There are many speculations circulating the media to deem Propylene Glycol as a carcinogenic chemical used in a form of anti-freeze, Propylene Glycol has many useful functions including anti-freeze (because it lowers the freezing point of liquids) and it is used as a less harmful alternative to other common forms of anti-freeze such as Ethylene Glycol. Propylene Glycol is used in various application as a non-toxic and safer solution to using Ethylene Glycol. The FDA has listed propylene glycol as 'Generally Recognised as Safe' where there is mild side effects when in contact with the human body. Some people may have a reaction such as skin irritation or some irritation in the lungs if inhaled. The MSDS report recommends avoiding direct handling which is generally recommended for other chemicals and will always require safety precaution however low the toxicity is, for example; handling cough syrup or using eye drops, 'if irritation persist, please consult your GP'.
'An interesting fact about propylene glycol is that it is non-toxic when ingested even in reasonably large amounts. Unlike its dangerous and frequently lethal cousin, ethylene glycol, PG is easily metabolized by the liver into normal products of the citric acid metabolic cycle, which are completely nontoxic to the body. Approximately 45 percent of any ingested PG is excreted directly from the body and never even comes into contact with the liver. The elimination half-life for propylene glycol is approximately four hours, and there is no bioaccumulation (buildup in the body over time). A few rare incidents have occurred where a person ingested a large quantity of propylene glycol and suffered some liver and neurological effects as a result, but these were short-lived and subsided once the material was metabolized and excreted.'Tonya Mckay (Naturally Curly, The Truth And Fiction of Propylene Glycol)
METABOLIC CYCLE FOR PROPYLENE GLYCOL:
Propylene glycol → lactic acid → pyruvic acid → CO2 + water
Vegetable Glycerin is mainly used in the food industry due to it's sweet taste and has fewer calories than sugar and doesn't have a dramatic effect on blood sugar levels, nor does it contribute to tooth decay. It's mainly used to prolong moisture from the air and has a slower metabolising rate then sucrose - mainly found in candy. Vegetable Glycerin is also commonly found in cough syrup.
Food flavouring can be added to energy drinks, cookies, coffee and used in other baking ingredients to add certain taste. Every flavour has a different chemical structure to give it a distinct taste. Flavours are prepared or extracted using chemical methods that has similar molecules found in nature, e.g vanillin obtained from vanilla pods. There are also artificial flavouring that are added to sweeten the taste of natural flavours such as ethyl maltol. Artificial flavouring uses identical molecular chemical structures to form a certain taste to what is found in natural food, for example if you smell and taste an apple, there is a chemical bond in the apple that gives it that distinct flavour.