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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 with acceptable restrictions
Remarks:
Study is considered to be reliable with the following restrictions: · study was not conducted under GLP · exposure concentrations were not analytical verified · age of neonates not documented · sublethal effects not documented · dissolved oxygen not documented
Principles of method if other than guideline:
USEPA. 1975. Methods for Acute Toxicity Tests with Fish, Macroinvertebrates, and Amphibians. Ecological Research Services, EPA-660/3-75-009. 61
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Neat test material added directly to exposure vessels
Test organisms (species):
other: Simocephalus vetulus
Details on test organisms:
TEST ORGANISM

- Source: Simocephalus vetulus neonates (age not documented) were obtained from laboratory cultures maintained under the same conditions used for testing.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
Hard water
Test temperature:
23±1ºC
pH:
7.4-7.7
Dissolved oxygen:
Not reported
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: 0, 100, 250, 300, 350, 400, 450, 500 mg/L
Details on test conditions:
TEST SYSTEM

- Test design:  static exposure, no solution renewal

- Dilution water:  reconstituted hard-water; glass-distilled water reconstituted with 192 mg/L NaHCO3, 120 mg/L CaSO4, 120 mg/L MgSO4, and 8 mg/L KCl (pH adjusted to 7.5 with NaOH).      

- Exposure vessel:  250-mL glass beakers containing 200 mL of dilution water; vessels aerated prior to but not after study initiation; vessels covered during exposure

- Replication:  duplicate controls and exposure concentrations, 10 organisms per exposure vessel; total of 160 organisms

- Observation periods:  0, 24, 48 h after study initiation

- Photo-period:  18-h light/6-h dark; 600 foot-candle
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
< 250 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
324 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 301-343
Details on results:
- Mortality of control: 0%
Reported statistics and error estimates:
LC50 values were determined by Probit analysis.

Table 1. Test results

 Nominal concentration (mg/L)  Percentage mortality after 24 hours  Percentage mortality after 48 hours
 0 (Control)  0  0
 250  5  20
 300  5  25
 350  20  45
 400  15  90
 450  15  95
 500  30  100
Validity criteria fulfilled:
yes
Conclusions:
A 48-hour LC50 value of 324 mg/L and NOEC of <250 mg/L have been determined for the effects of the test substance on mortality of Simocephalus vetulus (Family Daphnidae). It is likely that the test organisms were exposed primarily to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to invertebrates: 48 hour LC50 value of 324 mg/l (nominal) (OECD 202). The LC50 is equivalent to 266 mg/l when expressed in terms of [3-(2,3-epoxypropoxy)propyl]silanetriol.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
266 mg/L

Additional information

A 48 hour LC50 value of 324 mg/l (nominal concentration) has been determined for the effects of the test substance on mortality of Simocephalus vetulus (Family Daphnidae) (Dow Corning, 1978).

In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed primarily to the hydrolysis products of the substance. The results may be expressed in terms of concentration of the hydrolysis product, [3-(2,3-epoxypropoxy)propyl]silanetriol, by applying a molecular weight correction: (MW of silanol = 194.26 / MW of parent = 236.34) * 324 = 266 mg/l.

These values have been selected in preference to those from two equally reliable tests on the basis of being lower.

The other reliable studies report the following values:

A 48 hour EC50 value of 710 mg/l (nominal concentration) has been determined for the effects of the test substance on mobility of Daphnia magna (Springborn Smithers, 2002).

A 48 hour EC50 value of 473 mg/l (nominal concentration) has been determined for the effects of the test substance on mobility of Daphnia magna (Huls, 1993).