Octanoic acid

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 Jul - 11 Aug 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

yes

Remarks:

, hardness of test water was lower than that recommended by the Guideline

GLP compliance:

yes

Remarks:

according to the Japanese GLP Standard

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 0.20, 0.64, 2.0, 6.4 and 20 mg/L (nominal)
- Sampling method: Test solutions were sampled directly from each test vessel at day 0, 1, 7, 8, 14 and 15.
- Sample storage conditions before analysis: Analysis was conducted immediately after sampling, no storage.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test substance was dissolved in vehicle, and this stock solution was diluted in dilution water and stirred for 1 hour.
- Controls: dilution water with/without vehicle
- Chemical name of vehicle: dimethylformamide
- Concentration of vehicle in test medium : 0.1 mL/L
- Evidence of undissolved material: not observed

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: bred in-house (origin: Incorporated Administrative Agency, National Institute for Environmental Studies, Tsukuba, Japan)
- Age at study initiation: 24 hours
- Feeding during test: yes
- Food type: Chlorella vulgaris
- Amount: 0.1 - 0.2 mg C/day

ACCLIMATION for parental animals
- Acclimation period: < 3 weeks
- Acclimation conditions (same as test or not): same as test
- Type and amount of food: Chlorella vulgaris, 0.1 - 0.2 mg C/day
- Health during acclimation (any mortality observed): only healthy stocks (no mortality and no presence of males and ephippia) were used for the exposure

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

60 - 80 mg/L (as CaCO3)

Test temperature:

19.7 - 20.2 °C (20 ± 1 °C )

pH:

7.9 - 8.4

Dissolved oxygen:

7.2 - 8.8 mg/L (> 60% of saturated oxygen)

Nominal and measured concentrations:

nominal concentrations: 0.20, 0.64, 2.0, 6.4 and 20 mg/L
Measured time-weighted mean during 21 days: -, -, -, 5.3 and 19 mg/L (nominal concentrations were applied, since the low concentrations after exposure were below the detection limit)

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL beaker
- Material, fill volume: glass, 80 mL
- Renewal rate of test solution: once in 24 hours
- No. of organisms per vessel: 1
- No. of vessels per concentration: 10
- No. of vessels per control: 10
- No. of vessels per vehicle control: 10


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: charcoal-treated, dechlorinated and aerated tap water in Takarazuka, Japan
- Alkalinity: 56 mg/L
- Ca/Mg ratio: 19/4.3
- Culture medium different from test medium: same as test medium
- Intervals of water quality measurement: pH, oxygen content, total hardness and temperature of the test solutions were determined at day 0, 1, 7, 8, 14 and 15.

OTHER TEST CONDITIONS
- Photoperiod: 16 : 8 hours day-night regime
- Light intensity: < 1200 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality, reproduction, offspring

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 20 mg/L
- Results used to determine the conditions for the definitive study:
Based on the acute toxicity study, EC 50 was > 20 mg/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate (reagent grade)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

based on cumulative number of juveniles produced per adult

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

0.64 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

based on cumulative number of juveniles produced per adult

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

0.51 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

based on cumulative number of juveniles produced per adult

Duration:

21 d

Dose descriptor:

LC50

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks:

of parental animal

Details on results:

- Mortality of parent animals after 21 days: control: 0%, vehicle control: 10%, 0.20 and 0.64 mg/L: 0%, 2.0 mg/L: 30%, 6.4 mg/L: 40%, 20 mg/L: 50%
- No. of offspring produced per day per female: see table 1
- Number of males and females (parental): 10 females
- Time to first brood release or time to hatch: 7 - 9 days, no statistically significant difference between control and other groups

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: 0.44 mg/L (EC50 for immobility)

Reported statistics and error estimates:

Logistic method for EC50, Non-parametric Dunnett multiple comparison procedure, Two-sided test for NOEC and LOEC.

Table 1: Cumulative numbers of juveniles produced per adult alive for 21-days

Nominal Concentration (mg/L)	Mean Cumulative Numbers of juveniles after 21 Days (Mean ± SD)	Inhibition rate (%)	Significant difference
Control	63.0 ± 23.8	-
Solvent control	67.6 ± 25.0	-7.3
0.20	58.6 ± 21.4	7.0
0.64	4.6 ± 6.6	93	*
2.0	0.4 ± 1.1	99	**
6.4	0.2 ± 0.4	100	**
20	0.2 ± 0.4	100	**

*: Indicates a significant difference (α=0.05) from the control.

**: Indicates a significant difference (α=0.01) from the control.

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Please refer to the category justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

1.294 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

other: reproduction, mortality, growth

Remarks on result:

other: Source: CAS 334-48-5, 2013

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

based on cumulative number of juveniles produced per adult

Remarks on result:

other: Source: CAS 334-48-5, 1999

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

0.64 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

based on cumulative number of juveniles produced per adult

Remarks on result:

other: Source: CAS 334-48-5, 1999

Reference 3

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- three representative 24 h exposure periods per week: Sampling of fresh test solution before distribution to the replicates; Sampling of aged test solution from each test vessel, this samples were pooled for analysis.
- at each sampling point the samples were taken in duplicate, with one sample immediately analysed and the second frozen in case of further analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
A concentrated stock solution of the test substance acid was prepared by dissolving 222.1 mg in 22 mL of acetone as a solvent. An aliquot of 1mL of the acetone containing the test item was added to a hot sterile 2L bottle, the bottle turned to ensure coverage of the bottle walls with the test substance, and the acetone evaporated. Dilution water was then added to a volume of 2 L and the solution stirred at 300 rpm for 20 hours at room temperature (21 ± 1°C). The solution was then left to settle for 2 hours before the first 100 mL was drained and discarded. The remaining eluate solution formed the test loading at 5 mg/L. The control medium was prepared with sterile dilution water. All test media was used within 1-2 hours of final preparation.
A small volume (200 mL) of the eluate was used for rinsing the test vessels in order to saturate the surface before filling the vessels for toxicity testing and analytical measurements.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain/clone: Daphnia magna Straus
- Source: German Federal Environment Agency, Institut für Wasser-, Boden- und Lufthygiene, Germany
- Age of parental stock: at least 3 weeks old
- Feeding during test: yes
- Food type: Desmodesmus subspicatus
- Amount: amount depending on measured optical density and carbon content in the algae (according to a calibration nomograph)
- Frequency: daily

ACCLIMATION
- Acclimation period: 1 week
- Acclimation conditions (same as test or not): yes
- Type and amount of food: algal suspension (Desmodesmus subspicatus) and LiquizellR (HOBBY)
- Feeding frequency: daily

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES:
newborn Daphnia were removed daily

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

21 d

Hardness:

1.0 - 1.1 mmol/L

Test temperature:

20.1 - 20.3 °C

pH:

new test solutions: control: 8.81 - 9.48; 5 mg/L: 8.6 - 9.63
aged test solutions: control: 8.6 - 9.44; 5 mg/L: 8.27 - 9.24

Dissolved oxygen:

new test solutions: control: 5.7 - 8.5 mg O2/L ; 5 mg/L: 8.6 - 9.63 mg O2/L
aged test solutions: control: 7.2 - 11.2 mg O2/L; 5 mg/L: 4.6 - 10.9 mg O2/L

Nominal and measured concentrations:

0 and 5 mg/L (nominal, corresponding to 1.294 mg/L meas.(TWA))

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL glass flasks
- Type: closed (with silicone plugs)
- Material, fill volume: glass flasks, 100 mL
- Aeration: no
- Renewal rate of test solution: daily
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: purified local tap water (filtration with activated charcoal, passage through a lime-stone column, aeration to saturation)
- Total organic carbon: < 2 mg/L
- Metals (copper, iron, manganese and zinc): each < 2 µg/L
- Chlorine: < 0.02 mg/L
- Alkalinity: 2 mmol/L
- Ca/mg ratio: 0.8 mmol/L / 0.2 - 0.3 mmol/L
- Conductivity: 238.1 - 244.5 µS/cm
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: light/dark cycle: 16 h/8 h
- Light intensity: 509 - 528 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Daily: Number of juvenile Daphnia magna from day 6 on. Furthermore: Mortality, abnormalities in appearance, behaviour, condition (including male sex) or presence of winter eggs (ephippium)
- At study termination: body length (excluding the anal spine) of the adults in treatment and control (by digital photography)

VEHICLE CONTROL PERFORMED: no (the vehicle was evaporated before adding of dilution water

RANGE-FINDING STUDY
- Test concentrations: no information given

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

1.294 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

other: reproduction, mortality, growth

Details on results:

- Validity: mean control mortality: 0.0%, mean offspring number: 72.5. Therefore the validity criteria were met.
- Test item concentration (calculation as time weighted average TWA): Where the measured recovery in the solution was less than the LOQ (10 µg/L) then half of the LOQ (0.05 µg/L) was used for the calculation of the TWA. The TWA of the nominal loading 5.0 mg/L was 1.294 mg/L. The TWA of the test item was 25.9% of nominal loading
- Effects on mortality and length:
no adult mortality, juvenile deaths were observed in two replicates of the test loading on day 21
no significant reduction of adult growth (length)
- Effects on reproduction:
age at first brood between days 9 - 10; no significant difference between control and treatment
cumultive number of offsprings: control: 73, treatment: 75; no significant difference between control and treatment

68.1 – 98.9% of the nominal loading of the test substance was determined in the freshly prepared test solutions. The test substance in the aged test solutions decreased during the first 8 days to concentrations below the limit of quantification (10 µg/L).

Description of key information

NOEC (21 d) = 0.2 mg/L, based on reproduction rate of Daphnia magna (OECD 211); RA CAS 334-48-5 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.2 mg/L

Additional information

Two studies, investigating the long-term toxicity of decanoic acid to aquatic invertebrates, were used as read across to octanoic acid, since the two substances are structurally very similar. Due to an increasing toxicity with increasing chain length from octanoic acid (C8) to lauric acid (C12) towards aquatic invertebrates, the used studies conducted with decanoic acid (C10) are considered as a worst case scenario for the toxicity assessment of octanoic acid.

The first study (Ministry of the Environment of Japan, 1999) with the read across substance decanoic acid was conducted according to OECD 211. Daphnia magna was exposed for 21 d to 5 nominal concentrations of 0.20, 0.64, 2.0, 6.4 and 20 mg/L. The test substance was dissolved in dimethylformamid. The media was prepared and replaced daily. The study resulted in a NOEC (21 d) of 0.2 mg/L (nominal) based on the reproduction rate of the test organism.

A further study (2013) was conducted according to OECD 211 and GLP. Daphnia magna as the test organism was exposed for 21 d to a single concentration of 5 mg/L (nominal). The test item was initially dissolved in acetone. The solvent was left to evaporate before setting up the medium. The eluate was prepared under sterile conditions and replaced daily. The test concentrations were monitored throughout the test duration at three representative 24 h exposure periods per week by GC-MS. 68.1 – 98.9% of the nominal loading of the test substance was determined in the freshly prepared test solutions. The test substance in the aged test solutions decreased during the first 8 days to concentrations below the limit of quantification (10 µg/L). Therefore, the time weighted average (TWA) of the measured concentrations was calculated. The study did not show any biological effects on the mobility, reproduction or growth of Daphnia magna resulting in an NOELR (21 d) of 1.294 mg/L (meas., TWA).

In conclusion, based on the current available information, the most sensitive effect value determined was the NOEC (21 d) of 0.2 mg/L (nominal) which was used for further assessment. A test scheduled in cooperation with Fraunhofer Institute IME (FhG) in Schmallenberg/Germany is still ongoing to overcome methodological deficiencies due to rapid decay of the test substance and to verify the hazard assessment.