Silver nitrate

Bioaccumulation: terrestrial

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation: terrestrial

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP, non-guideline study, available as a published journal article. Some limitations in design and/or reporting.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Coutris et al. 2012 used neutron activated soluble silver to assess the uptake, excretion and bio-distribution of silver in the earthworm Eisenia fetida exposed in standard OECD artificial soil (pH 5.95) amended with spiked, air dried, horse manure.

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Radiolabelling:

yes

Details on sampling:

No data reported

Vehicle:

not specified

Details on preparation and application of test substrate:

Artificial OECD soil (10% dw sphagnum peat, 20% dw kaolinite clay, 70% dw quartz sand 0.09–0.5 mm, 0.4% dw CaCO3, 50 g dw soil corresponding to 68 g moist soil per worm).

Test organisms (species):

Eisenia fetida

Details on test organisms:

Mature (clitellate, two-months old) specimens of Eisenia fetida (Savigny) were taken from a synchronized culture and weighed individually (average worm weight: 394±76 mg). The worms were acclimatized for a minimum of 10 days in artificial OECD soil.

Total exposure / uptake duration:

28 d

Total depuration duration:

8 wk

Test temperature:

No data reported

pH:

Soil pH measured in 0.01 M CaCl2 was 5.95.

TOC:

No data reported

Moisture:

No data reported

Details on test conditions:

Earthworms were exposed for 28 days to Ag ions via their diet (air-dried horse manure sieved to <0.63 mm and remoistened to 67% water content, pH 7.3 measured in 0.01 M CaCl2), supplied once a week on the soil surface (0.5 g dw manure/worm). The horse manure was spiked with the radiolabeled substances by dry mixing the ENPs into the dry manure and then moistening with water. The ionic forms were added as solutions at the same time as the water. Water was added to the manure 24 hours prior to feeding and the manure was mixed mechanically using a spatula; homogeneity was checked by counting sub-samples using a Ge-detector.

The natural concentrations of silver in the horse manure analyzed by ICP-MS were less than 0.07mg/g ww. In the OECD soil, natural silver concentration was below detection limit. At the end of the exposure period, earthworms were transferred to clean terraria for 48 hours in order to empty their gut. They were then transferred again to new clean terraria for a depuration period of two months for silver treatments, renewing soil each month and providing 0.5 g dw clean horse manure per worm per week.

Nominal and measured concentrations:

In all treatments we aimed to use concentrations that would be below those exerting acute toxic effects. The concentrations of added stable silver in the horse manure (wet, as fed to the worms) was 0.55±0.15mg/g Ag ions.

Type:

BCF

Value:

0.62 dimensionless

Basis:

whole body w.w.

Time of plateau:

30 d

Calculation basis:

kinetic

Remarks on result:

other: 30 day BAF bioavailable value for ionic silver

Kinetic parameters:

The time course of accumulation during the exposure period had high initial accumulation which leveled off and approached a plateau after 28 days.

Metabolites:

Not applicable

Details on results:

- Control: During the five months duration of the experiment, no worms died in either the treated or the control terraria. Their average mass increased from 394 ± 76 mg ww to 566±144 mg ww and cocoons and juveniles were found in all treatments during the whole duration of the experiment.
- Results: At the end of the exposure period (day 28), but prior to emptying their gut content, worms had body concentrations (mean±SEM, n=30) corresponding to 5.1±0.5% and 11.0±0.3% of the concentration in the food for Ag NPs and Ag ions. After emptying their gut content for 48 hours, the corresponding value was 2.3±0.1%, for Ag ions. 80% of Ag ions were excreted within 48 hours and 97% during the two-month depuration period. At this time the remaining 110m Ag concentration in individual worms was close to the detection limit and the depuration study was terminated. Further localization of Ag in worms’ organs was not possible due to extremely low amounts of Ag in worms.
- Conclusion: 30 day BAF bioavailable value of 0.62 ± 0.11 was reported for ionic silver.

Reported statistics:

The counting uncertainties were calculated from the counting uncertainty of individual activity measurements using the square root of sum of squares. Evaluation of statistical differences between ionic and particulate silver was performed by a Student’st-test.

Validity criteria fulfilled:

not applicable

Conclusions:

30 day BAF bioavailable value of 0.62 ± 0.11 was reported for ionic silver.

Executive summary:

Coutris et al. 2012 used neutron activated soluble silver (silver nitrate) to asses the uptake, excretion and bio-distribution of silver in the earthworm Eisenia fetida exposed 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 BAF_bioavailablevalue of 0.62 ± 0.11 was reported.

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

BCF (terrestrial species):

0.62 dimensionless

Additional information

Coutris et al. (2012) used neutron activated soluble silver (silver nitrate) to assess the uptake, excretion and bio-distribution of silver in the earthworm Eisenia fetida exposed 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 BAF_bioavailable value of 0.62 ± 0.11 was reported.