Colorado Adopts New Marijuana Mold and Potency Testing Rules

A common mold found in marijuana flower, aspergillus can be inhaled through smoke.
A common mold found in marijuana flower, aspergillus can be inhaled through smoke. Lindsey Bartlett
Colorado marijuana regulators have beefed up the state's mold and potency testing requirements.

A July 1 memo from the state Marijuana Enforcement Division reminded licensed marijuana business owners that testing for aspergillus is now included in the state's mold and yeast test requirements, while potency testing has expanded into more forms of THC. The new rules took effect that day.

Commercial marijuana products are currently tested for various pesticides, molds and yeasts, heavy metals, solvents and other contaminants, as well as cannabinoid potency. Part of an extensive regulatory update in 2021, the new standards were based on recommendations from a science and policy committee overseen by the MED and Colorado Department of Public Health and Environment.

A common mold found indoors, outdoors and in marijuana samples, aspergillus can be inhaled through smoke and makes regular appearances in marijuana flower studies. Nearly a dozen states with commercial pot currently have aspergillus testing mandates, according to Jill Ellsworth, CEO of marijuana remediation company Willow Industries.

"The decision made by the [MED] to add aspergillus to its microbial testing requirements is a big step for the Colorado market. This mold is common and presents a serious risk to facilities, workers and consumers," Ellsworth says. "This change shows that the industry is continuing to understand the risks of microbial contamination, and hints at the standardization of testing regulations to come."

Marijuana samples found with aspergillus will have to undergo plant remediation or retesting, or be destroyed.

The new potency tests were partially designed to help inform consumers about the total amount of THC in the products they purchase at dispensaries, according to the MED memo.

Colorado marijuana testing laboratories measure several cannabinoids in medical and recreational products, including CBD and THC, but the THC testing previously only looked for for Delta-9 THC, the most common form of THC found naturally in cannabis plants. A federal loophole created by hemp's federal legalization in 2018 has since spurred the evolution of synthetic and modified isomers of THC derived from hemp such as Delta-8 and Delta-10 THC, both of which can have similar intoxicating effects to Delta-9.

Modified hemp cannabinoids have created a burgeoning market for gummies and vaporizers that can provide intoxicating effects similar to those of marijuana products sold at dispensaries. These hemp products are offered online and at more traditional retailers such as gas stations or smoke shops.

The MED banned hemp-derived cannabinoids from marijuana dispensary products in 2021, a few months before adopting the new potency-testing standards. According to the MED memo, Colorado marijuana products will now be tested for Delta-8, Delta-10 and Exo-THC, another intoxicating form of THC. Although the forms of THC aren't banned from commercial pot products, they must be produced within the state's registered marijuana framework, and not from industrial hemp.

The Colorado Legislature passed a law earlier this year creating a state committee that will study and recommend new regulations surrounding products made with modified cannabinoids.
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Thomas Mitchell has written about all things cannabis for Westword since 2014, covering sports, real estate and general news along the way for publications such as the Arizona Republic, Inman and Fox Sports. He's currently the cannabis editor for
Contact: Thomas Mitchell