Core Info - Ethylene Glycol
Mono Ethylene Glycol, commonly referred to as Ethylene Glycol Antifreeze but also referred to as Ethane-1,2-diol, MEG, EG and Industrial Glycol.
Ethylene Glycol was first formulated in the 1850’s and is now commercially produced through a chemical reaction between Ethylene Oxide and a catalyst. Large scale production of Ethylene Glycol commenced in early 1900’s in the USA and it is now produced in huge volumes around the Globe.
Ethylene Glycol - main uses
- Water-glycol based heat transfer fluids, which require an antifreeze function.
- Chiller-glycol formulations, for use in food and beverage cooling processes.
- Secondary refrigerants (liquid) in large cooling systems, where the primary refrigerant (gas) and associated plant are positioned in a central location.
- Waterless and water-based engine antifreeze formulations.
- Deicing fluid for aircraft and runways.
- Intermediate in the production of polyester fibres for plastic bottles made out of PET.
- Humectant, to absorb moisture (water) in manufacturing processes.
- Gas hydrate inhibitor, in gas pipelines.
Ethylene Glycol - characteristics
- Simplest member of the glycol family of organic compounds.
- Clear water-white, mildly sweet, slightly viscous liquid.
- Neat ethylene glycol boils at 198°C and freezes at -52°C when mixed with 28% water.
- Hygroscopic and miscible with water in all proportions.
- Readily biodegradable and does not bioaccummulate.
- Concentrations above 22% v/v in water provide a biostatic function.
Ethylene Glycol - key benefits
- Best heat transfer rates of all glycols and often selected ahead of propylene glycol for this reason.
- Significantly less viscous than propylene glycol, especially at sub-zero temperatures. Lower viscosity fluids require greater pumping-energy and therefore cost more to run.
- Less percentage volume of ethylene glycol is required, when mixed with water, compared with propylene glycol to achieve the same freeze-point protection.
- Manufactured in much larger volumes than propylene and other glycols, subsequently the unit cost is usually lower and availability more reliable.
Ethylene Glycol - drawbacks
The main drawback associated to ethylene glycol is it's toxicity to humans and animals. Whilst the vast majority of Safety Data Sheets declare ethylene glycol as (only) being 'Harmful', a mass of evidence exists to confirm that, relatively small amounts can prove fatal. In the United States the issue of ethylene glycol poisoning has recently been debated in the US Senate.
Until 2010 only propylene glycol was classified as non-toxic, that is no longer the case. In 2010 Hydratech, in association with Jack Evans and Tom Light of Connecticut USA, developed a range of non-toxic heat transfer fluids that are based on ethylene glycol, blended with a detoxification additive. The DTX range of products deliver the thermal efficiency and low viscosity associated to ethylene glycol in concert with the non-toxic rating of propylene glycol.
For more detailed information on the DTX range please select the appropriate Sector tab or call and speak to one of our technical experts.
- Ethylene glycol has a natural tendency to degrade in the presence of oxygen. During degradation several acid by products are formed including; glycolic, formic, acetic and oxalic acids. These acids will rapidly corrode carbon steel and other metals unless appropriate measures are taken. Specifically; minimising the availability of oxygen, pH buffering of acid by products and proactive corrosion prevention via inhibitors.
- It is relatively easy to degrade.
- It promotes corrosion after it degrades.
- It is difficult to monitor.
- It absorbs water from the atmosphere.
- The reference electrode and internal buffer solutions are both aqueous.
- The activity of the hydrogen ion can vary dramatically between an aqueous and organic chemical.
- The dissociation of a compound can vary dramatically between an aqueous and organic chemical.
- The external buffer solutions (for probe calibration) are aqueous solutions.
Minimum recommended volumes of Ethylene Glycol to minimise biological contamination.
The question is often raised, about the recommended minimum concentration of Ethylene Glycol which should be used in a solution of water. Hydratech recommend a minimum of 22% v/v which provides a freeze protection of below -10°C, but often the operator only requires freeze protection to, for example, -2°C which would require significantly less Ethylene Glycol by volume.
There are several reasons for the recommended minimum concentration;
1) Corrosion, Scale & Biological Control. Hydratech Ethylene Glycol based heat transfer fluids are formulated to operate in both cooling and heating systems at a wide range of concentrations. To provide protection over a long period of time, the initial mixture must also have the right balance of corrosion, scale and biological inhibitors in order to maintain proper corrosion control at various concentrations. E.g. The inhibitors in CoolFlow IGE and CoolFlow DTX are formulated to give the best possible performance and fluid lifetime at Ethylene Glycol levels between 25 and 60% v/v. Reducing the Ethylene Glycol concentration below 22% reduces the inhibitor concentrations to a level that may not provide adequate corrosion, scale and biological protection for a system.
2) Increased pH buffering against acid degradation. Both Ethylene and Propylene Glycol break down on exposure to high temperatures. With a higher concentration of fluid, there is also a greater concentration of inhibitor present in the solution. The higher concentration of inhibitors provide increased pH buffering to counteract acidic by-products, that may be formed due to Ethylene Glycol degradation.
3) Biological integrity of the fluid. The third reason for using at least 22% Ethylene Glycol in the system concerns the possibility of bacterial growth. With concentrations at or above 20%, both Ethylene and Propylene Glycol inhibit the growth and proliferation of most microbes and fungi. The reduced surface tension in the glycol solution interrupts the cell walls of the bacteria, resulting in an environment that will not support bacterial growth. At very low glycol concentrations, for example below 1%, both Ethylene and Propylene Glycol act as a nutrient for bacteria. At these concentrations, bacteria will biodegrade the Propylene Glycol causing rapid growth of bacterial contamination. At levels above 1 and below 20%, some bacteria can survive with limited growth, especially at moderate temperatures.
The presence of bacteria does not always imply bacterial growth. Solutions of 22% or more Ethylene Glycol are biostatic, not biocidal. Therefore if a source of bacteria is introduced in to solutions of Ethylene Glycol, the fluid may show the presence of bacteria. For this reason Hydratech recommend the pre-commission cleaning of new installations and periodic testing of the system fluid to check for any biological activity – please refer to the SureFlow Fluid Maintenance Program for more guidance. To further minimise the possibility of contamination from external contamination, all Hydratech formulations include both short-term and long-term biocides.
Technical insights into uninhibited ethylene glycol
Taken From "Process Cooling & Equipment USA, July 2002." Author. Mr. Keith Wheeler.
When used as a heat transfer fluid in chiller applications, uninhibted ethylene glycol can degrade, causing problems and increasing costs. Learn the science behind its properties and why an inhibited ethylene glycol might be a solution.
Uninhibited ethylene glycol has been a popular heat transfer fluid choice in chillers for many years because of its initial low cost and excellent freeze and heat protection over a wide temperature range. It also has good heat transfer capabilities and low conductivity, not to mention that it is completely miscible with water -- an inexpensive and abundant solvent. Those are the pros. There are, however, disadvantages inherent to uninhibited ethylene glycol, including:
These disadvantages can lead to frequent fluid changing, which can cost users money in labor and parts. There also can be lost production costs due to shutdown and possible premature failure of the system.
Degradation of Uninhibited Ethylene Glycol
Dow Chemical Co., Midland, Mich., distributes a technical bulletin entitled, "Acidic Thermal Degradation of Ethylene Glycol and Propylene Glycol." This advisory bulletin references the research of Dr. Walter Rossiter and his team of the National Bureau of Standards, now named the National Institute for Standards and Technology (NIST).
Dr. Rossiter and his team conducted experiments that showed uninhibited ethylene glycol will degrade into five organic acids -- glycolic, glyoxylic, formic, carbonic and oxalic -- in the presence of heat, oxygen, copper and aluminum. Copper and aluminum act as catalysts in the presence of uninhibited ethylene glycol. The organic acids then will chemically attack copper and aluminum in as little as three weeks under the right conditions to form metal organic compounds in the fluid.
Another extensive study on the degradation of uninhibited ethylene glycol was conducted by John Beavers and Ronald Diegle of Battelle, Columbus Laboratories. They concluded that degradation of uninhibited ethylene glycol occurred in absence of contact with various metals, but degradation was accelerated by the metals' presence.
Many chemical resistance guides list that copper, aluminum and other metals are acceptable for use with uninhibited ethylene glycol. Usually, their recommendations are based on a two-week chemical compatibility study exposing various metals to uninhibited ethylene glycol at various temperatures. The above research indicates that uninhibited ethylene glycol does not begin to degrade and become acidic until after three weeks under extreme conditions (212°F [100°C] and oxygen bubbling into the uninhibited ethylene glycol solution). So, the chemical resistance guides are based on the "solvency" effects of uninhibited ethylene glycol rather than the degraded, acidic uninhibited ethylene glycol effects on metals. The latter is much more corrosive toward metals.
Corrosion of metals will commence at locations where metal ions are stripped away from the base metal by acidic, uninhibited ethylene glycol. The section of metal that has had its surface metal stripped away now becomes a metal oxide. Also, once metal ions are in solution, they can attach themselves to oppositely charged metals to form a galvanic corrosion cell. Rapid corrosion can commence at these sites in the cooling loop. Corrosion byproducts (metal oxides) then can be swept away to cause damage downstream. Typical problems associated with corrosion in a chiller cooling-loop system are clogging of a particulate filter, damage to mechanical seals and premature failure of the system.
Preventive Maintenance becomes difficult Because uninhibited ethylene glycol can degrade and become corrosive in as little as three weeks, preventive maintenance can be time consuming and costly.
It is almost impossible to achieve an accurate pH reading for 100 percent uninhibited ethylene glycol because it is an organic liquid. pH meters are susceptible to errors and instability when exposed to organic chemicals. According to various manufacturers of uninhibited ethylene glycol, they state this chemical has a pH of 5.5 to 8.0. Most uninhibited ethylene glycol manufacturers do not specify a pH for this chemical; they state not applicable or not available (NA) on the product data sheet or material safety data sheet (MSDS). Others state to dilute the chemical with water to achieve a pH reading. But, by diluting with water, is one measuring the pH of the added water or the pH of uninhibited ethylene glycol/water solution?
A pH reading of an uninhibited ethylene glycol/water solution becomes less accurate with an increase in the uninhibited ethylene glycol concentration. Increasing the water concentration in uninhibited ethylene glycol allows for a more stable and reliable pH reading.
Some inherent problems associated with using a pH meter to measure pH of an organic chemical are:
Determining when to change out your uninhibited ethylene glycol by measuring pH to detect an increase in acidity is an unreliable measuring tool.
Atomic absorption spectroscopy (AAS) and inductively coupled plasma (ICP) are two analytical tools that detect specific metals and their concentrations in a fluid. A sample of the uninhibited ethylene glycol can be extracted from an application and analyzed by AAS or ICP to detect the metals that have been chemically attacked by acidic uninhibited ethylene glycol. However, this is a reactive approach because if there is a high concentration of metals found in the fluid, this signifies that the uninhibited ethylene glycol already has degraded and has turned acidic. Corrosion already has occurred and internal system damage is likely to be present.
A gas chromatography/mass spectrometer (GC/Mass Spec) is used to detect organic compounds in a solution. This analytical tool can measure the organic acids that develop when uninhibited ethylene glycol starts to degrade.
Uninhibited ethylene glycol, like other glycols, is hygroscopic; it will absorb moisture from its environment. The amount of water absorbed from its environment is proportional to the percent relative humidity (figure 1). At 50 percent relative humidity, 100 percent uninhibited ethylene glycol will absorb 20 percent water at equilibrium. This drops the concentration of uninhibited ethylene glycol from 100 percent to 83.3 percent.
Because of this property, ethylene glycol is used as a humectant for textile fibers, paper, leather, adhesives and glue. This desirable property helps make these products softer, more pliable and more durable. However, water absorption can potentially cause many problems in chiller applications.
Many users of uninhibited ethylene glycol are unaware of its hygroscopic property and often leave the cover off the container. Once this occurs, uninhibited ethylene glycol will immediately initiate water absorption.
Suppose you have a new chiller and you fill it up with what you believe is 100 percent uninhibited ethylene glycol from floor stock. The relative humidity within your building is 75 percent, and the application temperature is -4°F (-20°C). Accor-ding to your freeze protection guide, you can fill the chiller with 35.5 percent uninhibited ethylene glycol and 64.5 percent (by volume) deionized (DI) or distilled water to achieve freeze protection at -4°F. To be safe, you fill the chiller with 38.5 percent uninhibited ethylene glycol and 61.5 percent DI or distilled water to achieve freeze protection down to -10°F (-23°C). If the environment on the floor is 75 percent relative humidity and the cap has been kept off of the container, the 100 percent uninhibited ethylene glycol can become 71.4 percent uninhibited ethylene glycol and 28.6 percent water. Now, you dilute this solution with 61.5 percent water (thinking you will have a solution of 38.5 percent uninhibited ethylene glycol and 61.5 percent water) and your true concentration becomes 27.5 percent uninhibited ethylene glycol and 72.5 percent water. This concentration only allows freeze protection down to 7°F (-14°C). You now have a solution that you thought would provide freeze protection to -10°F but in reality, it only provides freeze protection to 7°F. The decrease in freeze protection is 17°F (9°C). This error can result in a system failure.
Conversely, 100 percent uninhibited ethylene glycol is used for heat protection. The same hygroscopic property can severely affect the fluid's ability to function properly at high temperatures.
There are many ways that the surrounding air can find its way into a closed-loop system. Air (humidity) can enter a chiller when the cap to the tank is removed for filling. Also, air can enter when the cap to the tank is removed to visually inspect the fluid level and during subsequent top-offs with uninhibited ethylene glycol. Air also enters the chiller via any left open valves or any leaks (loose hose clamps) in the system. Finally, uninhibited ethylene glycol is viscous and will entrap air when it is poured.
Industrially inhibited ethylene glycol contains approximately 93 percent uninhibited ethylene glycol, 3 percent water and 3 percent inhibitors. The inhibitors serve two purposes: to protect various metals in the cooling loop from corroding and to buffer the uninhibited ethylene glycol so that it retards the degradation process.
Automotive antifreeze typically contains silicates and therefore should not be used in chillers. Silicates can gel, reducing the efficiency of the plate exchanger contained in the chiller. Also, silicates can damage the mechanical seal of a pump found in a chiller, causing the pump to leak.
Inhibited ethylene glycol does share the same hygroscopic property as uninhibited ethylene glycol. Preventative steps must be followed to ensure minimal exposure to air. A disadvantage to inhibited ethylene glycol, however, is its initial cost.
Using inhibited ethylene glycol in place of uninhibited ethylene glycol can save money over the lifetime of the chiller and tool. If uninhibited ethylene glycol is not allowed to degrade (using inhibitors), then money is saved by less frequent maintenance to the cooling loop system (labor, parts and lost production costs) and change out of the fluid (labor, replacement fluid and lost production costs).
Health, Safety and Environmental Info on Ethylene Glycol
OECD Screening Information Data Set (SIDS) Assessment Profile for Ethylene Glycol
Chemical Name Ethylene Glycol (Ethane-1,2-diol) CAS No. 107-21-1
Structural Formula HOCH2CH2OH
Recommendations The chemical is currently of low priority for further work.
Category members (of the Ethylene Glycol family) are represented by the generic molecular structure, HO(CH2 CH2 O) n H, where n = 1-5. All category members therefore possess two terminal hydroxy groups and the members differ from each other only in the number of oxy-ethylene units. Because of this it is appropriate to classify ethylene glycol and the higher glycols (up to and including n=5) as a single group. At n = 6-8, absorption from ingestion decreases and certain physicochemical attributes change significantly. Adequate studies are available for most of the required SIDS endpoints for the category members. A category approach is used where experimental data are not available.
Category members ethylene glycol and the higher glycols (di-, tri-, tetra-, and penta-) are closely related in structure and have physicochemical properties which differ in a regular and expected way as a result of increasing molecular weight and consistent functionality of a relatively less stable hydroxy moiety on each end of the molecule. Thus, the hazard profile and dose response are also expected to change consistently, with decreasing potential for adverse effect with increasing molecular weight. Available data and quantitative structure activity modelling for the category for several toxicological endpoints confirm this expectation, indicating that it is reasonable to assume consistent changes in toxicological effects for the relatively few instances where experimental data for the category are lacking. Available data and modelling confirm that as the molecular weight increases, the potential for systemic, reproductive, and developmental toxicity decreases. Available data for several eco-toxicological endpoints demonstrate that the potential for these effects is consistently low throughout the category in that the LOELs are greater than the limit dose. Poly-ethylene glycol 200 (PEG 200, CAS No. 25322-68-3), which is not a category member, is a mixture of EGs (n=2 to 8, thereby containing category members and other higher molecular weight ethylene glycols) with an average molecular weight of approximately 200 and an average of 4 oxy-ethylene units. It has some properties similar to the category members and data from this mixture are used to support the trend that as molecular weight increases, toxicity decreases within the five-member category.
Ethylene Glycol, Di-Ethylene Glycol and Tri-Ethylene Glycol are almost completely absorbed by laboratory animals via oral routes as would be expected from their total miscibility with water. As tetra Ethylene Glycol and penta-ethylene glycol are likewise completely miscible with water and are of relatively low molecular weight, it is reasonable to assume that they are likewise extensively absorbed via the oral route. The absorption estimate for inhaled EG is approximately 100 percent. No direct measures of inhalation absorption are available for DEG, TEG, tetra-EG and penta-EG. In in vivo rodent dermal absorption studies, 1-51% of EG was absorbed. Dermal bioavailability of DEG was estimated as 9%. No direct measures of dermal absorption a available for TEG, tetra-EG, and penta-EG. Since the ethylene glycols are completely soluble in water, they are expected tobe well distributed throughout the aqueous tissues of the body with lower concentrations in adipose tissue; Uniform distribution has been demonstrated to a limited extent for ethylene glycol.
The main metabolic pathway for metabolism of the ethylene glycols is oxidation via alcohol dehydrogenases and aldehyde dehydrogenases. The main metabolites of Ethylene Glycol are carbon dioxide, oxalic acid and glycolic acid. Identified DEG and TEG metabolites include carbon dioxide, oxalic acid and other acid metabolites. Ethylene glycol, DEG, and TEG may be directly eliminated by urinary excretion. Acid metabolites of ethylene glycol, DEG and TEG are also eliminated in urine and may also be metabolized to carbon dioxide and eliminated in exhaled breath. Results of acute mortality studies in rodents indicate that the Ethylene Glycols are generally of low acute toxicity by the oral, inhalation and dermal routes of exposure with the values for reported endpoints being greater than a limit dose. Acute lethality by the oral route is greater than that for the other category members. The acute toxic effects of ethylene glycol in laboratory animals and humans can include narcotic effects, metabolic acidosis and renal toxicity. Acute oral toxicity in rats (measured as LD50 in mg/kg) ranged from 5890 in ethylene glycol to over 16000 in penta-EG. Tested members of the ethylene glycol category have LOAELs greater than a limit dose for repeated dose toxicity studies by the dermal, inhalation and oral routes. No adverse effects were seen in dermal studies performed with ethylene glycol and tetra-EG. Oral repeated dose toxicity (NOAEL in mg/kg/day) ranged from approximately 150 for ethylene glycol and DEG to greater than 2000 for tetra-EG and penta-EG. Studies by the oral route demonstrate that repeated oral exposure to the lower molecular weight category members (EG and DEG) induces renal toxicity. However, TEG had only minor effects on the kidney and as the number of oxyethylene units increases to four and five oxyethylene units, no renal toxicity is observed even at high doses. Due to the structural and physical similarities of penta-EG with the other category members and data for the ethylene glycol mixture PEG 200, it can be reasonably assumed that penta-EG also will have low potential for repeated dose mammalian toxicity.
Ethylene glycol can produce skin irritation, but the other EGs tested on humans (DEG, TEG, and tetra-EG) produce minimal irritation, and the human skin primary irritation index decreases with an increasing number of oxyethylene units. All category members produce only minor eye irritation. While DEG caused respiratory depression, the characteristics were not typical of a “pure” airway irritant (WIL, 2001). In a human clinical study of ethylene glycol, all participants found exposure to 0.14mg/L to be irritating to the throat and exposures above 0.20mg/L could not be tolerated due to severe irritation. Ethylene glycol, DEG, TEG and tetra-EG have not induced skin sensitization.
Mutagenicity studies in bacteria have been conducted for all category members, and in vitro mutagenicity studies in mammalian cells have been conducted for ethylene glycol, DEG, TEG, and tetra-EG. The results have been uniformly negative (± S9 activation). The results of in vitro assays of ethylene glycol, DEG, and TEG for chromosomal aberrations and in sister chromatid exchange assays have also been uniformly negative. Penta-EG has not been tested in vitro for chromosomal aberrations, but produced no biologically significant chromosomal damage in the mouse bone marrow micronucleus test. Evidence indicates that tetra-EG causes chromosomal aberrations in vitro. However, results of in vivo genotoxicity studies have been negative (dominant lethal test) or equivocal (bone marrow chromosome aberrations in rats, peripheral blood micronucleus test in mice). In several studies conducted for ethylene glycol, DEG and TEG some of which were limited, there was no evidence of carcinogenicity in animals. QSAR results from multiple models for mutagenicity in vitro (Salmonella, mouse lymphoma) and cancer were negative. No structural alerts were identified.
Information on the genotoxicity of PEG 200 is not considered to contribute to interpretation of results for compounds in the category, due to the lack of assessment of some its components for mutagenicity. Ethylene glycol, DEG, and TEG have been assessed using the Reproductive Assessment by Continuous Breeding protocol. Ethylene glycol and DEG produced decreased numbers of litters per fertile pair and live pups per litter. No reproductive effects were seen for TEG-exposed mice. Tetra-EG was negative in the rodent dominant lethal assay and repeat dosing with tetra-EG for 4 weeks in rats produced no notable changes in the histopathology of the testes and epididymides. Extensive developmental toxicity data are available for ethylene glycol, DEG, and TEG. Observed effects include reduced foetal body weights and skeletal variations for Ethylene Glycol, DEG and TEG and malformations at higher dose levels and dose rates for ethylene glycol and DEG. By the oral route, DEG and TEG do not cause any developmental effects below a limit dose. There is a clear trend of NOAELs increasing with the number of oxyethylene units in the rat studies. Benchmark dose analysis indicated that the trend also held for the mouse. NOAELs for repeated oral exposure ranged from approximately 150mg/kg/day for ethylene glycol (16-week study) to an estimate of over 2000 mg/kg/day for penta-EG. While studies of repeated dermal exposure to the EGs are limited, the two relevant studies indicate that these compounds are of low toxicity by the dermal route. No effect was observed in maternal animals dermally exposed to ethylene glycol at 3549 mg/kg/d for 10 days and no toxicity was found in animals dermally exposed to 3360 mg/kg/d tetra-EG for 13 weeks. These findings are consistent with the low dermal bioavailability determined for DEG and assumed for higher molecular weight EGs.
The Ethylene Glycol category consists of liquids of low volatility and high water solubility. Partition coefficients (Log Kow) range from –1.20 for ethylene glycol to –2.3 for penta-EG. All evidence indicates that ethylene glycol is readily biodegradable. The rate of degradation, however, decreases for other members of this category. Biodegradation of EGs may deplete levels of dissolved oxygen in receiving water-bodies near airports where these chemicals are used in high volume for deicing activities. Depletion of dissolved oxygen can result in adverse effects on aquatic organisms that may be present near points of effluent discharge. There is a limited potential for category members to bioaccumulate. Fish acute toxicity (measured as LC50 in mg/L) has been tested for all category members and ranges from 22,800 for ethylene glycol to greater than 50,000 for penta-EG. The acute toxicity of the category members to invertebrates has also been tested. Toxicity to Daphnia (measured as LC50 in mg/L) is greater than 20,000 for all category members except tetra-EG (LC50=7,800 mg/L) indicating low toxicity, but the toxicity was not as uniform as in fish. Toxicity evaluations in another invertebrate, brine shrimp (Artemia salina) were imprecise, but appear to be more consistent than the measured Daphnia toxicity values (no toxicity observed at the highest tested dose, 20g/l for ethylene glycol, 10 g/l for DEG, TEG and tetra-EG). Algal toxicity has been tested for ethylene glycol, DEG, TEG, and Penta-EG, and no toxicity was found at concentrations less than or equal to 100 mg/L. Based on the low toxicity of tested category members, it can reasonably be assumed that tetra-EG likewise poses no appreciable hazard to algae. The QSAR predictions indicate that the category members should exhibit low toxicity, with trends of decreasing toxicity with increasing chain length and are supportive of the available experimental data.
Total global production capacity estimated for each category member in 2001 was as follows: Ethylene Glycol - 15,841,000 metric tonnes; DEG - 1,584,000 metric tonnes; TEG - 150,000 metric tonnes; Tetra-EG - 10,000 metric tonnes; and Penta-EG - 3,000 metric tonnes. Approximately 78% of ethylene glycol is consumed in the manufacture of polyethylene terephthalate (PET) with an additional 13% used as an ingredient in automotive coolants. The largest use of DEG is in the production of unsaturated polyester resins, polyols and polyurethanes. The majority of TEG consumption is for natural gas dehydration. Commercial mixtures of tetra- and penta-EGs left over from distilling out lower boiling ethylene glycol, DEG, and TEG are often processed into brake fluids, and can also be used as an aid in cement grinding. Occupational exposure to members of the ethylene glycol category is limited during manufacture by the enclosed, continuous nature of the manufacturing process. The most likely routes of occupational exposure to ethylene glycol are dermal and inhalation of vapours and mists. The use with the highest potential for exposure is in deicing aircraft and runways. There is some potential for consumer exposure to lower molecular weight EGs. Consumers may come into dermal contact with ethylene glycol and DEG infrequently and for short periods, when topping off radiator antifreeze in personal vehicles. Consumers may also come into dermal contact with low concentrations of ethylene glycol present in a variety of commercial products and DEG in limited consumer products. Human exposure to ethylene glycol in commercial products can occur through dermal contact and inhalation of air and ingestion of soil near point sources. Workplace exposure to DEG may occur during manufacture or use as an industrial intermediate. Exposure may also occur during its use as a solvent. Almost all DEG is used industrially. The most likely human exposure to TEG is in the industrial setting. The most likely route of exposure is through dermal contact (e.g., during quality control sampling). The primary uses of tetra-EG, penta-EG, or mixtures containing these substances, are industrial. Therefore human exposure is most likely to occur in the work place, during such uses as a solvent, industrial extractant, plasticizer or humectant. The most likely route of industrial exposure is dermal, since tetra-ethylene and penta-ethylene glycols possess extremely low vapour pressure (6 x 10-5 hPa or less).
Environment: The chemicals in this category are currently of low priority for further work.
Human Health: Ethylene glycol and penta-ethylene glycol are candidates for further work. The remaining chemicals in this category are currently of low priority for further work.
Rationale for the recommendation and nature of further work recommended
Available data for several eco-toxicological endpoints demonstrate that eco-toxicological effects due to direct exposure to ethylene glycols are unlikely to result. However, biodegradation of ethylene glycols may deplete levels of dissolved oxygen in receiving water-bodies near airports where these chemicals are used in high volumes for deicing activities. Depletion of dissolved oxygen can result in adverse effects on aquatic organisms that may be present near points of effluent discharge. Member countries (particularly Nordic countries) that use ethylene glycol for deicing at airports should verify their exposure profile and risk management measures for this chemical to determine if there is a need for additional measures to be applied.
Based on studies by different routes (oral vs. dermal) and different regimes (gavage vs. diet), ethylene glycol exposure below the limit dose results in developmental toxicity in animals only by the oral route and only when rapidly ingested (bolus). Depending upon use and exposure, member countries should assess possible risk associated with both renal and developmental toxicity for the lower molecular weight EGs. In this context, an additional study on dose-response for renal effects following long-term exposure to ethylene glycol has been initiated in the sponsor country. An additional in vitro gene mutation assay for penta-EG in mammalian cells, the CHO/HPRT test, has been initiated to expand the genotoxicity profile of this substance. Ethylene glycol renal effects testing and penta-EG CHO/HPRT testing results will be provided to the OECD when available.
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