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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1997-06-18 to 1997-07-09
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Version / remarks:
Cited as OECD Guide-line 202, part 2 (Daphnia sp., Reproduction Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The analytical verification of the stock solution was carried out after 0, 2 and 5 days by measurement of dissolved organic carbon (DOC). The stock solutions were found to be stable.

The stability of exposure concentrations was determined by measuring DOC concentrations in fresh test media and in two and three day old media.

Test concentrations were measured in the fresh media at each renewal.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: For the preparation of a stock solution, 1 g/l of the test item was equilibrated in deionized water, stirred for about 18 hours, and filtered.  The resulting solution served as a stock solution for the preparation of the other treatments.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source: Laboratory stock culture

- Feeding during test

- Food type: Algae (Scenedesmus subspicatus)

- Amount: 0.5x10E7 cells/Daphnia until Day 6. 1.0x10E7 cells/Daphnia until end of test.

- Frequency: Daily


ACCLIMATION

- Acclimation conditions (same as test or not): Same as test

- Type and amount of food: Algae (Scenedesmus subspicatus)

- Feeding frequency: Daily in such an amount that it is all consumed each day.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Hardness:
Hard water
Test temperature:
20±1ºC
pH:
7.8-8.5
Dissolved oxygen:
83-107% ASV
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: 0 (Control), 2.5, 6.0, 16, 40 and 100 mg/L

The measured DOC concentrations in the test media were stable (within 20% of initial concentration) for periods of 3 and 5 days.

The measured DOC concentrations in the freshly prepared media were within ±20% of nominal for each medium renewal.

The results are reported and interpreted with reference to nominal concentrations.
Details on test conditions:
TEST SYSTEM

Test vessels: 100 ml glass beakers each containing 60 ml of test medium and 1 daphnid

Test design: Groups of 10 daphnia were individually exposed to each treatment.

Dilution water water: Synthetic fresh water, M4-medium as described by Elendt (1990)

Animal density: approximately 60 ml per individual

Frequency of test medium renewal: 3 times per week on Monday, Wednesday and Friday

Lighting: Light/dark: 16/8 hr, with a light ratio of approximately 600/100 lux. 58 W fluorescent lamps.
Reference substance (positive control):
no
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Details on results:
- Mortality of parent animals: 0% in control, 20% in highest treatment
Reported statistics and error estimates:
Significant differences between reproduction rates between treated and Control cultures were assessed by t-test. There were no significant differences.

Table 1. Summary of Results of Mortality and Reproduction Rate of
Daphnia Magna


Conc.      Control   2.5     6     16     40     100 
(mg/L)

Living MT  10        10      9      9     10      8

Inhibition MT
(%)        0         0       10    10     0      20

Living JT*
Parent:1  68         69      79    88     74     77
       2  75         52      -     89     60     38
       3  65         73      71     -     76     80
       4  54         81      76    82     51     74
       5  80         56      62    76     76     54
       6  63         73      66    80     71     45
       7  77         69      65    70     92     69
       8  65         68      67    67     78      -
       9  82         69      67    92     47      -
      10  85         95      92   102     73     85

Sum JT    714        705    645    746    698    522
Std Dev   9.9        12     9.4    11.1   13.5   17.4
Repro. Rate 71       71     72     83     70     65
Inhibition JT(%) -   0      -1     -17     1     8

Max Value  85        95     92     102     92    85
Min Value  54        52     62      67     47    38
Variat. Coeff.14     17     13      13     19    27   
t-Test     -         ns     >BI    >BI     ns    ns

where:
MT = mothers
JT = young
JT* = Living JT from the living mothers after 21 days
ns = not significant
>BI = reproduction rate > reproduction rate of the control,
no t-test performed


Table 2. pH and Oxygen Content (% Saturation) in the Test Solutions

Conc.  Day0   Day2   Day9   Day12    Day14    Day16
(mg/l) fresh 2-d old fresh  3-d old  fresh    2-d old
      pH  O2 pH  O2  pH  O2 pH  O2   pH  O2   pH  O2
contrl8.5 88 8.2 107 8.2 93 8.1 99   8.4 87   8.0 97
2.5   8.5 91 8.1 105 8.3 91 8.0 97   8.5 84   8.0 97
6.0   8.4 91 8.1 105 8.3 91 8.0 96   8.5 86   7.9 96
16    8.5 90 8.2 104 8.3 88 8.0 95   8.5 84   7.9 95
40    8.4 91 8.1 104 8.3 91 8.0 96   8.5 83   7.8 89
100   8.4 90 8.1 104 8.3 90 7.9 93   8.4 85   7.7 86

The pH of the freshly made up and 2-day and 3-day old
solutions of test item frequently deviated by more than 0.3
units. Since this did not affect the reproduction rate, this
pH change is not considered as reducing the quality of the
results.

Validity criteria fulfilled:
yes
Conclusions:
A 21-day NOEC of =100 mg/L has been determined for the effects of the test substance on reproduction of Daphnia magna. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

Long-term toxicity to invertebrates: 21day NOEC =100 mg/l (highest concentration tested) (OECD 211). The NOEC is equivalent to =82 mg/l expressed in terms of [3-(2,3-epoxypropoxy)propyl]silanetriol.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
82 mg/L

Additional information

A 21 day NOEC of =100 mg/l has been determined for the effects of 3-(2,3-epoxypropoxy)propyltrimethoxysilane on reproduction of Daphnia magna (Huls, 1993).It is likely that the test organisms were exposed 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) * =100 mg/l = =82 mg/l.