Trisodium bis[(3'-nitro-5'-sulfonato-(6-amino-2-[4-(2-hydroxy-1-naphtylazo)phenylsulfonylamino]pyrimidin-5-azo)benzene-2',4-diolato)]chromate(III)

Endpoint summary

Description of key information

Short-term toxicity to fish

LC50 (96h, Oncorhynchus mykiss) >77.3 mg/l (geam. mean corresponding to nominal conc. of 100 mg/l)

Short-term toxicity to aquatic invertebrates

LC50 (48h, Daphnia magna) > 100 mg/l (nominal)

Toxicity to aquatic algae and cyanobacteria

EC50 (72h, Scenedesmus subspicatus) >100 mg/l (nominal)

Toxicity to microorganisms

EC10 (30 min, microorganisms) > 100 mg/l (nominal)

Additional information

Short-term toxicity to fish

The acute toxicity of the test substance to Rainbow Trout (Oncorhynchus mykiss) was determined in a 96-hour semi-static test according to the OECD 203 giudeline. The nominal concentrations tested were 4.6, 10, 21, 46 and 100 mg test substance/l and a control. Fish were placed in clean aquaria with freshly prepared test media after each 48 hours.

No fish died in the control or in the test media up to the highest test concentration of 77.3 mg/l (measured, geom. mean) during the test period of 96 hours. At the measured test concentration of 5 mg/l (geom. mean) no symptoms of intoxication were observed.

The samples taken from the vessels with the nominal concentration of 21 and 100 mg/l showed a decrese of test item content (i.e. 18.7 and 77.3 mg/l, respectively), after the renewal of 48 hours. The vessels tested with nominal concentrations of 21, 46 and 100 mg/l showed sedimentation of a part of the suspended test substance.

Invertebrate acute toxicity

A limit test was performed according to OECD guideline 202 (1984). The experiment was performed to demonstrate that the test substance has no toxic effect on the test animals up to the concentration of nominal 100 mg test substance/l, thus, the only concentration tested was nominal 100 mg test substance/l and a control. The mean recoveries found varied in the range from 83.1 to 100.7 % of the nominal values and averaged to 91.9 ± 12.4 % SD (n = 2). Loss of test item could be observed for aged samples of 48 hours. Hence no further significant detector signal at 500 nm could be observed besides the main compound, the loss of test article may be occurred by sedimentation.However, since all measured valúes were higher than 80 % of the nominal valué, and the mean value of the measured concentrations at the start and the end of the test amounted to 91.9 % of the nominal value, all reported biological results are related to the nominal concentration of the test substance.

Toxicity to aquatic algae and cyanobacteria

The influence of the test substance on the growth of the green alga Scenedesmus subspicatus Chodat was investigated in a 72-hours static test according to the OECD Guideline N. 201. However, the test method was modified to differentiate between a reduced growth of algae due to real toxic effects of the test substance on the algal cells or due to an indirect effect, a reduced algal growth by light absorption in coloured test media.

The study consisted in two different parts, in order to quantify the algicidal effect of the test substance, but also the growth inhibition effect due to reduced light intensities in the coloured test media.

In addition, it is important to underline a significant variability of the substance concentration in test vessels, as determined during the analytical monitoring. The mean recoveries found for the test concentrations analysed varied in the range of 85.0 % to 92.6 % of the respective nominal values for samples at 0 hours, and were found in the range of 57.8 % to 80.4 % for aged samples of 72 hours.

In conclusion, the modified algal test has clearly demonstrated that the observed growth inhibition effect of the test substance was caused in a high degree due to the indirect effect, the light absorption In the coloured test media. The real toxic effect of the test substance amounted to in maximum about 21 % growth inhibition up to the highest test concentration of nominal 100 mg/l (mean measured test substance concentration: 86.5 mg/l).

Toxicity to microorganisms

The inhibitory effect of the substance on aerobic waste water bacteria of activated sludge was investigated in a respiration test, according to the OECD Guideline 209 (1984). The study examined nominal test concentrations in the range from 3.2 mg/l to 100 mg/l.

The test substance showed practically no inhibition of the respiration rate at test article concentrations ranging from 3.2 mg/l to 100 mg/I. The EC50 was therefore determined to be >100 mg/l.