Cannabis regulators in Michigan are encouraging all licensed cannabis provisioning centers and dispensaries to test their supply of vape cartridges for heavy metal contamination.

A public health and safety bulletin issued by the Department of Licensing and Regulatory Affairs reports that the Bureau of Marijuana Regulation (BMR) found evidence of a lead contamination problem in a number of vape cartridges when the failing test results were entered into Michigan’s statewide monitoring system.

“BMR encourages all licensed provisioning centers to have their vape cartridges tested,” reads the bulletin.

“Patients and caregivers who would like to have cartridges tested, at their own expense, can take them to a licensed safety compliance facility.”





Heavy metals in vaping

Heavy metal contamination of cannabis products usually occurs either through cross-contamination during processing, or by the cannabis plants themselves absorbing metals from the soil they are grown in. There are even a minority of cases where sellers have been caught adding heavy metals to street-sold cannabis in an attempt to artificially increase the weight of the product, and thereby increase its street value. But the manner in which vape cartridges and cannabis e-liquids are produced make these contamination sources unlikely.

Here, the leading theory is that the contamination could be a result of lead metal being used in the production of certain metal components of the vape cartridge, which then leaches into the cartridge’s acidic cannabis oil contents over time. While specific research into this contamination route is scant, there are number of studies which have linked metal contamination of vape contents to the composition of the cartridge metals.

The BMR safety bulletin itself references a 2018 study from the Johns Hopkins Bloomberg School of Public Health that found unsafe levels of lead, chromium, manganese, and nickel in the aerosols created by a number of e-cigarette and vape devices. The researchers found negligible amounts of metals in the e-liquids themselves that were held in the vape cartridges, but much higher levels of metals in e-liquids that had been exposed to the metallic heating coils inside the e-cigarette tanks.

This discrepancy led the researchers to conclude that the metal contamination was almost certainly down to metals leaching into the e-liquids via the metallic components of the heating coil. Though, the researchers noted that while these coils do normally contain nickel and chromium, and a few of the other metals detected, the source of the lead remains a mystery.

A second study referenced in the bulletin, this time from the Roswell Park Comprehensive Cancer Center, published in the International Journal of Environmental Research and Public Health, concerns the study of electronic nicotine delivery system (ENDS) devices for tobacco e-liquids, though the concept is the same for cannabis vape devices. Here the study observed that no bottled e-liquids contained quantifiable amounts of lead, but that e-liquids loaded into certain open-wick ENDS devices showed concerning levels of lead contamination – again, implying that the contamination found in Michigan could be related to metallic vape cartridge components.





Lead contamination in the US cannabis industry

Similar contamination problems were discovered in California at the start of the year when the state brought in strict new cannabis testing requirements, including extensive heavy metal contamination checks. Here the contamination was also put down to metals leaching into the acidic cannabis oils and e-liquids through contact with the metallic components of the vape cartridges.

A significant proportion of the electronics that went into common vape cartridges and e-cigarette refill brands being sold in California were being produced at metal foundries in China, where it is common practice to add lead into metal components to make the components more malleable during the shaping process. Despite the Chinese firms following very strict regulations on the amount of lead that could be added to these components, the practice still resulted in enough contact contamination that the detectable lead levels in vape cartridge liquid exceeded the safety limits put in place by California’s regulators.

The safety bulletin from Michigan’s regulators notes that, so far, no heavy metal contamination has been seen in vape cartridges which use ceramic components, indicating that Michigan could be experiencing the same problem that California encountered. Michigan is one of the few states with some form of legal cannabis that also requires mandatory heavy metal testing on all licensed marijuana products. And no ceramic vape cartridges have turned up this same lead contamination, making metal components a likely culprit.





Are cape cartridges safe?

While recreational cannabis use has been legal in Michigan for several months, a state-regulated marketplace for recreational cannabis is not currently in place, and likely won’t be until 2020.

This public health bulletin from the state is aimed more at the pre-existing medical cannabis provisioning centers and dispensaries which stock vape cartridges as an option for patients, though participants in Michigan’s grey market may also do well to heed this warning.

Exposure to toxic heavy metals, such as lead, can result in significant adverse health effects even in otherwise healthy individuals. The World Health Organization has previously stated that, “There is no known level of lead exposure that is considered safe” and links lead exposure to problems with high blood pressure, joint and muscle pain, headaches or abdominal pain, mood disorders, and impairments in memory and concentration in adults. For medical cannabis patients who already suffer from some form of physical health problem, there is the potential that this combined with lead exposure symptoms could present an even stronger health risk.

After lead contamination was discovered in California, some vape cartridge companies were able to make changes with their supplier to move to lead-free vape cartridge components as a safety precaution. It remains to be seen whether suppliers in Michigan are able to do the same.

In the meantime, the state has updated its testing regulations to require vape cartridges testing for metal contamination after the cartridges are filled with vape liquid, as well as the liquid itself being tested beforehand, as a further safeguard against heavy metal contamination.