Silver

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-term

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Substance considered to fall within the scope of the read-across 'Silver metal: Justification of a read-across approach for environmental information requirements' (document attached in IUCLID section 13).

Reason / purpose for cross-reference:

read-across source

Duration:

10 d

Dose descriptor:

LC50

Effect conc.:

0.084 other: g/kg

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: Bond lake sediment

Duration:

10 d

Dose descriptor:

LC50

Effect conc.:

2.98 other: g/kg

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: West Bearskin lake sediment

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

0.012 other: g/kg

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: Bond lake sediment

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

2.15 other: g/kg

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: West Bearskin lake sediment.

Conclusions:

The 10-day LC50 values were 0.084 g Ag/kg and 2.98 g Ag/kg for the two sediment types. The 10-day NOECs were 0.012 g Ag/kg and 2.15 g Ag/kg for the two sediment types, based on growth.

Executive summary:

The GLP status of this study is not known. It follows an adapted version of a standard guideline. The methods are well-described and it is considered reliable and suitable for use for this endpoint. The most sendistive

Description of key information

Read-across from the dissolved silver ion is also applied to fulfil information requirements for silver and silver-based (coated) nanomaterials. Supporting information for this read-across is included in endpoint summaries and in the appended summary/justification document.

Additional information

Summary of available data for uncoated and coated nanosilver

There are two studies reporting the effects of nanosilver exposure on sediment dwelling species (Nair et al. 2011, Hund-Rinke and Klawonn 2013). Nair et al. (2011) exposed 4^thinstar larvae of Chironomus riparius to nanosilver via the water column in a sediment/ water system and monitored pupation over a 25 day period. The study reports a LOEC of 200 µg/L for nanosilver in the water column (40 – 70 nm uncoated particles) from which a NOEC of 100 µg/L can be derived (where a LOEC is associated with effects >10% but <20% ECHA guidance [ECHA 2008] allows a NOEC to be calculated as LOEC/2). No measured concentrations of silver in sediments were reported.

Hund-Rinke and Klawonn (2013) undertook a standard 28 day OECD 219 sediment/water chironomid toxicity test using spiked overlying water. The study used a static exposure regime and undertook a single spike of overlying water with various concentrations of NM-300K nanosilver (uncoated particles with particle size of 15 nm) and measured chironomid survival, growth and development from 1^stinstar larvae to emergence. Nanosilver was observed to rapidly partition to sediments. The study reported effects on development rate and on the total number of observed midges. The most sensitive EC10 from the study was 925 µg/L for effects on the development rate of male and female midges.

Neither of the studies undertook a comparative exposure assessment of the relative toxicity of ionic and nanosilver in their test systems. The critical data for the sediment compartment in the CSR is a NOEC of 12 mg/kg silver from a 10 day exposure with the amphipod Hyalella azteca (Call et al. 1999). However, this value is not directly comparable with the effects thresholds derived from either the Nair et al. (2011) and Hund-Rinke and Klawonn (2013) studies as these exposures were via the water column rather than directly via the sediment phase. As an alternative, an EC10 for ionic silver from the REACH CSR of 14.43 µg/L, based on a 10 day water-only growth study using Chironomus tentans reported by Call et al. (1999), can be used to compare the relative toxicity of nanosilver and ionic silver in sediment dwelling species. Despite the Nair et al. (2011) and Hund-Rinke and Klawonn (2013) studies, both using a significantly longer exposure duration than Call et al. (1999), both studies report effects thresholds for nanosilver at least an order of magnitude less sensitive than for ionic silver.

As both Nair et al. (2011) and Hund-Rinke and Klawonn (2013) use a sediment/water test system, whilst Call et al. (1999) used a water only exposure there could be differences in the partitioning behaviour of silver between the two studies that confounds this simple interpretation of the two tests. Notwithstanding the limitations of the available information, the potential for adverse effects on sediment dwelling species from nanosilver exposure appears to be less than for ionic silver.