1,4-dioxane in shampoo: New York's 1 ppm limit, ethoxylated surfactants and how to test

01New York's 1,4-dioxane limits

New York amended its Environmental Conservation Law to cap 1,4-dioxane in products sold in the state. The limits were phased in over two years [1]:

DEC proposed implementing rules (6 NYCRR Subpart 352-1) on 6 December 2023 and adopted them on 18 September 2024 [1], [2]. The rules set out how compliance is evaluated, including analytical testing of the product under section 352-1.6. Waivers gave some manufacturers extra time, but DEC states that no waiver is effective after 30 December 2025 [1].

The driver is groundwater. 1,4-dioxane is persistent and mobile in water, and it has been found in Long Island's sole-source aquifer [2].

02Why ethoxylation creates 1,4-dioxane

Ethoxylation adds ethylene oxide to a fatty alcohol to build a polyethylene glycol chain. The chain makes a surfactant milder, more water-soluble and better at foaming. Under heat and acid, especially during the sulfation step that turns an alcohol ethoxylate into SLES, two ethylene oxide units can close into a six-membered ring. That ring is 1,4-dioxane, a manufacturing by-product rather than an added ingredient [3].

Suppliers remove most of it by vacuum stripping: the surfactant is held under reduced pressure, often with steam or nitrogen sparging, so the volatile dioxane boils off. FDA has recommended this step to manufacturers [3]. How well and how consistently a supplier strips decides how much reaches your bottle, so two lots with the same INCI name can differ.

03Which surfactants carry the risk

FDA lists ingredient names containing "PEG", "polyethylene", "polyoxyethylene", "-eth-" or "-oxynol-" as possible sources [3]. The table ranks the common families by typical risk; the real figure for your lot is the one on its CoA.

Risk adds up across the formula. A shampoo with SLES, a PEG thickener and a polysorbate solubiliser has three sources, and all three count toward the 1 ppm total. High risk does not mean non-compliant: well-stripped SLES can support a finished product below 1 ppm when the supplier's specification proves it.

04How to keep every batch under 1 ppm

1. Tighten supplier specs and CoA limits

   Ask every supplier of an ethoxylated ingredient for a 1,4-dioxane specification and a batch Certificate of Analysis with a measured value, not just "complies". Work backwards from the limit: if SLES is used at 12% (as supplied) and is the only source, the raw material must sit at or below about 8 ppm before any safety margin (1 ppm ÷ 0.12).

2. Move to low-dioxane grades

   Major surfactant makers sell grades stripped harder and specified low in dioxane. They cost more, but they are usually the fastest route because they need little or no reformulation.

3. Swap to non-ethoxylated systems

   For new launches, a sulfate-free base removes the source entirely. Common pairs are sodium cocoyl isethionate with cocamidopropyl betaine, or glutamate and glucoside blends. Expect harder thickening, lower foam and new pH and preservative windows, so plan full stability testing.

4. Check the whole formula

   Fragrance, solubilisers and PEG conditioning agents each add a little. A finished-product test catches what raw-material specs miss.

05How to test with headspace GC-MS

Measuring 1 ppm in a foamy, surfactant-heavy sample needs real analytical chemistry. The standard approach is headspace GC-MS. The sample is sealed in a vial and heated so dioxane moves into the gas above it. That gas goes into the gas chromatograph, and the mass spectrometer confirms the compound by its fragment ions. A deuterated internal standard (1,4-dioxane-d8) corrects for matrix effects [4].

A sound testing programme covers five points:

• 01
  Low quantitation limit. A "<1 ppm" result from a method that cannot quantify below 1 ppm tells you nothing about your margin. Headspace GC-MS methods report quantitation limits of about 0.01 ppm (9–13 ppb) [4], so ask for 0.1 ppm or lower.
• 02
  DEC-aligned method. Confirm the laboratory's procedure meets the requirements in section 352-1.6 [1].
• 03
  Accredited laboratory. Use an ISO/IEC 17025-accredited laboratory with the method on its scope.
• 04
  Test on change. Test at first production, after any supplier or grade change, and periodically after that.
• 05
  Keep the paper trail. File CoAs, specifications and reports together to show due diligence to retailers and regulators.

06Build compliance into the formula

New York's limits are fully in force [1]. Brands selling rinse-off products there need 1 ppm built into the formula: well-stripped or low-dioxane surfactants, firm CoA limits, and headspace GC-MS testing as the final check. Brands that start at the raw-material specification rarely have problems at the testing stage. If you also sell in the EU or UK, the same documentation supports your US and EU safety files.

07Questions readers ask

08References

1. New York State Department of Environmental Conservation. 1,4-Dioxane limits for household cleansing, personal care and cosmetic products. Accessed 16 October 2026. NYSDEC
2. Personal Care Insights. Toxin takedown: New York pioneers 1,4-dioxane ban in household and personal care products. 24 September 2024. Personal Care Insights
3. US Food and Drug Administration. 1,4-Dioxane in cosmetics: a manufacturing byproduct. Accessed 16 October 2026. FDA
4. Agilent Technologies. Determination of 1,4-dioxane in consumer products by headspace GC/MS. Application note 5994-3220EN. Agilent PDF

This article is general technical information, not legal, regulatory or medical advice. Confirm requirements for your product and market before launch.