Trisodium, bis [2-((E)-(4-hydroxy-2-oxido-3-((E)-(5-sulfonatonaphthalen-1-yl)diazenyl)phenyl)diazenyl)benzoate] chromate(3-)

Endpoint summary

Description of key information

Short-term toxicity to fish

LC50 (96 hours, Orynchus mykiss) = 509.1 mg/l (nominal)

LC50 (96 hours,Orynchus mykiss) > 100 mg/l (nominal)

Short-term toxicity to invertebrates

EC50 (48 hour, Daphnia magna) = 26 mg/l (nominal)

Long-term toxicity to invertebrates

NOEC (21 days, Daphnia magna) = 10.0 mg/l (nominal)

Toxicity to algae

NOEC (72 and 96 hours, Scenedesmus subspicatus): 20 mg/l (nominal)

Toxicity to microorganisms

IC50 (5 days) > 32 m/l (nominal)

Additional information

The following data on toxicity of the test item to fish, crustacea, alae and microorganisms was obtained.

 

Short-term toxicity to fish

Two studies were conducted on short-term toxicity to rainbow trout (Oncorhynchus mykiss). The first study (according to EU Method C.1, 1984) exposed groups of 10 animals to test item concentrations of 300, 350, 450, 500, 600 and 800 mg/l in reconstituted water for 96 hours, plus a control group of 10 animals were exposed to reconstituted water alone. Measured concentrations fell within 97.7 % to 108.3 % of nominal test item concentrations. A dose-response relationship with mortality was evident. The 96-hour LC50 of the test item was calculated to be 509.1 mg/l (nominal concentrations) using the LOGIT Model at 95 % confidence limits based on mortality.

The second study (according to the OECD Guideline 203, 1981) was a limit test according to the OECD Guideline 203 (1981) whereby 10 rainbow trout were exposed to 100 mg/l test item for 96 hours in a limit test, and a negative control group of 10 rainbow trout were exposed to test medium alone. Measured test item concentrations fell between 101.0 and 103.5 % of nominal concentrations. As no mortality was observed, the 96-hour LC₅₀ is therefore higher than 100 mg/l (nominal concentration).

Short-term toxicity to invertebrates

In accordance with the OCED Guideline 202 (1984), groups of 20 Daphnia magna were exposed to test item concentrations of 3.2, 5.6, 10, 18, 32, 56, 100, 180 and 320 mg/l in a static test for 48 hours. The 48-hour EC₅₀ was calculated using the PROBIT Analysis with 95 % confidence limits based on immobilisation of daphnia. At 48 hours, no immobilisation was observed in test item concentrations of 10 mg/l and below, and 100 % immobilisation occurred in concentrations of 56 mg/l and above. Measured concentrations ranged from 86 to 100 % (beginning of test), and 94 to 100 % (end of test) of nominal concentrations. Based on these findings, the 48-hour EC₅₀ was found to be 26 mg/l (nominal concentrations).

Long-term toxicity to invertebrates

A 21-day, semi-static daphnia reproduction toxicity study examined the long-term toxicity of the test item to invertebrates, according to Section 2 of the OECD Guideline 202 (1984). Groups of 10 Daphnia magna were exposed to 1.0, 3.2, 10.0, 32.0 or 100 mg/l test item for 21 days in semi-static conditions and were monitored for rate of reproduction and rate of survival for 21 days alongside a negative control group. The stock solution contained 81.3 and 88.7 % of the nominal concentration at the end of the test. A dose-response relationship was observed with mortality from 0 % at concentrations of 32.0 mg/l and below to 100 % in 100 mg/l on day 12. A dose-response relationship was also observed with reduced reproduction rate. Based on these observations, the NOEC of the test item for Daphnia magna was found to be 10.0 mg/l (nominal concentrations).

Toxicity to Algae

The toxicity of the test item to aquatic algae was evaluated in a 96-hour experimental study on Scenedesmus subspicatus according to the OECD Guideline 201 (1984). Cell cultivations of S. subspicatus were exposed to the test item (0.3125, 1.25, 5.0, 20 or 80 mg/l) and cells were counted after 24, 48, 72 and 96 hours. Change in cell count over time was represented graphically to form dose-response curves for each concentration, and toxicity was analysed by comparison of the area under respective growth curves of treated and untreated samples. A positive control (potassium dichromate) was also tested in parallel. Measured concentrations ranged from 72.4 to 113.1 % of nominal concentrations. The 96-hour NOEC was found to be 20 mg/l, and the 96-hour LOEC was found to be 80 mg/l. The E_bC₅₀ was found to be 24.2 mg/l for 96 hours (nominal concentrations), using the LOGIT-Model. Only EbC50 (72 h and 96 h) were reported in the study report. Based on the available data on number of cell at the different time points, a range of the percentage of inhibition considering the growth rate is calculated. The ErC50 (96 h) is expected to be between 20 -80 mg/L (% inhibition at 20 mg/L and 80 mg/L is ca. 5 % and 70 % respectively). It is worth noting that the evaluation of the toxicity potential of the substance to algae presents some limits due to the nature of the substance (dye). Specifically, it cannot be distinguished whether the effects are due to the colour of the test item (and hence the coloured test medium) or they are due to an intrinsic algicidic potential.

Toxicity to microorganisms

The toxicity of the test item to microorganisms was evaluated in an experimental study on 1 g/l aqueous solution of the test item which measured the 5-day Biochemical Oxygen Demand (BOD5) and the bacterial inhibition by the glucose/glutamic acid modification of the BOD5 method. BOD5 and bacterial inhibition were measured at concentrations of 1, 3.2, 10 and 32 mg/l test item without a nitrification inhibitor. A reference substance, glucose/glutamic acid, was tested at approximately a 1:47 dilution of the standard strength solution (150 mg/l of each compound) without nitrification inhibitor. BOD5 of the test item was found to be < 0.03 g O₂/g. At the highest concentration tested, the dissolved oxygen difference (blank - test) was less than 1 mgO₂/l, therefore, oxygen uptake was below the realistic detection limit and was calculated to be < 1/32 = < 0.03. The reference substance, glucose/glutamic acid, was found to have a BOD5 of 185 mg O₂/l. Bacterial inhibition (IC₅₀) was found to be higher than 32 mg/l.