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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Sika Hardener LG was assessed in an aquatic toxicty test to unicellular green algal (Pseudokirchneriella subcapitata) according EU-method C.3 and OECD guideline 201. A water accommodated fraction (WAF) was prepared and nominal concentrations of up to 100 mg/L tested. The 72-h EC50 based on growth rate was determined as 51.9 mg/mL. The 72-h EC50 based on yield was 38.5 mg/mL and the overall NOEC was determined to be 25.0 mg/mL of the limit of solubility.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
51.9 mg/L
EC10, LC10 or NOEC for freshwater algae:
25 mg/L

Additional information

Due to the high reactivity of the substance in water, a weight of evidence approach using data form the parent molecule, its two primary hydrolysis products and from an analogous substance were assessed:

In the study with the parent compound Sika Hardener LG, the effect of the test item on the growth of an unicellular green algal species Pseudokirchneriella subcapitata (formerly: Selenastrum capricornutum) according to EU method C.3 and OECD guideline no. 201 were determined. Exponentially growing cultures of Pseudokirchneriella subcapitata were exposed to various concentrations of the test item (6.25; 12.5; 25.0; 50.0 and 100.0 mg/L.) over several generations under defined conditions. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours and thus, over several algal generations. A supersaturated test item solution was prepared by dispersing the test item amount (nominal load of 100 mg/L) into the test medium two days before the start of the renewal periods. This solution was shaken for 24 hours at app. 30 ºC, then was left settling for 24 hours at app. 20 ºC and thereafter filtrated through a 0.45 μm filter. The shape of the algal cells growing was obviously not affected. The test item had a statistically significant inhibitory effect on the growth based on the average specific growth rate, yield and areas under the growth curves of Pseudokirchneriella subcapitata after the 72 exposure period in the concentration range tested. A test concentration of 50.0 mg/mL was determined as the 72-hour LOEC. A test concentration of 25.0 mg/mL was determined as the 72-hour NOEC. The 72- hour EC50 based on growth rate was determined as 51.9 mg/mL, a EC50 based on yield of 38.5 mg/mL.

The second study was performed in order to evaluate the toxic potential of the hydrolysis product 2,2 -Dimethyl-3 -lauroyloxy-propanal (aldehyde component) the toxic potential of test item towards Desmodesmus subspicatus CHODAT, an unicellular freshwater green alga. The incubation period of 72 hours corresponds to a subchronic test, as during this period, about five cell divisions take place. Four experiments were performed. As the test item is poorly water soluble, the “water-accommodated fraction” was tested in the first experiment. This was done by weighing the nominal load 100 mg/L, adding the corresponding amount of dilution water and shaking vigorously for 24 hours. The resulting solution was filtrated through 0.45μm filters. The treatment was used to incubate the unicellular freshwater green alga Desmodesmus subspicatus for a period of 72 hours. The cell concentration of each replicate was determined by measuring the absorption of the cuvettes at 440 nm every 24 hours with a spectral photometer. With these measured values, the number of cells was calculated (linear correlation between cell concentration and absorption given). Then the growth rate, the area under the growth curve (AUC1) and the yield2 were determined. The test solution went flocculent during the test probably caused by undissolved parts of the test item. The second experiment was performed likewise, but with stirring over 2 hours instead of shaking. The resulting solution was left to stand for about 15 minutes, then the solution was filtrated. No inhibition was observed. The test item forms a surface film, thus the preparation of the WAF is not very reproducible. Therefore for the third experiment, a stock solution in acetone was prepared. The treatment concentration of 1 mg/L was prepared by spiking the corresponding amount of deionized water with this stock solution. The treatment concentration of 1 mg/L is considered to be well above maximal water solubility of 0.227 mg/L. 25 % inhibition of growth rate, 72 % inhibition of AUC, and 73 % inhibition of yield were observed. At the beginning and after 4 hours of the test, the content of the test item and its oxidation product (carbonic acid) in each test solution was determined using GC. Based on these experiments, the fourth experiment was performed using five concentrations between 0.1 and 1 mg/L. The test solutions were prepared by spiking with a stock solution in acetone. No inhibition occurred in the two lower concentrations. The three higher concentrations inhibited the algal growth only slightly. At the beginning and 4 hours after the start of the test, the content of the test item in each test solution was determined using GC. The measured concentrations of the freshly prepared test solutions (at the start of the test) were between 27 and 30 % of the nominal concentrations. The three lower treatments were below the limit of quantification. Sample preparation and clean-up requires about one hour. During this time, the test item already undergoes hydrolysis which caused these low recoveries. After 4 hours remaining test item was only detected in the highest concentration. The measured concentration was 8 % of the nominal concentration. The test item is not stable in water (as has been demonstrated in the respective study “water solubility determination”). Due to the fast degradation referring to determined values is not meaningful and only the nominal values were used. The 72 h EC50 was determined to be > 1 mg/L and the 72 h NOEC was 0.18 mg/L. These data were already submitted in a NONS dossier under Directive 92/32/EEC (notification number 05 -04 -1922 -00 from 2005 -10 -25) and considered valid and uncritical from the German Competent Authority (BAUA).

The toxicity of the second hydrolysis product 2-(2-aminoethoxy)ethanol to Algae was evaluated according to German Industrial Standard DIN 38412 part 9. In a 72 hour toxicity study, cultures of Scenedesmus subspicatus were exposed to 2-(2-aminoethoxy)ethanol at nominal concentrations of 0 (control), 3.9, 7.8, 15.625, 31.25, 62.5, 125, 250, 500 mg/L under static conditions. The 72 h-EC50 value based on growth rate was 202 mg/L. The 72 h NOEC based on growth rate was 62.5 mg/L (see ECHA dissemination homepage).

In addition data from the analogues substance Sika Hardener LI (Dodecanoic acid , 3-[[3-[[[2,2-dimethyl-3-[(1-oxododecylo)oxy]propylidene]amino]methyl]-3,5,5-trimethylcyclohexyl]imino]-2,2-dimethylpropyl ester, CAS 932742-30-8) is reported. Sika Hardener LG and Sika Hardener LI both have the same aldehyde component (2,2 -Dimethyl-3 -lauroyloxy-propanal), but different amine components. Data from the OECD toolbox support the use of data from Sika Hardener LI also as read across fro Sika Hardener LG (see attachment in section 13). In this study, exponentially growing cultures of Pseudokirchneriella subcapitata were exposed to various concentrations of the test item over several generations under defined conditions. The algal growth in relation to a concurrent control culture was determined over a fixed test period of 72 hours and thus, over several algal generations. A supersaturated test item solution was prepared by dispersing the test item amount (nominal load of 100 mg/L) into the test medium two days before the start of the renewal periods. This solution was shaken for 24 hours at app. 30 ºC, then was left settling for 24 hours at app. 20 ºC and thereafter filtrated through a 0.45 μm filter. The following nominal concentrations were used: 6.25; 12.5; 25.0; 50.0 and 100.0 mg/L. In this 72-h algal growth inhibition test with Pseudokirchneriella subcapitata the 72-h EC50 based on growth rate was determined at 180.4 mg/L. The 72-h EC50 based on yield was 102.7 mg/L. The overall NOEC was determined to be 25.0 mg/L. All results were based on the nominal concentrations.

Conclusion:

Due to the physical-chemical properties of Sika Hardener LG (fast hydrolysis) it is not possible to perform standard ecotoxicology tests. It was decided to do the test by preparing a WAF and base the EC50 and NOEC calculations on nominal concentrations (justification see study record). A value of 51.9 mg/L was derived. The data presented for the supporting substance Sika Hardener LG with a LC50 of 180 mg/L show a lower toxicity as compared to Sika Hardener LG. Overall, taking all ecotoxicological data into account, the same classification and labelling results (R52/53, chronic environment cat.3). Results from the two hydrolysis products support the findings and lead to the same environmental classification and labelling (R52/53 or chronic cat.3, see also biodegradation other ecotoxicological results). For 2,2 -Dimethyl-3 -lauroyloxy-propanal (aldehyde component) different tests were done to assess the ecotoxicology towards algae. In the end it was also not possible to use measured data for EC50 calculations (details see above). As the substance is readily biodegradable, the LC50 of > 1 mg/L and the NOEC of 0.18 mg/L together lead to a classification as chronic env. cat.3 according to the 2. ATP of the CLP Regulation. The data with 2-(2-aminoethoxy)ethanol with an LC50 of 202 mg/L show that this hydrolysis product is no severely toxic to the environment. These data confirm that the classification and labelling and the hazard assessment of the ecotoxicology of Sika Hardener LG can be based on the main study with the product itself.