Ammonium mercaptoacetate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 2003/07/16 to 2004/11/10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

An amount of test material (2809 mg) was dissolved in water and the volume adjusted to 1000 ml to give a 2809 mg/l stock solution, equivalent to 2000 mg active ingredient (ai)/l from which dilutions were made to give 1000 and 100 mg ai/l stock solutions.
Aliquots (50 and 160 ml) of the 100 mg ai/l stock solution were each separately dispersed with synthetic sewage (16 ml), activated sewage sludge (200 ml) and water, to a final volume of 500 ml, to give the required concentrations of 10 and 32 mg ai/l.
Similarly, aliquots (50 and 160 ml) of the 1000 mg ai/l and an aliquot (250 ml) of the 2000 mg ai/l stock solution were used to prepare the test concentrations of 100, 320 and 1000 mg ai/l respectively.
The volumetric flasks containing the stock solutions were inverted several times to ensure homogeneity of the stock solutions. Analysis of the concentration, homogeneity and stability of the test material in the test preparations was not appropriate to the Test Guideline.

Test organisms (species):

activated sludge

Details on inoculum:

- Laboratory culture: mixed population of activated sewage sludge micro-organisms, obtained for the definitive test on 3 September 2004 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK.
- Preparation of inoculum for exposure: maintained on continuous aeration in the laboratory at 21ºC and used on the day of collection. The pH of the sample was 8.0. The suspended solids was equal to 4.1 g/l prior to use.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

100 mg/L as CaCO3

Test temperature:

21°C

pH:

8.2-8.3

Salinity:

no data

Nominal and measured concentrations:

Nominal concentrations: 10, 32, 100, 320, and 1000 mg ai/l.

Details on test conditions:

TEST SYSTEM
- 250 ml darkened glass Biological Oxygen Demand (BOD) bottle.
- The rate of respiration was measured using a Yellow Springs dissolved oxygen meter fitted with a BOD probe.
- The control group was maintained under identical conditions but not exposed to the test material.
- Preparation of the test system: 16 ml of synthetic sewage was diluted to 300 ml with water and 200 ml of inoculum added in a 500 ml conical flask (first control). The mixture was aerated with compressed air via narrow bore glass tubes at a rate of approximately 0.5 – 1 litre per minute. Thereafter, at 15 minute intervals the procedure was repeated with appropriate amounts of the reference material being added. As each vessel reached 30 minutes contact time an aliquot was removed from the conical flask and poured into the measuring vessel.

OTHER TEST CONDITIONS
- Lighting: normal laboratory lighting.

TEST MEDIUM / WATER PARAMETERS
- Laboratory tap water dechlorinated by passage through an activated carbon filter and partly softened.
- Total hardness of approximately 100 mg/l as CaCO3.

TEST CONCENTRATIONS
- Range finding study: nominal test concentrations of 10, 100 and 1000 mg ai/l. The test material was dissolved directly in water.
- Results used to determine the conditions for the definitive study: Significant inhibition of respiration was observed at 100 and 1000 mg ai/l, however, there were no significant effects on respiration at 10 mg ai/l. Based on this information test concentrations of 10, 32, 100, 320 and 1000 mg ai/l were selected for the definitive test.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (Sigma-Aldrich Batch No. 15809K1023)

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

530 mg/L

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

32 mg/L

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

820 mg/L

Details on results:

The following results were derived:

Ammonium Thioglycolate EC50 (30 minutes): 820 mg ai/l
3,5-dichlorophenol EC50 (30 minutes): 14 mg/l
Variation in respiration rates of controls 1 and 2 after 30 minutes: ± 4%.

Ammonium Thioglycolate EC50 (3 hours): 530 mg ai/l
3,5-dichlorophenol EC50 (3 hours): 7.7 mg/l
Variation in respiration rates of controls 1 and 2 after 3 hours: ± 1%.

Results with reference substance (positive control):

Two stock solutions of 50 and 160 mg/l were prepared by dissolving the reference material directly in water with the aid of ultrasonication for approximately 20 minutes.
Aliquots (10 and 100 ml) of the 160 mg/l stock solution were removed and dispersed with activated sewage sludge, synthetic sewage and water to give the final concentrations of 3.2 and 32 mg/l.
Similarly, a 100 ml aliquot of the 50 mg/l stock solution was used to prepare the 10 mg/l concentration.
The volumetric flasks containing the reference material were inverted several times to ensure homogeneity of the solutions.

3,5-dichlorophenol EC50 (30 minutes): 14 mg/l
3,5-dichlorophenol EC50 (3 hours): 7.7 mg/l

The validation criteria for the control respiration rates and reference material EC50 values have been satisfied.
- In some instances, the initial and final dissolved oxygen concentrations were below those recommended in the test guidelines (6.5 mg O2/l and 2.5 mg O2/l respectively).
This was considered to have had no adverse effect on the results of the test given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace. Observations made throughout the test period showed that at the test concentration of 1000 mg ai/l no undissolved test material was visible.
- the two control respiration rates are within 15% of each other.
- the EC50 (3-Hour contact time) for 3,5-dichlorophenol lies within the range 5 to 30 mg/l.

Validity criteria fulfilled:

yes

Conclusions:

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.

Executive summary:

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.
The reference material gave a 3-Hour EC50 value of 7.7 mg/l.

Description of key information

3 hr EC50 = 530 mg/L, 3 hr NOEC = 32 mg/L (OECD TG 209)

 

Key value for chemical safety assessment

EC50 for microorganisms:

530 mg/L

EC10 or NOEC for microorganisms:

32 mg/L

Additional information

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.