Calcium sulphidoacetate

Toxicity to microorganisms

Additional information

Experimental data on toxicity to algae are available for ATG and MeaTG. In addition, a toxicity control performed within a biodegradation screening test with NaTG is available as supporting information.

 

ATG

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge, Respiration Inhibition Test", EEC Commission Directive 87/302/EEC and US EPA Draft Ecological Effects Test Guidelines OPPTS 850.6800.
Following a preliminary range-finding test, activated sewage sludge was exposed to an aqueous solution of the test material at concentrations of 10, 32, 100, 320 and 1000 mg active ingredient (ai)/l for a period of 3 hours at a temperature of 21°C with the addition of a synthetic sewage as a respiratory substrate.
The rate of respiration was determined after 30 minutes and 3 hours contact time and compared to data for the control and a reference material, 3,5-dichlorophenol.
The effect of the test material on the respiration of activated sewage sludge gave a 3-Hour EC50 of 530 mg ai/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 32 mg ai/l.

 

MeaTG

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge, Respiration Inhibition Test", EEC Commission Directive 87/302/EEC and US EPA Draft Ecological Effects Test Guidelines OPPTS 850.6800.
Following a preliminary range-finding test, activated sewage sludge was exposed to an aqueous solution of the test material at concentrations of 3.2, 10, 32, 100, 320 and 1000 mg active ingredient (ai)/l for a period of 3 hours at a temperature of 21°C with the addition of a synthetic sewage as a respiratory substrate.
The rate of respiration was determined after 30 minutes and 3 hours contact time and compared to data for the control and a reference material, 3,5-dichlorophenol.
Results. The effect of the test material on the respiration of activated sewage sludge gave a 3-Hour EC50 of greater than 1000 mg ai/l*. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 32 mg ai/l.
The reference material gave a 3-Hour EC50 value of 11 mg/l.

 

NaTG

The test item NaTG was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days in accordance with OECD Guideline 301F. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

A mean biodegradation of 10% or more of the test item was reached at day 5, the mean degradation was 39.5%. At the end of the 10-day window at day 15, the mean degradation was 65% and therefore the 10 day window criterion was passed. The mean biodegradation at test end after 28 days was 84.5%. The degradation rate 98% did reach 60% within the 10-day window and after 28 days. Therefore, the test item is considered to be readily biodegradable.

The reference item sodium benzoate was sufficiently degraded to 79% after 14 days and to 89% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

In the toxicity control containing both, the test item and the reference item sodium benzoate, 76% biodegradation was noted within 14 days and 84% biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

 

Conclusion

Since the substances are readily biodegradable, testing is not required. However, in the available studies the substances were not toxic to microorganisms.