L-isoleucine

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

K2 score due to read-across.

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
PHYSICO-CHEMICAL PROPERTIES
- Melting point: 302-303°C
- Water solubility (under test conditions): 56.1 g/L at 20°C

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Source: M.B. Ruysbroek B.V., Noordvliet 159, Maassluis, The Netherlands
- Age at study initiation: no data
- Length at study initiation (length definition, mean and SD): 2.2 +/- 0.1 cm
- Weight at study initiation (mean and SD): 0.09 +/- 0.02 g

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

204 mg/L, expressed as CaCO3

Test temperature:

24.2 - 24.7°C

pH:

6.8 - 7.9

Dissolved oxygen:

> 6.8 mg/L

Nominal and measured concentrations:

0 - 1.0 - 1.8 - 3.2 - 5.6 and 10 g/L

Details on test conditions:

TEST SYSTEM
- Test vessel: beaker
- Type: not specified
- Material, size, headspace, fill volume: beaker volume: 2L; fill volume: 1L
- Aeration: yes
- Renewal rate of test solution: daily
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: groundwater from a locality near Linschoten (the Netherlands)
- Total organic carbon: no data
- Particulate matter: no data
- Trace elements: << 1 mg/L
- pH of the medium after aeration 8.0-8.2
- Chemical analysis results:
Na+: 1.19 mmol/L
K+: 0.22 mmol/L
Ca2+: 1.30 mmol/L
Mg2+: 0.74 mmol/L
Cl-: 2.71 mmol/L
SO42-: 0.69 mmol/L

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light / 8 h dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality, condition (swimming behaviour, colour, respiratory function or any other observable morphological or visual behavioural criterion).

TEST CONCENTRATIONS
- Test concentrations: 0 - 1.0 - 1.8 - 3.2 - 5.6 and 10 g/L

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 10 g/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

> 10 g/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

> 10 g/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

> 10 g/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

other: condition

Details on results:

There was no mortality in the control medium or any of the concentrations tested.
No effect on the condition of the fish was observed during the test.

Validity criteria fulfilled:

yes

Conclusions:

L-Valin was not acutely toxic to fish at a nominal concentration of 10 g/L.

Executive summary:

The study addresses the acute toxicity of L-Valine to Brachydanio rerio. The substance was tested under semi-static conditions for a total of 96 hours. Five beakers with 10 fish each were exposed to test solutions containing 1.0; 1.8; 3.2; 5.6 or 10g/L L-Valin, respectively. The test solutions were renewed daily.

After 96 hours, all animals were alive and no effects were observed on their swimming behaviour, colour, respiratory function or any other visual observable morphological or behavioural criterion. Therefore it can be concluded that L-Valin was not acutely toxic to fish at a nominal concentration of 10 g/L.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Source and target substance are both amino acids that differ by one CH2-group.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source substance: L-valine
Target substance: L-isoleucine

3. ANALOGUE APPROACH JUSTIFICATION
Source and target substances have similar physchem properties (water solubility, log Kow) and show very low toxicity and eco-toxicity.

Reason / purpose for cross-reference:

read-across source

Vehicle:

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 11.2 g/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

> 11.2 g/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

> 11.2 g/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

> 11.2 g/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

other: condition

Details on results:

The tabulated results are those for target substance L-isoleucine as recalculated from the source substance L-valine by taking into account the difference in molecular weight:

Example:

LC50 (Valine) > 10.0 g/L
MM (Valine) = 117.15 g/mol
--> 10.0 g Valine = 10.0 g / 117.15 g/mol = 0.085 mol Valine

0.085 mol Isoleucine
MM (Isoleucine) = 131.18 g/mol
--> 0.085 mol Isoleucine * 131.18 g/mol = 11.2 g Isoleucine
LC50 (Isoleucine) > 11.2 g/L

Conclusions:

Source substance L-valine was found to have an LD50 > 10.0 g/L.
Recalculation of this value to take into account the molecular weight difference between source and target substance yields an LD50 > 11.2 g/L for target substance L-isoleucine.

Executive summary:

As no short term toxicity study to fish is available for L-isoleucine, read-across to a short term toxicity study available for L-valine was considered.

For L-valine no effects were observed at the highest tested concentration, leading to an LD 50 > 10.0 g/L.

Recalculation of this value taking into account the difference in molecular weight results in an LD50 > 11.2 g/L for the target substance L-isoleucine.

Description of key information

Acute toxicity to fish is not expected to occur upon exposure to the L-isoleucine based on information available on read-across substance L-valine.

L-valine was found to have an LD50 > 10000 mg/L. Recalculation of this value taking into account the molecular weight of L-isoleucine results in a predicted LD50 value > 11200 mg/L for L-isoleucine.

This is further confirmed by the result of the QSAR (EcoSAR, EpiSuite) that predicted an 96h-LC50 of 70048 mg/L for L-isoleucine.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

11 200 mg/L

Additional information

No test results for L-isoleucine are available. However, read-across to the test results available for structural analogue L-valine is deemed justified based on a comparison of the main factors driving environmental toxicity: pH, water solubility, log Kow and chemical reactivity (functional groups).

- both are essential amino acids that are in the zwitterion state at physiological pH

- the chemical structure differs only in that L-isoleucine has one extra methylene group in the aliphatic side chain

- the pKa values of the α-COOH group is very similar: 2.36 for ILE, 2.32 for VAL

- the pKa values of the α-NH2 group is very similar: 9.60 for ILE, 9.62 for VAL

- the substances both have a high water solubility: 34 - 41 g/L for ILE, 58 g/L for VAL

- the substances both have a low log Kow value: -1.72 for ILE (experimental value obtained from EpiSuite's WSKOW model database), -2.08 for VAL (calculated by EpiWin QSAR)

As the chemical structure and reactivity, and the water solubility, low Kow and pKa values of L-isoleucine and L-valine are almost identical, it can be concluded that read-across for aquatic toxicity information between those 2 substances is acceptable.

The test available for L-valine are carried out according to OECD guidelines and reveals no fish mortality at the highest tested concentrations (10000 mg/L). As a consequence, acute toxicity to fish is not expected to occur upon exposure to the L-isoleucine up to a concentration of 11200 mg/L.

This is further confirmed by the result of the QSAR (EcoSAR, EpiSuite) that predicted an 96h-LC50 of 70048 mg/L for L-isoleucine.