Monopropylene Glycols

Monopropylene Glycol (MPG): Features

With its unique combination of properties MPG supports many uses.

It serves as a solvent
It dissolves and stabilises water-insoluble substances (emulsifier)
It helps to suspend and transport other substances (excipient)
It attracts/holds water/moisture (humectant)
It reduces the freezing point (antifreeze)
It increases the boiling point
It has very low volatility
It offers outstanding stability with high flash and boiling points
It is biodegradable in the environment.

MPG is chemically non-reactive i.e., it usually does not react with other substances. This is a particularly helpful property in combining non-miscible chemicals, for example in a perfume, to create a single, homogeneous mixture.

By emulsifying active ingredients, which otherwise would not mix, MPG helps to create a stable homogeneous mixture to improve texture and consistency allowing for the intended final product, such as a face cream or shampoo to perform its function.

Monopropylene Glycol (MPG): Production

Simple Process

Chemically, MPG has a very simple structure (obtained from PubChem). Carbon (C) atoms are represented by gray balls, oxygen (O) atoms by red balls and hydrogen (H) atoms by white balls.

In the MPG formula, the two parts of the molecule, the alcohol groups (“OH”, likes water) and the hydrocarbon backbone (“CH”, likes oil), represent fundamental chemical characteristics. Its behavior both in industrial processes, as well as in the human body or in the environment, is well understood.

In the traditional production process PGs are made from propylene oxide reacted with water.

The resulting material is a mixture of mono-, di- and tri-propylene glycols that are then distilled to purify to the different grades of PGs.

MPG is typically produced in two grades: technical or industrial grade (MPGI), and USP/EP. MPG USP/EP designates the requirements for the US Pharmacopiea and the European Pharmacopiea, but this grade is also the grade used in food, feed and personal care applications.

The production of MPG USP/EP is rigorously monitored and controlled through a track-and-trace system from the starting material throughout the production process up to the point of delivery. The high product quality standards, and compliance with stringent hygiene conditions, qualifies MPG USP/EP for use in health-sensitive applications.

Monopropylene Glycol (MPG): Markets

Enabling Everyday Convenience

MPG USP/EP enables a large variety of consumer applications:

MPG USP/EP (pharmaceutical grade) is used as a non-active, “enabling” agent (excipient)
carrier for flavours in food and drinks
face creams, body lotions, deodorant-sticks, lipsticks and many other cosmetic articles soft, moist and consistent
foams stabilizer in cosmetic and healthcare products
moisturizer for pet and livestock feed
carrier of active ingredients in vaccines, cough relief syrups or gel capsules to help deliver this substances within the body for treatment and prevention of diseases.

MPG industrial enables a large variety of industrial and technical applications:

MPG is used as a building block of unsaturated polyester resins (UPR) for multiple market segments including automotive, pipeline, wind turbines blades, solar panel coatings, marine , heavy impact surfaces (floors, Kitchen, bathrooms), protective paint and coatings.
Polyurethane foams (PUF) for the building and construction sector
De-icing chemical for aircraft
Viscosity control in coatings
An active ingredient for the production of hydraulic fluids
An active ingredient for heat transfer fluids used in heating, venting , Air conditioning, refrigerators and cold storage.
Active ingredient for liquid detergents

Monopropylene Glycol (MPG): Safety

MPG: Safe Use for Over Several Decades

The use and effects of MPG have been thoroughly evaluated by numerous entities and agencies, for example by US FDA and ECHA. This substance has been used safely for several decades, including adoption in health-sensitive applications such as food, feed, cosmetics and pharmaceuticals, where it mainly serves as a non-active ingredient or carrier of other substances.

Tests demonstrate that MPG is non-hazardous.

For the environment, tests show that MPG quickly degrades and hence does not persist nor does it bio-accumulate – it is readily biodegradable.

Accordingly, there is:

No official hazard classification or labelling of MPG, and
MPG is not entered on “negative” lists in any country of the EU.

In addition, all members of the sector group representing the producers of MPG within Cefic are committed to Responsible Care^®, a voluntary initiative of the chemical industry aimed at continuous improvement of their health, safety and environmental performance in handling chemicals.

MPG is known to be used as a carrier liquid in electronic cigarettes and to produce artificial (theatrical) smoke. While MPG is a very safe compound, the producers of MPG and members of Cefic’s PO/PG sector group do not support the use of MPG in electronic cigarettes, nor in artificial (theatrical) fogs due to unknown long-term effects on the eye, nose, throat, and respiratory tract membranes, from prolonged inhalation of (fine) droplets of MPG.

Monopropylene Glycol (MPG): Regulatory

Authorities Confirm Safety of MPG

The safety of MPG has been evaluated and confirmed by international and national authorities. The Organisation for Economic Cooperation and Development (OECD), the Canadian Centre for Occupational Health and Safety, EMA, and EFSA have published risk assessments that conclude MPG is not toxic.

Pharamceuticals

In Europe, MPG used in pharmaceuticals applications must follow strict specifications for quality as laid out in the European Pharmacopoeia. The 11^th edition of this official document of the European Directorate for the Quality of Medicines (EDQM) was published in 2022 and is used in more than 37 countries in Europe.

In the US, MPG is regulated by the US Food & Drug Administration (FDA) and must meet the specifications for pharmaceutical grade material laid out in the United Stated Pharmacopeia. US Pharmacopeia/National Formulary (USP/NF) chapter <467> imposes certain limits on Residual Solvents present as impurities in drug substances, excipient, and products.

Food

The European authorities responsible for consumer health have approved the use of MPG USP/EP with food:

In direct food contact regulated by Regulation (EC) No 1333/2008 on food additives: MPG USP/EP is listed as an approved food additive in Annexes II+III under E1520. The full content of these annexes is published under Regulation (EU) No 1129/2011 and (EU) No 1130/2011 respectively. MPG USP/EP meets the purity criteria for E1520 (propane- 1,2-diol) included Regulation (EC) No 2012/231, laying down specifications for food additives in Annexes II and III to Regulation (EC) No 1333/2008.
To reaffirm the safety-in-use of MPG USP/EP as a food additive (E 1520), the European Food Safety Authority (EFSA) has re-evaluated this substance in March 2018 (EFSA Journal 2018 16(4):5235; www.efsa.europa.eu/efsajournal). ESFA’s conclusion was to sustain the current acceptable daily intake (ADI) level of 25 mg/kg body weight per day. Their assessment of dietary risk found that the mean and high exposure levels of the refined exposure assessment scenarios (including the brand-loyalty general population scenario related to the repetitive purchases of flavoured drinks did not exceed the ADI in any population group for the use of MPG USP/EP as a food additive at the reported use.
In indirect food contact covered by Regulation (EU) 2023/1627 and amendments relating to plastic materials and articles intended to get in contact with food, such as packaging material.

The US FDA has affirmed MPG USP/EP as Generally Recognized as Safe (GRAS) when used:

As a direct food ingredient with certain limitations as specified in 21 CFR § 184.1666. It is used in various applications such as stabilizers, thickeners, flavoring agent, emulsifiers, anticaking agent, antioxidant, and others as defined in 21 CFR § 170.3.
In various indirect food contact applications as specified in 21 CFR parts 174, 175, 176 or 177. MPG USP/EP is used in food contact surfaces such as adhesives and components of coatings, paper and paperboard components, polymers and others as specified in the above chapters.

MPG USP/EP used in food applications must meet the specifications of the US Food Chemicals Codex. The caloric content of MPG is 4 cal/g according to the definition of a carbohydrate as defined by the FDA in 21 CFR § 101.9(c)(1)(i)(B).

Animal Feed

As of October 2010, MPG is an approved animal feed* material according to Regulation (EC) No 767/2009. It is listed in the Catalogue of Approved Feed Materials (Regulation(EU) 68/2013) and in the EU Register of Feed Materials.

The US FDA affirms MPG GMP is GRAS (except in cat food) as a general animal feed additive in 21 CFR § 582.1666 or as an emulsifying agent in 21 CFR § 582.4666 when used in accordance with good manufacturing or feeding practice. The FDA has determined that MPG is not safe for use in or on cat food, and such use causes the feed to be adulterated and therefore in violation of the Federal Food, Drug and Cosmetic Act (21 CFR § 589.1001).

*not approved for use in cat food

Cosmetics

In 2012, The Personal Care Products Council confirmed MPG USP/EP to be safe for use in cosmetic articles, and at higher concentrations than those actually used in consumer products.

In Europe Regulation, (EU) 2023/1490 on Cosmetic Products works on the principle of a “negative” list which defines substances that are prohibited or restricted for use in cosmetics. MPG USP/EP (INCI name: MPG) is not on this list and is found on the CosIng European listing (https://ec.europa.eu/growth/tools-databases/cosing/details/37269).

REACH

The Regulation (EC) No 1907/2006 concerning Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) requires producers and importers of chemical substances in quantities of above 1 ton per year to register with the European Chemicals Agency (ECHA). The registration dossier contains detailed information on the substance’s intrinsic properties and hazards, a detailed use mapping, and, for hazardous substances, an exposure and risk assessment. As MPG is not classified as hazardous, exposure scenarios and risk assessments are not required.

MPG producers in the EU have worked together in a Consortium to jointly address the registration requirements of this substance. For further details on this please visit the dedicated webpage managed by REACHCENTRUM. Propylene Oxide-Propylene Glycols REACH webpage managed by REACHCENTRUM .

Please be aware that the registration is valid for the substance (CAS No 57-55-6) with a defined identification agreed in the Consortium, which is different from the quality specifications necessary for industrial vs. pharmaceutical applications.

Classification

Most countries have adopted the UN Globally Harmonised System (GHS) for Classification and Labelling. In Europe GHS is implemented under Regulation (EC) No 1272/2008, also known as the CLP (Classification, Labelling and Packaging) Regulation. In the United States GHS is implemented under the OSHA Hazard Communication Standard (HCS). MPG is not classified as hazardous under GHS.

Monopropylene Glycol (MPG): Health Summary

Non-hazardous Substance

Humans are exposed to MPG primarily through oral intake, inhalation, injectable or skin contact. It is expected to be readily absorbed by oral exposure whereas uptake through the skin is very low. Once in the body, under conditions of normal low exposure, MPG is quickly metabolised and excreted. The half-life of MPG in the blood stream is about 2-4 hours. It is primarily metabolised to lactate which is further metabolised to pyruvate, carbon dioxide and water. Lactate also contributes to glucose formation through gluconeogenic pathways. Very large exposures to MPG (from intravenous pharmaceuticals) may cause lactic acidosis and hyperosmotic changes in the blood and altered nervous system function (alcoholic intoxication).

Tests show that MPG has a very low degree of acute toxicity. MPG is non-irritating to the skin. Long-term tests in rodents conducted with high oral doses found no evidence of adverse effects including cancer and reproductive toxicity. Ingestion by cats (not approved for use in cat food), however, results in species-specific hematological changes. High aerosol concentrations inhaled by rats and humans caused minor nasal and ocular signs that may have been due to mild irritation or drying effects of MPG on mucous membranes. Tests conducted in bacteria, mammalian cells, and in animals demonstrate MPG is not mutagenic. Long term toxicity tests conducted in rodents and dogs demonstrate that this substance is not carcinogen. Tests conducted in rodents with high oral doses indicate MPG is not toxic to reproduction or development.