Growing Evidence Of Marijuana Smoke’s Potential Dangers.

In a finding that challenges the increasingly popular belief that smoking marijuana is less harmful to health than smoking tobacco, researchers in Canada are reporting that smoking marijuana, like smoking tobacco, has toxic effects on cells.

Rebecca Maertens and colleagues note that people often view marijuana as a “natural” product and less harmful than tobacco. As public attitudes toward marijuana change and legal restrictions ease in some countries, use of marijuana is increasing.

Scientists know that marijuana smoke has adverse effects on the lungs. However, there is little knowledge about marijuana’s potential to cause lung cancer due to the difficulty in identifying and studying people who have smoked only marijuana.

The new study begins to address that question by comparing marijuana smoke vs. tobacco smoke in terms of toxicity to cells and to DNA. Scientists exposed cultured animal cells and bacteria to condensed smoke samples from both marijuana and tobacco. There were distinct differences in the degree and type of toxicity elicited by marijuana and cigarette smoke.

Marijuana smoke caused significantly more damage to cells and DNA than tobacco smoke, the researchers note. However, tobacco smoke caused chromosome damage while marijuana did not.

Source: :

Dietary selenium fails to influence cigarette smoke-induced lung tumorigenesis in A/J mice.

Higher dietary sodium selenite did not inhibit the induction of lung tumors. • Higher dietary selenium increased selenium and GPx protein levels in the lung. • Dietary selenium did not affect lung SOD levels.


The goal of the study was to determine if dietary selenium inhibited the induction of lung tumorigenesis by cigarette smoke in A/J mice. Purified diets containing 0.15, 0.5, or 2.0mg/kg selenium in the form of sodium selenite were fed to female A/J mice. Half of the mice in each dietary group were exposed to cigarette smoke 6h/day, 5days/week for five months followed by a four month recovery period in ambient air, while the other half were used as controls. After the recovery period, the mice were euthanized, and their lungs were removed for further analysis. Mice exposed to smoke had a higher tumor incidence and a higher tumor multiplicity, whereas dietary Se did not affect either the tumor incidence or tumor multiplicity. An increase in dietary selenium led to increased levels of selenium in the lung as well as GPx protein levels, but dietary Se did not affect lung SOD protein levels. In conclusion, these data confirm the carcinogenic activity of cigarette smoke in mice but show that dietary Se provided as sodium selenite does not affect smoke-induced carcinogenesis in this model.

Source: cancer letters