Silicon dioxide

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

a short-term study does not need to be conducted because an appropriate long-term toxicity study on terrestrial organisms is available

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 January 2019 to 16 March 2019 (in-life period)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Version / remarks:

2016

Deviations:

yes

Remarks:

Test concentrations were higher than limit recommended by the guideline due to the expected non-toxicity. Water content varied more than 10% on day 56 from that at the beginning of the test in all groups.

Qualifier:

according to guideline

Guideline:

ISO 11268-2 (Effects of Pollutants on Earthworms. 2. Determination of Effects on Reproduction)

Version / remarks:

2012

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil: The corresponding amount of the test item for each treatment and the remaining 10% of the quartz sand were directly incorporated into the artificial soil to prepare each test item concentration by thoroughly mixing for 5 minutes (until visual homogeneity) per treated soil. Per test vessel an amount corresponding to 500 g dw was used.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

Earthworms as used in this study, Eisenia fetida (Lumbricidae, Earthworms) are kept at the laboratory performing the study since February 1994. They were originally delivered by Co. Landenberger/Schömberg. The adult earthworms were fed with finely ground cow manure (free of growth promoters, nematicides or similar veterinary pharmaceuticals).

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Moisture:

In the lowest dose group, soil moisture content exceeded the recommended value slightly (62.5% versus 60%); this was considered to have no influence on the validity of the study results

Nominal and measured concentrations:

The nominal test concentrations were 0 (controls), 6.25, 12.5, 25.0, 50 and 100 g/kg soil(dw. Due to a preparation error in the low dose the actual concentration was 8.57 g/kg soil (dw) instead of 6.25 g/kg soil (dw)

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

100 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

100 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

- Mortality at end of 28-day exposure period: no mortality in adults observed. Mortality in controls was 1.25%.
- Changes in body weight of live adults (biomass mean change in % of initial weight per replicate) at end of exposure period: 35.4, 34.2, 35.3, 42.3, 42.7 and 45.7% in controls, 6.25, 12.5, 25.0, 50 and 100 g/kg soil(dw) groups;
- Number of offspring produced (% of controls): 107.8, 117.0, 101.2, 97.2, 87.2% in 6.25, 12.5, 25.0, 50 and 100 g/kg soil(dw) groups;
- No. of unhatched cocoons:
- Morphological abnormalities:
- Behavioural abnormalities:
- Other biological observations:

Results with reference substance (positive control):

The EC50 value for boric acid tested as the toxic reference in a separate GLP study was calculated by Probit analysis using Linear Max. Likelihood Regression as 329.8 mg boric acid/kg soil (dw) (95% confidence limits = 288.7 – 382.8 mg boric acid/kg soil (dw)). The estimated EC50 value in this study is slightly lower than the expected range of 400-600 mg boric acid/ kg soil (dw). This shows an acceptable sensitivity of the test system.

Reported statistics and error estimates:

Probit analysis using maximum likelihood regression and Fisher’s exact binomial test with Bonferroni Correction (one-sided, α = 0.05) for mortality; Dunnett’s t-test for reproduction (one-sided, α = 0.05); and Dunnett’s t-test for biomass change (one-sided, α = 0.05)

Validity Criteri

Mortality of the adult test animals in the control:	1.3%
(required: equal or less than 10%)
Mean number of juveniles per replicate in the control (±standard deviation):	378.9 ± 43.3
(required: ≥ 30)
The coefficient of variation for the number of juveniles in the control:	11.4%
(required:≤30%)

  

Validity criteria fulfilled:

yes

Conclusions:

No adverse effects on mortality, biomass change and reproduction were observed.

Executive summary:

A GLP study was performed in accordance with current OECD guideline and ISO standard to determine the NOEC and LOEC values for the effects of the test item on the reproduction (56 days after application), as well as on mortality and biomass development (28 days after application) of the earthwormEisenia fetida, using a standardised artificial soil with 10% peat. The test item was mixed with the substrate. NOECs for mortality and biomass development were determined at 100.0 g/kg soil (dw); the NOEC for reproduction was at 100.0 g/kg soil (dw).

Reference 3

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 January 2019 to 21 March 2019 (in-life period)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Version / remarks:

2016

Deviations:

yes

Remarks:

Test concentrations were higher than limit recommended by the guideline due to the expected non-toxicity. Water content varied more than 10% on day 56 from that at the beginning of the test in all groups except for the highest concentration

Qualifier:

according to guideline

Guideline:

ISO 11268-2 (Effects of Pollutants on Earthworms. 2. Determination of Effects on Reproduction)

Version / remarks:

2012

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil: The corresponding amount of the test item for each treatment and the remaining 10% of the quartz sand were directly incorporated into the artificial soil to prepare each test item concentration by thoroughly mixing for 5 minutes (until visual homogeneity) per treated soil. Per test vessel an amount corresponding to 500 g dw was used

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

Earthworms as used in this study, Eisenia fetida (Lumbricidae, Earthworms) are kept at the laboratory performing the study since February 1994. They were originally delivered by Co. Landenberger/Schömberg. The adult earthworms were fed with finely ground cow manure (free of growth promoters, nematicides or similar veterinary pharmaceuticals).

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Post exposure observation period:

no

Test temperature:

18.8 – 20.7°C

pH:

soil pH-value (day 0): 5.5 – 5.8;
soil pH-value (day 56): 5.8 – 6.5

Moisture:

soil moisture (day 0): 49.8 – 55.4% of the maximum water capacity (WHCmax),
soil moisture (day 56): 53.0 – 70.1% of the WHCmax;
The water content of the test substrate was checked weekly by reweighing the test vessels and losses of water were compensated

Nominal and measured concentrations:

The nominal test concentrations were 0 (controls), 6.25, 12.5, 25.0, 50.0 and 100.0 g test item/kg soil dry weight (dw)

Reference substance (positive control):

yes

Remarks:

Boric acid

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

50 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 2.5% mortality

Key result

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

100 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 97.5% mortality

Key result

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

70 700 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% CI 67.4-74.2 g/kg soil (dw)

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

50 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: biomass change

Remarks on result:

other: due to high mortality at 100.0 g/kg soil (dw), biomass change could not be calculated and the concentration was excluded from the statistical analysis

Key result

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

25 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

8 wk

Dose descriptor:

EC10

Effect conc.:

26 800 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: 95% CI 17.7-32.1 g/kg soil (dw)

Key result

Duration:

8 wk

Dose descriptor:

LOEC

Effect conc.:

50 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

8 wk

Dose descriptor:

EC50

Effect conc.:

50 400 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: 95%CI 47.1-54.8 g/kg soil (dw)

Details on results:

- Mortality at day 28: 2.5% and 97.5% in the two highest test concentrations, respectively. No mortality was observed in controls.
- Total mass of adults on day 28: no worms were found in the highest test concentration; thus, no biomass change could be calculated and the concentration was excluded from the statistical analysis. Statistical analysis showed no significant difference (Dunnett’s t-test, one-sided; α = 0.05) concerning biomass development of individual adults over 28 days between the control and the remaining four concentrations.
- Changes in body weight of live adults (biomass mean change in % of initial weight per replicate) at end of exposure period: 58.1, 66.8, 59.3, 57.7, and 71.9% in controls, 6.25, 12.5, 25.0, and 50.0 g/kg soil(dw) groups;
- Food consumption of adults during 28 days: no food was consumed in the highest test concentration;
- Number of offspring produced (% of controls): 99.7, 100.1, 93.1, 50.7*, 0.0* % in 6.25, 12.5, 25.0, 50.0 and 100.0 g/kg soil(dw) groups; *:significantly different;
- The test substrate with the two highest test concentrations was very dry. On day 1, in all replicates of the highest test concentration (100.0 g test item/kg soil (dw)) 8 - 10 worms were on the surface of the test substrate. During the first three weeks, dead earthworms were removed from the replicates of the highest test concentration.

Results with reference substance (positive control):

In a separate GLP study with boric acid, the LC50 value was calculated by Weibull analysis using Linear Max. Likelihood Regression as 329.8 mg boric acid/kg soil (dw) (95% confidence limits = 288.7 – 382.8 mg boric acid/kg soil (dw)). The estimated LC50 value in this study is slightly lower than the expected range of 400-600 mg boric acid/ kg soil (dw) and demonstrates the sensitivity of the test system.

Reported statistics and error estimates:

Trimmed Spearman-Karber procedure and step-down Rao-Scott-Cochran-Armitage Test (one-sided, α = 0.05) for mortality; Weibull analysis using maximum likelihood regression and Williams t-test for reproduction (one-sided, α = 0.05); and Dunnett’s t-test for biomass change (two-sided, α = 0.05)

Validity criteria:

Mortality of the adult test animals in the control:	0.0%
(required: equal or less than 10%)
Mean number of juveniles per replicate in the control (±standard deviation):	372.6 ± 54.7
(required: ≥ 30)
The coefficient of variation for the number of juveniles in the control:	14.7%
(required:≤30%)

Validity criteria fulfilled:

yes

Conclusions:

In an earthworm study, the NOECs for mortality and reproduction were at 50.0 and 25.0 g/kg soil (dw), respectively.

Executive summary:

A GLP study was performed in accordance with current OECD guideline and ISO standard to determine the NOEC, LOEC, EC10 and EC50 values for the effects of the test item on the reproduction (56 days after application), as well as on mortality and biomass development (28 days after application) of the earthworm Eisenia fetida, using a standardised artificial soil with 10% peat. The test item was mixed with the substrate. Additionally, the LC50 for the effects of the test item on the mortality of the adults was determined. NOECs for mortality and biomass development were determined at 50.0 g/kg soil (dw); the LC50 was at 70.7 g/kg soil (dw) (95% CI 67.4 - 74.2 g/kg soil(dw)); the NOEC for reproduction was at 25.0 g/kg soil (dw). At the effect levels, the substrate was very dry. This indicates that the effects might have been secondary to exsiccation.

Reference 4

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 February 2019 to 09 April 2019 (in-life period)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Version / remarks:

2016

Deviations:

yes

Remarks:

Test concentrations higher than limit recommended by the guideline due to the expected non-toxicity of the material. The control substrate had a slightly lower pHof 5.4 at test start.This deviation has no impact on the reliability of the study results.

Qualifier:

according to guideline

Guideline:

ISO 11268-2 (Effects of Pollutants on Earthworms. 2. Determination of Effects on Reproduction)

Version / remarks:

2012

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

-The needed amount of the test item was weighed for each concentration separately and mixed with an amount of deionized water to adjust the final soil moisture of 40 to 60% of WHCmax, taking into account that the test item contains 60% water. Afterwards, these mixtures were added to the 2100 g (dw) artificial soil to reach the desired concentrations. The prepared soil was mixed for 5 minutes.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

Earthworms as used in this study, Eisenia fetida (Lumbricidae, Earthworms) are kept at the laboratory performing the study since February 1994. They were originally delivered by Co. Landenberger/Schömberg. The adult earthworms were fed with finely ground cow manure (free of growth promoters, nematicides or similar veterinary pharmaceuticals).

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Post exposure observation period:

no

Test temperature:

18.7 – 20.5°C

pH:

soil pH-value (day 0): 5.4 – 6.0 (recommended 6 ± 0.5);
soil pH-value (day 56): 6.2 – 6.7

Moisture:

soil moisture (day 0): 48.7 – 55.6% of the maximum water capacity (WHCmax),
soil moisture (day 56): 50.2 – 66.5% of the WHCmax;
The water content of the test substrate was checked weekly by reweighing the test vessels and losses of water were compensated (note: this measure is not compensating the water absorbed by the test item);

Details on test conditions:

Five treatments plus water control, 4 replicates per treatment, 8 for the control

Nominal and measured concentrations:

The nominal test concentrations were 0 (controls), 6.25, 12.5, 25.0, 50.0 and 100.0 g SAS/kg soil dry weight (dw)

Reference substance (positive control):

yes

Remarks:

Boric acid was tested in a separate GLP study

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

100 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

50 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

8 wk

Dose descriptor:

LOEC

Effect conc.:

100 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

- Adult mortality at day 28: 5% and 2.5% mortality at 6.25 and 12.5 g/kg soil (dw), respectively. Mortality in controls: 1.3%. Fisher’s exact binomial test with Bonferroni Correction (one-sided, α = 0.05) showed no significant difference concerning mortality between the control and all concentrations of the test item tested;
- Total mass of adults on day 28: Statistical analysis showed a significant difference (Williams t-test, two-sided; α = 0.05) concerning biomass development of individual adults over 28 days between the control and highest concentration of the test item tested, i.e. 100.0 g SAS/kg soil (dw).
- Changes in body weight of live adults (biomass mean change in % of initial weight per replicate) at end of exposure period: 47.3, 51.4, 57.0, 56.7, 53.9 and 62.6* % in controls, 6.25, 12.5, 25.0, 50.0 and 100.0 g SAS/kg soil(dw) groups;
- Food consumption of adults during during 28 days:In all test vessels the administered food was almost fully consumed by the worms during the first four weeks.
- No effects on behaviour or morphology of the adult earthworms were observed.
- Number of offspring produced (% of controls):114.4, 105.1, 111.7, 88.0, 70.3* % in 6.25, 12.5, 25.0, 50.0 and 100.0 g SAS/kg soil(dw) groups *:significantly different (Williams t-test for reproduction (one-sided, α = 0.05);
The test substrate with the two highest test concentrations was very dry.

Results with reference substance (positive control):

In a separate GLP study with boric acid, the LC50 value was calculated by Weibull analysis using Linear Max. Likelihood Regression as 329.8 mg boric acid/kg soil (dw) (95% confidence limits = 288.7 – 382.8 mg boric acid/kg soil (dw)). The estimated LC50 value in this study is slightly lower than the expected range of 400-600 mg boric acid/ kg soil (dw) and demonstrates the sensitivity of the test system.

Reported statistics and error estimates:

Probit analysis using maximum likelihood regression and Fisher’s exact binomial test with Bonferroni Correction (one-sided, α = 0.05) for mortality; Williams t-test for reproduction (one-sided, α = 0.05); and Williams t-test for biomass change (two-sided, α = 0.05)

Validity criteria:               

Mortality of the adult test animals in the control:	1.3%
(required: equal or less than 10%)
Mean number of juveniles per replicate in the control (±standard deviation):	386.0 ± 81.3
(required: ≥ 30)
The coefficient of variation for the number of juveniles in the control:	21.1%
(required:≤30%)

Validity criteria fulfilled:

yes

Conclusions:

In an earthworm study, the NOECs for mortality and reproduction were at 100.0 and 50.0 g SAS/kg soil (dw), respectively.

Executive summary:

A GLP study was performed in accordance with current OECD guideline and ISO standard to determine the NOEC and LOEC values for the effects of the test item on the reproduction (56 days after application), as well as on mortality and biomass development (28 days after application) of the earthworm Eisenia fetida, using a standardised artificial soil with 10% peat. The test item was mixed with the substrate. NOECs for mortality and biomass development were determined at 100.0 and 50.0 g SAS/kg soil (dw), respectively; the NOEC for reproduction was at 50.0 g SAS/kg soil (dw).

Reference 5

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 January 2019 to 27 March 2019 (in-life period)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Version / remarks:

2016

Deviations:

yes

Remarks:

Test concentrations higher than limit recommended by the guideline due to the expected non-toxicity of the material. Water content varied more than 10% on day 56 from that at the beginning of the test in all groups except for the highest concentration.

Qualifier:

according to guideline

Guideline:

ISO 11268-2 (Effects of Pollutants on Earthworms. 2. Determination of Effects on Reproduction)

Version / remarks:

2012

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil: The corresponding amount of the test item for each treatment and the remaining 10% of quartz sand were directly incorporated into the artificial soil to prepare each test item concentration by thoroughly mixing for 5 minutes (until visual homogeneity) per treated soil. Per test vessel an amount corresponding to 500 g dw was used

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

Earthworms as used in this study, Eisenia fetida (Lumbricidae, Earthworms) are kept at the laboratory performing the study since February 1994. They were originally delivered by Co. Landenberger/Schömberg. The adult earthworms were fed with finely ground cow manure (free of growth promoters, nematicides or similar veterinary pharmaceuticals).

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Test temperature:

18.8 – 20.3°C

pH:

soil pH-value (day 0): 5.4 – 5.6 (recommended 6 ± 0.5);
soil pH-value (day 56): 5.8 – 6.4

Moisture:

soil moisture (day 0): 47.6 – 53.3% of the maximum water capacity (WHCmax),
soil moisture (day 56): 50.1 – 63.1% of the WHCmax;
The water content of the test substrate was checked weekly by reweighing the test vessels and losses of water were compensated (note: this measure is not compensating the water absorbed by the test item);

Nominal and measured concentrations:

The nominal test concentrations were 0 (controls), 6.25, 12.5, 25.0, 50.0 and 100.0 g test item/kg soil dry weight (dw)

Reference substance (positive control):

yes

Remarks:

Boric acid was tested in a separate GLP study

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

50 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 5% mortality

Key result

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

100 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 100% mortality

Key result

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

69 700 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% CI 57.5-3098.8 g/kg soil (dw)

Key result

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

25 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

8 wk

Dose descriptor:

LOEC

Effect conc.:

50 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

- Mortality at day 28: 5.0% and 10.0% in the two highest test concentrations, respectively. No mortality was observed in controls.
- Total mass of adults on day 28: no worms were found in the highest test concentration; thus, no biomass change could be calculated and the concentration was excluded from the statistical analysis. Statistical analysis showed no significant difference (Dunnett’s t-test, two-sided; α = 0.05) concerning biomass development of individual adults over 28 days between the control and the remaining four concentrations.
- Changes in body weight of live adults (biomass mean change in % of initial weight per replicate) at end of exposure period: 39.7, 42.6, 45.9, 46.8, 39.7% in controls, 6.25, 12.5, 25.0, and 50.0 g/kg soil(dw) groups;
- Food consumption of adults during during 28 days: no food was consumed in the highest test concentration; less than half was consumed on d28 in the 50.0g/kg soil(dw) group;
- Number of offspring produced (% of controls): 105.2, 104.7, 85.5, 19.1**, 0.0** % in 6.25, 12.5, 25.0, 50.0 and 100.0 g/kg soil(dw) groups **:significantly different;
The test substrate with the two highest test concentrations was very dry.

Results with reference substance (positive control):

In a separate GLP study with boric acid, the LC50 value was calculated by Weibull analysis using Linear Max. Likelihood Regression as 329.8 mg boric acid/kg soil (dw) (95% confidence limits = 288.7 – 382.8 mg boric acid/kg soil (dw)). The estimated LC50 value in this study is slightly lower than the expected range of 400-600 mg boric acid/ kg soil (dw) and demonstrates the sensitivity of the test system.

Reported statistics and error estimates:

Weibull analysis using maximum likelihood regression and Fisher’s Exact Binomial Test with Bonferroni-Holm Correction (one-sided, α = 0.05) for mortality; Williams t-test for reproduction (one-sided, α = 0.05); and Dunnett’s t-test for biomass change (two-sided, α = 0.05)

Validity criteria:              

Mortality of the adult test animals in the control:	0.0%
(required: equal or less than 10%)
Mean number of juveniles per replicate in the control (±standard deviation):	359.3± 46.4
(required: ≥ 30)
The coefficient of variation for the number of juveniles in the control:	12.9%
(required:≤30%)

Validity criteria fulfilled:

yes

Conclusions:

In an earthworm study, the NOECs for mortality and reproduction were at 50.0 and 25.0 g/kg soil (dw), respectively. Effects might be secondary to exsiccation.

Executive summary:

A GLP study was performed in accordance with current OECD guideline and ISO standard to determine the NOEC and LOEC values for the effects of the test item on the reproduction (56 days after application), as well as on mortality and biomass development (28 days after application) of the earthworm Eisenia fetida, using a standardised artificial soil with 10% peat. The test item was mixed with the substrate. Additionally, the LC50 for the effects of the test item on the mortality of the adults was determined. NOECs for mortality and biomass development were determined at 50.0 g/kg soil (dw); the LC50 was at 69.7 g/kg soil (dw) (95% CI 57.5 - 3098.8 g/kg soil(dw)); the NOEC for reproduction was at 25.0 g/kg soil (dw). At the effect levels, the substrate was very dry. This indicates that the effects might have been secondary to exsiccation.

Description of key information

In GLP studies on earthworms with different forms of synthetic amorphous silica (SAS), the lowest NOECs for mortality and reproduction were at 50 g/kg soil (dw) and 25 g/kg soil (dw), respectively. Hence, no toxicity was found at exposures exceeding current maximum recommended test concentrations.

At the effect levels (LC50s: 70 g/kg soil (dw) and higher; LOECs, reproduction: 50 g/kg soil(dw) and higher), the substrate was very dry. This indicates that the effects were secondary to exsiccation (as also verified by histopathology).

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

70 000 mg/kg soil dw

Long-term EC10, LC10 or NOEC for soil macroorganisms:

25 000 mg/kg soil dw

Additional information

No effects were observed up to the concentration limit of 1000mg/kg recommended in the current OECD TG 222.