Dodecamethylpentasiloxane

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-04-29 to 2008-05-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling: Samples were collected from one test chamber of each treatment and control group four days and two days prior to the start of the test after conditioning the diluter for approximately 45 and 96 hours respectively. Water samples were collected from alternating replicate test chambers in each treatment and control group at the beginning of the test and at 48 and 96 hours (+/-1 hour) to measure concentrations of the test substance. The samples were collected were collected from mid-depth into a 100 ml glass volumetric flask and analysed immediately.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A primary stock was prepared by mixing a calculated amount of test substance into HPLC-grade dimethyl formamide (DMF) at a nominal concentration of 10 μg/ml. An aliquot of the primary stock solution was diluted with DMF to create a secondary stock solution at a concentration of 700 ng/l. Four additional stock solutions were prepared in DMF at nominal concentrations of 44, 88, 180 and 350 ng/ml. The stock solutions were mixed by inversion and appeared clear and colourless. Stock solutions were stored refrigerated in glass amber bottles or a 500 ml graduated cylinder, and aliquots of each stock were placed in the syringe every two days of the study.

The five test substance stock solutions were injected into the diluter mixing chambers at a rate of 20 μl/minute) where they were mixed with dilution water delivered at a rate of 200 mL/minute to achieve the desired test concentrations. The negative control received dilution water only. The solvent control was prepared by delivering HPLC-grade DMF to the mixing chamber for the solvent control. The DMF concentration in the solvent control and all L5 treatments was 0.1 ml/l.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Test fish:  Total Length 5.0 cm (Range 4.5 to 5.3 cm)/Wet Weight 0.94 g (Range 0.65 to 1.2 g).

- Pre-experiment holding period: 14 days

- Holding conditions: Similar to test conditions

- Feeding during holding: The fish were fed daily with a commercially-prepared diet supplied by Zeigler Brothers Inc., Gardners, PA., USA. The fish were not fed for two days prior to the test or during the test.

- Test loading: 0.065 g/L/day over 24 hours (flow through), 0.63 g/L (instantaneous).

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

Hardness 132 mg/L as CaCO3, Alkalinity 178 mg/L as CaCO3

Test temperature:

12+/-1ºC

pH:

8.0-8.2

Dissolved oxygen:

≥7.2 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: Negative Control, Solvent Control, 4.4, 8.8, 18, 35 and 70 ng/L

Mean measured concentrations in treatments: 2.7, 7.5, 13.2, 35.1 and 75.1 ng/L.

Mean measured concentrations in treatments as a percentage of nominal: 61, 85, 73, 100 and 107%

The results are interpreted with reference to mean measured concentrations.

Details on test conditions:

- Exposure vessel type: 25-L Teflon-lined stainless steel aquaria containing 15-L of test solution. The water depth was approximately 18 cm.

- Number of replicates, fish per replicate: Two replicates per treatment, 10 Fish per replicate

- Dilution water source: Fresh water obtained from a well approximately 40 m deep. The water was passed through a sand filter to remove particles approximately 25 μm in diameter and was aerated. Prior to use the water was again filtered (0.45 μm) and passed through a UV steriliser to remove microorganisms.

- Dilution water chemistry: Hardness 132 mg/L as CaCO3, Alkalinity 178 mg/L as CaCO3, Conductivity 323  mhos/cm      

- Vehicle/solvent and concentrations: The solvent control and treatment groups contained 0.1 mL/L DMF

- Water chemistry in test: DO, pH and temperature measured in each test chamber daily

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 75 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 75 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

No mortalities or other signs of toxicity were observed in any treatment

Reported statistics and error estimates:

There was no significant mortality in any treatment; statistical analysis was therefore not required.

Sublethal observations / clinical signs:

Table 1. Test results

Nominal concentration (ng/l)	Mean measured concentration (ng/l)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	-	0	0	0	0
0 (Vehicle control)	-	0	0	0	0
4.4	2.7	0	0	0	0
8.8	7.5	0	0	0	0
18	13.2	0	0	0	0
35	35.1	0	0	0	0
70	75.1	0	0	0	0

       

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 value of >75 ng/L and NOEC of ≥75 ng/L have been determined for the effects of the substance on mortality of Oncorhynchus mykiss. The results have been obtained under flow-through conditions and are expressed relative to mean measured concentrations of the substance.

Description of key information

(96 hour) LC₅₀: >75 ng/l mortality Oncorhynchus mykiss, reliability 1.

Additional information

A 96 hour LC₅₀ value of >75 ng/l and NOEC of ≥75 ng/l have been determined for the effects of the substance on mortality of Oncorhynchus mykiss. The results have been obtained under flow-through conditions and are expressed relative to mean measured concentrations of the substance.