Three years ago, an American Indian tribe in Wisconsin watched in horror as their “industrial hemp” crop was bulldozed after a federal agent swabbed a plant and alleged it was marijuana.
The field test was incapable of determining if the plants were marijuana or quasi-legal hemp, and experts are bracing for more confusion with the new national legalization of hemp farming after nearly five decades of prohibition.
Hemp is a nonintoxicating form of cannabis used for rope, clothing, and food. It was legalized with last month’s farm bill, but questions remain about enforcing a 0.3 percent tetrahydrocannabinol, or THC, limit that legally distinguishes hemp from marijuana.
“I do expect there to be challenges,” said Jeffrey Raber, a chemist whose Werc Shop lab has operated in Washington and California. “Even though most labs could get a number that low, how tightly clustered these results are in terms of precision — repeatability — is more a matter of proper sampling and managing a highly variable agricultural product.”
Testing cannabis is surprisingly difficult, requiring expensive machinery, rigorous calibration, and consistent sample collection. Plant genetics and growing conditions also impact THC readouts.
“One year, [a crop] could be fine, the next may be problematic as there isn’t much room for variability,” said Raber, who also serves as executive director of the Association of Commercial Cannabis Labs. “How the sampling is done, how many replicates are performed, and what is considered 0.3 percent — [whether there is allowable] variance or a hard upper limit — will all dictate how much trouble is seen.”
Heather Despres, former lab director of Colorado’s CannLabs, said there can be about 8 to 12 percent variation in THC between the top and bottom of cannabis plants, with higher concentrations at the top.
Separately, variation of 10 percent from lab to lab is considered acceptable for a known sample, said Ken Groggel, director of proficiency testing at Emerald Scientific, which works with cannabis labs to improve accuracy.
“Equipment maintenance, calibration, the certified reference materials used for calibration — there are so many factors at play,” Groggel said. “It’s almost empirically impossible to hone in and control all of the variables.”
Hemp’s legalization follows a more limited set of state “pilot programs” that opened under the 2014 farm bill, bringing the crop back to the U.S. after decades of association with marijuana.
“Physically the plants all look the same, just chemically there are major differences,” said Despres, who now works to establish industry standards as director of the Patient Focused Certification, or PFC, program of the pro-medical marijuana Americans for Safe Access.
Despres advocates a national seed-certification system to confirm plants won’t exceed 0.3 percent THC, saying Canada offers a good model. For state pilot programs, authorities had to import seeds from countries where THC limits vary.
While mistaken busts are possible with flimsy test results, Despres said farmers may also grow marijuana and try to pass it off as hemp — a notion disputed by former U.S. Attorney for North Dakota Timothy Purdon, who has worked with the hemp industry and the raided tribe.
Purdon said only the “dumbest criminal” would register with state authorities as required. He noted the farm bill requires states to develop testing guidelines for enforcement.
Testing cannabis evolved recently. After Colorado legalized recreational pot in 2012, authorities used gas chromatography, but heat was found to give inaccurate potency results. Labs now use high performance liquid chromatography, or HPLC, machines costing more than $30,000, or ultra performance liquid chromatography, or UPLC, machines that cost more than $100,000.
Luke Mason, co-owner of Colorado’s Aurum Labs, said labs should be capable of accurately judging THC levels, but that simultaneously testing various compounds — such as THC and the emerging epilepsy treatment cannabidiol, or CBD — can be “troublesome and unreliable” due to machinery quirks.
Although some uncertainty remains, Groggel said he’s optimistic that the national cannabis-lab industry has moved past a bumpy post-2012 period characterized by allegedly disreputable and dishonest operators. Progress in states that allow recreational marijuana gives him confidence. “I think people are going to get on board fairly quickly,” he said.
