Polyethoxylated tallow amine
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Polyethoxylated tallow amine (also polyoxyethylene tallowamine, POE-tallowamine) refers to a range of non-ionic surfactants derived from animal fats ( tallow). They are a class of polyethoxylated amines (POEAs). The abbreviation 'POEA' is often erroneously used to refer to POE-tallowamine. They are used primarily as emulsifiers and wetting agents for
agrochemical An agrochemical or agrichemical, a contraction of ''agricultural chemical'', is a chemical product used in industrial agriculture. Agrichemical refers to biocides ( pesticides including insecticides, herbicides, fungicides and nematicides) an ...
formulations, such as
pesticides Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampric ...
and
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
s (e.g. glyphosate).


Synthesis

Animal fat is hydrolysed to give a mixture of free fatty acids, typically
oleic Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...
(37–43%),
palmitic Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The Li ...
(24–32%),
stearic Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "''stéar''", which means tallow. ...
(20–25%), myristic (3–6%), and
linoleic Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt or ester of this acid. L ...
(2–3%). These are then converted to fatty amines via the
nitrile process In chemistry, a fatty amine is loosely defined as any amine possessing a mostly linear hydrocarbon chain of eight or more carbon atoms. They are typically prepared from the more abundant fatty acids, with vegetable or seed-oils being the ultimate ...
before being
ethoxylated Ethoxylation is a chemical reaction in which ethylene oxide adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates. In the usual application, alcohols and phenols are converted in ...
with ethylene oxide; this makes them water-soluble and amphiphilic. The length of the fatty tail and degree of exothylation will determine the overall properties of the
surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
. Due to it being synthesized from an impure material POEA is itself a mixture of compounds.


Composition and use

The
polyethoxylated Ethoxylation is a chemical reaction in which ethylene oxide adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates. In the usual application, alcohols and phenols are converted ...
tallow amine used as a
surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
is referred to in the literature as MON 0139 or polyoxyethyleneamine (POEA). It is contained in the herbicide
Roundup A roundup is a systematic gathering together of people or things. Roundup, Round Up or Round-up may also refer to: Agriculture * A muster (livestock) (AU/NZ) or a roundup (US/CA) is the process of gathering livestock. * Roundup (herbicide), a M ...
. An ethoxylated tallow amine (CAS No. 61791-26-2), is on the United States Environmental Protection Agency List 3 of Inert Ingredients of Pesticides." Roundup Pro is a formulation of glyphosate that contains a "phosphate ester neutralized polyethoxylated tallow amine" surfactant; as of 1997 there was no published information regarding the chemical differences between the surfactant in Roundup and Roundup Pro. POEA concentrations range from <1% in ready-to-use glyphosate formulations to 21% in concentrates. POEA constitutes 15% of Roundup formulations and the phosphate ester neutralized polyethoxylated tallow amine surfactant constitutes 14.5% of Roundup Pro. Surfactants are added to glyphosate to allow effective uptake of water-soluble glyphosate across plant cuticles, which are hydrophobic, and reduces the amount of glyphosate washed off plants by rain.


Environmental effects

The chemical complexity of POEA makes it difficult to study in the environment.Dean G. Thompso
Ecological Impacts of Major Forest-Use Pesticides
Ecological Impacts of Toxic Chemicals, Bentham Science Publishers Ltd, 2011, Chapter 5, 88-110. quote"...owing to the chemical complexity of the POEA surfactant and resultant difficulty in analysing for it in complex environmental matrices, the environmental behaviour of POEA in natural forest ecosystems has not been specifically studied."
POEA is toxic to aquatic species like fish and amphibians. Like other surfactants, it can affect
membrane transport In cellular biology, membrane transport refers to the collection of mechanisms that regulate the passage of solutes such as ions and small molecules through biological membranes, which are lipid bilayers that contain proteins embedded in them. Th ...
and can often act as a general
narcotic The term narcotic (, from ancient Greek ναρκῶ ''narkō'', "to make numb") originally referred medically to any psychoactive compound with numbing or paralyzing properties. In the United States, it has since become associated with opiates ...
. In laboratory experiments POEA has a half-life in soils of less than 7 days. Washout from soil is assumed to be minimal, and the estimated half-life in bodies of water would be about 2 weeks. Field experiments have shown that the half-life of POEA in shallow waters is about 13 hours, "further supporting the concept that any potential direct effects of formulated products on organisms in natural waters are likely to occur very shortly post-treatment rather than as a result of chronic or delayed toxicity." A review of the literature provided to the EPA in 1997 found that POEA was generally more potent in causing toxicity to aquatic organisms than glyphosate, and that POEA becomes more potent in more
alkaline In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as ...
environments. (Potency is measured by the
median lethal dose In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the ...
(LD50); a low LD50 means that just a little of the substance is lethal; a high LD50 means that it takes a high dose to kill.) Glyphosate has an LD50 ranging from 4.2 times that of POEA for midge larvae at pH 6.5, to 369 times that of POEA for rainbow trout at pH 9.5 (for comparison, at pH 6.5 the LC50 of glyphosate was 70 times that of POEA for rainbow trout).Gary L. Diamond and Patrick R. Durki
Effects of Surfactants on the Toxicitiy of Glyphosate, with Specific Reference to RODEO
Report submitted to Leslie Rubin, COTR, Animal and Plant Health Inspection Service (APHIS). Biotechnology, Biologics and Environmental Protection, Environmental Analysis and Documentation, United States Department of Agriculture, February 6, 1997
The pH value of most freshwater streams and lakes is between 6.0 and 9.0; fish species are harmed by water having a pH value outside of this range.


Human toxicity

A review published in 2000 examining the toxicity of POEA and other components in glyphosate formulations found "no convincing evidence for direct DNA damage in vitro or in vivo, and it was concluded that Roundup and its components do not pose a risk for the production of heritable/somatic mutations in humans. ...Glyphosate, AMPA, and POEA were not teratogenic or developmentally toxic. …Likewise there were no adverse effects in reproductive tissues from animals treated with glyphosate, AMPA, or POEA in chronic and/or subchronic studies."Williams GM, Kroes R, Munro IC
Safety evaluation and risk assessment of the herbicide Roundup and its active ingredient, glyphosate, for humans
Regul Toxicol Pharmacol. 2000 Apr;31(2 Pt 1):117-65. Review.
Another review, published in 2004,Bradberry SM, Proudfoot AT, Vale JA
Glyphosate poisoning
Toxicol Rev. 2004;23(3):159-67. Review. (subscription required)
said that with respect to glyphosate formulations, "experimental studies suggest that the toxicity of the surfactant, polyoxyethyleneamine (POEA), is greater than the toxicity of glyphosate alone and commercial formulations alone. There is insufficient evidence to conclude that glyphosate preparations containing POEA are more toxic than those containing alternative surfactants. Although surfactants probably contribute to the acute toxicity of glyphosate formulations, the weight of evidence is against surfactants potentiating the toxicity of glyphosate."


References

Non-ionic surfactants