Propane-1,2-diyl dibenzoate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 November 2014 to 26 January 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP and to current guidelines

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Certificate from UK GLP Monitoring Authority

Analytical monitoring:

yes

Details on sampling:

At the start of the definitive test, two samples (20 mL) were taken from the freshly-prepared control and test media. After 72 hours, the contents of the replicate flasks for each group were pooled and further samples taken for analysis. Additional samples were also taken from a flask containing K-Flex PG® at 0.0298 and 10.0 mg/L but with no algal cells, in order to obtain information on the extent of adsorption/absorption of the test substance by the algal cells.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name:
- Strain: CCAP 278/4
- Source (laboratory, culture collection): SAMS Research Services Ltd Dunstaffnage Marine Laboratory Dunbg, Oban, Scotland
- Age of inoculum (at test initiation):
- Method of cultivation:

ACCLIMATION
- Acclimation period: approximately 3 weeks
- Culturing media and conditions (same as test or not):
- Any deformed or abnormal cells observed:

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

24,48 and 72 hours

Test temperature:

22.9 to 23.5 deg. C

pH:

7.97 to 8.99

Dissolved oxygen:

N/A

Salinity:

N/A

Nominal and measured concentrations:

Nominal = 0, 0.0298, 0.954, 0.305, 0.977, 3.13, 10.0 mg/L
Measured = 0, 0.0169, 0.0320, 0.107, 0.298, 1.85, 6.59 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: conical flask
- Type (delete if not applicable): closed with foam bungs and aluminium foil

- Aeration: shaking on orbital shaker at 130 cycles/minute

- Initial cells density: 9.4 x 10 -5


- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates): 1 per concentration

GROWTH MEDIUM
- Standard medium used: yes as in OECD 201



OTHER TEST CONDITIONS
- Sterile test conditions: yes/no

- Photoperiod: 72 h continuous light
- Light intensity and quality: 4440 to 8880 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Coulter Z Series Particle Count and Size Analyser
- Chlorophyll measurement:
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations: nominal, 0.0298, 0.0954, 0.305, 0.977, 3.13, 10.0 mg/L
- Results used to determine the conditions for the definitive study:

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.59 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 0.45 - 1.13

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.53 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 1.44-1.71

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.298 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

1.85 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.28 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield after 72 h

Remarks on result:

other: 0.20- 0.48

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.59 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield after 72 h

Remarks on result:

other: 0.33-0.89

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): No microscopic abnormalities detected

Validity criteria fulfilled:

yes

Conclusions:

The effect of K-Flex PG® on the growth of the unicellular green alga Pseudokirchneriella subcapitata has been assessed over a 72 hour period.

After 72 hours of exposure to K-Flex PG®, the ErC50 (growth rate) and EyC50 (yield) were 1.53 and 0.590 mg/L (measured), respectively.

The “no observed effect concentration” (NOEC) for growth rate and yield was 0.298 mg/L (measured).

Executive summary:

The effect of K-Flex PG^® on the growth of the unicellular green alga Pseudokirchneriella subcapitata has been assessed over a 72 hour period.

After 72 hours of exposure to K-Flex PG^®, the E_rC₅₀ (growth rate) was 1.53 mg/l.

The “no observed effect concentration” (NOEC) for growth rate and yield was 0.298 mg/L (measured).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2013

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This study is classified as reliable with restrictions because it is an acceptable and reliable study carried out by USEPA (Q)SAR ECOSAR (v1.11). The result is calculated data as modelled by EPISUITE. Meets generally accepted scientific principles, acceptable for assessment.

Justification for type of information:

QSAR prediction

Guideline:

other: REACH guidance on QSARs R.6, May/July 2008

Principles of method if other than guideline:

The structure-activity relationships (SARs) presented in ECOSAR are used to predict the aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the aquatic toxicity has been previously measured.  Most SAR calculations in the ECOSAR Class Program are based upon the octanol/water partition coefficient (Kow). SARs are developed for chemical classes based on measured test data that have been submitted by industry or they are developed by other sources for chemicals with similar structures, e.g., phenols.  Using the measured aquatic toxicity values and estimated Kow values, regression equations can be developed for a class of chemicals.  Toxicity values for new chemicals may then be calculated by inserting the estimated Kow into the regression equation and correcting the resultant value for the molecular weight of the compound.

GLP compliance:

no

Remarks:

QSAR

Test organisms (species):

other: Green Algae

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

2.066 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks on result:

other: This value is predicted for the ester class

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

6.243 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks on result:

other: This value is predicted for the baseline toxicity

Conclusions:

Based on the prediction results described, propylene glycol dibenzoate was predicted to have a green alga EC50 of 6.243 mg/L and 2.066 mg/L after 96 hours exposure for the baseline toxicity and the Ester class respectively .

Executive summary:

Based on the prediction results described, propylene glycol dibenzoate was predicted to have a green alga  EC₅₀ of 6.243 mg/L and 2.066 mg/L after 96 hours exposure  for the baseline toxicity and the Ester class respectively .

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

7 November 1997 - 11 November 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study undertaken at GLP accredited laboratory.

Justification for type of information:

A discussion and report on the read across strategy is presented as an attachment in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OTS 797.1050 (Algal Toxicity, Tiers I and II)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations Nominal loadings: 0 (control), 0.10, 0.22, 0.46, 1.0, 2.2, 4.6 and 10 mg/L
- Sampling method: Duplicate samples (200 mL) were taken from control and test cultures at 0 hours and at 96 hours (replicates pooled) for analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The method ofpreparation was selected following advice given in ECETOC 1996 Monograph No 26 as the test material has poor water solubility.
A stock solution of test material in chloroform (100 mg/mL) was prepared , then further stock solutions diluted using chloroform as required to give stock solutions at 46, 22, 10, 4.6, 2.2 and 1.0 mg/mL. 150 µL aliquots of each stock solution were added to autoclaved 2L vessels and the solvent was allowed to evaporate. 1.5 litres of algal medium were added to each vessel, then stirred for at least 18 hours using a magnetic stirrer with a 10 cm magnetic follower stirring at approximately 250 revolutions/minute. After stirring, the solutions were allowed to settle for approximately 1 hour, then a 500 mL (or 1 L for 1.0 mg/L level) aliquot of the water accomodated fraction was removed via a side tap from a mid water position.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): None reported

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Unicellular green algae
- Strain: No. CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae & Protozoa, Institute of Freshwater Ecology, Cumbria, UK
- Method of cultivation: Sterile nutrient medium was inoculated from a master culture and cultured under continuous illumination (c. 7000 lux) in an orbital incubator at 22°C to give an algal suspension in log phase growth, characterised by a cell density of 1.4E+07 cells / mL


ACCLIMATION
- Acclimation period:
- Culturing media and conditions (same as test or not): Lighting conditions used were equivalent to main test; temperature specification was slightly
different (22°C, c.f. 24±1°C in main test).
- Any deformed or abnormal cells observed: None reported

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

24 ± 1°C

pH:

7.3 to 7.4

Dissolved oxygen:

Not quantified - gaseous exchange was ensured by the action of the orbital shaker, oscillating at 120 cycles per minute.

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal loadings: 0 (control), 0.10, 0.22, 0.46. 1.0, 2.2, 4.6, 10 mg/L
Measured concentrations for dipropylene glycol dibenzoate (expressed as % of loading rate)
0.10 mg/L : 99 (Fresh prepared), 50 (expired / 96 hours)
0.22 mg/L : 97, 52
0.46 mg/L: 82, 41
1.0 mg/L: 88, 53
2.2 mg/L: 88, 60
4.6 mg/L: 73, 66
10 mg/L: 69. 51
An additional level at 1.0 mg/L DPGDB with no algae was prepared and found to contain 86% of loading at 96 hours.
Measured concentrations for dipropylene glycol monobenzoate (expressed as % of loading rate dipropylene glycol dibenzoate)
0.10 mg/L : 6 (Fresh prepared), 24 (expired / 96 hours)
0.22 mg/L : 6, 23
0.46 mg/L: 5, 20
1.0 mg/L: 6, 20
2.2 mg/L: 6, 14
4.6 mg/L: 5, 11
10 mg/L: 6, 8
An additional level at 1.0 mg/L DPGDB with no algae was prepared and found to contain 6% of loading at 96 hours.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed (loosely stoppered flasks)
- Material, size, headspace, fill volume: 250 mL flasks containing 100 mL medium.
- Aeration: Gaseous exchange and suspension of the algal cells were ensured by the action of the orbital shaker, oscillating at 120 cycles per minute.
- Renewal rate of test solution (frequency/flow rate): None (static test)
- Initial cells density: 1 x 10^4 cells/mL nominal, control cell density at 0h was 1.48 x 10^4 cells/mL.
- Control end cells density: 1.77 x 10^6 cells/mL
- No. of vessels per concentration (replicates):3
- No. of vessels per control (replicates):3


GROWTH MEDIUM
- Standard medium used: yes (Sterile nutrient medium as recommended in Official Journal No. L383A Part C3).


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Prepared in-house using deionised / reverse osmosis water.


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: Not specified
- Photoperiod: Continuous illumination
- Light intensity and quality: 7000 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter. Measurements taken at 0, 24, 48, 72, and 96 hours.


TEST CONCENTRATIONS
- Spacing factor for test concentrations: Approximately 2.2
- Range finding study
- Test concentrations: range finding studies conducted with initial loading rates of test substance ranging from 0.01 to 10 mg/L.
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

0.15 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

0.89 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EL10

Effect conc.:

0.19 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

96 h

Dose descriptor:

EL10

Effect conc.:

0.87 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

1.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

4.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

0.95 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

3.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

0.22 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

NOELR

Effect conc.:

0.46 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test):
No abnormalities were detected in any of the cultures examined.
Bacterial contamination, observed in some of the test cultures at low levels, was not considered significant. The presence of bacteria during the study is thought to be due to the test substance being a biodegradable substrate for bacteria.
- Any stimulation of growth found in any treatment: A slight increase in growth rate was seen in the 0.10, 0.22 and 0.46 mg/L cultures at 72 hours, and
in the 0.22 and 0.46 mg/L cultures at 96 hours.
The analytical method used to confirm the concentration of test material in solution determined concentrations of dipropylene glycol monobenzoate DPGMB) as well as dipropylene glycol dibenzoate (DPGDB); the concentration of DPGDB was found to be lower after 96 hours than at the start of the test in all cases, whereas the concentration of DPGMB had increased in all samples. This observation suggests that the monobenzoate was a degradation product of the dibenzoate.

Validity criteria fulfilled:

yes

Conclusions:

The EL50 (Area under the curve 72 h) was 1.1 mg/L and the EL50 (Growth rate 0-72 h was 4.9 mg/L while the EL50 (Area under the curve 96 h) was 0.95 mg/L and the EL50 (Growth rate 0-96 h) was 3.6 mg/L.

Executive summary:

Key data is available for propylene glycol dibenzoate (PGDB). This data is supported by relevant information available from a structural analogue Dipropylene glycol dibenzoate (DPGDB). The justification for read across is presented as an attachment included in Section 13 of the IUCLID dossier.

An algal growth inhibition test was conducted to determine the effect on the growth of algae of the test material dipropylene glycol dibenzoate (DPGDB). The study was conducted according to EC, OECD, and US EPA test guidelines, and in compliance with GLP.

The EL₅₀ (Area under the curve 72 h) was 1.1 mg/L and the EL₅₀ (Growth rate 0 - 72 h) was 4.9 mg/L. The corresponding "no-observed effect loading rates" (NOELR) were 0.22 and 1.0 mg/L, respectively. The EL₅₀ (Area under the curve 96 h) was 0.95 mg/L and the EL₅₀ (Growth rate 0 - 96 h) was 3.6 mg/L. A NOELR could not be obtained for Area under the curve 96 h, the NOELR for growth rate was 0.46 mg/L.

Description of key information

Key data is available for propylene glycol dibenzoate (PGDB). This data is supported by relevant information available from a structural analogue Dipropylene glycol dibenzoate (DPGDB). The justification for read across is presented as an attachment included in Section 13 of the IUCLID dossier.

In a GLP, OECD Guideline 201 study in unicellular green alga Pseudokirchneriella subcapitata, the 72-hr NOEC (growth rate) and EC₅₀(gowth rate) rate for propylene glycol dibenzoate was determined to be 0.298 and 1.53 mg/L, respectively (Huntingdon Life Sciences, 2015a; Klimisch score = 1).

Propylene glycol dibenzoate was predicted to have LC₅₀s of 6.243 mg/L (baseline toxicity) and 2.066 mg/L (Ester class) after 96 hours exposure to green algae (US EPA, 2012; Klimisch score = 2).

In a GLP algal growth inhibition conducted according to EC, OECD 201, and US EPA test guidelines, the EL₅₀ (Area under the curve 72 h) for dipropylene glycol dibenzoate was 1.1 mg/L and the EL₅₀ (Growth rate 0 - 72 h) was 4.9 mg/L. The corresponding "no-observed effect loading rates" (NOELR) were 0.22 and 1.0 mg/L, respectively. The EL₅₀ (Area under the curve 96 h) was 0.95 mg/L and the EL₅₀ (Growth rate 0 - 96 h) was 3.6 mg/L. A NOELR could not be obtained for Area under the curve 96 h, the NOELR for growth rate was 0.46 mg/L (Huntingdon Life Sciences, 2001b; Klimisch score = 1).

Key value for chemical safety assessment

EC50 for freshwater algae:

1.53 mg/L

EC10 or NOEC for freshwater algae:

0.298 mg/L