2-ethylbutyric acid

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes

Test organisms (species):

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

Total exposure duration:

72 h

Nominal and measured concentrations:

0, 15.3, 24.4, 39.1, 62.5, and 100 mg/l

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 63 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

39 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

63 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

At 62.5 and 100 mg/l, a significant reduction in pH occurred. A precise value for EC50 could not be obtained because the biomass of Pseudokirchneriella subcapitata was determined by cell count, however, at higher concentrations cell size was altered. Growth rate and cell density were reduced at higher concentrations, while percentage (%) inhibition comparatively increased.

Validity criteria fulfilled:

not specified

Conclusions:

Following the 72-hour exposure of green alga Pseudokirchneriella subcapitata with 2-ethylbutyric acid (0 - 100 mg/l), an EC50, NOEC, and LOEC of >63, 39, and 63 mg/l was reported. As the EC50 value is above the 1 mg/l threshold specified in the CLP Regulation (EC) No 1272/2008, this result is suggestive of 2-ethylbutyric acid being non-toxic to algae and other aquatic plants under the conditions of this experiment.

Executive summary:

An experiment was undertaken to establish the aquatic toxic potential of 2-ethylbutyric acid to green alga Pseudokirchneriella subcapitata. Which is considered to be representative species for aquatic algae and cyanobacteria. The experiment was performed according to Good Laboratory Practise (GLP) and OECD Guideline 201 (Alga, Growth Inhibition Test) (rate method) at 0, 15.3, 24.4, 39.1, 62.5, and 100 mg/l. The pH was not adjusted despite 2-ethylbutyric acid being acidic and, therefore, any true toxic effects would not be distinguishable from low pH effects of the substance, if present. Algal biomass was measured by cell count and so the precise EC50 could not be established. Growth rate was used as a basis for the measurement of aquatic toxicity, with resulting values at 72-hours of EC50 = >63 mg/l, NOEC = 39 mg/l, and LOEC = 63 mg/l. At higher concentrations, cell size was altered, growth rate and cell density declined, and inhibition increased. Given that the 72-hour EC50 was >1 mg/l (>63 mg/l), this result is suggestive of 2-ethylbutyric acid being non-toxic to aquatic algae and cyanobacteria, such as Pseudokirchneriella subcapitata, under the conditions of this experiment (CLP Regulation (EC) No 1272/2008).  

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2000

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Insufficient information for an assessment of reliability.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

not specified

Test organisms (species):

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

Total exposure duration:

72 h

Test temperature:

23 ± 2 °C

Nominal and measured concentrations:

15.3, 24.4, 39.1, 62.5, and 100 mg/l

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

39.1 mg/L

Conc. based on:

test mat.

Basis for effect:

not specified

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 60.8 - <= 77.5 mg/L

Conc. based on:

test mat.

Basis for effect:

not specified

Validity criteria fulfilled:

not specified

Conclusions:

A 72-hour NOEC of 39.1 mg/l and EC50 of ≥60.8 - ≤77.5 mg/l was calculated following exposure of Pseudokirchneriella subcapitata (previous name: Selenastrum capricornutum) to 2-ethylbutyric acid.

Description of key information

The 72-hour exposure of green alga Pseudokirchneriella subcapitata to 2-ethylbutyric acid at six concentrations between 0 - 100 mg/l resulted in an EC50, NOEC, and LOEC of >63, 39, and 63 mg/l. Under the conditions of the experiment, the registered substance can be regarded as non-toxic to aquatic algae and cyanobacteria given an EC50 value >1 mg/l (CLP Regulation (EC) No 1272/2008). A 72-hour NOEC of 39.1 mg/l and EC50 of ≥60.8 - ≤77.5 mg/l was similarly calculated following exposure of Pseudokirchneriella subcapitata (previous name: Selenastrum capricornutum) to 2-ethylbutyric acid in a supporting study.

Key value for chemical safety assessment

EC50 for freshwater algae:

63 mg/L

EC10 or NOEC for freshwater algae:

39 mg/L