Pesticides that are illegal to use on marijuana plants in Colorado are being found in some recreational and medical pot products being marketed and sold to the public -- leading to product recalls, plant quarantines and even a class-action lawsuit involving people who say they would not have inhaled the product had they known illegal pesticides were used on them.
Pesticide testing is not mandatory for pot businesses in Colorado, nor are they subject to random pesticide testing, as are other crops, according to Mitch Yergert of the state's agriculture department. Pot businesses generally are left to self-regulate pesticides use, though officials say they are working to come up with a plan for better oversight.
Given that, CNN decided to do its own tests to see exactly what's in some of the marijuana products sold at Denver dispensaries.
So, CNN asked two Denver pot shops to agree to submit three samples each for pesticides testing to Peter Perrone, who runs a company called Gobi Analytical, one of the few state-licensed labs. Perrone has tested thousands of pot products for pesticides and his lab is the go-to lab for the city of Denver's investigations.
The dispensaries submitted a total of six samples, including flowers, edibles and concentrates.
Five samples tested clean for pesticides, but one concentrate tested positive for a neurotoxin called imidacloprid.
The Colorado Department of Agriculture has said this chemical cannot be used on marijuana. The U.S. Environmental Protection Agency does allow its use on some crops, but only at very low levels -- for example 1 part per million on avocados and 0.5 parts per million on apples.
The pot concentrate sample showed imidacloprid levels of 100 parts per million, a level Perrone says is extremely high. "In this case, I would immediately recall that sample and destroy that entire batch."
That dispensary owner was shocked by the high levels of imidacloprid in the product he was selling, saying "that's sounds awful." He immediately pulled the products from his shelves and reported the results to the state.
Because of the CNN testing, officials launched an investigation, which led to a voluntary recall last week of 2,362 pot products including 23 different types of pot concentrates, all made from marijuana grown and distributed by Tru Cannabis.
Tru Cannabis is no stranger to problems with pesticides. The company was cited as one of two growers in a voluntary recall just last month when three pesticides banned by the state for use on marijuana, including imidacloprid, were found in plants and pot products.
Tru Cannabis declined several requests for an interview, but its chief executive officer, Bruce Nassau, told CNN in a statement, "The health and safety of our customers and employees is our top priority. Because pesticides are regulated by the Environmental Protection Agency and Cannabis is a Schedule I controlled substance at the federal level, there has been confusion about what products can be used on cannabis. Tru Cannabis is working with state and local regulators to resolve this issue with an ongoing focus on the health and safety of the consumer."
A largely self-regulating industry
The big and still unanswered question that worries Perrone -- what happens to these potentially dangerous chemicals when they are burned and then inhaled?
Experts say more research is needed and with marijuana still illegal federally, progress is slow. Perrone is particularly concerned about farm workers inhaling the chemical, as well as medical patients who "might be smoking this all day long and day after day after day" and could be exposed to high levels of these unapproved pesticides.
So who is in charge of making sure pot products don't contain potentially harmful pesticides?
The EPA doesn't have oversight on marijuana, as it does on other crops, because the federal government classifies it as an illegal Schedule 1 drug.
State and local governments primarily have relied upon self-regulation and do not require mandatory pesticides testing for pot growers, "middle-man" businesses that process pot products into edibles or concentrates or dispensaries who sell the products.
Industry experts say testing is expensive and only a few state-licensed labs have the expertise and specialized equipment needed to test for pesticides in pot.
Dan Rowland of Denver's Office of Marijuana Policy says city officials launch pesticide investigations and testing when businesses are flagged, often through fire department inspections, for alleged violations. Denver has 12 ongoing investigations into alleged illegal pesticide use.
Rowland said he worries that the "long-term impacts are unknown" but "the risk is there and that's really all the city needs to step in. In public health, we're going to err on the side of caution."
Because of strict state regulations on tracking, each plant can be traced from seed, to grow facility, in some cases to a factory that processes the product, and on to the store shelf.
Businesses, state trying to address problem
The dispensary owner whose sample tested positive is relieved that the tainted pot can be traced and pulled from all pot shop shelves, not just his own. "The system works on that side, to be able to go back and find out where it is, where the source of this problem is and therefore stop it. Nip it in the bud, as they say."
In the same week CNN notified authorities of its test results, Gov. John Hickenlooper's office issued an executive order "to address threats to public safety posed by marijuana contaminated by off-label pesticide use" and to establish a zero-tolerance policy for companies that violate the rules.
State agencies are working together to figure out how to ensure dangerous pesticides are not used on pot products grown and sold in Colorado.
Ro Silva of the Colorado Department of Revenue, the state agency that oversees the marijuana industry, would not comment, saying it follows a policy of not commenting on ongoing investigations.
Silva did say in an email that the Marijuana Enforcement Division, along with other state agencies, "will continue to develop this portion of mandatory testing by working collaboratively to develop regulations and to certify licensed retail marijuana testing facilities for pesticide testing." She said, "There is not a timeline right now for the MED to test for pesticides."