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==Introduction==
==Introduction==
The use of [[Cannabis (drug)|medicinal cannabis]] is legal in 20 countries and 33 U.S. states, while two countries, Canada and Uruguay, have fully [[Legality of cannabis|legalized]] the sale and use of recreational [[cannabis]] nationwide.<ref name="HassanWhere18">{{cite web |url=https://qz.com/1427177/where-is-marijuana-legal-around-the-world/ |title=All the places in the world you can (legally) smoke weed |author=Hassan, A. |work=Quartz |date=17 October 2018 |accessdate=01 May 2019}}</ref> In the U.S., 11 states and the District of Columbia have legalized recreational use of cannabis, but it is still illegal at the federal level. Many countries and U.S. states have decriminalized possession and use of cannabis.<ref name="DISAMap19">{{cite web |url=https://disa.com/map-of-marijuana-legality-by-state |title=Map of Marijuana Legality by State |publisher=DISA Global Solutions |date=2019 |accessdate=01 May 2019}}</ref> With so many people having access to cannabis, there is an increased need to [[RefWork:Past, Present, and Future of Cannabis Laboratory Testing and Regulation in the United States|test cannabis]] products to ensure their safety. ''Cannabis'' plants are subject to various pests and diseases which may require the judicious use of [[pesticide]]s to maintain plant health. McPartland has published two comprehensive reviews on the diseases<ref name="McPartlandARev96">{{cite journal |title=A review of ''Cannabis'' diseases |journal=Journal of the International Hemp Association |author=McPartland, J.M. |volume=3 |issue=1 |pages=19–23 |year=1996 |url=http://www.internationalhempassociation.org/jiha/iha03111.html}}</ref> and pests<ref name="McPartlandCanna96">{{cite journal |title=''Cannabis'' pests |journal=Journal of the International Hemp Association |author=McPartland, J.M. |volume=3 |issue=2 |pages=49, 52–55 |year=1996 |url=http://www.internationalhempassociation.org/jiha/iha03201.html}}</ref> that attack ''Cannabis'' plants. But, pesticide residues on the plant material are particularly concerning because cannabis can be ingested, smoked, or extracted and concentrated for use in everything from food and beverages to tinctures and suppositories. Many jurisdictions that have legalized cannabis require testing for pesticide residues. For example, Oregon<ref name="FarrerTech15">{{cite web |url=https://www.oregon.gov/oha/ph/PreventionWellness/marijuana/Documents/oha-8964-technical-report-marijuana-contaminant-testing.pdf |format=PDF |title=Technical report: Oregon Health Authority’s process to decide which types of contaminants to test for in cannabis products, and levels for action |author=Farrer, D.G. |publisher=Oregon Health Authority |date=December 2015 |accessdate=01 May 2019}}</ref>, California<ref name="TRCCRResid">{{cite web |url=https://govt.westlaw.com/calregs/Document/I8CCCCCCFBE19419D9DDFFA11E5E29042?viewType=FullText&originationContext=documenttoc&transitionType=CategoryPageItem&contextData=(sc.Default)#co_anchor_IB78AA9DD7002490FB0286370F626BEB |title=16 CCR § 5719 Residual Pesticides Testing |work=Westlaw |publisher=Thomson Reuters |accessdate=01 May 2019}}</ref>, and Canada<ref name="GoCMand19">{{cite web |url=https://www.canada.ca/en/public-health/services/publications/drugs-health-products/cannabis-testing-pesticide-list-limits.html |title=Mandatory cannabis testing for pesticide active ingredients - List and limits |author=Health Canada |publisher=Government of Canada |date=2019 |accessdate=01 May 2019}}</ref> have lists of 59, 66, and 95 pesticides, respectively, that must be targeted by analysts. However, some growers use pesticides that are not on lists of acceptable compounds for which maximum residue limits (MRLs) have been set. Product recalls are common, companies have gone out of business, and occasionally, someone is fined for the misuse of pesticides. On top of this, the unregulated market for cannabis is still much bigger than the legal market.<ref name="McGovern11Facts18">{{cite web |url=https://www.greenentrepreneur.com/article/324679 |title=11 Facts Cannabis Entrepreneurs Should Know About the Black Market |author=McGovern, S. |work=Green Entrepreneur |date=17 December 2018 |accessdate=01 May 2019}}</ref> Many of the illegal growers use pesticides carelessly and leave unknown levels of sometimes illegal pesticides on the plant material. One real concern is the affect that pesticides and [[cannabinoid]]s might have on a developing fetus.<ref name="LeungAdverse19">{{cite journal |title=Adverse outcome pathway of developmental neurotoxicity resulting from prenatal exposures to cannabis contaminated with organophosphate pesticide residues |journal=Reproductive Toxicology |author=Leung, M.C.K.; Silva, M.H.; Palumbo, A.J. et al. |volume=85 |pages=12–18 |year=2019 |doi=10.1016/j.reprotox.2019.01.004 |pmid=30668982}}</ref>
The use of [[Cannabis (drug)|medicinal cannabis]] is legal in 20 countries and 33 U.S. states, while two countries, Canada and Uruguay, have fully [[Legality of cannabis|legalized]] the sale and use of recreational [[cannabis]] nationwide.<ref name="HassanWhere18">{{cite web |url=https://qz.com/1427177/where-is-marijuana-legal-around-the-world/ |title=All the places in the world you can (legally) smoke weed |author=Hassan, A. |work=Quartz |date=17 October 2018 |accessdate=01 May 2019}}</ref> In the U.S., 11 states and the District of Columbia have legalized recreational use of cannabis, but it is still illegal at the federal level. Many countries and U.S. states have decriminalized possession and use of cannabis.<ref name="DISAMap19">{{cite web |url=https://disa.com/map-of-marijuana-legality-by-state |title=Map of Marijuana Legality by State |publisher=DISA Global Solutions |date=2019 |accessdate=01 May 2019}}</ref> With so many people having access to cannabis, there is an increased need to [[RefWork:Past, Present, and Future of Cannabis Laboratory Testing and Regulation in the United States|test cannabis]] products to ensure their safety. ''Cannabis'' plants are subject to various pests and diseases which may require the judicious use of [[pesticide]]s to maintain plant health. McPartland has published two comprehensive reviews on the diseases<ref name="McPartlandARev96">{{cite journal |title=A review of ''Cannabis'' diseases |journal=Journal of the International Hemp Association |author=McPartland, J.M. |volume=3 |issue=1 |pages=19–23 |year=1996 |url=http://www.internationalhempassociation.org/jiha/iha03111.html}}</ref> and pests<ref name="McPartlandCanna96">{{cite journal |title=''Cannabis'' pests |journal=Journal of the International Hemp Association |author=McPartland, J.M. |volume=3 |issue=2 |pages=49, 52–55 |year=1996 |url=http://www.internationalhempassociation.org/jiha/iha03201.html}}</ref> that attack ''Cannabis'' plants. But, pesticide residues on the plant material are particularly concerning because cannabis can be ingested, smoked, or extracted and concentrated for use in everything from food and beverages to tinctures and suppositories. Many jurisdictions that have legalized cannabis require testing for pesticide residues. For example, Oregon<ref name="FarrerTech15">{{cite web |url=https://www.oregon.gov/oha/ph/PreventionWellness/marijuana/Documents/oha-8964-technical-report-marijuana-contaminant-testing.pdf |format=PDF |title=Technical report: Oregon Health Authority’s process to decide which types of contaminants to test for in cannabis products, and levels for action |author=Farrer, D.G. |publisher=Oregon Health Authority |date=December 2015 |accessdate=01 May 2019}}</ref>, California<ref name="TRCCRResid">{{cite web |url=https://govt.westlaw.com/calregs/Document/I8CCCCCCFBE19419D9DDFFA11E5E29042?viewType=FullText&originationContext=documenttoc&transitionType=CategoryPageItem&contextData=(sc.Default)#co_anchor_IB78AA9DD7002490FB0286370F626BEB |title=16 CCR § 5719 Residual Pesticides Testing |work=Westlaw |publisher=Thomson Reuters |accessdate=01 May 2019}}</ref>, and Canada<ref name="GoCMand19">{{cite web |url=https://www.canada.ca/en/public-health/services/publications/drugs-health-products/cannabis-testing-pesticide-list-limits.html |title=Mandatory cannabis testing for pesticide active ingredients - List and limits |author=Health Canada |publisher=Government of Canada |date=2019 |accessdate=01 May 2019}}</ref> have lists of 59, 66, and 95 pesticides, respectively, that must be targeted by analysts. However, some growers use pesticides that are not on lists of acceptable compounds for which maximum residue limits (MRLs) have been set. Product recalls are common, companies have gone out of business, and occasionally, someone is fined for the misuse of pesticides. On top of this, the unregulated market for cannabis is still much bigger than the legal market.<ref name="McGovern11Facts18">{{cite web |url=https://www.greenentrepreneur.com/article/324679 |title=11 Facts Cannabis Entrepreneurs Should Know About the Black Market |author=McGovern, S. |work=Green Entrepreneur |date=17 December 2018 |accessdate=01 May 2019}}</ref> Many of the illegal growers use pesticides carelessly and leave unknown levels of sometimes illegal pesticides on the plant material. One real concern is the affect that pesticides and [[cannabinoid]]s might have on a developing fetus.<ref name="LeungAdverse19">{{cite journal |title=Adverse outcome pathway of developmental neurotoxicity resulting from prenatal exposures to cannabis contaminated with organophosphate pesticide residues |journal=Reproductive Toxicology |author=Leung, M.C.K.; Silva, M.H.; Palumbo, A.J. et al. |volume=85 |pages=12–18 |year=2019 |doi=10.1016/j.reprotox.2019.01.004 |pmid=30668982}}</ref>
Typically, [[Laboratory|laboratories]] test for pesticide residues on cannabis using [[gas chromatography]] and liquid chromatography with [[Tandem mass spectrometry|tandem]] [[quadrupole]] detectors (GC/MS/MS and LC/MS/MS). These instruments are extremely sensitive and are very selective in the multiple reaction monitoring mode. However, they can only find those pesticides that are on the target list. Other pesticides and environmental contaminants will be missed.
Clandestine cannabis growers often use illegal pesticides at their grow sites. For example, [[carbofuran]], a [[carbamate]] insecticide that is now banned for use in the U.S., was found at 78% of eradicated illegal grow sites in 2017.<ref name="FimriteIlleg18">{{cite web |url=https://www.sfchronicle.com/green/article/Illegal-pot-grows-spread-deadly-pesticides-other-12952302.php |title=Illegal pot grows spread deadly pesticides, other hazards, despite change in law |author=Fimrite, P. |work=San Francisco Chronicle |date=29 May 2018 |accessdate=01 May 2020}}</ref><ref name="ThompsonAnEver17">{{cite journal |title=An ever-changing ecological battlefield: marijuana cultivation and toxicant use in western forests |journal=The Wildlife Professional |author=Thompson, C.M.; Gabriel, M.W.; Purcell, K.L. |volume=11 |issue=3 |pages=42–6 |year=2017 |url=https://www.fs.usda.gov/treesearch/pubs/55041}}</ref> This highly toxic pesticide would be missed by typical laboratory testing procedures employing GC/MS/MS and LC/MS/MS for target compound analysis.
Because cannabis has been illegal in most countries around the world, there are not many studies available that evaluate cannabis samples for pesticide residues. A recent paper describes three sample preparation methods for cannabis leaves, dried [[Inflorescence|flowers]], and oils with analysis of pesticide residues by HPLC/MS/MS, GC/MS/MS, and GC/MS. One hundred and forty-four samples of cannabis leaves, dried flowers, and oils were obtained from Canadian dispensaries and were tested using their validated methods. Of 26 samples that contained unauthorized pesticides, [[myclobutanil]] was found most often (20 samples) followed by the [[acaricide]] bifenazate in nine samples.<ref name="MoulinsMulti18">{{cite journal |title=Multiresidue Method of Analysis of Pesticides in Medical Cannabis |journal=Journal of AOAC International |author=Moulins, J.R.; Blais, M.; Montsion, K. et al. |volume=101 |issue=6 |pages=1948–60 |year=2018 |doi=10.5740/jaoacint.17-0495 |pmid=29843862}}</ref> Schneider ''et al.''<ref name="SchneiderDetect13">{{cite journal |title=Detection of pesticides in seized illegal cannabis plants |journal=Analytical Methods |author=Schneider, S.; Bebing, R.; Dauberschmidt, C. |volume=6 |issue=2 |pages=515–20 |year=2013 |doi=10.1039/C3AY40930A}}</ref> analyzed 50 samples of confiscated cannabis for 160 pesticides by UHPLC/MS/MS and GC/MS in the scan mode. Seven different pesticides were found in 19 samples. A [[Headspace gas chromatography for dissolved gas measurement|headspace]] [[Solid-phase extraction|solid-phase microextraction]] GC/MS method has been tested for the quantitative analysis of nine pesticides in cannabis.<ref name="IliasHead06">{{cite journal |title=Headspace Solid-Phase Microextraction of Pesticide Residues in Cannabis Samples |journal=CHIMIA International Journal for Chemistry |author=Ilias, Y.; Rudaz, S.; Christen, P. et al. |volume=60 |issue=12 |pages=846–51 |year=2006 |doi=10.2533/chimia.2006.846}}</ref>
Here, we describe a procedure for [[Screening (environmental)|suspect screening]] using gas chromatography coupled to a high-resolution accurate mass [[quadrupole]] [[Time-of-flight mass spectrometry|time-of-flight mass spectrometer]] (GC/Q-TOF) together with a Pesticides and Environmental Pollutants (P&EP) Personal Compound Database and Library (PCDL). The PCDL contains chemical formulas, isotope patterns, and electron ionization mass spectra with accurate monoisotopic mass assignments for more than 1,000 GC-amenable pesticides and environmental contaminants. The method allows one to presumptively identify contaminants without the need to purchase analytical [[Wikipedia:Primary standard|reference standards]]. Of course, standards are required for positive identification or for quantitative analysis. The procedure is qualitative in nature, but quantification is possible when standards are available. The GC/Q-TOF, together with a pesticide PCDL, have been used for the detection of pesticides in aquatic environments<ref name="MoschetLC-17">{{cite journal |title=LC- and GC-QTOF-MS as Complementary Tools for a Comprehensive Micropollutant Analysis in Aquatic Systems |journal=Environmental Science and Technology |author=Moschet, C.; Lew, B.M.; Hasenbein, S. et al. |volume=51 |issue=3 |pages=1553-1561 |year=2017 |doi=10.1021/acs.est.6b05352 |pmid=328026950 |pmc=PMC7238889}}</ref> and in various foods<ref name="ChenScreen17">{{cite web |url=https://gcms.cz/labrulez-bucket-strapi-h3hsga3/paper/5991-8170EN.pdf |format=PDF |title=Screening of Pesticides and Other Contaminants in Food Matrices Using a Novel High‑resolution GC/Q-TOF with a Low‑energy‑capable EI Source |author=Chen, K.; Sanderson, J. |publisher=Agilent Technologies, Inc |date=16 June 2017}}</ref><ref name="LiScreen18">{{cite journal |title=Screening of 439 Pesticide Residues in Fruits and Vegetables by Gas Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry Based on TOF Accurate Mass Database and Q-TOF Spectrum Library |journal=Journal of AOAC International |author=Li, J.-X.; Li, X.-Y.; Chang, Q.-Y. et al. |volume=101 |issue=5 |pages=1631–8 |year=2018 |doi=10.5740/jaoacint.17-0105 |pmid=29724258}}</ref>, but it has never been used to analyze pesticide residues in cannabis. While this paper describes the analysis of GC-amenable pesticide residues on cannabis, there is a need for a similar broad screening method using high-resolution accurate mass [[liquid chromatography–mass spectrometry]] (LC–MS) because most (but not all) pesticides are LC-amenable.
This method is intended to help analysts such as government regulators, researchers, and other labs find pesticides on cannabis samples that may not be on a laboratory’s normal target list. As new cannabis companies establish their brand name, and as established companies move into the cannabis market, there will be greater incentive to protect their brand reputation by making sure that no unapproved pesticides contaminate their products.


==References==
==References==

Revision as of 22:09, 19 September 2020

Full article title Screening for more than 1,000 pesticides and environmental contaminants in cannabis by GC/Q-TOF
Journal Medical Cannabis and Cannabinoids
Author(s) Wylie, P.L.; Westland, J.; Wang, M.; Radwan, M.M.; Majumdat, C.G.; ElSohly, M.A.
Author affiliation(s) Agilent Technologies, University of Mississippi, ElSohly Laboratories
Primary contact Email: Philip dot l dot wylie at gmail dot com
Year published 2020
Volume and issue 3(1)
Page(s) 14–24
DOI 10.1159/000504391
ISSN 2504-3889
Distribution license Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Website https://www.karger.com/Article/FullText/504391
Download https://www.karger.com/Article/Pdf/504391 (PDF)
Emblem-important-yellow.svg This article should be considered a work in progress and incomplete. Consider this article incomplete until this notice is removed.

Abstract

A method has been developed to screen cannabis extracts for more than 1,000 pesticides and environmental pollutants using gas chromatography coupled to a high-resolution accurate mass quadrupole time-of-flight mass spectrometer (GC/Q-TOF). An extraction procedure was developed using acetonitrile with solid-phase extraction cleanup. Before analysis, extracts were diluted 125:1 with solvent. Two data mining approaches were used together with a retention-time-locked Personal Compound Database and Library (PCDL) containing high-resolution accurate mass spectra for pesticides and other environmental pollutants. In the first approach, a Find-by-Fragments (FbF) software tool extracted several characteristic exact mass ions within a small retention time window where the compound eluted. For each compound in the PCDL, the software evaluated the peak shape and retention time of each ion, as well as the monoisotopic exact mass, ion ratios, and other factors to decide if the compound was present or not. In the second approach, Unknowns Analysis (UA) software with a peak-finding algorithm called SureMass was used to deconvolute peaks in the chromatogram. The accurate mass spectra were searched against the PCDL using spectral matching and retention time as filters. A subset PCDL was generated containing only pesticides that are most likely to be found on foods in the US. With about 250 compounds in the smaller PCDL, there were fewer hits for non-pesticides, and data review was much faster. Organically grown cannabis was used for method development. Twenty-one confiscated cannabis samples were analyzed and ten were found to have no detectable pesticides. The remaining 11 samples had at least one pesticide, and one sample had seven detectable residues. Quantitative analysis was run on the confiscated samples for a subset of the pesticides found by screening. Two cannabis samples had residues of carbaryl and malathion that were estimated to be about 10 times greater than the highest U.S. Environmental Protection Agency (EPA) tolerance set for food and about 4,000 times greater than the Canadian maximum residue limits for dried cannabis flower.

Introduction

The use of medicinal cannabis is legal in 20 countries and 33 U.S. states, while two countries, Canada and Uruguay, have fully legalized the sale and use of recreational cannabis nationwide.[1] In the U.S., 11 states and the District of Columbia have legalized recreational use of cannabis, but it is still illegal at the federal level. Many countries and U.S. states have decriminalized possession and use of cannabis.[2] With so many people having access to cannabis, there is an increased need to test cannabis products to ensure their safety. Cannabis plants are subject to various pests and diseases which may require the judicious use of pesticides to maintain plant health. McPartland has published two comprehensive reviews on the diseases[3] and pests[4] that attack Cannabis plants. But, pesticide residues on the plant material are particularly concerning because cannabis can be ingested, smoked, or extracted and concentrated for use in everything from food and beverages to tinctures and suppositories. Many jurisdictions that have legalized cannabis require testing for pesticide residues. For example, Oregon[5], California[6], and Canada[7] have lists of 59, 66, and 95 pesticides, respectively, that must be targeted by analysts. However, some growers use pesticides that are not on lists of acceptable compounds for which maximum residue limits (MRLs) have been set. Product recalls are common, companies have gone out of business, and occasionally, someone is fined for the misuse of pesticides. On top of this, the unregulated market for cannabis is still much bigger than the legal market.[8] Many of the illegal growers use pesticides carelessly and leave unknown levels of sometimes illegal pesticides on the plant material. One real concern is the affect that pesticides and cannabinoids might have on a developing fetus.[9]

Typically, laboratories test for pesticide residues on cannabis using gas chromatography and liquid chromatography with tandem quadrupole detectors (GC/MS/MS and LC/MS/MS). These instruments are extremely sensitive and are very selective in the multiple reaction monitoring mode. However, they can only find those pesticides that are on the target list. Other pesticides and environmental contaminants will be missed.

Clandestine cannabis growers often use illegal pesticides at their grow sites. For example, carbofuran, a carbamate insecticide that is now banned for use in the U.S., was found at 78% of eradicated illegal grow sites in 2017.[10][11] This highly toxic pesticide would be missed by typical laboratory testing procedures employing GC/MS/MS and LC/MS/MS for target compound analysis.

Because cannabis has been illegal in most countries around the world, there are not many studies available that evaluate cannabis samples for pesticide residues. A recent paper describes three sample preparation methods for cannabis leaves, dried flowers, and oils with analysis of pesticide residues by HPLC/MS/MS, GC/MS/MS, and GC/MS. One hundred and forty-four samples of cannabis leaves, dried flowers, and oils were obtained from Canadian dispensaries and were tested using their validated methods. Of 26 samples that contained unauthorized pesticides, myclobutanil was found most often (20 samples) followed by the acaricide bifenazate in nine samples.[12] Schneider et al.[13] analyzed 50 samples of confiscated cannabis for 160 pesticides by UHPLC/MS/MS and GC/MS in the scan mode. Seven different pesticides were found in 19 samples. A headspace solid-phase microextraction GC/MS method has been tested for the quantitative analysis of nine pesticides in cannabis.[14]

Here, we describe a procedure for suspect screening using gas chromatography coupled to a high-resolution accurate mass quadrupole time-of-flight mass spectrometer (GC/Q-TOF) together with a Pesticides and Environmental Pollutants (P&EP) Personal Compound Database and Library (PCDL). The PCDL contains chemical formulas, isotope patterns, and electron ionization mass spectra with accurate monoisotopic mass assignments for more than 1,000 GC-amenable pesticides and environmental contaminants. The method allows one to presumptively identify contaminants without the need to purchase analytical reference standards. Of course, standards are required for positive identification or for quantitative analysis. The procedure is qualitative in nature, but quantification is possible when standards are available. The GC/Q-TOF, together with a pesticide PCDL, have been used for the detection of pesticides in aquatic environments[15] and in various foods[16][17], but it has never been used to analyze pesticide residues in cannabis. While this paper describes the analysis of GC-amenable pesticide residues on cannabis, there is a need for a similar broad screening method using high-resolution accurate mass liquid chromatography–mass spectrometry (LC–MS) because most (but not all) pesticides are LC-amenable.

This method is intended to help analysts such as government regulators, researchers, and other labs find pesticides on cannabis samples that may not be on a laboratory’s normal target list. As new cannabis companies establish their brand name, and as established companies move into the cannabis market, there will be greater incentive to protect their brand reputation by making sure that no unapproved pesticides contaminate their products.

References

  1. ↑ Hassan, A. (17 October 2018). "All the places in the world you can (legally) smoke weed". Quartz. https://qz.com/1427177/where-is-marijuana-legal-around-the-world/. Retrieved 01 May 2019. 
  2. ↑ "Map of Marijuana Legality by State". DISA Global Solutions. 2019. https://disa.com/map-of-marijuana-legality-by-state. Retrieved 01 May 2019. 
  3. ↑ McPartland, J.M. (1996). "A review of Cannabis diseases". Journal of the International Hemp Association 3 (1): 19–23. http://www.internationalhempassociation.org/jiha/iha03111.html. 
  4. ↑ McPartland, J.M. (1996). "Cannabis pests". Journal of the International Hemp Association 3 (2): 49, 52–55. http://www.internationalhempassociation.org/jiha/iha03201.html. 
  5. ↑ Farrer, D.G. (December 2015). "Technical report: Oregon Health Authority’s process to decide which types of contaminants to test for in cannabis products, and levels for action" (PDF). Oregon Health Authority. https://www.oregon.gov/oha/ph/PreventionWellness/marijuana/Documents/oha-8964-technical-report-marijuana-contaminant-testing.pdf. Retrieved 01 May 2019. 
  6. ↑ "16 CCR § 5719 Residual Pesticides Testing". Westlaw. Thomson Reuters. https://govt.westlaw.com/calregs/Document/I8CCCCCCFBE19419D9DDFFA11E5E29042?viewType=FullText&originationContext=documenttoc&transitionType=CategoryPageItem&contextData=(sc.Default)#co_anchor_IB78AA9DD7002490FB0286370F626BEB. Retrieved 01 May 2019. 
  7. ↑ Health Canada (2019). "Mandatory cannabis testing for pesticide active ingredients - List and limits". Government of Canada. https://www.canada.ca/en/public-health/services/publications/drugs-health-products/cannabis-testing-pesticide-list-limits.html. Retrieved 01 May 2019. 
  8. ↑ McGovern, S. (17 December 2018). "11 Facts Cannabis Entrepreneurs Should Know About the Black Market". Green Entrepreneur. https://www.greenentrepreneur.com/article/324679. Retrieved 01 May 2019. 
  9. ↑ Leung, M.C.K.; Silva, M.H.; Palumbo, A.J. et al. (2019). "Adverse outcome pathway of developmental neurotoxicity resulting from prenatal exposures to cannabis contaminated with organophosphate pesticide residues". Reproductive Toxicology 85: 12–18. doi:10.1016/j.reprotox.2019.01.004. PMID 30668982. 
  10. ↑ Fimrite, P. (29 May 2018). "Illegal pot grows spread deadly pesticides, other hazards, despite change in law". San Francisco Chronicle. https://www.sfchronicle.com/green/article/Illegal-pot-grows-spread-deadly-pesticides-other-12952302.php. Retrieved 01 May 2020. 
  11. ↑ Thompson, C.M.; Gabriel, M.W.; Purcell, K.L. (2017). "An ever-changing ecological battlefield: marijuana cultivation and toxicant use in western forests". The Wildlife Professional 11 (3): 42–6. https://www.fs.usda.gov/treesearch/pubs/55041. 
  12. ↑ Moulins, J.R.; Blais, M.; Montsion, K. et al. (2018). "Multiresidue Method of Analysis of Pesticides in Medical Cannabis". Journal of AOAC International 101 (6): 1948–60. doi:10.5740/jaoacint.17-0495. PMID 29843862. 
  13. ↑ Schneider, S.; Bebing, R.; Dauberschmidt, C. (2013). "Detection of pesticides in seized illegal cannabis plants". Analytical Methods 6 (2): 515–20. doi:10.1039/C3AY40930A. 
  14. ↑ Ilias, Y.; Rudaz, S.; Christen, P. et al. (2006). "Headspace Solid-Phase Microextraction of Pesticide Residues in Cannabis Samples". CHIMIA International Journal for Chemistry 60 (12): 846–51. doi:10.2533/chimia.2006.846. 
  15. ↑ Moschet, C.; Lew, B.M.; Hasenbein, S. et al. (2017). "LC- and GC-QTOF-MS as Complementary Tools for a Comprehensive Micropollutant Analysis in Aquatic Systems". Environmental Science and Technology 51 (3): 1553-1561. doi:10.1021/acs.est.6b05352. PMC PMC7238889. PMID 328026950. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=PMC7238889. 
  16. ↑ Chen, K.; Sanderson, J. (16 June 2017). "Screening of Pesticides and Other Contaminants in Food Matrices Using a Novel High‑resolution GC/Q-TOF with a Low‑energy‑capable EI Source" (PDF). Agilent Technologies, Inc. https://gcms.cz/labrulez-bucket-strapi-h3hsga3/paper/5991-8170EN.pdf. 
  17. ↑ Li, J.-X.; Li, X.-Y.; Chang, Q.-Y. et al. (2018). "Screening of 439 Pesticide Residues in Fruits and Vegetables by Gas Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry Based on TOF Accurate Mass Database and Q-TOF Spectrum Library". Journal of AOAC International 101 (5): 1631–8. doi:10.5740/jaoacint.17-0105. PMID 29724258. 

Notes

This presentation is faithful to the original, with only a few minor changes to presentation. Some grammar and punctuation was cleaned up to improve readability. In some cases important information was missing from the references, and that information was added.

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