Tris(2,4-ditert-butylphenyl) phosphite

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1988-11-30

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

yes

Remarks:

It was used a settled sludge. The substance was not dissolved but distributed in the test medium. The sludge concentration in the test bottles was 2 g/L instead of 1.4 - 1.8 g/L.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stock solution: 20.8 rsp. 20.2 mg of the test substance were weighed and added to the test medium. The volume was adjusted to 200 mL with bidistilled water and aerated for 3 hours.
- Evidence of undissolved material (e.g. precipitate, surface film, etc):

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Preparation of inoculum for exposure: according to the method described in the guideline. Instead of a centrifuged sludge a settled sludge was used.
- Initial biomass concentration: 2.0 g/L

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

none

Test temperature:

20 ± 2 °C

pH:

not determined

Nominal and measured concentrations:

104 and 101 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: BOD flasks with gas inlet
- Material, size, headspace, fill volume: 250 mL (size)
- Aeration: none during the test
- No. of vessels per concentration: 1
- No. of vessels per control: 1
- Biomass loading rate: 2 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated drinking water
16 g Peptone
11 g Meat extract
3.0 g Urea
0.7 g NaCl
0.4 g CaCl2 • 2 H2O
0.2 g MgSO4 • 7 H2O
2.8 g K2HPO4
per liter dechlorinated drinking water

OTHER TEST CONDITIONS
- Adjustment of pH: none

EFFECT PARAMETERS MEASURED: Oxygen consumption per hour in mg/liter

TEST CONCENTRATIONS
- Spacing factor for test concentrations: single dose in duplicate
- Justification for using less concentrations than requested by guideline: expected low toxicity of the test substance

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol at 32, 10, and 3.2 mg/L

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Graphically determined

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: IC20

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Graphically determined

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: IC80

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Graphically determined

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

- Any observations that might cause a difference between measured and nominal values: none reported
- Effect concentrations exceeding solubility of substance in test medium: none reported

Results with reference substance (positive control):

- Results with reference substance valid: yes
- Relevant effect levels: IC50 12 mg/L, graphically determined

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when tris(2,4-di-tert-butylphenyl)phosphite introduced in appropriate low concentrations.

Additional information

The toxicity of tris(2,4-di-tert-butylphenyl)phosphite on microorganisms was tested in a limit test performed according to OECD guideline 209 [Ciba, 1988]. At the test concentration of about 100 mg/L no effect on the respiration rate of activated domestic sludge was measured.