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Heavy Metals Can Leach into Cannabis Vape Oils and Aerosols, New Study Warns

By Alexander Beadle

Published: Nov 08, 2021   
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More needs to be done to protect cannabis vape consumers from harmful contaminants, researchers say, after a new study detected dangerous heavy metals in the aerosols produced by commercially available cannabis vape products.

Recently published in the journal Chemical Research in Toxicology, the new study from scientists at Medicine Creek Analytics tested vape products from 13 commercial brands, as well as several standard system cartridges filled with different model vape juices. They found evidence suggesting that chromium, copper, nickel, as well as small amounts of manganese, lead, and tin can leach out over time from the vape hardware into the vape liquid, and subsequently into the aerosol produced by the vape.

Concerningly, many of these metals are not currently screened for in areas where vape liquids are required to be tested. As a result, the researchers believe that regulatory requirements on heavy metals testing need to be reconsidered to properly reflect the actual risks presented by cannabis vape products.

Metals found in commercial vape product liquids

For this study, the researchers purchased a number of “model” system cartridges and filled them with either blank concentrate stock, blank distillate, terpenated concentrate, or terpenated distillate. Thirteen different brands of commercially available THC vape products were also purchased. Several of these were disassembled and ground down into smaller pieces, so that the elemental composition of typical vape hardware could be assessed.

Cannabis vape oil tests were conducted on these products before the vape was used, and then again after around two-thirds of the liquid had been vaped away. In the pre-vaped samples, measurable levels of chromium, copper and nickel were found, with small amounts of manganese. However, the levels of the classic “big four” heavy metals that are routinely tested for – arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) – all fell well below regulation limits.

These same metals were detected in the oil samples after vaping, but in generally higher average amounts than recorded pre-vaping.

“The results suggest that the cartridge devices themselves are leaching metals and potentially at higher rates when the components are heated,” the scientists warned.

“Given most states and other regulatory bodies generally only require screening for As, Cd, Hg, and Pb, these potential exposure profiles would pass current regulatory standards.”

Metals can leach from cartridge components into inhaled vapor

The aerosols produced by the commercial cartridges, as well as a model terpenated distillate and a model terpenated concentrate, were also captured and analyzed for the presence of ten different heavy metals: arsenic, cadmium, cobalt, chromium, copper, mercury, manganese, nickel, lead, and tin. While there is no singular accepted standard method for cannabis aerosol analysis – a problem that is rapidly becoming urgent given Colorado’s intention to require aerosol testing in 2022 – the Medicine Creek Analytics team recently published an effective method for screening heavy metals in aerosol, which was also used for this study.

The vape devices were roughly sorted into three groups – the model systems, commercial vapes with a similar cartridge design to the models (“group 1” carts), and a third group composed of varied hardware designs (“group 2” carts) – and the cannabis oils within each were tested by the team.

“Copper, nickel, and manganese were detected in all three groups,” the researchers reported. “Chromium was detected in all groups except the terpenated model systems, and lead was detected in both model systems and group 2 cartridges.”

“Group 2 cartridges generally had higher concentrations overall, but it is unclear if that is due to the difference in cartridge components, or the battery voltage/temperature inconsistencies.”

To confirm if the source of this contamination was the leaching of heavy metals from the vape hardware into the oils and subsequent aerosol, the researchers conducted an additional experiment where six of the model cartridges were filled with unterpenated model concentrate. Three of these were left in a room-temperature oven and the others in a 42 degrees Celsius oven to simulate the hot conditions, such as the inside of a car. The concentrate in these cartridges were removed and tested for heavy metals after three weeks and then again at seven months.

Before being added to the cartridges, the levels of metals present in the concentrate were all below the limit of detection/limit of quantitation values for each metal. After seven months at room temperature, significant amounts of copper and nickel were observed. The cartridges kept at 42 degrees Celsius had even higher levels of these metals, plus notable levels of lead, tin, chromium, and manganese.

The trouble with regulating cannabis vapes

Currently, states which require heavy metals testing for cannabis vape products only test the cannabis vape oil contained within the vape cartridge. Even then, only a very narrow range of metals are actually routinely screened for: ​​arsenic, cadmium, mercury, and lead.

“The cartridge devices themselves generally don’t have those four metals in them. There is sometimes a small amount of lead, but the other three metals generally aren’t found in these vape cartridges,” Dr Amber Wise, scientific director at Medicine Creek Analytics and an author of this new study, previously told Analytical Cannabis.

“So it’s arguable that we should be looking at anything but the big four. In this situation, if we're trying to figure out the contribution of the cartridges themselves to our metals exposure, we should look at what the cartridges are made out of and look for those metals.”

Colorado’s intent to require cannabis vapor testing in 2022 represents a significant step forward for the sector. Instead of exclusively testing unvaped cannabis oils, this testing should, in theory, be far more representative of what consumers are actually inhaling. But the lack of a universally agreed standard method for cannabis vape aerosols testing has led to questions over whether testing laboratories will be able to prepare reliable testing protocols in time for the change.

Even so, the Colorado regulations state that testing “must include, but need not be limited to, testing to determine the presence and amounts of arsenic, cadmium, lead, and mercury,” meaning that any amounts of copper, nickel, and chromium present might still evade detection.

Given this study confirms the presence of other metals outside of the big four being present in cannabis vape aerosols, the Medicine Creek Analytics scientists believe this research demonstrates the need for regulatory requirements to be reconsidered in ways that would better represent the realities of what appears to be present in these oils, and what may present a risk to consumers.


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