Carboxylic acids, C5-9

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Test performed in 2001.

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

Specific details on test material used for the study:

- Name of test material (as cited in study report): n-Heptanoic acid
- Substance type: acid
- Physical state: Liquid
- Analytical purity: >97.7%
- Lot/batch No.: FHH02

Analytical monitoring:

yes

Details on sampling:

The test medium was sampled 1 mL at a time 4 times during the exposure period and before and after water replacement for each test vessel in all testing groups, and analysed by GC after analysis pre-processing. The tested substance of each test fluid was quantitated from the ratio with the standard solution by the internal standard fluid addition method.
Test solutions

Vehicle:

no

Details on test solutions:

Elendt M4 medium (according to OECD 211 guideline)

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Source: Ministry of the Environment, National Institute of Environmental Studies (presently the National Institute for Environmental Studies)
- Feeding during test: yes
- Food type: Chlorella vulgaris
- Amount: 0.2 mg C per daphnia per day
- Frequency: daily

ACCLIMATION
- Acclimation period: 6 weeks
- Acclimation conditions (same as test or not): yes

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

None

Hardness:

Not specified

Test temperature:

20.0-20.6°C (min-max)

pH:

6.1-8.2

Dissolved oxygen:

from 4.3 to 8.8

Salinity:

None

Conductivity:

Not measured

Nominal and measured concentrations:

Nominal concentrations: 0 ; 5 ; 10 ; 20 ; 40 and 80 mg/L. See table 1 for measured concentrations. Nominal concentrations were used for the derivation of the effect concentrations.

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL glass beaker covered by a Teflon sheet
- Renewal rate of test solution (frequency/flow rate): semi-static, 3 times a week
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
Elendt M4

OTHER TEST CONDITIONS
- Adjustment of pH: none
- Photoperiod: 16L:8D
- Light intensity: 800 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): parental mortality, cumulative larvae production

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

40 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other:

Remarks:

Time to first brood

Details on results:

All daphnia died at the highest concentration (80 mg/L). No adverse effect was observed on cumulative larval production until the end of the experiment in the other treatments, except larval production was significantly delayed in the 40 mg/L group. Therefore NOEC was considered as 20 mg/L.

Results with reference substance (positive control):

None

Reported statistics and error estimates:

The 21-day cumulative juveniles per surviving parent for each test vessel was calculated, and the presence of a significant difference between each testing group and the control group was derived by statistical methods and the maximum no observable effect concentration (NOEC) and the lowest observable effect concentration (LOEC) were determined. As the result of Bartlett’s test for homogeneity of variances showed no homogeneity, the Kruskal-Wallis test as well as the non-parametric Dunnett’s multiple comparison test were performed. In the statistical analysis, Yukms Software Statlight “#4 multi-group comparison” (Yukms Corp., Tokyo) was used.

Table 1: Analytical measurements of test item concentrations at days 0, 1, 7, 8, 15, 16 and 17 of the experiment.

Days	0	1	7	8	15	16	16	17
Nominal concentrations (mg/l)	New	Old	New	Old	New	Old	New	Old
Control	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2
5	4.5	4.7	4.6	2.6	3.8	1.5	4.1	1
10	9.8	11.3	8.5	8.4	7.5	5.6	8.4	6.8
20	21.1	20.7	18	17.4	13.8	13.2	16.1	15.1
40	41.1	40.4	42	41.8	35.3	34.8	38.6	40.3
80	75.6	80	*	*	*	*	*	*

* All daphnia dead

Table 2: Time to first broods (in days)

	Nominal concentrations (mg/l)
Vessel	Control	5	10	20	40
1	8	9	8	8	11
2	8	8	8	8	8
3	8	8	7	8	11
4	8	8	8	8	8
5	8	8	8	8	11
6	8	8	8	8	11
7	8	8	8	8	11
8	9	9	8	8	8
9	8	8	8	7	8
10	8	8	8	8	11
Mean	8.1	8.2	7.9	7.9	9.8*
S.D.	0.32	0.42	0.32	0.32	1.55

* Significantly different from the control

Validity criteria fulfilled:

yes

Conclusions:

Daphnia magna was exposed to graded concentrations (0 ; 5 ; 10 ; 20 ; 40 and 80 mg/L) of n-heptanoic acid for 21 days. Adult mortality, cumulative juvenile production and time to first brood were examined. The most stringent outcome was time to first brood with a LOEC of 40 mg/L. Therefore, a NOEC of 20 mg/L was considered.
All validity criteria were fulfilled.

Description of key information

Heptanoic acid (one of the constituents of the target UVCB substance: Daphnia magna: 21-d NOEC: 18 mg/L (OECD 211; NITE, 2009)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

18 mg/L

Additional information

The chronic toxicity to aquatic invertebrates of the constituent heptanoic acid was tested in a reproduction test according to OECD 211. The 21 -d NOEC was determined to be 18 mg/L, the EC50 47 mg/L (NITE, 2009).

Chronic toxicity is therefore not expected.