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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The result was obtained by an appropriate predictive method.
Principles of method if other than guideline:
The ECOSAR ‘neutral organics’ QSARs for acute data have been applied and the effect concentrations calculated using log Kow and molar mass as input variables. An additional factor of *0.2 has been applied to the results.

The USEPA model ECOSAR was used as the basis for the estimation. This method is well-validated for ‘neutral organics’, i.e. those which act by a general narcotic mechanism, the potency of which is usually related to log Kow. Its scope is acute and long-term effects for the three standard trophic levels.
The method was validated for use with organosilicon compounds with a high weight percent of Si and limited or no additional functionality. Many of the reliable data for the category are limit values, therefore, the data were considered in terms of the range of theE(L)C50, in accordance with normal classification bands:    
E(L)C50 < 1 mg/l;
E(L)C50 in the range > 1 mg/l to 10 mg/l;
E(L)C50 in the range > 10 mg/l to 100 mg/l;
E(L)C50 > 100 mg/l.

In broad terms ECOSAR predicted correctly for most substances for each trophic level. However, performance was improved significantly by application of a factor of 0.2 to each predicted value (expressed in mg/l). This is equivalent to saying that the organosilicon substances are slightly more toxic than the general ECOSAR ‘neutral organics’ regression lines, although still well within the range of each model. The factor of 0.2 is applicable to fish,Daphniaand algae, across the whole range of log Kowvalues.
It is concluded that the acute effects of the substances in the sub-category can therefore be predicted from ECOSAR, with a minor modification.
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
17.9 mg/L
Remarks on result:
other: Based on O[Si](O)(c1ccccc1)c2ccccc2 and log Kow of -2.4
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2004-02-23 to 2004-02-27
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Qualifier:
according to
Guideline:
EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Negative Control, 13, 22, 36, 60 and 100 mg/L

- Sampling method: Samples were collected from the each test chamber of each concentration at test initiation and termination. Test solution samples were collected at mid-depth, placed in glass vials, and analyzed immediately.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: primary stock solution was prepared by mixing diphenylsilanediol in dilution water (Wildlife International, Ltd. well water) at a nominal concentration of 100 mg/L. The primary stock was mixed for approximately 24-hours using a stainless-steel top-down electric mixer, and appeared clear and colourless with white particles on the bottom, surface and throughout the solution in the test chamber at stirring termination. The primary stock was then allowed to settle for approximately 24-hours, to allow particulate matter to settle, and appeared clear and colorless with white particles on the surface and bottom of the test solution. The four remaining test solutions were prepared in dilution water at nominal concentrations of 13, 22, 36 and 60 mg/L by proportional dilution of the primary (100 mg/L) stock. The primary stock was siphoned from approximately the middle of the solution using a glass pipette in an effort to avoid particulates on the surface and bottom of the aquaria. The solutions were mixed by inversion, and approximately 250 mL of test solution was distributed to each of two replicates per treatment. The test solutions appeared clear and colourless at test initiation and termination, except for the 100 mg/L treatment group which was clear and colorless with a slight amount of particles throughout the solution at test initiation and clear and colorless with very few particles on bottom of test chamber at test termination.

- Controls: Dilution water
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source: Source: Wildlife International, Ltd. cultures

-Age at study initiation: <24 hours old

- Culture: Adult daphnids were cultured in water from the same source and at approximately the same temperature as used during the test. Daphnids in the cultures were held for 13 days prior to collection of the neonates for testing. The adults showed no signs of disease or stress during the holding period.

- Culture conditions: During the 13-day holding period preceding the test, water temperatures ranged from 20.1 to 20.6ºC. The pH of the water ranged from 8.2 to 8.6, and dissolved oxygen measurements ranged from 7.3 to 9.0 mg/L (≥81% saturation).

- Test organisms: Neonate daphnids were obtained for testing from five individual adult daphnids that had already produced at least one previous brood. At test initiation, the juvenile daphnids were collected from the cultures and indiscriminately transferred one and two at a time to transfer containers until each transfer chamber contained 10 daphnids. Transfer chambers were indiscriminately assigned to test chambers, and then the daphnids were released into the test chambers. All transfers were made below the water surface using wide-bore pipettes.

- Feeding: Daphnids in the cultures were fed daily a mixture of yeast, Cerophyll® and trout chow, as well as a suspension of the freshwater green alga, Selenastrum capricornutum. The adults were fed prior to test initiation, but neonates were not fed during the test.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
None
Hardness:
132 mg/L as CaCO3
Test temperature:
19.5 to 20.6 ºC



pH:
8.5 to 8.8
Dissolved oxygen:
≥8.4 mg/L (96% of saturation)
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: Negative Control, 13, 22, 36, 60 and 100 mg/L

Mean measured concentrations:
The results are reported and interpreted with reference to the mean measured concentrations.
Details on test conditions:
TEST SYSTEM

- Test vessel:

- Type: open

- Material, size, headspace, fill volume: 250 mL glass beakers containing 200 mL of test solution.

- Aeration: none

- Renewal rate of test solution: none

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 2

- No. of vessels per control (replicates): 2

- Biomass loading rate: 1 daphnia/20 ml


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Well water. The well water was passed through a sand filter to remove particles greater than approximately 25 μm, and pumped into a 37,800-L storage tank where the water was aerated with spray nozzles. Prior to use, the water again was filtered (0.45 μm) and passed through an ultraviolet (UV) sterilizer to remove microorganisms and fine particles.

- Total organic carbon: < 1 mg/L

- Hardness: 132 mg/L as CaCO3

- Alkalinity: 180 mg/L as CaCO3

- Conductivity: 300 mhos/cm

- Culture medium different from test medium: No

- Intervals of water quality measurement: Daily


OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 hours light:8 hours dark

- Light intensity: 374 Lux


EFFECT PARAMETERS MEASURED: All organisms were observed periodically to determine the numbers of mortalities and immobile organisms in each control and treatment group. The numbers of individuals exhibiting clinical signs of toxicity or abnormal behavior also were evaluated. Observations were made approximately 4, 24 and 48 hours after test initiation.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
24 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: mortality and immobilization
Details on results:
Biological observations: All daphnids in the negative control group appeared healthy and normal throughout the test. All daphnids in the 11 mg/L treatment appeared normal throughout the study, while lethargy was observed among daphnids in the 19 mg/L treatment at test termination. In the 11, 19, 31, 52 and 87 mg/L treatment groups, mortality/immobility at 48 hours was 0, 20, 80, 100 and 100%, respectively.
Reported statistics and error estimates:
The mortality/immobility data were analyzed using the computer program of C. E. Stephan. The program was designed to calculate the EC50 value and the 95% confidence interval by probit analysis, the moving average method, and binomial probability with nonlinear interpolation. In this study,
the probit method was used to calculate the 48-hour EC50 value. There was <50% mortality or immobility in any treatment group at 24 hours, which precluded the statistical calculation of an EC50 value. Therefore, the 24-hour EC50 value was determined by visual inspection of the mortality, immobility and observation data.

Table 1. Results of analysis of test media

 

Nominal test substance concentration (mg/L)

Mean measured concentration (mg/L)

Mean measured concentration as percentage of nominal

0 (Control)

-

-

13

11

85

22

19

86

36

31

86

60

52

87

100

87

87

 

Table 2. Test results

 

Mean measured concentration (mg/L)

Mean percentage dead/immobile daphnids after 24 hours

Mean percentage dead/immobile daphnids after 48 hours

0 (Control)

0

0

11

0

0

19

0

20

31

0

80

52

0

100

87

20

100

 

Validity criteria fulfilled:
yes
Conclusions:
A 48-hour EC50 value of 24 mg/L has been determined for the effects of the test substance on mobility/mortality of Daphnia magna based on mean measured concentrations.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the attached justification for grouping of substances in IUCLID Section 13.
Reason / purpose:
read-across source
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
24 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: mortality and immobilization
Remarks on result:
other: 21-28

Description of key information

48-hour EC50 = 24 mg/l

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
24 mg/L

Additional information

Measured data were not available for dichloro(diphenyl)silane (80-10-4) for short term toxicity to aquatic invertebrates. Due to the rapid rate of hydrolysis, measured data for the hydrolysis product diphenylsilanediol (947-42-2) was considered appropriate to use to determine the toxicity of the substance. A 48-hour EC50 value of 24 mg/l has been determined for the effects of the test substance on mobility/mortality of Daphnia magna based on mean measured concentrations according to OECD guideline 202 (Wildlife international 2004b). The study is considered reliable and was selected as key. These values are supported by a QSAR calculated 48 hr LC50 of 17.9 mg/l.