Examining the cases of multiple individuals who were hospitalized for various respiratory issues, this Rolling Stone article points out the inherent danger in using counterfeit cannabis vape cartridges. The piece notes how patients who were admitted, purportedly due to illness caused by these fake products, presented with symptoms of severe acute pulmonary disease, coughing, shortness of breath, and sometimes fever or vomiting.
The article points out different avenues through which these products are winding up in the hands of cannabis users. Some are simply bootleg THC cartridges, made by fake brands, and sold by unlicensed dispensaries. These vapes, made by illegal business don't go through the testing required by various states which check for contaminants such as pesticides and heavy metals.
Another, more disturbing, route for fake cannabis products is the counterfeit market. In these cases, illegal manufacturers are buying labels, packaging, and stickers of authenticity that look like real brands; filling pens and cartridges with their own products; and passing them off as the real item. While it's relatively simple to check whether a brand is real or not, it's far more difficult to discern if what appears to be a real brand's packaging is filled with real product.
As noted in the article, "users will share tips for how to discern bootleg cartridges from ones from licensed dispensaries, such as analyzing the consistency and texture of the oil (it should be fairly thick and move slowly when the pen is turned upside-down), as well as whether the cartridge has a certificate of analysis (COA), which often includes a batch number to cross-reference with the brand’s website. But this is by no means foolproof, as black-market dealers have been known to label their products with fraudulent stickers..."
Realistically, it will take the efforts of legitimate brands, working with experts in anti-counterfeiting and packaging, to find real solutions which will protect consumers. Until this happens consumers will continue to be at risk of buying fake, counterfeit, and potentially hazardous products.