As the legal recreational cannabis industry expands, regulators and safety watchdogs are taking a closer look at how the industry polices itself.
While the legal cannabis landscape for adult use expands to include new states, most recently Maryland and Minnesota, cultivators are undergoing fine-tooth scrutiny about how they grow and process the plant, and what a more diverse consumer market expects for the safety of their cannabis. As is often the case when an emerging industry goes under the research microscope, there are some newly discovered concerns amidst the product processing developments.
There are growing controversies about how the plant is grown and processed. For example, cannabis cultivators and their crews have been experiencing occupation illnesses from processing the product—key among them are respiratory issues, asthma attacks, and even death.
At 11 p.m. on January 7, 2022, an employee who was packaging ground cannabis into pre-rolls at the Trulieve dispensary in Holyoke, Massachusetts suffered an asthma attack and later died in the hospital (1). The Occupational Safety and Health Administration (OSHA) fined the facility $35,219 (2). Trulieve closed its Nevada operations a month later; they closed their Massachusetts operations a year later (3). They still own and operate 17 cultivation and processing facilities in seven different states.
There are other worker and health regulations that may apply to the cannabis industry, as noted by the California Department of Industrial Relations Division of Occupational Safety & Health unit, including electrical hazards, flammable liquids and gases, heat illness, repetitive motion injuries, and more (4). But not all cultivators are required to follow those guidelines.
According to a blog by two Delaware lawyers (5), OSHA, who did an inspection of the Trulieve facility on January 11, was taken to task for claiming that the reason for the asthma attack that caused the death of one of their workers was due to “general cannabis dust” (GCD), which OSHA said was a hazardous chemical. But no determination of GCD as a hazardous chemical exists. Trulieve entered a voluntary agreement with OSHA to determine whether ground cannabis dust is required to be classified as a hazardous chemical, according to OSHA regulations (6). OSHA reduce their fine by half as part of the agreement (7).
This column discusses new worker health and safety issues in cannabis cultivation, causing cultivators to take a closer look at their operations, and how more science is being brought to bear on slowing the effect that a latent viroid disease is having on the grows of cultivators around the country and the world.
In its hazard alert letter (8) about the Holyoke tragedy, OSHA cited an article that outlined the possible health safety effects for cannabis workers (9) at a cultivation facility. The article by Dr. Coralynn Sack (10) and four other researchers at the Department of Environmental and Occupational Health Sciences, University of Washington in Seattle, reported on a study of a small indoor grow facility in Washington State which involved mostly daily cannabis users. “Regardless of the underlying route of sensitization, participants reported a high rate of work-aggravated symptoms, implying that occupational exposures to cannabis or other workplace substances may have either caused or exacerbated health complaints,” the report concluded. “A better understanding of the occupational hazards and health risks is urgently needed, particularly given the rapid expansion of cannabis cultivation.”
Dr. Sack explained to us that what stood out to her was the high prevalence of people who were reporting work-related symptoms and respiratory symptoms, and a high rate of sensitization to cannabis. “All the employers I've spoken with have been extremely engaged, wanting to ensure that the appropriate safety protocols are in place,” said Dr. Sack. “I think there needs to be involvement. I think action needs to happen now.”
She added that there's a lot of collaboration between the states right now because they recognize that this is a growing industry with the potential of a multitude of different work hazards. “We know a lot from other agricultural industries,” she said. “The same types of workplace controls will work here, especially for things that generate a lot of aerosol dust, ensuring we have good local ventilation systems, ensuring that when they have people doing those particular jobs they have appropriate respiratory protection and good education programs so that they understand what the potential risks are. All those are standard safety practices (from agricultural industries) could be applicable here.”
Dr. Sack and her research group are just starting a new major study about cannabis and worker health, where they are hoping to visit 15–20 different grow facilities and work with about 120 workers.
While research about cannabis workers handling and processing continues, there are still issues to be discovered about the plant itself—mysteries to solve—that may contribute to why it’s making people sick.
Aside from the respiratory symptoms related to inhaling cannabis dust, Dr. Sack said sensitization tests suggested that there may be something in the plant protein itself that people are becoming allergic to. “Studies predominantly out of Europe have shown that people can form antibodies to specific proteins in the cannabis plant. So there's definitely a need for us to understand what the process is, what's causing these symptoms, and try to disentangle it so that we can provide better guidance for both regulators and employers to protect workers,” said Dr. Sack.
Another mystery of the plant is how to develop new cultivars with desirable cannabinoid profiles, high productivity, pest resistance, and overall vigor, according to an editorial by researcher Rachel Backer (11,12), working with McGill University, along with four other Canadian and Italian researchers. Polyploidization—or the multiplication of a complete chromosome set of a certain species to give birth to a new species (13)—has been used successfully in hemp breeding. But it has not been attempted in cannabis. “We are a long ways from where you can confidently pick a cultivar from a reputable breeder and know what it is,” said Backer. “The science is clear that an OG Kush from one grower may be completely different from one made from another grower. And they may have two completely different names that are actually genetically identical cannabis strains. It's very unusual compared to other agricultural markets and commodities.”
Cannabis in nature is a very diverse crop, Backer explained. “This means that, as scientists, we have a lot to draw upon in terms of breeding, whether or not that's related to support production, related to flowering time, or related to chemovars or flower structure. So until we're able to produce genetically uniform seeds it just means that you're constantly sorting through which plants you may want to propagate and which ones are going to give you the best yields and the best characteristics,” said Backer.
There's this notion that came on strong in the last 10 years of plant biology about understanding how things are more than a sum of their parts, Backer stated. “I think cannabis is such a perfect example of that,” she said. “Even if you have the exact same genotype, if you vary the production conditions, you may still get a different product.”
She made the comparison to wine production, where, for example, 2018 was a great year and 2019 was not a good year—from the exact same vineyard. “I think understanding where those features are both within the genetics of the plant and also within the environmental conditions that you're using for production, and actually collecting all of that data and fully understanding it, is a 10 year project,” she said. “There are so many variables. You just need enormous amounts of data.”
One of her findings was that plant yields could be positively influenced by plant growth-promoting rhizobacteria (PGPR), which have contributed to yield increases in other cultivated crops. For example, members of Bacillus (14) or Pseudomonas (15) may improve cannabis and hemp yield or quality via direct growth stimulation, improved nutrient acquisition, and biological control of pathogens.
Research has demonstrated that inoculating plants with plant-growth promoting PGPR or treating plants with microbe-to-plant signal compounds can be an effective strategy to stimulate crop growth, according to another article by Backer (16). These strategies can also improve crop tolerance for the abiotic stresses (such as drought, heat, and salinity), which are likely to become more frequent as climate change conditions continue to develop.
This discovery has resulted in multifunctional PGPR-based formulations for commercial agriculture, to minimize the use of synthetic fertilizers and agrochemicals.
There’s good bugs such as PGPR as well as the kind in the human gut (17). And there’s bad bugs such as the aspergillus fungus, one of the most common mold species found in most cannabis grow facilities, which causes localized infections, allergic responses, and fatal respiratory fungal infections. Inhaling aspergillus fumigatus spores (conidia) into the lungs may cause multiple diseases, which depend on the immunological status of the host in humans. These diseases include invasive pulmonary aspergillosis, aspergilloma, and different forms of hypersensitivity diseases such as allergic asthma, pneumonitis, and allergic bronchopulmonary aspergillosis, as spelled out in a study from Iranian researchers (18).
However, there are even worse bugs such as hop latent viroid (HLVd), now found in nearly all cultivations across the country which affect the plant—but not the human consumer, at least as it’s currently understood. A recent article (19) about the viroid reported on a survey conducted in 2021 by Dark Heart Nursery Research (20), in Oakland, California, involving 200,000 tissue tests, and concluded that 90% of cannabis-growing facilities in California were contaminated with HLVd.
Researchers found out that the viroid infection could significantly affect the plants’ vigor and yield. It has been estimated that it could cause losses of up to $4 billion annually for the cannabis industry, in part because HLVd-infected crops could suffer anywhere from a 50–70% loss in tetrahydrocannabinol (THC) content, considerably lowering the commercial value. Now the race is on to kill the viroid . . . or at least slow its infection growth.
One solution may be through the RNA enzyme, according to Zamir Punja, a professor of plant biotechnology at Simon Fraser University near Vancouver, British Columbia (21). “We can at least demonstrate that the RNase is not super invincible,” said Punja. “There are things out there that can destroy (the viroid) vis-a-vis the enzyme. The problem is, if we were to put this into a practical perspective, where we'll be able to identify such an enzyme, how would we get enough of it to actually use it as, for example, a cleaning agent, or as a surface disinfectant. So we're looking at microbes and other organisms that could produce similar enzymes.”
Bacteria get infected by viruses in nature, and develop mechanisms to protect themselves from these viruses, he explained. As the virus tries to enter the bacterial cell, the cell secretes enzymes to basically break down the virus. “So my first search is to see if we can find naturally occurring bacteria or microbes that are secreting the type of RNase enzyme that is needed, which is RNase III,” said Punja.
But buying the enzyme and applying it would be completely cost prohibitive, he added, costing thousands of dollars for 1 g. “Something that produces it naturally would be useful,” he said.
While HLVd is found mostly in indoor grows, where he has done the majority of his work, Punja said he is seeing more cases in outdoor grows as well. “It is found at a lower level outdoors,” he said. “Most of it, I think, originated from the seed. So there's definitely a seed transmission aspect that growers need to consider. Not just for cannabis, but also for hemp.”
Punja talked about a hemp grower who had started seed indoors, got the plants germinated, then transplanted them out in the field and spaced them out really well. “So unlike hydroponics, if growing is spaced out in an outdoor grow instead, you won't see that plant-to-plant spread of the viroid. And there's not water flowing through it, and the roots aren't touching one another. But if (the infection) did start with seed, I think you will find a certain percentage of infection in outdoor plants. You wouldn't see outdoors what we're seeing indoors, where plants are clustered together, sitting on the bench, sharing the water system or using recycled water,” he explained.
He said that bleach is still the go-to product right now, not just for the tools used to process the cannabis but for surface disinfecting. “We haven't looked at treating water. You've got all this recycling water. What do you do with that? The other thing we've looked at that's really encouraging right now is hypochlorous acid (22). There are claims that it works,” said Punja.
He doesn’t know how much parts-per-million of hypochlorous acid to add to water to treat it. Too much and it could make the water like a swimming pool that just stinks of chlorine. “You can't use it that way. There’s got to be some way we can inject hypochlorous. But not enough to kill the plant,” said Punja.
Understanding the diversity of the plant, its true origins, and its genetic makeup is an ongoing goal of researchers as they seek to develop more protocols for growing and processing this ancient plant. Safety is becoming more of a top concern.
The hop latent viroid has emerged as a real head-scratcher, gaining momentum within cultivations. Punja has discovered that there are some strains that are less susceptible to HLVd. “So I started testing a whole bunch of strains, not just to see how they respond, but to try to understand what the plant is doing to minimize the infection,” he said. “Is it not getting infected? Or is it getting infected but it's not allowing it to spread? Those are two key things. Maybe it doesn't move as fast out of the roots up into the flowers in a resistant or tolerant plant. And how do you measure that? So that's kind of what we're trying to wrap our heads around. Is it a movement thing?”
The viroid is definitely spreading once it's introduced, Punja explained. “Then it moves around in a facility. So the way to prevent that is to find these plants that are the mother plants, and if they are super infected, just get rid of them. So we did that in one facility. But then all of a sudden, sometimes, two months later, there's a huge spike in the number of plants that are infected. ‘What happened?’ Well, somebody brought in some genetics that hadn't been necessarily tested, and they put it out on the greenhouse floor, and all of a sudden, the water started spreading it. So you get these outbreaks because of either poor management or unanticipated events, because when you've got a large facility there are different people doing different things.”
But there is good news, according to Punja. “There's not a lot of variation (in the viroid) right now. And hopefully this viroid is stable, with just one strain, maybe two, unlike COVID which mutates all the time. I’m hoping we just get rid of it.”
David Hodes has written for many cannabis publications, and organized or moderated sessions at national and international cannabis trade shows. He was voted the 2018 Journalist of the Year by Americans for Safe Access, the world’s largest medical cannabis advocacy organization.
Hodes, D., Cultivators Address New Health and Safety Issues for Plants and Workers, Cannabis Science and Technology, 2023, 6(8), 20-23.