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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Principles of method if other than guideline:
EPA 600/3-75-009, US Environ Prot Agency, Corvallis, Oregon, 61 pp
GLP compliance:
not specified
Analytical monitoring:
yes
Details on test solutions:
- stock solutions were prepared in soft reconstituted water
- reconstituted water was prepared by adding the following quantitees of salts to 1 L of deionized water: 48 mg NaHCO3, 30 mg MgSO4, 30 mg CaSO4, 2 mg KCl
Test organisms (species):
Daphnia pulex
Test type:
semi-static
Water media type:
freshwater
Total exposure duration:
48 h
Hardness:
around 35 mg/L as CaCO3
Test temperature:
20 °C
pH:
7.1 - 7.2
Dissolved oxygen:
8.2 mg/L
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
0.19 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: immobilization
Remarks on result:
other: 0.16 - 0.23 mg/L (95 % CL)
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
0.16 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: immobilization
Remarks on result:
other: 0.13 - 0.19 mg/L (95 % CL)
Details on results:
Analytic Monitoring:
Exposure Tank Hydrazine Concentratin mg/l
Test 1 Test 2
0 <0.002 +/- 0.000 <0.002 +/- 0.000
1 0.04 +/- 0.006 0.03 +/- 0.007
2 0.08 +/- 0.008 0.06 +/- 0.002
3 0.16 +/- 0.006 0.13 +/- 0.006
4 0.31 +/- 0.024 0.26 +/- 0.010
5 0.66 +/- 0.030 0.53
6 1.26 +/- 0.060 1.07
7 2.75 +/- 0.144 2.17 +/- 0.119
8 5.36 +/- 0.245 4.35

Summarizing these results, the hydrazine loss was minor during the daphnid static exposures. Mean hydrazine loss was 2.7 % for the 24 h-periode preceding and following renewal. Thus, the hydrazine concentration did not fall below 80 % of nominal concentrations justifying the use of nominal concentrations.
EC50 related to hydrazine
Since there is no significant difference between the two 48 h values (Velte, 1984), a mean EC50(48 h) can be calculated. 
EC50(48 h)= 0.175 mg/L
Conclusions:
Hydrazine has to be scored as very toxic towards aquatic life.
Executive summary:

For hydrazine an EC50(48 h) of 0.175 mg/L was observed with respect to the immobilization of daphnids (Velte, 1984).

Description of key information

For hydrazine an EC50(48 h) of 0.175 mg/L (mean value of two separate tests) was observed with respect to the immobilization of daphnids (Velte, 1984), whereas exposure concentrations were proved by analytical measurements. 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.175 mg/L

Additional information

Since there is no significant differnce between the two obtained 48 h values, a mean EC50(48 h) of 0.175 mg/L was used for the further assessment. Tests were conduced as a static renewal test, whereas initial hydrazine exposure concentrations were measured at 0 and 24 h, and the renewal concentrations were measure at 24 and 48 h by the means of a colorimetric method. The hydrazine loss was minor during the daphnid static exposures. Mean hydrazine loss was 2.7 % for the 24 h-period preceding and following renewal. Thus, the hydrazine concentration did not fall below 80 % of nominal concentrations justifying the use of nominal concentrations.

The study performance is comparable to current guidelines but having one minor drawback concerning the study documentation. No information is presented with respect to the mortality in control samples as an indication of stress or illness independent of the presence of the test item. Nevertheless, the results were used for the hazard assessment as the obtained results would rather overestimate the toxicity of the test item in the case that other factors contributed to the observed effects (stress, illness). Consequently, results would be more protective with respect to aquatic hazard assessment.