Sodium acrylate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

04 July - 07 July 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP guideline study with analytical monitoring

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: control, 10 mg/L, 100 mg/L, 100 mg/L neutralised

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Test substance concentration in the stock solution: 125 mg/L in deionised water

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: green alga
- Strain: SAG 86.81
- Source (laboratory, culture collection): obtained at regular intervals from SAG (Collection of algal cultures in Göttingen) and is kept in liquid culture in the Laboratory of Experimental Toxicology and Ecology

STOCK CULTURE
- Initial cell density: 10000 cells/mL
- Growing duration: weekly passage

PRE CULTURE
- Initial cell density: 10000 cells/mL
- Growing duration: 72 h

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23 ± 2 °C

pH:

uninoculated (0 h): 7.2 - 7.9; pH of 100 mg/L without pH adjustment = 4.5; pH of 100 mg/L with pH adjustment = 7.7
uninoculated (72 h): 8.0 - 8.1; pH of 100 mg/L without pH adjustment = 4.6; pH of 100 mg/L with pH adjustment = 8.1
inoculated (72 h): 7.7 - 10.0; pH of 100 mg/L without pH adjustment = 4.6; pH of 100 mg/L with pH adjustment = 7.7

Nominal and measured concentrations:

Nominal test concentrations: control, 0.0078, 0.016, 0.031, 0.063, 0.13, 0.25, 0.5, 1, 10, 100 (not neutralised), 100 (neutralised) mg/L
Recovery rates (uninoculated; 0 h): 97 - 100 %
Recovery rates (uninoculated; 72 h): 94 - 99.3 %
Revovery rates (inoculated; 72 h): 96.7 - 101 %

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, total volume, fill volume: glass beakers, 250 mL, 100 mL
- Initial cells density: 10000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised water
- Culture medium different from test medium: no
- Intervals of water quality measurement: pH measurement after 0 and 72 h in a uninoculated replicate and after 72 h in an inoculated replicate

OTHER TEST CONDITIONS
- Adjustment of pH: yes, the 100 mg/L test solution
- Photoperiod: permanent
- Light intensity and quality: 120 µE/m*m*s; universal white (Osram L25)

EFFECT PARAMETERS MEASURED: cell growth and biomass after 0, 24, 48, 72 hours
- Chlorophyll measurement: fluorecence of Chlorophyll a at 685 nm

Reference substance (positive control):

not specified

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.03 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.13 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

0.24 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.016 mg/L

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.01 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.04 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

0.12 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

 - Analytical recovery:

		Recovery [%]
Time [h]		Control	Test	Stock solution
0	uninoculated	< LOD	97.0 – 100.0	98.2
72	uninoculated	< LOD	94.0 – 99.3	98.6
72	inoculated	< LOD	96.7 – 101.0	-

The validity criteria were maintained:

Factor of cell division (cell count) after 72 hours: 53.3

Validity criteria fulfilled:

yes

Description of key information

Very acute toxic to aquatic algae and toxic with long lasting effects based on data of the structural analogue acrylic acid.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.13 mg/L

EC10 or NOEC for freshwater algae:

0.03 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 toxicity to aquatic algae 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).

An acute toxicity study was conducted with the freshwater species Desmodesmus subspicatus(BASF AG, 1994) according to EU Method C.3 (algal inhibition test) using a static test system. Nominal exposure concentrations were 0.0078, 0.016, 0.031, 0.063, 0.13, 0.25, 0.5, 1, 10, 100 (not neutralized) and 100 (neutralized) mg/L. Analytical recovery rates were between 94 - 101 % of nominal concentrations. Therefore, all effect values were based on nominal test substance concentrations. Due to the experimental quality and the high reliability of the study it was rated as highly reliable without restriction (Klimisch score 1).  The 72-h effect concentration values based on the growth rate were: EC50 = 0.13 mg/L and EC10 = 0.03 ng/L. The NOEC and LOEC were determined to be 0.008 and 0.016 mg/L, respectively.

In addition, there is another toxicity study with the freshwater species Desmodesmus subspicatus conducted according to EU Method C.3 (algal inhibition test) in compliance with GLP using a static design (Huels, 1995). Since the analytical recovery rates were >80 %, all effect values were based on nominal concentrations. The 72-hour effect concentration values based on the growth rate values were as follows: EC50 = 0.205 mg/L. The NOEC was determined to be <0.01 mg/L. The EC50 was slightly higher than in the other algae study (EC50 = 0.13 mg/ L, BASF AG, 1994) Since the effect concentrations of both studies are based on different types of values (nominal and measured) the results can be considered similar and reliable.

To support these findings another experimental study with Selenastrum capricornutum according to GLP regulations and the guidelines EPA OTS 797.1050 and OECD Guideline 201 using a static design (BAMM, 1990).^. Nominal exposure concentrations were 0.13, 0.25, 0.5, 1.0, 2.0 mg/L. At time 0, the analyzed concentrations were 0.15, 0.26, 0.49, 0.96, 1.9 mg/L. After 96 h, analyses of the test media were all below the limit of detection. The loss of acrylic acid was related to volatility and/or adsorption to the vessels and the algae. Since such a loss of test substance did not occur in any of the other freshwater algae tests, this study is rated as valid with restrictions (Klimisch score 2) but appropriate to support other information. Growth inhibition of algae was observed at all concentrations from 24 h. Based on cell counts, the 72 and 96 h EC50 values were 0.14 and 0.17 mg/L (nominal), respectively. The 96-h NOEC was < 0.13 mg/L. In conclusion the EC50 (72 h) of 0.13 mg/L (BASF AG, 1994) can be considered the most sensitive endpoint and indicates an acute toxicity of AA to aquatic algae. Since NaA is dissociating fast in water and acrylic acid is forming in dependency of the pH value, data from AA can be used to assess the toxicity of NaA. Toxicological studies indicate a general higher toxicity of AA than NaA. Therefore, the toxicity of NaA is probably overestimated by using the data of AA.