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Sediment toxicity

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Reference
Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2nd February 2001 to 10th July 2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 219 (Sediment-Water Chironomid Toxicity Test Using Spiked Water)
Version / remarks:
(draft guidelines)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Details on sampling:
SEDIMENT
- Concentrations: all
- Sampling interval: 2 hours and 7 and 28 days after application

OVERLYING WATER
- Concentrations: replicates 1 and 2 from all concentrations
- Sampling interval: 2 hours and 3, 7, 14 and 28 days after application

VESSEL WASHINGS
- Concentrations: replicates 1 and 2 from all concentrations
- Sampling interval: 28 days after application
Vehicle:
yes
Details on sediment and application:
PREPARATION OF SPIKED WATER
- Details of spiking: applied just below the surface of the water column
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): ethanol
Test organisms (species):
Chironomus riparius
Details on test organisms:
TEST ORGANISM
- Source: in-house laboratory culture
- Breeding conditions/Handling of egg masses and larvae: egg masses were hatched under conditions similar to the test and larvae were transferred to vessels containing sediment and aqueous medium as used in the test. These were held in culture boxes containing space for emerged midges to swarm. Egg ropes produced were used for the test.
- Age of animals at beginning of exposure: freshly laid egg ropes were collected and transferred to fresh medium and hatched at test temperatures. The eggs began to hatch the next day and after a further 3 days (first instar), the larvae were transferred to the test vessels
- Feeding during test
- Food type: suspension of TetraMin® fish flake
- Amount: rate equivalent to 0.5 mg per larvae per day TetraMin®, increased to 1mg per day after the first 10 days
- Frequency: daily
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
Test temperature:
18-20.3 ºC
Dissolved oxygen:
50-98 % ASV
Nominal and measured concentrations:
0, 32, 100, 320, 1000 and 3200 µg/L
Details on test conditions:
TEST SYSTEM
- Test container (material, size): glass beakers of approximately 1 L capacity (double-housed in plastic 2 L capacity beakers for the radiolabelled test)
- Sediment depth: 2 cm
- Overlying water volume: 610 mL
- Depth of sediment and overlying water: 1:4
- Aeration: yes
- Replacement of evaporated test water, if any: as appropriate

EXPOSURE REGIME
- No. of organisms per container (treatment): 20
- No. of replicates per treatment group: 6
- No. of replicates per control / vehicle control: 6
- Type and preparation of food: suspension of TetraMin® fish flake
- Amount: rate equivalent to 0.5 mg per larvae per day TetraMin®, increased to 1mg per day after the first 10 days

OVERLYING WATER CHARACTERISTCS
- Type of water: Elendt M7 medium
- Conductivity: 0.63 mS

CHARACTERIZATION OF ARTIFICIAL SEDIMENT
- Composition: 10 % w/w sphagnum moss peat, 20 % w/w kaolin clay and 70% industrial sand
- Method of preparation: the three dry components were mixed with deionised water for 5 minutes
- Moisture: 79 %
- pH whole sediment: 6.0 ± 0.5

OTHER TEST CONDITIONS
- Photoperiod: 16 h light; 8 h dark

EFFECT PARAMETERS MEASURED:
- Emergence assessment: test vessels were checked daily and emerged insects knocked-down with CO2, removed, counted and sexed.

VEHICLE CONTROL PERFORMED: yes

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0, 0.1, 1, 10 and 100 µg/L
- Results used to determine the conditions for the definitive study: yes
Reference substance (positive control):
no
Key result
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
1 770 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
320 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
1 770 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: emergence ratio
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
1 000 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: emergence ratio
Key result
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
> 3 333 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
development rate
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
320 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
development rate
Details on results:
- No. of emerged male and female midges (per vessel and per day): > 80 % by day 28 in controls and treatment groups > 320 µg/L; 70 % emergence was recorded at 1000 µg/L; 3.75 % emergence was recorded at 3200 µg/L.
- Mean development rate of fully emerged midges: no treatment group showed a development ratio of < 50 % compared to the controls

Distribution of test material

Analysis of overlying water, sediment and interstitial water for radioactivity indicates that the applied test material was removed rapidly from the water phase and partitioned to the sediment phase. Losses from the overlying water increased with decreasing concentration with 16.8 to 27.3 % removal of radioactivity in the first 2 hours after dosing from the 1000 to 32 µg/L concentrations. The exception to this trend was the 33 % removal from the overlying water measured at 2 hours in the 3200 µg/L concentration. Losses from overlying water typically continued until day 7 by which time 79.3 to 88.9 % of applied radioactivity had been removed in the 32 to 3200 µg/L concentrations. By day 28, radioactivity levels in overlying water increased to 14.9 to 35.8 % of applied radioactivity. This may have been partly due to re-working of the sediment by test organisms but is also likely to have been due to degradation of the parent compound to more polar/soluble metabolites. Radioactivity in the interstitial water only constituted a minor fraction of the applied dose (<0.1, 0.16 to 0.27 and 0.55 to 2.0 % at 2 hours, day 7 and day 28, respectively). This indicates that the test material in the overlying water was adsorbed to the sediment phase although increased levels of radioactivity in the interstitial water by day 28 further supports the observation of the presence of radiolabeled degradation products. Radioactivity in the sediment phase rapidly increased after application of test material with 5.3 to 8.6 % of applied radioactivity in the sediment of the 32 to 1000 µg/L vessels at 2 hours and 17.1 % in the 3200 µg/L sediment at 2 hours. By day 28, mean sediment percentages of applied radioactivity were 36.7 to 61 %. This increase was generally proportional to concentration. Acetone washes of test vessels showed binding of propargite to be 2.4 to 7.1 % of applied levels.

Table 1: Total emergence and percent mean cumulative emergence

 Propargite concentration (µg equivalents/L)
 Total emergence  Control  Solvent control  32  100  320  1000  3200
 Day 15  0  3  5  0  0  0
 % mean cumulative emergence  7.5  0  3.75  6.25  0  0  0
 Day 16  23  26  38  35  16  0  0
 % mean cumulative emergence  28.75  32.5  51.25  50  20  0  0
 Day 17  52  51  63  56  40  6  0
 % mean cumulative emergence  65  63.75  78.75  70  50  7.5  0
 Day 18  71  68  72  60  62  10  0
 % mean cumulative emergence  88.75  85  90  75  77.5  12.5  0
 Day 19  75  71  75  65  69  27  0
 % mean cumulative emergence  93.75  88.75  93.75  81.25  86.25  33.75  0
 Day 20  75  71  77  67  73  41  0
 % mean cumulative emergence  93.75  88.75  96.25  83.75  91.25  51.25  0
 Day 21  75  71  77  67  73  48  0
 % mean cumulative emergence  93.75  88.75  96.25  83.75  91.25  60  0
 Day 22  75  72  77  67  73  52  0
 % mean cumulative emergence  9375  90  96.25  83.75  91.25  65  0
 Day 23  75  72  77  67  73  54  0
 % mean cumulative emergence  93.75  90  96.25  83.75  91.25  67.5  0
 Day 24  75  72  77  67  73  56  0
 % mean cumulative emergence  93.75  90  96.25  83.75  91.5  70  0
 Day 25 75  72  77  67  73  56  0
 % mean cumulative emergence 93.75   90  96.25 83.75  91.5   70  0
 Day 26 75  72  77  67  73  56  1
 % mean cumulative emergence 93.75   90  96.25  83.75  91.5 70  1.25
 Day 27  75 72  77  67  73  56  1
 % mean cumulative emergence  93.75  90 96.25   83.75  91.5  70  1.25
 Day 28 75   72 77   67  73  56  3
 % mean cumulative emergence  93.75  90 96.25   83.75  91.5  70  3.75

Table 2: Emergence of male and female midges: total in four replicates

 

 Number of emerged male and female midges

 
Conc (µg equivalent/L) day 15 day 16 day 17 day 18 day 19 day 20 day 21 day 22 day 23 day 24 day 25 day 26 day 27 day 28 Total number of emerged midges
32 -/3M 9F/26M 20F/5M 9F/- 3F/- 2F/- -/- -/- -/- -/- -/- -/- -/- -/- 43F/34M
100 1F/4M 11F/19M 13F/8M 4F/- 5F/- 2F/- -/- -/- -/- -/- -/- -/- -/- -/- 36F/31M
320 -/- 2F/14M 6F/18M 18F/4M 7F/- 4F/- -/- -/- -/- -/- -/- -/- -/- -/- 37F/36M
1000 -/- -/- -/6M -/4M 10F/7M 10F/4M 5F/2M 4F/- 2F/- 2F/- -/- -/- -/- -/-  33F/23M
3200 -/- -/- -/- -/- -/- -/- -/- -/- -/- -/- -/- -/1M -/- -/2M -/3M
Solvent control -/- 5F/21M 17F/8M 16F/1M 3F/- -/- -/- 1F/- -/- -/- -/- -/- -/- -/- 42F/30M
Control  -/6M -/17M 17F/12M 17F/2M 4F/- -/- -/- -/- -/- -/- -/- -/- -/- -/- 38F/37M

Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the test, the 28 day EC50 for emergence (survival) was 1700 µg/L as initially applied 14C-propargite equivalents; the corresponding NOEC was 320 µg/L as 14C-propargite equivalents. The same NOEC applies for rate of emergence (larval development rate) with an EC50 of > 3200 µg/L 14C-propargite equivalents. Analysis of overlying water, sediment and interstitial water for radioactivity indicates that the applied propargite was rapidly removed from water phase and partitioned to the sediment phase.
Executive summary:

The study was designed to determine the EC50 and NOEC of [14C]-propargite to the sediment dwelling life stage of Chironomus riparius. The study was performed in line with the draft version of the standardised guideline OECD 219.

Following a preliminary range finding study with non-labelled material, test concentrations for the definitive test were selected as 32, 100, 320, 1000 and 3200 µg/L. The test was conducted under static conditions with propargite added to the water column of a sediment water system containing first instar larvae of Chironomous. Radiolabelled test material was used so that the partitioning behaviour of the test material in the two-phase test system (sediment: water) could be observed over the duration of the study.

Chironomid midges emerged from test vessels from day 15 after application to the end of the test. Emergence in the two control treatments and the 32 to 320 µg/L groups was over 80 % and a majority of the midges had emerged by day 20 in these groups. Emergence in the 1000 µg/L group was 70 % by the end of the test. In the 3200 µg/L group, only 3 midges were observed and these did not begin to emerge until 26 days after application.

The EC50 for mortality of developing larvae and the emergence ratio (male to female) was 1770 µg equivalents/L. Effects on development rate did not span 50 % for the treatment levels tested. The statistically derived NOEC for larvae mortality and the midge development rate was 320 µg equivalents/L whereas it was 1000 µg equivalents/L for the emergence ratio. As only total radioactivity was monitored, the results of the study are reported as µg equivalents of the test material.

The majority of the [14C]-propargite was found in the overlying water or the sediment fraction by the end of the study. The largest fraction (36.7 to 61 % of the [14C]-propargite applied) was associated with the sediment. However, minimal concentrations detected in the overlying water were recorded at days 7 and 14. The radioactivity associated with [14C]-propargite appeared to be redistributing back to the overlying water by the end of the test. Compared to the minimum values, detected means of 4 to 15 % of the applied [14C]-propargite had returned to the overlying water by the end of the test. Total percent recovery of the radiolabeled material from all fractions ranged from 72.3 to 85.8 % of the applied [14C]-propargite. At the end of the test, 0.55 to 2 % of the radioactivity applied was associated with interstitial water. Acetone washings of the exposure vessels accounted for 2.4 to 7.1 % of the applied radioactivity.

Description of key information

Emergence (survival) EC50 1700 µg/L 14C-propargite equivalents, NOEC 320 µg/L 14C-propargite equivalents; study conducted in accordance with OECD Guideline 219 (draft version); Kelly and Allan, 2002

Key value for chemical safety assessment

Additional information

Following a preliminary range finding study with non-labelled material, test concentrations for the definitive test were selected as 32, 100, 320, 1000 and 3200 µg/L. The test was conducted under static conditions with propargite added to the water column of a sediment water system containing first instar larvae of Chironomous. Radiolabelled test material was used so that the partitioning behaviour of the test material in the two-phase test system (sediment: water) could be observed over the duration of the study.

Chironomid midges emerged from test vessels from day 15 after application to the end of the test. Emergence in the two control treatments and the 32 to 320 µg/L groups was over 80 % and a majority of the midges had emerged by day 20 in these groups. Emergence in the 1000 µg/L group was 70 % by the end of the test. In the 3200 µg/L group, only 3 midges were observed and these did not begin to emerge until 26 days after application.

The EC50 for mortality of developing larvae and the emergence ratio (male to female) was 1770 µg equivalents/L. Effects on development rate did not span 50 % for the treatment levels tested. The statistically derived NOEC for larvae mortality and the midge development rate was 320 µg equivalents/L whereas it was 1000 µg equivalents/L for the emergence ratio. As only total radioactivity was monitored, the results of the study are reported as µg equivalents of the test material.

The majority of the [14C]-propargite was found in the overlying water or the sediment fraction by the end of the study. The largest fraction (36.7 to 61 of the [14C]-propargite applied) was associated with the sediment. However, minimal concentrations detected in the overlying water were recorded at days 7 and 14. The radioactivity associated with [14C]-propargite appeared to be redistributing back to the overlying water by the end of the test. Compared to the minimum values, detected means of 4 to 15 % of the applied [14C]-propargite had returned to the overlying water by the end of the test. Total percent recovery of the radiolabeled material from all fractions ranged from 72.3 to 85.8 % of the applied [14C]-propargite. At the end of the test, 0.55 to 2 % of the radioactivity applied was associated with interstitial water. Acetone washings of the exposure vessels accounted for 2.4 to 7.1 % of the applied radioactivity.

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