(3E)-dec-3-en-2-one

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:

23 March 2011 - 10 November 2011

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))

Deviations:

yes

Remarks:

See "Any other information on materials and methods incl. tables" below.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test item (3E)-dec-3-en-2-one was poorly soluble in water and thus it was directly dosed into each test flask, which was subsequently filled with tap water. The test item was dissolved into the tap water as homogeneously as possible.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge, from a domestic waste water treatment plant was supplied by the municipal sewage treatment plant Bensheim, Germany.
The activated sludge used for this study was used as collected, coarse paiticles were removed by settling for a short period (10 minutes) and then the upper layer decanted.
During holding prior to use the sludge was fed with 50 mL synthetic sewage per litre and kept aerated at room temperature overnight.
An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight determined. Based on the sludge dry matter, calculated amounts of wet sludge were suspended in tap water to yield a concentration equivalent to about 2.5 g/L on dry weight basis. This level gives a concentration of 1 g/L suspended solids in the test medium. The pH of the activated sludge inoculum was 7.6 and therefore no adjustment necessary.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

16 - 22°C

Nominal and measured concentrations:

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

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass flasks of approximately 1 litre volume and Karlsruher flasks of 250 mL volume
- Type (delete if not applicable): open
- Aeration: Compressed air (0.945 litre per minute). During the 3 hour aeration period the flasks were stirred on a magnetic stirrer to maintain sludge flocs in suspension.
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): Six controls (tap water, synthetic sewage and inoculum, but without addition of the test item) were tested in parallel.
- Sludge concentration (weight of dry solids per volume): 2.5 g d.w./L
- Nutrients provided for bacteria: Synthetic Sewage Feed (16 g peptone, 11 g meat extract, 3 g urea, 0.7 g NaCl, 0.4 g CaC12 x 2H2O, 0.2 g MgSO4 x 7H2O; 2.8 g K2HPO4 were filled up to 1 litre with deionised water)
- Nitrification inhibitor used (delete if not applicable): N-allylthiourea

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water


OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
For the measurement of the respiration rate a well-mixed sample of each test medium was poured into a Karlsruher flask after exactly 3 hours incubation time and was not further aerated during measurement. The oxygen concentration was then measured with an oxygen electrode and recorded for about ten minutes. During measurement, the samples were continuously stirred on a magnetic stirrer. The oxygen consumption (in mg O2.L-1.minute-1) was determined from the most linear part of the respiration curve in the range between approximately 7.0 - 2.0 mg O2/L. In case of low oxygen consumption the values over a period of 10 minutes were used. In some cases of a fast drop-off below 2.0 mg O2/L shorter measurement intervals (e. g. 7 minutes) were used.
Since nitrification effects of the activated sludge may have influence on the respiration rates of the test item, therefore, total oxygen consumption is corrected by the oxygen consumption with the nitrification inhibitor N-allylthiourea.

Reference substance (positive control):

yes

Remarks:

3-5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

236.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

76.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: The 3-hour EC50 of 3,5-dichlorphenol was calculated as 4.4 mg/L and was therefore within the acceptable range of 2 to 25 mg/L.

Reported statistics and error estimates:

The EC50 value is calculated with the ToxRat software by probit analysis using linear maximum likelihood regression.

Inhibition of Respiration rate

- Total respiration:

In comparison to the inoculum controls the respiration rate of the activated sludge was not inhibited at the test concentrations of 10 and 32 mg/L. The respiration rate of the activated sludge was slightly inhibited by 27.7% at 100 mg/L and 63.6% at 320 mg/L. At a nominal concentration of 1000 mg/L, the respiration rate was inhibited by 79.5% by a maximum. Concentrations exceeding 1000 mg/L nominal were not tested (see Table 1).

Based on measured inhibition rates, the 3-hour EC10, EC20 and EC50 and their 95% confidence limits were determined.

The results are listed below:

	EC10	EC20	EC50
Value [mg/l]	42.1	76.1	236.6
lower 95%-cl	6.9	21.3	140.6
upper 95%-cl	83.4	130.5	406.1

Table 1. Influence of (3E)-dec-3 -en-2 -one and the Reference Item 3,5-Dichlorophenol on Total Oxygen Consumption of Activated Sludge

						pH-values (mean)1		Oxygen concentration (mean)1 (mg O2/L)
Flask No.	Treatment	Concentration (mg/L)	Oxygen consumption (mean)1 (%)	Coefficient of Varation (mean)1 (%)	Inhibition (mean)1 (%)	start*	end*	start*	end*
1,2,18,19,45,46	control	-	28.70	10.50	-	7.5	8.3	9.1	8.1
3-7	3,5-DCP	3.2	16.20	-	43.6	7.6	8.3	8.9	8.8
8-12	3,5-DCP	10	9.72	-	66.1	7.6	8.3	9.1	8.2
13-17	3,5-DCP	32	4.44	-	84.5	7.6	8.3	9.0	9.2
20-24	Test item	10	32.97	-	-14.9	7.6	8.3	9.0	6.8
25-29	Test item	32	33.72	-	-17.5	7.3	8.3	9.1	8.2
30-34	Test item	100	20.76	-	27.7	7.3	8.3	9.2	8.3
35-39	Test item	320	10.44	-	63.6	7.3	8.4	9.5	9.1
40-44	Test item	1000	5.88	-	79.5	7.3	8.5	9.6	9.3

1) mean value of 5 replicates

* start and end of 3-hour aeration

- Heterotrophic Respiration without Nitrification:

In comparison to the inoculum controls the respiration rate of the activated sludge was not inhibited at the test concentrations of 10 and 32 mg/L. The respiration rate of the activated sludge was slightly inhibited by 6.5% at 100 mg/L and 36.0% at 320 mg/L. At a nominal concentration of 1000 mg/L, the respiration rate was inhibited by 57.3% by a maximum. Concentrations exceeding 1000 mg/L nominal were not tested (see Table 2).

Based on measured inhibition rates, the 3-hour EC10, EC20 and EC50 and their 95% confidence limits were determined.

The results are listed below:

	EC10	EC20	EC50
Value [mg/l]	96.8	189.6	685.1
lower 95%-cl	24.2	77.5	476.7
upper 95%-cl	173.5	290.6	1176.0

Table 2. Influence of (3E)-dec-3-en-2 -one and the Reference Item 3,5-Dichlorophenol on Heterotrophic Oxygen Consumption of Activated Sludge

						pH - values (mean)1		Oxygen concentration (mean)1 (mg O2/L)
Flask No.	Treatment	Concentration (mg/L)	Oxygen consumption (mean)1 (%)	Coefficient of Varation (mean)1 (%)	Inhibition (mean)1 (%)	start*	end*	start*	end*
47, 48, 64, 65, 91, 92	control	-	16.30	18.70	-	7.6	8.5	9.1	9.1
49-53	3.5-DCP	3.2	10.80	-	33.7	7.8	8.5	9	9.6
54-58	3.5-DCP	10	9.12	-	44	7.8	8.4	9	10
59-63	3.5-DCP	32	4.20	-	74.2	7.8	8.3	9.1	9.3
66-70	Test item	10	21.96	-	-34.7	7.7	8.3	9.1	8.6
71-75	Test item	32	21.48	-	-36.8	7.3	8.4	9	8.6
76-80	Test item	100	15.24	-	6.5	7.3	8.4	9.2	89.4
81-85	Test item	320	10.44	-	36	7.3	8.4	9.1	9.2
86-90	Test item	1000	6.96	-	57.3	7.3	8.4	9.1	9.8

1) mean value of 5 replicates

* start and end of 3-hour aeration

- Oxygen Uptake due to nitrification

Based on measured inhibition rates, the 3-hour EC10, EC20 and EC50and their 95% confidence limits were determined.

The results are listed below:

	EC10	EC20	EC50
Value [mg/l]	51.4	63.2	93.7
lower 95%-cl	n.d.	n.d.	n.d.
upper 95%-cl	n.d.	n.d.	n.d.

n.d. not determinded

Validity criteria fulfilled:

yes

Conclusions:

An OECD 209 Activated sludge inhibition test (2010) was performed with (3E)-dec-3-en-2-one at nominal concentrations of 10, 32, 100, 320 and 1000 mg/L after a contact time of 3 hours.
For total respiration an EC50 of 236.6 mg/L, and a NOEC )= 32 mg/L were determined.

Executive summary:

To investigate potential harmful effects of (3E)-dec-3 -en-2 -one to microorganisms, an activated sludge respiration inhibition test was performed according to OECD 209 and under GLP. 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 respiration rate under defined conditions. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test item after an incubation period of 3 hours. The inhibitory effect of the test item at each concentration was expressed as percentage of the mean respiration rate of the controls. Additionally, the oxygen uptake by nitrification was evaluated in presence of an inhibitor, N-allythiourea (ATU).

The study was conducted to assess the inhibitory effect of the test item at concentrations of 10, 32, 100, 320 and 1000 mg test item/L (nominal) to microorganisms of activated sludge by measuring the respiration rate after adding a standard amount of synthetic sewage feed. In parallel to the study with the test item, the reference item 3,5-dichlorophenol was tested at the nominal test concentrations of 3.2, 10 and 32 mg/L (five replicates each test concentration) under otherwise identical test conditions.

Additionally, a nitrification inhibitor N-allylthiourea (ATU) was tested in the same way with six separate controls and at the identical nominal concentrations of the test item and also the reference item 3,5-dichlorophenol under otherwise identical test conditions.

The test met all guideline validity criteria. 

Result Synopsis

3-h EC10 = 42.1 mg/L [95% CI = 6.9 to 83.4]

3 -h EC50 for total respiration = 236.6 mg/L

3-h NOEC = 32 mg/L

Enpoint Effected: Total respiration

The results for the inhibition of the heterotropic respiration of activated sludge after the exposure period of 3 hours were:

3-h EC10 = 96.8 mg/L [ 95% CI = 24.2 to 173.5]

3-h NOEC = 32 mg/L (key value)

3- hour EC 50 for heterotrophic respiration = 685.1 mg/L

The results for the Oxygen Uptake due to Nitrification

3-h EC10 = 51.4 [ 95% CI = n.d.]

3- hour EC 50 for the O2 uptake = 93.7 mg/L

Description of key information

An OECD 209 Activated sludge inhibition test (2010) was performed with (3E)-dec-3-en-2-one at nominal concentrations of 10, 32, 100, 320 and 1000 mg/L after a contact time of 3 hours.

For total respiration an EC50 of 236.6 mg/L,  and a NOEC = 32 mg/L were determined.

Key value for chemical safety assessment

EC50 for microorganisms:

236.6 mg/L

EC10 or NOEC for microorganisms:

32 mg/L