By R. Scott Rappold
WebMD Health News
Reviewed by Brunilda Nazario, MD
March 24, 2015 -- Legal marijuana grown in Colorado is two to three times as potent as what was sold on the black market 30 years ago, according to test results released this week at a scientific meeting in Denver.
But it's the unexpected contents of Colorado's recreational marijuana that surprised researchers. Scientists found butane, heavy metals, and fungus in some samples.
"It's pretty startling just how dirty a lot of this stuff is," said Andy LaFrate, president and director of research at Charas Scientific, in a news release. "You'll see a marijuana bud that looks beautiful. And then we run it through a biological assay and we see that it's covered in fungi."
LaFrate shared the findings at a meeting of the American Chemical Society.
What's in Colorado's Recreational Pot?
Colorado voters legalized recreational marijuana in 2012, with the first legal sales of cannabis in the U.S. in eight decades beginning in 2014.
Mandatory testing for potency began in May 2014, followed by testing for consistency in July 2014, said Daria Serna, director of communications for the Colorado Department of Revenue.
Charas Scientific is one of eight labs certified by Colorado to test marijuana samples submitted by retailers.
Tests found that, despite the common belief that different strains produce different effects on the user, there was little chemical difference among marijuana samples. Researchers also found the levels of THC, the ingredient in marijuana that gives you a "high," ranged from 20% to 30 % percent, compared to the average of 10% 30 years ago. That's likely a result of years of breeding for higher THC potency many users prefer.
Another side effect of this breeding is that recreational marijuana has little or no CBD. That is an ingredient that has shown promise in treating seizures and other medical conditions.
The state has not yet begun requiring testing for contaminants, but some companies volunteered their products for such tests. Nothing was found to indicate a serious health risk. But the findings have raised questions about what should be tolerated in marijuana sold to the public and if such contaminants could be harmful.
Mary Meek, director of business development at Charas, said some marijuana samples had levels that are OK for grocery store produce. "But right now [the testing] is not in effect for marijuana, so you don't really know how dirty or clean your product is right now."
The possible health effects are unknown. While smoking a marijuana bud would conceivably kill the fungus, what if a user smells the marijuana first and breathes it in? Could it make him sick? For an industry just emerging from eight decades on the black market, there are few answers.
"The problem is it's not been tracked. You may just think you're getting a cold and it may look like allergies, when in reality it could be something else going on," Meek said.
Another problem is edible marijuana products. Meek said researchers have found E. coli -- though not a hazardous form -- and salmonella in some samples. Yet Denver is the only municipality in Colorado where health inspectors monitor edible marijuana products. Salmonella has also been found on marijuana buds, likely a result of organic growing techniques.
Still, Meek said that type of contamination is "rare."
"None of this is meant to be a scare campaign. That's not why we're here," she said. "We want to label your marijuana like we would label your liquor or your beer. You want to know your items have been tested and they're safe."
When contaminant testing becomes mandatory, pot stores will be required to test for molds, mildew, and filth; germs; and herbicides, pesticides, fungicides, and other harmful chemicals. They will also be required to include this information on labels, along with potency and the number of servings.
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