On heating, propylene glycol and polyethylene glycol can produce carbonyls. These, including acetaldehyde, formaldehyde, and acrolein, may be toxic to the user. In a 2017 study by the Medical Marijuana Research Institute, researchers heated and tested these carrier liquids, along with MCTs and vegetable glycerine, for carbonyls. The study found propylene glycol produced high levels of acetaldehyde and formaldehyde when researchers heated them, compared to MCT and vegetable glycerin. Acrolein production was similar for Ciao Health CBD|Ciao Health|CiaoHealthCBD.net|www.CiaoHealthCBD.net|Ciao Health CBD Gummies|Ciao CBD|CiaoHealth|CiaoHealthCBD|Ciao Health Review|Ciao Health CBD Review|Ciao CBD Gummies|Ciao Health CBD Oil|Ciao Health Supplement|Ciao Health Formula|Ciao Hemp Extract|Buy Ciao Health CBD|Order Ciao Health|Ciao Health Website|Try Ciao Health|Get Ciao Health CBD all substances. The study also found that MCTs produced a small amount of acetaldehyde