Ethyl 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:

key study

Study period:

10 Mar - 14 Mar 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP-Guideline study with acceptable restrictions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

96-h instead of 72-h test duration

Principles of method if other than guideline:

The study was conducted according to U.S . EPA-TSCA, 40 CFR, Part 797; Guideline 797.1050 (1985), and OECD Guideline 201.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 6.5, 13, 25, 50 and 100 mg/L
- Sampling method: Analytical samples were taken from the parent solutions of each concentration at 0-hour. All replicates were used at 96-hours for analytical confirmation of test concentrations.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The definitive test concentrations were prepared directly in 1000 mL volumetric flasks as proportional dilutions of a 2000 mL solution of the highest test concentration, 100 mg/L. The 100 mg/L working standard was prepared by adding an appropriate amount of compound directly to the sterile medium.
- Eluate: no
- Differential loading: no
- Controls: negative control
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Selenastrum capricornutum
- Batch: Batch #1648
- Source (laboratory, culture collection): The Department of Botany, Culture Collection of Algae, The University of Texas at Austin, Texas
- Age of inoculum (at test initiation): 48 h


ACCLIMATION
- Culturing media and conditions (same as test or not): same as test
- Any deformed or abnormal cells observed: no

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

no data

Test temperature:

23 - 24 °C

pH:

6.9 to 7.6

Dissolved oxygen:

no data

Salinity:

no data

Nominal and measured concentrations:

Nominal test concentrations: 6.5, 13, 25, 50 and 100 mg/L
0 hour test concentrations: 5.9, 11, 23, 47 and 99 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 250 mL-Erlenmeyer flasks, 100 mL medium
- Aeration: yes (by constant shaking at 100 rpm)
- Initial cells density: approximately 1.0E+4 cells/mL (nominal); 7.0E+3 cells/mL (counted)
- Control end cells density: 1.4E+6 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3


GROWTH MEDIUM
- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reverse-osmosis water, sterilised


OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH: yes
- Photoperiod: 24 h
- Light intensity and quality: continuous "cool-white" fluorescent light (approx. 4300 Lux)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:The algal cell counts were accomplished utilizing a hemacytometer and an Olympus® Model CHA microscope. The hemacytometer had two chambers each with nine squares, 1-mm on a side.
- Cell counts were conducted at 24, 48, 72 and 96 hours for each concentration. Initial cell counts were performed only on control replicates.


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study
- Test concentrations: 0 .10, 1 .0, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: Algal cell counts for these concentrations were 97, 96, 78 and 2.5 %, respectively of the control population.

Reference substance (positive control):

not specified

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

4.5 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

5.5 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

8.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 7.3 - 10

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

11 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 9.5 - 12

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no

ANALYTICAL MONITORING

The five nominal concentrations of 6.5, 13, 25, 50 and 100 mg/L were selected from the results of a range-finding test. The measured concentrations at 0 hour were 5.9, 11, 22, 47 and 99 mg/L. Overall, the measured values represent 92 ± 5.1 % of the nominal concentrations. By 96 -hours, the measured concentrations had decreased such that no detectable quantities of Ethyl Acrylate were found in test levels one, two or three. Less than one percent of the nominal concentrations were detected in test levels four and five. It is believed that the decreased concentrations may be due to 1) volatility of the compound, 2) adsorption to the glass aquaria, and/or 3) adsorption to particulate, including algal cells, in the test solutions.

BIOLOGICAL RESULTS

The 24- and 48-hour EC50 values were estimated to be < 6.5 mg/L since a 50 % dose response was not exhibited in any of the treated test concentrations. All values obtained at 24 and 48 hours exhibited > 50 % inhibition even in the lowest concentration of 6.5 mg/L. However, based on cell counts, the 72 and 96 hour EC50 values were 8.9 and 11 mg/L, respectively. Growth was significantly inhibited at all concentrations from 24 through 96 hours. At termination, the cell counts for the 0, 6.5, 13, 25, 50, and 100 mg/L cultures were 141, 111, 68, 7.0, 1.3, and 0.67 E+4 cells/mL. All results were based on nominal test concentrations of ethyl acrylate since samples taken at 96 hours were below the detection limit of ethyl acrylate.

CONCLUSION

The 96-hour EC50 based on nominal concentrations was 11 mg/L. A recalculation using the arithmetic means for the exposure concentrations (2.9, 5.5, 11, 23, and 49 mg/L) provides a 96-hour EC50 of 5.5 mg/L. This value indicates the toxicity of ethyl acrylate to algae is similar to other aquatic species and the recalculated EC50 is considered appropriate for the assessment.

Validity criteria fulfilled:

not specified

Description of key information

Ethyl acrylate is acutely toxic to freshwater algae.
EC50 (72 h, cell number) = 4.5 mg/L (measured) (Selenastrum capricornutum, OECD TG 201)

 

As described in section 13.2 of IUCLID, testing information on acute toxicity to alga is consistent with six acrylic esters evaluated as a category. Testing information on chronic algal toxicity for 2-ethylhexyl acrylate is selected as a conservative approach (lowest NOEC). The NOEC for 2-EHA on growth rate is 0.45 mg/L.

 

NOEC (72 h, growth rate) = 0.45 mg/L (measured) (Selenastrum capricornutum, OECD TG 201)

 

 

Key value for chemical safety assessment

EC50 for freshwater algae:

4.5 mg/L

EC10 or NOEC for freshwater algae:

0.45 mg/L

Additional information

An acute toxicity study was conducted with Selenastrum capricornutum (BAMM, 1990) according to OECD Guideline 201 using a static design. Nominal exposure concentrations were 6.5, 13, 25, 50 and 100 mg/L. At time 0, the analyzed concentrations were 5.9, 11, 23, 47, and 99 mg/L. After 96 hours, analyses of the test media were all below the limit of detection. The loss of ethyl acrylate was considered to be related to volatility and/or adsorption to the vessels and the algae.

Growth inhibition of algae was observed at all concentrations from 24 through 96 hours. At termination, the cell counts for the 0, 6.5, 13, 25, 50 and 100 mg/L cultures were 141, 111, 68, 7.0, 1.3 and 0.67 cells/mL (x 10⁴), respectively. Based on cell counts, the 72 and 96 hour EC50 values were 8.9 and 11 mg/L, respectively. All results were based on nominal test concentrations of ethyl acrylate since samples taken at 96 hours were below the detection limit of ethyl acrylate.

A recalculation using the arithmetic means for the exposure concentrations (2.9, 5.5, 11, 23, and 49 mg/L) provides 72-hour and 96-hour EC50 values of 4.5 and 5.5 mg/L, respectively. This value indicates the toxicity of ethyl acrylate to algae is similar to other aquatic species and the recalculated EC50 is considered appropriate for the assessment.

No NOEC could be derived since significant growth inhibition was observed at all concentrations.

In addition, there is an older study with Scenedesmus subspicatus conducted according to DIN 38 412 L 9 without analytical monitoring (BASF AG, 1991). EC50 values after 72 hrs exposure were recalculated and determined to be 45.85 mg/L (biomass) and 73.64 mg/L (growth rate), respectively. This study which does not take the possible decrease in test concentration by volatilisation of the substance into consideration and is therefore not suitable for the assessment.

A robust data set of acute studies is available from the other members of the acrylic ester category (methyl, 2-ethylhexyl, n-butyl, isobutyl, and tert-butyl acrylate).  Testing information on 2-ethylhexyl, isobutyl, and tert-butyl acrylate on chronic algal toxicity are also available. Testing information for 2-ethylhexyl acrylate is selected as a conservative approach (lowest NOEC) to support the chronic algal endpoint. The NOEC for 2-EHA on growth rate is 0.45 mg/L.