Hydrazine

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

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:

EU Method C.3 (Algal Inhibition test)

Deviations:

yes

Remarks:

the study data were analysed on a 48 h basis

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

concentrations were monitored at 0, 24 and 48 h

Vehicle:

no

Details on test solutions:

- A stock solution was prepared by weighing 4.1 mg of the test item into 2 litre of dilution water
- The pH was measured to be pH 8.2
- test item concentrations (nominal) of 0.063, 0.13, 0.25, 0.5 and 1.0 mg/L
- To produce the different test item concentrations appropriate amounts of the prepared stock solution were diluted with dilution water to a volume of 80 mL
- 10 mL of nutrient medium and 10 mL of algal inoculum with a cell density of 5000 cells/mL were added
- For each test item concentration and control 3 replicates were prepared

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Strain No. 86.81 SAG
obtained from 'The Collection of Algal Cultures' of the Institute of Plant Physiology at the University of Göttingen (Germany)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21 to 24 °C

pH:

at t0: 8.1 to 8.2
at t72 h: 8.0 to 8.3

Nominal and measured concentrations:

nominal concentrations: 0.063 mg/L, 0.13 mg/L, 0.25 mg/L, 0.5 mg/L and 1.0 mg/L
geometric mean measured concentrations: 0.009 mg/L, 0.018 mg/L, 0.039 mg/L, 0.062 mg/L and 0.134 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: Erlenmeyer flasks with cotton stoppers
- Initial cells density: 5000 cells per mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): none

GROWTH MEDIUM
- Standard medium used: according to Bringmann & Kühn (1977)

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: yes

OTHER TEST CONDITIONS
- Photoperiod: continuous uniform illumination
- Light intensity and quality: spectral range 400 to 700 nm, intensity 4000 to 8000 lx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: microcell counter

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Test item concentrations (nominal): 0.063 mg/L, 0.13 mg/L, 0.25 mg/L, 0.5 mg/L and 1.0 mg/L

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.017 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Remarks on result:

other: 95 % CL not determined

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.006 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Duration:

48 h

Dose descriptor:

EC10

Effect conc.:

0.008 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: 95 % CL not determined

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.01 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: 95 % CL not determined

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.006 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Details on results:

The results are expressed in terms of geometric mean measured concentrations. Effective concentrations ranged from 93.8% -99.2 % of nominal values at 0 hours, from 7.81 % - 12.5 % of nominal values at 24 hours and correspond to 3.13 % of nominal values at 48 hours, respectively.

The study was terminated after 48 h, because concentrations of the test item markedly decreased over time and thus the 48 h value reflects exposure better than the 72 h values. As cell numbers increased well above 16-fold over 48 h, and all other validity criteria are met, this is an option explicitly covered by OECD TG 201 (2006) and EU method C.3 (2009).

Validity criteria fulfilled:

yes

Executive summary:

The adverse effects hydrazine towards the growth of aquatic algae are characterized by an ErC50(48 h) of 0.017 mg/L as well as a NOEC of 0.006 mg/L referring to the reduction of the growth rate (Currenta, 2009). Effective concentrations are based on the geometric mean values of measured concentrations.

Description of key information

The adverse effects hydrazine towards the growth of aquatic algae are characterized by an ErC50(48 h) of 0.017 mg/L as well as a NOEC of 0.006 mg/L referring to the reduction of the growth rate (Currenta, 2009). Effective concentrations are based on the geometric mean values of measured concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.017 mg/L

EC10 or NOEC for freshwater algae:

0.006 mg/L

Additional information

The results are expressed in terms of geometric mean measured concentrations as effective concentrations ranged from 93.8 % -99.2 % of nominal values at 0 hours, from 7.81 % - 12.5 % of nominal values at 24 hours and correspond to 3.13 % of nominal values at 48 hours, respectively.

The study was terminated after 48 h, because concentrations of the test item markedly decreased over time and thus the 48 h value reflects exposure better than the 72 h values. As cell numbers increased well above 16-fold over 48 h, and all other validity criteria are met, this is an option explicitly covered by OECD TG 201 (2006) and EU method C.3 (2009).

There are several other studies reporting lower effective concentrations (Bringmann, Scherfig, Dixon) than observed in the selected key study. But:

- no information is given whether concentrations were determined analytically. As the test item concentration was shown to be not constant over time, measure concentrations would be quite crucial for the study evaluation.

- according to the Guidance document R.7b (ECHA, 2008), a test duration of 72 h is recommended to ensure exponential growth over the entire test duration. Reported test durations are well above 72 h and no information is given concerning the algal growth.

Concluding, due to these drawbacks, the studies cannot be used for the hazard assessment of hydrazine as it cannot be ensured that the toxicity of hydrazine towards aquatic algae is adequately described.