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| Generally speaking, a [[Contamination|contaminant]] is an unwanted substance that may show up in the final product, be it recreational marijuana or a pharmaceutical company's therapeutic tincture. The following are examples of contaminants that laboratories may test for in cannabis products.
| | A great number of approaches to analyzing cannabis constituents and contaminants have been developed and prescribed over the years. The following section examines the most common of these approaches. |
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| '''Pesticides''': [[Pesticide]]s represent the Wild West of not only growing cannabis but also performing analytical testing on it. One of the core issues, again, is the fact that on the federal level marijuana is illegal. Because it's illegal, government agencies such as the [[United States Environmental Protection Agency|Environmental Protection Agency]] (EPA) don't test and create standards or guidelines for what's safe when it comes to residual pesticides, let alone how to best test for them.<ref name="BorelTheWild15">{{cite web |url=https://www.theatlantic.com/health/archive/2015/08/pot-marijuana-pesticide-legalization/401771/ |title=The Wild West of Marijuana Pesticides |author=Borel, B. |work=The Atlantic |publisher=The Atlantic Monthly Group |date=31 August 2015 |accessdate=07 July 2021}}</ref><ref name="ZhangNobody15">{{cite web |url=https://www.wired.com/2015/08/nobody-knows-pesticides-legal-marijuana/ |title=Nobody Knows What to Do About Pesticides in Legal Marijuana |author=Zhang, S. |work=Wired |publisher=Condé Nast |date=07 August 2015 |accessdate=07 July 2021}}</ref> Additionally, researchers face their fair share of difficulties obtaining product to test. The end result is we don't know much about how inhalation of pesticide-coated marijuana smoke affects long-term health<ref name="BorelTheWild15" /><ref name="ZhangNobody15" />, and we have few standard methods for pesticide application and testing.<ref name="CassidayTheHighs16">{{cite web |url=https://www.aocs.org/stay-informed/inform-magazine/featured-articles/the-highs-and-lows-of-cannabis-testing-october-2016 |title=The Highs and Lows of Cannabis Testing |author=Cassiday, L. |work=INFORM |publisher=American Oil Chemists' Society |date=October 2016 |accessdate=07 July 2021}}</ref><ref name="DeibelPesticide19">{{cite web |url=https://cannabisindustryjournal.com/feature_article/pesticide-testing-methods-strategies-sampling/ |title=Pesticide Testing: Methods, Strategies & Sampling |author=Deibel, C. |work=Cannabis Industry Journal |date=29 January 2019 |accessdate=07 July 2021}}</ref> With numerous pesticide products and little oversight on what growers apply to their plants, combined with the technical difficulty of testing for pesticides in the lab, pesticides remain one of the most difficult contaminants to test for.<ref name="CassidayTheHighs16" /><ref name="DeibelPesticide19" /> That said, several classes of of pesticides are commonly applied during cannabis cultivation and can be tested for by labs<ref name="APHLGuide16">{{cite web |url=https://www.aphl.org/aboutAPHL/publications/Documents/EH-Guide-State-Med-Cannabis-052016.pdf |format=PDF |title=Guidance for State Medical Cannabis Testing Programs |author=Association of Public Health Laboratories |pages=35 |date=May 2016 |accessdate=07 July 2021}}</ref><ref name="KuzdzalACloser16">{{cite web |url=https://www.ssi.shimadzu.com/sites/ssi.shimadzu.com/files/Industry/Literature/Shimadzu_Whitepaper_Emerging_Cannabis_Industry.pdf |format=PDF |title=A Closer Look at Cannabis Testing |author=Kuzdzal, S.; Clifford, R.; Winkler, P.; Bankert, W. |publisher=Shimadzu Corporation |date=December 2017 |accessdate=07 July 2021}}</ref><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 Determine 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=07 July 2021}}</ref>:
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| {{flowlist |
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| * '''[[avermectin]]s''': function as an insecticide that is useful against mites, which are a common problem for cultivators
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| * '''[[carbamate]]s''': function as an insecticide, similar to organophosphates, but with decreased dermal toxicity and higher degradation
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| * '''[[organophosphate]]s''': function as the base of many insecticides and herbicides, valued for its easy organic bonding
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| * '''[[pyrethroid]]s''': function as the base of most household insecticides and exhibits insect repellent properties
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| }}
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| '''Solvents''': In 2003, Canadian Rick Simpson published a recipe of sorts for preparing cannabis extract via the use of [[solvent]]s such as naphtha or petroleum ether. Claiming the resulting oil helped cure his skin cancer, others hoping for a cure tried it, and the solvent method of preparation grew in popularity. Dubious healing claims aside, the solvent extraction method remains viable, though it has evolved over the years to include less harmful solvents such as [[supercritical carbon dioxide]], which has low toxicity, low environmental impact, and beneficial extraction properties.<ref name="CassidayTheHighs16" /><ref name="RomanoCannabis13">{{cite journal |url=http://www.stcm.ch/en/files/hazekamp_cann-oil_2013.pdf |format=PDF |title=Cannabis oil: Chemical evaluation of an upcoming cannabis-based medicine |journal=Cannabinoids |author=Romano, L.L.; Hazekamp, A. |volume=1 |issue=1 |pages=1–11 |year=2013}}</ref><ref name="PeachSuper14">{{cite journal |title=Supercritical carbon dioxide: A solvent like no other |journal=Journal of Organic Chemistry |author=Peach, J.; Eastoe, J. |volume=10 |pages=1878-95 |year=2014 |doi=10.3762/bjoc.10.196 |pmid=25246947 |pmc=PMC4168859}}</ref> However, chemical solvents are still used, and if not evaporated out properly, the remaining solvents can be particularly harmful to sick patients using the extract. As for what solvents should be tested for, it gets a bit trickier, though Chapter 467 of ''United States Pharmacopeia and The National Formulary'', the Oregon Health Authority's December 2015 technical report on contaminant testing of cannabis, and the Massachusetts Department of Public Health's response to public comments on cannabis testing provide helpful guidance. Listed solvents include [[benzene]], [[butane]], [[cumene]], [[dimethoxyethane]], [[hexane]], and [[pentane]], among others.<ref name="KuzdzalACloser16" /><ref name="APHLGuide16" /><ref name="CassidayTheHighs16" /><ref name="FarrerTech15" /><ref name="USPNF467">{{cite web |url=https://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/generalChapter467Current.pdf |archiveurl=https://web.archive.org/web/20160804174451/https://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/generalChapter467Current.pdf |format=PDF |title=<467> Residual Solvents |work=United States Pharmacopeia and The National Formulary |publisher=United States Pharmacopeial Convention |date=01 July 2007 |archivedate=04 August 2016 |accessdate=07 July 2021}}</ref><ref name="MDPHResponse">{{cite web |url=http://www.mass.gov/eohhs/docs/dph/quality/medical-marijuana/lab-protocols/external-comment-response-020416-final.pdf |archiveurl=https://web.archive.org/web/20171013214634/https://www.mass.gov/eohhs/docs/dph/quality/medical-marijuana/lab-protocols/external-comment-response-020416-final.pdf |format=PDF |title=Response to Public Comments |author=Bureau of Healthcare Safety and Quality |publisher=Massachusetts Department of Public Health |date=12 February 2016 |archivedate=13 October 2017 |accessdate=07 July 2021}}</ref>
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| '''Heavy metals''': 2013 research on contaminant testing on the behalf of Washington State provides insights into [[heavy metals]] and why they're looked for in cannabis testing. That research, as well as other sources, tell us<ref name="KuzdzalACloser16" /><ref name="APHLGuide16" /><ref name="CassidayTheHighs16" /><ref name="DaleyTesting13">{{cite web |url=http://lcb.wa.gov/publications/Marijuana/BOTEC%20reports/1a-Testing-for-Contaminants-Final-Revised.pdf |format=PDF |title=Testing ''Cannabis'' for Contaminants |author=Daley, P.; Lampach, D.; Sguerra, S. |publisher=BOTEC Analysis Corp |date=12 September 2013 |accessdate=07 July 2021}}</ref>:
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| * Heavy metals contribute to several health problems, including those of a neurological nature.
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| * Cannabis can "[[Hyperaccumulator|hyperaccumulate]] metals from contaminated soils."
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| * Research parallels can be found in tobacco research and how the FDA regulates heavy metal content in foods.
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| * The most prominently tested heavy metals include [[arsenic]] (As), [[cadmium]] (Cd), [[chromium]] (Cr), [[lead]] (Pb), [[Mercury (element)|mercury]] (Hg), and [[nickel]] (Ni).
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| '''[[Mycotoxin]]s and microorganisms''': "The ideal conditions for cannabis growth are also ideal for the growth of potentially harmful bacteria and fungi, including yeast and molds," say Shimadzu's Scott Kuzdzal and William Lipps, "therefore microbial contamination poses health risks to consumers and immunocompromised individuals."<ref name="KuzdzalUnrav15">{{cite journal |title=Unraveling the Cannabinome |journal=The Analytical Scientist |author=Kuzdzal, S.; Lipps, W. |issue=0915 |year=2015 |url=https://theanalyticalscientist.com/techniques-tools/unraveling-the-cannabinome |accessdate=07 July 2021}}</ref> In truth, these concerns have already borne out. In fact, the University of California, Davis reported in February 2017 one of its patients had contracted an incurable fungal infection from inhaling aerosolized marijuana. They later tested 20 marijuana samples from Northern California dispensaries—using specialized techniques—and found a wide variety of potentially hazardous [[microorganism]]s.<ref name="UCDavis17">{{cite web |url=http://www.ucdmc.ucdavis.edu/publish/news/newsroom/11791 |archiveurl=https://web.archive.org/web/20190927162134/https://health.ucdavis.edu/publish/news/newsroom/11791 |title=UC Davis study finds mold, bacterial contaminants in medical marijuana samples |publisher=UC Davis |date=07 February 2017 |archivedate=27 September 2019 |accessdate=07 July 2021}}</ref>
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| The degree to which such contaminants commonly appear in grown and stored cannabis material and to which microbiological contaminants should be tested is not clear, however. As mentioned previously, neither the U.S. EPA or neighboring Health Canada provide any significant guidance on cannabis testing, including microbiological contaminants.<ref name="KennardYouAre16">{{cite web |url=https://populace.tantaluslabs.com/you-are-probably-smoking-mouldy-weed-why-does-quality-assurance-matter/ |title=You are Probably Smoking Mouldy Weed - Why Does Quality Assurance Matter? |work=Populace |author=Kennard, M. |publisher=Tantalus Labs |date=02 June 2014 |accessdate=07 July 2021}}</ref> Like heavy metal testing, parallels are drawn from microbial testing guidelines and standards relating to tobacco and food, where they exist.<ref name="KennardYouAre16" /> As warm, moist environments are conducive to microorganism growth, maintaining stable moisture levels during cultivation and storage is essential. Regularly measuring [[water activity]]—how moist something is—is particularly useful as a front-line preventative tool to better ensure microbial growth is limited.<ref name="FarrerTech15" /> Regardless, testing of some kind is still required by many U.S. states, including for organisms such as<ref name="KuzdzalUnrav15" /><ref name="APHLGuide16" /><ref name="CassidayTheHighs16" /><ref name="FarrerTech15" /><ref name="UCDavis17" /><ref name="KennardYouAre16" /><ref name="CANNAMicro14">{{cite web |url=https://www.fundacion-canna.es/en/microbiological-study-cannabis-samples |title=Microbiological study of Cannabis samples |publisher=Fundación CANNA |date=2014 |accessdate=07 July 2021}}</ref><ref name="RussoCann13">{{cite book |url=https://books.google.com/books?id=qH-2Lj9x7L4C&pg=PT457&lpg=PT457 |chapter=Chapter 30: Contaminants and Adulterants in Herbal Cannabis |title=Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential |author=McPartland, J.M. |editor=Russo, E.B. |publisher=Routledge |year=2013 |pages=478 |isbn=9781136614934}}</ref>:
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| * ''[[Alternaria]]''
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| * ''[[Aspergillus]]''
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| * ''Cryptococcus''
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| * ''[[Escherichia coli|E. coli]]''
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| * ''Mucor''
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| * ''[[Penicillium]]''
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| * ''[[Salmonella]]''
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| ==References==
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| {{Reflist|colwidth=30em}}
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