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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:
key study
Study period:
2002-04-15 to 2002-07-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
Test media were not prepared in accordance with OECD guidance for testing difficult substances
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
- Nominal treatments: 100 mg/L and 10 mg/L (10% concentration of 100 mg/L water-soluble fraction)

- Sampling method: A sample of test media were taken from all treatments at the start (before introducing the test organisms) and at the end of the test.

- Sample storage conditions before analysis: Not reported
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A water-soluble fraction of the test substance was prepared by mixing 100 mg/l of the test substance with dilution water for 48 hours and then filtering (0.45 μm) to remove undissolved test substance. The water-soluble fraction was tested undiluted and at one-tenth of its original concentration.

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

- Strain: IRCHA

- Source: LPT Laboratory Culture

- Age at study initiation (mean and range, SD): 6-24 hours

ACCLIMATION

- Acclimation period: at least one week

- Acclimation conditions (same as test or not): yes

- Type and amount of food: algae (Scenedesmus subspicatus) plus a small quantity of sewage from the aerated phase of treatment
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
250 mg/L as CaCO3
Test temperature:
20+/-1ºC
pH:
7.61-8.15
Dissolved oxygen:
≥80% ASV
Nominal and measured concentrations:
Nominal loading rates: 0(Control), 100 mg/L and 10 mg/L (10% concentration of 100 mg/L water-soluble fraction).

A loading rate of 100 mg/L is above the expected solubility of the substance in the test medium. Measured dissolved organic carbon concentrations were below 5% of the theoretical values at the start and end of the test.
Details on test conditions:

- Aeration: none

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: aerated reconstituted water

- Alkalinity: 0.8 mmol/L

- Ca/mg ratio: 4:1

- Culture medium different from test medium: no

- Intervals of water quality measurement: Start and end ot test

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 h light/8 h dark

- Light intensity: 500 Lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility after 24 and 48 hours

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 10
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
48 h
Dose descriptor:
NOELR
Effect conc.:
< 10 other: percent concentration of the 100 mg/l water-soluble fraction
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Conclusions:
An EL50 of >100 mg/l was reported for the test substance. The result is considered reliable.
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 attached justification for grouping of substances in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
disregarded due to major methodological deficiencies
Study period:
2002-05-07 to 2003-02-14
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
significant methodological deficiencies
Qualifier:
according to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
Test media were not prepared in accordance with OECD guidelines for testing difficult substances
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
- Nominal treatments: 0(Control), 0.464, 1.00, 2.15, 4.64, 10.0 and 100 mg/l.

- Sampling method: An aliquot of test medium from all test concentrations at the start of the test before filling the test vessels. A combined aliquot was collected from the test media from all four exposure vessels of all test concentrations at the end of the test (48 hours).

- Sample storage conditions before analysis: The samples were stored at -20ºC prior to analysis.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Two sets of test media were prepared. The first set were prepared from a stock solution of the test substance prepared by adding 100 mg/l of the test substance to dilution water and stirring for 4 hours followed by passage through a 0.45 μm cellulose acetate filter. Other treatments were prepared by dilution of the filtrate. The second set were prepared from a stock solution prepared in a similar way except that it had been shaken for 48 hours.

- Controls: Dilution water

- Evidence of undissolved material (e.g. precipitate, surface film, etc): It is likely that the solubility of the test substance will have been exceeded in the stages of test media preparation prior to filtration of the stock solutions.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source: IRChA, France

- Age at study initiation (mean and range, SD): 6-24 hours

- Method of breeding: Laboratory stock culture

- Feeding during test: None

ACCLIMATION

- Acclimation period: At least 7 days

- Acclimation conditions (same as test or not): yes

- Type and amount of food: Unicellular algae (Scenedesmus subspicatus) and a small amount of aerated sewage.

- Feeding frequency: no data
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
250 mg/l as CaCO3
Test temperature:
20+/-1ºC
pH:
First set of test media: 7.06-8.09 in 0.464 to 10.0 mg/l nominal treatments and <5.6 in 100 mg/l nominal treatment.

First set of test media: 7.59-8.00 in 0.464 to 10.0 mg/l nominal treatments and approximately 5.0 in 100 mg/l nominal treatment.

It is likely that pH effects will have contributed to effects observed in the 100 mg/l nominal treatments in both tests.
Dissolved oxygen:
≥80% ASV
Salinity:
not applicable
Nominal and measured concentrations:
Nominal treatments: 0(Control), 0.464, 1.00, 2.15, 4.64, 10.0 and 100 mg/l.

Measured DOC concentrations in the test media prepared from the stock solution that had been shaken for 48 hours were <5% of the theoretical values. The test media prepared from the other stock solution were not analysed.

The results are reported and interpreted in the test report with reference to the nominal concentrations. The results have also been interpreted here with reference to the estimated concentration corresponding to the 48-h EC50 value. This is considered appropriate given the disparity between the measured and theoretical concentrations.
Details on test conditions:
TEST SYSTEM

- Test vessel:

- Type: no data

- Material, size: glass, 50 ml

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): static test

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4

- Biomass loading rate: 1 daphnid/10 ml

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted fresh water prepared by adding salts to demineralised water.

- Alkalinity: 0.8 mmol/l

- Ca/mg ratio: 4:1

- Culture medium different from test medium: no

- Intervals of water quality measurement: Start and end of test

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 hours light, 8 hours dark

- Light intensity:500 lux (+/-20%)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility after 24 and 48 hours

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2.2-10

- Range finding study: no
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
7 mg/L
Nominal / measured:
nominal
Conc. based on:
other: hydrolysis product (first test)
Basis for effect:
mobility
Remarks on result:
other: 4-13
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
14 mg/L
Nominal / measured:
nominal
Conc. based on:
other: hydrolysis product (second test)
Basis for effect:
mobility
Remarks on result:
other: 9-24
Duration:
48 h
Dose descriptor:
NOELR
Effect conc.:
0.464 mg/L
Nominal / measured:
nominal
Conc. based on:
other: hydrolysis product (first and second test)
Basis for effect:
mobility
Details on results:
- Behavioural abnormalities: no data

- Mortality of control: First test = 2.5%, Second test = 0

- Other adverse effects control: none

- Other adverse effects in treatments: It is likely that low pH will have contributed to the effects observed in the highest (nominal 100 mg/l) treatment in both tests.
Reported statistics and error estimates:
The EL50 value based on nominal loading rates was calculated by linear regression employing probit analysis (Probit Program Version 1.5, U.S. Environmental Protection Agency, 1992).

The EC50 value determined on the basis of measured concentrations and the NOEC (NOELR) values were obtained directly from the raw data.

Table 1. Test results (first and second tests)

 Nominal test substance concentration (mg/l)  Mean percentage immobilisation after 24 hours - first test Mean percentage immobilisation after 48 hours - first test   Mean percentage immobilisation after 24 hours - second test Mean percentage immobilisation after 48 hours - second test 
 0 (Control)  0  2.5  0  0
 0.464  0  0  0  0
 1.00  0  10  5  5
 2.15  10  40  5  5
 4.64  15  45  15  20
 10.0  40  60  15  25
 100  45  90  100  100

Table 2. Measured dissolved organic carbon (DOC) concentrations in the test media prepared for the second test.

 Nominal concentration of test substance (mg/l)  Theoretical DOC concentration (mg/l)  Actual DOC concentration at start of test (mg/l)  Actual DOC concentration at end of test (mg/l)
0.462 0.2 <1.0  1.3
1.00 0.5 <1.0 <1.0
2.15 1.1 <1.0 <1.0
4.64 2.5 1.1 1.6
10.0 5.3 1.3 <1.0
100 53.4  1.4 2.0

Limit of Quantitation (LOQ) = 10 mg/l

Limit of Detection (LOD) = 1.0 mg/l

Validity criteria fulfilled:
no
Conclusions:
48-h EL50 values of 7 and 14 mg/l and a NOELR of 0.464 mg/l have been determined in two tests for the effects of the test substance on mobility of Daphnia magna based on nominal test substance concentration. The study was severely compromised by significant methodological deficiencies or use of unsuitable test system; results not fit for purpose.

Description of key information

EL50 (48) > 100 mg/L (nominal, Daphnia magna, OECD 202, based on read across to CAS No. 16415-12-6)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
EC50
Effect concentration:
> 100 mg/L

Additional information

A study is available for the registered substance, which reported two EL50 values of 7 and 14 mg/l from two separate experiments. However, due to deficiencies in the methodology, the reliability could not be determined. Therefore, data was read-across from the structural analogue substance trimethoxy(hexadecyl)silane(CAS No. 16415-12-6) for the assessment of acute toxicity towards aquatic invertebrates. Both substances hydrolyse in the aquatic environment, but with very different hydrolysis rates (DT50 = << 2 min at room temperature and pH 7 (target); DT50 > 14 d at pH 7 (source)). However, both form the same silanol hydrolysis product hexadecylsilanetriol. The second hydrolysis product of the target substance is hydrochloric acid, while the second hydrolysis product of the source compound is methanol. Hydrochloric acid and methanol are both well described substances in the public domain literature and both are not expected to contribute to the overall aquatic toxicity of target and source substances (OECD SIDS, 2002; OECD SIDS 2004). Therefore, hydrochloric acid and methanol can be disregarded in the environmental hazard assessment. Further information can be found in an attached read-across justification in Section 13 of IUCLID.

 

In the valid acute toxicity test on aquatic invertebrates according to OECD guideline 202 and under GLP conditions, Daphnia magna was exposed to trimethoxy(hexadecyl)silane over 48 h to the nominal loading rates of 0 (control), 100 mg/L and 10 mg/L (10% concentration of 100 mg/L water-soluble fraction). The test solutions were analytically monitored via DOC analysis. Since the tested substance is poorly water soluble analytical results showed that measured DOC concentrations were <5% of nominal. An EL50 value of >100 mg/L (nominal loading rate) was determined in this study.

The result was obtained under static test conditions. In view of the slow hydrolysis rate and exposure regime it is likely that the test organisms were exposed predominantly to the parent of the tested source substance.

 

References:

OECD, 2002. Hydrogen Chloride - SIDS Initial Assessment Report for SIAM 15, Boston, USA: UNEP Publications.

OECD SIDS, 2004. Methanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.