N,N'-bis{3-[di-(branched and cyclic) alkylamino]alkyl}alkanediamide

Endpoint summary

Description of key information

The substance is a cationic surfactant type molecule with a low estimated CMC which accounts for the lack of ready biodegradation (16% in 28 days) observed. Algae, like sewage sludge micro-organisms, are anionic and therefore it is likely that in the WAF, these cationic molecules surround the relatively small number of algae that are in the solution, reducing their capacity to take up minerals and potentially even blocking active sites. Considering the results of the algal study, it appears that the critical concentration is somewhere >1 mg/L loading rate WAF.

In the environment it is unlikely that this situation would occur as the substance would be totally adsorbed to suspended solids, sediment and organic matter before it could reach a concentration effecting algal cells.

Although there would be a similar effect in the ASRI, with sewage sludge micro-organisms, the impact is mitigated due to hydrophobicity and therefore the effect is minor in comparison to that observed in the algal study.

As the 1.0 mg/L loading rate is much higher than the experimentally derived water solubility of the substance (less than 2.04E-06 g/L) the result of the study should not be used for determination of the PNEC, risk assessment or for the purpose of Classification and Labelling.

Fish

Daphnia

A key study was performed to assess the acute toxicity of the test item to Daphnia magna. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (April 2004) No 202, 'Daphnia sp., Acute Immobilisation Test' referenced as Method C.2 of Commission Regulation (EC) No. 440/2008.

Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to a Water Accommodated Fraction (WAF) of the test item at single nominal loading rate of 100 mg/L for 48 hours at a temperature of 21 °C to 22 °C under static test conditions. The number of immobilized Daphnia and any adverse reaction to exposure were recorded after 24 and 48 hours.

Exposure of Daphnia magna to the test item gave EL*50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L loading rate WAF.

Total Organic Carbon (TOC) analysis of the fresh media at 0 hours showed a measured concentration of 2.55 mgC/L. Analysis of the old media at 48 hours showed a measured concentration of 0.39 mg/L.

Given that the toxicity cannot be attributed to a single component or a mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.

*EL = Effective Loading Rate

Algae

A key study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed that described in the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

Due to the low aqueous solubility and pure nature of the test item, for the purposes of the definitive test, the test medium was prepared as a slow stir saturated solution. Following preliminary range-finding tests and an initial test, Pseudokirchneriella subcapitata was exposed to WAFs of the test item at nominal loading rates of 0.01, 0.32 and 1.0 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

Chemical analysis of the test preparations at 0 and 72 hours showed measured test concentrations of less than the LOQ (0.00090 mg/L) of the analytical method used. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less thanthe LOQ.

Given that the toxicity cannot be attributed to a single component or to a mixture of components but tothe test item as a whole, the results were based on nominal loading rates only.

Exposure of the test item to Pseudokirchneriella subcapitata gave EL50 values greater than the 1.0 mg/L loading rate WAF. The No Observed Effect Concentration was 1.0 mg/L loading rate WAF.

The study showed that the test item was not toxic to algae at a concentration in excess of the water solubility of the substance.

Sewage sludge micro-organisms

A key study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2010) No. 209 "Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)".

Activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 10, 100 and 1000 mg/L (3 replicates of the 1000 mg/L test concentration) for a period of 3 hours at a temperature of approximately 20 °C with the addition of a synthetic sewage as a respiratory substrate. The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L. It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/L. The reference item gave a 3-Hour EC50 value of 7.2 mg/L, 95% confidence limits 5.5 - 9.4 mg/L.