You may be inhaling carcinogens roughly equal to smoking a cigarette when you hit a weed vape pen. Cancer-causing agents including formaldehyde and acetaldehyde can be released from cannabis extracts when heated in a vape pen, according to a study from researchers in the cannabis industry and published in the Journal of Alternative and Complementary Medicine earlier this year.

The study’s authors say that the carcinogens are not in cannabis itself, nor even in the sometimes controversial solvents such as butane used in the extraction process. On the contrary, the authors claim that vaporizing marijuana has fewer potential respiratory risks than smoking raw flower. The problem, they argue, is in the thinning agents added to extracts to make them work well in a vape pen.

Vape pens “generally require the cannabis oil to flow easily from the cartridge to the heating element to enable vaporization,” the study states, but unfortunately raw cannabis oil “does not easily flow. Therefore, in a practice borrowed from the e-cigarette industry, many cannabis oil manufacturers combine the oil with thinning agents to improve flow.”

Popular thinning agents are, as you might expect, FDA approved. But they are FDA approved for use in foods, cosmetics, and pharmaceuticals. Many have not been tested under the high temperatures required for vaporization. In these conditions, the agents can release toxic aerosols, which are then inhaled.

One thinning agent in particular was troubling to the researchers: polyethylene glycol 400. PEG 400 is commonly used as a thinning agent in hash oil (this is confirmed by one extraction company we talked to). At a temperature of 230° C (446° F) it releases much, much larger amounts of vaporous acetaldehyde and formaldehyde than other agents. One inhalation at that temperature would give you 1.12 percent of your daily limit of formaldehyde. By comparison, smoking an entire cigarette gives you 1.42 to 2.35 percent, so a person hitting their vape pen all day is potentially inhaling the same amount of carcinogens as a regular cigarette smoker.

That’s pretty alarming, but there are some caveats to these findings. Most of them involve the lack of testing of these effects. The authors of the study are the first to admit that there is a lack of information on the effects of vaporized thinning agents. Because of federal limitations on cannabis research, even they have not been able to observe what happens when PEG 400 is vaporized in combination with cannabis extract, which could change the effects either positively or negatively.

Temperature can also play a big role in the amount of carcinogenic aerosols released while vaping. Lower temps could release healthier vapor, but again more testing would be needed.

Photo via Flickr user Vaping360