Hexanoic acid

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

03 September 2002 - 05 September 2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

The pH was not in the range of 6 to 9.

GLP compliance:

yes

Remarks:

according to Japanese standard

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Melting point: -10/-7 °C
- Boiling point: 223 °C
- Vapour pressure: 1 mmHg at 78 °C, 10 mmHg at 113.2 °C, 100 mmHg at 160 °C
- Water solubility: 2410 mg/L at 15 °C

Analytical monitoring:

yes

Details on sampling:

- Sampling method: 1 mL of test water was directly sampled by each vessel.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test item was dissoved in water. Stock solution was 100 mg/L. Each concentration was prepared by diluting stock solution.
- Controls: Blank control
- Evidence of undissolved material (e.g. precipitate, surface film, etc): Apperance of test water was clear colorless in all concetration.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Source: Incorporated Administrative Agency, National Institute for Environmental Studies, Tsukuba, Japan
- Age at study initiation (mean and range, SD): within 24 hours
- Feeding during test: No food during test

ACCLIMATION
- Acclimation period: From 13 August to 3 September 2002
- Acclimation conditions (same as test or not): Same as test
- Type and amount of food: Chlorella vulgaris, 0.2 mgC/animal/day
- Health during acclimation (any mortality observed): Mortality of parental animal was 0% during 2 weeks before exposure

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20.2 - 20.4 °C

pH:

5.7 - 8.1

Dissolved oxygen:

8.2 - 8.8 mg/L

Nominal and measured concentrations:

Nominal concentration: 10, 18, 32, 56 and 100 mg/L
Measured concentration: 9.19, 19.2, 31.6, 58.7 and 111 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Beaker
- Type: closed with teflon sheet
- Material, size, headspace, fill volume: Glass, 100 mL
- Renewal rate of test solution (frequency/flow rate): Water was changed every 24 hours.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Elendt M4 medium was used.
- Culture medium different from test medium: Same as test

OTHER TEST CONDITIONS
- Adjustment of pH: No adjustment
- Photoperiod: 16 hours in the light, 8 hours in the dark
- Light intensity: < 800 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Immobility was observed at 24 and 48 hours.

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Range finding study: Performed
- Test concentrations: 1, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study:
Immobility after 24 hours and 48 hours was 0% in control, 1 and 10 mg/L group. Immobility was 100% in 100 mg/L group.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

72 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 56 - 100 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Mortality of control: 0%

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: 0.89 mg/L

Reported statistics and error estimates:

Binomial method

Table 1.The number of immobilized Daphnia magna

Nominal Concentration (mg/L)	Cumulative Number of immobilized Daphnia (Percent Immobility)
	24 Hour	48 Hour
Control	0 (0)	0 (0)
10	0 (0)	0 (0)
18	0 (0)	0 (0)
32	0 (0)	0 (0)
56	1 (5)	1 (5)
100	20 (100)	20 (100)

Validity criteria fulfilled:

yes

Description of key information

EC50 (48 h) = 72 mg/L (nominal, D. magna, OECD 202)
LC50 (48 h) = 235 mg/L (nominal, H. plumulosa; no guideline followed)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

72 mg/L

Marine water invertebrates

Marine water invertebrates

Dose descriptor:

LC50

Effect concentration:

235 mg/L

Additional information

No data on freshwater short-term toxicity to aquatic invertebrates are available for hexanoic acid C6 (CAS 142-62-1), only a study on short term toxicity on Hyale plumulosa in marine water is available, which is used as supporting information.

Therefore ecotoxicological effects on freshwater aquatic invertebrates are predicted from adequate and reliable data for source substance(s) by read-across to the target substance within the group applying the group concept in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006.

Due to an increasing toxicity with increasing chain length from hexanoic acid C6 to decanoic acid C10 for aquatic invertebrates read across is performed to heptanoic acid C7 (CAS 111-14-8) since this substance is the most structurally related one in comparison to hexanoic acid.

In the study provided from the Ministry of the Environment, Government of Japan (2002), heptanoic acid was tested according to OECD 202 under GLP-conditions. Daphnids (Daphnia magna) were exposed to 0, 10, 18, 32, 56 and 100 mg/L (nominal, measured values were in the range of 92 – 111% of nominal values) and an EC50 (48 h) of 72 mg/L (nominal) was derived.

As already mentioned a supporting study on hexanoic acid in marine water is available (Onitsuka et al., 1989). Gammarids (Hyale plumulosa) were exposed for 48 h in artificial seawater and an LC50 of 235 mg/L was stated.