Reaction mass of disodium [2,2'-(imino-kappaN)dibutanedioato-kappa2O1,O4(4-)]manganese(2-) and sodium sulphate

Endpoint summary

Additional information

General considerations

Ecotoxicological investigations concerning fish, aquatic invertebrates and algae were performed with the target substance Mn(II)-IDHA. However, experimental data referring to the toxicity to microorganisms are only available for the read-across substance Mn(II)-EDTA. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement by Chemservice S.A. (2014).

Toxicity to fish

The acute toxicity of MnIDHA towards Rainbow trout was investigated according to OECD Guideline 203 in compliance with GLP (Konfederak, 2013). In this static test, Oncorhynchus mykiss was exposed to the test item at the limit test concentration of 100.0 mg/L and a control (0.0 mg/L). The exposure took place in glass aquaria with a capacity of 10 L. There was one replicate of the test concentration and the control. Ten fish were introduced into each aquarium. The fish were observed for mortality and intoxication symptoms after 3, 6, 24, 48, 72, and 96 hours of the exposure. All fish in the control and in the test concentration survived the 96-hour exposure. They did not exhibit any intoxication symptoms. Chemical analyses were performed using a validated method. Samples collected at the exposure initiation (t0) and at the exposure termination (t96) were analyzed. The average concentration of MnIDHA in samples collected at the exposure initiation (t0) was 96.8% of the nominal concentration. The average concentration of MnIDHA in samples collected at the exposure termination (t96) was 84.1% of the initial concentration. Since the concentration of MnIDHA in the solution was higher than 80% of the initial concentration after 96 hours, the LCx values were calculated on the basis of the nominal concentration. The LC50 values after 24, 48, 72, and 96 hours of the exposure determined on the basis of the nominal concentration of the test item are higher than 100.0 mg/L. The NOEC (96h) value is reported as ≥ 100 mg/L based on the nominal concentration.

Toxicity to aquatic invertebrates

The acute toxicity of Mn(II)IDHA towards Daphnia magna was determined by OECD Guideline 202 in compliance with GLP (Konfederak, 2013). In this static test, the test organisms were exposed to the test item for 48 hours. The limit concentration and the control were split into eight replicates. There were five daphnids in each replicate. The daphnids were observed for immobilization after 24 and 48 hours of the exposure. Test organisms were considered immobile if they showed no ability to swim within 15 seconds after swirling the test vessel. The daphnids in the limit concentration of the test item (100.0 mg/L) and the control did not exhibit immobilization. Chemical analyses were performed using a validated method. Samples collected at the exposure initiation (t0) and at the exposure termination (t48) were analyzed. The average concentration of MnIDHA in samples collected at the exposure initiation (t0) was 88.7 % of the nominal concentration. The average concentration of MnIDHA in samples collected at the exposure termination (t48) was 91.6 % of the initial concentration. Since the concentration of MnIDHA was higher than 80% of the initial concentration at the exposure termination, the ECx values were determined on the basis of the nominal concentration of the test item. Immobilization was not observed in the limit test. In conclusion, the EC50 (48h) value is reported as > 100 mg/L. Due to the absence of immobilization at the limit concentration tested, the NOEC (48h) value can be indicated as ≥ 100 mg/L based on the nominal concentration.

Toxicity to aquatic algae

The impact of MnIDHA on the green algal growth was investigated during a 72-hour static toxicity study according to OECD Guideline 201 in compliance with GLP (Konfederak, 2013). The study was conducted in glass flasks with a capacity of 250 mL. Each replicate contained 100 mL. The initial density of the algae was 1 x 10 E4 cells/mL. The concentrations of the test item, MnIDHA of 10; 32; 100; 320 and 1000 mg/L and a control (0.0 mg/L) were used. Chemical analyses were performed using a validated method. Samples collected at the exposure initiation (t0) and at the exposure termination (t72) were analyzed. The average concentration of MnIDHA in samples collected at the exposure initiation (t0) was between 95.2 – 100.3% of the nominal concentration. The average concentration of MnIDHA in samples collected at the exposure termination (t72) was between 92.2 – 100.4% of the initial concentration. After 72 hours of the exposure, the algal cells were observed for changes in morphology. The cells in all test item concentrations did not differ from the control ones. Since the concentration of MnIDHA was in the range of 80 - 120% of the initial concentration at the exposure termination, the ECx values were determined on the basis of the nominal concentrations of the test item.

The concentration causing 50% inhibition of the growth rate of Pseudokirchneriella subcapitata, i.e. the ErC50 (72h) value is 597.57 mg/L. The ErC20 (72h) value is 140.86 mg/L, whereas the ErC10 (72h) value is 66.18 mg/L. For the growth rate, the LOEC (72h) is lower than or equal to 10 mg/L, whereas the NOEC (72h) is lower than 10 mg/L.

The mean concentration causing 50% inhibition of yield of Pseudokirchneriella subcapitata, i.e. the EyC50 (72h) value is 108.95 mg/L. The EyC20 (72h) value is 42.27 mg/L, whereas the EyC10 (72h) value is 25.76 mg/L. For yield, the LOEC (72h) is lower than or equal to 10 mg/L, whereas the NOEC (72h) is lower than 10 mg/L.

Toxicity to aquatic microorganisms

Data referring to the toxicity towards microorganisms of the target substance was only indirectly assessed for the inherent biodegradation study.

However, sufficient data from a read-across substance can be used to fill this data gap. The toxicity of the read-across substance EDTA-MnNa2 to activated sludge was investigated in an activated sludge respiration inhibition test, conducted according to OECD TG 209 under GLP (Geerts, 2010).In this test, no inhibition of the respiration of the activated sludge was measured at the highest concentration tested, i.e. 640 mg/L. EDTA-MnNa2 istherefore considered not harmful to activated sludge.

This conclusion is confirmed by the inherent biodegradation study of Mn(II)IDHA according to OECD Guideline 302B (Chojnacka, 2014). A solution of Mn(II)IDHA in a mineral medium was inoculated with activated sludge and incubated under aerobic conditions for 28 days. The test substance was the sole source of organic carbon. In addition to the investigations referring to the degradation of the test substance, a toxicity control (containing 100 mg DOC/L of Mn(II)IDHA and also 100 mg DOC/L of the easily biodegradable substance benzoic acid, sodium salt) was performed. Due to the fact that benzoic acid, sodium salt and Mn(II)IDHA were degraded (57.8 % degradation after 28 days, based on DOC), the substance Mn(II)IDHA had no toxic effects on the microorganisms. The corresponding result (NOEC (28 d) = 100 mg DOC/L) shows that the substance is not harmful to activated sludge.