cyproconazole (ISO); (2RS,3RS;2RS,3SR)-2-(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

6 Oct 1998 to 9 Jan 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)

Version / remarks:

Proposal, May 1998

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: BBA guideline: Effects of Plant Protection Products on the Development of Sediment-Dwelling Larvae of Chironomus riparius in a Water-Sediment System

Version / remarks:

Porposal 1995

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Aqueous samples: Samples of an appropriate volume of the aqueous test solution, i.e. 30 mL samples from each beaker per concentration and the control were taken from the center of the test vessels at day 0, 3, 7, 14, 28 and 0, 2, 7, 14, 28 for exposure scenarios A and B respectively. These samples were analyzed and the concentration of the test substance measured.

- Sediment samples: At the beginning, after 7 days and at the end of the experiment, the concentration of the test substance in the sediment was measured in test vessels with the highest test concentrations and the lower one, i.e. at dose levels 10, 20 mg/Land 100, 200 mg/kg dry sediment for exposure scenarios A and B, respectively. To monitor changes in sediment or interstitial water chemistry during the course of the experiment, separate sediment chemistry chambers were set up and sampled at the start and after 7 days of the experiment.

Vehicle:

yes

Remarks:

For the application in sediment

Details on sediment and application:

PREPARATION ON STOCK SOLUTION AND THE FINAL TEST SOLUTIONS
- Water: 226.8 mg test substance were mixed and made up to 200 mL with reconstituted water (M4 Medium) to prepare stock solution 1. Stock solutions 2 - 6 were prepared by mixing appropriate stock solution 1 and making up to 100 mL with M4 Medium at test day 0 of exposure. The final test solutions were prepared by adding 10 mL of these stock solutions into the test chamber containing 567 mL M4-medium.

- Sediment: 8.3615 g test substance were mixed and made up to 100 mL with acetone to prepare SL 1. 5.0 mL of this stock solution were mixed and made up to 10 mL with acetone to prepare SL 2. 2.5 mL of this stock solution were mixed and made up to 10 mL with acetone to prepare SL 3. 1.25 mL of this stock solution were mixed and made up to 10 mL with acetone to prepare SL 4. 0.625 mL of this stock solution were mixed and made up to 10 mL with acetone to prepare SL 5.
After evaporation of the acetone the dry sand was added to the aged sediment (1100 g sediment equivalent to 819.8 g dry sediment) to achieve the planned test concentrations and thoroughly mixed with a Mixer for about 30 minutes.

CONTROLS
- Water: 10 mL culture medium (M4) was added at test initiation.
- Sediment: Aged Sediment with acetone and without acetone treated sand were used as controls.

APPLICATION IN WATER
The application of the test substance was carried out one day after adding the larvae. The stock solutions were added to the water column of the test vessels below the water surface by using a pipette and gently mixing the upper water layer to ensure homogeneous distribution without disturbing the sediment. Gentle aeration was provided through a glass pipette situated about 2 to 3 cm above the sediment.

APPLICATION IN SEDIMENT
The artificial sediment was conditioned for 7 days in flowing water prior to spiking. 1 L glass beakers (tall form, 9 cm diameter) were filled with a layer of 1.6 cm of artificial sediment (sediment spiked with test substance, sediment mixed with sand treated with acetone (vehicle control) or untreated sediment for control) corresponding to 160 g sediment (moist weight); The sediment was overlaid with reconstituted water of a height of approximately 8 cm. Separation of the sediment ingredients when adding the test water, was avoided by covering the sediment with a styropor plate, before pouring the test water (500 g) into the beakers. The plate was carefully removed thereafter.

Test organisms (species):

Chironomus riparius

Details on test organisms:

TEST ORGANISM
- Age of animals at beginning of exposure: 1st instar larvae, 2 - 3 days old
- Handling of Chironomus larvae used in the test: The 1st instar larvae used in this study are obtained by transferring fresh egg masses to small crystallising dishes with culture medium (M4-medium). After 2 - 3 days the larvae have hatched and are transferred to the test beakers.
- Feeding during test: A commercially available fishfood is used as food. 1 g fishfood is ground finely and suspended in 20 mL water. From this stock a certain amount is added to the test vessel in order to provide each larvae with about 1 mg food per day during the course of the experiment.

CULTIVATION
- Culture condition: Chironomus larvae were reared in crystallising dishes spread at the bottom with a thin layer of Kieselgur of about 1 - 2 cm depth and covered with M4 medium to a weight of about 6 cm. The rearing vessels were kept in a suitable cage to prevent escape of emerging adults.
- Temperature: 20 ± 2 °C
- Photoperiod: 16 hours light and 8 hours dark (transition period 30 mins)
- Relative air humidity: 60 - 90%
- Aeration: Gentle aeration was provided throughout the culture period.
- Feeding: The Chironomus larvae were fed with a fish flake food. Some green algae (Scenedesmus subspicatus) were added when new culture vessels are set up and sometimes throughout culturing.
- Handling: Once adults were present within the breeding cage, all larvae rearing vessels were checked 3 times a week for deposition of the gelatinous egg masses. If present, the egg packages will be removed carefully and used to start new rearing vessels or for toxicity tests.

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Duration:

28 d

Exposure phase:

total exposure duration

Hardness:

- Exposure scenario A (water): 234 - 251 mg/L as CaCO3
- Exposure scenario B (sediment): 249 - 257 mg/L as CaCO3

Test temperature:

20 ± 2 °C

pH:

Test initiation:
- Exposure scenario A (water): 7.7 - 7.9
- Exposure scenario B (sediment): 8.0 - 8.1

Test termination:
- Exposure scenario A (water): 8.3 - 8.9
- Exposure scenario B (sediment): 7.9 - 9.0

Dissolved oxygen:

Test initiation:
- Exposure scenario A (water): 7.9 - 11.6 mg O2/L
- Exposure scenario B (sediment): 7.5 - 8.0 mg O2/L

Test termination:
- Exposure scenario A (water): 7 .7 - 9.2 mg O2/L
- Exposure scenario B (sediment): 5.8 - 8.8 mg O2/L

Conductivity:

- Exposure scenario A (water): 671 - 682 μS/cm
- Exposure scenario B (sediment): 658 - 688 μS/cm

Nominal and measured concentrations:

Nominal concentrations:
- Exposure scenario A (water): 0 (negative control), 0.63, 1.25, 2.5, 5.0, 10 and 20 mg/L
- Exposure scenario B (sediment): 0 (negative control), 0 (solvent control),12.5, 25, 50, 100 and 200 mg/kg dry sediment

Details on test conditions:

TEST SYSTEM
(Exposure scenario A; Water)
- Test container: 1 L glass beakers (tall form, 9 cm diameter)
- Type: The test beakers were covered with parafilm with small holes to reduce evaporation throughout the test and to allow collection of emerged midges.
- Sediment volume: A layer of 1 - 2 cm of artificial sediment
- Weight of wet sediment (moist weight): 120 g
- Overlying water weight: 540 g
- Depth of sediment and overlying water:
Approximately 8 cm
- No. of organisms per container: 20 (Allocated randomly to each test vessel with a blunt pipette 1 day before treatment)
- Aeration: Yes (Gentle aeration was provided through a glass pipette situated about 2 - 3 cm above the sediment layer. After addition of the larvae, aeration was stopped for the following 24 hours.)
- Other: The test beakers were prepared 13 days before the start of the test substance application to allow stabilisation of the systems under test conditions.

TEST SYSTEM (Exposure scenario B; Sediment)
- Test container: 1 L glass beakers (tall form, 9 cm diameter)
- Type: The test beakers were covered with parafilm with small holes to reduce evaporation throughout the test and to allow collection of emerged midges.
- Sediment volume: A layer of 1.6 cm of artificial sediment (sediment spiked with test substance, sediment mixed with sand treated with
acetone (vehicle control) or untreated sediment for control)
- Weight of wet sediment (moist weight): 160 g
- Overlying water weight: 500 g
- Depth of sediment and overlying water: Approximately 8 cm
- No. of organisms per container: 20
- Aeration: A gentle aeration was carried out for 1 hour before start of exposure. After addition of the larvae aeration was stopped for the following 24 hours. Following gentle aeration was provided through a glass pipette situated about 2 to 3 cm above the sediment.
- Other: The test beakers were prepared 48 hours before the start of the test substance application.

OVERLYING WATER CHARACTERISTCS (Exposure scenario A and B)
- Type of water: M4 medium was used according to Guideline recommendations. The water column had a depth of about 8 cm (at the end of exposure 6 cm).

CHARACTERISATION OF ARTIFICIAL SEDIMENT (Exposure scenario A and B)
- Peat: 5.5 %
- Kaolin clay: 20%
- Industrial sand : 75% (fine sand with more than 50% of the particles between 50 and 200 microns)
- pH adjustment: Yes, by adding chemically pure calcium carbonate
- Organic carbon: 1.7%

EXPOSURE REGIME
(Exposure scenario A and B)
- No. of replicates per treatment group: 3
- No. of replicates per control / vehicle control: 3

OTHER TEST CONDITIONS (Exposure scenario A and B)
- Photoperiod: 16h : 8h (light:dark-rhythm)
- Light intensity: 800 lux (corresponding to about 75 μE/m2 sec)

WATER PARAMETERS (Exposure scenario A and B)
- Temperature: The water temperature was continuously measured in the test room and in a test vessel at different days.
- Oxygen and pH: Oxygen content and pH were measured once weekly with appropriate electrodes directly in the test vessels.
- Conductivity: The water conductivity and the water hardness were measured after preparing the 4-medium.

EFFECT PARAMETERS MEASURED (Exposure scenario A and B)
- Biological Observations: Visual assessments (behaviour, mortalities, emergence) were made daily (except for test days 2, 4, 5, 9, 11, 12, 19, 25, and 26 for exposure scenario A and 3, 4, 6, 8, 10, 11, 18, 24 and 25 for exposure scenario B). The number, time and sex of emerged adults was recorded. Afterwards adults were removed from the test vessels. The weight of larvae incubated for 9 days under exposure scenario A and B was measured after sieving the sediment from each test beaker using a 250 μm sieve. The dry weight of the larvae was measured after drying at 60 °C to a constant weight.

- Biological Endpoints: The following parameters were measured and considered relevant endpoints:
• rate of emergence, i.e. the sum of midges emerged per replicate divided by the number of larvae introduced
• Mean development time, i.e. the mean time between the application of the test substance (day 0, method A) or the addition of larvae (day 0, method B) and the emergence of adults
• Rate of development, i.e. the portion of larval development per day which is calculated from the reciprocal of development time.

RANGE FINDING STUDY
- Test concentrations:
Exposure scenario A: 1.0, 10 and 100 mg/L; Exposure scenario B: 1.0, 10 and 100 mg/kg dry sediment

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

development rate

Remarks on result:

other: Exposure scenario A: Water-spiked

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

50 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: emergence rate and development rate

Remarks on result:

other: Exposure scenario B: Sediment-spiked

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

emergence rate

Remarks on result:

other: Exposure scenario A: Water-spiked

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

10.6 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

emergence rate

Remarks on result:

other: Exposure scenario A: Water-spiked

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

16.4 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

development rate

Remarks on result:

other: Exposure scenario A: Water-spiked

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

88 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

emergence rate

Remarks on result:

other: Exposure scenario B: Sediment-spiked

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

10 386 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

development rate

Remarks on result:

other: Exposure scenario B: Sediment-spiked

Details on results:

An overview of the results is provided in Table 5 - Table 6 in 'Any other information on results incl. tables'.

BIOLOGICAL OBSERVATIONS
- Effects on the Rate of Emergence, the Development Time and the Development Rate: There were no indications on different sensitivities of sexes, therefore male and female results werepooled for statistical analyses.
Calculations of effects on the rate of emergence, the development time and development rate (reciprocal of the development time) were done by using a regression approach. All calculations
were based on nominal concentrations in the water phase for exposure scenario A and based on
nominal concentrations in the sediment for exposure scenario B. For exposure scenario A, the NOEC values for Emergence rate and development rate were 10 and 5 mg/L, respectively. For exposure scenario B, the NOEC values were 50 mg/kg for both emergence rate and development rate.

WEIGHT OF LARVAE
- Exposure scenario A: After 9 days of exposure 20, 19, 20, 20, 13, 19 and 6 larvae could be found at blank and at test concentrations of 0.63, 1.25, 2.5, 5.0, 10 and 20 mg/L. The corresponding average weight of the test groups were 1.15, 1.08, 1.11, 1.02, 0.88, 0.34 and 0.02 mg/larvae. A clear influence of the test substance to the weight of the larvae could be seen at test concentrations of 10 and 20 mg/L.
- Exposure scenario B: After 9 days of exposure 19, 18, 19, 20, 20, 17 and 19 larvae could be found at blank, vehicle and test concentrations of 12.5, 25, 50, 100 and 200 mg/kg sediment (dry weight). The corresponding average weight of the test groups were 0.695, 0.611, 0.637, 0.50, 0.465, 0.33 and 0.637 mg/larvae. No influence of the test substance to the weight of the larvae could be seen at the tested concentrations.

Reported statistics and error estimates:

ER and GR are transformed prior to statistical analysis, using an arcsine-squareroot transform. Dunnett tests (a= 5%) for these three parameters are performed to calculate NOEC and LOEC. ECx and 95%-confidence limits are calculated by logit analysis for emergence rate and development rate.

Table 5. Sum of Larvae, rate of emergence (ER), gender rate (GR) and development rate (X), (Exposure scenario A)

Nr.	Group (mg/L)	NE	NMALE	ER	GE	X
1	Blank	18	9	0.90	0.50000	0.066767
2	Blank	20	15	1.00	0.75000	0.716190
3	Blank	16	8	0.80	0.50000	0.067860
4	0.63	20	9	1.00	0.45000	0.063982
5	0.63	20	12	1.00	0.60000	0.068546
6	0.63	20	10	1.00	0.50000	0.066709
7	1.25	19	8	0.95	0.42105	0.066403
8	1.25	20	9	1.00	0.45000	0.069229
9	1.25	19	9	0.95	0.47368	0.069163
10	2.5	20	7	1.00	0.35000	0.066025
11	2.5	17	6	1.00	0.35294	0.068796
12	2.5	20	11	1.00	0.55000	0.068811
13	5	20	14	1.00	0.70000	0.068175
14	5	20	6	1.00	0.30000	0.065207
15	5	18	8	1.00	0.44444	0.067538
16	10	17	11	0.85	0.64706	0.059899
17	10	19	10	0.95	0.52632	0.059317
18	10	13	4	0.65	0.30769	0.055910
19	20	0	0	0	-	-
20	20	0	0	0	-	-
21	20	0	0	0	-	-

NE: Sum of midges emerged per vessel

ER: Emergence Rate

GR: Gender Rate

Table 6. Sum of Larvae, rate of emergence (ER), gender rate (GR) and development rate (X), (Exposure scenario B)

Nr.	Group (mg/kg)	NE	NMALE	ER	GE	X
1	Blank	13	7	0.65	0.53846	0.065325
2	Blank	18	9	0.90	0.50000	0.060452
3	Blank	20	9	1.00	0.45000	0.060957
4	Viecle	16	6	0.80	0.37500	0.059681
5	Viecle	19	11	0.95	0.57895	0.063721
6	Viecle	16	9	0.80	0.56250	0.058110
7	12.5	28	17	0.85	0.47059	0.061325
8	12.5	18	11	0.90	0.61111	0.063055
9	12.5	16	9	0.80	0.56250	0.061469
10	25	15	6	0.75	0.40000	0.060639
11	25	16	11	0.80	0.68750	0.061054
12	25	16	7	0.80	0.43750	0.061614
13	50	15	7	0.75	0.46667	0.060117
14	50	18	7	0.90	0.38889	0.057800
15	50	17	9	0.85	0.52941	0.059974
16	100	4	0	0.20	0.00000	0.054487
17	100	6	4	0.30	0.66667	0.054973
18	100	3	2	0.15	0.66667	0.054131
19	200	0	0	0.00	-	-
20	200	1	1	0.05	1.00000	0.060606
21	200	0	0	0.00	-	-

NE: Sum of midges emerged per vessel

ER: Emergence Rate

GR: Gender Rate

X: Mean of development rate per vessel

 

X: Mean of development rate per vessel

Validity criteria fulfilled:

yes

Remarks:

Since emergence in the controls was greater than 80% and the mean development time for the larvae in exposure scenarios A and B was not later than 23 days after application, the validity of these tests are confirmed.

Conclusions:

The water-spiked EC50 values were 10.6 (emergence rate) and 16.4 mg/L (development rate) for organisms exposed to the test substance via spiking of the water column. The corresponding NOEC values were 10 (emergence rate) and 5.0 mg/L (development rate), respectively. The sediment-spiked EC50 values were 88.0 mg/kg sediment dw (emergence rate) and 10386 mg/kg sediment dw (development rate) for organisms exposed to the test substance via spiking of the sediment. The corresponding NOEC values were 50 mg/kg for emergence rate and development rate, respectively.

Executive summary:

The impact of the test substance on the emergence and development of the sediment-dwelling organism Chironomus riparius was studied under static conditions according OECD guideline proposal for toxicity test with Chironomidae and the proposal of BBA guideline (Effects of Plant Protection Products on the Development of Sediment-Dwelling Larvae of Chironomus riparius in a Water-Sediment System). The study was in compliance with GLP criteria.

In this study, first instar midge larvae (2 - 3 days old; 20 per test vessel) were exposed under static conditions to a series of test concentrations for 28 days. The test vessels contained approximately 1.5 cm artificial sediment and 8 cm height water column (at test terminated 6 cm height). The tests were performed at 20 ± 2 °C with a 16/8 light/dark cycle (30-minute transition period; 800 lux) and gentle aeration of the water layer using a glass Pasteur pipette (oxygen content 5.8 to 11.6 mg/L in the course of the test). The main parameters examined were the rate and time of emergence and the total number of fully emerged male and female midges. 

Two exposure scenarios were included in the study:

Exposure scenarios A: The test substance was applied to the water column of the system at nominal concentrations of 0.63, 1.25, 2.5, 5.0, 10 and 20 mg/L. After 9 days of exposure, 20, 19, 20, 20, 13, 19 and 6 larvae could be found at blank and at test concentrations of 0.63, 1.25, 2.5, 5.0, 10 and 20 mg/L, respectively. The corresponding average weight of the test groups were 1.15, 1.08, 1.11, 1.02, 0.88, 0.34 and 0.02 mg/larvae. A clear influence of the test substance to the weight of the larvae could be seen at test concentrations of 10 and 20 mg/L.

Exposure scenarios B: The test substance was mixed with the artificial sediment to prepare nominal concentrations of 12.5, 25, 50, 100, 200 mg/kg sediment (dry weight). There were no indications of a difference in sensitivity to the test substance between the sexes. After 9 days of exposure 19, 18, 19, 20, 20, 17 and 19 larvae could be found at blank, vehicle and test concentrations of 12.5, 25, 50, 100 and 200 mg/kg sediment (dry weight), respectively. The corresponding average weight of the test groups were 0.695, 0.611, 0.637, 0.50, 0.465, 0.33 and 0.637 mg/larvae. No influence of the test substance to the weight of the larvae could be seen at the tested concentrations.

Based on the findings, the water-spiked (Exposure scenario A) EC50 values for emergence rate and development rate were determined to be 10.6 and 16.4 mg/L, respectively. The corresponding NOEC values were 10 and 5.0 mg/L for emergence rate and development rate, respectively. The sediment-spiked (Exposure scenario B) EC50 values for emergence rate and development rate were 88.0 and 10386 mg/kg sediment (dry weight), respectively. The corresponding NOEC values was 50 mg/kg for emergence rate and development rate. As sediment-spiked data is recommended, this NOEC of 50 mg/kg sediment dry weight will be used as key value in the chemical safety assessment.

Description of key information

28-d NOEC = 50 mg a.i./kg sediment dry weight, sediment-spiked exposure, Chironomus riparius, development of larvae, BBA guideline proposal and OECD TH proposal, Grade 1999

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

50 mg/kg sediment dw

Additional information

The impact of the test substance on the emergence and development of the sediment-dwelling organism Chironomus riparius was studied under static conditions according OECD guideline proposal for toxicity test with Chironomidae and the proposal of BBA guideline (Effects of Plant Protection Products on the Development of Sediment-Dwelling Larvae of Chironomus riparius in a Water-Sediment System). The study was in compliance with GLP criteria.

In this study, first instar midge larvae (2 - 3 days old; 20 per test vessel) were exposed under static conditions to a series of test concentrations for 28 days. The test vessels contained approximately 1.5 cm artificial sediment and 8 cm height water column (at test terminated 6 cm height). The tests were performed at 20 ± 2 °C with a 16/8 light/dark cycle (30-minute transition period; 800 lux) and gentle aeration of the water layer using a glass Pasteur pipette (oxygen content 5.8 to 11.6 mg/L in the course of the test). The main parameters examined were the rate and time of emergence and the total number of fully emerged male and female midges. 

Two exposure scenarios were included in the study:

Exposure scenarios A: The test substance was applied to the water column of the system at nominal concentrations of 0.63, 1.25, 2.5, 5.0, 10 and 20 mg/L. After 9 days of exposure, 20, 19, 20, 20, 13, 19 and 6 larvae could be found at blank and at test concentrations of 0.63, 1.25, 2.5, 5.0, 10 and 20 mg/L, respectively. The corresponding average weight of the test groups were 1.15, 1.08, 1.11, 1.02, 0.88, 0.34 and 0.02 mg/larvae. A clear influence of the test substance to the weight of the larvae could be seen at test concentrations of 10 and 20 mg/L.

Exposure scenarios B: The test substance was mixed with the artificial sediment to prepare nominal concentrations of 12.5, 25, 50, 100, 200 mg/kg sediment (dry weight). There were no indications of a difference in sensitivity to the test substance between the sexes. After 9 days of exposure 19, 18, 19, 20, 20, 17 and 19 larvae could be found at blank, vehicle and test concentrations of 12.5, 25, 50, 100 and 200 mg/kg sediment (dry weight), respectively. The corresponding average weight of the test groups were 0.695, 0.611, 0.637, 0.50, 0.465, 0.33 and 0.637 mg/larvae. No influence of the test substance to the weight of the larvae could be seen at the tested concentrations.

Based on the findings, the water-spiked (Exposure scenario A) EC50 values for emergence rate and development rate were determined to be 10.6 and 16.4 mg/L, respectively. The corresponding NOEC values were 10 and 5.0 mg/L for emergence rate and development rate, respectively. The sediment-spiked (Exposure scenario B) EC50 values for emergence rate and development rate were 88.0 and 10386 mg/kg sediment (dry weight), respectively. The corresponding NOEC values was 50 mg/kg for emergence rate and development rate. As sediment-spiked data is recommended, this NOEC of 50 mg/kg sediment dry weight will be used as key value in the chemical safety assessment.