Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to soil macroorganisms except arthropods

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE READ-ACROSS APPROACH (ENDPOINT LEVEL)
The REACH registration of silver (powder and massive forms of zero-valent, elemental, silver) is underpinned, in common with other metals, by a read-across (or analogue) approach from the properties of the free ion. This principle of read-across from the free ion has been extended to also include nanosilver.
The scientific validity of read-across from the hazard properties of ionic silver (source) to nanosilver (target) under REACH is underpinned by both theoretical and empirical considerations.
The theoretical basis for the use of ionic silver data as the foundation of the risk assessment of nanosilver is based on the premise that the free metal ion (Me+) is the most toxic metal form/species (Starodub et al. 1987). This consideration was implicit in the development of the Free Ion Activity Model [FIAM] (Morel 1983, Paquin et al. 2002, Campbell 1985, Brown and Markich 2000) and, more recently, the Biotic Ligand Model [BLM] (Paquin et al 2002, Niyogi and Wood 2004) that has underpinned the risk assessment of several metals (e.g. Cu, Ni, Zn) under the Existing Substance Regulations and REACH; and most recently the development of the Environmental Quality Standard (EQS) for nickel and nickel substances under the Water Framework Directive (WFD). When considered on an equal mass basis ionic silver would therefore be expected to have greater toxicity than nanosilver simply on the basis that silver ions are released over time from the surface of particles (via oxidative dissolution). As the properties of nanosilver are read-across directly from ionic silver (not just to the fraction of silver ions released from nanosilver), this read-across is also expected to introduce considerable precaution into the hazard component of the risk assessment of nanosilver as all nanosilver, irrespective of coating, morphology or particle size distribution is assumed to behave similarly to the free ion.
This theoretical consideration has been tested by conducting a comprehensive review of the available scientific literature for nanosilver, with particular emphasis on the comparative effects on REACH relevant biotic systems (REACH information requirement) of ionic silver and nanosilver. This review is described for each endpoint in subsequent sections of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IULCID Section 13) and is summarised below. Furthermore, this theoretical consideration was confirmed by a specific ecotoxicity testing programme undertaken by the EPMF following the silver substance evaluation and designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms.

2. READ-ACROSS APPROACH JUSTIFICATION (ENDPOINT LEVEL)
In terms of ecotoxicity, nanosilver on an equal mass basis has been found to be significantly less toxic than ionic silver for the majority of REACH endpoints and of equivalent toxicity for some others. None of the empirical information available suggests that nanosilver is consistently more hazardous than ionic silver on an equivalent mass basis, or that “nano-specific” effects that would prejudice the validity of read across from ionic silver to nanosilver occur. In addition, with very limited exceptions which are described further in the report ‘Nanosilver: read-across justification for environmental information requirements’, none of the available data suggested consistent relationships between particle morphology, size, particle size distribution (raw or agglomerated) or coating (surface treatment) and effects.
Notter et al. (2014) presents a meta-analysis of published EC50 values for ionic silver and nanosilver. The authors demonstrate that almost 94% of acute toxicity values assessed for freshwater, seawater and terrestrial systems using algae, annelid, arthropoda, bacteria, crustacea, fish, nematoda, plant, protozoa and rotatoria show that the nanoform of silver is less toxic than the dissolved metal (when normalised for total metal concentration).
In addition, a specific ecotoxicity testing programme designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms was undertaken following the silver substance evaluation. This demonstrated that the nanoform of silver is less toxic than ionic silver (based on EC10 and EC50 values for total, ‘conventional’ dissolved (<0.45μm) and ‘truly’ dissolved (<3kDa) silver). Therefore, taking the full body of evidence into account, the read-across use of toxicity values from ionic to nanosilver as a ‘worst case’ approach is justified and scientifically defensible for environmental endpoints. The Substance Evaluation Conclusion document for silver agreed with this conclusion for the nanosilver forms covered in the REACH dossier (RIVM 2018).

Toxicity to soil macro-organisms
There are three studies reporting the long-term toxicity of various sizes of nanoparticles and coating types to terrestrial invertebrates included in the REACH dossier as Endpoint Study Records. These comparative long-term (28d) studies for earthworms all report effects thresholds (EC10) for nanosilver that are less sensitive or of comparable sensitivity to those for ionic silver. There is insufficient long-term data for terrestrial invertebrates to conclude on the influence of particle size or particle coating on terrestrial ecotoxicity. Together with the theoretical basis for read-across based on the free-ion, this supports the use of ionic silver as the ‘worst case’ basis to read across properties to nanosilver. A summary of these supporting studies is available under Section 4.3.1 of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IUCLID Section 13).



For further information and data matrix see 'CSR Annex 9 - Read Across Justification Nanosilver ENV_SUMMARY_200706' attached in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
> 8 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Houthalen soil, unleached, 95% CL = not calculated
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
> 16 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Bordeaux soil, unleached, 95% CL = not calculated
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
63 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Inman Valley soil, unleached, 95% CL = 41-101
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
77 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Charleston soil, unleached, 95% CL = na-125
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
5.3 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Kingaroy soil, unleached, 95% CL = na-24
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
141 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Bakalava soil, unleached, 95% CL = 99-196
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
36 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality
Remarks on result:
other: Port Kenny soil, unleached, 95% CL = na-71
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
> 8 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Houthalen soil, unleached, 95% CL = not calculated
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
12 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Bordeaux soil, unleached, 95% CL = 6.2-na
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
83 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Inman Valley soil, unleached, 95% CL = 41-133
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
62 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Charleston soil, unleached, 95% CL = 39-91
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
> 101 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Kingaroy soil, unleached, 95% CL = not calculated
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
74 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Bakalava soil, unleached, 95% CL = 35-133
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
> 80 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: Port Kenny soil, unleached, 95% CL = not calculated
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
> 160 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
growth
Remarks on result:
other: South East soil, unleached, 95% CL = not calculated
Duration:
70 d
Dose descriptor:
EC10
Effect conc.:
67 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
element
Basis for effect:
reproduction
Remarks on result:
other: Inman Valley soil, unleached, 95% CL = 41-105
Duration:
70 d
Dose descriptor:
EC10
Effect conc.:
5.9 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
element
Basis for effect:
reproduction
Remarks on result:
other: Kingaroy soil, unleached, 95% CL = na-58
Duration:
70 d
Dose descriptor:
EC10
Effect conc.:
64 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
reproduction
Remarks on result:
other: Bkalava soil, unleached, 95% CL = na
Duration:
70 d
Dose descriptor:
EC10
Effect conc.:
0.2 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
reproduction
Remarks on result:
other: Port Kenny soil, unleached, 95% CL = na-5.2
Duration:
70 d
Dose descriptor:
EC10
Effect conc.:
5.5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
reproduction
Remarks on result:
other: South East soil, unleached, 95% CL = na-11
Details on results:
- Mortality at end of exposure period: There was no significant decrease in the survival of earthworms with increasing Ag concentrations in the Houthalen and Bordeaux soils. For the remaining soils a dose response relationship was observed with increasing Ag concentration. The survival of earthworms in the control soils after 28 days varied considerably across the study soils ranging from approximately 60% to 100% survival.

- Changes in body weigth of live adults (% of initial weight) at end of exposure period: The dose response analysis of the data showed that for many soils there was no decrease in earthworm growth with increasing Ag concentration. In several cases some growth was observed in the control soils, however, in the majority of cases the earthworms decreased in weight during the initial 28 days of the test.

- No. of offspring produced: The number of juveniles per adult worm at the completion of the test was highly variable and in the majority of cases below the validation level for the test (i.e. 3 juveniles/adult worm). In addition, the variability between the replicates was high and in most cases exceeded an RSD of 30%. In the Houthalen and Bordeaux soil there were no juveniles found in the controls. This is likely due to a negative effect of the low pH on the hatching and survival of juveniles. In addition, in the Charleston unleached treatment there was less than 0.2 juveniles produced per adult worm. Based on these low results in these cases, no further data analysis was conducted on these data.
Reported statistics and error estimates:
The data from the test endpoints were fitted to dose response models to determine the concentration that produced a 10% and 50% reduction relative to the controls (EC10 and EC50 respectively) using GraphPab Prism®.
In some cases, the toxicity data showed stimulation in the response relative to the controls at low Ag concentrations (i.e. hormesis), as a result, one of two dose response models were used to fit the data and derive ECx values depending on this response. In cases where there was no significant increase (p > 0.05) in the measured response at low Ag concentrations, a standard dose log-logistic model was used to fit the data (Equation 1) and derive ECx values. For dose response curves that showed a significant increase (p ≤ 0.05) in the response at low Ag concentrations, a non-linear model that accounted for hormesis was fitted to the data (Equation 2) (Brain and Cousens, 1989).
y=c+ (d-c)/(1+(x/e)^b ) (1)
y=c+(d-c +fx)/(1+(x/e)^b ) (2)

The EC10 and EC50 values were then determined in each case through interpolation from the fitted curve at a 10% and 50% reduction from the fitted d values (i.e. fitted response in the control).

Earthworm survival was presented as the percentage of worms present after 28 days relative to the initial number of worms (i.e. 10 worms). The tests were deemed valid if there was ≥ 90% survival in the control soils. The growth of the worms was presented as a relative weight change over the initial 28 days of the test. This was done by calculating the average weight per worm in each of the test containers at day 0 and day 28 and then determining the ratio of these two values (i.e. d28/d0).

The total number of juveniles that were present in each of the test containers at the completion of the second phase of the test was normalised to the number of juveniles per adult worm. For this normalisation, the number of adult worms that had been removed after the initial phase of the test was used. The test was deemed valid if there were ≥ 3 juveniles produced per adult worm and the RSD between the control samples was ≤ 30%(OECD, 2004).

Validity criteria fulfilled:
no
Remarks:
In some soils the survival in the controls was less than 90%. The number of juveniles per adult worm was highly variable and in the majority of cases was < 3 juveniles/adult worm. the variability between the replicates was high and in most cases >30%.
Conclusions:
All toxicity results should be used with caution as the validitiy criteria were not fulfilled. The most sensitive endpoint in the study was reproduction. The EC10 values based on this endpoint ranged from 0.2 (Port Kenny soil) to 67 (Inman Valley soil) mg Ag/kg in the unleached treatment.
Executive summary:

The earthworm toxicity study was conducted according to the OECD guideline 222 (Earthworm Reproduction Test) using the earthworm Eisenia fetida as the test species in a range of soils indicative of natural variability in soil conditions across the EU (pH 4.6 – 8.0, organic carbon 0.9 – 6.9, and clay 2.5 – 60%). Reproduction (number of juveniles) was found to be the most sensitive endpoint in the study. However, there were low juvenile counts in all of the soils (in most cases < 3 juveniles per worm) and in the case of the Houthalen and Bordeaux soils (both acidic), no juveniles were found at the completion of the test. The EC10 values based on this endpoint ranged from 0.2 (Port Kenny soil) to 67 (Inman Valley soil) mg Ag/kg in the unleached treatment. The EC10 values for survival were in the range of 5.3 (Kingaroy soil) – 141 (Balaklava soil) mg Ag/kg the unleached treatment. The toxicity of Ag to soil invertebrates appeared to be controlled primarily by organic carbon. The earthworm growth was also observed in the study, however due to the small number of EC10 and EC50 values that could be calculated from the data, no analysis was conducted to determine the effect of soil properties on this toxicity endpoint. 

Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE READ-ACROSS APPROACH (ENDPOINT LEVEL)
The REACH registration of silver (powder and massive forms of zero-valent, elemental, silver) is underpinned, in common with other metals, by a read-across (or analogue) approach from the properties of the free ion. This principle of read-across from the free ion has been extended to also include nanosilver.
The scientific validity of read-across from the hazard properties of ionic silver (source) to nanosilver (target) under REACH is underpinned by both theoretical and empirical considerations.
The theoretical basis for the use of ionic silver data as the foundation of the risk assessment of nanosilver is based on the premise that the free metal ion (Me+) is the most toxic metal form/species (Starodub et al. 1987). This consideration was implicit in the development of the Free Ion Activity Model [FIAM] (Morel 1983, Paquin et al. 2002, Campbell 1985, Brown and Markich 2000) and, more recently, the Biotic Ligand Model [BLM] (Paquin et al 2002, Niyogi and Wood 2004) that has underpinned the risk assessment of several metals (e.g. Cu, Ni, Zn) under the Existing Substance Regulations and REACH; and most recently the development of the Environmental Quality Standard (EQS) for nickel and nickel substances under the Water Framework Directive (WFD). When considered on an equal mass basis ionic silver would therefore be expected to have greater toxicity than nanosilver simply on the basis that silver ions are released over time from the surface of particles (via oxidative dissolution). As the properties of nanosilver are read-across directly from ionic silver (not just to the fraction of silver ions released from nanosilver), this read-across is also expected to introduce considerable precaution into the hazard component of the risk assessment of nanosilver as all nanosilver, irrespective of coating, morphology or particle size distribution is assumed to behave similarly to the free ion.
This theoretical consideration has been tested by conducting a comprehensive review of the available scientific literature for nanosilver, with particular emphasis on the comparative effects on REACH relevant biotic systems (REACH information requirement) of ionic silver and nanosilver. This review is described for each endpoint in subsequent sections of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IULCID Section 13) and is summarised below. Furthermore, this theoretical consideration was confirmed by a specific ecotoxicity testing programme undertaken by the EPMF following the silver substance evaluation and designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms.

2. READ-ACROSS APPROACH JUSTIFICATION (ENDPOINT LEVEL)
In terms of ecotoxicity, nanosilver on an equal mass basis has been found to be significantly less toxic than ionic silver for the majority of REACH endpoints and of equivalent toxicity for some others. None of the empirical information available suggests that nanosilver is consistently more hazardous than ionic silver on an equivalent mass basis, or that “nano-specific” effects that would prejudice the validity of read across from ionic silver to nanosilver occur. In addition, with very limited exceptions which are described further in the report ‘Nanosilver: read-across justification for environmental information requirements’, none of the available data suggested consistent relationships between particle morphology, size, particle size distribution (raw or agglomerated) or coating (surface treatment) and effects.
Notter et al. (2014) presents a meta-analysis of published EC50 values for ionic silver and nanosilver. The authors demonstrate that almost 94% of acute toxicity values assessed for freshwater, seawater and terrestrial systems using algae, annelid, arthropoda, bacteria, crustacea, fish, nematoda, plant, protozoa and rotatoria show that the nanoform of silver is less toxic than the dissolved metal (when normalised for total metal concentration).
In addition, a specific ecotoxicity testing programme designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms was undertaken following the silver substance evaluation. This demonstrated that the nanoform of silver is less toxic than ionic silver (based on EC10 and EC50 values for total, ‘conventional’ dissolved (<0.45μm) and ‘truly’ dissolved (<3kDa) silver). Therefore, taking the full body of evidence into account, the read-across use of toxicity values from ionic to nanosilver as a ‘worst case’ approach is justified and scientifically defensible for environmental endpoints. The Substance Evaluation Conclusion document for silver agreed with this conclusion for the nanosilver forms covered in the REACH dossier (RIVM 2018).

Toxicity to soil macro-organisms
There are three studies reporting the long-term toxicity of various sizes of nanoparticles and coating types to terrestrial invertebrates included in the REACH dossier as Endpoint Study Records. These comparative long-term (28d) studies for earthworms all report effects thresholds (EC10) for nanosilver that are less sensitive or of comparable sensitivity to those for ionic silver. There is insufficient long-term data for terrestrial invertebrates to conclude on the influence of particle size or particle coating on terrestrial ecotoxicity. Together with the theoretical basis for read-across based on the free-ion, this supports the use of ionic silver as the ‘worst case’ basis to read across properties to nanosilver. A summary of these supporting studies is available under Section 4.3.1 of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IUCLID Section 13).


For further information and data matrix see 'CSR Annex 9 - Read Across Justification Nanosilver ENV_SUMMARY_200706' attached in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
104.8 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
mortality
Remarks on result:
other: Lufa 2.2
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
104.8 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
reproduction
Remarks on result:
other: Lufa 2.2
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
190.77 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
mortality
Remarks on result:
other: Lufa 2.2. 95% CI: 119-233 mg Ag/kg soil dw
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
254 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
reproduction
Remarks on result:
other: Lufa 2.2. 95% CI: 0-91.7 mg Ag/kg soil dw
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
104.8 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
mortality
Remarks on result:
other: Woburn
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
22.5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
reproduction
Remarks on result:
other: Woburn
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
86.73 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
mortality
Remarks on result:
other: Woburn
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
13.22 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Silver
Basis for effect:
reproduction
Remarks on result:
other: Woburn. 95% CI: 0-28.56 mg Ag/kg soil dw
Details on results:
Lufa 2.2
Results from study report
Survival LC50: 231.1 (validated nominal concentrations)
Reproduction EC50: 45.4 (validated nominal concentrations)
Survival and reproduction EC50: 161.2 (95% CI: 38.22-284.2) (nominal)

Estimates from ToxCalc
Survival:
NOEC = 104.8 mg/kg dwt – Homoscedastic t-test (Bonferroni)
LOEC = 352 mg/kg dwt – Homoscedastic t-test (Bonferroni)
EC10 = 190.77 (119.0 - 233.0) mg/kg dwt – Maximum likelihood logit
EC50 = 406.15 (357.2 – 510.36) mg/kg dwt – Maximum likelihood logit
Reproduction:
NOEC = 104.8 mg/kg dwt – Heteroscedastic t-test (Bonferroni)
LOEC = 352 mg/kg dwt – Heteroscedastic t-test (Bonferroni)
EC10 = 57.3 (0 – 91.07) mg/kg dwt – ICP
EC50 = 169.17 (84.13 – 215.23) mg/kg dwt – ICP

Lufa 2.2 - Worms exposed to 2 months aged soils (no leachings, soils were only incubated at the climate rooms)
Survival LC50: 318 (95% CI: 162-475) (nominal)
Reproduction EC50: 30 (95% CI: 16-43) (nominal)

Lufa 2.2 - Worms exposed to 7 months aged soils (no leachings, soils were only incubated at the climate rooms)
Survival LC50: 682 (nominal)
Reproduction EC50: 90 (95% CI: 29-151) (nominal)

Woburn
Results from study report
Survival LC50: 254 (S.E. = 22) (measured)
Reproduction EC50: 13.2 (S.E. = 4.2) (measured)
Reproduction EC10: 3.0 (S.E. = 0.6) (measured)
Survival and reproduction EC50: 33.1 (95% CI: 21.7-44.5) (nominal)

Estimates from ToxCalc
Survival:
NOEC = 104.8 mg/kg dwt – Homoscedastic t-test (Bonferroni)
LOEC = 352 mg/kg dwt – Homoscedastic t-test (Bonferroni)
EC10 = 86.73 mg/kg dwt – Non-linear interpolation
EC50 =258.87 mg/kg dwt – Non-linear interpolation
Reproduction:
NOEC = 22.5 mg/kg dwt – Homoscedastic t-test (Bonferroni)
LOEC = 56.3 mg/kg dwt – Homoscedastic t-test (Bonferroni)
EC10 = 13.22 (0 – 28.56) mg/kg dwt – ICP
EC50 = 37.29 (25.38 – 49.72) mg/kg dwt – ICP
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Additional estimates for chronic endpoints were determined using ToxCalc.

Lufa 2.2 soil (A)

Ag conc. (mg/kg) No. worms surviving Juveniles/worm/wk
0 9 1.919
0 10 1.400
0 10 0.975
0 10 0.625
0 10 1.100
0 10 2.375
9 10 1.868
9 10 1.450
9 10 1.325
22.5 10 1.250
22.5 10 0.975
22.5 10 1.725
56.3 10 1.175
56.3 10 1.425
56.3 10 1.450
104.8 10 1.025
104.8 9 1.108
104.8 10 0.842
352 10 0.000
352 3 0.000
352 5 0.037

Lufa 2.2 (b)

Ag conc. (mg/kg) No. worms surviving Juveniles
0.0 9 46
0.0 10 57
0.0 10 41
18.0 9 51
18.0 10 36
18.0 9 34
45.0 10 30
45.0 10 17
45.0 9 30
112.5 9 13
112.5 10 3
112.5 10 13
281.3 1 0
281.3 6 0
281.3 5 0
703.1 0 0
703.1 0 0
703.1 0 0
1757.8 0 0
1757.8 0 0
1757.8 0 0

Woburn soil

Ag conc. (mg/kg) No. worms surviving Juveniles/worm/wk
0 10 0.875
0 10 0.875
0 10 0.825
0 10 0.600
0 10 1.200
0 10 0.975
9 9 0.816
9 10 1.150
9 10 0.650
22.5 10 0.575
22.5 10 0.800
22.5 10 0.575
56.3 10 0.200
56.3 10 0.025
56.3 10 0.325
104.8 10 0.030
104.8 10 0.000
104.8 3 0.000
352 9 0.000
352 3 0.000
352 0 0.000

Chiltern soil

Ag conc. (mg/kg) No. worms surviving Juveniles/worm/wk
0 10 1.150
0 10 0.900
0 9 1.564
0 10 1.125
0 10 1.050
0 10 1.250
22.5 10 1.150
22.5 10 1.375
22.5 10 1.200
56.3 9 0.872
56.3 10 0.900
56.3 9 1.026
104.8 10 0.425
104.8 10 0.550
104.8 10 0.475
352 8 0.342
352 4 0.294
352 1 0.065
880 0 0.000
880 0 0.000
880 0 0.000

North Wales soil

Ag conc. (mg/kg) No. worms surviving Juveniles/worm/wk
0 10 2.675
0 10 2.450
0 10 3.375
0 10 2.350
0 10 2.700
0 10 2.100
9 10 1.625
9 10 2.625
9 10 2.500
22.5 10 1.600
22.5 10 1.925
22.5 10 1.950
56.3 10 1.950
56.3 10 2.175
56.3 10 1.725
104.8 10 1.575
104.8 10 1.700
104.8 10 2.175
352 5 0.172
352 10 0.625
352 8 0.294
Validity criteria fulfilled:
not specified
Conclusions:
The NOEC for survival and reproduction in Lufa 2.2 (A) and survival Woburn soil was 104.8 mg Ag/kg soil dw . The NOEC for reproduction in Woburn soil was 22.5 mg Ag/kg soil dw.
Executive summary:

The toxicity of silver nitrate to Eisenia fetida was determined in study following OECD guideline 222. Worms were exposed to silver nitrate in different substrates (Lufa 2.2, Woburn, North Wales and Chiltern soils) for 28 days and the effects on survival and reproduction were recorded. A summary of the study report is available as unpublished nanofate material.

Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE READ-ACROSS APPROACH (ENDPOINT LEVEL)
The REACH registration of silver (powder and massive forms of zero-valent, elemental, silver) is underpinned, in common with other metals, by a read-across (or analogue) approach from the properties of the free ion. This principle of read-across from the free ion has been extended to also include nanosilver.
The scientific validity of read-across from the hazard properties of ionic silver (source) to nanosilver (target) under REACH is underpinned by both theoretical and empirical considerations.
The theoretical basis for the use of ionic silver data as the foundation of the risk assessment of nanosilver is based on the premise that the free metal ion (Me+) is the most toxic metal form/species (Starodub et al. 1987). This consideration was implicit in the development of the Free Ion Activity Model [FIAM] (Morel 1983, Paquin et al. 2002, Campbell 1985, Brown and Markich 2000) and, more recently, the Biotic Ligand Model [BLM] (Paquin et al 2002, Niyogi and Wood 2004) that has underpinned the risk assessment of several metals (e.g. Cu, Ni, Zn) under the Existing Substance Regulations and REACH; and most recently the development of the Environmental Quality Standard (EQS) for nickel and nickel substances under the Water Framework Directive (WFD). When considered on an equal mass basis ionic silver would therefore be expected to have greater toxicity than nanosilver simply on the basis that silver ions are released over time from the surface of particles (via oxidative dissolution). As the properties of nanosilver are read-across directly from ionic silver (not just to the fraction of silver ions released from nanosilver), this read-across is also expected to introduce considerable precaution into the hazard component of the risk assessment of nanosilver as all nanosilver, irrespective of coating, morphology or particle size distribution is assumed to behave similarly to the free ion.
This theoretical consideration has been tested by conducting a comprehensive review of the available scientific literature for nanosilver, with particular emphasis on the comparative effects on REACH relevant biotic systems (REACH information requirement) of ionic silver and nanosilver. This review is described for each endpoint in subsequent sections of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IULCID Section 13) and is summarised below. Furthermore, this theoretical consideration was confirmed by a specific ecotoxicity testing programme undertaken by the EPMF following the silver substance evaluation and designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms.

2. READ-ACROSS APPROACH JUSTIFICATION (ENDPOINT LEVEL)
In terms of ecotoxicity, nanosilver on an equal mass basis has been found to be significantly less toxic than ionic silver for the majority of REACH endpoints and of equivalent toxicity for some others. None of the empirical information available suggests that nanosilver is consistently more hazardous than ionic silver on an equivalent mass basis, or that “nano-specific” effects that would prejudice the validity of read across from ionic silver to nanosilver occur. In addition, with very limited exceptions which are described further in the report ‘Nanosilver: read-across justification for environmental information requirements’, none of the available data suggested consistent relationships between particle morphology, size, particle size distribution (raw or agglomerated) or coating (surface treatment) and effects.
Notter et al. (2014) presents a meta-analysis of published EC50 values for ionic silver and nanosilver. The authors demonstrate that almost 94% of acute toxicity values assessed for freshwater, seawater and terrestrial systems using algae, annelid, arthropoda, bacteria, crustacea, fish, nematoda, plant, protozoa and rotatoria show that the nanoform of silver is less toxic than the dissolved metal (when normalised for total metal concentration).
In addition, a specific ecotoxicity testing programme designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms was undertaken following the silver substance evaluation. This demonstrated that the nanoform of silver is less toxic than ionic silver (based on EC10 and EC50 values for total, ‘conventional’ dissolved (<0.45μm) and ‘truly’ dissolved (<3kDa) silver). Therefore, taking the full body of evidence into account, the read-across use of toxicity values from ionic to nanosilver as a ‘worst case’ approach is justified and scientifically defensible for environmental endpoints. The Substance Evaluation Conclusion document for silver agreed with this conclusion for the nanosilver forms covered in the REACH dossier (RIVM 2018).

Toxicity to soil macro-organisms
There are three studies reporting the long-term toxicity of various sizes of nanoparticles and coating types to terrestrial invertebrates included in the REACH dossier as Endpoint Study Records. These comparative long-term (28d) studies for earthworms all report effects thresholds (EC10) for nanosilver that are less sensitive or of comparable sensitivity to those for ionic silver. There is insufficient long-term data for terrestrial invertebrates to conclude on the influence of particle size or particle coating on terrestrial ecotoxicity. Together with the theoretical basis for read-across based on the free-ion, this supports the use of ionic silver as the ‘worst case’ basis to read across properties to nanosilver. A summary of these supporting studies is available under Section 4.3.1 of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IUCLID Section 13).


For further information and data matrix see 'CSR Annex 9 - Read Across Justification Nanosilver ENV_SUMMARY_200706' attached in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
226 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
element
Basis for effect:
mortality
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
39 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
element
Basis for effect:
growth
Remarks:
dry and wet weight
Duration:
56 d
Dose descriptor:
NOEC
Effect conc.:
11.2 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
element
Basis for effect:
reproduction
Remarks:
number of juveniles produced
Duration:
56 d
Dose descriptor:
NOEC
Effect conc.:
39 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
element
Basis for effect:
reproduction
Remarks:
mean number of cocoons
Duration:
56 d
Dose descriptor:
EC10
Effect conc.:
15.05 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
element
Basis for effect:
reproduction
Remarks:
number of juveniles produced
Details on results:
Avoidance was noted in the higher silver treatments (>50 mg/kg) up to day 12.
Results with reference substance (positive control):
The 96hr LC50 fell within the 95% historical control limits. Therefore, the response of the organisms was within the historical range for this laboratory.
Reported statistics and error estimates:
Hypothesis testing of the NOEC was determined using Toxstat version 3.5.
Validity criteria fulfilled:
yes
Remarks:
Survival and reproduction in controls was within acceptable levels
Conclusions:
The most sensitive endpoint for this test was the number of juveniles produced, with a 56 day NOEC of 11.2 mg Ag/kg dw and an EC10 of 15.05 mg Ag/kg dw.
Executive summary:

The chronic toxicity of silver nitrate to the earthworm Eisenia fetida was tested in an OECD 222 test. The test was conducted as a static exposure with a single soil type. Eight test concentrations and a control were included, and the results are expressed based on the mean measured total silver concentrations at the start and end of the test. The survival and growth of the adult worms was studied for the first 28 days, and reproduction endpoints (number of juveniles and number of cocoons) was studied after 56 days. No observed effect concentrations (NOEC) were determined for each biological endpoint. The most sensitive endpoint for this test was the number of juveniles produced, with a 56 day NOEC of 11.2 mg Ag/kg dw and an EC10 of 15.05 mg Ag/kg dw.

Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE READ-ACROSS APPROACH (ENDPOINT LEVEL)
The REACH registration of silver (powder and massive forms of zero-valent, elemental, silver) is underpinned, in common with other metals, by a read-across (or analogue) approach from the properties of the free ion. This principle of read-across from the free ion has been extended to also include nanosilver.
The scientific validity of read-across from the hazard properties of ionic silver (source) to nanosilver (target) under REACH is underpinned by both theoretical and empirical considerations.
The theoretical basis for the use of ionic silver data as the foundation of the risk assessment of nanosilver is based on the premise that the free metal ion (Me+) is the most toxic metal form/species (Starodub et al. 1987). This consideration was implicit in the development of the Free Ion Activity Model [FIAM] (Morel 1983, Paquin et al. 2002, Campbell 1985, Brown and Markich 2000) and, more recently, the Biotic Ligand Model [BLM] (Paquin et al 2002, Niyogi and Wood 2004) that has underpinned the risk assessment of several metals (e.g. Cu, Ni, Zn) under the Existing Substance Regulations and REACH; and most recently the development of the Environmental Quality Standard (EQS) for nickel and nickel substances under the Water Framework Directive (WFD). When considered on an equal mass basis ionic silver would therefore be expected to have greater toxicity than nanosilver simply on the basis that silver ions are released over time from the surface of particles (via oxidative dissolution). As the properties of nanosilver are read-across directly from ionic silver (not just to the fraction of silver ions released from nanosilver), this read-across is also expected to introduce considerable precaution into the hazard component of the risk assessment of nanosilver as all nanosilver, irrespective of coating, morphology or particle size distribution is assumed to behave similarly to the free ion.
This theoretical consideration has been tested by conducting a comprehensive review of the available scientific literature for nanosilver, with particular emphasis on the comparative effects on REACH relevant biotic systems (REACH information requirement) of ionic silver and nanosilver. This review is described for each endpoint in subsequent sections of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IULCID Section 13) and is summarised below. Furthermore, this theoretical consideration was confirmed by a specific ecotoxicity testing programme undertaken by the EPMF following the silver substance evaluation and designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms.

2. READ-ACROSS APPROACH JUSTIFICATION (ENDPOINT LEVEL)
In terms of ecotoxicity, nanosilver on an equal mass basis has been found to be significantly less toxic than ionic silver for the majority of REACH endpoints and of equivalent toxicity for some others. None of the empirical information available suggests that nanosilver is consistently more hazardous than ionic silver on an equivalent mass basis, or that “nano-specific” effects that would prejudice the validity of read across from ionic silver to nanosilver occur. In addition, with very limited exceptions which are described further in the report ‘Nanosilver: read-across justification for environmental information requirements’, none of the available data suggested consistent relationships between particle morphology, size, particle size distribution (raw or agglomerated) or coating (surface treatment) and effects.
Notter et al. (2014) presents a meta-analysis of published EC50 values for ionic silver and nanosilver. The authors demonstrate that almost 94% of acute toxicity values assessed for freshwater, seawater and terrestrial systems using algae, annelid, arthropoda, bacteria, crustacea, fish, nematoda, plant, protozoa and rotatoria show that the nanoform of silver is less toxic than the dissolved metal (when normalised for total metal concentration).
In addition, a specific ecotoxicity testing programme designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms was undertaken following the silver substance evaluation. This demonstrated that the nanoform of silver is less toxic than ionic silver (based on EC10 and EC50 values for total, ‘conventional’ dissolved (<0.45μm) and ‘truly’ dissolved (<3kDa) silver). Therefore, taking the full body of evidence into account, the read-across use of toxicity values from ionic to nanosilver as a ‘worst case’ approach is justified and scientifically defensible for environmental endpoints. The Substance Evaluation Conclusion document for silver agreed with this conclusion for the nanosilver forms covered in the REACH dossier (RIVM 2018).

Toxicity to soil macro-organisms
There are three studies reporting the long-term toxicity of various sizes of nanoparticles and coating types to terrestrial invertebrates included in the REACH dossier as Endpoint Study Records. These comparative long-term (28d) studies for earthworms all report effects thresholds (EC10) for nanosilver that are less sensitive or of comparable sensitivity to those for ionic silver. There is insufficient long-term data for terrestrial invertebrates to conclude on the influence of particle size or particle coating on terrestrial ecotoxicity. Together with the theoretical basis for read-across based on the free-ion, this supports the use of ionic silver as the ‘worst case’ basis to read across properties to nanosilver. A summary of these supporting studies is available under Section 4.3.1 of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IUCLID Section 13).



For further information and data matrix see 'CSR Annex 9 - Read Across Justification Nanosilver ENV_SUMMARY_200706' attached in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
8.38 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: Silver
Basis for effect:
reproduction
Remarks on result:
other: Silver nitrate. Standard deviation: ± 1.26 mg/kg
Details on results:
Silver nitrate led to a concentration-dependent decrease in the number of cocoons produced per earthworm. A significant decrease in cocoon production was observed at 94.12 ± 5.56 mg/kg silver nitrate, an effect not observed at similar concentration treatments of silver nanoparticles. When compared to the controls, the rate of cocoon hatching was not singificantly affected when worms were exposed to silver nitrate.
For growth and mortality, no-concentration dependent effects were observed at up to 94.12 mg/kg, though a non-significant decrease in growth was observed. The silver nitrate treatments did not induce significant mortality but at the highest concentration tested did show some reproductive toxicity.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
The data were log transformed and Shapiro-Wilk's test was used to test normality, with Levene's test used to test homogeneity of variance. Where data were normal and homogeneous, ANOVA was used to determine significant differences between treatment and controls in growth, mortality and reproduction. Duncan's Multiple Range test was used for post-hoc mulitple comparisons for ANOVA. Wilcoxon Rank-Sum test was used for non-normal data.
Validity criteria fulfilled:
not specified
Remarks:
Insufficient data to determine whether validity criteria were met
Conclusions:
The 28 day reproduction NOEC for silver nitrate to earthworms is 8.38 mg/kg dw.
Executive summary:

The study is a guideline study, published in peer reviewed literature and considered suitable for use as a supporting study for this endpoint. The 28 day reproduction NOEC for silver nitrate to earthworms is 8.38 mg/kg dw.

Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE READ-ACROSS APPROACH (ENDPOINT LEVEL)
The REACH registration of silver (powder and massive forms of zero-valent, elemental, silver) is underpinned, in common with other metals, by a read-across (or analogue) approach from the properties of the free ion. This principle of read-across from the free ion has been extended to also include nanosilver.
The scientific validity of read-across from the hazard properties of ionic silver (source) to nanosilver (target) under REACH is underpinned by both theoretical and empirical considerations.
The theoretical basis for the use of ionic silver data as the foundation of the risk assessment of nanosilver is based on the premise that the free metal ion (Me+) is the most toxic metal form/species (Starodub et al. 1987). This consideration was implicit in the development of the Free Ion Activity Model [FIAM] (Morel 1983, Paquin et al. 2002, Campbell 1985, Brown and Markich 2000) and, more recently, the Biotic Ligand Model [BLM] (Paquin et al 2002, Niyogi and Wood 2004) that has underpinned the risk assessment of several metals (e.g. Cu, Ni, Zn) under the Existing Substance Regulations and REACH; and most recently the development of the Environmental Quality Standard (EQS) for nickel and nickel substances under the Water Framework Directive (WFD). When considered on an equal mass basis ionic silver would therefore be expected to have greater toxicity than nanosilver simply on the basis that silver ions are released over time from the surface of particles (via oxidative dissolution). As the properties of nanosilver are read-across directly from ionic silver (not just to the fraction of silver ions released from nanosilver), this read-across is also expected to introduce considerable precaution into the hazard component of the risk assessment of nanosilver as all nanosilver, irrespective of coating, morphology or particle size distribution is assumed to behave similarly to the free ion.
This theoretical consideration has been tested by conducting a comprehensive review of the available scientific literature for nanosilver, with particular emphasis on the comparative effects on REACH relevant biotic systems (REACH information requirement) of ionic silver and nanosilver. This review is described for each endpoint in subsequent sections of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IULCID Section 13) and is summarised below. Furthermore, this theoretical consideration was confirmed by a specific ecotoxicity testing programme undertaken by the EPMF following the silver substance evaluation and designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms.

2. READ-ACROSS APPROACH JUSTIFICATION (ENDPOINT LEVEL)
In terms of ecotoxicity, nanosilver on an equal mass basis has been found to be significantly less toxic than ionic silver for the majority of REACH endpoints and of equivalent toxicity for some others. None of the empirical information available suggests that nanosilver is consistently more hazardous than ionic silver on an equivalent mass basis, or that “nano-specific” effects that would prejudice the validity of read across from ionic silver to nanosilver occur. In addition, with very limited exceptions which are described further in the report ‘Nanosilver: read-across justification for environmental information requirements’, none of the available data suggested consistent relationships between particle morphology, size, particle size distribution (raw or agglomerated) or coating (surface treatment) and effects.
Notter et al. (2014) presents a meta-analysis of published EC50 values for ionic silver and nanosilver. The authors demonstrate that almost 94% of acute toxicity values assessed for freshwater, seawater and terrestrial systems using algae, annelid, arthropoda, bacteria, crustacea, fish, nematoda, plant, protozoa and rotatoria show that the nanoform of silver is less toxic than the dissolved metal (when normalised for total metal concentration).
In addition, a specific ecotoxicity testing programme designed to compare the effects of the smallest nanosilver form registered under REACH (‘Nano 8.1’ or ‘Silberpulver Typ 300-30’) and silver nitrate to algae, Daphnia (long-term) and soil microorganisms was undertaken following the silver substance evaluation. This demonstrated that the nanoform of silver is less toxic than ionic silver (based on EC10 and EC50 values for total, ‘conventional’ dissolved (<0.45μm) and ‘truly’ dissolved (<3kDa) silver). Therefore, taking the full body of evidence into account, the read-across use of toxicity values from ionic to nanosilver as a ‘worst case’ approach is justified and scientifically defensible for environmental endpoints. The Substance Evaluation Conclusion document for silver agreed with this conclusion for the nanosilver forms covered in the REACH dossier (RIVM 2018).

Toxicity to soil macro-organisms
There are three studies reporting the long-term toxicity of various sizes of nanoparticles and coating types to terrestrial invertebrates included in the REACH dossier as Endpoint Study Records. These comparative long-term (28d) studies for earthworms all report effects thresholds (EC10) for nanosilver that are less sensitive or of comparable sensitivity to those for ionic silver. There is insufficient long-term data for terrestrial invertebrates to conclude on the influence of particle size or particle coating on terrestrial ecotoxicity. Together with the theoretical basis for read-across based on the free-ion, this supports the use of ionic silver as the ‘worst case’ basis to read across properties to nanosilver. A summary of these supporting studies is available under Section 4.3.1 of the report ‘Nanosilver: read-across justification for environmental information requirements’ (attached in IUCLID Section 13).


For further information and data matrix see 'CSR Annex 9 - Read Across Justification Nanosilver ENV_SUMMARY_200706' attached in IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
8.38 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: Silver
Basis for effect:
reproduction
Remarks:
Cocoons and worms
Remarks on result:
other: Soil: Artifical. Standard error: ± 1.26 mg/kg soil dw.
Details on results:
Earthworms in artificial soil exposed to silver nitrate showed no significant concentration-dependent decrease in growth or survival but a significant decrease in the number of cocoons per worm was observed at concentrations of 94.12 g/kg. In the artifical soil, the hatching rate of cocoons showed no significiant difference at any concentration. In all the treatment groups and the control, no juveniles survived to be counted.
In YSL, earthworms exposed to 7.41 ± 1.19 mg/kg ionic silver showed a signficiant decrease in growth and exposures of 7.41 mg/kg soil dw caused a significant decreases in the hatching sucess and the number of juveniles. No significant decrease was observed on the number of cocoons produced per earthworm.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
The data were log transformed and Shapiro-Wilk's test was used to test normality, with Levene's test used to test homogeneity of variance. Where data were normal and homogeneous, ANOVA was used to determine significant differences between treatment and controls in growth, mortality and reproduction. Duncan's Multiple Range test was used for post-hoc mulitple comparisons for ANOVA. Wilcoxon Rank-Sum test was used for non-normal data.
Validity criteria fulfilled:
not specified
Remarks:
Insufficient data to determine whether validity criteria were met
Conclusions:
The 28 day reproduction (cocoons and worms) NOEC for silver nitrate to earthworms in artificial soil is 8.38 mg Ag/kg dw .
Executive summary:

The study is a guideline study, published in peer reviewed literature and considered suitable for use as a supporting study for this endpoint. The 28 day reproduction (cocoons and worms) NOEC for silver nitrate to earthworms in artificial soil is 8.38 mg Ag/kg dw .

Description of key information

Key value for chemical safety assessment

Additional information

Summary of available data for uncoated and coated nanosilver

After quality assessment there are three reliable studies reporting the long-term toxicity of nanosilver to terrestrial invertebrates. Two of the studies are by Shoults-Wilson et al. (2011a/b) and report the results of a series of 28 day toxicity tests with the earthworm Eisenia fetida in synthetic soil using PVP and oleic acid coated nanosilver. The third study is reported by Schlich et al. (2013), who report the results of a series of 28 day earthworm reproduction tests with Eisenia andrei exposed to nanosilver and ionic silver (as silver nitrate).

Shoults-Wilson et al. (2011a) report a 28-day NOEC for oleic acid coated spherical nanosilver particles (~50 nm diameter) of 81.62 mg/kg based on reproduction (cocoon production). Shoults-Wilson et al. (2011b) report 28 day reproduction (cocoon production) NOECs for ~40 and ~60 nm diameter PVP coated nanosilver particles of 84.15 and 79.45 mg/kg, respectively. No difference in toxicity between PVP and oleic acid coating spherical nanoparticles was observed in either study. Both studies report a comparative exposure with ionic silver (silver nitrate), resulting in a reproduction NOEC of 8.38 mg/kg, which is approximately a factor of 10 more sensitive than that observed for the silver nanomaterials.

Schlich et al. (2013) report data on earthworm reproduction (number of juveniles) from four 28 day tests. NOEC values for reproduction, with the exception of a single study with silver nitrate, are all reported as less than the lowest concentration tested, i.e. statistically significant effects were observed at the lowest concentration tested. However, using the data presented in the paper, EC10 values of 23.87 and 14.68 mg/kg dry weight can be calculated for uncoated nanosilver (15 nm) and EC10 values of 21.03 and 15.39 mg/kg dry weight can be calculated for ionic silver. These data suggest that nano and ionic forms of silver are of similar toxicity to Eisenia andrei. However, the absence of exposures that did not affect earthworm reproduction suggests that there are some limitations with the experimental design and that the results from this test should be interpreted with caution.

There is insufficient long-term data for terrestrial invertebrates to conclude on the influence of particle size or particle coating on terrestrial ecotoxicity.