Docosanoic acid

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:

08 July - 29 July 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

yes

Remarks:

There were three test concentrations arranged.

GLP compliance:

yes

Remarks:

According to Japanese GLP standard

Analytical monitoring:

yes

Details on sampling:

- Sampling method: Test water was directly sampled by each vessel.
- Sample storage conditions before analysis: No storage before analysis.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test item was mixed with HCO-20 and DMF. And then, deionized water was added to prepare stock solution (250 mg/L).
- Controls: Blank control and vehicle control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): HCO-40 and DMF
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): DMF 5000 mg/L and HCO-40 5000 mg/L in stock solution and DMF 40 mg/L and HCO-40 40 mg/L in final test solution

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/day

ACCLIMATION
- Acclimation period: 2 weeks for parental animals
- Acclimation conditions (same as test or not): Same as test
- Type and amount of food: Chlorella vulgaris, 0.15 mgC/day
- Health during acclimation (any mortality observed): Only healthy stock was used for exposure.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

225 - 275 (as CaCO3) mg/L

Test temperature:

19.9 - 20.6 °C

pH:

7.0 - 8.0

Dissolved oxygen:

6.0 - 8.6 mg/L

Nominal and measured concentrations:

Nominal concentration: 0.3, 0.5 and 1mg/L
Measured concentration: 0.27, 0.49 and 0.84 mg/L (time-weighted mean)

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL beaker
- Type (delete if not applicable): closed with teflon sheet
- Material, fill volume: Glass, 80 mL
- Renewal rate of test solution (frequency/flow rate): three times a week
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- No. of vessels per vehicle control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: same as test

OTHER TEST CONDITIONS
- Adjustment of pH: No adjustment
- Photoperiod: 16 hours in the light and 8 hours in the dark
- Light intensity: < 1200 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Time to first brood production was recorded, mortality of parental daphnia and cumulative number s of juveniles produced per adult alive were observed everyday.

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 5 mg/L
- Results used to determine the conditions for the definitive study:
Acute toxicity test for 48 hours were performed and EC50 was > 5 mg/L.D

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

21 d

Dose descriptor:

LC50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 0.84 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 0.84 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Details on results:

- Mortality of parent animals: See table 1.
- No. of offspring produced per day per female: see table 2.
- Egg development time: 7-10 days in control groups, 7-11 days in 0.3, 0.55 and 1 mg/L

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50: 0.66 mg/L

Reported statistics and error estimates:

Dunnet's and Williams' multicomparison test

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	10	10
Solv. Cont.		0	0	0	0	20	20
0.30	0.27	0	0	0	0	10	10
0.55	0.49	0	0	0	0	20	20
1.00	0.84	0	0	0	0	10	20

Table 2. Cumulative numbers of juveniles produced per adult alive for 21 days

Nominal concentration (mg/L)	Mean (a) measured concentration (mg/L)	Mean Cumulative Numbers of Juveniles ± S.D.	Inhibition Rate (%)	Significant difference
Control		137.4± 11.1
Solv. Cont.		135.9 ± 15.5
0.30	0.27	146.7 ± 12.0	-7.9	-
0.55	0.49	154.9 ± 8.9	-14.0	-
1.00	0.84	137.5 ± 15.0	-1.2	-

(a) time-weighted mean

-: indicates no significant difference.

Validity criteria fulfilled:

yes

Description of key information

No long-term toxicity effects up to the limit of water solubility

Additional information

One study is available on long-term toxicity to aquatic invertebrates for docosanoic acid (CAS 112-85-6). This study was performed according to OECD guideline 211 (GLP). Neonates (age < 24 h) of Daphnia magna were exposed to different concentrations of the test substance (0.0, 0.3, 0.5, 1.0 mg/L, nominal) under semi static conditions for 21 d. Analytical determination of test solution concentration was performed by analyzing docosanoic acid concentrations in the water phase. Time weighted average (TWA) concentrations were calculated for all treatment groups: 0.27, 0.49 and 0.84 mg/L (TWA).

No concentration dependent effects and no significant effects compared to the control group on mortality or reproduction were observed after 21 d up to the highest concentration tested.

Therefore, the EC10 (21 d) for reproduction was > 1.00/0.84 mg/L (nominal/TWA). Thus, no effects on survival and reproduction of Daphnia magna after 21 d of exposure were observed up to the water solubility limit (0.016 mg/L at 25 °C) of docosanoic acid.