What is Propylene glycol ( PGP or PEG) and why should I ask if it’s in my cannabis oil?

Propylene glycol is a solvent found in many cannabis oil cartridges and has been shown to be a pulmonary toxin when heating. PG has several hazardous byproducts at high temperatures, including formaldehyde. Happy Valley is committed to selling only propylene glycol-free  and vegetable glycerin-free products.