1,4-Dioxane in Ethoxylated Surfactants: A Guide to Regulation, Analytics, and Application

If you formulate cosmetics, laundry detergents or household cleaners containing ethoxylated surfactants (SLES, ALES, ethoxylated alcohols), you have likely already encountered the topic of 1,4-dioxane content. This substance is formed as a by-product of ethoxylation and is drawing increasing attention from regulators and consumers alike.

An issue that (so far) is not widely discussed

1,4-dioxane is classified as a potential carcinogen. Although its concentrations in surfactants are typically low (on the order of ppm), regulatory requirements are gradually tightening and manufacturers face growing pressure to reduce levels further. For formulators, this raises a clear question: how can you ensure product safety while also meeting regulatory limits?

The regulatory reality across global markets

Requirements differ significantly by region and are often tightened step-by-step depending on local priorities (consumer protection vs. protection of the aquatic environment; exposure-based approaches vs. limits directly in products).

European Union (EU)

In the EU, market pressure in practice is to keep 1,4-dioxane in raw materials and finished products as low as possible (typically single-digit to tens of ppm depending on the application). At the same time, it is worth noting that in 2023 the German competent authority opened a “call for evidence” for a planned restriction under REACH, which worked with a very strict limit of 1 mg/kg in “surfactant active matter” (i.e., 1 ppm).

This intention was subsequently withdrawn on 20 August 2025; according to ECHA, the German authorities want to first assess new information on emission pathways of the substance into the environment and consider the next regulatory steps.

United States (federal vs. state level)

At the federal level, regulation often focuses primarily on exposure (for example, California’s Proposition 65 uses a warning threshold of 30 µg/day of exposure), which in practice can push towards very low concentrations in finished products depending on the use scenario.

In addition, some states impose product-content limits—most notably New York State, which is among the strictest and sets the following limits:

• Household cleansing and personal care products: max 2 ppm from 31 Dec 2022 and max 1 ppm from 31 Dec 2023
• Cosmetic products: max 10 ppm from 31 Dec 2022

Practical note on converting “ppm in a raw material” vs. “ppm in the finished product”

Limits are defined in different ways (in the raw material / in the active matter / in the finished product). As a quick rule of thumb: if you use 70% SLES with 10 ppm (as supplied, “tel quel”) and dose it into a shampoo at 10% active matter, the contribution from this raw material to the finished product is roughly 1 ppm (because 10% of 10 ppm = 1 ppm). With strict requirements such as 1 ppm in the finished product, compliance often depends not only on the “purity of the raw material”, but also on dosage rate and on the combined contribution of multiple ethoxylated ingredients.

Asia

Asian markets have their own rules. In China, NMPA emphasizes testing and documentation as part of cosmetics registration. South Korea is gradually tightening requirements within K-beauty/K-cosmetics standards (often also driven by market expectations and documentation requirements).

Practical implications for exporters

The same product may be subject to different specifications depending on the target market. If you aim for a “global SKU”, it is often beneficial to follow the strictest relevant requirement (typically a combination of limits such as New York’s 1 ppm for selected categories and exposure-based requirements in the target market).

Technical background: formation and control of 1,4-dioxane

1,4-dioxane is formed during ethoxylation as a by-product when ethylene oxide reacts with fatty alcohols. The amount depends on reaction conditions—temperature, pressure, catalyst, and reaction time. During subsequent sulfation of the ethoxylated alcohol, 1,4-dioxane carries over into the resulting sulfate (typically SLES).

Modern manufacturing uses two main approaches to reduce 1,4-dioxane:

• prevention through optimization of the ethoxylation process,
• reduction through post-reaction techniques.

One such technique is vacuum steam stripping, which we also use at ENASPOL. As standard, we are able to achieve levels below 20 ppm; for the low-dioxane grade, below 10 ppm (tel quel in a 70% product). On customer request we can also achieve levels below 5 ppm, which is naturally associated with higher costs.

The difference between standard and controlled ethoxylation/sulfation can be tens to hundreds of ppm. That is why it is important to ask suppliers not only for a typical value, but also for batch-to-batch consistency.

Analytics and interpretation of results

The standard method for determining 1,4-dioxane is gas chromatography (GC-MS or GC-FID) according to ISO/ASTM standards. A typical detection limit is around 0.5–1 ppm.

A certificate of analysis (CoA) should include the measured value, the method used, the detection limit, and the date of analysis. Batch-to-batch consistency is critical—if a supplier declares <10 ppm, ask for the range of results in recent batches. A responsible manufacturer will have statistical data available.

How ENASPOL controls 1,4-dioxane

ENASPOL approaches this topic proactively. We regularly test our sulfated products using accredited methods and guarantee limits according to market requirements—standardly <20 ppm, and for more demanding applications <10 ppm or <5 ppm.

We provide every customer with full documentation, including a CoA with current results. Our technical specialists help select the right product for the application and target market. Exporting to the USA? We can support you with Prop 65 requirements. Entering the Chinese market? We can prepare documentation for NMPA.

We recognize that higher purity means higher costs. That is why we openly discuss with customers where strict specifications are necessary and where standard quality is sufficient.

Practical tips for formulators

• Request from your supplier: a CoA for every batch, the analytical method specification, and historical data demonstrating consistency.
• Set internal specifications: define limits by product category (facial cosmetics typically require stricter control than industrial cleaners).
• Communicate proactively: have fact-based, data-supported answers ready for customer questions.
• Monitor regulation: requirements are tightening—what is sufficient today may be insufficient in two years.

Controlling 1,4-dioxane is not a rarity, but a standard of responsible manufacturing. Choosing a supplier who takes this seriously is an investment in the safety of your products and your brand.

Do you need consultation on 1,4-dioxane in your formulations? Our technical team is ready to answer your questions and propose the optimal solution for your specific market.