Iotroxic acid

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

Justification for type of information:

In an aqueous environment, the iotroxic acid separates from the disodium salt immediately. Therefore, tests conducted with disodium salt in aqueous medium are representative for the toxicity of iotroxic azide.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): No changes in morphological structures or other abnormalities were observed except some oversized cells in the

Reported statistics and error estimates:

The values for the average area below the growth curves, specific growth rate, and the percentage inhibition were calculated by the computer program Abimed "AlgenTest XT 2.21 ".
The EbC50/72 hours (biomass) and the ErC50/72 hours (growth rate) as well as the 95% confidence limits are also calculated by the above referenced computer program on the basis of a probit analysis.

Table 1: Inhibition of biomass and the growth rate (%) of Desmodesmus subspicatus after 72 hours exposure to iotroxic acid, disodium salt

Nominal concentration of iotroxic acid, disodium salt (mg/L)	Inhibition in percent
	Biomass (integral)	Growth rate
0.0 (control)	0	0
3.1	-4.6	10.4
6.3	-11.0	6.3
12.5	-8.5	-9.4
25.0	-5.6	-10.7
50.0	-6.4	-1.1
100.0	-4.0	-7.2

At all concentrations no inhibition of growth (biomass and growth rate) was observed.

Validity criteria fulfilled:

yes

Conclusions:

Iotroxic acid, disodium salt had no inhibitory effect on the growth of Desmodesmus subspicatus.
The EbC50 (biomass) and the ErC50 (growth rate) was > 100 mg/L. Consequently, iotroxic acid, disodium salt was considered to be not toxic to the green algae Desmodesmus subspicatus..

Executive summary:

In a 72 hour algal growth inhibition test, cultures of Desmodesmus subspicatus were exposed to iotroxic acid, disodium salt (purity: 99.5%) at nominal concentrations of 0.0 (control), 3.1, 6.3, 12.5, 25.0, 50.0 and 100.0 mg/L under static conditions in accordance with the OECD Guideline 201 (23 March 2006), EC guideline Part 2 - Testing methods, Part C.3 and under GLP.

The % growth inhibition in the treated algal culture as compared to the control ranged from 10.4 % at a concentration of 3.1 mg/L to -7.2 % at a concentration of 100.0 mg/L. At all concentrations no inhibition of growth (biomass and growth rate) was observed.

There were no compound related phytotoxic effects.  

This toxicity study is classified as acceptable and satisfies the guideline requirements for an algae growth inhibition toxicity study.  

 

Results Synopsis

Test Organism: Desmodesmus subspicatus

Test Type: Static

72 hr EC₅₀: > 100 mg/L (nominal)

Endpoint(s) Effected:  Growth rate, Yield, Cell abberrations

This information is used in a read-across approach in the assessment of the target substance.

For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Description of key information

In a 72 hour algal growth inhibition test, cultures of Desmodesmus subspicatus were exposed to iotroxic acid, disodium salt at nominal concentrations of 0.0 (control), 3.1, 6.3, 12.5, 25.0, 50.0 and 100.0 mg/L under static conditions in accordance with the OECD Guideline 201 (23 March 2006), EC guideline Part 2 - Testing methods, Part C.3 and under GLP.

At all concentrations no inhibition of growth (biomass and growth rate) was observed.

The ErC50 (growth rate) was > 100 mg/L. Nominal concentrations were verified analytically. Consequently, iotroxic acid, disodium salt was considered to be not toxic to the green algae D. subspicatus, since the EC50 was higher than 100 mg/L.

Additional information

This information is used in a read-across approach in the assessment of the target substance.

Data describing the acute aquatic toxicity of iotroxic acid is based on read-across from iotroxic acid, disodium salt. In aqueous solution disodium salt disassociates to iotroxic acid.