Tributyl phosphate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published public domain study

Qualifier:

according to guideline

Guideline:

other: FEA 1984 - Provisional Procedure: extended toxicology test with Daphnia magna (determination of NOEC for reproduction rate, mortality and the time of first appearance of offspring; 21d)

Deviations:

yes

Remarks:

chemical determinations of substance concentrations were modified for reasons of practicality

Principles of method if other than guideline:

The 21-d reproduction test was utilised to determine the effect of tributyl phosphate on Daphnia. A semi-static method was used to determine the NOEC and lethal concentration on the parent Daphnia.

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
Not relevant.

Analytical monitoring:

yes

Details on sampling:

Concentrations: samples were taken twice from selected concentration levels of the test series during the test period and analysed chemically. The first sample was taken before the 7th day (in the period during which no offspring appeared), and the second sample was taken between the 16th and 21st day.

Vehicle:

not specified

Details on test solutions:

The test substance was dissolved in synthetic fresh water (dilution water) using magnetic stirrers for 1 hour.
Graduated dilutions using dilution water were produced in the concentration range in which effects were expected, based on the 24h Daphnia test and a preliminary 3d Daphnia test.
Controls were produced that contained no test substance.

Test organisms (species):

Daphnia magna

Details on test organisms:

The Daphnia magna IRCHA strain was used in the test. The strain had been maintained in accordance with the procedure practised since 1978.
20-30 specimens were placed in forty 2l beakers which had been filled with at least 1.6l Berlin tap water. They provided 24 hour old animals when the offspring were removed daily from the cultures.
Cultures were maintained in dechlorinated and oxygen-saturated tap water (which had been left to stand for 24h) kept at 20 °C. They were kept in glass beakers on a white surface, under exclusion of daylight but lit with fluorescent lamps for 9 hours a day.
Feeding took place daily with dry algae from the Scenedesmus genus; 9g feed suspended in 1L tap water, 2ml of this suspension was added to each culture beaker. Feeding continued throughout the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

No information.

Hardness:

The amount of calcium and magnesium ions in the dilution water was 2.5mmol/L.

Test temperature:

25 ± 1 °C.

pH:

8.0 ± 0.2

Dissolved oxygen:

The water was aerated up to the water saturation level.

Salinity:

Not relevant.

Nominal and measured concentrations:

No information provided.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: open (beakers covered with watch glasses)
- Material, size, headspace, fill volume: 400ml glass beaker with 250ml useful capacity
- Aeration: yes
- Renewal rate of test solution (frequency/flow rate): Semi-static procedure, parent animals transferred to fresh solution 3 times a week
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic fresh water (see below)
- Metals: Molar relationship of sodium to potassium ions was 10:1
- Ca/mg ratio: 2.5mmol/l
- Conductivity: when conductivity was <1µS/com, the dilution water was diluted with 10% tap water
- Culture medium different from test medium: yes; culture medium was 20 °C dechlorinated and oxygen saturated tap water which had been left to stand for 24 hours. pH 7.6-7.7, German hardness 16°.

OTHER TEST CONDITIONS
- Adjustment of pH: pH valure measured as 8.0±0.2
- Photoperiod: 9 hours fluorescent light (7am to 4pm)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : 24h EC0 & EC50, 21d NOEC

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

other: LC0

Effect conc.:

9.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

35 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

No further information

Results with reference substance (positive control):

Not relevant.

Reported statistics and error estimates:

The student's t-test and the U-test were used when calculating the NOEC from the mortality of the parent animals and the reproduction rate.

The NOEC was determined to be 1.3 mg/L in the 21-day reproduction test.

Validity criteria fulfilled:

not specified

Conclusions:

The NOEC was determined to be 1.3mg/L in the 21-day reproduction test.

Executive summary:

The 21-day reproduction test was carried out in Daphnia magna to determine the NOEC for tributyl phosphate. Evaluation parameters for fixing the NOEC were parent animal mortality, reproduction rate and the appearance of the first offspring during the test period. Animals were aged 24 hours at the start of the test. A semi-static procedure was used with open vessels maintained under fluorescent lighting, animals were fed daily with algae suspension (the test was carried out in accordance with an FEA guideline). The 24 hour EC₅₀ value was also determined. The NOEC was found to be 1.3 mg/L in the 21-day reproduction test.

Description of key information

One proprietray and one published study are available.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

1.3 mg/L

Additional information

A 21-day reproduction test was carried out in Daphnia magna to determine the NOEC for tributyl phosphate (Kuehn et al, 1989). Evaluation parameters for fixing the NOEC were parent animal mortality, reproduction rate and the appearance of the first offspring during the test period. Animals were aged 24 hours at the start of the test. A semi-static procedure was used with open vessels maintained under fluorescent lighting, animals were fed daily with algae suspension (the test was carried out in accordance with an FEA guideline). The 24 hour EC50 value was also determined. The NOEC was found to be 1.3 mg/l in the 21 day reproduction test.

The 21 day EC50 (immobilisation) of tributyl phosphate in Daphnia magna is also reported to be >2.1mg/l (ABC Laboratories, 1991).