Exposure to large amounts of ethylene glycol can damage the kidneys, heart, and nervous system. Both compounds can change your body chemistry by increasing the amount of acid. Both ethylene glycol and propylene glycol are clear, colorless, slightly syrupy liquids at room temperature. Either compound may exist in air in the vapor form, although propylene glycol must be heated or briskly shaken to produce a vapor. Ethylene glycol is odorless but has a sweet taste.
Propylene glycol is practically odorless and tasteless.
Ethylene glycol is also an ingredient in photographic developing solutions, hydraulic brake fluids and in inks used in stamp pads, ballpoint pens, and print shops. It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products. It is a solvent for food colors and flavors. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. Neither compound is likely to exist in large amounts in air.