Silver nitrate

Toxicity to terrestrial arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to terrestrial arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Unpublished guideline study. Some limitations in method and/or reporting but otherwise adequate for assessment.

Principles of method if other than guideline:

Organisms were exposed to silver nitrate concentrations in soil for 14 days and the survival, growth (biomass) and behaviour (avoidance) was recorded.

GLP compliance:

not specified

Application method:

soil

Specific details on test material used for the study:

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

Analytical monitoring:

yes

Details on sampling:

For total Ag analysis, ~100 mg of soil were dried overnight at 50ºC and digested in 2mL in a mixture of, concentrated HCl (J.T. Baker, purity 37%) and HNO3 (J.T. Baker, purity 70%) (4:1, v/v) for 7 hours in an oven (CEM MDS 81-D) at 140ºC.

Vehicle:

no

Details on preparation and application of test substrate:

Lufa 2.2 soil (LUFA-Speyer 2.2, Sp 2121, LUFA Speyer, Speyer, Germany) was used in the toxicity tests. After spiking with a stock solution of AgNO3 (Sigma-Aldrich, 99% purity, CAS 7761-88-8), soils were equilibrated for one day. Non-spiked soils were moistened with Milli-Q water and tested as control soils.

Test organisms (species):

other: Porcellionides pruinosus

Animal group:

Crustacea (soil-dwelling woodlouse)

Details on test organisms:

Specimens of the isopod Porcellionides pruinosus were collected in uncontaminated field in Coimbra (Portugal). The animals were kept in lab conditions (20±2ºC, 16/8h photoperiod) for at least one month before used in the tests. For the toxicity tests, males and non-gravid females adults (>15-25 mg) were used.

Study type:

laboratory study

Limit test:

no

Total exposure duration:

14 d

Post exposure observation period:

None

Test temperature:

20±2°C

pH (if soil or dung study):

pH 5,5
Analysis method: 0.01 M CaCl2

Humidity:

No data available

Photoperiod and lighting:

No data available

Details on test conditions:

- Survival test: Approximately 100 g of soil were added to plastic boxes. In each box, 10 isopods were added and 4 replicates were used for each concentration and control. Number of dead animals was recorded after 14 days.
- Avoidance behavior test: Plastic boxes were divided in two compartments using a removable plastic split. In each compartment, Ag-spiked and unspiked Lufa 2.2 soils were added. The split was removed and 3 isopods were introduced between spiked and unspiked soils, in triplicates for each concentration. After 48 hours, the split was reintroduced and the number of animals in each compartment (spiked or unspiked soil) was counted.
- Feeding inhibition test: The isopods were exposed individually, in 5 replicates for each treatment and a control. The animals were fed with alder leaves ad libitum. After 14 days, biomass change (%) was evaluated.
- Information on soil: 2.09% OC, eCEC = 10 cmolc/kg

Nominal and measured concentrations:

- Survival test: Lufa 2.2 soil was spiked with AgNO3 at 6 nominal concentrations of 0.01, 0.1, 1, 10, 100, and 1000 mg Ag/kg.
- Avoidance behavior test: Lufa 2.2 soil was spiked with AgNO3 at 5 nominal concentrations of 1, 5, 10, 50 and 100 mg Ag/kg.
- Feeding inhibition test: Lufa 2.2 soil was spiked with AgNO3 at 5 nominal concentrations of 12.5, 25, 50, 100, and 200 mg Ag/kg.

Reference substance (positive control):

no

Key result

Duration:

14 d

Dose descriptor:

LC10

Effect conc.:

40.54 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Silver

Basis for effect:

mortality

Remarks on result:

other: 95% CI: 22.85-59.99 mg Ag/kg soil dw

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

391.4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Silver

Basis for effect:

mortality

Remarks on result:

other: 95% confidence intervals: 256-651 mg Ag/kg soil dw

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

68.11 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Silver

Basis for effect:

growth

Remarks:

Biomass

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

252.95 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Silver

Basis for effect:

growth

Remarks:

Biomass

Key result

Duration:

14 d

Dose descriptor:

EC10

Effect conc.:

176.56 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Silver

Basis for effect:

growth

Remarks:

Biomass

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

120.1 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Silver

Basis for effect:

growth

Remarks:

Biomass

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

14.5 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Silver

Basis for effect:

behaviour

Remarks:

Avoidance

Remarks on result:

other: 95% confidence intervals: 9.3-23.9 mg Ag/kg soil dw

Details on results:

The 14 day LC50 for survival was 391.4 mg Ag/kg soil dw (95% confidence intervals: 256-651 mg Ag/kg soil dw) based on nominal concentrations. The 14 day EC50 for biomass was 120.1 mg Ag/kg soil dw based on measured concentrations. The 48 hour EC50 for avoidance was 14.5 mg Ag/kg soil dw (95% confidence intervals: 9.3-23.9 mg Ag/kg soil dw) based on measured concentrations.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

- Survival test: Silver concentrations causing 50% mortality (median lethal concentrations or LC50) of P. pruinosus were calculated by probit analysis.
- Avoidance test: As in the avoidance behavior test, 50% of avoidance is defined as 50% of the animals in the control soil, the calculation of EC50 need to be adapted to the avoidance results (Loureiro et al., 2005). For that, % of avoidance (A) was calculated by the formula: A=(C-T)/N*100 where C is number of animals in control soil, T is number of animals in spiked soil and N is the total number of animals. Median avoidance concentration (AC50) was calculated using Probit regression (% Avoidance versus concentration).
- Biomass change: For biomass change, median effect concentrations (EC50s) were estimated by applying a four parameter logistic model: Y = Ymin+(Ymax-Ymin)/(1+(X/EC50)-b where Ymin is the minimum biomass gain (%); Ymax the maximum biomass gain (%); X the Ag concentration in soil (mg Ag/kg); and b the slope parameter.

Survival of Porcellionides pruinosus

Concentration mg/kg	survival	total observed
control	32	40
0.01	35	40
0.1	37	40
1	35	40
10	33	40
100	25	40
1000	3	40

Concentration mg/kg	N	Dead	Alive
Control	10	2	8
Control	10	2	8
Control	10	2	8
Control	10	2	8
0.01	10	2	8
0.01	10	1	9
0.01	10	0	10
0.01	10	2	8
0.1	10	1	9
0.1	10	1	9
0.1	10	1	9
0.1	10	0	10
1	10	1	9
1	10	1	9
1	10	2	8
1	10	1	9
10	10	2	8
10	10	1	9
10	10	2	8
10	10	2	8
100	10	7	3
100	10	4	6
100	10	2	8
100	10	2	8
1000	10	7	3
1000	10	10	0
1000	10	10	0
1000	10	10	0

Biomass change of Porcellionides pruinosus

concentration (mg/kg)	biomass change	measured concentration	median
0	-1.84	2.8	-0.883
0	0.59	2.8
0	-1.4	2.8
12.5		11.11	-2.41
12.5	4.07	11.11
12.5	-0.2	11.11
12.5	-4.2	11.11
12.5	-9.31	11.11
25	-8.5	24.78	-3.68
25	-4.61	24.78
25	-0.67	24.78
25	-5.24	24.78
25	0.62	24.78
50	-3.14	33.48	-2.762
50	1.58	33.48
50	-5.43	33.48
50	-0.21	33.48
50	-6.61	33.48
100	-1.37	68.11	-4.52
100	-1.85	68.11
100	-10.34	68.11
200	-15.68	252.95	-15.215
200	-13.71	252.95
200	-10.43	252.95
200	-21.04	252.95

Avoidance of contaminated soil

Nominal content (mg/kg)	Measured concentration	Number of organisms	Number in normal soil	Number in contaminated soil	Avoidance %
Control	0	3	3	0	100
Control	0	3	3	0	100
Control	0	3	0	3	-100
1 mg/kg	8.535	3	0	3	-100
1 mg/kg	8.535	3	1	2	-33.3
1 mg/kg	8.535	3	3	0	100
5mg/kg	3.217	3	2	1	33.3
5mg/kg	3.217	3	0	3	-100
5mg/kg	3.217	3	0	3	-100
10mg/kg	18.729	3	3	0	100
10mg/kg	18.729	3	2	1	33.3
10mg/kg	18.729	3	3	0	100
50mg/kg	55.286	3	3	0	100
50mg/kg	55.286	3	3	0	100
50mg/kg	55.286	3	3	0	100
100mg/kg	95.732	3	3	0	100
100mg/kg	95.732	3	3	0	100
100mg/kg	95.732	3	3	0	100

Validity criteria fulfilled:

not specified

Conclusions:

The EC10 values of 40.6 mg Ag/kg dw for mortality and 176.6 mg Ag/kg dw for growth were taken forward to the derivation of the PNEC according to the statistical extrapolation approach.

Executive summary:

The toxicity of silver nitrate to Porcelliunides pruinosus was determined in a non-guideline study. Three separate methods were used to determine the effect on survival, biomass (feeding inhibition) and behaviour (avoidance). Organisms were exposed to ranges of silver nitrate concentrations (0.01 -1000 mg Ag/kg soil dw for survival, 1 -100 mg Ag/kg soil dw for avoidance, 12.5 -200 mg Ag/kg soil dw for biomass) for either 48 hours (avoidance) or 14 days (survival and biomass). A summary of the study report is available as unpublished material from Nanofate.

The EC10 values of 40.6 mg Ag/kg dw for mortality and 176.6 mg Ag/kg dw for growth were taken forward to the derivation of the PNEC according to the statistical extrapolation approach.

Description of key information

Two reliable EC10 values for chronic silver toxicity to biomass and survival of the arthropod Porcellionides pruinosus were identified. The reliable EC10 values range between 40.6 mg Ag/kg dw for mortality of Porcellionides pruinosus and 176.6 mg Ag/kg dw for growth of Porcellionides pruinosus (Nanofate, 2013). All EC10 values are expressed based on total elemental Ag concentrations in soil. All reliable NOEC and EC10 values were taken forward to the derivation of the PNEC according to the statistical extrapolation approach.

Additional information

A single study with Folsomia candida (springtail) is available conducted in Lufa 2.2 soil (pH 5.5, organic carbon 2.09) following ISO-guideline 11267 (van Gestel & Waalewijn-Kool, unpublished Nanofate data). A 28-d EC10 of 47.6 mg/kg based on reproduction was calculated from the data. Since this value was below the lowest test concentration, it was not taken forward to the derivation of the PNEC according to the statistical extrapolation approach.

In addition, a single study for terrestrial crustaceans is from an unpublished study (Nanofate) with the isopod (woodlouse) Porcellionides pruinosus conducted in Lufa 2.2 soil. A 14-d EC10 of 176.56 mg/kg based on biomass and 43.54 mg/kg based on survival were calculated from the data. These values were taken forward to the derivation of the PNEC according to the statistical extrapolation approach.