Diethylene glycol, or DEG, is a colorless, liquid organic compound at room temperature produced by the interaction of ethylene glycol and triethylene glycol. It is used in a wide variety of industrial applications, including as a compound in the manufacture of polyurethane plastic, in natural gas production, and as a solvent. The ability of diethylene glycol to act as a humectant where it absorbs water or helps other materials to do so has also led to its use in the production of tobacco and cork, as well as printing inks and glues.
DEG is not corrosive and has a high flash point of between 309° to 617° Fahrenheit (154° to 325° Celsius) so it can be stored in stainless steel drums and does not easily catch fire. These traits along with its low freezing point of 16° Fahrenheit (-9° Celsius) and high boiling point of between 473° to 885° Fahrenheit (245° to 474° Celsius) also give it uses in cooling applications, such as for some anti-freeze solutions, and as a heat transfer fluid. Other high-stress applications for diethylene glycol include in the manufacture of explosives and as a hydraulic and brake fluid.
There is a world demand for close to 24,000,000 metric tons of ethylene glycol per year as of 2010, and China consumes about one-third of this supply. Monoethylene glycol (MEG) fills 90% of the market's needs, and diethylene glycol and triethylene glycol are made as supplemental chemicals in the manufacturing process. The bulk of MEG, at around 85%, is used to manufacture polyester fiber for clothing and related plastics. Production capacity has increased at a rapid rate and the world market for the chemical family, in 2010 to 2011, is estimated to be oversupplied by 3,500,000 metric tons.
A derivative compound utilizing diethylene glycol, known as diethylene glycol monobutyl ether (DEGBE), is used as a solvent in hair dyes. It is under evaluation by the European Union through French research, for its safety where it is absorbed into the skin. A 2006 assessment led to some French restrictions on its use, where concentrations of no more than 9% are allowed in hair products. As of the mid 1990s, up to 50,000 metric tons of the chemical were being used in Europe as an ingredient in cleaning agents and surface coatings, such as paints.
The health risks of diethylene glycol exposure itself are well-established. Inhalation can cause nausea and vomiting, among many other symptoms, and ingestion can cause a form of alcohol intoxication and lead to convulsions and death. Exposure is also known to have degenerative effects on many organs and biological systems in the human body, including causing brain damage. Due to the fact that diethylene glycol has been responsible for several cases of mass poisoning of people since 1937, it is universally restricted from being used as a food additive. The compound is nevertheless present at a 0.2% concentration as an impurity in polyethylene glycol, which is used as a food additive.