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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
29 Mar 19 Apr 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Deviations:
no
GLP compliance:
yes
Remarks:
according to the Japanese GLP Standard
Specific details on test material used for the study:
Details on properties of test material:
PHYSICO-CHEMICAL PROPERTIES
- Melting point: < 0°C
- Boiling point: 123°C
- Vapour pressure: < 2.7 kPa at 25 °C
- Water solubility (under test conditions): low
- Stability in water: Test item is hydrolyzed (half-life: within 30 min)
Analytical monitoring:
yes
Details on sampling:
- Sampling method: sampled directly by each vessel and pre-treatment was not performed
- Sample storage conditions before analysis: no storage before analysis
- Methanol was measured, since the test item was quickly hydrolyzed
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test item was measured and diluted in dilution water with stirring for 120 min
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Source: Incorporated Administrative Agency, National Institute for Environmental Studies, Tsukuba, Japan
- Age of parental stock (mean and range, SD): within 24 hours
- Feeding during test: yes
- Food type: Chlorella vulgaris
- Amount: 0.15 mgC/animal/day

ACCLIMATION
- Acclimation period: 2006-03-08 ~ 2006-03-29
- Acclimation conditions (same as test or not): similar to test (acclimation condition: water was changed three times a week, test condition: water was changed everyday)
- Type and amount of food:Chlorella vulgaris, 0.2 mgC/animal/day
- Health during acclimation (any mortality observed): < 5% during 2 weeks before exposure

Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Hardness:
240 - 250 (as CaCO3) mg/L, measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.
Test temperature:
19.7 - 20.2 °C, measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.
pH:
7.1 - 8.4, measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.
Dissolved oxygen:
4.4 - 8.8 mg/L (> 3mg/L), measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.
Nominal and measured concentrations:
Nominal concentration: 12, 21, 38, 67 and 120 mg/L
Time-weighted mean: 7.2, 14.6, 28.1, 52.4 and 99.8 mg/L
The measured concentration was calculated based on the concentration of methanol yielded on hydrolysis
Details on test conditions:
TEST SYSTEM
- Test vessel: 100 mL beaker
- Type (delete if not applicable): closed with a teflon sheet
- Material, fill volume: glass, 80 mL
- Aeration: no
- Renewal rate of test solution (frequency/flow rate): once a day
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: same medium

OTHER TEST CONDITIONS
- Adjustment of pH: no adjustment
- Photoperiod: 16 hours in the light, 8 hours in the dark
- Light intensity: < 800 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
mortality and general condition (abnormal behaviour) of parental animals, cumulative number of juveniles and time to first brood production were observed everyday.

RANGE-FINDING STUDY
- Test concentrations: 120 mg/L (nominal concentration)
- Results used to determine the conditions for the definitive study: An acute toxicity test of daphnia magna was performed and EC50 for 48 hours was > 120 mg/L.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate (analytical grade)
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
28.1 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks:
cumulative number of juveniles per adult
Remarks on result:
other: The measured concentration was calculated based on the concentration of methanol yielded on hydrolysis
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
52.4 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks:
cumulative number of juveniles per adult
Remarks on result:
other: The measured concentration was calculated based on the concentration of methanol yielded on hydrolysis
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
119 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: (95% CL 104 - 149 mg/l; extrapolated from effects at conc. 14.6-99.8 mg/l).
Details on results:
- Mortality of parent animals: see Table 2
- No. of offspring produced per day per female: see Table 3
- Time to first brood release or time to hatch: Control: 8 - 9 days, 7.2 mg/L: 8 - 9 days, 14.6 mg/L: 8 - 13 days, 28.1 mg/L: 8 - 9 days, 52.4 mg/L: 8 - 9 days, 99.8 mg/L: 9 - 15 days
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC 50 was 0.75 ± 0.14 mg/L
Reported statistics and error estimates:
Logit test for EC50, Williams's multicomparison test for NOEC and LOEC

Table 1. Calculated concentration of the test item using methanol concentration in test water

Nominal concentration

(mg/L)

 

Measured concentration (mg/L)

TWM (*1)

(% of nominal)

Date

0 new

1 old

14 new

15 old

20 new

21 old

Control

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

-

12.0

10.1

10.5

9.75

7.21

10.3

0.32 (*2)

7.20

(60) (*3)

21.0

19.2

17.6

17.1

13.5

15.6

6.01

14.6

(70)

38.0

33.5

32.0

31.1

20.2

31.6

21.5

28.1

(74)

67.0

57.3

51.3

60.3

37.6

67.4

44.3

52.4

(78)

120

104

96.4

102

77.0

120

101

99.8

(83)

New: Freshly prepared test solution

Old: Old test solutions before renewal

*1: Time-weighted mean calculated concentration during 21 days

*2: This value is estimate because it is not within the range of the calibration curve.

*3: This value is given for reference because of containing the estimate value.

Table 2. Mortality of parental Daphnia

Nominal concentration (mg/L)

Mean measured concentration

(mg/L)

Cumulative Number of Dead

(Percent Mortality)

Day 1

2

4

7

14

21

Control

-

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

12.0

7.20

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

21.0

14.6

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

38.0

28.1

0 (0)

1 (10)

1 (10)

1 (10)

1 (10)

1 (10)

67.0

52.4

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

120

99.8

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

12.0

7.20

0 (0)

0 (0)

0 (0)

1 (10)

1 (10)

1 (10)

Table 3. Cumulative number of juveniles produced per adult alive for 21 days

Nominal Conc., mg/L

 

Calculated Cnc., mg/L

Mean Cumulative Numbers of Juveniles ± S.D.

Inhibition Rate (%)

Significant difference

Control

-

107.8 ± 13.8

 

 

12.0

7.20

123.7± 8.1

-14.7

-

21.0

14.6

124.5 ± 18.9

-15.5

38.0

28.1

108.0 ± 19.4

-0.2

-

67.0

52.4

95.7 ± 17.2

11.2

**

120

99.8

69.8 ± 16.5

35.5

**

-: indicates no significant difference

**: indicates a significant difference (a = 0.01) from the control.

Validity criteria fulfilled:
yes
Conclusions:
A 21-day NOEC value of 28.1 mg/Lhas been determined for the effects of the test substance on the reproduction of Daphnia magna. Due to the rapid rate of hydrolysis, it is likely that the test organism were primarily exposed to the hydrolysis product of the test substance, vinylsilanetriol and methanol. These results can be expressed in terms of the hydrolysis products as NOEC 20 mg/L.

Description of key information

No data are available for tris(2 -methoxyethoxy)vinylsilane (CAS 1067 -53 -4). A 21 day NOEC value of 28.1 mg/L has however been determined for the effects of a read-across substance, Trimethoxy(vinyl)silane (CAS 2768-02-7), on the reproduction of Daphnia magna. It is likely that the test organisms were primarily exposed to the hydrolysis product of the test substance, vinylsilanetriol. The NOEC is equivalent to 20 mg/L when expressed in terms of the silanol hydrolysis product, vinylsilanetriol.

A 21-day NOEC of =500 mg/L has been concluded for the effects of 2-methoxyethanol on the reproduction of Daphnia magna.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
20 mg/L

Additional information

There are no reliable long-term invertebrate toxicity data available for tris(2 -methoxyethoxy)vinylsilane (CAS 1067-53-4), therefore good quality data for an appropriate structural analogue, trimethoxy(vinyl)silane (CAS 2768-02-7) have been read across. Both substances hydrolyse to the same hydrolysis product, vinylsilanetriol. The hydrolysis half-lives of tris(2-methoxyethoxy)vinylsilane and trimethoxy(vinyl)silane indicate that, under conditions relevant to ecotoxicity assessment, both will hydrolyse to vinylsilanetriol over the course of the test. The other hydrolysis products are 2-methoxyethanol and methanol, respectively; the properties of these substances are well characterised. Methanol is non-toxic to the environment and it is considered unlikely that its presence significantly affected the results of the test performed with trimethoxy(vinyl)silane.

A 21 day NOEC value of 28.1 mg/L has been determined for the effects of trimethoxy(vinyl)silane (CAS 2768-02-7) on the reproduction of Daphnia magna based on measured concentrations of the substance (MOE, 2006). The result was obtained under static test conditions. In view of the test media preparation method and exposure regime, it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results are expressed in terms of the concentration of the hydrolysis product, vinylsilanetriol.

The results may be expressed in terms of the concentration of the hydrolysis product, vinylsilanetriol, by applying a molecular weight correction (MW of silanol / MW of parent) * concentration of parent = 106.15 / 148.24 * 28.1 mg/L = 20 mg/L.

The study was considered to be reliability 1 (reliable without restriction).

A 21-day EC50of =500 mg/l (nominal) has been determined for the effects of 2-methoxyethanol on the reproduction ofDaphnia magna,in a reliable study conducted according to OECD 211(Devillers et al., 2002).