By Cindy Orser | Chief Science Officer
For those following the now seemingly weekly health and safety bulletins in Colorado recalling cannabis flower and products made from them, one might wonder what is going on? Certainly the use of pesticides is not a new agricultural practice amongst cannabis growers as knowledge of the use of pesticides amongst them is common. The reason the public has been in the dark with regard to pesticide residue on their cannabis is that pesticide screening of cannabis and cannabis products has not been required in the State of Colorado. That all changed with the issuance of Governor Hickenlooper’s Executive Order (“Order”) on November 12, 2015 directing state agencies to address threats to public safety posed by marijuana contaminated by pesticides. As part of this Order, the Governor required the Colorado Department of Health and Environment (“CDPHE”), the Colorado Department of Agriculture (CDA), and the Colorado Department of Revenue (“DOR”) to “utilize all existing investigatory and enforcement authorities established by law to protect against threats to the public safety posed by contaminated marijuana, including, but not limited to, placing contaminated marijuana on administrative hold and destroying contaminated marijuana pursuant to existing law.”
While one might applaud that the status quo of unregulated use of pesticide on cannabis in Colorado is finally coming under the oversight of State regulatory agencies, the implementation of the current random pesticide surveillance is not without headaches and heartbreak. Since the Order was issued, only random sampling has occurred by either by the City of Denver or the CDA or based on complaints or physical observation of pesticide containers unregistered for use on cannabis at a grow location.
States normally rely on the EPA to regulate the agricultural use of pesticides in order to protect human health and the physical environment under the auspices of the Federal Food, Drug and Cosmetic Act (FFDCA) and its amendments, while the FDA enforces EPA tolerances in foods, and the USDA is the responsible enforcement entity for pesticide tolerances in meats, poultry, and eggs, and under narrow circumstances, tobacco products. Because of the disconnect between State and Federal laws relating to cannabis, there are no registered pesticides for use on cannabis as the EPA has not overseen any pesticide trials on cannabis to make health-based claims for establishing allowable tolerance limits for a given pesticide. This is even more of a threatening situation than one might anticipate since cannabis is often combusted and inhaled, we have no idea what the health impact from chronic inhalation of pesticides might be, but one can guess that inhalation of any level of pesticide should be avoided. Combining this deduction with the knowledge that pesticides concentrate along with cannabinoids during extraction, there is reason to be concerned.
One might think to look at similar crops and think of tobacco which is also combusted and inhaled; but, the EPA did not require health based pesticide studies for chronic use of tobacco, only acute use. Tobacco is rarely ingested or extracted and it is not considered a food crop. According to USDA and EPA, under their laws there are currently no established tolerance limits for pesticide residues that apply to domestically grown tobacco. Shockingly, in this country pesticide monitoring has been largely left to the discretion of the tobacco industry, with few exceptions. The U.S. tobacco industry is known to have vigorously lobbied against stricter pesticide controls and public disclosure of residue levels.
Moving forward with implementation of mandatory pesticide screening for Colorado cannabis, reveals the complication of how to determine what the pesticide monitoring list should include and at what method detection limit, and if consideration for how other states have handled the same sticky issue should be taken into consideration. Even though there are established tolerance limits for other food crops for many pesticides commonly used on cannabis, how should tolerance limits be set for pesticides used on cannabis without any health-based studies specifically on cannabis? None of these are straightforward issues to resolve, but progress has been made through the efforts of the Pesticide Working Group as overseen by the CDPHE and CDA with participation from the MED and the Governor’s office but will require more time to clarify and then to certify cannabis testing labs for pesticide screening.
An unfortunate fallout from the Governor’s Order implying a zero tolerance for pesticides has been the implication of innocent pesticide-free growers from the inadvertent use of a pesticide contaminated product called Guardian. At the time of the Governor’s Order, the pesticide “Guardian” was on the list of specifically approved exempt (25b) pesticides. In January 2016, a respected grower in Boulder County became aware there was a potential issue with Guardian due to allegations made in Oregon regarding avermectin, a chemical not listed on the label. Upon learning of this potential issue, the grower proactively ceased using Guardian on or around January 6, 2016. Unfortunately, the concerns regarding Guardian were warranted, as it appears Guardian was utilizing avermectin, a chemical not cleared for use on marijuana plants, and not listed on the product label. In accordance with this new information, the CDA issued a Pesticide Advisory on January 21, 2016, removing Guardian Mite Spray from the approved List. Unfortunately, under the Order, any detectable level of avermectin results in a hold on the entire crop even though only a handful of test samples were taken from a grow of 900 plus plants. Some composited samples contained mother plants and vegetative samples to arrive at a level of unspecified contamination just over the CDA’s method detection limit (MDL) of 5 parts per billion (PPB), in another analogy, like 5 seconds in 32 years.
If we carry along the example of avermectin for the purpose of this story, what about other crop tolerance levels for avermectin, like Crop Group 19, herbs and spices, which was the strategy adopted by the State of Nevada for their medical marijuana pesticide tolerance limits, taking the avermectin action level at 50 ppb. While the accepted testing for such a different crop as oregano may seem inappropriate (and unvalidated) for Cannabis, it can inform us on the toxicity of the compound. Pesticides registered by the EPA for use on other crops established maximum residue levels (MRLs) for those commodities; these tolerance levels serve as useful starting points for establishing residue tolerance guidelines or limits for Cannabis. As example, avermectin MRLs established by the EPA for lettuce is 100 ppb; for strawberry, 20 ppb; for nuts, 10 ppb; for hops, 200 ppb; and, dry herbs, 30 ppb. Levels range from 200 ppb, down to 10 ppb which is twice the CDA’s MDL.
The State of Oregon arbitrarily adopted an action limit of 2X the limit of quantitation, making avermectin cut off at 500 ppb. The State of Massachusetts adopted an across the board action limit for all monitored pesticides, including avermectin to be 10 ppb. Colorado was not impressed and rather went with MDL levels, for avermectin that is 5 ppb. Avermectin itself is not a particular bad player amongst pesticides and in fact a closely related variant, called ivermectin, is widely used in Africa as a prophylactic to avert infections by the parasite responsible for river blindness. Ivermectin is also widely used to avert infections by the heartworm parasite in canines.
While pesticide residues on any crop consumed by humans is a quality metric, the true human health effects of trace amounts of pesticide on cannabis or any other crop will take years of clinical studies to delineate. This has left both cannabis policymakers and well-intentioned cannabis producers with very few guidelines to follow, in terms of reducing the harms to the public environment, protecting the health of the consumer, and allowing for the sustainable production of quality assured cannabis. No matter how the story is written, the ultimate solution to the pesticide screening dilemma for cannabis would be the adoption of standardized cannabis testing protocols and regiments across the US instead of individual states grappling with the task in isolation.
Meanwhile, cannabis growers and producers who play by the rules are unfairly caught up in the milieu of overreaching Orders that do not consider the consequence of a zero tolerance approach to pesticide screening on cannabis, a rule that does not apply to any other commodity in the US, causing damage far beyond the loss associated with an affected crop. Only the acceptance of cannabis as a legitimate food crop at the federal level will clear a rationale path for how to set pesticide tolerance limits.