Carboxylic acids, C5-9

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles Data from ciliate growth inhibition tests, preferably with the species Tetrahymena are also relevant for the risk assessment for STPs.

Qualifier:

no guideline followed

Principles of method if other than guideline:

TETRATOX assay: Tetrahymena pyriformis population growth impairment

GLP compliance:

not specified

Specific details on test material used for the study:

Nonanoic acid is one of the main constituents of the target UVCB substance

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Tetrahymena pyriformis

Details on inoculum:

- Test organism: Tetrahymena pyriformis (strain GL-C)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

40 h

Test temperature:

27 ± 1 °C

Nominal and measured concentrations:

five concentration levels

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 250 mL Erlenmeyer flasks, 50 mL semi-defined medium
- No. of organisms per vessel: ca. 2,500 cells/mL in log-growth phase
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2 + 1 blank
- No. of tests per substance: 3

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- growth impairment: population density is measured spectrophotometrically

TEST CONCENTRATIONS
- Range finding study performed

STATISTICAL EVALUATION
- 50 % inhibitory growth concentration in mg/L (IGC50)
- IGC50: Probit analysis using the percent control-normalized absorbance as the dependent variable and the toxicant concentration in mg/L as the independent variable

Duration:

40 h

Dose descriptor:

IC50

Effect conc.:

71 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth inhibition

Remarks on result:

other: original value reported: -log (IGC50) = 0.3509

Validity criteria fulfilled:

not applicable

Conclusions:

Growth inhibition of Tetrahymena pyriformis: IGC50 (40 h): 71 mg/L
Nonanoic acid is one of the main constituents of the target UVCB substance.

Executive summary:

The growth inhibiting effect of nonanoic acid on the ciliate Tetrahymena pyriformis was determined using the TETRATOX assay. The resulting IGC50 (40 h) of 71 mg/L indicates a low toxicity of nonanoic acid to microorganisms (ciliates).

Reference 2

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1979

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

abstract

Qualifier:

no guideline followed

Principles of method if other than guideline:

Bacillus subtilis was tested with different substances and the optical densitiy measured after 1 h to calculate the inhibition.

GLP compliance:

no

Analytical monitoring:

not specified

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Inoculum was placed into plastic tubes or Erlenmeyer flasks which already contained the test substance
- Controls: 2 with solvent, 2 with distilled water
- Chemical name of vehicle: Ethanol, dimethylsulfoxide, sodium hydroxide or distilled water
Test organisms

Test organisms (species):

Bacillus subtilis

Details on inoculum:

- Pretreatment: Plated with tryptose blood agar base (33 g/L) were inoculated from single colonies of Bacillus subtilis and incubated for 7 h. Afterwards the cells were supended and diluted at different low titers into three flasks containing the MCV medium and shaken at room temperature overnight. If the cultures had not grown overnight beyond an optical density at 600 nm (OD600) of 1.0 it was not used. The cultures reaching 1.0 were utilised for the test.

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

60 h

Hardness:

Not specified

Test temperature:

Not specified

pH:

7.2, adjusted with KOH

Dissolved oxygen:

Not specified

Salinity:

Not added

Conductivity:

Not specified

Nominal and measured concentrations:

Not specified

Details on test conditions:

TEST SYSTEM
- Test vessel: Plastic tubes or Erlenmeyer flasks
- Aeration: Tubes were aerated.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: MCV medium contains 1.4% K2HPO4 , 0.6% KH2PO4, 0.2% MgSO4 * 7 H2O, 0.1% sodium citrate, 25 µg/mL L-tryptophan, 10 µg/mL L-methionine and 1 % vitamin-free casein hydrolysate

OTHER TEST CONDITIONS
- Adjustment of pH: with KOH to 7.2

EFFECT PARAMETERS MEASURED: optical density at 600 nm after 60 min in the plastic tubes and after 15 or 20 min in the Erlenmeyer flasks

Reference substance (positive control):

no

Duration:

60 min

Dose descriptor:

EC50

Effect conc.:

1.88 mmol/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Validity criteria fulfilled:

not specified

Conclusions:

Growth inhibition of Bacillus subtilis: EC50 (60 h): 1.88 mmol/l
Octanoic acid is one of the main constituents of the target UVCB substance.

Executive summary:

The growth inhibiting effect of octanoic acid on Bacillus Subtilis was determined. The resulting EC50 (60 h) of 1.88 mmol/L indicates a low toxicity of octanoic acid to microorganisms

Reference 3

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not specified

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

abstract

Qualifier:

no guideline followed

Principles of method if other than guideline:

Six different bacteria were anaerobically incubated and the turbitidy measured to determine inhibition on growth.

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test solution was prepared by dissolving measured quantities of the test substance in absolute ethanol. First a 250 mM stock solution was prepared and then further diluted with ethanol to 200, 175, 150, 125, 100, 75, 50, 25, 10, 5 and 2.5 mM.
- Controls: Since the test compund produces culture turbidity, a dilution series with medium and test compound without inoculum were prepared.

Test organisms (species):

other: Bifidobacterium bifidum type a, Bifidobacterium bifidum type b, Bifidobacterium infantis sp infantis type a, Bifidobacterium infantis sp infantis type b, Escherichia coli, Salmonella typhimurium

Details on inoculum:

- Preparation of inoculum for exposure: The PYG medium was dispensed into a 500 mL screw-capped bottle and sterilised at 121 °C for 15 min. While cooling, 3.0 mL were delivered into metal capped culture tubes which were inoculated with 0.03 mL of the substance stock solutions (2.5 - 20 mM). The culture tubes were placed in an anaerobic cabinet and maintained at 37°C over night. Oxygen free gas (20% nitrogen in hydrogen) was supplied.
Study design

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

29 h

Hardness:

Not specified

Test temperature:

37 °C

pH:

4.5 - 6.6, the pH was measured in the highest and lowest substance concentrations.

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

Not specified

Nominal and measured concentrations:

Nominal: 200, 175, 150, 125, 100, 75, 50, 25, 10, 5 and 2.5 mM

Details on test conditions:

TEST SYSTEM
- Test vessel: culture tubes
- No. of vessels per control (replicates): one series (2.5 - 200 mM test substance) with test substance without inoculum to determine turbidity

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The PYG media (Petone-yeast extract glucose) with 1% glucose, was prepared and dispersed anaerobically and sterilised. Anaerobic culture counts were performed on PYG-agar roll tubes.

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED: turbidity after 29 h

Reference substance (positive control):

no

Duration:

29 h

Dose descriptor:

EC50

Effect conc.:

80 other: nmol

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Remarks on result:

other:

Remarks:

B. Bifidum type a

Duration:

29 h

Dose descriptor:

EC50

Effect conc.:

15 other: nmol

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Remarks on result:

other:

Remarks:

B. Infantis sp. Infantis type a

Duration:

29 h

Dose descriptor:

EC50

Effect conc.:

2.5 other: nmol

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Remarks on result:

other:

Remarks:

B. Infantis sp. Infantis type b

Duration:

29 h

Dose descriptor:

EC50

Effect conc.:

0 other: nmol

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other:

Remarks:

S. typhimurium

Details on results:

No 50 % inhibition on bacterial growth was achieved on E. coli and B. bifidum type b.

Validity criteria fulfilled:

not specified

Conclusions:

No 50 % inhibition on bacterial growth was achieved on E. coli and B. bifidum type b.

Reference 4

Endpoint:

activated sludge respiration inhibition testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is found to be readily biodegradable and the applied test concentrations are in the range of concentrations that can be expected in the influent of a sewage treatment plant

Justification for type of information:

In consideration of the results obtained from the study according to OECD 301B (substance ready biodegradable) no toxicity is expected on aquatic microorganisms at the expected concentration

Description of key information

Disturbances in sewage treatment plants are not to be expected when the target UVCB substance is released in appropriate amounts. The substance is readily biodegradable.

Also the available data on the substance main constituents are in agreement with this conclusion.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

32 mg/L

Additional information

The results of the OECD 301B study (Tosin, 2018) indicate that

a) Carboxylic acid, C5-9 is readily biodegradable,

b) disturbances in sewage treatment plants are not to be expected when Carboxylic acid, C5-9 is released in appropriate amounts, and

c) inhibitory effects of Carboxylic acid, C5-9 to sewage sludge bacteria was not observed at a concentration of 32 mg/L of Carboxylic Acids, C5 -9

In addition, the growth inhibiting effect of nonanoic acid on the ciliate Tetrahymena pyriformis was determined: IGC50 (40 h) = 71 mg/L (Schultz, 2006).

Supportive information is withdrawn from short abstracts of two publications. In the first study (Freese, 1979) conducted with Bacillus subtilis, a EC50 of 0.25 mmol/L was obtained after 60 min. In the second study (Powell and May, 1981) with six different bacterial strains incubated anaerobically, different sensitivity of the various organisms to decanoic acid were observed. However, due to limited documentation and consequently limited information, these two literature studies were rated as not assignable.