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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity of C8-18 AAPB and Coco AAPB to fresh water and salt water algae was investigated in several reliable studies conducted according to guideline, including two studies with natural river water. In addition one toxicity study to fresh water algae conducted with C12 AAPB is available. The EC50 and NOEC values were calculated based on a weight of evidence approach.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.4 mg/L
EC50 for marine water algae:
2.4 mg/L
EC10 or NOEC for freshwater algae:
0.6 mg/L
EC10 or NOEC for marine water algae:
0.6 mg/L

Additional information

The toxicity of C8-18 AAPB and Coco AAPB to fresh water algae was investigated in several reliable studies conducted according to guideline. There is more than one set of data on algae with the same endpoint, duration, life stage and testing condition with the same reliability rating and there is no specific reason that could explain the difference in results. According to “R.10.2.2 Evaluation and interpretation of data” these data are harmonised by a geometric mean. This weight of evidence approach was followed though the test results are slightly more than a factor of 10 apart.

As Desmodesmus subspicatus as well as Skeletonema costatum belong to the Eucaryota and according to TGD the sensitivity of fresh water and marine organisms are in general comparable, the EC50and NOEC values were calculated based on aweight of evidence approach. For fresh water algae, data from two reliable studies with the lowest EC50and NOEC values were included in the weight of evidence approach. In addition it seems to be justified to include the values obtained from the study conducted with C12 AAPB, as it is the main component of Coco AAPB and differs only in chain length distribution. Therefore a common mode of action can be assumed. For marine water data from one study are available. The obtained results were considered to be valid for the AAPBs.

Data included in the weight of evidence approach

 

Fresh water algae

In a test conducted according to DIN 38412, part 9 (comparable to OECD Guideline 201), the cultures of Desmodesmus subspicatus were exposed to Coco AAPB under static conditions for 72 h. Originally, the data were evaluated according to the test guideline DIN 38412, Part 9 using the EDV-program of Mr. Holtmann (Henkel KGaA). Based on current knowledge, this calculation model is no longer valid or only valid with restriction. Therefore, a recalculation of the data was performed taking into account the OECD principles. The 72 h ErC50, EbC50, and NOEC were found to be 1.5, 0.57, and 0.3 mg a. i./L nominal, respectively.

In the second 72 hour toxicity study conducted according to OECD Guideline 201 (Alga, Growth Inhibition Test) and EU Method C.3 (Algal Inhibition test), the cultures of Desmodesmus subspicatus were exposed to Coco AAPB (aqueous solution, 30.9 % active matter) at nominal concentrations of 0.97, 1.93, 3.86, 7.72, 15.45, 30.9 mg active substance/L under static conditions. The 72 h NOEC, LOEC and EC50values based on growth rate were 3.86, 7.73 and 9.86 mg a. i./L nominal, respectively. The 72 h NOEC, LOEC and EC50values based on biomass were 1.93, 3.86 and 5.31 mg a. i./L nominal, respectively.

C12 AAPB was investigated in a 72 hour acute toxicity study. The cultures of Desmodesmus subspicatus were exposed under static conditions in accordance with the OECD Guideline 201. The 72 h ErC50value based on inhibition of specific growth rate was 3.15 mg a. i./L, the 72 h EyC50value based on yield inhibition was 1.01 mg a. i./L, respectively. The 72 h NOEC based on growth rate and yield was determined to be 0.3 mg a. i./L nominal. No abnormalities were noted. The test item effects were observed to be reversible at the test concentrations 0.32 - 32 mg test mat. /L. (0.096 - 9.6 mg a. i./L).

 

Marine algae

The toxicity of Coco AAPB to the marine phytoplankton Skeletonema costatum was investigated in a study conducted according to ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum). Cultures of Skeletonema costatum in the exponential growth phase were exposed to Coco AAPB under static conditions for 72 h. The 72 h ErC50and NOEC values were determined to be 0.74 mg a. i./L and 0.36 mg a. i./L (nominal each), respectively.

Supporting data

The results were supported by further fresh water guideline studies (OECD 201, EU Method C.3, ISO 8692). ForScenedesmus subspicatus (Desmodesmus subspicatus), the 72 h ErC50, EbC50and NOEC values were determined to be in the range between 5.6 and 14.7 (growth rate), 4.66 and 9.2 (biomass), and 1.8 –3.55 mg a. i./L nominal (NOEC growth rate and biomass), respectively.

For Pseudokirchneriella subcapitata (Selenastrum capricornutum) the 96 h ErC50, EbC50and NOEC values were determined in a study on Coco AAPB to be >10 (growth rate) and ca. 8 (biomass) and 3.2 mg a. i./L nominal (NOEC growth rate and biomass), respectively. Compound related phytotoxic effects were not detected.

AAPBs were subject to the ICCA OECD program. In additional studies the toxicity to aquatic algae was investigated, comparing two different products, reconstituted water and natural river water. The following conclusion is cited from SIAR CAPB (2006).

“The effect values using natural river water are only slightly higher than using reconstituted

water. The influence of ingredients in natural aquatic systems on the algae toxicity can be neglected. It could also be shown, that the use of different products did not have an influence on the algae toxicity of cocamidopropyl betaine.”

Conclusion:

As justified above this endpoint was evaluated using a weight of evidence approach. The geometric mean calculation results in a 72 h ErC50of 2.4 mg a. i./L and a NOEC of 0.6 mg a. i./L taking into account 72 h ErC50values of 1.5, 9.86, 3.15, and 0.74 mg a. i./L, NOEC values of 0.3, 3.86, 0.3, and 0.36 mg a. i./L respectively.