This story first appreared at Marijuana Business Daily.

As cannabis vaping pens grew in popularity in late 2019, concerns grew about the safety of the products, spurred by reports of <a href=”https://mjbizdaily.com/vaping-crisis/”>illness, and even deaths</a>, of tobacco vape users.

Vape manufacturers rushed to assure regulators and consumers their products were safe, despite having no clear understanding of what ingredients might actually be dangerous.

Two of the suspected ingredients were phytol and propylene glycol, both of which can be used as thinning agents for cannabis extracts.

Now, a new study published in Inhalation Toxicology, the journal of the International Forum for Respiratory Research, has shown that phytol might be <a href=”https://www.tandfonline.com/doi/full/10.1080/08958378.2020.1867260″ target=”_blank” rel=”noopener”>significantly more toxic</a> than propylene glycol.

Phytol, a terpene best known for its presence in green tea and a promising antioxidant, is found in high amounts in some cannabis varieties.

Propylene glycol is a diol compound that is often used as a carrier in vapes because of its ability to produce smokelike vapor when aerosolized.

Researchers exposed male and female rats to 5 milligrams per liter of phytol or propylene glycol for periods of up to six hours over a span of up to two weeks.

The rats exposed to phytol showed several severe clinical signs, including weight loss and death. Lung weights were increased and respiratory tissue was seriously affected.

The phytol effects were so pronounced the trial for those rats was halted.

The rats exposed to propylene glycol showed no adverse reactions after 14 days of high-dose exposure.