Diundecyl phthalate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Qualifier:

equivalent or similar to guideline

Guideline:

other: EPA-660/3-75-009

Version / remarks:

(Methods for acute toxicity tests with fish, macroinvertebrates, and amphibians)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Up to 2.10 mg/L (not specified how many concentration s used)
- Sampling method: all test solutions and control test water were analyzed at 0 h and on the last day of the study. In addition, two quality-assurance samples were prepared on each sample collection day and remained with the set of samples through the extraction and analysis procedures. These two samples were prepared in test water or media, with one of the samples prepared at a concentration unknown to the analyst.
The stock solution prepared for each test concentration was sampled in duplicate before it was poured into the test vessels.
At the end of the study, replicate test solutions were combined and duplicate samples were analyzed.
- Sample storage conditions before analysis: sample extracts were stored in a 10-ml serum vial at 0°C until the analysis was performed.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: test solutions were prepared by mixing the appropriate amount of test chemical with the algal growth medium and stirring for 1 h to provide the highest test concentration. Dilutions of this concentration were made to provide additional test concentrations.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Source: no info
- Method of cultivation: not reported

ACCLIMATION
- Acclimation period: not reported
- Culturing media and conditions (same as test or not): according to EPA, 1978. The selenastrum capricornutum printz algal assay bottle test. Environmental Research Laboratory, Corvallis, OR, pp. 1-126.
- Any deformed or abnormal cells observed: not reported.

Test type:

static

Water media type:

freshwater

Total exposure duration:

96 h

Post exposure observation period:

None

Hardness:

25 to 50 mg CaCO3/L

Test temperature:

22 to 24ºC (maintained by a temperature-controlled waterbath)

pH:

7.6 to 7.9

Nominal and measured concentrations:

Highest mean measured concentration: 2.10 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: not specified
- Material, size, headspace, fill volumen: Not specified
- Initial cells density: not reported
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): Not specified
- No. of vessels per vehicle control (replicates): N/A

GROWTH MEDIUM
- Standard medium used: EPA, 1978.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Not specified
- Alkalinity: 25 to 50 mg CaCO3/L
- Intervals of water quality measurement: Temperature was measured at all observation periods (0, 24, 48, 72, and 96 h) in the control vessels.
- Culture medium different from test medium: Not specified

OTHER TEST CONDITIONS
- Photoperiod: Constant illumination
- Light intensity and quality: 60 to 70.5 µE/m2s
- Other: Procedure followed was described by EPA, 1978. Each test vessel was placed on an orbital shaker for the duration of the experiment, and algal assays continued until there was less than 5% change in the daily in vivo chlorophyll-a measurements for a maximum of 10 d. The chlorophyll-a measurements were used to determine when to end the tests.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Cell counts were performed at the end of the test and constituted the criterion for DUP effect.

Acute no-observed-effect concentrations (NOECs) were determined operationally at the end of the test by selecting the highest test concentration at which 10% or less cell count decrease occurred.
This provided a value that was somewhat analogous to an EC10. When ≤10 % cell count decrease was observed at all test concentrations the NOEC was reported as the highest concentration tested.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: Not specified
- Range finding study
- Results used to determine the conditions for the definitive study: Not specified for DUP, only the general procedure was reported: If the range-finding test indicated that toxicity would occur at a concentration below the water solubility of the test chemical, definitive test was done using five concentrations and a control. If the range-finding test indicated that no toxicity would occur at levels up to the water solubility of the chemical, a test with a single concentration was performed at or near the water-solubility limit of the chemical.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 2.1 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

(cell count decrease)

Remarks on result:

other: Insufficient cell count decrease observed at the highest test concentration (value shown) to calculate an acute toxicity value.

Details on results:

It was not possible to calculate acute no-observed-effect concentrations (NOEC) or EC50 values because of a lack of cell count decrease. The acute NOEC was observed to be higher than the highest concentration tested as less than 10% cell count decrease was observed.
The report stated that phthalate esters with alkyl chain lengths of six carbon atoms or more were not acutely toxic at concentrations up to their respective aqueous solubilities (≤ 1.1 mg/L).

Results with reference substance (positive control):

Not applicable

Validity criteria fulfilled:

yes

Conclusions:

In a toxicity test to green algae Selenastrum capricornutum conducted in static conditions, the NOEC of the test substance was established to be higher than the highest concentration tested as less than 10% cell count decrease was observed and accordingly the 96h-EC50 was reported to be higher than 2.10 mg/L.

Executive summary:

An aquatic toxicity study with green algae Selenastrum capricornutum was conducted for DUP following methods for Acute Toxicity Tests with Fish, Macroinvertebrates, and Amphibians (EPA-660/3-75-009), OECD guidelines and EPA GLP. A preliminary range finding study was performed to determine the concentrations used in the main test. The main test was conducted with test concentrations up to 2.10 mg/L for a period of 96 h in static conditions. A validated analytical method based on gas chromatography was used to monitor the concentration of DUP in the test solutions at 0 h and at the end of the study. It was not possible to calculate the NOEC or EC50 because of a lack of cell count decrease. The NOEC was observed to be higher than the highest concentration tested as less than 10% cell count decrease was observed. Based on these results, the 96h-EC50 of the test substance is reported to be higher than 2.10 mg/L.

Description of key information

Key study. Test method according to US EPA (1975): "Methods for acute toxicity tests with fish, macroinvertebrates and amphibiens", OECD guidelines and EPA GLP. DUP was tested with green algae Selenastrum capricornutum in static conditions at concentrations up to 2.1 mg/L. The acute NOEC was observed to be higher than the highest concentration tested as less than 10% cell count decrease was observed. Thus the 96h-EC50 was reported to be higher than 2.10 mg/L. Furthermore, due to the very low water solubility, no acute aquatic toxicity is expected at concentrations up to the water solubility of the test substance.

Key value for chemical safety assessment

EC50 for freshwater algae:

2.1 mg/L

EC10 or NOEC for freshwater algae:

2.1 mg/L

Additional information

Key study. An aquatic toxicity study with green algae Selenastrum capricornutum was conducted for DUP following methods for Acute Toxicity Tests with Fish, Macroinvertebrates, and Amphibians (EPA-660/3-75-009), OECD guidelines and EPA GLP. A preliminary range finding study was performed to determine the concentrations used in the main test. The main test was conducted with test concentrations up to 2.10 mg/L for a period of 96 h in static conditions. A validated analytical method based on gas chromatography was used to monitor the concentration of DUP in the test solutions at 0 h and at the end of the study. It was not possible to calculate the NOEC or EC50 because of a lack of cell count decrease. The NOEC was observed to be higher than the highest concentration tested as less than 10% cell count decrease was observed. Based on these results, the 96h-EC50 of the test substance is reported to be higher than 2.10 mg/L. Furthermore, the study report concluded that phthalate esters with alkyl chain lengths of six carbon atoms or more were not acutely toxic at concentrations up to their respective aqueous solubilities.