The ‘news’ story, which several other mainstream media outlets are also promoting, is based on a new British study assessing the effects of, ahem, “calf thymus DNA treated in vitro (in a Petri dish) … with the smoke generated from 1, 5, and 10 cannabis cigarettes.”

Yes, really.

So how did Fox “We report, you decide” News summarize this non-story? Let’s take a look.

What Fox News reported: “Smoking marijuana not only gets you high, but it also alters your DNA.”

What the study actually said: “[T]hese results provide evidence for the DNA damaging potential of cannabis smoke, implying that the consumption of cannabis cigarettes may be detrimental to human health with the possibility to initiate cancer development.”

What Fox News reported: “There have been many studies on the toxicity of tobacco smoke,” researcher Rajinder Singh said in a news release. “Cannabis in contrast has not been so well studied.”

What Fox News didn’t report: From the March 2009 issue of the scientific journal Medicinal Research Reviews, “Research on the chemistry and pharmacology of cannabinoids and endocannabinoids has reached enormous proportions. … [A]pproximately 15,000 articles on Cannabis sativa L. and cannabinoids and over 2,000 articles on endocannabinoids (are available in the scientific literature).”

What Fox News reported: “Singh said cannabis smoke contains 400 compounds including 60 cannabinoids. It also contains 50 percent more carcinogenic polycyclic aromatic hydrocarbons including naphthalene, benzanthracene, and benzopyrene, than tobacco smoke, Singh added.”

What Fox News didn’t report: From the November 2007 issue of the scientific journal Clinical Pharmacology & Therapeutics, “Vaporization of marijuana does not result in exposure to combustion gases, … and [was] preferred by most subjects compared to marijuana cigarettes. … The Volcano [vaporizer] device is an effective and apparently safe vehicle for THC delivery, and warrants further investigation in clinical trials of cannabis for medical purposes.”

What Fox News reported: “‘The smoking of 3-4 cannabis cigarettes a day is associated with the same degree of damage to bronchial mucus membranes as 20 or more tobacco cigarettes a day,’ the team wrote in the journal.”

Except for the fact that it isn’t. In fact, here’s what Donald Tashkin of the UCLA David Geffen School of Medicine, Division of Pulmonary and Critical Care Medicine, had to say about the subject earlier this month in an interview with the McClatchy newspaper chain. (**Note: Dr. Tashkin has performed US-government sponsored studies of marijuana and lung function for over 30 years and is considered to be the United States’ — if not the world’s — foremost expert on the subject.)

“What we found instead was no association (between marijuana smoking and cancer) and even a suggestion of some protective (anti-cancer) effect. … Early on, when our research appeared as if there would be a negative impact on lung health, I was opposed to legalization because I thought it would lead to increased use and that would lead to increased health effects. But at this point, I’d be in favor of legalization (of marijuana). I wouldn’t encourage anybody to smoke any substances. But I don’t think it should be stigmatized as an illegal substance. Tobacco smoking causes far more harm. And in terms of an intoxicant, alcohol causes far more harm.”

Just for the record, in 2006, Tashkin led the largest population case-control study (yes, Dr. Tashkin actually performed research on humans, not ‘calf thymus DNA’) ever to assess the use of marijuana and lung cancer risk. The study, which included more than 2,200 subjects (1,212 cases and 1,040 controls), reported that marijuana smoking was not positively associated with cancers of the lung or upper aerodigestive tract – even among individuals who reported smoking more than 22,000 joints during their lifetime.

Let the folks at Fox put that in their pipe and smoke it.