Humans have been using cannabis or cannabis products for thousands of years.1 A recent Pew Research Center study indicated that more than six in ten Americans support legalization of marijuana. This level of support has more than doubled since 2000 and has led to a corresponding increase in the number of states that allow the use of medical and/or recreational marijuana.2 Currently, 33 states and the District of Columbia permit such use and many of the states allow marijuana cultivation on a commercial scale.3
This has promoted an entirely new industry – with job descriptions that include cultivator, trimmer, bud tender and extraction technician.4 These positions require close contact with plants throughout their growth and maturation. Cultivation of marijuana can range from a small “closet” operation to facilities as large as twenty football fields employing hundreds of workers.
Health & Safety Hazards
Like many new industries, health and safety issues have to be considered and controls implemented to protect workers. However, very few states or the Occupational Safety & Health Administration (OSHA) have established controls over these workplace hazards. Cultivation of marijuana requires elevated temperatures and high humidity levels in grow houses. Growers’ use of pesticides, herbicides and fungicides to control powdery mildew and other fungi/bacteria is unregulated – unlike in the food industry. Several states have developed strict regulations for the residual levels of chemicals permitted on marijuana buds and products made from marijuana. So, the threat of losing an entire crop has served as a deterrent to indiscriminate use of pesticides.
While many of the health and safety hazards are similar to those of any industry, others are unique to the cultivation industry. Employees who cultivate or trim marijuana may be susceptible to mold exposure due to the 60-80% humidity levels in grow houses needed for optimal growth. This can lead to wheezing, coughing, difficulty breathing, respiratory infections, hypersensitivity pneumonitis, and exacerbation of asthma. One study found several species of Aspergillus in the breathing air – including those associated with acute invasive aspergillosis, as well as bacteria such as Klebsiella, Escherichia coli (E. coli), Pseudomonas and Acinetobacter.
The growth cycle of marijuana plants produces a wide range of “cannabis-related” odors. These are typically complex mixtures of hundreds of volatile organic compounds (VOCs), such as terpenes and terpenoids that are produced along with odorless cannabinoids. About 200 terpenoids have been described in Cannabis and constitute the essential oils in the plant.5 Most of these compounds do not have established exposure standards, leaving it up to the individual grower to provide sufficient ventilation to prevent a buildup of these chemicals.
Direct contact with terpenes, such as limonene and linalool found in marijuana plants and buds, can result in allergic contact dermatitis as well as irritation of the eyes and nasal passages. These may cause itchy skin, hives and swollen, irritated eyes. Repeated exposure can result in progressively strong and abnormal responses.
Other Indoor Environment Issues
Carbon dioxide (CO2) is often used as a liquid gas or dry ice to increase and promote growth and in the extraction process to produce concentrates. Elevated concentrations of CO2 impact the indoor air quality and can result in headaches, dizziness, rapid breathing and elevated heart rate. In small confined spaces, without adequate ventilation, CO2 can also deplete oxygen concentrations.
Many grow houses use supplemental heat to maintain growing conditions. The indoor use of generators, space heaters, salamanders, and diesel- or gasoline-powered equipment can produce elevated concentrations of carbon monoxide and oxides of nitrogen. Carbon monoxide is a colorless, odorless gas that interferes with the body’s ability to transfer oxygen. In elevated concentrations, it can cause unconsciousness or death. Nitrogen oxides cause irritation of the upper respiratory tract and can exacerbate asthmatic symptoms.
Growers that make cannabis products may also use highly flammable solvents, such as butane, acetone and toluene, to extract oils from the plants. The indiscriminate use of these solvents has resulted in many facility fires.
Finally, cleanliness of grow houses is critical to the successful operation of a grow facility. Cleaning chemicals often include disinfectants, such as bleach, isopropyl alcohol and hydrogen peroxide, as well as corrosive acids and bases including hydrochloric acid, nitric acid, sulfuric acid, sodium hydroxide and potassium hydroxide…all of which present certain health and safety hazards.
The Need for Health & Safety Controls
In 2016 and 2017, the National Institute for Occupational Safety and Health (NIOSH) conducted a comprehensive health hazard evaluation (HHE) of a medicinal Cannabis facility.6 NIOSH recommended several engineering and administrative controls. Currently, there are no published standards for allowable exposure limits and no statistics for injuries or illnesses among grow house workers. Many grow facilities are small and may fly under the radar of OSHA or state agencies. As the number of facilities increases, it is likely that there will be greater regulatory attention.
HETI…Helping Ensure Safe Working Environments
HETI’s team of Certified Industrial Hygienists and EHS professionals can conduct workplace exposure assessments to aid in identifying potential worker health issues; design ventilation systems appropriate for specific needs; and provide guidance and support for issues related to marijuana cultivation.
References:
1 Abel EC, “Marijuana, The First 12,000 Years”, McGraw-Hill, 1982
2 “About Six-In-Ten Americans Support Marijuana Legalization” Pew Research Center, October, 2018
3 DISA Global Solutions, Map of Marijuana Legality by State, 2019
4 “Guide to Worker Safety and health in the Marijuana Industry”, Colorado Dept. of Public Health and Environment, January, 2017
5 Russo, EB et al “Cannabis Pharmacology: The Usual Suspects and a Few Promising Leads” Adv. Pharmacol. 2017:80:67-134
6 “Evaluation of a Medicinal Cannabis Manufacturing Facility with Indoor and Outdoor Grow Operations”, NIOSH, June, 2018