Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic compound (a diol or double alcohol) with formula C3H8O2 or HO-CH2-CHOH-CH3. The compound is sometimes called α-propylene glycol to distinguish it from the isomer propane-1,3-diol HO-(CH2)3-OH, also called β-propylene glycol. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”] Propylene glycol is a clear, colourless, slightly syrupy liquid at room temperature. It may exist in air in the vapour form, although propylene glycol must be heated or briskly shaken to produce a vapour. Propylene glycol is practically odourless and tasteless. 
Forty-five percent of propylene glycol produced is used as chemical feedstock for the production of unsaturated polyester resins. In this regard, propylene glycol reacts with a mixture of unsaturated maleic anhydride and isophthalic acid to give a copolymer. This partially unsaturated polymer undergoes further cross-linking to yield thermoset plastics. Related to this application, propylene glycol reacts with propylene oxide to give oligomers and polymers that are used to produce polyurethanes. Propylene glycol is used as a humectant (E1520), solvent, and preservative in food and for tobacco products, as well as being the major ingredient in the liquid used in electronic cigarettes (along with vegetable glycerine and, more rarely, PEG 400). It is also used in pharmaceutical and personal care products. Propylene glycol is a solvent in many pharmaceuticals, including oral, injectable and topical formulations, such as for diazepam and lorazepam that are insoluble in water, use propylene glycol as a solvent in their clinical, injectable forms. Like ethylene glycol, propylene glycol is able to lower the melting point of water, and so it is used as aircraft de-icing fluid. It is similarly used as automotive antifreeze. Furthermore, propylene glycol is a minor ingredient in the oil dispersant Corexit, used in great quantities during the Deepwater Horizon oil spill.
Sources & Routes of Exposure
Sources of Exposure 
Exposure to propylene glycol can occur by:
- eating food products;
- using cosmetics;
- taking medicine that contains it;
- If you work in an industry that uses propylene glycol or products containing propylene glycol, you could be exposed by breathing or touching these substances.
Routes of Exposure 
The major routes of exposure to propylene glycol are:
- skin and/or eye contact
Health Effects [2,4]
The following health effects may be experienced when exposed to propylene glycol:
- May cause slight transient injury of the eye.
- May be absorbed through damaged or abraded skin in harmful amounts. Allergic reactions have been reported.
- A single prolonged skin exposure is not likely to result in the material being absorbed in harmful amounts. Prolonged contact is essentially non-irritating to skin. Repeated exposures may cause problems.
- Negative results have consistently been obtained in guinea pigs studies for sensitisation. Propylene glycol is not considered an occupational skin sensitiser.
- When ingested it may cause gastrointestinal irritation with nausea, vomiting and diarrhoea.
- It may cause hemoglobinuric nephrosis
- It may cause changes in surface EEG.
- Inhalation of a mist of propylene glycol may cause respiratory tract irritation.
- Material has a low vapour pressure at room temperature, so exposure to vapour is not likely.
- Chronic exposure to large doses may cause central nervous system depression.
- Chronic ingestion may cause lactic acidosis and possible seizures.
- As exposure to propylene glycol has no adverse effects on the mother, it should have no effect on the foetus.
- Birth defects are unlikely.
- In animal studies, propylene glycol has been shown not to interfere with reproduction.
- The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified propylene glycol for carcinogenicity.
- Animal studies have not shown this chemical to be a carcinogen.
First Aid Measures
- Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Get medical attention.
- Skin Contact: In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an emollient. Remove contaminated clothing and shoes. Cold water may be used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention.
- Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
- Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.
- Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. If large quantities of this material are swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband.
Exposure Controls and Personal Protection
Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapours below their respective threshold limit value. Ensure that eyewash stations and safety showers are proximal to the workstation location.
Personal Protective Equipment
The following personal protective equipment is recommended when handling propylene glycol:
- Splash goggles;
- Lab coat;
- Vapour respirator (be sure to use an approved/certified respirator or equivalent);
Personal Protection in Case of a Large Spill:
- Splash goggles;
- Full suit;
- Vapour respirator;
- A self-contained breathing apparatus should be used to avoid inhalation of the product;
- Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.
- FDA: The U.S Food & Drug Administration has classified propylene glycol as “generally recognised as safe,” which means that it is acceptable for use in flavourings, drugs, and cosmetics, and as a direct food additive.
- NIOSH: The National Institute for Occupational Safety & Health has established a time weighted average concentration for propylene glycol of 100 ppm (360 mg/m3).
- OSHA: The U.S Occupational Safety & Health Administration has not established a permissible exposure limit for propylene glycol.
- Safe Work Australia: Safe Work Australia has established a time weighted average concentration for an 8 hour workday of 100ppm (369 mg/m3).