2-butyloctanoic acid

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2022-02-07 to 2022-02-11

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:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The test concentrations for the study were 0 (control), 2.13, 4.7, 10.3, 22.7 and 50 mg/l (nominal test loading rates). The test concentrations were determined from a range finding test. At the start (0-hour) of the test the excess test solutions were sampled and at the end of the test (48-hour) one replicate of the dilution water control and each test loading rate was sampled.

Vehicle:

no

Details on test solutions:

STOCK AND TEST SOLUTION AND THEIR PREPARATION
- Dispersion: no
- Vehicle, solvent: no
- Concentration of vehicle/ solvent: not applicable
- Other procedures: A stock solution was prepared by mixing of 0.2 g/l test substance with synthetic freshwater, stirring for 24 hours and subsequently filtering.
STABILITY OF THE TEST CHEMICAL SOLUTIONS: No stability test was performed.

Test organisms (species):

Daphnia magna

Details on test organisms:

- Strain: Daphnia magna straus; CCAP 278/4
- Source/supplier: laboratory bred
- Breeding method: The females were maintained in Elendt's M4 medium in 2 l glass vessels with a working volume of 1.6 L. A photoperiod of 16 hours light:8 hours dark, with 20-minute transition periods was provided. The parent animals were 21 ± 1 days old and had been maintained with a twice weekly renewal of reconstituted water medium since birth. The test organisms were obtained from healthy cultures with no evidence of stress such as high mortality, presence of males or ephippia, delays in the production of the first brood or discoloured animals before the test period.
- Age: not older than 24 hours
- Feeding: on a mixed diet of Pseudokirchneriella subcapitata, strain CCAP 278/4 and yeast, cereal, trout-flake
- Pretreatment: Females were separated from the offspring 24 hours before the start of the test. The offspring produced overnight are transferred into the test water.
- Feeding during test: no
- Control group: 4 replicates with 5 animals each in synthetic freshwater

Test type:

static

Water media type:

freshwater

Total exposure duration:

48 h

Test temperature:

19.5 -20.8 ° C

pH:

7.64 - 7.89

Dissolved oxygen:

8.44 - 8.74 mg O2/L

Nominal and measured concentrations:

The loading rates of 2-butyloctanoic acid in the test solutions at the beginning of the test ranged between 82 - 90 % of the nominal loading rates. At the end of the test, the measured loading rates ranged between 84 – 92 % of the nominal loading rates. The measured concentration in the dilution water control was

Details on test conditions:

DILUTION WATER
- Source: reconstituted freshwater medium
- Aeration: no
- Alkalinity: 41.4 mg CaCO3/L
- Hardness: 234 mg CaCO3/L
- Salinity: not mentioned
- TOC: <3 mg/L
- Ca/Mg ratio: not mentioned
- Na/K ratio: not mentioned
- TSS: not mentioned
- pH: 7.72
- Oxygen content: not mentioned
- Conductance: 603 μS/cm
- Holding water: synthetic freshwater
TEST SYSTEM
- Test type: static
- Concentrations: 0 (control), 2.13, 4.7, 10.3, 22.7 and 50 mg/l (nominal test loading rates)
- Renewal of test solution: no
- Exposure vessel type: Glass beakers of 250 mL nominal capacity
- Number of replicates, individuals per replicate: 4 replicates, 5 animals per replicate
- Test temperature: 19.5 - 20.8 °C
- Dissolved oxygen: 8.44 - 8.74 mg O2/L
- pH: 7.64 - 7.89
- Adjustment of pH: no
- Photoperiod: test was performed in a photoperiod of 16 hours light: 8 hours dark, with 20 minute dusk and dawn transition periods
- Intensity of irradiation: not applicable
DURATION OF THE TEST: 48 hours
TEST PARAMETER: immobilisation, pH value, dissolved oxygen
SAMPLING: after 24 and 48 hours
MONITORING OF TEST SUBSTANCE CONCENTRATION: The measured analytical value of the test solution at the beginning of the test ranged between 82 - 90 % of the nominal loading rates, and at the end of the test, the measured concentrations ranged between 84 – 92 % of the nominal loading rates.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

41.7 mg/L

95% CI:

34.1 - 50.9

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other:

Details on results:

- concentration / effect data (Immobilisation, percent immobilized)
(mg/l) 24h 48h
0 0 0
2.13 0 0
4.70 0 0
10.3 0 0
22.7 0 0
50.0 40 65

Validity criteria fulfilled:

yes

Remarks:

no immobility or other signs of stress were observed in the control and dissolved oxygen concentration remained at ≥ 3 mg/L

Conclusions:

The 48h-EL50 was 41.7 mg/l (95% confidence interval between 34.1 and 50.9 mg/l).

Executive summary:

In an OECD 202 -study the 48h-EL50 of 2 -butyl octanoic acid was 41.7 mg/l (95% confidence interval between 34.1 and 50.9 mg/l).

Description of key information

In the key study (Daphnia magna, OECD 202, GLP compliant) with 2-butyloctanoic acid the 48h-EL50 was 41.7 mg/l (95% confidence interval between 34.1 and 50.9 mg/l). In the ECOSAR calculation a value of 48 h-EC50 of  9.363 mg/L is predicted. 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

41.7 mg/L

Additional information

In the key study (Daphnia magna, OECD 202, GLP compliant) with 2-butyloctanoic acid the 48h-EL50 was 41.7 mg/l (95% confidence interval between 34.1 and 50.9 mg/l). In the ECOSAR calculation a value of 48 h-EC50 of 3.585 mg/L is predicted.

Acute toxicity in Daphnia magna with the similar substance Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid was tested according to OECD guideline No. 202. The study met the acceptability criteria and was conducted GLP compliant, therefore considered reliable without restrictions. The 48h-EC50 was 16 mg/L based on average exposure concentrations (95% confidence interval between 13 and 19 mg/L) and thus confirming the range of toxicity to invertebrates.