Leucophor 1111X

Toxicity to aquatic algae and cyanobacteria

Description of key information

ECb50 (72 h): 93 mg/l 
ECr50 (72h) > 100 mg/l 
NOEC (72h): 22 mg/l (both biomass and growth rate) 

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

22 mg/L

Additional information

There are no experimental data available on the Leucophor 1111X, thus a read across approach with the structural analogous substance 01 and the structural analogous 02 has been proposed.

The toxicity of analogous substance 02 to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the OECD 201. The study was conducted under static conditions and five concentrations were tested: 2.00, 6.32, 2.0, 63.2, 200 mg/l. All concentration levels and the control were analytically verified via HPLC-DAD: the test item in the fresh media (0 hrs) were in the range of 102 to 113 % of the nominal values at all tested concentration levels; the measured concentrations in the old media (72 hrs) were in the range of 29 to 33 % of the nominal values of all concentrations. Microscopic evaluation of the cells at the start and end of exposure revealed no morphological abnormalities. The No Observed Effect Level was stated at 11.3 mg/l for inhibition of both growth rate and yield after 72 hours and the ErC50 (72h) was stated as greater than 111 mg/l (meas. geom. mean) (Scheerbaum, 2015).

It has to be taken into account that Stilbene-type Fluorescent Whitening Agents (SFWAs) undergo photoisomerization. During the test, it is expected that the analyses measured only one of the two isomers present in the tested solutions because the determination of the test item concentration was carried out by HPLC-DAD at the wavelength of 350 nm. Furthermore, considering the fact that substance is very soluble, not abiotically rapidly degraded and that in the study report no abnormalities of the test solution were observed, it is expected that the low concentration levels recorded at 72 hours are attributable to the method of analysis, rather than to the substance disappearance.

The influence of analogous substance 01 on the growth of the green algal species Scenedesmus subspicatus was investigated in a 72-hour static test according to the OECD Guideline No. 201, 1984. The nominal test concentrations were 4.6, 10, 22, 46, 100 mg/l in parallel with a control. In the analyzed test media the measured test item concentrations ranged from 97 to 1.04 % of the nominal values at test start. In the test media samples from the end of the test 194 to 206 % of the nominal values were found. The pretended increase of the test item concentrations most probably was due to photo-isomerisation of the test item. It is known for this substance, that the cis/trans isomers have different adsorption coefficients, leading to the increasing results for the test item at the end of the test. A quantification of the unchanged educt only in the aged samples is not possible. However, the correct dosage was shown by the not light exposed samples from the start of the test. Thus, the reported biological results are based on the nominal test item concentrations. The test item had a statistically significant inhibitory effect on the mean growth rate of Scenedesmus subspicafus after the test period of 72 hours at concentrations of 46 mg/l and above. The mean biomass was statistically significantly reduced first at the next higher test concentration of 100 mg/l. However the biomass was clearly lower than in the control. Thus, the test concentration of 46 mg/l was determined as the 72-hour LOEC. The 72-hour NOEC was determined to be 22 mg/l, since up to and including this test concentration both, the mean biomass and the mean growth rate of the algae were statistically not significantly lower than in the control (Seyfried, 2006).

All the substances used in a read across approach are Stilbene derivatives Fluorescent Whitening Agents salts. They display similar structural and physicochemical properties: all of them exhibit high degree of dissociation in water and very low octanol/water partition coefficients because to a higher affinity with water phase than the octanol one. They are all very soluble in water, due to the presence of sulphonated groups in the molecules; all of them are non readily biodegradable and are expected to undergo to the same environmental fate.

In both cases the read across approach can be considered as reliable and representative; the differences occurring in the structure formulas (i.e. substituents) are expected to not significantly impact the toxicity to aquatic algae.

Further details about the justification for read across approach are given in the report attached to the Section 13 of this dossier.