In California, the director of the National Organization for the Reform of Marijuana Laws, with help from a leading cannabis researcher in the Netherlands, did a similar trial with 10 top labs in the state. The results for a "same homogenized cannabis material" ranged from 4.16% THC to 14.3%, although seven of the labs had closer results, between 8.4% and 12.5%."
Having high potency is a money-maker. Having pesticides is not, and the industry as a whole has shown little interest in learning and disclosing what industrial chemicals, if any, people are drawing into their lungs.
Most labs charge separate fees for each test the customer wants: screening for THC and other active compounds, for biological contaminants, and for pesticides. Dispensaries always want the THC test.
The Werc Shop does the biological contaminant tests on half its samples and checks about 30% for pesticides. Steep Hill, the state's largest lab, tests about 65% of submitted samples for mold and microbes and only about 5% for pesticides.
Steep Hill's president, David Lampach, says it's too costly to routinely test for the hundreds of possible pesticides and easier to work with farmers to ensure they're never used.
At Halent, Land says "purity is more important than potency," and he performs only an all-inclusive screening for more than 30 pesticides as well as molds, fungi and mycotoxins.
But this tests only the most common pesticides and, with no federal tolerance guidelines for marijuana — or tobacco, as a potential reference point — the labs are left to come up with their own thresholds for what is acceptable.
In October 2009, Los Angeles police officers bought marijuana at nine dispensaries and had it tested by the Food and Drug Administration.
"They came back with a number of different pesticides," said William W. Carter, the chief deputy city attorney. "Half the samples were contaminated."
His office successfully shut down one store, the Hemp Factory in Eagle Rock; he said a sample from there contained the pesticide Bifenthrin at a level 170 times greater than the federal tolerance guidelines set for herbs and spices.
City Atty. Carmen Trutanich used this to issue depict the dispensary owners as callous criminals, not caregivers. At a press conference, he sprayed a can of Raid and asked, "Would you eat a salad with that on it?"
Ironically, Trutanich's push for testing — culminating in a requirement in the medical marijuana ordinance, passed in 2010 but still not enforced — launched a new sector in the industry he's expressed so much loathing for.
"When L.A. issued the ordinance that it had to be tested, labs popped up everywhere," said Paula Morris, scientific project manager of the short-lived Medea Labs in Hollywood. "There were a lot of people getting involved who had no science background."
In the often fractious industry, many have qualms about mandatory testing and say the contamination threat is overstated.
"With no scientific standardization, there's no meaning to these numbers," said Robert Jacob, director of Peace in Medicine Healing Center in Sonoma County. "I think it's more important to know our growers. We don't test organic tomatoes to see if they're organic. We create standards of growing."
But activists trying to broaden legalization are warming to the idea. "It's kind of the quid pro quo of legalization," said Ethan Nadelmann, director of the Drug Policy Alliance in New York City. "It's reasonable to expect that there is going to be labeling."
"The tide is turning," said Amir Daliri, director of government relations for the California Cannabis Assn., which is lobbying in Sacramento for statewide regulation, including testing. "You're getting dispensaries demanding growers bring tested medicine. Or patients are demanding it."
Doctors say testing is critical for patients with compromised immune systems. "Unless they're growing their own, I don't think they should buy medical cannabis if it hasn't been lab-analyzed," said Dr. Stacey Kerr, a family physician in Santa Rosa and a member of the Society of Cannabis Clinicians. "This is adding integrity to the medicine."
Kerr's group is keenly interested in a compound called cannabidiol, or CBD, which reportedly does not cause users to feel stoned, but has calming and pain-relieving effects that may help treat a range of problems, including arthritis, side effects of chemotherapy, asthma, sleep disorders and post-traumatic stress disorder.
The labs are helping identify strains high in CBD and low in THC, which a few leading dispensaries are encouraging cultivators to grow. Clinicians are studying the effects.
"The lab analysis is allowing patients to choose their medicine with knowledge of what is actually in it," Kerr said.
Raber opened The Werc Shop in April 2010 in a light industrial park east of Los Angeles in a city whose name he asked not be disclosed. There are no signs on the door.