On Jan. 1, 2017, Colorado will raise its state-regulated limit on the residual levels of volatile solvents allowed in cannabis concentrates. It’s a little-noticed rule change that involves dramatically increased levels of allowable solvents. Among the changes:

A redlined version of Colorado state testing regulations highlights the changes to residual solvent limits in the state, set to take effect Jan. 1. (Colorado Department of Revenue)A redlined version of Colorado state testing regulations highlights the changes to residual solvent limits in the state, set to take effect Jan. 1. Click to expand image. (Colorado Department of Revenue)

“Consumers are going to feel like they might taste it.”

Mike Van Dyke, Colorado Department of Public Health and Environment

On the surface, these are staggering increases in chemicals that, at some levels, have been associated with nausea, irregular heartbeat, increased risk of cancer, and even death. Regulators, testing laboratory operators, and industry members in other states have expressed surprise at the changes, which will apply to both adult-use and medical markets. Mike Van Dyke, chief of the Environmental Epidemiology, Occupational Health, and Toxicology Branch at the Colorado Department of Public Health and Environment (CDPHE), which recommended the new limit, acknowledged that concentrates capable of clearing the regulatory hurdles could be noticeably different from what’s currently allowed.

“Consumers are going to feel like they might taste it,” he said of new allowed butane levels. “They might smell it.”

“I’m surprised nobody else has even actually been interested in this,” he told me in an interview last week.


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There are a few things CDPHE’s Van Dyke wants to make clear about the new rules. Here is one: “This change was not a result of any industry pressure.”

The increase didn’t come at the behest of lobbyists, he told Leafly. “In fact, in the workgroups, if we heard anything from industry, I think we heard the other side, that these were too high,” he said, “which is an uncommon place to be.”

What is going on?

The justification for the change, according to Van Dyke, is that the new limits truly follow the best currently available medical and scientific guidance. “This was a re-evaluation based on trying to make things health-based,” he explained. “These numbers came from the international harmonized guidelines for residual solvents in pharmaceuticals.”

Van Dyke is referring to a published scientific article he cited in a July letter to Jim Burack, director of the Colorado Department of Revenue’s enforcement division, which is in charge of enforcing the new standards. Van Dyke provided the letter and spoke at length to Leafly about the coming change.

“Will these numbers stand the test of time? I don’t know,” he said. “We’re open to new data that comes out, but our goal is to make sure that we maintain, the best we can, the best evidence-based regulations for health.”


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The agency is trying to do precisely what it’s been asked, Van Dyke said. Legislation passed this year, House Bill 16-1261, put the CDPHE in charge of recommending testing standards “based on medical reports and published scientific literature.”

When the Colorado Department of Revenue set the previous limits, in the wake of Amendment 64’s passage, it was a “fast and furious” process, Van Dyke said. “There were times you came up with numbers because that’s what you came up with at the time.” Despite the eye-popping increases, he said the new limits adhere more strictly to the latest available evidence in scientific research.

Amy Phung/LeaflyClick to expand image. (Amy Phung/Leafly)

Comparison shopping

Other jurisdictions have set residual solvent limits lower than Colorado. Berkeley, Calif., limits total combined residual solvents at 400 ppm. Oregon, on the other hand, set standards similar to Colorado, but with more solvents identified. In a report explaining its own rulemaking process, the Oregon Health Authority cited the same international pharmaceutical standards as Van Dyke’s letter did. Washington, which was initially silent on residual solvents levels, has considered limits as low as 500 ppm butane and 0.1 ppm benzene, but regulators are currently proposing the state adopt higher limits that match those now embraced by Oregon and Colorado. After a public comment period, the new Washington limits are set to take effect in late February.

“Frankly, we’re not saying that extracted marijuana products should have 5,000 ppm of butane in them,” Van Dyke, in Colorado, said. “What we’re saying is 5,000 is a health-based limit.”

But didn’t he just acknowledge the possibility of literally smelling butane in BHO approved by the state for medical patients?

“I think there may be a lot of market drivers that push those numbers lower,” Van Dyke acknowledged, and smell could certainly be one of them. But, he repeated, “it’s not from a health perspective that those numbers should be lower.”

But are residual solvents merely a matter of product taste and quality, or is scientific research still too limited to inspire consumer confidence? It may be a little bit of both.