tert-butylphenyldiphenyl phosphate (tBuTPP)

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)

Qualifier:

according to guideline

Guideline:

other: ASTM Standard E729-96: Standard guide for conducting acute toxicity tests on test materials with fishes, macroinvertebrates and amphibians

GLP compliance:

yes

Remarks:

Periodic analyses of water for potential contaminants were not performed according to GLP Standards, but were performed using a certified laboratory and standard US EPA analytical methods.

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples were collected from the batches of test solution prepared for each treatment and
control group at the beginning of the test and from each test chamber at 48 h (± 1 h) to
measure concentrations of the test substance based on the C4 and TPP components.
- Sampling method: The samples were collected at mid-depth, combining with an equal volume of acetonitrile, placed in glass vials,
and processed immediately for analysis.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A primary stock solution was prepared by mixing a calculated amount of test substance in
solvent tetrahydrofuran (THF) at a nominal concentration of 5.0 mg/L. A calculated amount of test
substance was weighed into a tared glass beaker and the test substance was transferred into the
1000 mL glass volumetric flask. The beaker was sonicated for approximately 1 minute to ensure that
all test substance was dissolved in the solvent prior to transferring to the flask. The flask was brought
to volume with THF and the solution was inverted at least 20 times to mix. The stock solution
appeared clear and colorless, with no precipitate noted. Aliquots of the primary stock solution were
added into five 500-mL glass volumetric flasks. The flasks were purged with nitrogen gas for 5 to 10
minutes to evaporate the solvent to dryness. The flasks were brought to volume with dilution water
(UV sterilized well water). The solutions were mixed overnight using stir bars and stir plates. After
mixing, approximately 250 mL of solution was placed in each of two replicate test chambers per
treatment group.
- Controls: negative control solution was dilution water only
- Chemical name of vehicle: tetrahydrofuran
- Evidence of undissolved material: no evidence of precipitate

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source:cultures maintained by Wildlife International, Easton, Maryland
- Age at study initiation (mean and range, SD): < 24 h
- Feeding during test: no

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

132 mg/L as CaCO3 (dilution water at test initiation)

Test temperature:

The target test temperature during the study was 20 ± 1ºC. Temperature was measured in
each test chamber at the beginning and end of the test and at approximately 24 hours during the test
using a liquid-in-glass thermometer. Temperature also was monitored continuously during the test in
a container of water placed adjacent to the test chambers, using a Fulscope ER/C Recorder, which
was verified prior to test initiation with a liquid-in-glass thermometer.

pH:

pH was measured in each test chamber at the beginning and end of
the test and at approximately 24 h during the test. Measurements of pH were made using a
Thermo Orion Model 525Aplus meter.

Dissolved oxygen:

Dissolved oxygen was measured in each test chamber at the beginning and end of
the test and at approximately 24 h during the test. Dissolved oxygen was measured using a
Thermo Orion Model 850Aplus dissolved oxygen meter.

Nominal and measured concentrations:

nominal: 0, 16, 26, 43, 72, 120 μg/L
mean measured based on measured C4: < LOQ, 10, 19, 30, 47, 73
mean measured based on measured TPP: < LOQ, 16, 26, 47, 72, 127

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL glass beaker
- Type (delete if not applicable): open / closed
- No. of vessels per concentration (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Water used for culturing and testing was freshwater obtained from a well approximately 40 m deep located on the Wildlife International site. The well water was passed through a sand filter to remove particles greater than approximately 25 μm, and pumped into a 37800-L storage tank where the water was aerated with spray nozzles. Prior to use, the water was filtered to 0.45 μm to remove fine particles and was passed through an ultraviolet (UV) sterilizer.
- Total organic carbon: < 1 mg C/L (dilution water at test initiation)
- Alkalinity: 172 mg/L as CaCO3 (dilution water at test initiation)
- Conductivity: specific conductance: 343 μS/cm (dilution water at test initiation)

OTHER TEST CONDITIONS
- Photoperiod: 16 h light / 8 h dark
- Light intensity: Light intensity was measured at the water surface of one representative test chamber at the beginning of the
test using a SPER Scientific Model 840006 light meter.

EFFECT PARAMETERS MEASURED
- Immobility (defined as a lack of movement by the organism except for minor activity of the appendages), signs of toxicity, abnormal behaviour
- Observations were made approximately 3.5, 24 and 48 h after test initiation.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.6-1.7

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 73 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

based on measured C4

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

> 73 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

based on measured C4

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 127 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

based on measured TPP

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

> 127 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

based on measured TPP

Validity criteria fulfilled:

yes

Remarks:

(1) immobility of the daphnids in the negative control did not exceed 10% by the end of the test (2) the dissolved oxygen concentration was ≥84% of the air-saturation value throughout the test

Conclusions:

The cladoceran, Daphnia magna, was exposed for 48 h under static conditions to 5 mean measured concentrations of 3 G FF ranging from 10 to 73 μg/L, based on C4 or 16 to 127 μg/L, based on TPP. The 48 h EC50 value was greater than 73 μg 3 G FF/L or 127 3 G FF/L, based on measured C4 or TPP, respectively. The no-immobility concentration and NOEC were both 73 μg 3 G FF/L, based on C4 or 127 μg 3 G FF/L, based on TPP.

Executive summary:

Measurement of test concentrations

Nominal concentrations selected for use in this study were 16, 26, 43, 72 and 120 μg/L. Test solutions in the test chambers at these nominal concentrations appeared clear and colorless during the test, with no evidence of precipitation observed.

The concentrations of 3 G FF based on measured C4 and TPP in the test solutions were determined during the study. Measured concentrations of 3 G FF based on C4 in the samples ranged from approximately 49.3 to 106% of nominal, while the measured concentrations of 3 G FF based on TPP in the samples ranged from approximately 91.7 to 126% of nominal. The measured concentrations of 3 G FF based on C4 in the test solution samples declined on Day 2 of the test. The declines were likely due to adsorption of C4 component to the test chambers since the measured concentrations of TPP remained consistent during the test. When measured concentrations of the samples were averaged, the mean measured test concentrations of 3 G FF based on C4 for this study were 10, 19, 30, 47 and 73 μg/L, representing 63, 73, 70, 65 and 61% of nominal concentrations, respectively. The mean measured test concentrations of 3 G FF based on TPP for this study were 16, 26, 47, 72 and 127 μg/L, representing 100, 100, 109, 100 and 106% of nominal concentrations, respectively. The results of the study were based on the mean measured concentrations of 3 G FF based on both C4 and TPP components of the test substance.

Observations and measurements

Water temperatures were within the 20 ± 1°C range established for the test. Dissolved oxygen concentrations remained ≥ 7.6 mg/L (≥ 84% of saturation) throughout the test. Measurements of pH ranged from 8.2 to 8.5. The measurements of hardness, alkalinity, specific conductance and TOC in the dilution water at test initiation were typical of Wildlife International well water. Light intensity at test initiation was 398 lux at the surface of the water of one representative test chamber.

Daphnia in the negative control group appeared normal throughout the test, with no overt signs of toxicity noted. All daphnids in the 3 G FF treatment groups also appeared normal throughout the test, with no immobility or overt signs of toxicity observed. The exception was noted in two daphnids in the 16 and 26 μg 3 G FF/L nominal treatment concentrations that were trapped at the water’s surface at the first observation, but these daphnids appeared normal after gentle submersion under the water’s surface. The no-immobility concentration and the NOEC were 73 μg 3 G FF/L or 127 μg 3 G FF/L, based on measured C4 or TPP, respectively.

Conditions of validity of the test

The following criteria were used to judge the validity of the test:

1. immobility of the daphnids in the negative control did not exceed 10% by the end of the test

2. the dissolved oxygen concentration was ≥84% of the air-saturation value throughout the test.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

73 µg/L