Hydrazine

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Direct weighings were prepared to give the different test item concentrations. The test item was added into Erlenmeyer flasks (incubation vessels) to about 130 mL deionised water

Test organisms (species):

activated sludge of a predominantly domestic sewage

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 +/- 2 °C

pH:

7.6 to 7.9

Nominal and measured concentrations:

range-finding test: 10, 100, 1000 mg/L (nominal)
main-test: 5.6, 10, 18, 32, 56 mg/L (nominal)

Details on test conditions:

EXPERIMENTAL PROCEDURE

- 250 mL of sludge with test item (or control or reference compound) was incubated for 3 h in 300 mL closed Erlenmeyer flasks (with air inlet and outlet) and aerated through a glass tube at 50-100 L/h with clean oil-free air.
- the content of the Erlenmeyer flasks was completely transferred to 250 mL BOD bottles and O2-content was measured with an O2-meter (redox electrode) with writer.
- Two controls without test item were included in the test design, one at the start and the other at the end of the test series.
- reference compound: 3,5-Dichlorophenol
- physico-chemical oxygen consumption control: to differentiate between physico-chemical oxygen consumption and biological oxygen consumption (respiration), at least the maximum concentration of the test item was tested without activated sludge.
- The respiration rate for each concentration was determined graphically from the linear part of the curve of O2-content versus time. The inhibitory effect of the test item at a particular concentration is expressed as a percentage of the mean of the respiration rates of two controls. An EC50 value was calculated from the respiration rates at different test item concentrations.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

8.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: referring to hydrazine hydrate (containing 64 % hydrazine); 95 % CI: .7 to 11.4 mg/L

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

5.5 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: referring to 100 % hydrazine

Validity criteria fulfilled:

yes

Remarks:

All validity criteria of the test method were met: - respiratory rates of the 2 controls differ less than 15 % from each other - the EC50 of the reference compound 3,5-Dichlorophenol is in the range 5 – 30 mg/L

Executive summary:

The toxicity of hydrazine towards microorganisms is characterized by an EC50(3 h) of 5.5 mg/L (nominal) testing the respiration rate of activated sludge (Currenta, 2010c).

Description of key information

The toxicity of hydrazine towards microorganisms is characterized by an EC50(3 h) of 5.5 mg/L (nominal) testing the respiration rate of activated sludge (Currenta, 2010c). 

Key value for chemical safety assessment

EC50 for microorganisms:

5.5 mg/L

Additional information

According to the Guidance document R.7b (ECHA, 2008), preference is given to tests with a mixed inoculum that assess the functioning of the entire microbial community in a sewage treatment plant, rather than tests based on single species or even microbial sub-systems. Respirometry is generally considered as an approach that will integrate the functioning of all organisms in an STP. Concluding, Currenta (2010c) was chosen to represent the toxicity of the test item towards microorganisms and thus the functioning of the sewage treatment plant, as all reported supporting studies performed by Bringmann et al. used single species as test organisms. These species represent only a minor part of microorganisms present in sewage treatment systems and should only be used for the risk assessment in the absence of other reliable data.