Formaldehyde

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms, other

Remarks:

respiration inhibition test with single species

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

exposure time not documented

Principles of method if other than guideline:

Respiration Inhibition Test, modified

Test organisms (species):

Pseudomonas putida

Dose descriptor:

NOEC

Effect conc.:

30 mg/L

Executive summary:

The single species Pseudomonas putida was exposed to the test item in a modified respiratory inhibition test. The NOEC was determined to be 30 mg/L.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study is not performed according to international or national accepted guideline and only few data are presented in the study. The methanol content of the test substance is not given. However, these deficiencies do not invalidate the study because it appears to be conducted according to general scientific standards.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Test was performed according to Offhaus K (1973) Münchner Beitr Abwasser Fisch Flussbiol 24, 169

GLP compliance:

no

Specific details on test material used for the study:

- Name of test material (as cited in study report): Formaldehyde
- Analytical purity: No data
- Composition of test material, percentage of components: No data
- Lot/batch No.: No data

Analytical monitoring:

no

Details on sampling:

Not applicable

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: No data, however formaldehyde is not volatile from water at the concentration range tested

Test organisms (species):

other: Mixed bacterial culture

Details on inoculum:

- Source: Settled municipal wastewater
- Sampling site: No data
- Laboratory culture: No
- Method of cultivation: Method according to Offhaus K (1973) Münchner Beitr Abwasser Fisch Flussbiol 24, 169
- Preparation of inoculum for exposure: No data
- Pretreatment: No data
- Initial biomass concentration: No data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

120 h

Post exposure observation period:

None

Hardness:

No data

Test temperature:

20 ± 1 °C

pH:

8.4

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Not applicable

Details on test conditions:

TEST SYSTEM
- Culturing apparatus: Sapromat (type B12, Voith, Heidenheim, Germany) and Baromat (WTW, BSB-Messgerät, model 1200, Weilheim, Germany)
- Type: closed. However, test substance is not volatile from water at the concentration range tested
- Aeration: No data
- No. of vessels per concentration (replicates): No data
- Controls: No data
- Biomass loading rate: No data

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: No data

EFFECT PARAMETERS MEASURED: Respiration inhibition, oxygen consumption rate associated with peptone degradation. No data about sampling regime.

TEST CONCENTRATIONS: Not reported

Reference substance (positive control):

no

Duration:

120 h

Dose descriptor:

EC10

Effect conc.:

14.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

34.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

120 h

Dose descriptor:

other: EC90

Effect conc.:

78.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

No data

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Calculation of ECx values using linear regression analysis

Validity criteria fulfilled:

not applicable

Conclusions:

Formaldehyde is harmful towards bacteria.

Executive summary:

Formaldehyde was found to be harmful to the mixed bacterial inoculum, because it inhibited oxygen consumption associated with peptone degradation.

The methanol content of the test substance is not given. However, due to the fact that the concentrations at which methanol shows effects to aquatic organisms are several orders of magnitude lower than those expected for formaldehyde, these do not affect the results of the study.

Reference 3

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Study data are not reported in full detail (e.g., initial concentration, etc.); methanol content of the test substance is not given. However, this does not affect the overall validity of the results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

(as adopted 1981)

Deviations:

yes

Remarks:

Synthetic sewage used for activated sludge incubation was slightly different from the OECD guideline 209 instructions (K2HPO4 concentration was increased to 28 g/L).

Principles of method if other than guideline:

Not applicable

GLP compliance:

no

Specific details on test material used for the study:

- Name of test material (as cited in study report): Formaldehyde
- Analytical purity: Reagent grade
- Composition of test material, percentage of components: No data
- Lot/batch No.: No data

Analytical monitoring:

no

Details on sampling:

Not applicable

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: No data
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Not applicable

Test organisms (species):

activated sludge

Details on inoculum:

- Source: Local municipal wastewater treatment plant, sampling 1 day before test performance
- Sampling site: No data
- Laboratory culture: No
- Method of cultivation: 9 L laboratory scale, semicontinuous sludge cylinder, supplemented daily with 50 mL synthetic sewage stock solution
- Preparation of inoculum for exposure: Solids were allowed to settle, waste liquor was discarded and solids were washed three times with deionisized water
- Pretreatment: No
- Initial biomass concentration: 4000 ± 400 mg suspended solids/L (dry weight)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

None

Hardness:

No data

Test temperature:

21 °C

pH:

7.5 ± 0.5 at start of the test
7.4 – 8.0 at the end of the test

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Actual concentrations of test substance were not determined

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: open, however test substance is not volatile at the concentrations applied in the test
- Material, size, headspace, fill volume: 1L bottles
- Aeration: Pasteur pipette aeration device, 0.5 –1.0 L/min
- No. of vessels per concentration (replicates): No data.Two untreated controls at the beginning and the end of the tests, 3 different reference substance concentrations were run in parallel
- No. of vessels per control (replicates): 2, controls were run for each test at the beginning and the end of the test
- Biomass loading rate: 1600 mg suspended solids/L (dry weight)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Synthetic sewage stock solution: 16.0 g/L Bacto-Peptone, 11.0 g/L Bacto-Beef extract; 3.0 g/L urea, 28.0 g/L K2HPO4, 0.2 g/L MgSO4 ··7H2O, 0.4 g/L CaCl2 · 2H2O, 0.7 g/L NaCl, pH 7.0

EFFECT PARAMETERS MEASURED: In a standard BOD dilution bottle oxygen consumption was determined over a 5 minute period after 3 hours, using an Orion model 97-08 polarographic oxygen electrode and Orion model 701 Ionanalyzer.

TEST CONCENTRATIONS: No data

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (99%)

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

19 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: (Graphic Analysis)

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

19.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: (Moving Average Analysis by Thompson)

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

20.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: (Probit Analysis), 95% confidence interval 16.1 – 25.8 mg/L

Details on results:

No data

Results with reference substance (positive control):

3h EC50 = 12.2 ± 2.0 mg/L (n = 24, variance: 18%, Moving Average Analysis)

Reported statistics and error estimates:

Respiration rate (mg O2 / L / minute) was determined graphically from the slope between approx. 6.0 and 2.0 mg O2/L of the recorded graph.
Three alternative methods for data analysis were applied: inhibition data were analysed graphically by log-linear interpolation from concentration-response values, Thompsons method of moving averages or probit analysis

The study authors found probit analysis to be superior to the other two methods with respect to curve fitting and confidence intervals.

Validity criteria fulfilled:

not specified

Remarks:

No data if the two control respiration rates are within 15 per cent of each other. The EC 50 (3 hours) of 3,5-dichlorophenol is in the accepted range 5 to 30 mg/l.

Conclusions:

Formaldehyde was found to be harmful towards activated sludge inoculum.

Executive summary:

The analysis by probit is preferred.

The test is considered as valid as the validity criteria given in OECD 209 (as adopted 1981) were met: a) the difference of the duplicate controls was within a range of 15%; b) the sensitivity of the activated sludge towards the reference substance was within the accepted range (EC₅₀ between 5 and 30 mg/L).

The methanol content of the test substance is not given. However, due to the fact that the concentrations at which methanol shows effects to aquatic organisms are several orders of magnitude lower than those expected for formaldehyde, these do not affect the results of the study.

Description of key information

Depending on local conditions and existing concentrations, disturbances in the biodegradation process of activated sludge are possible

Key value for chemical safety assessment

EC50 for microorganisms:

19 mg/L

EC10 or NOEC for microorganisms:

14.7 mg/L

Additional information

In an activated sludge respiration inhibition test according to OECD 209 an EC50 of 19 mg/L was determined after 3h (Klecka et al., 1985). These findings are supported by another experimental study with mixed microorganism cultures from municipal wastewater (Tisler et al., 1997), no official guideline was followed. Nevertheless, the study is well documented and follows generally acceptable scientific principles. The inhibition of total respiration was measured and an EC50 of 34.1 mg/L after 120 h was determined. The EC10 (120 h) was 14.7 mg/L. These results are within the same range as in the guideline study (Klecka et al., 1985).

In addition, the NOEC in a single species test with Pseudomonas putida was determined in a modified respiratory inhibition test (Gericke, 1990). The NOEC was 30 mg/L. No exposure time is given but the result is similar to the previous mentioned results, so this value can be seen as plausible and supports the previous results.

In conclusion, based on the available experimental values the test item is harmful to microorganism and disturbance of degradation processes of activated sludge  in sewage treatment plants is possible.