We all know that lead is bad for health, but did you know that it can cause cardiovascular disease, kidney disease, intellectual disabilities, and even affect fertility? Following exposure, lead is absorbed into the bloodstream and then moved and stored in the bones and teeth. As people age, it can be released back into the bloodstream again. Although lead exposure is generally not safe, organizations such as the CDC, EPA, OSHA, and Health Canada have established action limits, or allowable levels of exposure, based on work environments. In the cannabis industry, regulations at the state level are between 500 and 1200 ppb in cannabis products, with Massachusetts, for example, having an action limit of 500 ppb. Dr. Francis Boero of Gavenum and Dr. Houssain El Aribi of Valens have studied how lead from vape hardware leaches out under the slightly acidic conditions (pH = 4) of cannabis extract, and how this has implications on the shelf life and storage conditions of vape cartridges. It is significant that the distillate material is not neutral or basic, such as nicotine, which is an alkaloid, because a decreased pH value can dissolve more metal. The cannabis material happens to be on the side of acidic, because of the functional groups it contains such as phenols.
Because of the EVALI situation, Massachusetts flagged 600,000 vape carts that were non-medical and put them in quarantine on November 12, 2019. The next month, permission was given to sell newly made vape cartridges into the adult market that were made without additives, however, the 600,000 vape cartridges from November were still in quarantine as of March of 2020, when COVID restrictions were put in place regarding adult use cannabis in the state. This gave researchers a unique opportunity to study these aged samples in depth with MCR Labs of Framingham, MA. They tested these quarantined carts for potency, vitamin E acetate, and heavy metals, established a life-cycle profile, and also did leachate testing of the vape hardware. It is worth noting that even some materials such as “lead-free copper” can leach lead in the ppm range because the lead-free specification is for plumbing purposes, not for the purpose of heating with acidic material. To analyze the vape hardware, empty cartridges were filled with a dilute acetic acid solution with a pH of 4, leaching occurred for 24 hours before dilution and analysis by ICPMS.
Ideally, manufacturers should aim to completely remove all heavy metal contamination from any part of the vape hardware supply chain, but for now, studies can be done to show how long a vape could last before the leaching becomes too high. In reality, vapes may also be stored in less-than-ideal conditions, such as a warm car, so accelerated aging methods were done to establish an expiration date of about 6 months. This also takes cannabinoid degradation into account, the conversion of THC to CBN. Although it is possible to store bulk distillate for long periods of time without degradation, distillate is much less stable once it has been converted into cartridges. Overall, they have proven that you cannot verify a vape without having to destroy it.