Calcium diformate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Only short abstract available; important information missing (e.g. source of activated sludge)

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

GLP compliance:

not specified

Analytical monitoring:

not specified

Test organisms (species):

activated sludge

Test type:

static

Water media type:

freshwater

Total exposure duration:

3 h

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

>= 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Reference 2

Endpoint:

toxicity to microorganisms, other

Remarks:

OECD 306 guideline

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD 306

Deviations:

no

Principles of method if other than guideline:

The toxicity of sodium formate to marine microorganisms was assessed as part of the toxicity control of an OECD 306 'Biodegradability in Seawater (Closed Bottle Test)' study.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

SAMPLING
- Sampling frequency: sampled on day 0, 5, 15, and 28
- oxygen measurements: day 0, 5, 15, and 28 with an oximeter

Vehicle:

no

Test organisms (species):

other: non-specific marine microbiota (present in collected seawater)

Test type:

static

Water media type:

saltwater

Total exposure duration:

28 d

Remarks on exposure duration:

The exposure duration was that of the biodegradation study.

Test temperature:

20°C ± 2.4°C

Nominal and measured concentrations:

22.1 mg/L

Details on test conditions:

TEST CONDITIONS
- Volume of test solution/treatment:
- Composition of medium: aged and decanted seawater, added mineral solutions according to guideline
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: 20°C±2.4°C
- pH adjusted: no
- Continuous darkness: yes
- Any indication of the test material adsorbing to the walls of the test apparatus: no

Reference substance (positive control):

yes

Remarks:

benzoic acid, sodium salt

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 22.1 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: biodegradation

Details on results:

Inhibitory effects of sodium formate to the marine microbiota present within the collected seawater that was used in the OECD 306 marine biodegradability study were not observed at the tested concentration 22.1 mg/L.

Results with reference substance (positive control):

The reference substance showed 82% biodegradation after 5 days.

This endpoint is sufficiently covered by the data on biodegradability (please see Section 5.2).

The results of the key study in Section 5.2 indicate that:

a) sodium formate is readily biodegradable,

b) disturbances in sewage treatment plants are not to be expected when sodium formate is released in appropriate amounts, and

c) inhibitory effects of sodium formate to sewage sludge bacteria were not observed at the tested concentration 22.1 mg/L.

Validity criteria fulfilled:

yes

Remarks:

The inoculum control was degraded by 82% within 5 days, therefore the inoculum activity was satisfactory. Moreover, oxygen depletion in the inoculum blank did not exceed 30% oxygen of the oxygen in the test bottle. The test is therefore considered valid.

Conclusions:

Sodium formate is readily biodegradable (86% degradation, based on ThOD, over 28 days) (KM Lab, 1998) and inhibitory effects of sodium formate to the marine microbiota present within the collected seawater were not observed at the tested concentration 22.1 mg/L, thus a NOEC of 22.1 mg/L is concluded.

Executive summary:

The biodegradability of sodium formate in seawater was investigated via a ‘Biodegradability in Seawater (closed bottle)’ study (OECD Guideline 306), which showed 86% degradation (ThOD) over 28 days (KM Lab, 1998). The study used a test concentration of 22.1 mg/L and included a toxicity control which investigated the inhibition of degradation activity of the marine microbiota present within the collected seawater used in the study. No inhibition of degradation activity was observed throughout the duration of the study, thus resulting in a 28 day (the duration of the biodegradation study) NOEC value of 22.1 mg/L. The inhibition of the degradation activity of activated sludge is therefore not anticipated when introduced in appropriately low concentrations.

Reference 3

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Peer-reviewed paper, but test methods and results poorly documented regarding inhibitory effects on bacterial growth

Test organisms (species):

other: other bacteria: sulfur-oxidizing and acidophilic iron-oxidizing strains of Thiobacillus

Details on test conditions:

Type: aquatic

It was found that the growth of Thiobacillus neapolitanus (ATCC  23638), T. thiooxidans (IFO 13724), and T. ferooxidans (JCM 7811) was  completely inhibited by 10 mmol/L (ca. 1.3 g/L) calcium formate (similar  results were obtained with sodium and ammonium formate)

Description of key information

NOEC = 22.1 mg/L (KM Lab, 1998). The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriately low concentrations.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

22.1 mg/L

Additional information

No reliable data exist regarding the toxicity of calcium diformate to microorganisms. Therefore a read across is performed to sodium formate.

This endpoint is sufficiently covered by the data on biodegradability (please see Section 5.2).

The results of the key study in Section 5.2 indicate that

a) sodium formate is readily biodegradable,

b) disturbances in sewage treatment plants are not to be expected when sodium formate is released in appropriate amounts, and

c) inhibitory effects of sodium formate to sewage sludge bacteria were not observed at the tested concentration 22.1 mg/L.

It can be concluded that the inhibition of the degradation activity of activated sludge is not anticipated when sodium formate and hence calcium formate is introduced in appropriately low concentrations.