A study published yesterday in the New England Journal of Medicine by a team of researchers at the Mayo Clinic provides further evidence that contaminated THC oils are likely playing a major role in the vaping-associated respiratory disease outbreak and makes it even less likely that store-bought nicotine e-liquids are playing any role at all. Here is the key evidence provided by the paper:
1. The overwhelming majority of patients admitted to vaping THC oils.
Approximately 76% of the patients studied who reported on product use admitted to vaping marijuana (13 out of 17 patients). Because urine THC testing was either not conducted or not reported, it is not possible to state that any of these cases occurred in a patient who had not vaped a marijuana-based product. In one case, a patient had been vaping nicotine e-liquids for five years, but then tried vaping marijuana and was in the hospital with respiratory distress within a few days. His vaping history was reported as: "vaping nicotine for 5 years; on weekend prior to presentation, started vaping nicotine with marijuana for the first time."
2. The study authors suspect a direct chemical injury to the lungs, suggesting that a new contaminant, not traditional nicotine e-liquids, is the most likely cause.
After examining the lung biopsies, the authors concluded that the most likely explanation for these cases is "direct lung toxicity from an inhaled noxious agent or agents." The ingredients of store-bought nicotine e-liquids is quite standard. These e-liquids contain propylene glycol, glycerin, water, nicotine, and flavorings. This formula is ubiquitous for all store-sold nicotine e-liquids and there have not been any recent changes to these ingredients. The FDA's testing of the recovered nicotine e-liquids from case patients have so far not revealed any contaminants. These products have been sold for years without reported problems of lung toxicity.
In contrast, black market THC products and counterfeit vape cartridges sold over the internet and by street dealers are very susceptible to contamination. Unlike legal THC oils, the black market products are not tested, and therefore might contain pesticides, residual solvents, other noxious chemicals, or synthetic cannabinoids, each of which could potentially cause a direct chemical injury to the lung.
In fact, acute respiratory toxicity from synthetic cannabinoids has been observed. So has acute alveolar hemorrhage and a more subacute lung injury characterized radiographically by diffuse hazy densities. Moreover, just lack week, testing of a large number of black market THC vape cartridges revealed that they "all contained myclobutanil, a fungicide that can transform into hydrogen cyanide when burned," which can have severe respiratory toxicity. It was also recently shown that vaping butane hash oil can result in severe lung toxicity that presents in a similar fashion to the current outbreak cases.
3. The study findings are not necessarily inconsistent with lipoid pneumonia.
Although the study authors opine that the pathological findings are not indicative of exogenous lipoid pneumonia, the basis for this conclusion is not clear. The authors' assertion seems to be based primarily on their failure to find "coalescent of lipid into large droplets." However, there are many previous reports of exogenous lipoid pneumonia in which the pathology examination did not report finding a coalescence of lipid into large droplets in the lung. The main finding in these previous studies (example) was the presence of lipid-laden macrophages, just as the primary finding in the current study was the presence of foamy (lipid-laden) macrophages. The radiographic findings in many of the cases and the finding of lipid-laden macrophages are consistent with a diagnosis of lipoid pneumonia in at least some of the observed cases. I think it is premature to rule out the significance of the inhalation of large quantities of viscous oil in the pathogenesis of the disease.
The results of this study add to the growing evidence that contaminated black market THC oils or counterfeit, bootleg vape cartridges are the primary, if not sole, cause of the outbreak. In two cases, legally purchased THC oils from dispensaries in Oregon were implicated. However, there are no cases that have been shown to be associated with the use of store-purchased nicotine e-liquids and it seems extremely unlikely that these products have any involvement in the outbreak.