Nonylphenol Ethoxylates

What are NPEs, and are they still allowed in organic crop production?

By Meagan Campbell

Nonylphenol ethoxylates (NPEs) are a commonly used group of synthetic surfactants. Surfactants are compounds that help decrease surface tension, and can help different substances mix together if they naturally repel each other. NPEs are used in a wide variety of products, including cleaning and degreasing products, paints, lubricants, epoxy, and pesticides.

Surfactants formulated with NPEs are added at the time of mixing pesticides or sprays, because their hydrophilic heads and hydrophobic tails may join water and water-insoluble substances together. They may also serve as wetting agents. The higher an NPE’s molecular weight, the greater its water solubility, or the easier it is to dissolve in water. Given the way that these products are applied, NPEs are prevalent in the environment, moderately bioaccumulative, toxic to aquatic organisms, and eventually degrade into nonylphenol, a compound known by the Environmental Protection Agency to be more toxic than the original NPE.

Around 2014, two separate issues arose regarding the use of NPEs in USDA organic production. Both concerned the allowance of NPEs as inert ingredients under §205.601(m)(1) and (2) on the National List of National List of Allowed Substances.

Firstly, surfactant manufacturers reevaluated CAS Registry Number (CAS, or CAS RN) assignments for some NPE substances. CAS RNs are helpful tools to identify specific chemical substances. Two NPEs in particular, polyoxyethylene nonylphenol (9016-45-9) and p-nonylphenol, ethoxylated (26027-38-3), were historically described with linear chemical structures. Each substance had been previously assigned a CAS RN that also appeared on the 2004 EPA List of Inerts. However, we learned that NPEs identified with these two CAS RNs are incorrectly identified. Instead, commercially available forms are chemically branched and more accurately identified by CAS RN: 127087-87-0, a 2004 EPA List 3 inert.

Given the previous confusion surrounding CAS RN reassignments, OMRI currently considers the commercial avail-ability and use of NPEs identified by CAS RN: 9016-45-9 or 26026-38-3 as a "Beyond Resolution" issue, and will no longer review products reporting the use of those NPEs, pending clarification from the National Organic Program. 

Secondly, the National Organic Standards Board (NOSB) discussed the possible prohibition of NPEs in USDA organic production as part of the “Sunset Review” of 2004 EPA List 4 inerts in 2020 and 2024. Environmental concerns about using NPEs led the EPA to publish in 2010 a “Nonylphenol (NP) and Nonylphenol Ethoxylates (NPE) Action Plan.” This action plan calls for an industry-wide phase-out of these chemical compounds. The 2015 Technical Evaluation Report on NPEs included reference to the EPA action plan, which led to the possibility of the NOSB recommending the prohibition of NPEs. As of 2024, the NOSB has not yet officially recommended prohibiting NPEs to the NOP.

This article was originally published in the winter 2020 edition of the OMRI Materials Review newsletter, and was revised in December 2024 by Research and Education Manager Peter Bungum.