Lipids are fats, oils, and waxes. Their basic unit is the triglyceride, which is synthesized from glycerol and fatty acids. Phytocannabinoids are lipid-soluble terpenophenolic compounds in cannabis. Oral administration of cannabinoids with lipids (or dietary fat) enhances absorption. [2,3] Inhalation of plant lipids, on the other hand, may damage lung tissue and lead to illness. It is for this reason that lipid levels should be labeled on cannabis extracts.
Although very rare, there are cases of exogenous lipoid pneumonia (ELP) resulting from the inhalation of cannabis extracts.  ELP is caused by accumulation of lipid material in pulmonary alveoli. It is associated with inhaling petroleum-based fluid, such as that used by professional fire-eaters. Chronic use of oil-based products is a key predictor for the condition.
There are misconceptions that the inhalation of plant lipids is safe. Some believe that the carbon chains in plant lipids are not long enough to cause a problem in the lungs, but oil pulling (washing the oral cavity) with vegetable oils has been linked to ELP.  Another misconception is that extraction leaves only beneficial plant compounds in the final product. Commercial operations remove most plant lipids through post-extraction processes like winterization. But Romano & Hazekamp (2013) found that hydrocarbon solvents (like butane) leave residual contaminants in the final concentrate.  Cuticle wax may survive dewaxing or winterization. The rarity of ELP cases is the typical defense regarding the harmlessness of lipids in extracts, but lung damage may occur under the radar. There is a near-complete gap in research regarding lipid levels in extracts meant for inhalation.
In the event that extracts contain significant levels of plant lipids, inhalation would present risk. The long-chain and medium-chain fatty acids so beneficial for oral administration can be dangerous when stripped from plant matter and inhaled. Those with major business interests at stake are not always inclined to worry about residual lipids and contaminants.
Dietary information, including saturated fat, provides insight for diet-conscious individuals – total fat is a current label requirement for edibles in California and several other states.  Labeling lipid content on extracts intended for inhalation would serve as an assurance of proper dewaxing/winterization, and verify purity and pulmonary safety.
The American Oil Chemist Society (AOCS) is one organization with a special interest in cannabis testing and analysis for consumer safety. The AOCS aims to boost testing for residual solvents, heavy metals, microorganisms, pesticides, and cannabinoid/terpene content. The lack of federal legality and regulation has left these product characteristics and safety concerns as top priorities. Right or wrong, it is likely that lipid testing and labeling will have to wait in line.
- Brenneisen R. “Chemistry and Analysis of Phytocannabinoids and OtherCannabis Constituents.”Forensic Science and Medicine: Marijuana and the Cannabinoids. Edited by: M. A. ElSohly. Humana Press Inc.: Totowa, New Jersey, 2007.
- Zgair, A., et al. “Oral Administration of Cannabis with Lipids Leads to High Levels of Cannabinoids in the Intestinal Lymphatic System and Prominent Immunomodulation.” Scientific Reports.2017,7/1. doi:10.1038/s41598-017-15026-z. Times Cited = 6, Journal Impact Factor = 4.122
- Zgair, Atheer et al. “Dietary Fats and Pharmaceutical Lipid Excipients Increase Systemic Exposure to Orally Administered Cannabis and Cannabis-based Medicines.”American Journal of Translational Research.2016, 8/8/3448-3459.Times Cited = 17, Journal Impact Factor = 2.829
- Vethanayagam, D., et al. “Exogenous Lipid Pneumonia Related to Smoking Weed Oil Following Cadaveric Renal Transplantation.” Canadian Respiratory Journal. 2000, 7/4/338-342. doi:10.1155/2000/248915. Times Cited = 25, Journal Impact Factor = 1.016
- Kuroyama, M., et al. “Exogenous Lipoid Pneumonia Caused by Repeated Sesame Oil Pulling: A Report of Two Cases.” BMC Pulmonary Medicine. 2015, 15/1. doi:10.1186/s12890-015-0134-8. Times Cited = 9, Journal Impact Factor = 2.721
- Romano, Luigi L & Hazekamp, Arno. “Cannabis Oil: Chemical Evaluation of an Upcoming Cannabis-Based Medicine.”Cannabinoids. 2013, 1/1/1-11. Times Cited = 36
- Barrus, D., et al.“Tasty THC: Promises and Challenges of Cannabis Edibles.” Methods Rep RTI Press. 2016. doi:10.3768/rtipress.2016.op.0035.1611. Times Cited = 8
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