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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
The test was realized in similar way to OECD 202 guideline. No data on GLP.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
not specified
Analytical monitoring:
not specified
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Age at study initiation (mean and range, SD): < 24 h old
Test type:
static
Water media type:
freshwater
Total exposure duration:
48 h
Hardness:
Hard water
Test temperature:
20 ºC
Nominal and measured concentrations:
No data
Details on test conditions:
OTHER TEST CONDITIONS
- Adjustment of pH: No
Test solutions were apparently un-neutralized.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility
Reference substance (positive control):
not specified
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
65 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: (no adjustment of pH)

The 48h EC 50 of acetic acid was 65 mg/L (basis for effect: mobility) with no adjustment of pH.

Validity criteria fulfilled:
yes
Conclusions:
The 48 h EC 50 of acetic acid was 65 mg/L (basis for effect: mobility) with no adjustment of pH.
Executive summary:

Daphnia magna were exposed to a series of concentrations of acetic acid for 48 h. The 48h EC50 of acetic acid was 65 mg/L (basis for effect: mobility) with no adjustment of pH.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Test method was according to DIN 38412, Part II guideline (Daphnia short-time test). No data on GLP.
Qualifier:
according to guideline
Guideline:
other: DIN 38412, Part II (Daphnia short-time test)
Deviations:
not specified
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
no
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnid
- Strain: Standardized strain IRCHA.
- Source: Laboratory own breeding
- Age at study initiation (mean and range, SD): 24 hours old
- Feed: The stock cultures of test organisms were fed dry algae, but no feeding occurred during the 24-hour exposure.
Test type:
static
Water media type:
freshwater
Total exposure duration:
24 h
Test temperature:
The room was thermostatically controlled at 20 ° C.
pH:
8.0 ± 0.2
Nominal and measured concentrations:
No data
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 50 mL beakers, fill volume: 20 mL.
- No. of organisms per vessel: 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Testing of the toxic action of acetic acid was performed in a chemically and physically defined standardized culture medium ("artificial fresh water").
- Intervals of water quality measurement: At the end of the test period, pH and dissolved oxygen concentration were measured.

OTHER TEST CONDITIONS
- Adjustment of pH: Yes and No
The stated result was for test solutions neutralized (pH 8.0) prior to daphnid exposures. The pH of unneutralized test solutions was not stated.

- Photoperiod: 9 hours light / 15 hours dark
- Light intensity: 2.5 W/m2

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility
Reference substance (positive control):
yes
Remarks:
(potassium dichromate)
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
95 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: (no adjustment of pH)
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
6 000 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: (adjusted to pH 8.0)
Results with reference substance (positive control):
- EC50: 1.3 mg/L (0.9-1.9 mg/L)

The EC 50 of acetic acid was 95 mg/L (basis for effect: mobility) with no adjustment of pH. The EC50 was 6000 mg/L with adjustment of pH to 8.0.

Validity criteria fulfilled:
not specified
Remarks:
(There is no information about control results)
Conclusions:
The EC 50 of acetic acid was 95 mg/L (basis for effect: mobility) with no adjustment of pH. The EC50 was 6000 mg/L with adjustment of pH to 8.0.
Executive summary:

A largely standardized procedure of water toxicology for testing the potential toxic action of water pollutants measured by the immobilization of Daphnia magna Straus according to DIN 38412, Part II guideline (Daphnia short-time test) is presented. Testing of the toxic action of acetic acid was performed in a chemically and physically defined standardized culture medium ("artificial fresh water"). Potassium dichromate was used as the reference substance.

The EC 50 of acetic acid was 95 mg/L (basis for effect: mobility) with no adjustment of pH. The EC50 was 6000 mg/L with adjustment of pH to 8.0.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Remarks:
A standardised method was used. No GLP.
Principles of method if other than guideline:
The EC50 of 86 chemicals was determined using a standardised method.
GLP compliance:
no
Test organisms (species):
Daphnia magna
Test type:
static
Water media type:
freshwater
Total exposure duration:
24 h
Test temperature:
21-25 ºC
Details on test conditions:
EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mortality
Key result
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
47 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mortality
Validity criteria fulfilled:
not applicable
Conclusions:
24 h LC 50 for Daphnia was 47 mg/L.
Executive summary:

The 24 h EC50 of Acetic acid for Daphnia was determined to be 47 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Remarks:
Test method was not according to any guideline. No data on GLP.
Principles of method if other than guideline:
An acute toxicity test was performed with Moina micrura in a renewal system. Several concentrations of Acetic acid were tested (0, 104.95, 125.94, 146.93, 167.92, 188.91, 209.90, 230.89, and 251.88 mg/L). The exposition lasted 96 hours.
GLP compliance:
not specified
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
other: Moina micrura
Details on test organisms:
TEST ORGANISM
- Length at study initiation (length definition, mean, range and SD): 0.09 mm
Test type:
other: renewal
Water media type:
freshwater
Total exposure duration:
4 d
Hardness:
100 mg/L CaCO3
pH:
7.21
Dissolved oxygen:
5.3 mg/L
Nominal and measured concentrations:
Measured concentrations:
104.95, 125.94, 146.93, 167.92, 188.91, 209.90, 230.89, and 251.88 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 500 mL beakers; a beaker contained 300 mL water
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4

TEST MEDIUM / WATER PARAMETERS
The test medium was replaced every 24 h by fresh water and the desired quantity of respective acid was immediately added to the water to assure a constant concentration of the concerned acid in the solution and also to avoid other abiotic factors interfering with the animals’ performance.
- Alkalinity: 172 mg/L CaCO3

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mortality of the test organisms was recorded every 24 h and dead organisms were counted and removed from the experimental container immediately to avoid depletion of dissolved oxygen. Total mortality of the animals recorded up to 96 h.
Reference substance (positive control):
no
Key result
Duration:
4 d
Dose descriptor:
LC50
Effect conc.:
163.72 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: (156.38-171.07 mg/L)

The 96 h-LC50 was 163.72 (156.38-171.07) mg/L (basis for effect: mortality).

Validity criteria fulfilled:
not applicable
Conclusions:
The 96 h-LC50 was 163.72 (156.38-171.07) mg/L (basis for effect: mortality).
Executive summary:

An acute toxicity test was performed with Moina micrura in a renewal system. Several concentrations of Acetic acid were tested (0, 104.95, 125.94, 146.93, 167.92, 188.91, 209.90, 230.89, and 251.88 mg/L). The exposition lasted 96 hours.

The 96 h-LC50 was 163.72 (156.38-171.07) mg/L (basis for effect: mortality).

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Remarks:
Study poorly documented. No GLP.
Principles of method if other than guideline:
The NOEC for Daphnia (younger than 8 days) in 16 h was determined.
GLP compliance:
no
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Age at study initiation (mean and range, SD): < 8 h
Test type:
static
Water media type:
freshwater
Total exposure duration:
16 h
Test temperature:
25 ºC
Details on test conditions:
EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility
Duration:
16 h
Dose descriptor:
NOEC
Effect conc.:
150 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mobility
Validity criteria fulfilled:
not applicable
Conclusions:
The 16 h NOEC for Daphnia was 150 mg/L.
Executive summary:

The 16 h NOEC for Daphnia was 150 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: No data available to evaluate the reliability
Principles of method if other than guideline:
Daphnia magna were exposed to a series of concentrations of acetic acid. The endpoint was immobilization. 24-h old animals were used. The results were observed after 24 hours.
GLP compliance:
no
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
Daphnia magna
Test type:
static
Water media type:
freshwater
Total exposure duration:
24 h
Test temperature:
20-22 ºC
pH:
7.6-7.7
Nominal and measured concentrations:
No data
Reference substance (positive control):
not specified
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
7 170 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
mobility

The 24-h LC50 for Daphnia magna was 7170 mg/L.

Validity criteria fulfilled:
not specified
Conclusions:
The 24-h LC50 for Daphnia magna was 7170 mg/L.
Executive summary:

The 24 hour LC50 was determined by means of a standardised procedure using 24-h-old animals from a clone of Daphnia magna. The 24-h LC50 was 7170 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
158.26 mg/L
Remarks on result:
other: (Read-across approach from acetic acid effect concentration based on test material, basis for effect: mobility and with no adjustment of pH)
Details on results:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (48h EC50 =65 mg/L, with no adjustment of pH and basis for effect: mobility), the read-across approach is applied and the 48h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 158.26 mg/L, with no adjustment of pH.
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (48h EC50 =65 mg/L, with no adjustment of pH and basis for effect: mobility), the read-across approach is applied and the 48h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 158.26 mg/L, with no adjustment of pH.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (48h EC50 =65 mg/L, with no adjustment of pH and basis for effect: mobility), the read-across approach is applied and the 48h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 158.26 mg/L, with no adjustment of pH.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
231.3 mg/L
Remarks on result:
other: (Read-across approach from acetic acid effect concentration based on test material, basis for effect: mobility and with no adjustment of pH)
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
14 608.33 mg/L
Remarks on result:
other: (Read-across approach from acetic acid effect concentration based on test material, basis for effect: mobility and pH adjusted to 8.0)
Details on results:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (24h EC50 = 95 mg/L, with no adjustment of pH and 24h EC50 = 6000 mg/L, with adjustment of pH to 8.0; basis for effect: mobility), the read-across approach is applied and the 24h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 231.30 mg/L, with no adjustment of pH and 14608.33 mg/L with adjustment of pH to 8.0.
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (24h EC50 = 95 mg/L, with no adjustment of pH and 24h EC50 = 6000 mg/L, with adjustment of pH to 8.0; basis for effect: mobility), the read-across approach is applied and the 24h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 231.30 mg/L, with no adjustment of pH and 14608.33 mg/L with adjustment of pH to 8.0.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (24h EC50 = 95 mg/L, with no adjustment of pH and 24h EC50 = 6000 mg/L, with adjustment of pH to 8.0; basis for effect: mobility), the read-across approach is applied and the 24h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 231.30 mg/L, with no adjustment of pH and 14608.33 mg/L with adjustment of pH to 8.0.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
114.43 mg/L
Remarks on result:
other: (Read-across approach from acetic acid effect concentration based on test material and basis for effect: mortality)
Details on results:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (24h EC50 = 47 mg/L, basis for effect: mortality), the read-across approach is applied and the 24h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 114.43 mg/L.
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (24h EC50 = 47 mg/L, basis for effect: mortality), the read-across approach is applied and the 24h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 114.43 mg/L.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (24h EC50 = 47 mg/L, basis for effect: mortality), the read-across approach is applied and the 24h EC50 for diacetoxydi-tert-butoxysilane is calculated to be 114.43 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
4 d
Dose descriptor:
LC50
Effect conc.:
398.61 mg/L
Remarks on result:
other: (Read-across approach from acetic acid effect concentration based on test material and basis for effect: mortality)
Details on results:
Based on the experimental results obtained with the supporting substance acetic acid for Moina micrura (4d LC50 = 163.72 mg/L, basis for effect: mortality), the read-across approach is applied and the 4d LC50 for diacetoxydi-tert-butoxysilane is calculated to be 398.61 mg/L.
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid for Moina micrura (4d LC50 = 163.72 mg/L, basis for effect: mortality), the read-across approach is applied and the 4d LC50 for diacetoxydi-tert-butoxysilane is calculated to be 398.61 mg/L.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid for Moina micrura (4d LC50 = 163.72 mg/L, basis for effect: mortality), the read-across approach is applied and the 4d LC50 for diacetoxydi-tert-butoxysilane is calculated to be 398.61 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Duration:
16 h
Dose descriptor:
NOEC
Effect conc.:
365.21 mg/L
Remarks on result:
other: (Read-across approach from acetic acid effect concentration based on test material and basis for effect: mobility)
Details on results:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (16h NOEC = 150 mg/L, basis for effect: mobility), the read-across approach is applied and the 16h NOEC for diacetoxydi-tert-butoxysilane is calculated to be 365.21 mg/L.
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (16h NOEC = 150 mg/L, basis for effect: mobility), the read-across approach is applied and the 16h NOEC for diacetoxydi-tert-butoxysilane is calculated to be 365.21 mg/L.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid for Daphnia magna (16h NOEC = 150 mg/L, basis for effect: mobility), the read-across approach is applied and the 16h NOEC for diacetoxydi-tert-butoxysilane is calculated to be 365.21 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable. Acetic acid and its salts are grouped together because of their close structural relationship (US EPA officially recognises acetic acid and acetates as a subcategory). Therefore, sodium acetate has comparable values with acetic acid and the target substance diacetoxydi-tert-butoxysilane.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
12 779.35 mg/L
Remarks on result:
other: (Read-across approach from sodium acetate effect concentration based on test material and basis for effect: mobility)
Details on results:
Based on the experimental results obtained with the supporting substance sodium acetate for Daphnia magna (24h LC50 = 7170 mg/L, basis for effect: mobility), the read-across approach is applied and the 24h LC50 for diacetoxydi-tert-butoxysilane is calculated to be 12779.35 mg/L.
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental results obtained with the supporting substance sodium acetate for Daphnia magna (24h LC50 = 7170 mg/L, basis for effect: mobility), the read-across approach is applied and the 24h LC50 for diacetoxydi-tert-butoxysilane is calculated to be 12779.35 mg/L.
Executive summary:

Based on the experimental results obtained with the supporting substance sodium acetate for Daphnia magna (24h LC50 = 7170 mg/L, basis for effect: mobility), the read-across approach is applied and the 24h LC50 for diacetoxydi-tert-butoxysilane is calculated to be 12779.35 mg/L.

Description of key information

Weight of evidence: Based on experimental results obtained in short-term toxicity to aquatic invertebrates studies with supporting substance acetic acid, read-across approach was applied and EC50 (48h) for diacetoxydi-tert-butoxysilane was calculated to be 158.26 mg/L (based on mobility and with no pH adjustment).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
158.26 mg/L

Additional information

Weight of evidence:

Read-across from experimental results with acetic acid:

In the first study, Janssen et. al., 1993 (reliability 2), an acute immobilisation test with acetic acid was performed according to an equivalent method to OECD Guideline 202. The EC50 in Daphnia magna for 48h exposure period was 65 mg/L (basis for effect: mobility). Based on this experimental result, read-across approach from the supporting substance acetic acid was applied and EC50 (48h) for diacetoxydi-tert-butoxysilane was calculated to be 158.296 mg/L (based on mobility and with no pH adjustment).

In the study by Bringmann et. al, 1982 (reliability 2), a largely standardized procedure of water toxicology for testing the potential toxic action of water pollutants measured by the immobilization of Daphnia magna according to DIN 38412, Part II guideline (Daphnia short-time test) was performed. The EC50 (48h, basis for effect: mobilitly) for acetic acid was 95 mg/L with no pH adjustment and 6000 mg/L with pH adjustment. Based on this result, read-across approach from supporting substance acetic acid was applied and EC50 (48h, basis for effect: mobility) for diacetoxydi-tert-butoxysilane was calculated to be 231 mg/L with no pH adjustment and 14608.33 with pH adjustment.

In the study by Dowden et. al., 1965 (reliability 4), the EC50 of 86 chemicals was determined using a standardised method. The 24h EC50 of acetic acid for Daphnia magna was determined to be 47 mg/L (basis for effect: mobility). Based on this result obtained with the supporting substance acetic acid, read-across approach was applied and the EC50 (48h, based on mobility) for diacetoxydi-tert-butoxysilane was calculated to be 114.43 mg/L.

In the published study by Saha et. al., 2006 (reliability 4), an acute toxicity test was performed with Moina micrura in a renewal system. Based on the experimental results obtained with the supporting substance acetic acid for Moina micrura (96h LC50 = 163.72 mg/L, basis for effect: mortality), the read-across approach was applied and the 96h LC50 for diacetoxydi-tert-butoxysilane was calculated to be 398.61 mg/L.

Supporting studies:

Read-across from experimental results with acetic acid and sodium acetate:

There are two supporting studies from Anderson, 1944 (reliability 4) and Bringmann et. al., 1977, (reliability 3) performed for the supporting substances acetic acid and sodium acetate respectively. In the first one and based on the experimental results with supporting substance acetic acid (16h NOAEC = 150 mg/L for Daphnia magna and basis for effect: mobility), read-across approach was applied and the 16h NOAEC for diacetoxydi-tert-butoxysilane was calculated to be 365.21 mg/L. In the second study and based on the experimental results with supporting substance sodium acetate (24h LC50 = 7170 mg/L for Daphnia magna and basis for effect: mobility), the read-across approach was applied and the 24h LC50 for diacetoxydi-tert-butoxysilane was calculated to be 12779.35 mg/L.

According to the available information on short-term toxicity to aquatic invertebrates, could be pointed out that the toxicity of diacetoxydi-tert-butoxysilane is caused by the pH effect of acetic acid since the read-across approach applied from experimental data with acetic acid (EC50 (48h): 158.26 mg/L, no pH adjustment; EC(24h): 116,15 mg/L) is much more restrictive than the results obtained with the read-across approach from experimental data with sodium acetate, the neutralised form of the acid (LC50 (24h): 12779.35 mg/L). In the same way, in the study performed by Bringmann et. al. 1982 with acetic acid and after applying the read-across approach, the LC50 (24h) calculated for diacetoxydi-tert-butoxysilane was 231.30 mg/L with no pH adjustment and 14608.33 mg/L with pH adjustment.

Key value for chemical safety assessment:

According to the read-across approaches from experimental results with supporting substance acetic acid, the diacetoxydi-tert-butoxysilane key value for chemical safety assessment is calculated to be EC (48h) = 158.26 mg/L (based on mobility, with no pH adjustment). This value is the most restrictive result and it was obtained in the reliable study by Janseen et.al., 1993 (Klimisch 2) during an observation period of 48 h. Although an EC (24h) = 114.43 mg/L was obtained by read-across approach from the study by Dowden et. al., 1964, it was excluded for chemical safety assessment since the study was not assignable (Klimisch 4) with an observation period of 24 h.