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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
SEDIMENT
- Concentrations: 0 and 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)
- Sampling interval: Days 0 and 28. In addition samples were taken on day -2 to confirm correct dosing of the system.
- Sample storage before analysis: Duplicate samples were taken and stored at approximately - 20ºC for fruther analysis if neccessary


PORE WATER
- Concentrations: 0 and 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)
- Sampling interval: Days 0 and 28.
- Sample storage before analysis: Duplicate samples were taken and stored at approximately - 20ºC for fruther analysis if neccessary


OVERLYING WATER
- Concentrations: 0 and 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)
- Sampling interval: Days 0 and 28
- Sample storage before analysis: Duplicate samples were taken and stored at approximately - 20ºC for further analysis if neccessary
Test organisms (species):
Chironomus sp.
Details on test organisms:
TEST ORGANISM
- Common name: Chironomus riparius
- Source: In-house laboratory cultures
- Handling of egg masses and larvae: Any gelatinous egg masses produced by breeding adult midges were removed from the culture vessels and transferred to separate vessels and, if required, larvae used to populate new cultures at an initial density of between 100 and 200 larvae.
- Age of animals at beginning of exposure: 2-3 days old
- Feeding during test
- Food type: Tetramin flake food
- Amount: 0.5 mg / larva / day
- Frequency: Daily


Study type:
laboratory study
Test type:
static
Type of sediment:
artificial sediment
Duration:
28 d
Exposure phase:
total exposure duration
Hardness:
The water hardness values for the control were determined to be 296 and 360 mg/l as CaCO3 on days 0 and 28 respectively, and 316 and 322 mg/l as CaCO3 for the 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment) test group on days 0 and 28 respectively.
Test temperature:
Temperature was maintained at 20.6ºC to 22.3ºC (refer to attached document for individual measurements taken throughout the test)
pH:
Refer to attached document for individual measurements taken throughout the test
Dissolved oxygen:
Refer to attached document for individual measurements taken throughout the test
Ammonia:
Ammonia concentrations were determined to be 0.054 and 0.0066 mg/l as NH3 for the control on days 0 and 28 respectievly and 0.022 and 0.0079 mg/l as NH3 for the 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment) test group on days 0 and 28 respectively.
Nominal and measured concentrations:
1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight sediment)
Details on test conditions:
TEST SYSTEM
- Test container (material, size): 600 mL glass beaker
- Overlying water volume: 8 cm
- Depth of sediment: 2 cm
- Aeration: yes
- Aeration frequency and intensity: Test vessels aerated 1 bubble/second approximately 2-3 cm above the sediment layer and the veseels left for 2 days prior to addition of the test organisms. Aeration was switched back on after ~ 24h having allowed the larvae to settle in the sediment.


EXPOSURE REGIME
- No. of organisms per container (treatment): 20 larva/ vessel
- No. of replicates per treatment group: 6 replicates. A further 40 larvae (two vessels of 20 larvae) of each test group were preapred and sacrificed on day 10 of the exposure period to determine the 10 day larval survival and growth data.
- No. of replicates per control / vehicle control: 6 replicates
- Feeding regime:
- Type of food: Tetramin flake food
- Amount of food: Larvae were fed at a rate of 0.25 mg Tetramin flake food per larva per day for the first 10 days and 0.5 mg Tetramin flake food per larva per day thereafter



OVERLYING WATER CHARACTERISTCS
- Type of water: Elendt medium acc. to OECD 219):


CHARACTERIZATION OF (ARTIFICIAL SEDIMENT)
- Particle size distribution
- % Industrial quartz sand: 76
- % Sphagnum moss peat: 4
- % Kaolinite clay: 20
- Further constituents
- Organic carbon: 1.6%
- Total organic carbon (%): 1.6


OTHER TEST CONDITIONS
- Photoperiod: 16 hour light/8 hour darkness
- Light intensity: 302 - 333 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Emergence of live adult midges. THe number of emerged adult midges was recorded daily until termination of the study after 28 days.


VEHICLE CONTROL PERFORMED: no


TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 10, 100 and 1000 mg test material/kg dry weight of sediment (equivalent to 7.56, 75.6 and 756 mg cyanuric acid/kg dry weight
- Results used to determine the conditions for the definitive study: Based on the results of the range finding test a limit test was conducted for the definitive study at a test concentration of 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight)
Reference substance (positive control):
no
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg sediment dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
emergence rate
Remarks on result:
other: equivalent to 756 mg cyanuric acid/kg dry weight sediment
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/kg sediment dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
emergence rate
Remarks on result:
other: Equivalent to 756 mg cyanuric acid/kg dry weight of sediment
Details on results:
- No. of surviving larvae on day 10: See table 1
- No. of pupae failing to emerge: 0
- Adult emergence data after 28 days: See table 2
- Mean development rate of fully emerged midges: See table 3
- Mean individual dry weight of larvae (per larvae and per instar): See table 4
Reported statistics and error estimates:
Statistical analysis of the day 10 larval weights was performed using the Student’s T-test incorporating Bartlett’s test for homogeneity of variance (Sokal and Rohlf 1981) for the control and 1000 mg/kg test group. Statistical analysis of the emergence data was performed using the Student’s T-test. All statistical analyses were performed using the SAS computer software package (SAS 1999 – 2001). Analysis was performed on the emergence ratio (ER) values.

Table 1: No of surviving larvae on day 10

Nominal concentration

(mg/kg)*

Number of larvae

Live larvae

Dead larvae

Larvae unaccounted for

Control R7

20

0

0

Control R8

19

0

1

1000 R7

19

0

1

1000 R8

20

0

0

* mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)

R7-R8 = replicates 7 and 8 prepared at the start of the study for sacrifice on day 10.

Table 2: Adult emergence data after 28 days

Replicate

Number of fully emerged midges (out of 20/vessel)

Control

1000 mg/kg*

R1

20

21

R2

20

18

R3

15

19

R4

16

20

R5

22

20

R6

18

20

* mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)

R1-R6 = replicates 1 to 6 (replicates 7 and 8 in both groups were sacrificed at 10 days)

Table 3: Mean development rates

Nominal concentration* (mg/kg)

Mean development rate per vessel (fraction/day)

Overall mean development rate (fraction/day)

Control

R1

R2

R3

R4

R5

R6

0.0543

0.0601

0.0556

0.0612

**

0.0635

0.0589

1000

R1

R2

R3

R4

R5

R6

**

0.0648

0.0645

0.0597

0.0597

0.0648

0.0627

* mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)

** Not calculated due to an emergence of greater than 20

R1 - R6 = Replicates 1 - 6

Table 4: Dry weight of surviving larvae of day 10

Nominal concentration (mg/kg)*

Total larvae dry weight (mg)

Mean individual larvae dry weight (mg)

Control R6

19.4

0.97

Control R7

22.6

1.19

1000 R6

16.0

0.84

1000 R7

15.0

0.75

* mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment)

R7 -R8 = replicates replicates 7 and 8 prepared at the start of the study for sacrifice on day 10

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of Monosodium salt of cyanuric acid to the sediment dwelling larvae of Chironomus riparius has been investigated and gave a 28-Day EC50 (emergence) of greater than 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment). The No Observed Effect Concentration was 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid/kg dry weight of sediment). The EC50 (development rate) based on nominal test concentrations was greater than 1000 mg test material/kg dry weight of sediment (equivalent to 756 mg cyanuric acid)

Description of key information

Sediment-water chironomid toxicity test according to OECD Guideline 218 with the monosodium salt of cyanuric acid.

Key value for chemical safety assessment

EC50 or LC50 for freshwater sediment:
756 mg/kg sediment dw
EC10, LC10 or NOEC for freshwater sediment:
756 mg/kg sediment dw

Additional information