About a month ago, Kevin McKernan, the founder and CSO of Massachusetts-based Medicinal Genomics, which also produces the CannMed conferences, posted online a rerecording of the Endotoxin on Cannabis presentation he gave at the CannMed Innovation & Investment Summit held in May at Marco Island, Florida. The talk was based on a December 2023 study by McKernan et al that looked at High Levels of Endotoxins in Commercial Cannabis Flower. Cannabis Business Executive wrote about the endotoxin inquiry in an April 2024 article titled, Is Remediation Safe?
Some slides were missing from the original CannMed presentation, so McKernan decided to rerecord it in full in order to provide a complete picture of the inquiry by the Medicinal Genomics team into this overlooked subject. The result is a revealing and edifying 30-minute journey into questions that were inspired by the untimely death in January 2022 of Lorna McMurrey, a worker at a Trulieve manufacturing facility in Holyoke, Mass., who, according to a federal inspection report, “was packaging ground cannabis into prerolls at a commercial cannabis processing facility [when she] suffered an asthma attack and later died in the hospital.”
As such, the inquiry into endotoxin and resulting presentation is an attempt by McKernan and his team to solve a real-world mystery about the microbiologic factors that may have contributed to a death. “So, what motivated this,” McKernan asked rhetorically five minutes into the video. “A couple years ago, there was a cannabis fatality at a trimming facility here in Massachusetts, and this fatality started a lot of questions online as to how someone who was known to be a cannabis user died of an asthma attack in a trimming room,” he explained. “She had an asthmatic reaction and died on the scene. Horrible situation.
“Everyone was assuming it was mold,” he continued, “and so we were getting dragged into this discussion as well, and the CDC came in and started looking around for spores and for endotoxins. We thought those were interesting, because no one in the cannabis industry is looking for endotoxin, but the endotoxin was actually a really important thing to look for, because if you look at the literature, you’ll find that endotoxin can actually trigger asthmatic reactions like this.”
McKernan provides a fascinating look into the good and bad bacteria found on commercially available cannabis products as well as the inner workings of the Massachusetts market. According to the report, whose opening five minutes are spent explaining what endotoxins are and how they are identified in cannabis, most of the commercially available flower in Massachusetts is irradiated prior to being lab tested. Truth be told, it would certainly help to have a PhD in microbiology, or even an undergraduate degree, to understand a lot of the science being discussed here, but even for a civilian the roadmap of research deftly laid out by McKernan presents a clear and convincing enough case for the presence of high amounts of endotoxin in commercial cannabis.
“The thing to know about cannabis is that about 40 percent of the bacteria in cannabis is known to be gram negative,” he added, referring to a previous study. “This has been published by Green et al, and it is something that we wanted to confirm ourselves because we have a rich database of cannabis microbiomes that we can go and assess whether we are seeing this in the samples that have been sequenced in the past. But that’s an important data point, that a lot of the bacteria on cannabis is expected to have gram negative bacteria, and therefore expected to have endotoxin.”
Utilizing a database with about a thousand cannabis samples that have been whole genome shotgun sequenced by Medicinal Genomics, McKernan explained of the results, “When you do this, you get a really nice breakdown of all the different organisms that are present, and you can begin to classify those organisms as to whether they’re gram negative or gram positive, just bioinformatically, and we’ve done that, and we come up with similar numbers [as Green et al], maybe a little bit higher, with gram negative strains that are on cannabis plants.”
Postmortem
McKernan also provides a rather extensive explanation of the necessity and efficacy of HVAC in cannabis manufacturing environments, especially when compared with masks, which McKernan posits are useless in certain circumstances and could even make matters worse for vulnerable populations. “You don’t mess around with masks, because masks, in general, don’t work with really small particle sizes,” he said. In the McMurrey incident, he noted, the company reacted appropriately considering the unknown nature of the problem they were facing.
“The employer did the right thing, and they quickly responded by changing out the HVAC, and you’ll see why that’s an important thing to do when you don’t know what the pathogen is,” said McKernan. “By the time the CDC got there, they were making measurements for endotoxin after the new HVAC was in and they found levels to be below what is a DECOS limit. OSHA got involved in this as well, and this got us digging through the literature as to how common this is. This has been published before. Are there any other cases of this?”
Their findings identified known risks. “There are other studies done in other states where they’ve gone and looked at what are the endotoxin levels in trimming rooms, and these came back showing that 40 percent of the employees are exposed to endotoxin levels that exceed the DECOS limits,” noted McKernan, adding, “The DECOS limits came out of the Netherlands, [which has] done a lot of work on this, and they test around 90 EU endotoxin units per cubic meter.”
“Total aerobic count test came back with equivalent endotoxin test, and they were orders of magnitude over the DECOS limits,” noted McKernan. “On all the flower surveyed, we’ve yet to find flower that doesn’t have endotoxin. In fact, I don’t think we found one yet that’s below the DECOS limit. So, they are very high.”
Following an array of assays to determine the amount and type of gram negative versus gram positive bacteria found on tested material, the consequence of decontamination practices comes into sharper focus. “The decontamination the states and the growers are doing is certainly lowering the viable microbial count, it lowers the DNA a little bit, but not all the way to the floor,” explained McKernan. “Even if you use these nucleases, there’s still some samples that are positive on qPCR, but would pass on plating, but the endotoxins are everywhere.
“This is something we’ve got to consider if we’re going to get into this world of really strict regulations on microbials,” he added. “It pushes grows into a corner where they have to use decontamination everywhere, and that can be a bit of a double-edged sword, because the moment grows know they’re going to be decontaminating everything, they don’t have to have clean grow practices. They can grow really, really dirty material with very, very high endotoxin levels, knowing they’re just going to irradiate it at the end, and then we still have a health risk that’s present that doesn’t get mopped up with the decontamination that just counterfeits your viability test, if you will.”
McKernan reiterated, “The plating systems are blind to these risks, and we should really, in our opinion, be pushing for labeling of samples that have been irradiated in some way.” One suggestion would be to label how the sample tested before cleanup versus after. “If it’s in the millions of counts and they radiated their way to cleanliness, well, that doesn’t mean the product’s safe,” noted McKernan. “It would be really important to have user transparency here, so that the consumer understands, ‘Okay, this is something that was irradiated into safety.’”
As inadequate as current practices may be, McKernan closes out his presentation on an upbeat note, reminding readers of a paper by Punja on genotype specificity finding that the genotypes of the cannabis plant play a role in total yeast and mold content. “There’s a way to grow our way out of this without having to grow plants that have high burden and then radiate them,” said McKernan. “The practice is known. People can do this. You don’t necessarily need to be dependent on radiating your way out of this problem.”
McKernan also included in his presentation a paper by Tess Eidem that was published after his CannMed talk. He remarked that Eidem has “put together some really important messages in terms of not just endotoxin, but other bioaerosols that could be playing a role in these grow environments. We don’t mean to pin everything on endotoxin. This is just something that we happened to measure. We were quite shocked at how high it is in all the plant, and that leads us to believe it’s an unappreciated risk factor if we’re moving into a world where people are going to grow dirty and mop up later.”
In addition to a number of confounders, the presentation includes the following conclusions:
Endotoxin is present at levels that Exceed DECOS limits (by orders of magnitude) on most cannabis; Remediation hides this risk; Labeling of cannabis products fir remediation is needed for asthmatics; Environmental confounders with Spike protein; Orthogonal Mass Spec assays should be developed to confirm LAL; Aerosols need to be tested.The rerecording of Kevin McKernan’s CannMed 2024 presentation on Endotoxin on Cannabis can be found here.