Fatty acids, tall-oil, compds. with N-[3-(dimethylamino)propyl]tall-oil amides

Toxicity to aquatic algae and cyanobacteria

Description of key information

Toxicity to algae was determined in a new study (Spoo-Klöppel, 2020) conducted in accordance with OECD 201, GLP documentation and in contrast to the previously existing study (Weyers, 2006) with substance-specific analysis.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.031 mg/L

EC10 or NOEC for freshwater algae:

0.008 mg/L

Additional information

In its decision CCH-D-2114453667-38-01/F ECHA asked the registrants to conduct a new study on toxicity to algae as the existing study (Weyers, 2006) referred to nominal concentrations. Thus, a new algae study was conducted (Spoo-Kloeppel, 2020). Based on analytical pre-tests it turned out that the test item (mixture of fatty acids) forms micelles in algae test medium, resulting in fluctuating recoveries of the test item. Thus, there was additional effort to identify conditions under which stable and reproducible test concentrations could be maintained. It turned out that test item pre-treatment could be adapted to ensure stable and reproducible recoveries within the same experiment. However, in the final range-finder and main study which applied this pre-treatment the test item concentration differed again by a factor 10 between both tests, while the recoveries were well within each of both tests. This revealed that the study design was still not sufficiently robust to ensure stable test concentrations. It was, thus, concluded that additional efforts are needed to further develop the test conditions for this obviously difficult to handle test item. However, as the deadline set by ECHA to generate a new algae study is now ahead no further refinements could be done and a study report was generated based on the recent main study.

In this main study, the validity criteria defined in OECD 201 were all fulfilled and all parameters observed proved that the study as such is reliable. Thus, there is no issue with the main study reported as such. The only issue is that it was not possible to establish a test item pre-treatment, which ensures reproducible recoveries of the test item.

Despite this short-coming the study was considered to be adequate to be considered for PNEC derivation, PBT assessment, and CLP classification. This is in particular true as the recovery in the main study was a factor 10 lower compared to the range-finger. Thus, the derived ErC50, the ErC10, and NOEC which are used these assessments report of the lower and more conservative effect levels.

Thus, while the recovery among the pre-tests, the range-finder and the main study varied the main study is still reporting of the lowest effect level. The following effect levels were determined:

72-hour NOEC values based on growth rate in the pre-tests range from 0.031 to 0.1 mg/L, that in the range-finder was 10 mg/L, and that of the main study is 0.0040 mg/L.

72-hour ErC10 values based on growth rate in the pre-tests range from 0.032 to 0.11 mg/L, that of the range-finder is 0.72 mg/L, and that of the main study is 0.0079 mg/L.

72-hour ErC50 values based on growth rate in the pre-tests ranged from 0.47 to 0.52 mg/L, that of the range-finder is 5.0 mg/L, and that of the main study is 0.031 mg/L.

All validity criteria defined in OECD 201 are met in the main study.

The registrants consider the new study on algae toxicity (Spoo-Kloeppel, 2020) as sufficiently reliable (Klimisch 2, reliable with restrictions) to be used for regulatory purposes.

The ErC10 value is usually considered more reliable from algae studies and, thus, the ErC10 value together with the ErC50 of the main study are taken forward for hazard and risk assessment as well as CLP classification.