Pyridoxine hydrochloride

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26-27 May 2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to OECD 209 (1984) and in compliance with GLP. The study report was very minimal and lacked detailed information. It was therefore considered reliable with restrictions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1984

Deviations:

yes

Remarks:

see below

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1986 (E) Method B

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Annex of EEC Directive 88/302/EEC (18 November 1987)

Deviations:

not specified

Principles of method if other than guideline:

The concentration of inoculum is somewhat lower than in the guideline (1.5 g/L). This is not causing and effect on the study as it is deemed worst-case.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Vehicle:

no

Details on test solutions:

No data. The stock solution was 2 g/L.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge from laboratory wastewater plant treating municipal sewage.
The inoculum was washed, brought to a concentration of 5 g/L dry substance and aerated during the night. 50 mL were added to a total volume of 250 mL to obtain a concentration of 1 g/L dry substance in the test.

Test type:

static

Water media type:

not specified

Limit test:

yes

Total exposure duration:

30 min

Post exposure observation period:

6 minutes

Hardness:

no data

Test temperature:

20 ± 2 ºC

pH:

The stock solution of the test substance was corrected from pH 3.5 to pH 7.5. The stock solution of the reference substance was corrected from pH 5.6 to pH 7.3 (no further details given).
At t=0, before adding the inoculum, pH of blanks were 6.8 before correction and 7.1 after correction (no further details were given on correction). The pH in the test substance solution was 7.0 before adding the inoculum and 7.3 at 30 minutes.

Dissolved oxygen:

Oxygen concentration during the 30 minutes aeration was > 2.5 mg/L
Oxygen concentration immediately before measurement was > 6.5 mg/L
See the attached table 1 of the oxygen concentrations during the 6 minutes measurement.

Salinity:

Not applicable

Nominal and measured concentrations:

Limit test of 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer
- Aeration: yes, but no further details
- blank control replicates: 3
- test substance replicates: 1
- reference substance replicates: 1
- Biomass loading rate: 1 g/L (50 mL inoculum/vessel)

TEST MEDIUM / WATER PARAMETERS
- 8 ml/vessel 100-fold concentrated OECD synthetic medium (corresponding to the OECD 209, 1984)

OTHER TEST CONDITIONS
- Adjustment of pH: Yes

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Oxygen concentration after 30 minutes incubation and 6 minutes later.

TEST CONCENTRATIONS
- Limit test of 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The test substance had no effect on the respiration rate of activated sludge as compared to the blank control.

Results with reference substance (positive control):

See the details in the attached table 3. The EC50 was 15 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the test, the test substance had no effect on the respiration rate of activated sludge as compared to the blank control. The EC50 was > 1000 mg/L. The NOEC was = 1000 mg/L

Executive summary:

An activated sludge respiration inhibition test was conducted with Vitamin B6 hydrochlorid according to OECD 209 (1984) and in compliance with GLP. After 30 minutes of exposure, the test substance did not cause effects on the respiration rate of activated sludge as compared to the blank control. The EC50 was > 1000 mg/L and the NOEC = 1000 mg/L. The validity criteria of the guideline were fulfilled. The study report was very minimal and lacked detailed information. The study was thus considered to be reliable with restrictions.

Description of key information

An activated sludge respiration inhibition test was conducted with Vitamin B6 hydrochlorid according to OECD 209 (1984) and in compliance with GLP. After 30 minutes of exposure, the test substance did not cause effects on the respiration rate of activated sludge as compared to the blank control. The EC50 was > 1000 mg/L and the NOEC = 1000 mg/L. The validity criteria of the guideline were fulfilled. The study report was very minimal and lacked detailed information. The study was thus considered to be reliable with restrictions.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L