Androsta-1,4-diene-17-carbothioic acid, 6,9-difluoro-11-hydroxy-16-methyl-3-oxo-17-(1-oxopropoxy)-, (6.alpha.,11.beta.,16.alpha.,17.alpha.)-

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:

20th May 2003 - 27th November 2003

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:

yes

Remarks:

Two deviations occurred but didn't affect the outcome/integrity/validity of the study: It wasn't possible to issue the draft report to the proposed schedule. The inoculum pH was measured before the final dilution, not afterwards as per the protocol.

GLP compliance:

yes

Specific details on test material used for the study:

Appearance: White/off-white crystalline solid
Batch Number: H030714
Receipt Date: 26 April 2003
Storage Conditions: Room temperature, 20±10°C
Expiry Date: Not stated on recipt

Details on test solutions:

Activate sludge was collected from one of the sludge return lines at Burley Menston sewage treatment work (Yorkshire Water), a treatment plant with a waste-water catchment that is predominantly domestic. On arrival in the laboratory, each sample was aerated by means of a compression air supply delivered through a diffuser block.

The suspended solids concentration of the activated sludge was determined by filtering a 25mL subsample through a pre-dried and pre-weighed glass microfibre filter (Whatman GF/C). The filter and retained solids were then dried at 105°C (nominal) in a conventional oven, re-weighed and the contribution made by the sludge solids were determined by difference.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The inoculum used in this study was not deliberately acclimated or adapted to Thio Acid Propionate (CCI22363) before exposure to the test substance under test conditions. The inoculum was maintained by aeration at all times and fed overnight with synthetic sewage at a rate of 50mL/L during the interval between preparation and final use.

Range-Finder:
The suspended solids concentration determined before the range-finder test was 4.0g/L, within the acceptance range of 4g/L ± 10%, and the pH was 6.02, within the acceptance range of pH 6 to 8.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

21° C

Nominal and measured concentrations:

All mixtures comprised 16mL synthetic sewage diluted to 300mL with reverse-osmosis water and the test substance or 3,5-DCP stock solution. Inoculation entailed addition of 200mL activated sludge.

Details on test conditions:

The inoculum was maintained, the test mixtures incubated and the test measurements carried out in a facility where the termperature was set at a nominal 21°C. Temperatures recorded over the duration of this study were compliant with the method requirement that temperatures be maintained in the range 20±2°C.

Reference substance (positive control):

yes

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

ca. 9.81 mg/L

Nominal / measured:

estimated

Conc. based on:

other: 3,5-DCP

Basis for effect:

inhibition of total respiration

Details on results:

The applied concentrations of test substance were plotted against the resulting percentage inhibition observed. No significant inhibition was observed. Consequently, the EC50 of the test substance must be greater than the highest tested concentration, 1000mg/L. Following consideration of the data, no further assessment was made. From a plot of the inhibition against dosed concentration, the EC50 for 3,5-DCP was estimated to be 12.9mg/L.

The applied concentrations of test substance were plotted against the resulting percentage inhibition observed. No significant inhibition was observed. Consequently, the EC50 of the test substance must be greater than the highest tested concentration, 1000mg/L. Following consideration of the data, no further assessment was made. From a plot of the inhibition against dosed concentration, the EC50 for 3,5-DCP was estimated to be 12.9mg/L.

Range-Finder Test, Respiration Rate and Inhibition Data:

Treatment	Respiration Rage (mgO2/L/h)	Mean	% Inhibition
Control	63.33^1	68.42	na
	70.43^1
	72.17^2
	67.76^2
1mg Thio Acid Propionate/L	66.43	69.62	0
	72.82
10mg Thio Acid Propionate/L	71.57	70.88	0
	70.20
100mg Thio Acid Propionate/L	66.55	70.54	0
	74.54
5mg 3,5-DCP/L	53.76	na	21
15mg 3,5-DCP/L	30.00	na	56
45mg 3,5-DCP/L	9.81	na	86

¹ = start-of-series control

² = end-of-series control

na = not applicable

Validity criteria fulfilled:

yes

Conclusions:

The impact of Thio Acid Propionate (CCI22363( on the respiration of activated sludge was assessed according to Guideline 209 of the Organisation for Economic Co-operation and Development (OECD). The method is identical to that described in EU Commission Directive 87/302/EEC.

Samples of activated sludge were exposed to Thio Acid Propionate (CCI22363) at a range of concentrations between 0.1 and 1000mg/L, and their respiration rates measured after 3 hours contact time. The test substance did not cause significant inhibition of the respiration rate of activated sludge at concentrations up to and including 1000mg/L. Consequently the EC50 was not determined from the results of this stud, but must be greater than 1000mg/L, the highest dose tested.

Both the Guideline validity criteria that relate to the reference inhibitor response and conformity of the control respiration rates were met. The results of this study are therefore considered valid.

Executive summary:

The impact of Thio Acid Propionate (CCI22363( on the respiration of activated sludge was assessed according to Guideline 209 of the Organisation for Economic Co-operation and Development (OECD).  The method is identical to that described in EU Commission Directive 87/302/EEC.

Samples of activated sludge were exposed to Thio Acid Propionate (CCI22363) at a range of concentrations between 0.1 and 1000mg/L, and their respiration rates measured after 3 hours contact time. The test substance did not cause significant inhibition of the respiration rate of activated sludge at concentrations up to and including 1000mg/L. Consequently the EC₅₀ was not determined from the results of this stud, but must be greater than 1000mg/L, the highest dose tested.

Both the Guideline validity criteria that relate to the reference inhibitor response and conformity of the control respiration rates were met. The results of this study are therefore considered valid.

Description of key information

The impact of Thio Acid Propionate (CCI22363( on the respiration of activated sludge was assessed according to Guideline 209 of the Organisation for Economic Co-operation and Development (OECD).  The method is identical to that described in EU Commission Directive 87/302/EEC.

Samples of activated sludge were exposed to Thio Acid Propionate (CCI22363) at a range of concentrations between 0.1 and 1000mg/L, and their respiration rates measured after 3 hours contact time. The test substance did not cause significant inhibition of the respiration rate of activated sludge at concentrations up to and including 1000mg/L. Consequently the EC50 was not determined from the results of this stud, but must be greater than 1000mg/L, the highest dose tested.

Both the Guideline validity criteria that relate to the reference inhibitor response and conformity of the control respiration rates were met. The results of this study are therefore considered valid.