Disposable Cannabis Vape Cartridges May Pose Latent Lead Exposure Risk, Study Finds

Stored cannabis concentrate vaporizer cartridges may pose a health risk to consumers, an early study shared with Analytical Cannabis has found.

After small amounts of lead were noticed during the re-testing of older cartridges, two licensed cannabis processors – Cultivate of Massachusetts, USA, and the Valens Company of British Columbia, Canada – began looking closer at these products. The researchers found that undisclosed lead can leach from the vaporizer hardware into the concentrate, endangering consumer health. 

Now the two labs are collaborating to improve knowledge of product stability and lead leaching, and to educate the industry on how to select safe vaping hardware.

An accidental discovery

Concerns over the safety of cannabis concentrate vaping are not new. In early 2019, dangerous levels of lead contamination in vape products were detected in California. This was found to be down to the use of lead-doped electrical components in the vape hardware, a common practice in the Chinese metal foundries where the majority of vape cartridge components are made.

In response, some US States established limits of 500 parts per billion (ppb) for lead in finished cannabis products. Health Canada has adopted similar limits “within the accepted tolerance limits for human use” from the Canadian Food and Drugs Act.

More recently, the e-cigarette or vape product use-associated lung injury (EVALI) outbreak in the United States has also called the safety of vaping into question. In testing the safety of its products during this EVALI outbreak, one licensed producer made an additional discovery.

“All vape cartridges were quarantined in Massachusetts and labs were busily testing for vitamin E acetate as well as other dilutes,” recalls Dr Francis Boero, head of the Legalized Cannabis and Hemp Edibles working group at the Institute of Food Technology (IFT).

“I noticed that with one client, Cultivate, they had done the right thing. Along with MCR labs (another cannabis testing lab in Massachusetts), Cultivate began to proactively test all quarantined cartridges in their inventory to see if they were still useful.”

“I, as well as the lab staff, began to notice that the longer the vape had been stored, the higher the lead level was in these cartridges,” Boero tells Analytical Cannabis. “And it was quite striking because we could plot these by date. And there was a perfectly linear line marching upwards every month – the THC concentrate was quite pure, very good when it was put in – and after six months you were beginning to approach levels of lead exceeding the state standards.”

The rate of contamination appeared to depend on cartridge hardware as well as the vaporizer concentrate. Some combinations showed excessive lead levels after one month while others were well below state limits after six months.

Boero reached out to other members in the IFT to see if they had noticed similar results, and lab staff from the Valens Company confirmed that they were seeing the same trend. From there the two labs began to collaborate, hoping to discover the cause of this lead contamination.

Undeclared lead in wetted cartridge components may be to blame

Both legally licensed cannabis processors carried out acid solution leaching tests and independently developed their own methods to further investigate the issue. Valens subjected vaporizer wetted parts to further nitric acid digestion for total heavy metal analysis, while Cultivate performed a retrospective analysis of concentrate cartridges that had been stored for up to 340 days.

The labs concluded that vaporizer cartridge hardware may contain undeclared lead in their wetted components. Acid leaching tests returned lead levels in the range of zero to over 1400 ppb, which varied depending on the supplier.

The nitric acid digestion tests carried out by Valens on the vaporizer components revealed undeclared lead ranging between 54-to-6900ppb, which indicated that these parts may well be a likely source for the lead contamination.

The tests run by Cultivate, in which cannabis concentrates were extracted and tested from older stored cannabis vaporizer cartridges, showed a consistent increase in lead content despite the original concentrate being free of heavy metals when it was first packaged. Cartridges in Cultivate’s possession increased from zero to approximately 150ppb over a 340-day period. Other third-party commercial cartridges distributed by Cultivate showed levels of 526ppb after 295 days in storage.

The early study also reported the results of an accelerated aging test performed on cannabis extract-filled cartridges at 52˚C; the lead levels remained below the limit of detection (~50ppb) for time periods corresponding to around 24 weeks of storage at room temperature.

Recommendations for the industry

In the eyes of the World Health Organization, there is “no known level of lead exposure that is considered safe,” which is why the sudden appearance of lead in older vape cartridges is a particularly concerning event.

“It was a very fortunate mistake that, whilst everyone was looking for vitamin E acetate, these two laboratories actually looked further than that,” says Boero. “They went beyond what was necessary. And that data, when applied and looked at in retrospect, showed that there was a latent problem in the cartridges themselves.”

The early study does make a number of future recommendations that could serve to improve the industry’s quality systems and to ultimately protect consumers from this type of latent lead exposure.

Firstly, they ask that licensed processors should establish purchasing controls using pharmaceutical good manufacturing practices for their vape hardware, and that these controls include appropriate sampling plans confirmed by leachate or heavy metals analyses. As the industry currently lacks federal regulation, the study authors also recommend that processors validate the safe shelf life for their filled cartridges, and that these cartridges should clearly list a use-by date.

Recently, one Massachusetts-based cannabis business, Temescal Wellness, has announced that it will be destroying more than 40,000 vape cartridges that have been sat in storage since the state’s temporary ban on cannabis vaping in the wake of the EVALI outbreak. The firm cited concerns over possible lead leaching as a reason behind their decision, despite companies now being allowed to re-test and sell these older products with the ban lifted.

In light of their early findings, both Valens and Cultivate have elected to build on their good manufacturing practice principles and quality testing procedures. The findings have also been shared with the FDA and the independent lab standards organization AOAC International.

“I think that was March 10 of this year,” Boero recalls. “AOAC held a townhall on vaping products and inhalants, with the FDA, Health Canada, and ProVerde Labs to collaborate on testing methods directed toward [improving the] quality of public safety. It was presented, it was discussed, and on March 11 we started to talk about Covid.”

While efforts to improve standardization may be temporarily on hold, the laboratory scientists behind the research are continuing to investigate possible ways to improve consumer safety in the cannabis industry.

“I think personally that there is more to be done to really end up with a final conclusion,” says Houssain El Aribi, PhD, laboratory manager for Valens Agritech. “I have recommended that we plan deeper experiments, with different forms of cartridges as well. We can't focus only on cartridges coming from China, we have to focus on cartridges coming from different parts of the world.”