Using Method Detection Limits to Set Mandatory Reporting Limits for Banned Pesticides: How a Public-Private Partnership Improved Cannabis Regulation in Colorado

  • Image credit: Kiattipong/

    Image credit: Kiattipong/

Mar 1, 2018
Abstract / Synopsis: 

The discovery of nonregistered pesticides contamination in cannabis plant material in Colorado prompted the need to set mandatory reporting limits (MRLs) for these pesticides in the state to ensure public safety. Since then, the Colorado Department of Public Health and Environment (CDPHE) undertook the responsibility for setting such MRLs. Colorado’s novel approach to determine MRLs for each pesticide involved forming a working group with its in-state laboratories and expert volunteers to agree on analytical procedures to determine method detection limits (MDLs) using an industry-standard approach. The authors describe how this approach formed a collaborative public-private partnership where state government agencies worked side by side with laboratories and growers toward a common goal. The multilaboratory study was completed yielding MDLs for 13 pesticides in cannabis flowers using a QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction with analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The authors share the procedures used for the study, an overview of the data generated by the participating laboratories, and the new Colorado MRLs, which became effective on January 1, 2018.

The regulation of pesticide use on cannabis is a complex issue for states with legalized marijuana. Pesticide use is regulated at the federal level; however, cannabis is not a specifically listed crop on any registered pesticide label, and the United States Environmental Protection Agency (US EPA) does not consider cannabis to fit into any general crop groups, such as herbs or spices (1). In addition, no risk assessments have been conducted specifically for pesticide use on cannabis and tolerance limits have not been defined. Pesticide use in cannabis was recognized as a public health and safety concern, but the information deficit and limited available resources left the state of Colorado grappling with how to handle this complex issue when the Denver Department of Environmental Health placed the first holds on 100,000 marijuana plants for improper use of banned pesticides in March 2015.

In the following months, many additional quarantine and recall events occurred. In November 2015, Colorado issued a statewide pesticide policy and executive order (2) addressing the use of pesticides in marijuana. These documents mandated state agencies to consider cannabis contaminated with banned pesticides a threat to public safety, until such a time that scientific assessment establishes which additional pesticides can be safely applied to marijuana.

After issuance of the executive order and statewide policy, the next question was how to get private laboratories certified to perform pesticide testing so the state could mandate this testing for cannabis. Two primary pieces of information were needed: what pesticides are laboratories expected to test for and what are the associated limits? The executive order has frequently been called a zero tolerance policy; while it does establish zero tolerance for the use of a banned pesticide, analytically it is not possible to test to a concentration of zero. Without defining minimum testing requirements, different results would be reported across laboratories. To address these issues, the state initiated a stakeholder process to determine what pesticides should be tested for and what the associated mandatory reporting limits (MRLs) should be.

The Colorado Department of Public Health and Environment (CDPHE) took the lead on oversight of this stakeholder process, which engaged marijuana testing facilities, cultivators, product manufacturers, scientific experts, and other interested parties. The working group first tackled the list of required analytes. The final list selected included 13 pesticides that were considered the most important for testing in Colorado because they are banned for use and have been previously detected in marijuana in the state.

The working group then determined that in the absence of established pesticide tolerance limits, the regulatory limits should be based upon laboratory detection capability. At that time, to obtain this information, a unique public-private collaboration was initiated to design and execute a multilaboratory method detection limit (MDL) study engaging the resources of Colorado’s private marijuana testing facilities and the state’s Department of Agriculture (CDA) laboratory. The results of the study would be used to inform the regulatory limits for the list of 13 pesticides in marijuana. A technical subcommittee of scientists was formed from the stakeholder working group to assist CDPHE in designing the study and reviewing the results.

Study Design and Preparation

Following the decision to design a multilaboratory study (MLS), Restek volunteered to help CDPHE form a study design and oversight (SDO) team to ensure the multilaboratory study’s success. Since no study of this kind had ever been attempted in the past and there was no standardized analytical method protocol for participant laboratories to follow, the SDO team’s goal was to minimize variables by applying study guidelines based on industry-standard practices. Also, since the marijuana flower buds are an expensive commodity and time was of the essence given the governor’s directive, careful planning and execution were required to produce statistically valid data that the state could use for decision-making upon completion of the first round.

The team consisted of two CDPHE personnel, one representative from Neptune and Company, one from Lowry Consulting—all based in Colorado—and three from Restek Corporation located in Bellefonte, Pennsylvania. The team began to meet regularly to design guidance documents by which labs would be asked to conduct their testing.

  1. Colorado Department of Agriculture, Factual and Policy Issues Related to the Use of Pesticides on Cannabis, (paragraph 4), CDA link: OrJR39b6MA1M9AH/view.
  2. Office of the Governor, Denver, Colorado, D2015-015 Executive Order Directing State Agencies to Address Threats to Public Safety Posed by Marijuana Contaminated by Pesticide (November 12, 2015).
  3. European Commission Directorate-General For Health and Food Safety, SANTE 2015 Guidance document on analytical quality control and method validation procedures for pesticides residues analysis in food and feed (SANTE/11945/2015 30 November-1 December 2015 rev. 0).
  4. Code of Federal Regulations (CFR), 40 Appendix B to Part 136 -Definition and Procedure for the Determination of the Method Detection Limit-Revision 1.11. (J U.S. Government Printing Office, Washington, D.C., 2011).
  5. Colorado Retail Marijuana Code Adopted Rules, CCR 1 212-2, Rule 712, Section R 712 - Retail Marijuana Testing Facilities: Sampling and Testing Program, E. Permissible Levels of Contaminants, (Adopted November 17,2017; effective January 1, 2018), pp. 124-125.

How to Cite This Article

J. Konschnik, H. Krug, S. Kassner, Cannabis Science and Technology 1(1), 42-47 (2018).

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