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Environmental fate & pathways

Bioaccumulation: terrestrial

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Description of key information

A 30 day BAF bioavailable value of 0.62 ± 0.11 was reported for silver nitrate bioaccumulation in the earthworm Eisenia fetida.

Key value for chemical safety assessment

Additional information

Silver

Coutris et al. (2012) used neutron activated soluble silver (silver nitrate) to assess the uptake, excretion and bio-distribution of silver in the earthwormEisenia fetidaexposed in standard OECD artificial soil (pH 5.95) amended with spiked, air dried, horse manure (0.55 ± 0.15 µg/g dissolved silver). A 30 day BAFbioavailablevalue of 0.62 ± 0.11 was reported.

Summary of available data for uncoated and coated nanosilver

Bioaccumulation in terrestrial invertebrates

Coutris et al. (2012) used neutron activated nanosilver particles (20.2 ± 2.5 nm by TEM) and soluble silver (silver nitrate) to assess the uptake, excretion and bio-distribution of silver in the earthwormEisenia fetidaexposed in standard OECD artificial soil (pH 5.95) amended with spiked, air dried, horse manure (0.55 ± 0.15 µg/g dissolved silver; 0.77 ± 0.15 µg/g nanosilver). 30 day BAFbioavailablevalues of 0.31 ± 0.12 and 0.62 ± 0.11 were reported for nanosilver particles and ionic silver, respectively. Ionic silver was approximately twice as bioavailable as nanosilver. Silver accumulated from soluble salts and nanoparticles was excreted rapidly.

Hunde-Rinke and Klawonn (2013) also measured bioaccumulation of nanosilver (NM-300K, 15 nm particle size) withEisena fetida. Worms were exposed to silver via either soil or feed in a long-term (28 day) chronic toxicity study. No depuration phase was included and measurements were made at 28 days only. Despite these limitations, a bioaccumulation factor (BAF) of 0.52 can be calculated from silver accumulation observed in the lowest test concentration (13.43 mg/kg dry weight) of the soil exposure after 28 days (no adverse effects were observed on survival or reproduction at this nanosilver concentration). It is not clear if steady-state concentration was achieved after this exposure. Exposures to higher concentrations of silver in soil (by factors of up to 13), whilst resulting in toxicity, did not result in broadly greater accumulation of silver. It is unclear if the silver was located in the tissues or the gut of the worm. These results compare favourably to those reported by Coutris et al. (2012). No comparative exposure to ionic silver was conducted.