Non-graphitic carbon fibre

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-11-02 to 2012-12-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

carbon

EC Number:

701-026-1

Cas Number:

7440-44-0

Molecular formula:

C up to (C80N5H16O)n

IUPAC Name:

carbon

Test material form:

solid: fibres

Details on test material:

- milled carbonised PAN based fibre (Sigrafil C30 M150 UNS)
- for further details on the test material, see section 1.4, endpoint "Non-graphitic carbon fibre (carbonised PAN based fibre, milled)", attached document "Analytics_milled_carbonised_PAN_based_fibre.pdf"

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

Preparation and application of test solution (especially for difficult test substances)
- Method: water accomodated fraction (WAF according to OECD 23)
- Eluate: not applicable
- Differential loading: no
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): not applicable
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): not applicable
- Evidence of undissolved material (e.g. precipitate, surface film, etc): yes

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: yes
- Method of cultivation: the activated sludge was aerated until it was used in the test and fed daily with 50 mL/L synthetic sewage feed
- Pretreatment: the sludge was filtered, washed with tap water and re-suspended in tap water
- Initial biomass concentration: 1.40 g suspended solids/L in the test

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

not applicable

Test conditions

Hardness:

1.08 mmol/L

Test temperature:

18.9 – 20.7 °C

pH:

8.09

Dissolved oxygen:

purified air, using Pasteur pipettes, flow approximately 0.75 L/min

Conductivity:

330 µS/cm at 20 °C

Nominal and measured concentrations:

0 mg/L, 1 mg/L, 10 mg/L, 100 mg/L, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass beakers
- Type (delete if not applicable): open
- Aeration: purified air, using Pasteur pipettes, flow approx. 0.75 L/min
- No. of vessels per concentration (replicates): 5 for a concentration of 1000 mg/L; 1 for a concentration of 1 mg/L, 10 mg/L, and 100 mg/L, respectively
- No. of vessels per control (replicates): 1 per concentration
- No. of vessels per vehicle control (replicates): not applicable
- Biomass loading rate: Dry matter in the test: 1.40 g suspended solids/L


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Wasserwerk Maikammer
- Total organic carbon: 0.4 mg/L
- Particulate matter: not determined
- Metals: not determined
- Pesticides: < LOD
- Chlorine: not determined
- Alkalinity: not determined
- Ca/Mg ratio: 49.7 mg/L : 6.7 mg/L
- Conductivity: 330 µS/cm at 20 °C
- Culture medium different from test medium: no
- Intervals of water quality measurement: not reported

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: not applicable
- Light intensity: not applicable

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): O2 consumption

TEST CONCENTRATIONS
- Spacing factor for test concentrations: log 10
- Range finding study: no
- Test concentrations: 0 mg/L, 1 mg/L, 10 mg/L, 100 mg/L, 1000 mg/L
- Results used to determine the conditions for the definitive study: 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 95% confidence interval not determinable

Effect concentrations 2

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 95% confidence interval not determinable

Effect concentrations 3

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

Remarks:

respiration rate

Remarks on result:

other: 95% confidence interval not determinable

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: yes
- Effect concentrations exceeding solubility of substance in test medium: yes

Results with reference substance (positive control):

- Results with reference substance valid: yes
- Relevant effect levels: no effect up to the tested concentration of 1000 mg/L

Reported statistics and error estimates:

not applicable

Any other information on results incl. tables

Parameter	Value	95% Confidence Interval
NOEC	≥1000 mg/L	not determinable
3h EC10	1000 mg/L	not determinable
3h EC50	1000 mg/L	not determinable

Raw data:

Vessel No.	Content	Concentration in mg/L	O2consumption in mg/(L*min)	O2consumption in mg/(L*h)	Inhibition in %	pH
1	Control	0	0.7352	44.113	0	7.7
2	Control	0	0.7156	42.937	0	7.7
3	Positive Control	5	0.4803	28.821	32.7	7.8
4	Positive Control	10	0.2847	17.084	60.1	7.8
5	Positive Control	20	0.1351	8.109	81.1	7.8
6	Positive Control	40	0.0658	3.946	90.8	7.8
7	Control	0	0.7356	44.137	0	7.7
8	Control	0	0.7425	44.552	0	7.7
9	Test Item	1001.6	0.7423	44.540	-3.9	7.6
10	Test Item	1002.0	0.7206	43.237	-0.9	7.7
11	Test Item	1001.2	0.7429	44.571	-4.0	7.7
12	Test Item	1001.0	0.7569	45.414	-6.0	7.6
13	Test Item	1003.4	0.7387	44.320	-3.4	7.6
14	Test Item	102.2	0.7508	45.045	-5.1	7.6
15	Test Item	10	0.7577	45.461	-6.1	7.6
16	Test Item	1	0.6743	40.458	5.6	7.5
17-34	*	*	*	*	*	*
35	Control		0.6971	41.828	0	7.5
36	Control		0.6592	39.552	0	7.6

in vessels 17 – 34 other items were measured

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

No significant inhibition of the respiration of activated sludge was determined when exposed to the test item (milled carbonised PAN based fibre) for 3 hours. The NOEC has been determined as >= 1000 mg/L.

Executive summary:

The test item (milled carbonised PAN based fibre) was tested with five concentrations (ranging from 1003.4 to 1 mg/L) over three hours. Activated sludge was used as inoculum. It was taken from a domestic sewage treatment plant and washed prior to the test. The dry matter was determined to be 2.80 g suspended solids/L, corresponding to a concentration of 1.4 g suspended solids/L in the test.

3,5-Dichlorophenol was used as positive control and four concentrations were tested. An EC50 value of 7.7 mg/L (95% confidence interval: 5.3 – 10 mg/L) was determined which lies within the range of 2 – 25 mg/L.

Because no significant inhibition was observed with the test item no additional experiment was performed.

The O₂consumption in the treatment with the highest test item concentration (1000 mg/L) was higher than in the control experiment. Therefore, the test item concentration of 1000 mg/L is stated as the NOEC. No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.