Imidazolium compounds, 2-C17-unsatd.-alkyl-1-(2-C18-unsatd. amidoethyl)-4,5-dihydro-N-methyl, Me sulfates

Toxicity to aquatic algae and cyanobacteria

Description of key information

Three studies on algal growth inhibition according to OECD Guideline 201 are available.

From these studies the acute effect concentration 72h ErC50 of > 400 µg/L and 330 µg/L are available. Two studies made with the registration substance provide deviating results for the 72h NOEC of 178 µg/L and 30 µg/L . However, the test item used to derive the lower 72h NOEC contains 24% isopropanol. Caused by the solvent, the water solubility and presumably the bioavailability of the test substance is elevated. The better bioavailability of the substance for the test organisms is expected to result in higher toxicity. The test result for the mixture of registration substance and isopropanol is not comparable to the test made with the pure substance. The 72h NOEC of 30 µg/L is therefore not considered for the assessment. The 72h NOEC of 178 µg/L is considered to be more reliable. In addition a long-term Coupled OECD Confirmatory test (5 weeks) for algae under flow through conditions for the closely related partially unsaturated IQAC, DMS quaternised is available. During the 35d exposure there was no change observed in the measured density of the algae cultures exposed to the test substance doted activated sludge unit. The 35d NOEC was determined to be > 100 µg/L, which is well in tune with the 72 h NOEC of the solvent-free oleic-acid based IQAC, DME quaternised. The Coupled OECD Confirmatory test is considered to be the better model for field conditions in surface waters at the outlet of sewage treatment plants and provide a more realistic scenario of exposure of algae.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

100 µg/L

Additional information

In an Alga, Growth Inhibition Test according to OECD 201 with Pseudokirchneriella subcapitata exposed to the test item the respective 72h EC50 values for growth rate and yield were calculated to be > 400 µg act. ingr. /L (highest test concentration) and 356 µg act. ingr. /L. The 72h EC10 values were calculated to be 277 and 181 µg act. ingr. /L for growth rate and yield, respectively. The NOEC values for growth rate and yield were estimated to be 178 and 79 µg act. ingr. /L. However, at the LOEC concentration of 267 µg/L for effects on growth rate, the inhibition was only 8.1% compared to the controls. This value was statistically significant due to the low variability of the control replicates (1.5 % CV). Since effects below 10 % are generally not considered to be ecotoxicological relevant, it is recommended to use the growth rate EC10 of 277 µg act. ingr. /L as relevant endpoint for the long-term aquatic risk assessment (NOEC).

In a second test, the algal toxicity of Oleic-acid based IQAC, DMS quaternised was also determined to be very toxic to the growth of the alga Selenastrum capricornutum, with a 72-h EC50 value of 330 μg/L. No significant effect (NOEC) on growth of the green alga was observed at concentrations of 30 μg/L or less. The product contains 24% of isopropanol. Caused by the solvent, the water solubility and presumably the bioavailability of the test substance is elevated. The better bioavailability of the substance for the test organisms is expected to result in higher toxicity. The test result for the mixture of registration substance and isopropanol is not comparable to tests made with the pure substance. The derived NOEC is therefore not used for the assessment. In the first study the test substance is solvent-free . This study is considered to be more reliable.

In an acute test according to DIN 38 412 Part 9 with the read across substance partially unsaturated IQAC, DMS quaternised, Algae were less sensitive. The EC50 was determined to be EC50 (72 h): ca. 1800 — 4500 µg/L act. ingr. (nominal). This value is based on the biomass and therefore not used for the assessment.

In a 5 weeks long-term toxicity study in a Coupled OECD Confirmatory Test the cultures of Scenedesmus subspicatus CHODAT (new name: Desmodesmus subspicatus) were exposed to the degradation products of the closely related partially unsaturated IQAC, DMS quaternised (CAS 86088-85-9) of an activated sludge unit at 24 °C. There was no change in the measured extinction of the algae cultures exposed to the surfactant doted activated sludge unit during the test period of 5 weeks. Only minor variation was observed. The mean extinction was 0.75 E. Visual inspection of the alga cultures showed optimal green coloured cultures, an indication of high active chlorophyll. Sedimentation of algae was not observed. The culture remained stabile over 5 weeks and no negative effects were observed. In comparison the control culture was somewhat labile, so that it could be concluded that the algae culture exposed to the degradation products was slightly promoted. During the test the read across substance, partially unsaturated IQAC, DMS quaternised, is eliminated in the model activated sludge unit by > 90%. The elimination is calculated to be 97.75% taking into account the inflow into the model activated sludge unit of the test substance with a concentration of 10 mg/l, the dilution of the effluent of the elimination unit in ratio 1:1.25 and the separately determined EC0=0.1 mg/l. Thus a NOEC of >100 μg/L is calculated.

This toxicity study is classified as assignable, though only few data are reported. As a precautionary measure a NOEC of 100µg/L is choosen.

Justification for read-across:

The structural similarities between the source and the target substances presented above are the basis for the read-across hypothesis. Adequate, reliable and available scientific information indicates that the source and target substances have similar physicochemical properties, ecotoxicological and toxicity profiles and thus support the read-across hypothesis.

Both substances are UVCB substances, produced by a similar process resulting in main constituents of the same structure, varying in the degree of saturation and chain length (C16 and C18 and mainly C18, for source and target substance, respectively). Given the underlying identical generic structure (outlined in chapter 1 and 2), similar absorption following oral or dermal uptake and the same metabolic patterns are expected for source and target substance. The findings from toxicokinetic data confirm that the discussed IQAC source and target substances are only poorly absorbed after oral application and rapidly excreted. There was no tendency for accumulation of the substance in the body of the test animals.

In conclusion the results obtained from source substance (partially unsaturated IQAC, DMS quaternised) are considered a reliable source to cover endpoints of the target substance (oleic-acid based IQAC, DMS quaternised). Beyond, the dose descriptors obtained from these studies performed on the source substance are considered as an appropriate starting point for deriving the respective PNECs.

A more detailed justification for read-across is outlined in a separate document:

“Justification for read-across - toxicological information”, is attached to the endpoint summary acute toxicity and provided in chapter 13 of Technical dossier.