According to a 2017 report by Arcview Market Research, the legal cannabis industry has accelerated dramatically over the past few years and will continue to grow. In 2016, consumers spent about $6.9 billion on legal cannabis products in North America. This represents a 30 percent growth in spending from the previous year. Much of this growth was in the United States, particularly in states that now allow adult-use marijuana, such as Colorado and Washington.

Last year, other states passed medical cannabis laws and similar initiatives for adult-use marijuana. Based on these developments, the projected annual compounded growth rate over the next five years is an astounding 26 percent, which would push spending to more than $21 billion by 2021.
What does this mean for industrial hygienists? With the projected growth of the legal cannabis market, we expect to see more workers come under the protection of health and safety regulations. A 2017 report by New Frontier Data, The Cannabis Industry Annual Report: 2017 Legal Marijuana Outlook, projects the U.S. cannabis market to create more than 250,000 new jobs by 2020. More industrial hygienists will provide their services to cannabis cultivation, extraction, and retail facilities over the coming years.
Cannabis cultivation and extraction facilities are a unique workplace scenario and have the potential to expose workers to a number of hazards, such as pesticides, marijuana dust, marijuana resin, UV light, and mold spores. According to a 2012 report by National Jewish Health, indoor facilities create greater challenges with greater potential exposures to viable and non-viable mold spores. The report identifies mold as a major hazard, in addition to dermal contact with the resins. In a plant growth environment, workers can also be exposed to excessive UV light from the high-output grow lamps. These exposures are associated with both short-term and long-term negative health effects. Furthermore, protecting the cleanliness of products during production is essential. These circumstances are particularly worrying at indoor cannabis cultivation and extraction facilities, where conditions are warm and damp, and ventilation might be inadequate.
Given the growth outlook and unique hazards, industrial hygienists should be familiar with the potential risks facing cannabis growers and their employees, as well as the correct personal protective equipment (PPE) they should use to ensure both worker and product safety. COVERALLS AND LAB COATS In cultivation facilities, disposable coverall suits, known as Tyvek (by Dupont) coveralls or “bunny suits,” protect workers from exposure to dirt and fertilizers, and from inadvertent contact with pesticides and plant allergens. Bunny suits are also essential when workers are using chemicals such as dilute bleach solutions (for example, those with more than 5 percent sodium hypochlorite) to disinfect areas between plant generations and during particularly dirty operations.
During the cannabis infusion process, where extracted oil is added to edibles, it is important to protect the product from worker contamination. Skin cells, hair follicles, sweat, and any other bodily waste contacting merchandise can affect the flavor, quality, or safety of the product. Lab coats are the best way to maintain purity throughout the infusion and extraction process. Reusable lab coats should be regularly laundered in accordance with U.S. Food and Drug Administration Food Code recommendations (see FDA Food Code 2013 subparts 4-301.15 on clothes washers and dryers, 4-401.11 on washer and dryer location, and 6-305.11 on dressing areas).
Thicker, chemical- resistant gloves are typically recommended when workers mix and apply pesticides in concentrated form. Photo credit: Cordova Safety Products
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GLOVES Hand protection keeps contaminants out of products and shields workers from contact with hazardous substances. The basic product safety protocol is to mandate glove usage by marijuana cultivation and extraction workers. However, not all gloves are created equal, and not every glove is appropriate for every task. It’s critical to select the appropriate glove type and thickness for each exposure scenario. Work in the cannabis industry presents four common exposure scenarios: handling and application of pesticides, cultivation of the plants, extraction of resin, and infusion of extract to food products.

Pesticide Handling and Application To control molds, mildews and insect infestations (mites, for example), various natural and commercial pesticides are used with marijuana crops. According to the Colorado Department of Agriculture, these pesticides include soaps, oils, and pyrethrins. Protective gloves and clothing should be selected in accordance with the manufacturer’s recommendations or based on available chemical resistance data. Thicker, chemical-resistant gloves (for example, those designated as 15 mil) are typically recommended when workers mix and apply pesticides in a concentrated form.
Disinfection for mold control may involve the use of sodium hydroxide (NaOH), also known as caustic soda. Most nitrile and similar rubber products provide adequate protection, but thicker gloves are recommended for concentrated solutions (greater than 30 percent NaOH).
One barrier to glove selection is that limited data often exist on the chemical resistance of gloves and clothing to various pesticides. If pesticide manufacturers do not provide specific recommendations—such as for nitrile, neoprene, or butyl gloves—then other resources need to be consulted. Helpful resources include Quick Selection Guide to Chemical Protective Clothing, published by Wiley; NIOSH’s “Recommendations for Chemical Protective Clothing”; chemical resistance guides published by glove manufacturers; and the scientific literature on chemical permeation. Cultivation For cultivation workers, the repetition of trim work calls for a glove that eases the stress of repetitive motions, lessens contact pressure from holding the shears, and provides cut resistance and chemical resistance. Thinner, disposable nitrile gloves do not withstand the continual abrasion from trimming and are uncomfortable to use with small pruning shears. An abrasion- and cut-resistant glove, such as a nylon fabric glove dipped with nitrile, is recommended. The nitrile coating provides added protection against the isopropyl alcohol commonly used to clean the pruning shears and trays. Extraction Extraction most often involves use of a solvent under conditions of varying pressure and temperature. Common solvents include butane, ethanol, isopropyl alcohol, and heptane. In most cases, thicker chemical-resistant nitrile gloves (15 mil) provide adequate protection against these solvents. However, glove selection should still be based on a hazard evaluation using charts and guidelines for chemical resistance. Disposable gloves are required for handling extract. The material, very viscous and sticky, requires operators to change gloves often to avoid spreading contamination.
Use of butane, a liquefied petroleum gas (LPG), requires additional protection against potential exposures to very low temperature liquids. Some tanks may be immersed in hot or cold water to facilitate transfer; in these circumstances, waterproof cryogenic gloves provide protection against accidental contact with the water or cryogenic liquids. These should be used whenever a potential exposure to the hands exists, such as during transfer of the liquid.
Liquid carbon dioxide, also used for extractions, requires additional protection against exposure to a cryogenic liquid. The primary hazards here include exposure to a cryogenic liquid and displacement of oxygen. As with an LPG such as butane, waterproof cryogenic gloves are necessary. Infusion The cannabis infusion process involves adding extracted oils to food products, which means that these types of activities must be conducted in a sanitary environment. Although the requirements for use of gloves may vary among state and local health codes, disposable food-grade gloves designed for food handling are recommended. Disposable nitrile gloves are recommended for added protection against dermal contact and absorption of the extracted cannabis oils. HAIRNETS AND BEARD COVERS The cannabis infusion process, which adds extracted oils to food products, must be conducted in a sanitary environment. Standards are set by the National Sanitation Foundation as well as state and municipal health codes. Almost all regulations require that hair nets and beard covers be used when cooking or preparing foods or edibles.
Beyond compliance, common sense dictates that hairnets and beard covers be used. It’s imperative to take obvious, easy preventative steps during production to keep hair away from trimming, packaging, and production operations. SHOE COVERS When growing cannabis, outside contaminants can threaten to ruin the product during cultivation. Mold such as powdery mildew can be tracked in from outside and can lead to the loss of plant material as fungi feed off nutrients from the leaves of cannabis plants. Other potential hazards to marijuana plants are spider mites, hemp russet mites, and rice root aphids, all of which thrive on various parts of the plant. All can eventually destroy the product if left to fester.
A simple and effective way to combat these pests is to require everyone entering grow rooms to wear shoe covers. Mold spores, mites, or aphids can easily be tracked in on shoes. Once they get into grow facilities, it is extremely difficult to eradicate them. Disposable shoe covers, correctly used, are an inexpensive way to reduce the risk of product loss from outside contaminants.
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Respirators or dust masks should be worn when plant matter is ground. Photo credit: Gerson
RESPIRATORS Cultivation facilities must maintain clear guidelines on when employees should use respirators. The risk of inhaling unwanted contaminants from cannabis plants is sometimes overlooked. During harvesting, trimming, or repotting, workers can be exposed to dusts, molds, and allergens that are released when the plant is disturbed. Inhalation of these byproducts can have long-term health complications. Similar risks also exist during size reduction operations when plant matter is ground, which releases excessive amounts of dust and allergens. As a result, respirators or dust masks should be worn during these operations. The report from National Jewish Health found that many agencies (including EPA and law enforcement) recommend:
  1. for minimally to moderately contaminated areas, use of a NIOSH-approved N95 disposable respirator or NIOSH-approved half-face air purifying respirator with P-100 filter cartridges
  2. for heavily contaminated areas with significant mold growth, use of a NIOSH-approved full-face air-purifying respirator with P-100 filter cartridges
Some workers with asthma may be sensitive to mold spores and other allergens in the air. It is recommended that adequate respiratory protection, such as a NIOSH-approved full-face air-purifying respirator with P-100 filter cartridges, be provided.

Monitoring for mold and allergens may also be necessary. EYE AND FACE PROTECTION Appropriate eye or face protection is required whenever workers are exposed to chemical solvents, corrosives, or cryogenic liquids that could damage the eyes or skin. Exposures to cryogenic liquids and highly corrosive chemicals require both eye and face protection.
In addition, eye protection should provide UV protection from the full-spectrum grow lamps common to cultivation facilities.
Safety glasses, goggles and face shields should all meet the ANSI Z87.1 standard for protection. UV PROTECTION (LIP BALMS AND SUNSCREEN) One of the most frequently overlooked hazards to workers is exposure to UV light from the intense grow lights used in cultivation facilities. Long-term risks such as skin cancer and skin-damage can be minimized by having employees cover their exposed skin and by applying UV-protective, high-SPF sunscreens. If exposures to the glow lights are daily and continual, then a sunscreen with a high sun protection factor (SPF) of at least 50 is recommended. Sunscreens should be applied in accordance with the manufacturer’s instructions, with many requiring reapplication at least every two hours. ADDITIONAL PROTECTIVE MEASURES Because many grow operations are indoors and ventilation may not be adequate for production-scale use of solvents, additional precautions may be necessary. Local exhaust ventilation can help control gases and vapors. Fixed or portable monitors for oxygen, carbon dioxide, carbon monoxide, and flammability may also prove valuable, especially during large-scale solvent extraction operations. In addition, some facilities may burn a carbon-based fuel (such as ethanol, butane, or propane) to produce excess carbon dioxide and increase yields, which can displace oxygen and potentially increase production of toxic carbon monoxide concentrations. Ultimately, special precautions should be taken with indoor grow operations to ensure adequate ventilation is provided. JAMES LIEBERMAN, CIH, is the president of THC Safety, Inc., a full-service consulting company for the cannabis industry. He can be reached at info@thc-safety.com and (303) 997-6626. ROB BROWN is chair of the AIHA Protective Clothing and Equipment Committee and president of Gloves By Web, a provider of personal protective apparel and PPE for many industries, including EMT, pest control, and cannabis. He can be reached at rbrown@glovesbyweb.com or (414) 975-7500. ROBERT N. PHALEN, PHD, CIH, is an associate professor of Industrial Hygiene at University of Houston-Clear Lake in Houston, Texas. He can be reached at phalen@uhcl.edu or (281) 283-3753. Send feedback to synergist@aiha.org.
RESOURCES Arcview Market Research: “The State of Legal Marijuana Markets, 5th Edition, Executive Summary” (March 2017).
Colorado Department of Agriculture: “Pesticide Use in Cannabis Production Information” (March 2017).
FDA: Food and Drug Administration Food Code 2013 (PDF, November 2013).
National Jewish Health: “Health Effects Associated with Indoor Marijuana Grow Operations” (PDF, September 2012).
New Frontier Data: “New Frontier Data: U.S. Cannabis Market Creates 283,422 Jobs by 2020” (PDF, February 2017).
Wiley: Quick Selection Guide to Chemical Protective Clothing, 6th Edition (June 2014).
During harvesting, trimming, or repotting, workers can be exposed to dusts, molds, and allergens that are released when the plant is disturbed.
GROWING PAINS
Personal Protective Equipment for Workers in the Emerging Cannabis Industry
BY JAMES LIEBERMAN, ROB BROWN, AND ROBERT N. PHALEN
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NEWSWATCH
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the Synergist
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