Ethylene Glycol

What is Ethylene glycol?

Ethylene glycol (chemical formula C₂H₆O₂, CAS number 107-21-1) is a colourless, odourless, and syrupy liquid known for its distinctly sweet taste. It can also exist in the air as a vapour. Commonly referred to as “glycol” or “glycol alcohol,” ethylene glycol is a versatile compound widely used in both industrial and consumer applications.

What is Ethylene used for?

Ethylene glycol is primarily used as a raw material in the production of antifreeze and de-icing solutions for vehicles, aircraft, boats, and runways. Its utility extends well beyond this: it’s used in cooling and heating systems, hydraulic brake fluids, electrolytic condensers, and plasticisers.

It also plays a role in the manufacture of polyethylene terephthalate (PET) bottles, lacquers, resins, wood stains, dyes for leather, and photographic developing solutions. In the textile industry, it aids in processing and helps create polyester fibres and synthetic waxes.

Additionally, it’s found in cosmetics, pharmaceuticals, and certain food-contact applications. Ethylene glycol is also used to produce artificial smoke or mist for theatrical productions and is a key component in various printing inks and extinguishing foams.

Ethylene glycol is used in de-icing fluids to safely remove ice from vehicles, aircraft, boats, and runways in cold weather conditions.

Sources & Routes of Exposure

Occupational exposure to ethylene glycol may occur through inhalation or skin contact during its production or use. It may enter the environment through industrial wastewater, de-icing operations, spills, or improper disposal of antifreeze and solvents.

The most common exposure routes include:

Inhalation (especially in occupational settings)
Ingestion (often accidental or intentional from antifreeze)
Dermal contact with skin or eyes

Toxokinetics

Once ingested, ethylene glycol is rapidly and extensively absorbed via the gastrointestinal tract. Absorption through the skin is slower, and there is limited data on respiratory uptake.

After absorption, it distributes throughout the body and undergoes a series of metabolic transformations. These processes yield various metabolites, including glycine, malate, oxalic acid, formate, and carbon dioxide.

Ethylene glycol is eliminated from the body through two main routes:

Exhalation as carbon dioxide
Urinary excretion of unmetabolized ethylene glycol and its by-products (e.g., glycolic acid, oxalic acid)

Its elimination half-life ranges between 2.5 to 8.4 hours, and higher doses can lead to a saturated metabolic pathway, increasing excretion via urine.

Health Effects

Acute Effects

Large ingestions of ethylene glycol can result in three distinct stages of toxicity:

CNS depression—vomiting, drowsiness, coma, respiratory failure, convulsions
Cardiopulmonary complications
Renal damage

In animal models (rats, mice, rabbits, guinea pigs), ethylene glycol has shown moderate acute toxicity via inhalation or dermal exposure and low to moderate toxicity through ingestion.

Chronic Effects

Long-term inhalation exposure to low concentrations may cause irritation of the throat and upper respiratory tract. Chronic dietary exposure in rats has resulted in kidney and liver toxicity. Subchronic inhalation exposure in animals has caused ocular damage, lung inflammation, and other organ effects.

The US EPA has set an oral reference dose (RfD) of 2.0 mg/kg/day, based on kidney toxicity observed in rats. No reference concentration (RfC) has been established for inhalation.

Reproductive Effects

There is no definitive data on reproductive or developmental impacts in humans. However, animal studies have shown ethylene glycol can cause:

Fetotoxicity
Increased preimplantation loss
Delayed ossification
Foetal malformations

It’s important to note that in some inhalation studies, animals ingested ethylene glycol through grooming, complicating the interpretation of results.

Cancer Risk

Epidemiological studies have not shown an increased risk of cancer (e.g., renal cancer) in workers exposed to ethylene glycol. Similarly, animal studies conducted by the National Toxicology Programme (NTP) found no significant increase in tumour incidence.

As a result, the US EPA has not classified ethylene glycol as carcinogenic.

Safety

First Aid Measures

Eye Contact

Remove contact lenses if present.
Rinse eyes immediately with plenty of water for at least 15 minutes. Cold water may be used.
Seek medical attention if irritation persists.

Skin Contact

Wash the affected area thoroughly with soap and water.
Apply an emollient to soothe irritation. Cold water may be used.
Seek medical attention if irritation develops.

Inhalation

Remove the person to fresh air.
If not breathing, perform artificial respiration.
If breathing is difficult, administer oxygen.
Seek immediate medical attention.

Ingestion

Do not induce vomiting unless directed by medical personnel.
Never give anything by mouth to an unconscious person.
If large amounts are swallowed, contact a physician immediately.
Loosen any tight clothing such as collars, ties, belts, or waistbands.

Note: Individuals with pre-existing kidney, respiratory, neurological, or eye conditions may be more sensitive to ethylene glycol exposure.

Notes to Physician

Support vital functions and correct for dehydration, shock, and fluid imbalance.
Elimination of ethylene glycol and its metabolites is crucial. This can be done by:
- Gastric lavage (most effective within 1 hour of ingestion).
- Correcting metabolic acidosis using intravenous sodium bicarbonate. Adjust administration based on frequent acid-base status checks.
- Administering ethanol or fomepizole (Antizol) orally or intravenously as antidotes to inhibit the formation of toxic metabolites.
Hemodialysis may be required in severe cases where metabolic acidosis or renal failure has occurred. It is effective in removing ethylene glycol and its toxic metabolites and correcting acid-base disturbances.

Exposure Controls and Personal Protection

Exposure Controls

Install exhaust ventilation or other engineering controls to keep vapour levels below occupational exposure limits.
Ensure eyewash stations and safety showers are located close to workstations.

Personal Protective Equipment

Eyes:

Wear chemical safety glasses or splash-proof goggles.

Skin and Body:

Use a synthetic apron and impervious gloves (e.g., nitrile or neoprene).
For large-scale handling or spills, wear full-body protective clothing and chemical-resistant boots.

Respiratory Protection:

Not typically required under normal conditions.
If ethylene glycol is sprayed, heated, or if vapour levels exceed limits, use a properly fitted air-purifying respirator approved for organic vapours.

Important: Always consult a safety specialist prior to handling ethylene glycol in hazardous scenarios to ensure PPE adequacy.