Study: smoking marijuana found non-carcinogenic
Source: americanlivewire.com Author: staff Smoking marijuana does not appear to increase the risk of lung cancer or head-and-neck malignancies, even among heavy users, researchers reported here. “We expected that we would find that a history of heavy marijuana use, more than 500 to 1,000 uses, would increase the risk of cancer from several years to decades after exposure to marijuana, said Donald Tashkin, M.D., of the University of California in Los Angeles. But in fact, they reported at the American Thoracic Society meeting here, marijuana use was associated with cancer risk ratios below 1.0, indicating that a history of pot smoking had no effect on the risk for respiratory cancers. Studies have shown that marijuana contains many compounds that when burned, produce about 50% higher concentrations of some carcinogenic chemicals than tobacco cigarettes. In addition, heavy, habitual marijuana use can produce accelerated malignant change in lung explants, and evidence on bronchial biopsies of pre-malignant histopathologic and molecular changes, Dr. Tashkin said. The investigators had also previously shown that smoking one marijuana cigarette leads to the deposition in the lungs of four times as much tar as smoking a tobacco cigarette containing the same amount of plant material. Marijuana cigarettes are not filtered and are more loosely packed than tobacco, so there’s less filtration of the tar. In addition, pot smokers hold the smoke in their lungs about four times longer than tobacco smokers do, Dr. Tashkin pointed out. For the population-based case-control study, they identified cancer cases among people from [...]