Tests Reveal Colorado Weed More Potent, Has More Contaminants Than 30 Years Ago

By Paul Gaita 03/24/15

The THC levels in pot being sold today are far more potent than three decades ago.

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Tests on the potency of marijuana being legally sold in Colorado revealed that current strains are far more powerful than the weed that was available a quarter-century or more ago. The results of the tests, conducted by the Denver-based laboratory Charas Scientific, were announced on Monday, March 23 at the 249th national meeting of the American Chemical Society (ACS).

According to their findings, the average potency for marijuana is approximately 20% to 30% tetrahydrocannabinol (THC), the psychoactive compound in the plant that creates the feeling of being high. That potency value is markedly higher than marijuana sold in the 1980s, which federal officials cited as being about 4% THC, or even three years ago, when THC concentration in confiscated marijuana hovered around 15%.

THC levels can be altered by growers through crossbreeding different strains to create a more potent new hybrid. In doing so, Charas Scientific reported that the marijuana samples they tested also had very low levels of cannabidiol (CBD), which has been cited as possessing therapeutic value for conditions ranging from schizophrenia and seizures to Alzheimer’s disease.

CBS News medical contributor Dr. David Agus expressed surprise at this revelation, adding that because of the possible medical advantages in marijuana, “we have to standardize and put more CBD in [marijuana strains].” However, marijuana chemistry expert Anthony Fabrizio of California’s Terra Tech Corp, noted that strains with even lower CBD levels still possess some medicinal value. “Cannabinoids are a single component of what is active in the medicine properties of marijuana plants,” he stated.

A more disconcerting finding in the report was the presence of various contaminants in the samples, including fungi, bacterial growth, and traces of heavy metals and butane, which are often used to create marijuana extracts. The findings echoed the results of a similar test from a Colorado lab in 2014, which found mold, E.coli, and salmonella in marijuana samples.

Charas Scientific founder and director of research Andy LaFrate, Ph.D., said that while microbial growth in a natural product like marijuana is a normal occurrence, acceptable levels of contaminants have not been set in Colorado, where standards are still being established. “The questions become: What’s a safe threshold?” said LaFrate. “And which contaminants do we need to be more concerned about?” 

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Paul Gaita lives in Los Angeles. He has contributed to the Los Angeles Times, Variety, LA Weekly, Amazon.com and The Los Angeles Beat, among many other publications and websites.