema.
Lung function tests showed that the lungs of marijuana smokers worked just as well as those of nonsmokers, he said.
In addition, Tashkin led a six-year study documenting all cases of head and neck cancers in Los Angeles.
Researchers determined risk factors for head and neck cancers based on the subjects’ family histories, diet, lifestyle and smoking habits, he said. But the results did not label marijuana as a risk factor for the cancers.
People who smoked more than two packs of cigarettes a day were 20 times as likely to develop the cancer, according to the study.
These counterintuitive results may be attributable to delta-9-tetrahydrocannabinol, or THC ““ the chemical in marijuana leaves that gives smokers of the plant a “high,” Tashkin said.
The chemical prevents lung cell inflammation, which in turn lowers the risk of developing a cancerous tumor, Roth said.
He added that cigarettes don’t have this property.
Researchers are looking at the chemical’s anti-tumoral properties not only in the lungs but in other parts of the body, such as the heart, blood vessels, immune system and metabolism, Roth said.
“There is a lot of interest in seeing if (the chemical’s) effects on the body holds the possibility for designing new medications and drugs,” Roth said.
But the amount of research done on marijuana is small compared to what has been studied in cigarettes, Roth said.
“Until you study something, you don’t really know what’s going on,” Roth said. “The most important thing is not to assume that (marijuana) doesn’t cause any (harmful) effects.”
