Hexanoic acid

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-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:

11 September 2002 - 02 October 2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP - Guideline study, tested with the source substance CAS 111-14-8. In accordance to the ECHA guidance document “Practical guide 6: How to report read-across and categories (March 2010)”, the reliability was changed from RL1 to RL2 to reflect the fact that this study was conducted on a read-across substance

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

GLP compliance:

yes

Remarks:

According to Japanese GLP 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 (under test conditions): 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
- Food type: Chlorella vulgaris
- Amount: 0.15 mgC/animal/day

ACCLIMATION
- Acclimation period for parental animals: From 2002/08/14 to 2002/09/11
- Acclimation conditions (same as test or not): Similar to test condition
- Type and amount of food: Chlorella vulgaris, 0.2 mgC/animal/day
- Health during acclimation (any mortality observed): 0% mortality during 2 weeks before study initiation

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

250 - 265 (as CaCO3) mg/L

Test temperature:

20.0 - 20.6 °C

pH:

6.1 - 8.2

Dissolved oxygen:

4.3 - 8.8 mg/L

Nominal and measured concentrations:

Nominal concentration: 5, 10, 20, 40 and 80 mg/L
Measured concentration: 3.5, 8.7, 17.9, 40.3 and 77.8 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL beaker
- Type (delete if not applicable): closed, covered with teflon sheet
- Material, fill volume: glass, 80 mL
- Aeration: No
- Renewal rate of test solution (frequency/flow rate): Test water was changed every 24 hours.
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- M4 medium was used.
- Culture medium different from test medium: Same as test medium

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) :
General condition and mortality of parental animal was observed everyday.
Time to first brood production was recorded.
Cumulative number of juveniles produced per adult alive for 21 days were counted.

VEHICLE CONTROL PERFORMED: no

RANGE-FINDING STUDY: Acute immobilisation test was performed.
- Test concentrations: 72 mg/L
- Results used to determine the conditions for the definitive study: EC50 for 48 hours was 72 mg/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

17.9 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

40.3 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

46.8 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: 43.7 - 77.8 mg/L

Duration:

21 d

Dose descriptor:

LC50

Effect conc.:

52.2 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks:

of parental animals

Remarks on result:

other: 40.3 - 77.8 mg/L

Details on results:

- Mortality of parent animals: See table 1
- No. of offspring produced per day per female: See table 2
- Time to first brood release or time to hatch was within 9 days in cotrol group, 5, 10 and 20 mg/L groups. In 40 mg/L group, it was 9.8 day and sinificant difference was indicated. In 80 mg/L group, parental animals were dead before first brood production.

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 0.89 mg/L

Reported statistics and error estimates:

Binomial test was applied for LC50, logit test for EC50, and Dunnett's multicomparison test for NOEC and LOEC.

Table 1. Mortality (%) of parental Daphnia

Nominal concentration (mg/L)	Mean measured concentration (mg/L)	Days
		1	2	4	7	14	21
Control	-	0	0	0	0	0	10
5	3.5	0	0	0	0	0	0
10	8.7	0	0	0	0	0	0
20	17.9	0	0	0	0	0	0
40	40.3	0	0	0	0	0	10
80	77.8	100	100	100	100	100	100

Table 2. Cumulative number of juveniles produced per adult alive

Nominal concentration (mg/L)	Mean measured concentration (mg/L)	Mean Cumulative Numbers of Juveniles ± S.D.	Inhibition Rate (%)	Significant difference
Control	-	104.4± 7.1	-
5	3.5	142.0 ± 7.3	-36.0	*
10	8.7	145.8 ± 15.8	-39.6	**
20	17.9	161.1 ± 11.3	-54.2	**
40	40.3	92.1 ± 35.2	11.8	V
80	77.8	0	100	++

*,**: Indicates a significant difference (α =0.05, 0.01) from the control. Mean cumulative number for this concentration level was higher than that for control group. It was considered that a test substance (n-heptanoic acid) was nutrition for bacteria and degraded in water. It was concluded that this concentration level did not show adverse effect on Daphnia reproduction.

V: Indicates no significant difference from mean value of the control. However, the variance was significantly (α=0.05) different from the control and its coefficient of variation was remarkably large exceeding 38%. It was concluded that this concentration level showed adverse effect on Daphnia reproduction.

++: Statistical comparison test could not be performed because parental animals were dead.

Validity criteria fulfilled:

yes

Description of key information

NOEC (21 d) = 17.9 mg/L (nominal, OECD 211)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

17.9 mg/L

Additional information

No data on long-term toxicity to aquatic invertebrates are available for hexanoic acid C6 (CAS 142-62-1).

Therefore ecotoxicological effects on aquatic invertebrates are predicted from adequate and reliable data for a source substance 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 C7 was tested according to OECD 211 under GLP-conditions. Daphnids (Daphnia magna) were exposed to 0, 5, 10, 20, 40 and 80 mg/L (nominal, measured values were in the range of 92 – 111% of nominal values) for 21 d. NOEC (21 d) and EC50 (21 d) values of 17.9 mg/L (nominal) and 72 mg/L (nominal) were derived, respectively.