Terpenes are like the herbs and spices of concentrates. They are what gives it flavor, and can affect the high too. But some terpenes may actually might actually make your concentrates way less healthy, according to a new study from Portland State University.

When researchers tested the toxic level of terpenes cooked at various dab-like temperatures, they found high levels of toxic degradation products, including methacrolein and benzene.

Benzene is considered one of the planet’s biggest pollutants, but its presence in vaporized terpenes is much greater than what’s found in ambient air. The effects of methacrolein, the study says, are not fully understood in humans, but the chemical is structurally similar to other known  powerful pulmonary irritants and has been shown to harshly inflame the respiratory tracts of mice.

The problem is not so much that dabbers are inhaling carcinogens every time they lean over an oil rig. The problem is that, since the chemical effects of vaporized terpenes has been studied very little, and terpene chemicals and vaporization temperatures vary so much from sesh to sesh, no one really knows what the health effects will be years down the line.

Plenty of pharmaceutical drugs that have been rigorously tested have turned out to have unknown health risks. For instance, the sometimes fatal side effects of the first approved oral contraceptive were not known until nearly a decade after it went on the market.

“Given the widespread legalization of marijuana in the USA, it is imperative to study the full toxicology of its consumption to guide future policy,” said Rob Strongin, a Portland State professor who led the study. “The results of these studies clearly indicate that dabbing, while considered a form of vaporization, may in fact deliver significant amounts of toxins.”

This is not the first time a study has linked carcinogens with dabbing hash oil. Another report published in the Journal of Alternative and Complementary Medicine earlier this year found harmful toxins present in the thinning agents used to create vape pen oil. Though the chemicals used in thinning agents had been approved by the FDA, they had not been thoroughly tested when vaporized. In that state, the study found that some hash oils release formaldehyde levels consistent with those found in cigarettes.

The health risks of terpenes and hash oil thinning agents have not yet been tested enough to know their full effects. Terpenes are also used in e-cigarette juice.

Photo by Flickr user Will Fisher