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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 to 19 March 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Qualifier:
according to guideline
Guideline:
ISO 7346-1 (Determination of the Acute Lethal Toxicity of Substances to a Freshwater Fish [Brachydanio rerio Hamilton-Buchanan (Teleostei, Cyprinidae)] - Part 1: Static Method)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
Duplicate samples for analysis were taken from the highest test concentration and the control according to the schedule below. The method of analysis is described in the appended Analytical Report (Appendix II).

Frequency: at t=0 h, t=24 h and t=96 h
Volume: 25 ml
Storage: Not applicable, samples were analysed on the day of sampling.
Vehicle:
no
Details on test solutions:
The standard test procedures required generation of test solutions, which should contain completely dissolved test substance concentrations or stable and homogeneous mixtures or dispersions. The testing of concentrations that disturb the test system should be prevented (e.g. film of the test substance on the water surface).

The batch of Octyltintris(2-ethylhexyl mercaptoacetate) tested was a clear colourless to light yellow liquid with a purity of 98.00% and the substance was not completely soluble in test medium at the initial loading rate prepared.

Preparation of test solutions started with a loading rate of 100 mg/l applying one day of magnetic stirring followed by a one day stabilisation period to reach maximum solubility of the test substance in the test medium. The slightly hazy and colourless Water Soluble Fraction (WSF) was filtered through glass wool and used as the highest test concentration, which was observed to be still slightly hazy. The lower test concentrations were prepared by subsequent dilutions of the WSF in test medium. These lower test concentrations were clear and colourless.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
Source: Zodiac, proefacc, "De Haar Vissen", Wageningen University and Research Centre, The Netherlands.
Mean length': 2.3 ± 0.2 cm
Mean weight': 0.33 ± 0.09 g
Characteristics: F1 from a single parent-pair bred in UV-treated water.
Total fish used: 20
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
180 mg CaCO3/L
Test temperature:
20.6 to 21.1°C depending on the sampling timing and considered series.
pH:
7.5 to 7.7 depending on the sampling timing and considered series.
Dissolved oxygen:
5.5 to 9.1 mg/L depending on the sampling timing and considered series.
Salinity:
Not applicable
Nominal and measured concentrations:
1.0, 10 and 100% of a WSF prepared at a loading rate of 100 mg/l
Details on test conditions:
Test duration: 96 hours
Test type: Static
Test vessels: 3.5 litres, all-glass, containing 3 litres of test solution
Test medium: Adjusted ISO medium with a hardness of 180 mg CaCO3 per litre and a pH of 7.7 ± 0.3.
Number of fish per concentration: 7 for the control and the highest test concentration; 3 for each lower concentration
Loading: 0.77 g fish/litre, i.e. 7 fish per 3 litres of test medium; 0.33 g fish/litre, i.e. 3 fish per 3 litres of test medium
Illumination: 16 hours photoperiod daily
Aeration: Aeration was introduced after 72 hours of exposure and maintained for 6 hours.
Feeding: No feeding from 24 hours prior to the test and during the total test period
Introduction of fish: Within 10 minutes after preparation of the test media from a holding tank with comparable water quality parameters and pH and temperature differences












Reference substance (positive control):
yes
Remarks:
Pentachlorophenol
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 100 other: %WSF
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
100 other: %WSF
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Details on results:
No LC50 could be calculated because the test substance proved to be non-toxic (LC50 > maximum concentration tested).
Results with reference substance (positive control):
Results acceptable
Sublethal observations / clinical signs:

The measured concentration of octyltin species in the duplicate samples taken from the undiluted WSF showed initial concentrations of 1805 and 849 µg/l. The large variance between duplicate samples together with the slight haziness of the test solutions indicated that the initial concentration was above the solubility limit. Measurements at 24 and 96 hours of exposure showed that actual test concentrations were still above the solubility limit. Note that at the end of the test, a precipitate of test substance was observed in the vessel containing the highest test concentration. Given these results, the effect parameters were expressed in terms of both loading rate (Octyltintris(2-ethylhexyl mercaptoacetate)) and the mean concentration of octyltin species. The mean concentration was calculated to be 945 µg/l.

Validity criteria fulfilled:
yes
Conclusions:
1. No mortality was observed in the control at the end of the test.
2. Test conditions were maintained constant throughout the test.
3. The dissolved oxygen concentration has been at least 60% of the air saturation value throughout the test (>5 mg/L at 22°C).
4. Analysis was performed on the octyltin species in Octyltintris(2-ethylhexyl mercaptoacetate). Results were based on both the loading rate of Octyltintris(2-ethylhexyl mercaptoacetate) and the mean concentration of the octyltin species.
No LC50 could be calculated because the test substance proved to be non-toxic (LC50 > maximum concentration tested).
Executive summary:

The study procedure described in this report was based on the OECD guideline No. 203, 1992. In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.1, 2008, the ISO International Standard 7346-1: Static method, 1996 and the OECD series on testing and assessment number 23, 2000.

The batch of Octyltintris(2-ethylhexyl mercaptoacetate) tested was a clear colourless to light yellow liquid with a purity of 98.00% and the substance was not completely soluble in test medium at the initial loading rate prepared.

Preparation of test solutions started with a loading rate of 100 mg/L applying one day of magnetic stirring followed by a one day stabilisation period to reach maximum solubility of the test substance in the test medium. The slightly hazy and colourless Water Soluble Fraction (WSF) was filtered through glass wool and used as the highest test concentration, which was observed to be still slightly hazy. The lower test concentrations were prepared by subsequent dilutions of the WSF in test medium. These lower test concentrations were clear and colourless.

A combined limit/range-finding test was performed, exposing seven fish per concentration to the WSF prepared at a loading rate of 100 mg/L and to a control group. In addition, three fish per concentration were exposed to 1.0 and 10% of the WSF. The total test period was 96 hours and duplicate samples for analytical confirmation of actual exposure concentrations were taken at the start, after 24 hours of exposure and at the end of the test.

Analysis was performed on the octyltin species in Octyltintris(2-ethylhexyl mercaptoacetate).

The measured concentration of octyltin species in the duplicate samples taken from the undiluted WSF showed initial concentrations of 1805 and 849 µg/L. The large variance between duplicate samples together with the slight haziness of the test solutions indicated that the initial concentration was above the solubility limit. Measurements at 24 and 96 hours of exposure showed that actual test concentrations were still above the solubility limit. Note that at the end of the test, a precipitate of test substance was observed in the vessel containing the highest test concentration. Given these results, the effect parameters were expressed in terms of both loading rate (Octyltintris(2-ethylhexyl mercaptoacetate)) and the mean concentration of octyltin species. The mean concentration was calculated to be 945 µg/L.

The study met the acceptability criteria prescribed by the protocol and was considered valid.

Octyltintris(2-ethylhexyl mercaptoacetate) induced no visible effects in carp exposed to the concentration obtained in a WSF prepared at a loading rate of 100 mg/L (NOEC).

The 96h-LC50 was beyond the concentration obtained in a WSF prepared at a loading rate of 100 mg/L. The mean concentration of organotin species measured in this WSF was 945 µg/L.

Description of key information

No toxicity is expected up to the water solubility limit of MOTE.

Key value for chemical safety assessment

Additional information

The study procedure described in Bouwman' report (2010) was based on the OECD guideline No. 203, 1992. In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.1, 2008, the ISO International Standard 7346-1: Static method, 1996 and the OECD series on testing and assessment number 23, 2000. This study is identified as the key study.

Preparation of test solutions started with a loading rate of 100 mg/L. The lower test concentrations were prepared by subsequent dilutions of the WSF in test medium. These lower test concentrations were clear and colourless.

A combined limit/range-finding test was performed, exposing seven fish per concentration to the WSF prepared at a loading rate of 100 mg/I and to a control group. In addition, three fish per concentration were exposed to 1.0 and 10% of the WSF. The total test period was 96 hours.

The study met the acceptability criteria prescribed by the protocol and was considered valid.

Octyltintris(2-ethylhexyl mercaptoacetate) induced no visible effects in carp exposed to the concentration obtained in a WSF prepared at a loading rate of 100 mg/I (NOEC).

Migchielsen 2004 study is a supporting study, performed in accordance to EC Method C.1. However, the test material only contained 54% of MOTE.

The 96-hour acute toxicity study in zebra-fish on MOT(EHMA) was run as a limit test, which was combined with a range-finding test in a semi-static system with daily renewal. Seven zebra-fish per test group were exposed to a blank control and a WAF testing solution prepared at a nominal MOT(EHMA) loading of 100 mg/L. Migchielsen analytical results could not be relied upon because of tin contamination in the control samples and was therefore rejected. In both cases, no mortality was observed and LC50 were defined as > 100 mg/L WSF. Therefore no toxicity occurs up to the water solubility limit which is expected to be very low. NOEC is defined as 100 mg/L WAF.