Sodium selenite

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Standard guideline followed (OECD 220, 2003), well performed and well documented study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 220 (Enchytraeid Reproduction Test)

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

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

Vehicle:

no

Details on preparation and application of test substrate:

see test conditions

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

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

6 wk

Test temperature:

18 degree C

pH:

7.1

Moisture:

soil was watered to 55% WHC

Details on test conditions:

TEST SYSTEM
- Test container (material, size): 150 mL containers covered by their own cups and randomly placed in a thermostat
- Amount of soil or substrate: 20 g oven dry soil
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 5
- No. of replicates per control: 5

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Nagyhörcsök, Hungary (soil from control plots of the experimental field of the Research Institute for Soil Science and Agricultural Chemistry (RISSAC) of the Hungarian Academy of Sciences)
- Soil texture (if natural soil): calcareous loamy chernozem with medium to deep humus layer formed on loess
- % sand: no data
- % silt: no data
- % clay: 20%
- Organic carbon (%): 3.1% organic matter
- eCEC: 40 meq/100g
- background concentration: 0.23 and 0.77 mg Se/kg dw for reproduction and mortality assay, respectively

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:

Measured: 0.77-6.21-12.8-24.8-42.6-76.6-132.0 mg Se/kg dw (mortality tests)
Measured: 0.23-1.20-2.35-5.08-9.975-20.55-43.95 mg Se/kg dw (reproduction tests)

Duration:

6 wk

Dose descriptor:

NOEC

Effect conc.:

2.12 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se (added concentration)

Basis for effect:

reproduction

Remarks on result:

other: total concentration: 2.35 mg Se/kg

Duration:

6 wk

Dose descriptor:

EC10

Effect conc.:

2.57 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se (added concentration)

Basis for effect:

reproduction

Remarks on result:

other: total concentration: 2.8 mg Se/kg (95% CL: 1.61-3.74)

Duration:

6 wk

Dose descriptor:

EC50

Effect conc.:

7.07 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se (added concentration)

Basis for effect:

reproduction

Remarks on result:

other: total concentration: 7.3 mg Se/kg (95% CL: 6.2-8.5)

Duration:

6 wk

Dose descriptor:

NOEC

Effect conc.:

5.44 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se (added concentration)

Basis for effect:

mortality

Remarks on result:

other: total concentration: 6.21 mg Se/kg

Duration:

6 wk

Dose descriptor:

LC10

Effect conc.:

6.53 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se (added concentration)

Basis for effect:

mortality

Remarks on result:

other: total concentration: 7.3 mg Se/kg (95% CL: 5.07-6.21)

Duration:

6 wk

Dose descriptor:

LC50

Effect conc.:

21.73 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Se (added concentration)

Basis for effect:

mortality

Remarks on result:

other: total concentration: 22.5 mg Se/kg (95% CL: 19.6-25.7)

Reported statistics and error estimates:

The NOEC for reproduction and mortality was calculated by the t test.
Probit analysis was based on linear maximum likelihood regression.

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 on reproduction and mortality of adult pot worms (Enchytraeus albidus). The 6-week NOEC for reproduction was 2.35 mg Se/kg dw and for mortality was 6.21 mg Se/kg dw.

Description of key information

The lowest reliable EC10 for Na₂SeO₃ is 2.57 mg Se/kg soil (added concentration) for reproduction of Enchytraeus albidus after 6 weeks exposure, according to the OECD 220 guideline (Somogyi et al., 2007; Klimisch 1).

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil macroorganisms:

2.57 mg/kg soil dw

Additional information

Reliable results are available for the toxicity of Na₂SeO₃ and Na₂SeO₄ to soil macro-organisms except arthropods. Somogyi et al. (2007) 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 selenite are taken into account for the hazard assessment of tetravalent inorganic Se substances.

Reliable chronic toxicity data for sodium selenite are only availble for Enchytraeus albidus and vary between 2.6 and 8.4 mg Se/kg soil (lowest value reported for reproduction after 6 weeks exposure, Somogyi et al., 2007).

In addition, reliable chronic NOEC or EC10 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 Na₂SeO₄was 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.