Amines, C16-18-alkyldimethyl

Endpoint summary

Description of key information

See section "Additional information" below.

Additional information

Cationic surfactants like Dimethyl Alkyl Amines (DMA) at environmentally relevant pH exhibit strong sorption to organic and inorganic materials such as test organisms and walls of test vessels due to a combination of ionic and hydrophobic interaction. The sorption processes are mostly non-linear, such that the sorption coefficient was found to be concentration dependent. Due to these properties, the test items are difficult to test in synthetic water and results from such tests depend on the test settings applied. In river water, which contains particulate as well as dissolved organic carbon, DMAs are either dissolved in water or adsorbed to dissolved and particulate matter. This reduces the difficulties encountered in tests with synthetic water caused by the high adsorption potential and low solubility in water. In general, the adsorbed fraction of DMA is difficult to extract from the test system, which normally leads to low analytical recoveries especially in the old media, while initially measured concentrations (fresh media) are generally within +/- 20% as recommended by the guidelines. Due to the short exposure periods applied in these tests (semi-static design) those low recoveries cannot be explained by biodegradation. No, or negligible sorption to glassware occurs under these conditions, which was confirmed by measurements. This ensures reliable as well as reproducible results and means that the test substance is present in the test system and therefore available for exposure (dissolved in water and adsorbed, also called bulk). This so-called Bulk Approach is described by ECETOC (2003). Consequently, nominal concentrations were used for these tests instead of measured ones.

Finally, the most recently performed study on acute Daphnia toxicity with C16-18-DMA reliably demonstrates that artificial water (Elendt M4) alone is inappropriate for the difficult substance properties (surface-active; adsorbing; low solubility especially for the long-chain DMAs) of DMA category members. The absence of any stabilizing organic constituents (DOC, suspended matter) normally present in environmental waters caused an instable system, producing erratic immobilization results. Possible reasons are the much lower water solubility found in the Elendt M4 test medium compared to the physico-chemical test result, combined with the specific properties of DMAs outlined above.
The different WAF preparation methods elaborated in this study to cope with these problems (three range finding tests carried out) produced very different measured concentrations and partly conflicting immobilization results. Due to their surface-active properties, the DMAs are prone to form micelles or possibly micellar aggregates, depending on the respective experimental procedure applied. Glass test-vessels were pre-saturated in the definitive test with the possible side effect that additional test material was introduced into the system (e.g., some surfactants are prone to form multiple layers on surfaces). In the definitive test, actually no WAFs or saturated solutions were prepared, but a stock dispersion at a nominal concentration of 10 mg/L, far above even the solubility in pure water (4 mg/L). This stock dispersion was diluted to the test concentrations applied. This procedure seems to have caused major inhomogeneities with local concentration peaks, as indicate measured concentrations of up to 279% of nominal (analytically confirmed). Inhomogeneous and locally high concentrations have probably caused immobilization of Daphnia at low loading rates. In conclusion, this study reliably demonstrates the inappropriateness of aquatic test systems using artificial water for members of the DMA category. The study is therefore disregarded due to major methodological deficiencies. While reliable, it is not relevant for environmental hazard and risk assessment.

In order to avoid the problems outlined above, well characterized river water was used as aquatic medium to allow for reliable test results. Those results from river water tests generally correspond to bulk-(no) effect concentrations, i.e. including both, a freely dissolved fraction of the test item being in (stabilizing) equilibrium with a fraction adsorbed to dissolved or particulate organic carbon (DOC / suspended matter). Accordingly, sometimes river water tests are criticized for underestimating the true toxicity of the test item. However, based on the relatively low concentrations of dissolved or particulate organic carbon present in river water usually used for these kinds of tests, only compounds with extremely high adsorption coefficients will be bound to any significant degree.
To demonstrate this for all the acute and chronic ecotoxictiy test results obtained from river water studies, the freely dissolved fraction of the (bulk) E(L)Cx / NOEC was estimated using the adsorption coefficient for suspended matter valid for all DMA category members (see IUCLID section 5.4.1; 500 L/kg), the suspended matter (Susp. water) and organic carbon (non-purgable organic carbon, np-OC) concentrations reported for the river water used as well as EUSES methodology (RIVM, 2004). Further details and the associated calculations as well as associated literature references are given in the spreadsheet attached to this endpoint summary.
The table below summarizes the results from available river water tests ("bulk" (no)effect concentrations) with DMAs, the corresponding data for suspended matter (susp. water) and dissolved organic carbon (np-OC) concentrations per test type, as well as the calculation results for "dissolved" (no)effect concentrations.

 

Results from available river water tests with DMAs - (no) effect concentrations given as "bulk" and freely dissolved:

	C10-DMA, bulk [µM]	C10-DMA, diss. [µM]	C12-14-DMA, bulk [µM]	C12-14-DMA, diss. [µM]	C16-DMA, bulk [µM]	C16-DMA, diss. [µM]	C16-18-DMA, bulk [µM]	C16-18-DMA, diss. [µM]	C18-DMA, bulk [µM]	C18-DMA, diss. [µM]
Acute Fish Toxicity, Susp. water / np-OC [mg/L]	15.6	3.34	15.6	3.34	15.6	3.34	14	3.21	--	--
Acute Fish Toxicity, OECD 203, LC50 (96 h)	6.09	5.95	2.81	2.75	0.950	0.927	2.85	2.78	--	--
Acute Daphnia Toxicity, Susp. water / np-OC [mg/L]	15.6	3.34	15.6	3.34	15.6	3.34	14.0	3.21	--	--
Acute Daphnia Toxicity, OECD 202, EC50 (48 h)	4.99	4.88	0.253	0.247	0.247	0.241	0.653	0.638	--	--
Algae Growth inhibition ErC50, Susp. water / np-OC [mg/L]	15.6	3.34	1.0	14.0	15.6	3.34	14.0	3.21	15.6	3.34
Algae Growth inhibition, OECD 201, ErC50 (72 h)	0.145	0.141	0.254	0.237	0.0367	0.0359	0.0698	0.0682	0.0474	0.0462
Algae Growth inhibition ErC10/NOEC, Susp. water / np-OC [mg/L]	15.6	3.34	1.0	14.0	14.0	3.21	14.0	3.21	15.6	3.34
Algae Growth inhibition, OECD 201, ErC10/NOEC (72 h)	0.0223	0.0217	0.0907	0.0848	0.00947*	0.00925	0.0296	0.0289	0.0200	0.0195
Long-term toxicity to Daphnia, Susp. water/ np-OC [mg/L]	--	--	19.0	6.6	--	--	14.0	3.21	--	--
Long-term toxicity to Daphnia, OECD 211, NOEC reprod. (21 d)	--	--	0.163	0.157	--	--	0.347	0.339	--	--

*) see discussion in IUCLID Chapter 6.0 (PNEC & Conclusion on C&L) and 6.1.5 (Toxicity to algae)

 

Accordingly, depending on the suspended matter concentration and the non-purgable organic carbon concentration on the river water, the fraction of the bulk effect concentration adsorbed to suspended matter and dissolved organic carbon amounts between 2.25 % and 2.39 % for acute fish and acute Daphnia toxicity test results, 2.25 % and 6.59 % for algae toxicity tests and 2.25 % and 4.08 % for Daphnia long-term toxicity results. The resulting difference between bulk and dissolved (no) effect concentrations is within the experimental variability of these tests and is accounted for in the exposure and risk assessment, because (according to the ECETOC (2003) "bulk approach") bulk concentrations in water are used to calculate RCR values.

Results on long-term fish toxicity are not yet available. In Annex IX of Regulation (EC) No 1907/2006, it is laid down that long-term toxicity testing of aquatic organisms shall be proposed by the registrant if the chemical safety assessment indicates the need to investigate further the effects on fish. According to Annex I of this regulation, the chemical safety assessment triggers further action when the substance or the preparation meets the criteria for classification as dangerous or is assessed to be a PBT or vPvB. The hazard assessment for DMA category members reveals that they are neither PBT nor vPvB substances. While being classified as dangerous to the environment, available acute studies with fish compared to Daphnia and algae toxicity give evidence that fish are clearly less sensitive than aquatic invertebrates, with algae being definitely most sensitive. Long term studies on Daphnia magna with C12-14-DMA and C16-18-DMA (see 6.1.4) are available (see table above) such that based on that database a reliable CSA was possible.
Moreover, two further Daphnia reproduction tests as well as two long-term fish toxicity tests (OECD 210) for C12-14-DMA and C16-DMA are currently being performed and will be submitted later based on ECHA decision numbers CCH-D-2114585927-27-01/F and CCH-D-2114585918-26-01/F, respectively. This information is assumed to confirm the existing environmental assessment for the category.