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Ecotoxicological information

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:
2002-06-10 to 2002-07-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Control and all test concentrations containing surviving fish at 0, 24, 48 and 72 hours in fresh media and at 24, 48, 72 and 96 hours in old media.

- Sample storage conditions before analysis: The samples were extracted immediately after collection.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The test media were prepared by direct dispersion of the test substance in in the dilution water. Amounts of the test substance (0.16, 0.28, 0.50, 0.90 and 1.60 g) were separately dispersed in 20 L of dechlorinated tap water with the aid of propeller stirrers for approximately 5 minutes to give the treatment series of 8.0, 14, 25, 45 and 80 mg/L.

- Controls: Dechlorinated tap water
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
TEST ORGANISM

- Common name: Rainbow trout

- Source: Parkwood trout farm, Wigmoor, Kent, U.K.

- Length at study initiation (length definition, mean, range and SD): 4.2+/-0.2 cm

- Weight at study initiation (mean and range, SD): 0.61+/-0.11 g

- Feeding during test: none


ACCLIMATION

- Acclimation period: 7 days

- Acclimation conditions: same as test

- Type and amount of food: Commercial trout pellets

- Feeding frequency: daily until the day prior to the test.

- Health during acclimation (any mortality observed): approximately 2% mortality in 7 days prior to test.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
100 mg/L as CaCO3
Test temperature:
14ºC
pH:
7.3-7.4
Dissolved oxygen:
9.6-9.9 mg/L
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: 0 (Dilution water control), 8.0, 14, 25, 45 and 80 mg/L.

Mean measured concentrations in the 24-hour old treated media: 4.47, 6.07, 11.89, 21.87 and 37.80 mg/L. The reduction in concentration is attributed to the hydrolysis of the substance and adsorption to the test vessel.

The mean measured concentrations ranged beween 43 and 56% of the nominal concentrations.

The results are interpreted with reference to nominal and mean measured concentrations.
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type: covered
- Material, size, headspace, fill volume: Glass, 20 litres with 20 L of test medium
- Aeration: continuously via narrow bore tube
- Renewal rate of test solution (frequency): daily
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): 1
- Biomass loading rate: 0.31 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dechlorinated tap water
- Total organic carbon: 1 mg/l
- Chlorine: 0.22 mg/l (total)
- Conductivity: 382 μS/cm
- Culture medium different from test medium: no
- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light, 8 h dark with a 20 minute transition period.
- Light intensity: not reported

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mortality after 3, 6, 24, 48, 72 and 96 hours

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8
- Range finding study
- Test concentrations: 1, 10 and 100 mg/L and 3.2 and 32 mg/L and 50 and 80 mg/L
- Results used to determine the conditions for the definitive study: no mortality at nominal concentrations of ≤32 mg/L but mortalities at the higher concentrations.
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
14 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is likely to have been to a mixture of test substance and hydrolysis products
Basis for effect:
mortality (fish)
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
9.1 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
but exposure is likely to have been to a mixture of test substance and hydrolysis products
Basis for effect:
mortality (fish)
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
6.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Remarks:
Mean measured concentrations of test material in 24-hour old test media. However exposure is likely to have been to a mixture of test substance and hydrolysis products.
Basis for effect:
mortality (fish)
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is likely to have been to a mixture of test substance and hydrolysis products
Basis for effect:
mortality (fish)
Remarks on result:
other: 40-60
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
35 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
but exposure is likely to have been to a mixture of test substance and hydrolysis products
Basis for effect:
mortality (fish)
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
24 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Remarks:
Mean measured concentrations of test material in 24-hour old test media. However exposure is likely to have been to a mixture of test substance and hydrolysis products.
Basis for effect:
mortality (fish)
Remarks on result:
other: 20-29
Details on results:
- Mortality of control: 0

- Other adverse effects control: none
Reported statistics and error estimates:
LC50 values and associated confidence intervals were calculated by the moving average method of Thompson (1947).
Sublethal observations / clinical signs:

Table 1. Results of analysis of test media

 Nominal concentration of test substance (mg/l)  Mean measured concentration of substance in 24 -hour old test media (mg/l) Mean measured concentration as percentage of nominal
0 (Control) - -
8.0 4.47 56
14 6.07 43
25 11.89 48
45 21.87 49
80 37.80 47

Table 2. Test results

 Nominal concentration of test substance (mg/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
8.0 0 0  0
14 0 0  0
25 0 0  0 0
45 30 30  30 30
80 100 100 100  100 

Geometric means have been calculated from the reviewer based on the measured concentrations at the start of the test/after each water renewal and 24 h after the water media renewal. The average of the geometric means of measured concentrations in fresh and 24 -h old media are presented in the table below.

Table 3. Geometric means of measured concentrations.

 Nominal concentrations (mg/l)  Geometric mean (mg/l)  Factor
 8  6.02  1.31
 14  9.14  1.53
 25  17.28  1.45
 45  31.37  1.43
 80  55.45  1.44

The LC50 geometric mean has been calculated based on the above factors. Therefore the LC50 nominal value of 50 mg/l has been divided by a factor of 1.4 to determine an LC50 geometric mean value of 35 mg/l.

Validity criteria fulfilled:
yes
Conclusions:
A 96-h LC50 value of 50 mg/L , equivalent to a geometric mean measured value of 35 mg/l, and NOEC of 14 mg/, equivalent to a geometric mean measured value of 9.1 mg/l, have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss based on nominal concentrations. When expressed in terms of mean measured concentrations of the substance in the 24-hour old test media the corresponding values were 24 and 6.1 mg/L. The test substance hydrolyses in water and it is likely that the test organisms were exposed to a mixture of test substance and hydrolysis products.

Description of key information

(96-h) LC50 24 mg/l (parent substance), O. mykiss

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
24 mg/L

Additional information

A 96-h LC50 value of 50 mg/L, nominal, equivalent to a geometric mean measured value of 35 mg/l, NOEC of 14 mg/L, nominal, equivalent to a geometric mean measured value of 9.1 mg/l, have been determined for the effects of the parent test substance on mortality of Oncorhynchus mykiss. When expressed in terms of mean of the geometric mean measured concentrations taking into consideration the substance in the 24-hour old test media the corresponding values were 24 and 6.1 mg/L. The test substance hydrolyses in water and it is likely that the test organisms were exposed to a mixture of test substance and hydrolysis products. The parent substance is thought to be more toxic than the silanol hydrolysis product. While there are no data to confirm this assumption, it is supported by the pattern of observed effects, i.e. no further toxicity was observed beyond the initial 24 hours of exposure, where the organisms would have been predominantly exposed to the parent substance. This interpretation is consistent with the estimated log Kow values of the substance and hydrolysis product, 4.3 and 1.9 respectively.

This is the most conservative reliable value and has been selected as key. Other study reports have determined LC50 values in the range 75-77 mg/l.