2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol]

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:

30 March 2017

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 (Carbon and Ammonium Oxidation))

Version / remarks:

OECD Guidelines for Testing of Chemicals, No.: 209 Adopted: 22 July 2010.

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Commission Regulation (EU) 2017/735 of 14 February 2017 amending, for the purpose of its adaptation to technical progress, the Annex to Regulation (EC) No 440/2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)

Version / remarks:

Product Properties Test Guideline OCSPP 850.3300 (Public Draft OPPTS 850.6800, April 1996) of the United States Environment Protection Agency (EPA) "Modified Activated Sludge, Respiration Inhibition Test", June 2012

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

No further details specified

Analytical monitoring:

not specified

Vehicle:

no

Details on test solutions:

Based on poor solubility of the Test Item in water, a given amount Test Item was weighed directly into each individual flask just before the start of the experiment.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Species: Activated sludge, microorganisms from a domestic waste water treatment plant.
Source: The activated sludge was supplied from the sewage plant for domestic sewage in Veszprém, Hungary.
Conditioning: The activated sludge was supplied by the sewage plant for domestic sewage two days before the start of the experiment. Prior to use, the sludge was fed daily with 50 mL synthetic sewage per litre and kept aerated at 20 ± 2°C until use.
The activated sludge used for this study was washed and centrifuged and the supernatant liquid phase was decanted. The solid material was re-suspended in chlorine-free tap water and again centrifuged.
An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to dry weight was determined.
Based on this ratio, calculated amounts of wet sludge were suspended in chlorine-free tap water to yield a concentration equivalent to 3 g per litre (on dry weight basis). The pH of the activated sludge inoculum was determined to be pH 7.36. The activated sludge was used directly after conditioning.

Test type:

flow-through

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

No post exposure observation period specified in the study report.

Hardness:

Not specified

Test temperature:

20.2 – 21.8 °C

pH:

The pH of the activated sludge inoculum was determined to be pH 7.36.

Dissolved oxygen:

Not applicable

Salinity:

Not specified

Conductivity:

Not specified

Nominal and measured concentrations:

Nominal concentrations:
The test was performed at 3 concentrations of the Test Item with 5 replicates per concentration: 10 (TI11, TI12, TI13, TI14, TI15), 100 (TI21, TI22, TI23, TI24, TI25)
and 1000 mg/L (TI31, TI32, TI33, TI34, TI35) were used.

Details on test conditions:

Test units
Type and size: Appropriate glass beakers for 500 mL volume and BOD bottles with 300 mL volume.
Identification: Each test flask was uniquely identified with study code, treatment and replicate codes.

Test conditions
Surrounding type: Temperature controlled laboratory
Temperature: 20.2 – 21.8 °C
Aeration: With compressed air (about 1 L/min)
Recording: Test conditions were measured with suitable instruments and documented in the raw data.

PERFORMANCE OF THE TEST
Preparations of the test flasks
Each glass flask had a final volume of 400 mL (ratio of composition of each test mixture referring to 500 mL according to the guideline).
A volume of 12.8 mL synthetic sewage, an adequate amount of the Test Item and deionised water were placed into the test flask before the start of the incubation (see the Table 1 under Any other information). At the start of the test, 200 mL activated sludge inoculum with a sludge concentration of 3g/L of suspended solids was added to all flasks, except of the abiotic control flasks.
Abiotic controls in 5 parallels (A1, A2, A3, A4 and A5), and one untreated blank (B1) control was started as the first step of the test. Then at appropriate time intervals of approximately 30 minutes the further test groups were started. The second series were 4 different concentrations (without replicates) of the Reference Item (REF1, REF2, REF3, REF4) and to the second blank control (B2). The third series was the 5 replicates of the Test Item concentration of 10 mg/L nominal concentration (TI11, TI12, TI13, TI14 and TI15) and the third blank control (B3). The fourth series was the five replicates of Test Item concentration 100 mg/L nominal concentration (TI21, TI22, TI23, TI24 and TI25) and the fourth blank control (B4). The final series was the five replicates of Test Item concentration 1000 mg/L nominal concentration (TI31, TI32, TI33, TI34 and TI35) and the fifth blank control (B5).
In summary, 3 Test Item concentration series and one abiotic control series were prepared in 5 parallels with one blank control series by series. In parallel with the above test mixtures 4 Reference Item concentrations without replicates were also prepared with one blank control.

Measurement of Respiration Rate (Dissolved Oxygen)
For the measurement of the respiration rate a well-mixed sample of each treatment was poured into a BOD flask after approximately 3-hours incubation, and was not further aerated. The oxygen concentration was measured for approximately 15 minutes with an O2 electrode and was recorded in every half minute. The oxygen consumption (in mg O2 L-1 minute-1) was determined from the most linear part of the respiration curve.

Measurement of pH and temperature
The pH of the test mixtures was determined at the start and at the end of the incubation period in all test vessels. The temperature was measured in the laboratory with a min/max thermometer during the experiment.

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.

Basis for effect:

inhibition of total respiration

Details on results:

In comparison to the inoculum controls the inhibition of the respiration rate in the case of the activated sludge was between -0.84 % and 6.73 % in the examined range of 10–1000 mg/L of Test Item.
The average specific respiration rate (RS) of the untreated (Blank) controls (B1-B5) was 38.32 mg O2/L/h/g solid sludge.
The variation coefficient of oxygen uptake rate in above untreated replicates was 1.08%.

Results with reference substance (positive control):

In comparison to the controls, the inhibition of the respiration rate of the activated sludge was 79.88 % at the highest nominal concentration of 32.0 mg/L. At the nominal concentrations of 1.0, 3.2 and 10.0 mg/L 18.01 %, 27.37% and 54.13% inhibition of the respiration rate was calculated respectively.
The 3-hour EC50 of 3,5-Dichlorophenol was calculated to be 7.80 mg/L with 95% confidence limits of 5.99–10.16 mg/L.

Reported statistics and error estimates:

Not specified in the study report.

Influence of test item on oxygen consumption of activate sludge

Test group	Conc. of Test Item in test mix.	Total oxygen consumption rate (RT)	Specific respiration rate (RS)	Inhibition	pH values^iii
Name, ID	mg/L	mg O2/L/h	mg O2/L/h/g solid	%	Start	End
Abiotic Control
A1 A2 A3 A4 A5	1000	0.04 0.41 -0.04 0.00 -0.25	--- --- --- --- ---	--- --- --- --- ---	7.36 7.38 7.37 7.39 7.35	7.63 7.59 7.58 7.57 7.57
Blank Control
B1 B2 B3 B4 B5	0.0	57.6 56.4 57.6 57.9 57.9	38.40 37.60 38.40 38.60 38.60	--- --- --- --- ---	7.40 7.44 7.41 7.42 7.48	7.77 7.97 7.98 7.96 7.96
Reference Item
REF1 REF2 REF3 REF4	1.0 3.2 10.0 32.0	47.16 41.78 26.40 11.60	31.44 27.85 17.60 7.73	18.01 27.37 54.13 79.88	7.41 7.42 7.42 7.41	7.96 7.97 8.00 8.02
Test Item
TI1 TI2 TI3	10 100 1000	53.64 58.00 57.41	35.76 38.66 38.27	6.73 -0.84 0.18	7.40 7.46 7.46	7.98 7.97 7.96

ⁱⁱⁱIndividual pH values of the BOD flasks, except TI1-3, where the average values are reported.

Oxygen consumption data of the abiotic test mixtures

Oxygen consumption data of abiotic test mixture series
Half minutes	Test mixtures
	A1	A2	A3	A4	A5	B1
1	8.32	8.21	8.32	8.45	8.42	6.84
2	8.47	8.29	8.46	8.62	8.6	5.61
3	8.46	8.27	8.48	8.61	8.62	5.19
4	8.47	8.26	8.47	8.61	8.63	4.66
5	8.47	8.3	8.48	8.6	8.62	4.16
6	8.46	8.28	8.48	8.59	8.62	3.68
7	8.41	8.27	8.48	8.58	8.62	3.2
8	8.42	8.27	8.47	8.59	8.62	2.72
9	8.41	8.25	8.47	8.58	8.61	2.24
10	8.4	8.25	8.47	8.56	8.61	1.78
11	8.43	8.25	8.45	8.57	8.61	1.32
12	8.39	8.24	8.44	8.56	8.59	0.89
13	8.42	8.21	8.44	8.55	8.58	0.49
14	8.39	8.21	8.43	8.55	8.58	0.18
15	7.42	8.21	8.42	8.54	8.57	0.1
16	8.37	8.22	8.43	8.53	8.57	0.08
17	8.39	8.2	8.41	8.53	8.56	0.08
18	8.4	8.19	8.41	8.51	8.55	0.07
19	8.39	8.19	8.4	8.51	8.55	0.07
20	8.38	8.17	8.39	8.51	8.54	0.07
21	8.35	8.18	8.39	8.49	8.53	0.06
22	8.36	8.2	8.38	8.5	8.52	0.06
23	8.33	8.21	8.38	8.48	8.52	0.06
24	8.32	8.13	8.36	8.48	8.51	0.05
25	8.34	8.13	8.38	8.48	8.5	0.05
26	8.31	8.19	8.36	8.46	8.49	0.05
27	8.3	8.22	8.35	8.47	8.48	0.05
28	8.32	8.19	8.36	8.45	8.47	0.05
29	8.32	8.18	8.35	8.45	8.47	0.05
30	8.31	8.11	8.33	8.45	8.48	0.04
Q1	8.32	8.21	8.32	8.45	8.42	4.16
Q2	8.31	8.11	8.33	8.45	8.48	2.72
dt	14.5	14.5	14.5	14.5	14.5	1.5
RT(mg O2/L/minute)	0.00	0.01	0.00	0.00	0.00	0.96
RT(mg O2/L/hour)	0.04	0.41	-0.04	0.00	-0.25	57.60
RT(average)	0.03					-
RTs(mg O2/L/h/g solid sludge)	-					38.40

 

Oxygen consumption data of the reference Item test mixtures

Oxygen consumption data of reference item test mixture series
Half minutes	Test mixtures
Conc. (mg/L) of the Reference item	1.0	3.2	10.0	32.0
	REF1	REF2	REF3	REF4		B2
1	7.86	7.8	7.94	8.69		7.88
2	6.78	6.84	7.05	8.16		6.5
3	6.44	6.56	6.76	8.08		5.99
4	6.04	6.2	6.44	7.97		5.51
5	5.65	5.88	6.11	7.88		5.03
6	5.23	5.51	5.79	7.77		4.56
7	4.85	5.17	5.46	7.68		4.09
8	4.46	4.77	5.14	7.57		3.62
9	4.07	4.48	4.8	7.48		3.15
10	3.67	4.13	4.48	7.39		2.68
11	3.28	3.78	4.15	7.29		2.22
12	2.88	3.39	3.82	7.21		1.77
13	2.51	3.08	3.48	7.1		1.32
14	2.11	2.73	3.15	7.01		0.89
15	1.73	2.36	2.82	6.91		0.49
16	1.34	2	2.48	6.82		0.18
17	0.96	1.66	2.15	6.73		0.07
18	0.6	1.32	1.82	6.61		0.06
19	0.27	0.96	1.48	6.52		0.06
20	0.1	0.63	1.15	6.43		0.05
21	0.08	0.31	0.82	6.33		0.05
22	0.08	0.1	0.5	6.23		0.05
23	0.07	0.08	0.21	6.14		0.04
24	0.07	0.07	0.1	6.04		0.04
25	0.06	0.07	0.09	5.94		0.04
26	0.07	0.07	0.09	5.85		0.04
27	0.07	0.06	0.08	5.75		0.04
28	0.06	0.06	0.08	5.65		0.03
29	0.06	0.05	0.08	5.57		0.03
30	0.05	0.05	0.07	5.46		0.03
Q1	6.44	6.56	6.44	6.91		5.03
Q2	2.51	2.73	2.48	5.75		3.15
dt	5.0	5.5	9.0	6.0		2.0
RT(mg O2/L/minute)	0.79	0.70	0.44	0.19		0.94
RT(mg O2/L/hour)	47.16	41.78	26.40	11.60		56.40
RTs(mg O2/L/h/g solid sludge)	31.44	27.85	17.60	7.73		37.60
IT= [1 –(RT– RTA)/RTB] x 100
IT(%)	18.01	27.37	54.13	79.88		-

 

Oxygen consumption data of the test mixture series with Test Item concentration of 10 mg/L

Oxygen consumption data of test mixture series with test item concentration of 10 mg/L
Half minutes	Test mixtures
	TI11	TI12	TI13	TI14	TI15	B3
1	7.51	7.33	7.57	7.58	7.55	7.45
2	6.45	6.32	6.43	6.2	6.48	6.3
3	6.05	5.93	5.94	5.69	5.99	5.77
4	5.57	5.45	5.49	5.21	5.52	5.28
5	5.13	5	5.03	4.74	5.06	4.8
6	4.67	4.56	4.59	4.27	4.6	4.31
7	4.19	4.09	4.13	3.8	4.14	3.83
8	3.72	3.63	3.68	3.33	3.68	3.36
9	3.25	3.21	3.23	2.86	3.22	2.88
10	2.79	2.75	2.78	2.4	2.77	2.4
11	2.33	2.29	2.33	1.94	2.32	1.93
12	1.88	1.85	1.89	1.49	1.87	1.48
13	1.44	1.41	1.45	1.05	1.43	1.03
14	1.01	1	1.03	0.65	1.01	0.62
15	0.6	0.58	0.63	0.3	0.61	0.27
16	0.26	0.24	0.29	0.11	0.27	0.09
17	0.1	0.09	0.1	0.1	0.1	0.07
18	0.08	0.08	0.08	0.09	0.08	0.06
19	0.08	0.06	0.08	0.08	0.08	0.06
20	0.07	0.06	0.07	0.08	0.07	0.05
21	0.07	0.06	0.07	0.08	0.07	0.05
22	0.07	0.05	0.07	0.07	0.06	0.05
23	0.06	0.06	0.06	0.07	0.06	0.04
24	0.06	0.06	0.06	0.07	0.06	0.04
25	0.05	0.06	0.06	0.07	0.06	0.04
26	0.05	0.06	0.06	0.07	0.05	0.04
27	0.05	0.05	0.06	0.06	0.05	0.04
28	0.05	0.05	0.05	0.06	0.05	0.03
29	0.05	0.04	0.05	0.06	0.05	0.03
30	0.05	0.03	0.05	0.06	0.05	0.03
Q1	5.13	5.45	5.49	5.21	5.52	5.28
Q2	2.79	2.75	2.79	3.33	3.68	2.88
dt	2.5	3.0	3.5	2.0	2.0	2.5
RT(mg O2/L/minute)	0.94	0.90	0.77	0.94	0.92	0.96
RT(mg O2/L/hour)	56.16	54.00	46.46	56.40	55.20	57.60
Average RT(mg O2/L/hour)	53.64					-
RTs(mg O2/L/h/g solid sludge)	37.44	36.00	30.97	37.60	36.80	38.40
IT= [1 –(RT– RTA)/RTB] x 100
IT(%)	6.73					-
Oxygen update of control (blank) replicates (RT(mg O2/L/hour))		B1	B2	B3	B4	B5
		57.60	56.40	57.60	57.90	57.90
Variation coefficient of oxygen update of the blanks (B1-B5) (%)						1.08
Average Oxygen update of control (blank) replicates (RT(average)(mg O2/L/hour))						57.48
Average Specific Oxygen update of control (blank) replicates (RT(average)(mg O2/L/h/g solid sludge))						38.32

 

Oxygen consumption data of the test mixture series with Test Item concentration of 100 mg/L

Oxygen consumption data of test mixture series with test item concentration of 100 mg/L
Half minutes	Test mixtures
	TI21	TI22	TI23	TI24	TI25	B4
1	7.16	6.92	7.33	7.43	7.17	7.6
2	6.22	5.82	6.15	6.1	5.83	6.34
3	5.7	5.31	5.66	5.59	5.4	5.92
4	5.23	4.79	5.18	5.1	4.89	5.43
5	4.75	4.32	4.7	4.61	4.4	4.94
6	4.26	3.88	4.23	4.12	3.91	4.46
7	3.77	3.35	3.76	3.64	3.41	3.98
8	3.29	2.9	3.28	3.16	2.92	3.49
9	2.81	2.39	2.81	2.68	2.42	3.01
10	2.33	1.92	2.34	2.2	1.94	2.53
11	1.87	1.46	1.88	1.73	1.47	2.06
12	1.41	1	1.42	1.28	1.02	1.59
13	0.97	0.58	0.98	0.84	0.6	1.14
14	0.55	0.23	0.58	0.45	0.24	0.71
15	0.22	0.08	0.24	0.16	0.1	0.33
16	0.09	0.07	0.1	0.1	0.08	0.1
17	0.08	0.07	0.09	0.09	0.07	0.07
18	0.07	0.06	0.08	0.08	0.07	0.06
19	0.07	0.07	0.07	0.08	0.06	0.05
20	0.06	0.05	0.07	0.07	0.06	0.05
21	0.06	0.04	0.07	0.07	0.06	0.05
22	0.06	0.05	0.07	0.07	0.05	0.04
23	0.06	0.05	0.06	0.06	0.05	0.04
24	0.05	0.05	0.06	0.06	0.05	0.04
25	0.05	0.04	0.06	0.06	0.05	0.04
26	0.05	0.05	0.06	0.06	0.05	0.03
27	0.05	0.05	0.06	0.06	0.04	0.03
28	0.05	0.05	0.06	0.06	0.04	0.03
29	0.05	0.03	0.05	0.06	0.04	0.03
30	0.04	0.04	0.05	0.06	0.04	0.03
Q1	5.23	5.82	4.70	4.12	4.89	4.94
Q2	2.81	2.90	2.81	2.68	3.41	3.01
dt	2.5	3.0	2.0	1.5	1.5	2.0
RT(mg O2/L/minute)	0.97	0.97	0.95	0.96	0.99	0.97
RT(mg O2/L/hour)	58.08	58.40	56.70	57.60	59.20	57.90
Average RT(mg O2/L/hour)	58.00					-
RTs(mg O2/L/h/g solid sludge)	38.72	38.93	37.80	38.40	39.47	38.60
IT= [1 –(RT– RTA)/RTB] x 100
IT(%)	-0.84					-

 

Oxygen consumption data of the test mixture series with Test Item concentration of 1000 mg/L

Oxygen consumption data of test mixture series with test item concentration of 1000 mg/L
Half minutes	Test mixtures
	TI31	TI32	TI33	TI34	TI35	B5
1	7.13	6.99	7.15	7.26	7.43	7.31
2	6.05	5.93	6.1	5.99	6.08	6.14
3	5.65	5.55	5.6	5.46	5.55	5.62
4	5.15	5	5.12	4.98	5.06	5.11
5	4.64	4.53	4.65	4.49	4.58	4.62
6	4.2	4.13	4.18	4.02	4.1	4.14
7	3.7	3.64	3.72	3.54	3.61	3.66
8	3.24	3.18	3.24	3.07	3.12	3.17
9	2.76	2.73	2.78	2.6	2.65	2.69
10	2.28	2.26	2.32	2.13	2.17	2.21
11	1.83	1.79	1.86	1.67	1.71	1.74
12	1.37	1.33	1.41	1.22	1.25	1.29
13	0.94	0.86	0.98	0.8	0.82	0.85
14	0.54	0.48	0.58	0.41	0.43	0.46
15	0.21	0.17	0.25	0.15	0.15	0.17
16	0.09	0.08	0.11	0.1	0.08	0.08
17	0.08	0.08	0.09	0.09	0.07	0.06
18	0.07	0.06	0.08	0.08	0.07	0.06
19	0.06	0.06	0.08	0.08	0.06	0.05
20	0.06	0.06	0.07	0.07	0.06	0.05
21	0.06	0.07	0.07	0.07	0.06	0.05
22	0.06	0.04	0.07	0.07	0.05	0.04
23	0.06	0.03	0.06	0.07	0.05	0.04
24	0.05	0.06	0.06	0.06	0.05	0.04
25	0.05	0.04	0.06	0.06	0.05	0.04
26	0.05	0.06	0.06	0.06	0.04	0.03
27	0.05	0.03	0.05	0.06	0.04	0.03
28	0.04	0.05	0.05	0.06	0.04	0.03
29	0.05	0.05	0.05	0.06	0.04	0.03
30	0.04	0.04	0.05	0.06	0.04	0.03
Q1	5.65	5.00	5.12	5.46	5.06	4.62
Q2	2.76	2.73	2.78	2.60	2.65	2.69
dt	3.0	1.5	6.0	3.0	2.5	2.0
RT(mg O2/L/minute)	0.96	1.51	0.39	0.95	0.96	0.97
RT(mg O2/L/hour)	57.80	90.80	23.40	57.20	57.84	57.90
Average RT(mg O2/L/hour)	57.41					-
RTs(mg O2/L/h/g solid sludge)	38.53	60.53	15.60	38.13	38.56	38.60
IT= [1 –(RT– RTA)/RTB] x 100
IT(%)	0.18					-

 

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study the observed endpoint for the effect of the Test Item was the 3-hour EC50 value which was considered to be > 1000 mg/L.
Based on the results of this study, as the Test Item had no inhibition effect on the total respiration rate of the microorganisms of the activated sludge at 1000 mg/L, no further
testing was necessary.

Executive summary:

A laboratory test was carried out with the Test Item to evaluate its effect on microorganisms from activated sludge by measuring the respiration rate.

The test concentrations (10, 100 and 1000 mg/L) were chosen to permit the determination of the approximate EC50 and to identify if further, more detailed analysis is required.

 

The effect of Test Item on the total respiration rate of activated sludge microorganisms was investigated in this study, using the method, described by the OECD Guidelines for Testing of Chemicals, No.: 209 Adopted: 22 July 2010.

 

The total respiration rate (oxygen consumption) of an aerobic activated sludge is a result of the oxidation of organic carbons, and of ammonium to nitrite or nitrate.

The purpose of the 3-hour toxicity test was to evaluate the influence of the Test Item on the activity of activated sludge by measuring the total respiration rate under defined conditions, to calculate the inhibition effect, based on the measured data.

 

The test method and the sensitivity of the activated sludge inoculum was checked, using the 3,5-Dichlorophenol (3,5-DCP). The EC50 result of 3,5-DCP was compared to the result of international ring test, organized in 2004, described in the point 12 of OECD 209.

 

The EC50 value is the concentration of the Test Item at which the respiration rate is 50% of that of the control under the conditions described in this study. If the EC50 value is >1000 mg/L then further testing at lower concentrations or for nitrification inhibition is not necessary.

 

The reference control results showed that in this study, the inoculum and methodology used provided a good measure of inhibition of activated sludge respiration rate, hence the study was considered to be valid.

 

In conclusion, under the conditions of this study the observed endpoint for the effect of the Test Item was the 3-hour EC50 value which was considered to be >1000 mg/L.

Based on the results of this study, as the Test Item had no significant inhibition effect on the total respiration rate of the microorganisms of the activated sludge at the limit test concentration of 1000 mg/L, no further testing was necessary.

Description of key information

The total respiration rate of activated sludge microorganisms was investigated in this study, using the method, described by the OECD Guidelines for Testing of Chemicals, No.: 209 Adopted: 22 July 2010.

3-hour EC50 value which was considered to be >1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

A laboratory test was carried out with the Test Item to evaluate its effect on microorganisms from activated sludge by measuring the respiration rate.

The test concentrations (10, 100 and 1000 mg/L) were chosen to permit the determination of the approximate EC50 and to identify if further, more detailed analysis is required.

 

The reference control results showed that in this study, the inoculum and methodology used provided a good measure of inhibition of activated sludge respiration rate, hence the study was considered to be valid.

 

In conclusion, under the conditions of this study the observed endpoint for the effect of the Test Item was the 3-hour EC50 value which was considered to be >1000 mg/L.

Based on the results of this study, as the Test Item had no significant inhibition effect on the total respiration rate of the microorganisms of the activated sludge at the limit test concentration of 1000 mg/L, no further testing was necessary.