2,2'-(octadecylimino)bisethanol

Endpoint summary

Description of key information

PNEC aqua (freshwater)		0.161	µg/L
PNEC intermittent release		0.1	µg/L
PNEC aqua (marine water)		0.0161	µg/L
PNEC aqua (marine water) intermittent release		0.01	µg/L

Additional information

Primary fatty amine ethoxylates (PFAEO) are cationic surfactants. Aquatic ecotoxicity testing of cationic surfactants is complicated as these substances are in most cases multicomponent mixtures (UVCB’s) with a range of relatively low water solubilities which sorb to equipment and organisms. These substances are therefore considered as difficult substances for which the results of standard guideline studies are very difficult to interpret when considering them in a standard way.

OECD Guidance Document 23 on aqueous-phase toxicity testing of difficult test chemicals (Feb. 2019), advices to use the Water Accommodated Fraction (WAF) approach for these UVCB substances. The aquatic ecotoxicity studies were therefore performed according to this approach.

Per definition of the WAF approach, all terms related to concentration level should be given as loading rates (mass-to-volume ratio of the substance to the medium) because partly dissolved compounds and mixtures cannot be related to concentrations. Analytical verifications of selected components can be helpful and deliver supporting information, but they do not represent the whole test substance and therefore, toxicity results were evaluated based on WAF loading rate (Wheeler, Lyon et al. 2020). Several guidance documents suggest to use the WAF loading rate for the environmental hazard classification of chemical substances e.g. the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (OECD 2002, OECD 2019) as well as OECD guidance documents on the classification of chemicals which are Hazardous for the Aquatic Environment.

The test item concentrations of PFAEO were as indicated in OECD GD 23 analytically verified via LC-MS/MS during the tests in the fresh media at the start of an exposure-renewal interval as well as in the old media at the end of an exposure-renewal interval (frequency depending on test type). Quantification of the dissolved concentration of the test substance is however problematic for cationic surfactants especially in test solutions where algae are present. Cationic surfactants were observed to sorb strongly to algae (van Wijk et al., 2009). Removal of algae requires either filtration or centrifugation and at the very low test concentrations applied there is a relatively large loss (factor ±10 concentration reduction) of substance due to the required separation step, despite of precautions taken to limit the loss e.g. by the rinsing of the equipment.  This means that an accurate quantification of the dissolved concentration in these studies is not possible. Ecotoxicity testing with these difficult substances according to the WAF approach leads for algae and long-term daphnia tests to test results which are poorly reproducible and are associated with high uncertainty. In addition, daphnids are in the long-term test due to the strong sorption to food algae mainly exposed to PFAEO via ingestion of algae which means that focusing only on the dissolved concentration for the dose response will lead to unrealistically low EC values for these studies.

Because of the complex sorption mechanisms (van der Waals and Ionic mechanisms) of these cationic surfactants the actual dissolved exposure concentration cannot reliably be predicted as the equilibrium partitioning method assumes that partitioning is only occurring to organic carbon.

Both the problematic quantification of the exposure concentrations during the aquatic ecotoxicity tests for the effect assessment and the incorrect prediction of the dissolved concentrations for the exposure assessment has resulted to the use of the Bulk approach for testing cationic surfactants. The Bulk approach as described in ECETOC Technical Report “Environmental Risk Assessment of difficult substances” (TR 88, 2003) is less suitable for C&L purposes but perfectly suited to derive a realistic risk ratio for the aquatic compartment because the partitioning of cationic surfactants to soil, sediment or suspended matter is rather complex which explains why there is no alternative Equilibrium Partitioning Method (EPM, di Toro, 2008) formula for these substances available yet. The use of the Bulk approach however elegantly bypasses this deficiency as it eliminates the EPM on the exposure and effect side. (More details on the Bulk approach are attached to the dossier).  Besides to the results of aquatic ecotoxicity tests performed according to the WAF approach, results obtained according to the Bulk approach are presented in the Table below. The Bulk approach tests were specifically performed where the biggest problems with quantification of the exposure concentrations would be expected i.e. the algae and long term daphnia test.

More details on the use of the bulk approach are described in a document attached to IUCLID chapter 13.

PFAEO-C18 (2,2'-(octadecylimino)bisethanol, EC 233-520-3, CAS 10213-78-2)
	nominal		TWA
	EC(L)50/L(L)C50	EC10/NOEC	EC50	EC10/NOEC
	(µg/L)	(µg/L)	(µg/L)	(µg/L)
Algae test (2021)	2560	772
WAF approach static
Noack
CAS no.: 10213-78-2
Short term daphnia test (2021)	26600		23.7
WAF approach semi-static
Noack
CAS no.: 10213-78-2
Acute fish test (2009)			100
Diluted stock solution static
Arkema
read-across (CAS 25307-17-9, PFAEO-O)
Long-term fish (2022)	16.8 post-hatch survivial	3.5	10.7 post-hatch survivial	1.6 fry growth weight
WAF approach semi-static
Noack
read-across (CAS 25307-17-9, PFAEO-O)
Long-term fish (2021)		13.4		14.3 fry growth weight
Flow-through
Noack
read-across (CAS 71786-60-2, PFAEO-C)
Long-term daphnia test (2022)		<1560		<1.53	*
Flow-through
Noack
CAS no.: 10213-78-2
Toxicity to microorganisms (2010)	167000	35000
Geerts (2010)
3h-Ecx
CAS no.: 90367-28-5 (Old CAS no.)

* Concentration range will be extended or study will be repeated.

 

• Di Toro, D 2008 Bioavailability of chemicals in Sediments and soils: toxicological and chemical interactions. SERDP/ESTCP Bioavailability workshop


• van Wijk, D., Gyimesi-van den Bos, M., Garttener-Arends, I., Geurts, M., Kamstra, J., Thomas, P., 2009. Bioavailability and detoxification of cationics, I. Algal toxicity of trimethylammonium salts in the presence of suspended matter and humic acid. Chemosphere 75 (3), 303–309.

• OECD (2002). Guidance Document on the Use of the Harmonised System for the Classification of Chemicals which are Hazardous for the Aquatic Environment.


• Wheeler, J. R., D. Lyon, C. Di Paolo, A. Grosso and M. Crane (2020). "Challenges in the regulatory use of water-accommodated fractions for assessing complex substances." Environmental Sciences Europe 32(1): 1-10.


• OECD (2019): Guidance document on aqueous-phase aquatic toxicity testing of difficult test chemicals. OECD series on testing and assessment no. 23 (second edition), ENV/JM/MONO(2000)6/REV1