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EC number: 231-131-3
CAS number: 7440-22-4
Table1: Results from analyses of the selected study soils for pH,
organic carbon, cation exchange capacity, particle size distribution and
total silver concentration.
Cation exchange capacity
Particle size distribution (%)
Total Silver (mg/kg)
* note that particle size distribution
for Port Kenny is equal to 37.2% due to the high concentration of CaCO3that
is present in this soil (60%)
The toxicity of silver to soil microorganisms was investigated
using a soil nitrogen (N) transformation test (OECD guideline 216, 2000)
for six study soils. Two test endpoints were calculated from the
results: total NO3 production and potential nitrification rate (PNR).
The 28-day EC10 values for NO3 production ranged from 0.65 (Bordeaux) to
371 mg Ag/kg (Millicent) and for PNR were between 1.2 (Bordeaux) and 488
mg Ag/kg (Millicent) in unleached soils. The toxicity of silver to the
soil nitrification process was primarily controlled by soil pH and OC.
chronic toxicity of silver nitrate to indiginous soil microorganisms was
tested in an OECD 216 test. The test was conducted as a static exposure
with a single soil type. Six 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. Alfalfa was
added to half the replicates as an organic substrate. The rate of
nitrogen transformation was studied for 28 days. The 28 day NOEC
was 0.13 mg Ag/kg dw and the EC10 was 0.30 mg Ag/kg dw.
Read across from ionic silver
Plus supporting data from a soil nitrogen (N) transformation test
comparing the effects of the smallest nanosilver form registered under
REACH previously (‘Nano 8.1’) and ionic silver (silver nitrate) in 3
natural soils, demonstrating nanosilver is equally toxic than ionic
silver in 1 soil and less toxic than ionic silver in 2 soils (based on
EC10 and EC50 values)
Plus supporting published data from 1 study included in the REACH
dossier as Endpoint Study Record, reporting a NOEC for nanosilver and
silver ions in loam soil of >3 mg/L
Summary of available data for uncoated
and coated nanosilver
Two reliable studies investigating the
effects of nanosilver on soil microorganisms are available (Calder et
al. 2012, and Smolders and Willaert, 2017)).
Calder et al. (2012) evaluated the toxicity
of 10 nm spherical silver nanoparticles (1 and 3 mg/L) to Pseudomonas
chlororaphis O6 (a beneficial soil bacterium) in sand and soil
matrices (loam soil). In sand, both concentrations of nanosilver
resulted in a loss of bacterial viability whereas in loam soil, no
cell death was observed. The addition of clays (30% v/v kaolinite or
bentonite) to sand did not protect the bacterium when challenged with
Ag NPs. However, viability of the bacterium was maintained when sand
was mixed with soil pore water or, to a lesser extent, humic acid.
Despite being considered a reliable study the experimental design
employed should be considered to represent rather artificial
conditions that may not reflect the behaviour of nanosilver materials
in conventional soils or the response of natural microbial
assemblages. Specifically, this relates to the fact that the effects
of nanosilver in soil matrices were tested in aqueous suspension and
that only a single microbial species was present. The study reports a
NOEC for nanosilver and silver ions in loam soil of >3 mg/L (note that
conventionally the results of terrestrial ecotoxicity tests are
expressed as units of soil mass e. g. mg/kg (dry weight).
The effects of nanosilver and silver
nitrate to soil microorganisms were compared by Smolders and Willaert
(2017), using a soil nitrogen (N) transformation test (OECD guideline
216, 2000). The toxicity of nanosilver and silver nitrate were
evaluated in three natural soils (Rots, Poelkapelle and Lufa 2.2),
based on two test endpoints: potential nitrification rate (PNR) and
substrate induced nitrification (SIN).Soil samples from
three different arable soils (Rots, Poelkapelle and Lufa 2.2) were
collected from the plough layer (0-20 cm). The soils were selected to
have a pH between 4.3 and 7.3, %OC between 1.1 and 6.8% and CEC
between 9.7 and 33.9 cmolc/kg.The nanosilver material used
was a powder in aqueous suspension with the following particle size
distribution: D25 = 7 nm, D50 = 8 nm, D75 = 9 nm (see section 4.5 of
IUCLID), and contained 37% silver. Based on 0-14 day PNR, the EC10
values for nanosilver (as measured total silver) ranged from 3.8 to
29mg Ag/kg. Based on 28 day SIN,the EC10 values for nanosilver
(measured total silver) ranged from 35 to 132mg Ag/kg. Corresponding
0-14 day PNR EC10 values for silver nitrate (measured total silver)
ranged from 3.8 to 9.1 mg Ag/kg, and 28 day SIN EC10 values ranged
from 30 to 45 mg Ag/kg. These results inicate that silver toxicity to
soil microorganisms is similar for both ionic silver and nanosilver.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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