Isobutyric acid

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: German industrial standard test guideline DIN 38412, part 9

Principles of method if other than guideline:

Method used is comparable to OECD TG 201 (Freshwater Algae and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: SAG 86.81

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

20 °C

Nominal and measured concentrations:

Nominal concentrations (mg/l): control, 3.9, 7.8125, 15.625, 31.25, 62.5, 125, 250, 500 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer vessels
- Material, size, headspace, fill volume: glass, 10 ml fill volume
- Initial cells density: 10 000 cells/ml

GROWTH MEDIUM
- Standard medium used: OECD medium

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: fluorimeter
- Observation intervals: 0, 24, 48 and 72 h

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

29.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

45.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

76.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

30.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: fluorescence

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

44.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: fluorescence

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

75.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: fluorescence

Details on results:

- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: at low test substance concentrations

Measured algal cell density (fluorescence) after 0 h, 24 h, 48 h and 72 h (relative units, mean of 4 replicates)

 

Nominal Concentrations [mg/L]	Time
	0 h	24 h	48 h	72 h
0 (controls)	106.7 ± 3.58	227.7 ± 15.79	892.2 ± 114.9	2327.6 ± 196.37
3.9	105.6 ± 3.5	277.4 ± 11.68	1037.5 ± 42.94	2653.7 ± 166.35
7.8	108.3 ± 3.22	269.7 ± 4.8	1000.2 ± 20.09	2448.5 ± 58.61
15.6	108.5 ± 4.02	266.7 ± 23.39	993.1 ± 126.35	2398.1 ± 305.27
31.25	103.3 ± 6.01	263.3 ± 25.68	860.9 ± 89.82	1823.6 ± 253.33
62.5	96.8 ± 3.29	181.9 ± 6.27	238.2 ± 34.85	290.7 ± 86.91
125	83.4 ± 1.86	56.6 ± 1.77	44.1 ± 1.46	33.1 ± 3.53
250	77.1 ± 2.75	55.6 ± 0.62	34.6 ± 1.73	12.9 ± 0.94
500	70.7 ± 2.6	44.1 ±0.93	9.7 ± 0.97	6.1 ± 2.37

 

Validity criteria fulfilled:

yes

Executive summary:

In a 72-h acute toxicity study similar to OECD TG 201, cultures of Scenedesmus subspicatus (new name Desmodesmus subspicatus), strain SAG 86.81, were exposed to isobutyric acid at nominal concentrations of 0 (controls), 3.9, 7.8, 15.6, 31.25, 62.5, 125, 250, and 500 mg/L under static conditions. Cell density was recorded at 0, 24, 48 and 72h by fluorescence measurement.

The 72 -h EC10 was determined to be 29.4 mg/L (BASF AG, 1990)

The 72-h EC50 was determined to be 44.7 mg/L (BASF AG, 1990).

 

This toxicity study is acceptable and adequate to satisfy the information requirements for the toxicity to aquatic algae.

Description of key information

In a valid growth inhibition test with green algae similar to OECD TG 201, the EC50 of isobutyric acid was determined to be 45.1 mg/L (BASF AG, 1990)

Key value for chemical safety assessment

EC50 for freshwater algae:

45.1 mg/L

EC10 or NOEC for freshwater algae:

29.4 mg/L

Additional information

The toxicity of isobutyric acid to aquatic algae was investigated in two studies. One study is only reported in a Handbook, thus reliability of the data cannot be assessed (Verschueren, 1983). The second study (BASF AG, 1990) was performed according to a German test guideline (DIN 38412 part 9) which is comparable to OECD TG 201. Reliability is 2.

 

BASF 1990

 

In a 72-h acute toxicity study similar to OECD TG 201, cultures of Scenedesmus subspicatus (new name Desmodesmus subspicatus), strain SAG 86.81, were exposed to isobutyric acid at nominal concentrations of 0 (controls), 3.9, 7.8, 15.6, 31.25, 62.5, 125, 250, and 500 mg/L under static conditions. Cell density was recorded at 0, 24, 48 and 72h by fluorescence measurement.

 

The 72-h EC50 was determined to be 45.1 mg/L (BASF AG, 1990).