Tetrasodium 4-amino-5-hydroxy-3,6-bis[[4-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]naphthalene-2,7-disulphonate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

2020

Reliability:

2 (reliable with restrictions)

Justification for type of information:

1. Hypothesis for the analogue/category approach
See paragraph 1 of the 6.1.5 - EC 241-164-5 - Reactive Black 5 – Reasoning.pdf file.
Source and target chemical(s) (Including information on purity and impurities)
See paragraph 2 of the 6.1.5 - EC 241-164-5 - Reactive Black 5 – Reasoning.pdf file.
Analogue approach justification
See paragraph 3 of the 6.1.5 - EC 241-164-5 - Reactive Black 5 – Reasoning.pdf file.
4. DATA MATRIX
For the details on data matrix see the paragraph 4 of the file 6.1.5 - EC 241-164-5 - Reactive Black 5 – Reasoning.pdf

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 28 mg/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

The three neighbour compounds show a high similarity to the target considering the chemical structure, the physico-chemical properties and the molecular groups expected to have an effect towards algae. All the chemical groups contained in the target compound are also contained in the source substances. There are not functional groups that are present in the target compound but not in the sources. Considering the fragments matching, some dissimilarities may explain the absence of toxicity for source No 2 and confirms the highest similarity of the source No 3 with the target.
The experimental acute toxicity towards algae for the sources are discordant. The sources No 1 and No 3 show an ErC50 72 hr for algae between 10 and 100 mg/L, whereas for the source No 2 an ErC50>100 mg/L is reported.
All the studies were conducted considering the shading effect that may affect the algal growth. Anyway, for sources No 1 and No 2 no details are reported about the percentage difference between direct test (part A) and indirect test (part B) on algae. The study on source No 1 indicates a degradation of the substance that cause the loss of the 86% of the nominal concentration.
For the source No 3, the presence of more detailed information about the results for the modified test performed on the dye provides a higher reliability to this study.
The studies on the target substance retrieved from NITE Database reports only qualitative data. Therefore, they were discarded.
From the above considerations and based on the scenario number 2 of the RAAF document (2017), an acute toxic effect on algal growth inhibition ranging from 10-100 mg/L can be supposed for the target substance (EC 241-164-5); the value of 28 mg/L has been adopted, as average of the experimental values available for the source substance No 3 (EC 404-320-5).

Executive summary:

According to the scenario number 2 of the RAAF document (2017), the target substance (EC 241-164-5) could exert an acute toxic effect on algal growth inhibition rate of 28 mg/L. This value is obtained as an average value from the experimental ErC50 data of source substance No 3 (EC 404-320-5).

Key value for chemical safety assessment

EC50 for freshwater algae:

28 mg/L