Registration Dossier

Diss Factsheets

Ecotoxicological information

Ecotoxicological Summary

Currently viewing:

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
0.04 µg/L
Assessment factor:
3
Extrapolation method:
sensitivity distribution

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
0.86 µg/L
Assessment factor:
10
Extrapolation method:
assessment factor

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
0.025 mg/L
Assessment factor:
1
Extrapolation method:
assessment factor

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
438.13 mg/kg sediment dw
Assessment factor:
10
Extrapolation method:
assessment factor

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
438.13 mg/kg sediment dw
Assessment factor:
10
Extrapolation method:
assessment factor

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
1.41 mg/kg soil dw
Assessment factor:
3
Extrapolation method:
sensitivity distribution

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

See CSR Annex 4 - PNEC Summary Report

Conclusion on classification

Acute and chronic aquatic toxicity data are available for a range of different freshwater and marine species. For silver and silver compounds, the acute ecotoxicity reference value (ERV) is 0.22 µg Ag/L and the chronic ERV is 0.1 µg Ag/L.

In line with the risk assessment/classification approach adopted for other metals and inorganic metal compounds (ECHA 2013), ecotoxicity data are reported in terms of the concentration of dissolved silver ions from soluble inorganic silver species. Predominantly, these are studies that used silver nitrate (AgNO3) as the source of dissolved silver ions. Silver nitrate is considered to be the form of silver with the greatest toxicity as it dissociates rapidly and completely in aqueous solution. Where data for silver nitrate was not available, data derived from other inorganic salts (e.g. silver chloride) were used, but only after the exposure conditions were determined to be acceptable (e.g. testing was conducted within the limits of solubility and the Ag+ ion was likely to be the dominant dissolved species).

A complete base set of acute ecotoxicity studies is available for soluble inorganic silver species, comprising numerous studies for fish, invertebrates and algae. The lowest reliable acute value is an EC50 of 0.22 µg Ag/L for the invertebrateDaphnia magna(Bianchini et al. 2002).

A complete chronic data set is also available for soluble inorganic silver species, with chronic ecotoxicity data available for various species of fish, invertebrates and algae. The lowest reliable chronic value is an EC10 of 0.1 µg Ag/L for the algaePseudokirchneriella subcapitata(Fraunhofer 2017). Additional chronic toxicity data of similar sensitivity are also available for thethe blue-green algae Nostoc muscorum (Rai et al. 1990),Brown TroutSalmo trutta(217 day EC10 of 0.19 µg Ag/L) andOncorhynchus mykiss(196 day EC10 of 0.17 µg Ag/L) obtained from Davies et al. (1998).

Based on current guidance (ECHA 2013), soluble silver is classified as R50/53 under the DSD, with specific concentration limits of Cn ≥0.025% for R50-53, ≥0.0025% Cn <0.025% for R51-53, and ≥0.00025% Cn <0.0025% for R52-53. Soluble silver is also classified as Acute 1 and Chronic 1 under the CLP regulations and subject to an acute M factor of 1000 and a chronic M factor of 100.

Uncoated and coated nanomaterials (as per EU definition – median particle size <100 nm)

A precautionary classification for silver and silver-based (coated) nanomaterials has been read across from data for soluble silver (see below). Similarly, appropriate M factors have been based on read across from soluble silver.

Classification

The classification strategy for poorly soluble silver substances has been based on ECHA guidance (ECHA 2013). This guidance describes how to determine the classification and appropriate M factors for poorly soluble substances, such as elemental silver powder and massive silver, from acute and chronic ERV and the results of T/D tests (Annex IV: Metals and Inorganic Metal Compounds). Acute and chronic classifications have been undertaken individually.

Uncoated and coated nanomaterials (as per EU definition – median particle size <100 nm)

The T/D-data generated for nanosilver for the silver substance evaluation under REACH should not be used for classification purposes. On specific request of the Evaluating MS this T/D study was performed in non-standard modified daphnia and algae media (with chloride salts replaced by nitrate salts to maximise the concentration of ionic Ag). These conditions are deviating from the standard medium described in OECD Test Guideline 29. The OECD 29 Test Guideline was developed for hazard classification purposes, and therefore any deviation from the guideline (like changes in the medium composition that may affect the solubility and bioavailability of the test compound) makes the results not useable for hazard assessment.

In absence of reliable T/D data (generated according to OECD Testing Guideline 29) for nanosilver, the environmental classification of uncoated and coated nanomaterials has therefore been directly read across from soluble forms of silver. Silver and silver-based nanomaterials would therefore be classified as per soluble silver substances: Acute and Chronic Category 1.

Appropriate M factors have also been read across from soluble forms of silver. This read-across results in acute and chronic M factors of 1000 and 100, respectively, for uncoated and coated nanomaterials.

As the weight of evidence available suggests that the ecotoxicity of uncoated and coated nanomaterials is lower than soluble silver on an equivalent mass basis (see read-across matrix for environmental endpoints), read across from soluble silver in this case is expected to result in a precautionary classification and M-factors for nanosilver.

Equally, as the dissolution rates of uncoated and coated nanomaterials are expected to be variable dependent on morphology, particle size, particle size distribution and coating, this approach encompasses the range of likely properties of nano silver and is consistent with the read across rationale applied to uncoated and coated nanomaterials for environmental hazard endpoints.

For the purposes of this read-across, silver-based (coated) nanomaterials are considered to be those that are primarily based on elemental silver and fulfil the criteria of the Commission Recommendation for the definition of nanomaterials, but which also comprise a surface functionalisation/coating/capping. The scope of the read-across from soluble silver to elemental silver and elemental silver-based (coated) nanomaterials for classification is identical to the scope of the environmental assessment of silver and silver-based (coated) nanomaterials in the REACH chemical safety assessment (CSA), i.e. the read-across is only considered to be applicable where applied to elemental silver nanomaterials or elemental silver-based nanomaterials with additional surface functionalisation/coating/capping that is demonstrated to be non-toxic, biodegradable, “passive” and applied primarily to increase the stability of nanomaterial dispersions in aqueous or non-aqueous solutions (i.e. to prevent aggregation or agglomeration) through steric, electrostatic or comparable mechanism. Surface functionalistion/coating/capping that are specifically designed to interact with biological receptors or which have hazardous properties in their own right (e.g. meet the criteria for SVHC) would not be compatible with this read-across approach for classification. Equally, multi-metal nanomaterials incorporating elemental silver are outside of the scope of this read-across.

References cited

ECHA (2013) Guidance on the Application of the CLP Criteria. Guidance to Regulation (EC) No 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures. Version 4.0, November 2013.