Sodium acrylate

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:

weight of evidence

Study period:

23 Feb 1996 - 15 Mar 1996 (experimental)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP-guideline study with analytical monitoring

Qualifier:

according to guideline

Guideline:

EPA OTS 797.1330 (Daphnid Chronic Toxicity Test)

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Primary stock solutions were prepared fresh on each sample day. Diluter stock solutions of 16000 mg actylic acid/L were prepared by transferring ca. 16.0353 g of the test substance to a 1-L volumetric flask wich was then brought to volume with hard blended water. An injection of 2.5 mL of the diluter stock solution was delivered to the 1-L mixing box by a dual syringe dispenser each time the diluter cycled. This dilution resulted in the nominal concentration of 40 mg acrylic acid/L.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: ABC Laboratories in-house culture
- Age of parental stock: 24 h
- Feeding during test
- Food type: Algal suspension (Selenastrum capricornutum/Ankistrodesmus falcatus), which provided at least 2.0E8 g cells/L per chamber per day.
- Amount/Frequency: 5 mg/L per chamber per day

CULTURE CONDITIONS
- Temperature: 20 ± 2 °C
- Photoperiod: 16 hours light : 8 hours darkness
- Light intensity: 58 - 61 footcandles
- Holding period: Daphnids were fed a suspension of at least one algae species: Selenastrum capricornutum and/or Ankistrodesmus falcatus at least once a day. Along with the algae, the daphnids received an artificial diet (fish food).

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES: To provide test daphnids (<24 hours old), adult daphnids were transferred and isolated the previous day. The adults from this culture had been cultured for 24 days and were considered acceptable with no signs of stress, disease, or physical damage. 240 neonates were removed and impartially placed in groups of ten into vials containing hard blended water (food-free). Acclimation period was not necessary since the culturing and testing parameters of temperature, dilution water, hardness and lightling were the same.

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES: Survival, abnormal effects

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

130 - 160 mg/L as CaCO3

Test temperature:

19.1 - 19.7 °C

pH:

7.3 - 8.5

Dissolved oxygen:

6.4 - 8.7 mg/L

Nominal and measured concentrations:

Nominal test concentrations: Control, 2.5, 5, 10, 20, 40 mg/L
Measured test concentrations: < Minimum Quantifiable Limit, 1.8, 3.8, 8.1, 19, 38 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, total volume: glass beakers, 1 L
- Type of flow-through: 0.5 L proportional diluter system
- Renewal rate of test solution (frequency/flow rate): 4.2 mL/min equivelent to a replacement of 1-L test volume 6.0 times in a 24-hour period
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 1 daphnid/100 mL

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Hard blended water was used as test water. The specific water hardness was obtained by blending ABC Laboratories' well water with well water that had been demineralized by reverse osmosis.
- Total organic carbon: < 1.0 mg/L
- Particulate matter: 0.2 - 1.1 mg/L
- Alkalinity: 148 - 180 mg7L as CaCO3
- Conductivity: 280 - 300 µmhos/cm
- Intervals of water quality measurement: Temperature, dissolved oxygen, pH was measured after 0, 4, 7, 14, 20 days in alternating replicates

OTHER TEST CONDITIONS
- Photoperiod: 16-hour daylight : 8-hour darkness with 30-minute dusk and dawn transition periods .
- Light intensity: 43 - 55 footcandles

EFFECT PARAMETERS MEASURED: Survival, abnormal effects of the adults daphnieds daily; reproduction three times per week

RANGE-FINDING STUDY
- Test concentrations: 6.3, 12.5, 25, 50, 100 mg/L
- Results used to determine the conditions for the definitive study: adverse effects and mortality in all exposure concentrations after 13 days

Reference substance (positive control):

not specified

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

19 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 8.1 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Remarks:

of adult daphnids

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

3.8 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Remarks:

of adult daphnids

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

8.1 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Remarks:

of adult daphnids

Duration:

21 d

Dose descriptor:

other: MATC

Effect conc.:

5.5 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Remarks:

of adult daphnids

Remarks on result:

other: MATC = geometric mean of LOEC and NOEC

Details on results:

- Analytical recovery: The mean measured concentrations of acrylic acid were 1.8, 3.8, 8.1, 19, and 38 mg/L, representing 72, 76, 81, 95, and 95 % of the nominal test concentrations.

Survival:

Survival of Daphnia magna was shown to be significantly affected in the 8.1, 19, and 38 mg/L mean measured test concentrations, as compared to the control, after the 21-day exposure to acrylic acid. The mean measured concentrations of 1.8, 3.8, 8.1, 19, and 38 mg/L had mean percent survivals of 100, 95.0, 65.0, 22.5, and 52.5 %, respectively. The mean percent survival for the control was 95.0. A 21-day EC50 based on immobility was determined to be > 8.1 mg/L.

Time to first brood:

There were no test concentrations shown to be significantly affected for time to first brood when compared to the control. The control, 1.8, 3.8, 8.1, 19, and 38 mg/L test concentrations had mean days to first brood of 8.0, 8.0, 7.8, 8.0, 8.3, and 8.3 days, respectively.

Young per adult reproductive day (YAD):

The mean YAD value for the mean measured concentration of 38 mg/L was shown to be significantly affected when compared to the control. The control, 1.8, 3.8, 8.1, 19, and 38 mg/L test concentrations had mean YAD values of 4.7, 5.2, 5.0, 4.7, 4.3, and 3.4, respectively. All young produced during the study appeared normal.

Length of adult Daphnia:

The mean length of adult Daphnia magna for the mean measured concentration of 38 mg/L was shown to be significantly affected when compared to the control. The control, 1.8, 3.8, 8.1, 19, and 38 mg/L test concentrations had mean lengths of 4.0, 4.2, 4.1, 4.0, 3.9, and 3.7 mm, respectively.

Weight of adult Daphnia:

There were no test concentrations shown to be significantly affected for weight when compared to the control. The control, 1.8, 3.8, 8.1, 19, and 38 mg/L test concentrations had mean weights of 0.52, 0.64, 0.68, 0.69, 0.52, and 0.50 mg, respectively.

Based on Daphnia length, a NOEC and a LOEC of 19 mg/L and 38 mg/L were determined, respectively. Staples et al. (2000) calculated on the basis of these two values a MATC of 27 mg/L.

Validity criteria fulfilled:

yes

Description of key information

Based on data for the structural analogue acrylic acid, sodium acrylate is chronic toxic to aquatic inveretebrates with a NOEC of 3.8 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

3.8 mg/L

Additional information

No experimental data on the test substance is available. Sodium acrylate (NaA) is dissociating fast in aqueous media (Henderson – Hasselbach calculation). Therefore, the evaluation of the endpoint long term toxicity to aquatic invertebrates is based on a weight of evidence approach using the data of the structural analogue acrylic acid (AA) (CAS 79-10-7) (for WoE information, see chapter 13.2).

A 21-day chronic study with Daphnia magna was conducted under flow-through conditions according to EPA OTS 797.1330 and GLP regulations (BAMM, 1996). The study was rated highly reliable (Klimisch score 1) due to good data quality and high adequacy. Daphnids younger than 24 h were exposed to the mean measured test concentrations of 1.8, 3.8, 8.1, 19, 38 mg/L and a control. Survival and abnormal effects were controlled daily and the reproduction was checked three times a week. Based on the statistical endpoint of adult mean survival from this 21-day Daphnia magna chronic toxicity study, the LOEC was determined to be 8.1 mg/L and the NOEC = 3.8 mg/L. The EC50 (21 d) based on immobility/mortality of adult daphnia was determined to be > 8.1 mg/L. The parameters length and weight of the adult daphnids were not affected significantly by the test substance at any tested concentration. The NOEC for reproduction was based on the parameter YAD (Young per adult reproductive day) and determined to be 19 mg/L; the corresponding LOEC (reproduction) was 38 mg/L. The time for the first brood of the exposed test organisms did not significantly derive from the control.

Another long-term study with Daphnia magna according to OECD Guideline 211 (Daphnia magna Reproduction Test) and GLP regulations was conducted in a semi-static experimental set up for 21 d (Huels, 1995) The analytical measurements were conducted in a separate test vessel and were only conducted after 24 and 48 h by spectophotometrical measurements. Therefore, the study was rated as reliable with restrictions (Klimisch score 2). The study is adequate to support other information. The recovery rate was > 80 %. Therefore, effect values were based on nominal concentrations. The test organisms were expose to a control and the nominal test concentrations 1, 2.5, 5, 10, 20 and 40 mg/L .The NOEC for maternal survival was determined to be 7 mg/L, the NOEC for reproduction based on young per adult was 12 mg/L (nominal).

The NOEC for both studies was within the same range and indicate no chronic toxicity, Due to higher reliability the NOEC from the flow-through system study (BAMM, 1996) with AA is chosen to assess the chronic potential of NaA to aquatic invertebrates. Since AA in general has a higher toxicity potential than NaA, this can be seen as worst-case assumption.