Amines, N-(3-aminopropyl)-N'-(C16-18 and C18-unsatd. alkyl)trimethylenedi-

Toxicity to aquatic algae and cyanobacteria

Description of key information

One algae study with N-(3-aminopropyl)-N'-C16-18 (evennumbered), C18 unsaturated alkyl -propane-1,3-diamine (CAS 1219458-14-6) is available.

Abbreviation: Triamine T

Triamine T is a multicomponent mixture (UVCB) of cationic surface-active constituents with different water solubilities. The fate of cationic surfactants in general deviates from standard chemicals. 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. The reasons are the intrinsic properties like the relatively low water solubility and strong sorption to equipment and organisms. Classical ecotoxicity testing with these substances using reconstituted water often leads to test results which are poorly reproducible and are associated with high uncertainty. In addition, because of the complex sorption mechanisms (van der Waals and Ionic mechanisms) the actual dissolved exposure concentration cannot reliably be estimated.

To determine the intrinsic toxicity of Triamine T (for C&L purposes) an algae test (OECD TG 201) is performed according to the Water Accommodated Fraction (WAF) approach as described in “OECD guidance document on aqueous-phase aquatic toxicity testing of difficult test chemicals” (No. 23 Feb. 2019) with a daily refreshment of the test solutions. The term “loading rate” is advocated to express exposure to a WAF and is considered analogous to the nominal concentration.

For the preparation of the test solutions according to the WAF approach, all reasonable efforts were taken to produce a solution of all soluble components of the test item in test media. The test solutions were prepared daily, by gentle mixing the test item with test medium for a prolonged period sufficient to ensure equilibration between the test item and the water phase. At the completion of mixing and following a settlement period, the WAF was separated by siphoning. This procedure was followed for each renewal of the test solutions. Five WAFs were prepared and tested at nominal loading rates 10.0 – 17.8 – 31.6 – 56.2 – 100 µg//L (separation factor ~1.78), corresponding to the time weighted mean measured test item concentrations 0.364 – 0.421 – 0.892 – 2.08 – 4.76 µg/L.
No undissolved or emulsified material was observed in the WAF solutions based on the Tyndall effect check. Adsorptive losses to the glass test vessels were kept as low as possible by pre-conditioning the test vessels already with appropriate test solution for at least 12 hours under test conditions. Before the start of the exposure and each renewal, the test containers were emptied and refilled with freshly prepared test solutions. 

It should be noted that the test substance sorbs strongly to the algae (van Wijk, 2009) which may give the impression that the substance is lost from the test system when focusing only the dissolved concentration (when algae are separated prior to analysis).

The results are presented based on nominal test loadings and on time weighted average (TWA) measured concentrations. The calculated ErL10 and ErL50 values for inhibition of specific growth rate were 39.0 and 63.8 μg/L, respectively. While the ErC10 and ErC50 values with 95 % confidence intervals for inhibition of specific growth rate were 0.179 and 2.66 μg/L, respectively The TWA results are given despite the fact that per definition of the WAF, 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 will be 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 Triamine T were analytically verified via LC-MS/MS at the start (0 hours), after 24 and 48 hours and at the end of the exposure (72 hours) in all WAFs and in the control. The environmental conditions were within the acceptable limits. The validity criteria of the test guideline were met.

A fingerprint was performed with the highest loading rate (100.0 µg/L) and compared with the analytical standard with the same concentration of the test item prepared in methanol. Both were verified via MS and evaluated by the software. The solutions were analytical verified via high resolution MS and evaluated by the software. The detected signals of the analytical standards and the sample solution were compared. Signals related to the test item were observed in the analytical standard but not in the highest test item concentration indicating a low solubility of the test item in the aqueous test medium.

 

• 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

 

Key value for chemical safety assessment

EC50 for freshwater algae:

63.8 µg/L

EC10 or NOEC for freshwater algae:

39 µg/L