Denver health officials Tuesday began inspecting and quarantining hundreds of marijuana products because their labels listed pesticides not approved for use on cannabis.

The move comes about six months after the city quarantined 100,000 plants at 11 grow facilities over concerns about pesticides.

Although pesticides are widely used on crops, their use on cannabis remains problematic because no safety standards exist. Marijuana is illegal under federal law, so the U.S. Environmental Protection Agency, which regulates pesticides, has never established any limits.

The Colorado Department of Agriculture, however, has created a list of pesticides it says can be used.

The holds at Mountain High Suckers on South Lipan Street and MMJ America on Arapahoe Street come after Denver’s Department of Environmental Health late Monday warned businesses that products with labels that reflect the use of unapproved pesticides should be removed from shelves and destroyed or returned to the manufacturer.

State law requires all marijuana product labels list the pesticides, contaminants, fungicides and herbicides that were used at any point of the production process, from germination to packaging.

Several hundred lozenges at Mountain High were quarantined after inspectors found their labels listed the pesticide spinosad, an insecticide that is slightly toxic to humans, according to Dan Rowland, spokesman for Denver’s office of marijuana policy.

An undisclosed amount of raw marijuana — shake and flower — at MMJ America also was put on hold over labels that disclosed spinosad, Rowland said.

Representatives of Mountain High and MMJ could not be reached for comment immediately. Mountain High’s website says it manufactures marijuana-infused edibles such as the lozenges and suckers. MMJ grows and sells its own marijuana.

An industry trade group said its members are “committed to complying with Denver’s new guidance.”

“Safety of our customers and employees is a top concern for our members,” said Mike Elliott, executive director of the Marijuana Industry Group. “This process demonstrates yet again that the regulated industry is always safer than the black market.”

State law says “it is unlawful for someone to use pesticides in a manner inconsistent with labeling directions or requirements,” said Mitch Yergert, director of the Colorado Department of Agriculture’s division of plant industry.

However, some labels are so broadly written that the state has decided the pesticide can be used on marijuana because it doesn’t violate the label warnings.

Denver health inspectors will continue to make spot checks of marijuana businesses and respond to referrals, officials said.

Inspectors who find products that appear to contain an unapproved pesticide will file a complaint to have them tested, Rowland said.

“They’ll be removed from shelves contingent on the test results,” Rowland said, “and a product recall could be issued.”

Inspectors also will investigate the source of plants that had the pesticide to determine whether a supplier sold to other manufacturers, Rowland said. They also will determine whether a manufacturer, such as Mountain High, sold its products to other retailers.

Although product labels might reflect pesticides not allowed for use on marijuana, it’s unclear how much pesticide residue actually remains on the pot or on infused products. And a different state law requiring businesses to test for them has not yet been enforced.

That issue surfaced after Denver quarantined plants in March and April.

“While everyone wants safe marijuana, Denver has no science to show the presence of residual amounts of pesticides are a danger to public health,” said attorney Sean McAllister, who sued the city over the holds last spring.

Nearly every test CDA did on the quarantined plants found some level of a banned pesticide, some several times the limit allowed on other crops. In some cases, more than one barred pesticide was found on the same batches.

Two marijuana-grow businesses chose to have their quarantined plants destroyed rather than tested, while nine others chose to wait for residue levels to drop to trace amounts, enough to have them released for sale.

Four of the nine businesses unsuccessfully sued in Denver District Court to stop the city from quarantining their pot plants .

“Experts testified that residual amounts of pesticides not on the CDA list did not pose a public health threat,” McAllister said. “Denver’s actions are adding unneeded costs to the marijuana industry with no benefit to public health.”

The city eventually agreed to release the marijuana when its pesticde residues reached the lowest level allowable on food. The businesses were then entitlted to sell products that listed those pesticides among its ingredients, officials said.



Two of the pesticides most broadly found, according to test results obtained by The Denver Post, were myclobutanil and imidacloprid.

Myclobutanil is a powerful fungicide whose label warns it may be harmful if inhaled and could impact the central nervous system.

Imidacloprid is an insecticide that, according to its label, is harmful if swallowed, inhaled or absorbed through the skin — three ways that marijuana is consumed.

Yet, both products are allowed for use on certain fruits and vegetables.

The Post in August found that marijuana products at two stores listed barred pesticides, often buried within a list of ingredients that included water, seaweed extract and guano from bats and seabirds.

One shop, LivWell in Denver, said the products were being phased out.

“Any compliant company that uses any non-organic pesticides, fungicides or herbicides is obligated to list the fact that they were used,” LivWell executive director and chief legal strategist Dean Heizer said Tuesday. “Until March of 2015, our facility was using some of those products. We do not use any non-organic, listable pesticides anymore.”

David Migoya: 303-954-1506, dmigoya@denverpost.com or twitter.com/davidmigoya