Diethylene Glycol (DEG) is a synthetic organic compound. It presents as a clear, colorless, and slightly viscous liquid that is essentially odorless, though it possesses a characteristic sweet taste. These physical properties make it highly miscible with water and many other organic solvents, which is the basis for its widespread industrial utility, though it is highly toxic to humans upon ingestion.
Primary Industrial Applications
The primary industrial function of Diethylene Glycol is its powerful action as a solvent for numerous compounds that do not readily dissolve in water. It is highly effective at dissolving materials such as nitrocellulose, many types of resins, dyes, and oils. This makes it a common component in industrial cleaning agents and specialized fluid mixtures.
DEG is also prized for its hygroscopic nature, meaning it readily absorbs and retains moisture from the air. This allows it to function as a humectant, controlling water content in various materials. Industrial applications include adding it to glues, cork, and certain textile formulations to prevent them from drying out or becoming brittle.
Within the automotive and energy sectors, DEG is incorporated into formulations for coolants and antifreeze solutions. While ethylene glycol is the primary ingredient in most automotive antifreeze, DEG is often present as a co-product of its manufacturing process or added to lower the freezing point and raise the boiling point of the mixture. Furthermore, it is used as a dehydrating agent for natural gas, effectively stripping water vapor from the gas stream to prevent pipeline corrosion and hydrate formation.
Use in Chemical Synthesis
A major use of Diethylene Glycol involves its role as a chemical intermediate, meaning it is a foundational building block for synthesizing more complex materials. The molecule contains two hydroxyl (-OH) groups, which are chemically reactive sites. These sites allow it to be incorporated directly into polymer chains.
DEG is a primary raw material in the manufacture of various polyesters, including both saturated and unsaturated polyester resins. These resins are then used in the production of fiberglass, certain coatings, and durable plastic components. Examples include materials found in boat hulls and automotive parts.
It is also an important component in the synthesis of polyurethane, a versatile polymer used to create foams, elastomers, and adhesives. Here, DEG can function as a chain extender or cross-linker, which helps determine the final material’s flexibility, rigidity, and overall physical properties. Additionally, it serves as a precursor in the production of other specialty chemicals, such as morpholine and 1,4-dioxane.
Toxicity and Contamination Risk
Despite its extensive industrial utility, Diethylene Glycol is a highly toxic substance if ingested, posing a severe health risk to the public. Its danger stems from the fact that it is metabolized in the liver by the enzyme alcohol dehydrogenase into toxic byproducts, primarily diglycolic acid (DGA). This acid rapidly causes severe, irreparable damage to the renal tubules, leading to acute kidney failure, which is the hallmark of DEG poisoning.
The contamination risk is high because DEG shares similar physical characteristics—colorless, odorless, and viscous—with safe, pharmaceutical-grade ingredients like propylene glycol (PG) and glycerin. This similarity, coupled with DEG’s significantly lower price, has historically led to its intentional substitution for these non-toxic substances by unscrupulous suppliers or manufacturers. This fraudulent practice is the root cause of multiple global poisoning epidemics.
Contamination most frequently occurs in liquid oral medications, such as cough syrups, fever reducers, and vitamins, where glycerin or PG are used as solvents or vehicles. Since 2022, the World Health Organization (WHO) has issued multiple alerts concerning DEG-contaminated medicines in several countries, resulting in hundreds of fatalities, predominantly among young children. Regulatory bodies worldwide are continuously strengthening requirements for testing high-risk drug components, recognizing that even small amounts of DEG can be fatal.