Disilver oxide

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Non-GLP study, undertaken equivalent to guideline, with analytical monitoring of exposure reported with high-level of detail.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Deviations:

no

GLP compliance:

not specified

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:

Weekly sampling at all treatments: Total and dissolved silver (0.4 μm filter) determined. Samples acidified with nitric acid to pH <2 on collection and analysed the same day.

Vehicle:

not specified

Details on test solutions:

The water source for the diluters was a well located on the Colorado Division of Wildlife's (CDOW) Research Centre property. Different levels of hardness were obtained by mixing well water treated by Reverse Osmosis (RO) with non-treated well water. Chemical stock solutions were prepared about every 4 days.

Test organisms (species):

Salmo trutta

Details on test organisms:

Source: Colorado Division of Wildlife Bellvue Watson Hatchery, with eggs originally obtained from wild fish spawned at Delaney Butte Reservoir in Colorado. Organisms were obtained from hatchery as eyed eggs and were acclimated on hatching trays submersed in their appropriate dilution water priot to initiating experiments. At the end of exposure, fish had an average length of 85 mm and a weight of 6.09 g.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

217 d

Post exposure observation period:

No data reported

Hardness:

Soft (27.9 mg/L CaCO3), medium (200 mg/L CaCO3) and hard (460 mg/L CaCO3)

Test temperature:

13.3°C

pH:

Soft (6.88), medium (7.53) and hard (7.56)

Dissolved oxygen:

Soft (8.68 mg/L), medium (8.91 mg/L) and hard (8.80 mg/L)

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 0.11, 0.2, 0.36, 0.64, 1.12, 1.5, 2.0 μg dissolved silver/L. Measured concentrations: See table

Details on test conditions:

Aquaria - 90 L volume.
Renewal rate: 2 L every three minutes.
Eighty organisms per vessel.
One replicate per concentration.
Feeding: Fish fed Biokyowa. Feeding rate adjusted dependent on volume of uneaten food one hour after feeding.
Aquaria were monitored daily and deaths recorded.
Retarded embryonic development and growth different from control tanks were estimated based on a scale of 1 to 10 from an analysis of four observers.

Reference substance (positive control):

not specified

Key result

Duration:

217 d

Dose descriptor:

EC10

Effect conc.:

0.23 µg/L

95% CI:

>= 0.19 - <= 0.27

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

silver

Basis for effect:

mortality

Remarks on result:

other: water hardness: soft

Duration:

217 d

Dose descriptor:

EC10

Effect conc.:

0.8 µg/L

95% CI:

>= 0.75 - <= 0.85

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

silver

Basis for effect:

mortality

Remarks on result:

other: water hardness: medium

Duration:

217 d

Dose descriptor:

EC10

Effect conc.:

1.39 µg/L

95% CI:

>= 1.22 - <= 1.58

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

silver

Basis for effect:

mortality

Remarks on result:

other: water hardness: hard

Details on results:

Chronic values were defined on the basis of mortality, though very similar toxic limits were also defined based on retarded embryonic development and growth of early life stages. Despite early retardation of development and growth, after more than six months of exposure, fish did not show significant differences in growth between silver exposure concentrations and controls at termination of the experiments.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Effect concentrations were evaluated based on mortality with chronic values calculated from their geometric mean.

Validity criteria fulfilled:

yes

Remarks:

Validity criteria in OECD 201 met

Conclusions:

217 day early-life stage EC10 (mortality) of AgNO3 to Salmo trutta was determined to be 0.23 µg/L dissolved Ag.

Executive summary:

In a non-GLP, guideline test, the 217 day early-life stage EC10 (mortality) of AgNO3 to Salmo trutta was determined to be 0.23 µg/L dissolved Ag.

Reference 2

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Non-GLP study, undertaken equivalent to guideline, with analytical monitoring of exposure reported with high-level of detail.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Deviations:

no

GLP compliance:

not specified

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:

Weekly sampling at all treatments: Total and dissolved silver (0.2 μm filter) determined. Samples acidified with nitric acid to pH <2 on collection and analysed the same day.

Vehicle:

not specified

Details on test solutions:

The water source for the diluters was a well located on the Colorado Division of Wildlife's (CDOW) Research Centre property. Different levels of hardness were obtained by mixing well water treated by Reverse Osmosis (RO) with non-treated well water. Chemical stock solutions were prepared about every 4 days.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Source: Colorado Division of Wildlife Crystal River Hatchery. Organisms were obtained from hatchery as eyed eggs and were acclimated on hatching trays submersed in their appropriate dilution water priot to initiating experiments. At the end of exposure, fish had an average length of 87.9 mm and a weight of 6.82 g.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

196 d

Post exposure observation period:

None

Hardness:

Soft (24.7 mg/L CaCO3), medium (195 mg/L CaCO3) and hard (466 mg/L CaCO3)

Test temperature:

13.1°C

pH:

6.93 (soft), 7.53 (medium) and 7.62 (hard)

Dissolved oxygen:

8.33 mg/L (soft), 8.40 mg/L (medium) and 8.61 mg/L (hard)

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 0.11, 0.2, 0.36, 0.64, 1.12, 1.5, 2.0 μg dissolved silver/L. Measured concentrations: See table

Details on test conditions:

Aquaria - 90 L volume.
Renewal rate: 2 L every three minutes.
Eighty organisms per vessel.
One replicate per concentration.
Feeding: Fish fed Biokyowa. Feeding rate adjusted dependent on volume of uneaten food one hour after feeding.
Aquaria were monitored daily and deaths recorded.
Retarded embryonic development and growth different from control tanks were estimated based on a scale of 1 to 10 from an analysis of four observers.

Reference substance (positive control):

not specified

Key result

Duration:

196 d

Dose descriptor:

EC10

Effect conc.:

0.17 µg/L

95% CI:

>= 0.17 - <= 0.18

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

silver

Basis for effect:

mortality

Remarks on result:

other: soft

Duration:

196 d

Dose descriptor:

EC10

Effect conc.:

0.44 µg/L

95% CI:

>= 0.38 - <= 0.52

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

silver

Basis for effect:

mortality

Remarks on result:

other: medium

Duration:

196 d

Dose descriptor:

EC10

Effect conc.:

0.96 µg/L

95% CI:

>= 0.76 - <= 1.2

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

silver

Basis for effect:

mortality

Remarks on result:

other: hard

Details on results:

Chronic values were defined on the basis of mortality, though very similar toxic limits were also defined based on retarded embryonic development and growth of early life stages. Despite early retardation of development and growth, after more than six months of exposure, fish did not show significant differences in growth between silver exposure concentrations and controls at termination of the experiments.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Effect concentrations were evaluated based on moratlity with chronic values calculated from their geometric mean.

Validity criteria fulfilled:

yes

Remarks:

Validity criteria in OECD 201 met

Conclusions:

The 196 day early-life stage EC10 (mortality) of AgNO3 to Oncorhynchus mykiss was determined to be 0.17 µg dissolved Ag/L.

Executive summary:

In a non-GLP, guideline test, the 196 day early-life stage EC10 (mortality) of AgNO3 to Oncorhynchus mykiss was determined to be 0.17 µg dissolved Ag/L.

Reference 3

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: ASTM 1241-98 (2003)

Principles of method if other than guideline:

ELS – 73 d unmodified water, 77 d – amended water (i.e. 30 d beyond mean day to swimup of the control for each

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples collected from each test chamber on day of test initiation. Further samples collected from randomly selected replicate on day before test initiation and on a weekly basis after test initiation for each treatment with surviving fish.

Details on test solutions:

stock solutions prepared in Milli-Q water

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Kamloops strain - unamended water; Shasta strain - amended water. Spring Creek Hatchery, Lewistown, MT, USA (unamended water). Lost River Trout Mackay, ID, USA (amended water). Life stage used: fertilised eggs.

Test type:

flow-through

Water media type:

freshwater

Total exposure duration:

73 d

Remarks on exposure duration:

73 d in the test with unamended water; 77 d in the test with NaCl-amended water

Hardness:

30-36 mg CaCO3 l-1 (unamended); 30-34 mg CaCO3 l-1 (NaCl-amended) DILUTION WATER

Test temperature:

11-13ºC (both tests)

pH:

7.3 - 8.1 (unamended); 7.3 - 8.1 (NaCl-amended) DILUTION WATER

Dissolved oxygen:

6.6 - 9.1 mg l-1 (unamended); 6.6 - 9.0 mg l-1 (NaCl-amended) DILUTION WATER

Nominal and measured concentrations:

Nominal and measured: See table.

Details on test conditions:

Filtered and sterilized using ultraviolet, Horsetooth Reservoir, Fort Collins, CO, USA. 4.5 l, covered glass chambers with glass drain. Flow rate 20 ml of test solution per min; each test vessel received ~ 7 volume additions per day. Started with 40 eggs/ thinned to 20, 23 eggs not thinned (amended water). Four replicates per concentration. Biomass loading: ≤ 5 g of fish l-1. volume of water in each vessel ~ 4 l. 16:8 light:dark. ≤ 4 foot candles to swim-up, then ambient lighting > 16 foot candles. At swim-up fish started on 4% bw ration of salmon starter no.1 (Zeigler Brothers, Gardners, PA, USA) over 3 feedings daily (2 daily on weekends).
Photoperiod: 16 light : 8 dark
DOC: 2.3-3.0 mg/L in the test with unamended water; 2.3-3.3 mg/L in the test with NaCl-amended water

Reference substance (positive control):

yes

Remarks:

sodium chloride

Duration:

73 d

Dose descriptor:

NOEC

Effect conc.:

> 1.25 µg/L

Nominal / measured:

meas. (TWA)

Basis for effect:

other: Mortality; weight; hatching

Remarks on result:

other: dissolved Ag/L, for survival, mean day to hatch, mean day to swimup, growth and whole-body sodium content in the unamended water.

Duration:

77 d

Dose descriptor:

EC10

Effect conc.:

0.89 µg/L

95% CI:

>= 0.47 - <= 1.69

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: EC10 value recalculated from originally reported data

Duration:

77 d

Dose descriptor:

LC10

Effect conc.:

1.24 µg/L

95% CI:

>= 1.11 - <= 1.37

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mortality

Remarks on result:

other: LC10 value recalculated from originally reported data

Duration:

77 d

Dose descriptor:

NOEC

Effect conc.:

> 2.26 µg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

time to hatch

Details on results:

Survival NOEC >1.25 µg l-1 soft; 1.09 µg l-1 amended (4.4 ± 5 % survival at 2.26 µg l-1). No sublethal effect seen in soft water exposure. Growth (mean dry weight) NOEC 0.21 µg l-1; LOEC 0.48 µg l-1

Reported statistics and error estimates:

NOEC and LOEC values determined using Anova followed by Dunnett’s test, Wilcoxon’s rank sum test or Steel’s many-one rank test. LC10 and EC10 have been re-calculated using log-logistic curve fitting (TRAP software)

See table provided in Materials and methods.

The chronic toxicity of silver to rainbow trout, Oncorhynchus mykiss, was determined in flow-through exposures in two water types; soft water in the presence and absence of 49 mg l-1 NaCl (30 mg Cl l-1). Rainbow trout embryos were exposed to silver (as AgNO3) from 48h or less post-fertilization to 30d post-swimup. The NOEC was > than 1.25 μg dissolved Ag l-1 (measured) for survival, mean day to hatch, mean day to swimup, growth and whole-body sodium content in the unamended water. 96% mortality was observed in the highest test concentration in the NaCl-amended water exposure 4 μg Ag l-1, nominal (2.26 μg dissolved Ag l-1 measured). This concentration was not included in the unamended water exposures. Average dry weights of surviving organisms exposed in NaCl-amended water were significantly reduced in treatments ≥ 0.48 μg dissolved Ag l-1, the NOEC was 0.21 μg dissolved Ag l-1. Differences in sensitivity to silver may have been partly due to the fact that different strains of rainbow trout were used. Whole body silver concentrations increased significantly at 0.13 μg dissolved Ag l-1 (measured) in unamended water and at 1.09 dissolved Ag l-1 (measured) in NaCl-amended water.

Validity criteria fulfilled:

yes

Conclusions:

The 73-day NOEC was >1.25 μg dissolved Ag/L for survival, mean day to hatch, mean day to swimup, growth and whole-body sodium content in the unamended water.
Reliable LC10 and EC10 for O. mykiss for the endpoint mortality of 1.24 μg/L and 0.89 μg/L for the endpoint weight could be extracted. All values are reported as dissolved Ag.

Executive summary:

This guideline study observed GLP and is considered reliable and fully acceptable for use as a supporting study for this endpoint. Reliable LC10 and EC10 for O. mykiss for the endpoint mortality of 1.24 μg/L and 0.89 μg/L for the endpoint weight could be extracted. All values are reported as dissolved Ag.

Reference 4

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study conducted to GLP with analytical verification of doses for some endpoints. For those results where analytical monitoring was not carried out a Klimisch score of 2 is assigned.

Qualifier:

according to guideline

Guideline:

other: ASTM E1241-98

Deviations:

not specified

GLP compliance:

yes

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:

Start, end and random replicates weekly. Clean metal techniques. Sampling equipment rinsed three times with water to be samples prior to collection. Preserved with nitric acid.

Vehicle:

no

Details on test solutions:

The dilution/control water was characterised as very soft to soft water, with both hardness and alkalinity ranging from 20 to 35 mg/L CaCO3. The culture and testing waters for FHMs in the laboratory were obtained from Horsetooth Reservoir (Fort Collins, CO, USA). Water was passed through a sand filter, 1 and 10 µm cartridges and ultraviolet light sterilisation and heated to 25°C before use.

Test organisms (species):

Pimephales promelas

Details on test organisms:

In-house culture - ENSR, Fort Collins, CO, USA. Freshly fertilised eggs. Holding conditions as per test.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

34 d

Remarks on exposure duration:

28 days post hatch in controls; test durations were 32 (HT), 33 (HT-high), and 34 days (HT-high NaCl).

Post exposure observation period:

None

Hardness:

30.5 mg/L CaCO3

Test temperature:

25 °C

pH:

7.3 - 8.2

Dissolved oxygen:

>4.9 mg/L (72% saturation)

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal: Control (0), 0.19, 0.38, 0.75, 1.5, 3.0 μg Ag/L. Measured: Control (<0.044), 0.038, 0.079, 0.147, 0.351, 0.795 μg dissolved Ag/L

Details on test conditions:

2.2 L test volume using 2.5 L test chambers. Aeration not reported. Twenty organisms per vessel. Four replicates per concentration. Biomass loading: < 5 g of fish per litre of water over 24 hour period. 16:8-h light:dark - low ambient (538 lux). Brine shrimp nauplii: 0.5mL per test chamber 3 times per day, increasing to 2.0-2.5 mL per test chamber 3 times per day by the end of the test.
Tests performed under 3 conditions: HT (normal flow conditions in unamended Horsetooth water), HT-high (higher flow conditions in unamended Horsetooth water), and HT-high NaCl (higher flow conditions in Horsetooth water amended with NaCl - nominal chloride concentration of 60 mg/L).
Flow rate was adjusted to deliver a target rate of 50 ml/min (HT-high and HT-high NaCl) or 15 ml/min (HT) to each exposure chamber.
Test durations were 32 (HT), 33 (HT-high), and 34 d (HT-high NaCl).

Reference substance (positive control):

not specified

Duration:

32 d

Dose descriptor:

NOEC

Effect conc.:

0.351 µg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

other: mortality and growth rate

Remarks on result:

other: HT conditions

Duration:

32 d

Dose descriptor:

EC10

Effect conc.:

0.66 µg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mortality

Remarks on result:

other: HT conditions; EC10 value recalculated from originally reported data

Duration:

32 d

Dose descriptor:

EC10

Effect conc.:

0.65 µg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: HT conditions; EC10 value recalculated from originally reported data

Duration:

32 d

Dose descriptor:

NOEC

Effect conc.:

> 0.795 µg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element (dissolved fraction)

Basis for effect:

number hatched

Remarks on result:

other: HT conditions

Duration:

33 d

Dose descriptor:

NOEC

Effect conc.:

0.27 µg/L

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

other: mortality; growth rate; number hatched

Remarks on result:

other: HT-high conditions. Estimated Ag concentrations 81% of nominal Ag as total Ag, 53% as dissolved Ag.

Duration:

33 d

Dose descriptor:

EC10

Effect conc.:

0.42 µg/L

95% CI:

>= 0 - <= 1 542

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

mortality

Remarks on result:

other: HT-high conditions. Estimated Ag concentrations 81% of nominal Ag as total Ag, 53% as dissolved Ag. EC10 value recalculated from originally reported data.

Duration:

33 d

Dose descriptor:

EC10

Effect conc.:

0.32 µg/L

95% CI:

>= 0.23 - <= 0.45

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: HT-high conditions. Estimated Ag concentrations 81% of nominal Ag as total Ag, 53% as dissolved Ag. EC10 value recalculated from originally reported data.

Key result

Duration:

33 d

Dose descriptor:

EC10

Effect conc.:

0.38 µg/L

95% CI:

>= 0.25 - <= 0.59

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

number hatched

Remarks on result:

other: HT-high conditions. Estimated Ag concentrations 81% of nominal Ag as total Ag, 53% as dissolved Ag. EC10 value recalculated from originally reported data.

Duration:

34 d

Dose descriptor:

NOEC

Effect conc.:

1 µg/L

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

mortality

Remarks on result:

other: HT-high NaCl conditions. Estimated Ag concentrations 90% of nominal Ag as total Ag, 67% as dissolved Ag.

Duration:

34 d

Dose descriptor:

EC10

Effect conc.:

0.25 µg/L

95% CI:

>= 0 - <= 70 000 000

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

mortality

Remarks on result:

other: HT-high NaCl conditions. Estimated Ag concentrations 81% of nominal Ag as total Ag, 53% as dissolved Ag. EC10 value recalculated from originally reported data.

Duration:

34 d

Dose descriptor:

NOEC

Effect conc.:

0.5 µg/L

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: HT-high NaCl conditions. Estimated Ag concentrations 90% of nominal Ag as total Ag, 67% as dissolved Ag.

Duration:

34 d

Dose descriptor:

EC10

Effect conc.:

0.86 µg/L

95% CI:

>= 0.56 - <= 1.33

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: HT-high NaCl conditions. Estimated Ag concentrations 81% of nominal Ag as total Ag, 53% as dissolved Ag. EC10 value recalculated from originally reported data.

Duration:

34 d

Dose descriptor:

NOEC

Effect conc.:

> 2 µg/L

Nominal / measured:

estimated

Conc. based on:

element (dissolved fraction)

Basis for effect:

number hatched

Remarks on result:

other: HT-high NaCl conditions. Estimated Ag concentrations 90% of nominal Ag as total Ag, 67% as dissolved Ag.

Details on results:

Dissolved Ag calculated based on mean recovery between unfiltered and filtered samples.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

NOEC and LOEC values determined using Anova followed by Dunnett’s test, or Steel’s many-one rank test. EC10 have been re-calculated using log-logistic curve fitting (TRAP software).

Validity criteria fulfilled:

yes

Conclusions:

Wide confidence intervals of the LC10 values are noted for the endpoint mortality and therefore only the NOEC were selected for that endpoint, i.e. NOEC of 0.351, 0.27 and 1.0 μg/L, resulting in a geomean of 0.46 µg/L.
For the endpoint hatching the EC10 of 0.38 μg/L was selected.
For the endpoint growth the NOEC of 0.351, and the EC10 of 0.32 and 0.86 μg/L were selected, resulting in a geomean of 0.46 µg/L.

Executive summary:

A GLP, guideline, 34 days post-hatch early-life stage test with AgNO3 to Pimephales promelas was performed.

Wide confidence intervals of the LC10 values are noted for the endpoint mortality and therefore only the NOEC were selected for that endpoint, i.e. NOEC of 0.351, 0.27 and 1.0 μg/L, resulting in a geomean of 0.46 µg/L.

For the endpoint hatching the EC10 of 0.38 μg/L was selected.

For the endpoint growth the NOEC of 0.351, and the EC10 of 0.32 and 0.86 μg/L were selected, resulting in a geomean of 0.46 µg/L.

All toxicity values are expressed as dissolved Ag.

Reference 5

Endpoint:

long-term toxicity to fish, other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant, guideline study, fully acceptable for assessment.

Qualifier:

according to guideline

Guideline:

other: ASTM E1191-97 (2003) and ASTM E1241-98 (2003) and conducted following US EPA (1993) GLP rules.

Deviations:

not specified

GLP compliance:

not specified

Remarks:

GLP compliance stated in published article

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:

Samples were collected at start, end and weekly.

Vehicle:

not specified

Details on test solutions:

Filtered seawater from Atlantic Ocean at TR Wilbury Laboratories, Marblehead, Massachusetts. Salinity adjusted by addition of deionised water. Stock solutions prepared in deionized water acidified with 0.2% nitric acid to pH < 2 and stored at room temperature in amber glass bottles.

Test organisms (species):

Menidia beryllina

Details on test organisms:

Embryos and 11 days juveniles obtained from Aquatic Biosystems, Fort Collins, CO, USA. Acclimated to test exposure medium. Embryos were collected during natural spawning of fish that were introduced into spawning tanks < 24 hours before the initiation of a toxicity test. Fertilization was confirmed at test initiation by direct microscopic observation.

Test type:

flow-through

Water media type:

saltwater

Limit test:

no

Total exposure duration:

28 d

Post exposure observation period:

None

Hardness:

No data reported

Test temperature:

25 ± 2ºC

pH:

7.6 - 8.2

Dissolved oxygen:

6.9 - 9.2 mg/L

Salinity:

10, 20 and 30‰ experimental variable

Nominal and measured concentrations:

See table in 'Any other information on materials and methods incl. tables'. Dissolved and free ionic silver concentrations are arithmetic mean measured values.

Details on test conditions:

Glass aquaria lined with Teflon. No aeration. Renewal rate: 4 - 8 volume additions to each test vessel every 24 hours. 20 embryos per vessel. Four replicates per concentration. 16:8 light/dark. 30 - 40 foot candles (4 - 6 µEin/m2/s) 15 minute transition period. Feeding: rotifer, B. plicatilis 1st week, then transition to A. Salina.

Reference substance (positive control):

not specified

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

130 other: μg dissolved Ag/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

silver

Basis for effect:

other: mortality and growth

Remarks on result:

other: at 30% salinity

Details on results:

The effect values from the toxicity test demonstrate that increasing salinity has a mitigating effect on silver toxicity if toxicity is determined using measured concentrations of dissolved silver.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Values for NOEC and LOEC were calculated using ANOVA and a parmetric Dunnettt's test or nonparametric William's test. The LC20 calculated by weighted least-squares nonlinear regression, and the EC50 calculated by binomial/nonlinear interpolation. (p<0.05).

Salinity	NOEC	LOEC	EC20	ACR
‰	µg/L dissolved Ag
Mysids
10	6	13	3.9	>3.2
20	34	60	60	5.8
30	19	37	35	9.3
Fish
10	26	42	38	3
20	49	100	100	1.9
30	130	290	170	> 3

Validity criteria fulfilled:

not specified

Conclusions:

The 28 day NOEC (mortality and growth) is 130 μg dissolved Ag/L.

Executive summary:

This is a GLP, guideline study and is considered reliable and fully acceptable for use for this endpoint.

Description of key information

 Three chronic NOECs or EC10s for ionic silver were taken forward for use in the derivation of the freshwater PNEC by statistical extrapolation. These were an EC10 of 0.46 µg/L Ag for Oncorhynchus mykiss (geometric mean from Davies et al., 1998 and Dethloff et al., 2007), an EC10 of 0.23 µg/L Ag for Salmo trutta (Davies et al. 1998) and an EC10 of 0.38 µg/L Ag for Pimephales promelas (Naddy et al. 2007). A NOEC of 130 µg/L Ag for Menidia beryllina (Ward et al. 2006) is taken forward for the derivation of the marine PNEC. 

Additional information

Key data for three freshwater fish species are available: rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta) and fathead minnow (Pimephales promelas). Key data for O. mykiss are taken from Davies et al. (1998) and Dethloff et al. (2007). Key data for S. trutta are taken from Davies et al. (1998).

 

Davies et al. (1998) undertook six long-term exposures with two species of salmonid to investigate the effects of water quality characteristics on silver toxicity. Salmo trutta (brown trout) and Oncorhynchus mykiss (rainbow trout) were exposed to silver in flow-through tanks under three water “hardness and chloride” regimes (soft, medium and hard). Survival and development were monitored from hatch to 217 days (31 weeks) post-hatch. The test medium for the three “hardness and chloride” regimes was created by diluting well water with reverse osmosis treated well water. As a consequence of this, other physicochemical parameters also varied between the hardness regimes, e.g. DOC and SO₄. EC10 values for chronic S. trutta survival were calculated from the data in the report as 0.23, 0.8 and 1.39 μg/L dissolved silver for soft, medium and hard water, respectively. Similarly, EC10 values for O. mykiss survival were calculated as 0.17, 0.44 and 0.96 μg/L dissolved silver, respectively. Only the results of the soft “hardness and chloride” regime experiments are suitable for use in the calculation of the PNEC/ in the SSDas the study indicates a reduction in silver toxicity (of between three- and six-fold) with increasing water “hardness and chloride”, potentially through modified bioavailability of silver.

 

From Dethloff et al. (2007), reliable EC10 values for O. mykiss of 1.24 μg/L dissolved silver for the endpoint mortality and 0.89 μg/L dissolved silver for the endpoint weight could be extracted. The geometric mean of the EC10 values for O. mykiss survival from Davies et al. (1998) and Dethloff et al. (2007) – respectively 0.17 μg/L and 1.24 µg/L dissolved silver – is 0.46 µg/L dissolved silverand is taken forward for use in the SSD.

 

Additional reliable supporting data for O. mykiss are also available in Davies et al. (1977) and Nebeker et al. (1983). However, the study by Nebeker et al. (1983) is not of comparable duration or sensitivity to Davies et al. (1998) and will therefore not be used in the calculation of the PNEC. The data in Davies et al. (1977) are of similar sensitivity to those presented in Davies et al. (1998) but will not be used in the calculation of the PNEC as the results are based on total rather than dissolved concentrations of silver.

 

Key long-term data for fathead minnow (Pimephales promelas) are taken from Naddy et al. (2007). Naddy et al. (2007) investigated the chronic toxicity of silver to fathead minnows at low and enhanced chloride concentrations. Fathead minnows were exposed to silver in soft reservoir water in standard ASTM early life stage (ELS) toxicity tests (up to 34 days) at one of two flow regimes: normal (15 mL test solution/min) and high (50 mL test solution/min). Chloride concentrations were increased in the enhanced chloride treatment by addition of NaCl to increase the concentration from an original 1.9 mg/L to 58.2 mg/L. EC10 values from this study have been re-calculated using log-logistic curve fitting (TRAP software). Wide confidence intervals of the EC10 values for survival were noted and therefore only the NOEC were selected for that endpoint, i.e. NOEC of 0.351, 0.27 and 1.0 μg/Ldissolved silver (for normal flow/low chloride, high flow/low chloride, and high flow/enhanced chloride treatments, respectively), resulting in a geometric mean of 0.46 µg/L dissolved silver. For the endpoint hatching, a reliable EC10 of 0.38 μg/L dissolved silver could be derived. For the endpoint growth the NOEC of 0.351, and the EC10 of 0.32 and 0.86 μg/L dissolved silver were selected, resulting in a geometric mean of 0.46 µg/L dissolved silver. Additional reliable supporting data are available in Holcombe et al. (1983) but are not used in the SSD as they are based on total silver concentrations.

 

In the marine environment Ward et al. (2006) conducted tests with the fish Menidia beryllina. The 28-day survival NOECs were 26, 49 and 130 µg/L dissolved silver at 10, 20 and 30‰ salinity, respectively. Klein-MacPhee et al. (1984) report a NOEC of 54 µg/L dissolved silver for growth in winter flounder (Pleuronectes americanus) after an 18 day exposure of embryos. Marine fish appear to be somewhat less sensitive to the effects of silver than freshwater species. This is likely to be due to the speciation of silver in marine / estuarine systems.