What Is It?

Ethylene oxide is an EPA-registered antimicrobial pesticide[1]. It is also used as a chemical intermediary in the manufacturing of ingredients used in personal care and cleaning products. In a process called ethoxylation, ethylene oxide is added to other ingredients to make them less “harsh.” These ethoxylated ingredients include sodium laureth sulfate, and many chemicals that end in “eth,” which often denotes ethoxylation, like ceteareth and oleth. They also include polyethylene glycols (PEGs) and polysorbates – both are groups of ingredients treated with ethylene oxide. Ethoxylated ingredients are often used as thickeners, softeners, moisture-carrying agents, surfactants, cleaning agents, and penetration enhancers.

Why It Matters

When shopping for personal care and cosmetics, it’s always a refreshing feeling to pick up a product with a transparent ingredient label. Yet, while avoiding some chemicals is as easy as looking for a name on the back of a shampoo bottle, others are not as simple to locate. Ethylene oxide is used to synthesize other ingredients and can contaminate finished ingredients as a residual substance. Despite its links to cancer, reproductive toxicity, and other adverse human health effects, ethylene oxide is not federally required to be listed on ingredient labels (with the exception of state law in California) because it is not an intentionally added ingredient to cosmetics and personal care.

Where It’s Found

Ethylene oxide is primarily used for the purpose of synthesizing other chemicals. It may be used industrially as a pesticide or sterilizing agent in medical supplies[4]. It is also used as a fumigant in spices and herbs[1].

Ethoxylated ingredients are most often found in products that suds, like shampoos, shower gels, dish soaps, and laundry detergents. They are also found in toothpastes, mouthwashes, deodorant, and hair dyes.

Found In

Products with ethoxylated ingredients
Laundry detergents
Dish soaps
Personal care and cosmetic products that suds:
Shampoos
Toothpastes
Bubble baths
Medical supplies sterilized with ethylene oxide gas

The Health Concern

Ethylene oxide is an established carcinogen. Most notably, chronic inhalation exposure is associated with cancers of the white blood cells, such as lymphoma and leukemia, as well as stomach and breast cancers[4]. It is also linked to reproductive and developmental toxicity and genetic damage[5][6][7]. In 2011, it was placed on the TEDX List of Potential Endocrine Disruptors from experiments in rats and fish[8].

Ethylene oxide is listed in the Poisons Standard as a substance with high potential for causing harm at low exposure and is prohibited in cosmetic products by several regions, including Europe, Southeast Asia, Canada, and New Zealand[6]. Adverse neurological effects from ethylene oxide exposures are commonly reported in occupational settings and have been reported in chronically exposed laboratory animals[6]. Ethylene oxide has been classified as a skin sensitizer in humans by the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) in Australia, and is irritating to the eyes, skin, and respiratory system[6].

While ethylene oxide is not an intentionally added ingredient to product formulations, it is used in the synthesis of other ingredients that are. Once synthesized, ethoxylated ingredients can be contaminated with residual carcinogens ethylene oxide or 1,4-dioxane, both by-products of ethoxylation).

There is limited data on the levels of ethylene oxide in the environment and no data available as to its bioaccumulation in the tissues of marine organisms[12]. As such, data on the general population’s exposure to ethylene oxide is scarce; industrial workers and sterilization technicians are likely at higher risk of exposure. General exposure to ethylene oxide can also occur through tobacco smoke[12].

Due to the known human health effects of ethylene oxide, as well as the effects of ethoxylation by-products, such as 1,4-dioxane, ethoxylated ingredients are best avoided.

How to Avoid It

Consumers can read labels to identify and avoid relevant ingredients. to avoid ethylene oxide. Because ethylene oxide itself won’t appear on ingredient lists, focus on avoiding ingredients that are commonly made using ethoxylation and may carry residual contaminants.

Avoid PEG compounds, which are usually listed as “PEG” followed by a number on labels.

Skip polysorbates, ingredients that are listed on labels as “Polysorbate” followed by a number.

Look for and avoid chemicals that end in “oxynol” or “eth”, as this denotes ethoxylation. Examples include: nonoxynol-9, octoxynol-9, octoxynol-10, ceteareth, oleth, laureth, pareth, and steareth.