Selenium

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Only short summary available, it seems that tests were performed according to scientific standards.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Not reported which guideline was followed. Selenium was added as sodium selenate, and weathered/aged in soil via alternating wetting/drying cycles for 13 weeks. Soil organisms were then exposed for a non-reported test duration for establishment of EC20 ecotoxicological benchmarks based on reproduction.

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

Soil samples from each treatment were taken for Se analysis at test initiation and finalization.

Vehicle:

no

Details on preparation and application of test substrate:

Selenium was added as sodium selenate and weathered/aged in soil via alternating wetting/drying cycles for 13 weeks.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

no data

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Remarks:

exact test duration not reported

Test temperature:

no data

pH:

7.1

Moisture:

no data

Details on test conditions:

TEST SYSTEM
- Test container (material, size): no data
- Amount of soil or substrate: no data
- No. of organisms per container (treatment): no data
- No. of replicates per treatment group: no data
- No. of replicates per control: no data
- No. of replicates per vehicle control: no data

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Sassafras sandy loam (fine-loamy siliceous, mesic Typic Hapludult)
- % sand: 70%
- % silt: 13%
- % clay: 17%
- Organic carbon (%): 1% organic matter
- Maximum water holding capacity (in % dry weigth): no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): reproduction

Nominal and measured concentrations:

no data

Key result

Dose descriptor:

NOEC

Effect conc.:

1.7 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other: NOEC calculated as EC20/2; test duration not reported

Dose descriptor:

other: EC20

Effect conc.:

3.4 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other: test duration not reported

Reported statistics and error estimates:

EC20 estimated by nonlinear regression

Conclusions:

This Klimisch 2 study reports the results of an experiment that evaluated the effects of sodium selenate on the reproduction of Eisenia fetida. The organisms were exposed to spiked soil after 13 weeks of equilibration via alternating wetting/drying cycles. The exposure duration was not reported. The EC20 for reproduction was reported to be 3.4 mg Se/kg dw. An approximate NOEC was obtained dividing the EC20 by a factor of 2, resulting in a NOEC value of 1.7 mg Se/kg dw.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Only short summary available, it seems that tests were performed according to scientific standards.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Not reported which guideline was followed. Selenium was added as sodium selenate, and weathered/aged in soil via alternating wetting/drying cycles for 13 weeks. Soil organisms were then exposed for a non-reported test duration for establishment of EC20 ecotoxicological benchmarks based on reproduction.

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

Soil samples from each treatment were taken for Se analysis at test initiation and finalization.

Vehicle:

no

Details on preparation and application of test substrate:

Selenium was added as sodium selenate and weathered/aged in soil via alternating wetting/drying cycles for 13 weeks.

Test organisms (species):

other: Enchytraeus crypticus

Animal group:

annelids

Details on test organisms:

no data

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Remarks:

exact test duration not reported

Test temperature:

no data

pH:

7.1

Moisture:

no data

Details on test conditions:

TEST SYSTEM
- Test container (material, size): no data
- Amount of soil or substrate: no data
- No. of organisms per container (treatment): no data
- No. of replicates per treatment group: no data
- No. of replicates per control: no data
- No. of replicates per vehicle control: no data

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Sassafras sandy loam (fine-loamy siliceous, mesic Typic Hapludult)
- % sand: 70%
- % silt: 13%
- % clay: 17%
- Organic carbon (%): 1% organic matter
- Maximum water holding capacity (in % dry weigth): no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): reproduction

Nominal and measured concentrations:

no data

Key result

Dose descriptor:

NOEC

Effect conc.:

2.2 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other: calculated as EC20/2, test duration not reported

Dose descriptor:

other: EC20

Effect conc.:

4.4 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other: test duration not reported

Reported statistics and error estimates:

EC20 estimated by nonlinear regression

Conclusions:

This Klimisch 2 study reports the results of an experiment that evaluated the effects of sodium selenate on the reproduction of Enchytraeus crypticus. The organisms were exposed to spiked soil after 13 weeks of equilibration via alternating wetting/drying cycles. The exposure duration was not reported. The EC20 for reproduction was reported to be 4.4 mg Se/kg dw. An approximate NOEC was obtained dividing the EC20 by a factor of 2, resulting in a NOEC value of 2.2 mg Se/kg dw.

Reference 3

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 220 (Enchytraeid Reproduction Test)

Version / remarks:

2004

Deviations:

yes

Remarks:

The optimum temperature for growth and reproduction of E. albidus is between 15 and 21°C. That is why the tests were performed at 18 +- 0.8 °CC instead of 20 +- 0.8 0CC as the guideline No. 220 suggests.

GLP compliance:

not specified

Specific details on test material used for the study:

Na2O4Se, SigmaeAldrich, No. 71948

Analytical monitoring:

yes

Details on sampling:

Soils were sampled from each concentration 24-48 hours after spiking and stored at 4°C for up to one week until Se analyses.

Vehicle:

no

Test organisms (species):

Enchytraeus albidus

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: Pot worm
- Source: originated from the E. albidus stock cultures of the Department of Zoology and Ecology, Szent István University
- Age at test initiation (mean and range, SD): adult worms with fully developed clitellum and visible eggs
- The culture is kept according to Römbke and Moser 2002

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

6 wk

Test temperature:

18 +- 0.8 °C

Moisture:

The soils were watered to 55e60% of their water holding capacity with Na-selenate or Na-selenite solutions.

Details on test conditions:

TEST SYSTEM
- Test container (material, size): 150 mL covered glass containers
- Amount of soil or substrate: 20 g oven dry Ko or KA soil
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 5
- No. of replicates per control: 10

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: A chernozem brown forest soil was collected from the top 20 cm of control plots at the experimental fields of the Agricultural Research Institute “Fleischmann Rudolf” of the Károly Róbert University (designated as Kompolt soil, KO) and a meadow chernozem from the top 20 cm of the control plots at the Research Institute of Karcag (Debrecen University), designated as Karcag soil (KA).
-- % sand: KO: 5%; KA: 0%
- % silt: KO: 49%; KA: 53%
- % clay: KO: 46%; KA: 47%
- Organic carbon (%): KO: 2.7%; KA: 2.9%
- CaCo3: KO: 0%; KA: 2%

OTHER TEST CONDITIONS
- Photoperiod: the tests were performed in total darkness

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mortality and reproduction

Nominal and measured concentrations:

KO soil
selenate
nominal 0.94, 1.88, 3.79, 7.5, 15, 30 mg/kg
measured total 2.92, 6.14, 12.5, 25.6, 49.5, 101.5 mg/kg
measured available 2.79, 6.04, 11.8, 25.1, 48.4, 98.5 mg/kg
selenite
nominal 4.7, 9.38, 18.75, 37.5, 75, 150 mg/kg
measured total 3.88, 8.89, 16.8, 33.2, 70.7, 144.5 mg/kg
measured available 0.27, 0.61, 1.42, 3.37, 10.2, 31.7 mg/kg

KA soil
selenate
nominal 3.38, 6.75, 12.5, 25, 50, 100 mg/kg
measured total 1.66, 3.42, 5.77, 12.9, 24.8, 31.9 mg/kg
measured available 1.55, 2.56, 5.33, 12.4, 24.5, 31.5 mg/kg
selenite
nominal 6.25, 12.5, 25, 50, 100, 150 mg/kg
measured total 8.39, 17.1, 31.3, 62.9, 107.7, 136.1
measured available 2.50, 5.94, 13.1, 32.2, 59.3, 80.2 mg/kg

Key result

Duration:

6 wk

Dose descriptor:

NOEC

Effect conc.:

3.4 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KA soil

Key result

Duration:

6 wk

Dose descriptor:

NOEC

Effect conc.:

3.4 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KA soil

Duration:

6 wk

Dose descriptor:

LOEC

Effect conc.:

5.8 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KA soil

Duration:

6 wk

Dose descriptor:

LOEC

Effect conc.:

5.8 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KA soil

Duration:

6 wk

Dose descriptor:

LOEC

Effect conc.:

<= 2.9 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KO soil

Duration:

6 wk

Dose descriptor:

LOEC

Effect conc.:

<= 2.9 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KO soil

Duration:

6 wk

Dose descriptor:

LC50

Effect conc.:

6.9 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KO soil, R² = 0.97

Duration:

6 wk

Dose descriptor:

LC50

Effect conc.:

6.7 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se, available fraction

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KO soil, R² = 0.98

Duration:

6 wk

Dose descriptor:

LC50

Effect conc.:

6.8 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KA soil, R² = 0.96

Duration:

6 wk

Dose descriptor:

LC50

Effect conc.:

6.2 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se, available fraction

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

KA soil, R² = 0.99

Duration:

6 wk

Dose descriptor:

EC50

Effect conc.:

1.8 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KO soil, R² = 0.95

Duration:

6 wk

Dose descriptor:

EC50

Effect conc.:

1.7 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se, available fraction

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KO soil, R² = 0.96

Duration:

6 wk

Dose descriptor:

EC50

Effect conc.:

5 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Se

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KA soil, R² = 0.99

Duration:

6 wk

Dose descriptor:

EC50

Effect conc.:

4.6 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se, available fraction

Basis for effect:

reproduction

Remarks on result:

other:

Remarks:

KA soil, R² = 0.99

Conclusions:

This Klimisch 1 study was performed according to OECD guideline 220. It was a well performed and well documented study that evaluated the effects of sodium selenite and sodium selenate on reproduction and mortality of adult pot worms (Enchytraeus albidus) for two soils (KO and KA soil). For sodium selenite; the 6-week NOEC for reproduction was 3.9 mg Se/kg dw and 8.4 mg Se/kg dw for KO and KA soil, respectively and the 6 week NOEC for mortality was 8.9 mg Se/kg dw and 8.4 mg Se/kg dw for KO and KA soil, respectively. For sodium selenate; the 6-week LOEC for reproduction was 2.9 mg Se/kg dw and 5.8 mg Se/kg dw for KO and KA soil, respectively and the 6 week LOEC for mortality was 2.9 mg Se/kg dw and 5.8 mg Se/kg dw for KO and KA soil, respectively.

Description of key information

In total, 3 reliable NOEC values for chronic selenate toxicity to terrestrial invertebrates except arthropods were retrieved from 2 published studies (Checkai et al., 2004 and Somogyi et al., 2012). All data were derived from soils amended with disodium selenate. The data cover selenate toxicity to reproduction of 3 different species (Eisenia fetida, Enchytraeus albidus and Enchytraeus crypticus). NOEC values vary between 1.7 mg Se/kg dw for Eisenia fetida and 3.4 mg Se/kg dw for Enchytraeus albidus. All NOEC values are expressed based on added elemental Se concentrations in soil. All reliable NOEC values were taken forward to the derivation of the PNEC according to the statistical extrapolation approach.

Additional information

Reliable results are available for the toxicity of Na₂SeO₃ and Na₂SeO₄ to soil macro-organisms except arthropods. Somogyi et al. (2007 and 2012) studied the effect of both Na₂SeO₃ and Na₂SeO₄ on mortality and reproduction of the potworm Enchytraeus albidus according to the OECD 220 guideline. There was a significant difference in toxicity between selenite and selenate, with selenate showing significantly higher toxicity. This is consistent with data for plants and the lower adsorption of selenate in soil compared to selenite. Therefore, only the available reliable results for selenate are taken into account for the hazard assessment of hexavalent inorganic selenium substances.

Reliable chronic NOEC values for toxicity of sodium selenate are available for 3 organisms: Eisenia fetida, Enchytraeus crypticus and Enchytraeus albidus and vary between 1.7 and 3.4 mg Se/kg soil. The lowest reported reliable NOEC for Na₂SeO₄ was 1.7 mg Se/kg soil (calculated as EC20/2) for reproduction of Eisenia fetida after 13 weeks exposure (Checkai et al., 2004).

All results are based on nominal added or background corrected measured Se concentrations.