Synthetic wollastonite

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Conducted between 2010-02-28 and 2010-03-01

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

The use of data derived for Soda-ash flux calcined kieselghur are justified for read-across to
synthetic wollastonite. Justification for read-across is warranted given the similarities in toxicity profile and physico-chemical properties for Soda-ash flux calcined kieselghur and synthetic wollastonite.
Considering the available data:
The source substance show no concerns for the environment.
The source substance has low acute toxicity and low toxicity in repeated dose studies, is non-irritant (skin and eye), non-sensitizing, non-mutagenic to bacteria, non-cytogenic and has low toxicity for reproductive and developmental toxicity.
Please see RAAF attached in Section 13. for further details.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Details on test solutions:

Test item preparation:
Amounts of test item ( 5, 16, 50, 160 and 500 mg) were each separately dispersed in approximately 250 mL of water and subjected to ultrasonication for approximately 15 minutes followed by prolonged mixing for 24 hours in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL) activated sewage sludge (200 mL) and water were added to a final volume of 500 mL to give the required concentrations of 10, 32, 100, 320 and 1000 mg/L.

Reference item preparation:
Two stock solutions of 50 and 160 mg/L were prepared by dissolving the reference item directly in water with the aid of ultrasonication for approximately 15 minutes. Aliquots (10 and 100 mL) of the 160 mg/L stock solution were removed and dispersed with activated sewage sludge, synthetic sewage sludge and water to give the final concentrations of 3.2 and 32 mg/L. .Similarly, a 100mL aliquot of the 50 mg/L stock solution was used to prepare the 10 mg/L concentration. The volumetric flasks containing the reference item were inverted several times to ensure homogeneity of the solutions.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21°C and was used on the day of collection. The pH of the sample was 7.4 and dissolved sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper using a Buchner funnel which was then rinsed 3 times with 10 mL of deionised reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105°C for at least 1 hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 3.7 g/L prior to used.

Total exposure duration:

3 h

Test temperature:

21 ± 1°C

pH:

pH values at the start and end of the exposure period are provided in table 3.

Nominal and measured concentrations:

10, 32, 100, 320 and 1000 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL darkened class Biological Oxygen Demand (BOD) bottle
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex water softener) giving water with a total hardness of approximately 140 mg/L as CaCO3. After dechlorination and softening the water was then passed through a series of computer controlled plate heat exchangers to acheive the required temperature.


OTHER TEST CONDITIONS
- Light intensity: The test was conducted under normal laboratory lighting

EFFECT PARAMETERS MEASURED : Rate of respiration

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Details on results:

Results are provided in table 1. Oxygen consumption rates and percentage inhibition val;ues for the control, test and reference item are given in table 2.

Observations made at 0 hours, 30 minutes and 3 hours showed that the control vessels contained a dark brown dispersion and the reference item vessels contained a dark brown dispersion with no undissolved reference item visible. Observations made at 0 hours prior to addition of activated sewage sludge and synthetic sewage showed that the test concentrations of 10 and 32 mg/L contained a clear colourless water column with particles of test item dispersed throughout and the test concentration of 100 mg/L contained a slightly cloudy dispersion with particles of test item dispersed throughout. The test concentrations of 320 and 1000 mg/L contained a cloudy dispersion with particles dispersed throughout.

Observations made after 30 minutes and 3 hours contact time showed that all the test concentrations contained a dark brown dispersion with particles of test item visible throughout.

Results with reference substance (positive control):

The reference material gave a 3-hour EC50 value of 7.8 mg/L, 95% confidence limits 6.1 - 9.9 mg/L

Table1:

	Soda-ash flux calcined kieselguhr		3,4-dichlorophenol
	ECx (3 hours) mg/L)	95% Confidence Limits (mg/L)	ECx (3 hours) mg/L)	95% Confidence Limits (mg/L)
EC20	> 1000	-	2.1	-
EC50	> 1000	-	7.8	6.1 – 9.9
EC80	> 1000	-	30	-
NOEC	1000	-	1.7	-

Table 2: Oxygen consumption rates and percentage inhibition values after 3 hours contact time

Nominal concentration (mg/L)	Initial O2reading (mgO2/L)	Measurement period (minutes)	Final O2reading (mg O2/L)	O2Consumption rates (mg O2/L/min)	% inhibition
Control R1 R2	5.5 4.1	5 4	2.7 1.9	0.56 0.55	- -
Test item 10 32 100 320 1000	5.4 5.1 4.9 3.1 5.2	6 5 4 2 5	2.2 2.2 2.5 1.9 2.1	0.53 0.58 0.60 0.60 0.62	5 [5] [8] [8] [12]
3,5-dichlorophenol 3.2 10 32	6.6 7.3 7.9	10 10 10	2.6 5.0 6.8	0.40 0.23 0.11	28 59 80

R1 -R2 = Replicates 1 and 2

[increase in respiration rate as compared to controls)

Table 3: pH values of the test preparations at the start and end of the exposure period.

Validity criteria fulfilled:

yes

Remarks:

The results of the study are considered valid if (i) the two control respiration rates are within 15% of each other and (ii) the EC50 (3 hour contact time) for 3,5-dichlorophenol lies within the range 5 to 30 mg/L. Validity criteria were fulfilled.

Conclusions:

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3 hour EC50 of > 1000 mg/L. The NOEC after 3 hours was 1000 mg/L.
Justification for read-across is warranted given the similarities in toxicity profile and physico-chemical properties for Soda-ash flux calcined kieselghur and synthetic wollastonite.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Conducted between 2010-02-28 and 2010-03-01

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

GLP compliance:

yes (incl. QA statement)

Details on test solutions:

Test item preparation:
Amounts of test item ( 5, 16, 50, 160 and 500 mg) were each separately dispersed in approximately 250 mL of water and subjected to ultrasonication for approximately 15 minutes followed by prolonged mixing for 24 hours in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL) activated sewage sludge (200 mL) and water were added to a final volume of 500 mL to give the required concentrations of 10, 32, 100, 320 and 1000 mg/L.

Reference item preparation:
Two stock solutions of 50 and 160 mg/L were prepared by dissolving the reference item directly in water with the aid of ultrasonication for approximately 15 minutes. Aliquots (10 and 100 mL) of the 160 mg/L stock solution were removed and dispersed with activated sewage sludge, synthetic sewage sludge and water to give the final concentrations of 3.2 and 32 mg/L. .Similarly, a 100mL aliquot of the 50 mg/L stock solution was used to prepare the 10 mg/L concentration. The volumetric flasks containing the reference item were inverted several times to ensure homogeneity of the solutions.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21°C and was used on the day of collection. The pH of the sample was 7.4 and dissolved sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper using a Buchner funnel which was then rinsed 3 times with 10 mL of deionised reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105°C for at least 1 hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 3.7 g/L prior to used.

Total exposure duration:

3 h

Test temperature:

21 ± 1°C

pH:

pH values at the start and end of the exposure period are provided in table 3.

Nominal and measured concentrations:

10, 32, 100, 320 and 1000 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL darkened class Biological Oxygen Demand (BOD) bottle
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex water softener) giving water with a total hardness of approximately 140 mg/L as CaCO3. After dechlorination and softening the water was then passed through a series of computer controlled plate heat exchangers to acheive the required temperature.


OTHER TEST CONDITIONS
- Light intensity: The test was conducted under normal laboratory lighting

EFFECT PARAMETERS MEASURED : Rate of respiration

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Details on results:

Results are provided in table 1. Oxygen consumption rates and percentage inhibition val;ues for the control, test and reference item are given in table 2.

Observations made at 0 hours, 30 minutes and 3 hours showed that the control vessels contained a dark brown dispersion and the reference item vessels contained a dark brown dispersion with no undissolved reference item visible. Observations made at 0 hours prior to addition of activated sewage sludge and synthetic sewage showed that the test concentrations of 10 and 32 mg/L contained a clear colourless water column with particles of test item dispersed throughout and the test concentration of 100 mg/L contained a slightly cloudy dispersion with particles of test item dispersed throughout. The test concentrations of 320 and 1000 mg/L contained a cloudy dispersion with particles dispersed throughout.

Observations made after 30 minutes and 3 hours contact time showed that all the test concentrations contained a dark brown dispersion with particles of test item visible throughout.

Results with reference substance (positive control):

The reference material gave a 3-hour EC50 value of 7.8 mg/L, 95% confidence limits 6.1 - 9.9 mg/L

Table1:

	Soda-ash flux calcined kieselguhr		3,4-dichlorophenol
	ECx (3 hours) mg/L)	95% Confidence Limits (mg/L)	ECx (3 hours) mg/L)	95% Confidence Limits (mg/L)
EC20	> 1000	-	2.1	-
EC50	> 1000	-	7.8	6.1 – 9.9
EC80	> 1000	-	30	-
NOEC	1000	-	1.7	-

Table 2: Oxygen consumption rates and percentage inhibition values after 3 hours contact time

Nominal concentration (mg/L)	Initial O2reading (mgO2/L)	Measurement period (minutes)	Final O2reading (mg O2/L)	O2Consumption rates (mg O2/L/min)	% inhibition
Control R1 R2	5.5 4.1	5 4	2.7 1.9	0.56 0.55	- -
Test item 10 32 100 320 1000	5.4 5.1 4.9 3.1 5.2	6 5 4 2 5	2.2 2.2 2.5 1.9 2.1	0.53 0.58 0.60 0.60 0.62	5 [5] [8] [8] [12]
3,5-dichlorophenol 3.2 10 32	6.6 7.3 7.9	10 10 10	2.6 5.0 6.8	0.40 0.23 0.11	28 59 80

R1 -R2 = Replicates 1 and 2

[increase in respiration rate as compared to controls)

Table 3: pH values of the test preparations at the start and end of the exposure period.

Validity criteria fulfilled:

yes

Remarks:

The results of the study are considered valid if (i) the two control respiration rates are within 15% of each other and (ii) the EC50 (3 hour contact time) for 3,5-dichlorophenol lies within the range 5 to 30 mg/L. Validity criteria were fulfilled.

Conclusions:

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3 hour EC50 of > 1000 mg/L. The NOEC after 3 hours was 1000 mg/L

Description of key information

An ASRI study was not available for Synthetic Wollastonite. A study was performed on the analogue substance Kieselghur soda-ash flux calcined in accordance with OECD guideline 209 (Activated sludge, respiration inhibition test) The EC50 was > 1000 mg/L after 3 hours contact time.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

In a key study (Youngs 2010) performed on the analogue substance Kieselghur soda-ash flux calcined, activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 10, 32, 100, 320 and 1000 mg/L for a period of 3 hours at a temperature of 21 ± 1°C with the addition of a synthetic sewage as a respiratory substrate. The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5 -dichlorophenol. The effect of the test item on the respiration of activated sewage sludge gave a 3 hour EC50 of > 1000 mg/L. The NOEC after 3 hours exposure was 1000 mg/L.

Justification for read-across is warranted given the similarities in toxicity profile and physico-chemical properties for Soda-ash flux calcined kieselghur and synthetic wollastonite.