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Toxicity to soil macroorganisms except arthropods

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Endpoint:
toxicity to soil macroorganisms except arthropods: short-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
See attached document in section 13 "Assessment report" for justification and rationale of the analogy approach.
Original letters from the French Competent Authorities requiring the read across to be done with cerium and iron oxide isostearate are attached below.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
14 d
Dose descriptor:
LC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
14 d
Dose descriptor:
LC0
Effect conc.:
>= 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
14 d
Dose descriptor:
LC100
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth
Remarks:
body weight
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth
Remarks:
body weight
Conclusions:
Iron oxide isostearate is to be considered as Cerium and iron oxide isostearate as to be non-toxic to the earthworm Eisenia foetida up to and including the highest nominal concentration of 1000 mg/kg dry soil in the 14-day test.
Executive summary:

The source and target substances present similar characterization (nanoparticles of very similar parameters) and similar physico-chemical and ecotoxicological properties (high melting point, low vapour pressure, very low water solubility, no expected bioaccumulation potential when considering cerium and iron elements and isostearate parts, no acute toxicity to daphnids up to and including the saturation concentration). This similarity supports the relevance of the read-across.

Thus, the toxicity to soil macroorganisms is expected to be the same for the source and target substances.

Iron oxide isostearate is to be considered as cerium and iron oxide isostearate as to be non-toxic to the earthworm Eisenia foetida up to and including the highest nominal concentration of 1000 mg/kg dry soil in the 14-day test.

Endpoint:
toxicity to soil macroorganisms except arthropods: short-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 6 February 2008 to 26 May 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 207 (Earthworm, Acute Toxicity Tests)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
yes
Details on preparation and application of test substrate:
- Method of mixing into soil:
No aqueous application solution could be prepared for the dosing of the test item due to its limited water solubility. However, the test item was completely soluble in chloroform at the required concentrations. Thus, the test item was dissolved and diluted in chloroform and applied to a portion of sand.
Therefore, the application solution for the single test item concentration was prepared by dissolving 5570 mg of the test item completely in chloroform. The volume of the application solution was made up to 20 mL with chloroform resulting in a test item concentration of 278 mg/mL chloroform.
The volume of 10 mL of the application solution was applied to 50 g sand in a motar. Then the sand/application solution mixture was placed under a hood at room temperature for 1.5 hours and the solvent was completely evaporated. The remainder (sand/test item mixture) was intensively mixed by means of a pestle and the mixed on a roller mixer for 30 minutes. Then the sand/test item mixture was divided into aliquots of 10 g and filled into separate vials. The individual mixtures were prepared just before the start of the test.
The final sand/test item mixture was used to prepare the test medium replicates.
- Method of application to soil surface:
For each test vessel, 551 g of the prepared substrate was thoroughly mixed with 10 g sand/test item mixture, 3.3 g calcium carbonate and 189 mL purified water in a laboratory mixer.
- Controls: yes (same procedure without test item)
- Chemical name of vehicle: chloroform
- Evaporation of vehicle before use: yes
Test organisms (species):
Eisenia fetida
Animal group:
annelids
Details on test organisms:
TEST ORGANISM
- Common name: redworm, brandling worm, tiger worm, red wiggler worm
- Source: from a breeding stock maintained at RCC
- Age at test initiation: adults with a clitellum (about 4-5 months old)
- Weight at test initiation: 418 to 474 mg

ACCLIMATION
- Acclimation period: one day
- Acclimation conditions: same as test
- Health during acclimation: data not available
Study type:
laboratory study
Substrate type:
artificial soil
Limit test:
yes
Total exposure duration:
14 d
Post exposure observation period:
none
Test temperature:
20-21°C
pH:
initial pH: 6.3
final pH: 5.7 (control) to 5.9 (1000 mg/kg d.w.)
Moisture:
initial value: 35%
final value (after 14 days): 32 % (1000 mg/kg d.w.) - 33 % (control)
Details on test conditions:
TEST SYSTEM
- Test container (material, size): cylindrical glass vessel (diameter 10cm, height 14cm, volume ca. 1L)
- Amount of soil or substrate: 556 g artificial soil (dry weight)
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 4

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
The artificial soil was prepared according to the test guideline with the following constituents (% based on dry weight):
- Sphagnum peat (shredded, sieved through 2mm sieve): 10%
- Kaolinite clay (content of Al2O3: 35.5%): 20%
- Sand (Sihelco 36): 70%
- Calcium carbonate: 0.6%
- Storage: no data available
- Stability and homogeneity of test material in the medium: data not available

OTHER TEST CONDITIONS
- Photoperiod: continuous illumination
- Light intensity: 571 - 644 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- mortality and symptoms of toxicity (e.g. abnormal behaviour): after 7 and 14 days of exposure
- body weight: at the start and at the end of the test. For the purpose of this measurement, worms were quickly washed and the surplus was absorbed on filter paper. The surviving worms were then weighed all together and the total weight was divided by the number of surviving worms.
- other measurements: soil moisture (at the start and at the end of the test), pH (at the start and at the end of the test), temperature (continuously)

VEHICLE CONTROL PERFORMED: no

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not applicable (limit test)
- Range finding study: yes
- Test concentrations: up to 1000 mg/kg dry soil
- Results used to determine the conditions for the definitive study: no toxicity up to and including 1000 mg/kg dry soil
Nominal and measured concentrations:
nominal concentration: 1000 mg/kg dry soil
Reference substance (positive control):
yes
Remarks:
2-chloroacetamide (once a year, at 8, 14, 25, 45 and 80 mg/kg d.w.)
Key result
Duration:
14 d
Dose descriptor:
LC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
14 d
Dose descriptor:
LC0
Effect conc.:
>= 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
14 d
Dose descriptor:
LC100
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth
Remarks:
body weight
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth
Remarks:
body weight
Details on results:
- Mortality at end of exposure period: after 7 and 14 days of exposure, all test organisms survived at the single nominal test item concentration of 1000 mg/kg dry soil. Moreover, no abnormal behaviour of the test organisms or other symptoms of toxicity were recorded in the worms at this treatment group.
- Changes in body weight of live adults at end of exposure period: the mean body wet weight of the worms in the control vessels was 433 mg at the beginning and 431 mg at the end of the test. Thus, practically no change in the mean body wet weight of the worms in the control was determined during the exposure period of 14 days. In the treated soil, a slight reduction of the mean wet weight of the test organisms was 4%, which was statistically significantly higher compared to the control (Student-t-test, one-sided smaller, p = 0.05). However, the body weight loss was lower than 5% and was considered not to be biologically significant.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 14-day LC50 = 26 mg/kg dry soil (95% CL: 14-46 mg/kg dry soil) (acceptance range: 19-55 mg/kg dry soil)
Reported statistics and error estimates:
The NOEC and the LC0 were deduced directly from the raw data. The LOEC, LC50 and LC100 could not been calculated as no adverse effects were observed. Changes in the body weight of treated worms were compared to the control values and were statistically evaluated using a Student t test.

Table 1: mortality of Eisenia fetida

Nominal test item concentration (mg/kg dry soil)

Replicates

Vessel No.

Number of earthworms exposed

Number of missing or dead earthworms

% mortality (average per group)

Day 7

Day 14

Day 7

Day 14

Control

1

2

3

4

10

10

10

10

0

0

0

0

0

0

0

0

0

0

 

1000

1

2

3

4

10

10

10

10

0

0

0

0

0

0

0

0

0

0

Table 2: mean body weight of Eisenia fetida

Nominal test item concentration (mg/kg dry soil)

Mean body weight per worm at Day 0 (mg)

Mean body weight per worm at Day 14 (mg)

Mean change in body weight per worm between Days 0 and 14 (mg)

Difference compared to control (%)

Statistical significance

Control

433 +/- 10

431 +/- 18

-2 +/- 9

/

/

1000

453 +/- 22

436 +/- 18

-17 +/- 9

-4%

Significant

Validity criteria fulfilled:
yes
Conclusions:
Cerium and iron oxide isostearate proved to be non-toxic to the earthworm Eisenia fetida up to and including the highest nominal concentration of 1000 mg/kg dry soil in the 14-day test.
Executive summary:

Cerium and iron oxide isostearate has been tested for acute toxicity to Eisenia foetida. The study was carried out according to the OECD Guideline 207 and in compliance with GLP. Worms were exposed to a control and to cerium and iron oxide isostearate mixed with artificial soil at a concentration of 1000 mg/kg of dry soil for a 14-day period (limit test). Mortality and symptoms of toxicity were investigated after 7 and 14 days of exposure. Body weight was measured at the start and at the end of the test. No significant biological effect with respect to survival, weight, behaviour or appearance was observed. The NOEC is equal or higher than 1000 mg/kg dry soil. Cerium and iron oxide isostearate is considered as not harmful to the tested terrestrial organism.

Description of key information

By analogy with cerium and iron oxide isostearate (active matter of DPX10), iron oxide isostearate (active matter of DPX13) should not have any acute effect on earthworms.

Key value for chemical safety assessment

Additional information

One GLP-compliant study performed according to OECD guideline 207 is available on the analogue, cerium and iron oxide isostearate (active matter of DPX10). It is quoted as reliability 1 according to Klimisch criteria and flagged as a key study.