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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
25 January 2018 to 06 March 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
761/2009
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
The test substance is listed as PDHP, (CAS # 34562-31-7). The test substance is a yellow to amber colored liquid with > 85% purity. The test substance was obtained from the Sponsor, Vertellus Holdings LLC and stored at room temperature in the dark.
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
The test was carried out using Pseudokirchneriella subcapitata strain CCAP 278/4. Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland. Master cultures were maintained in the laboratory by the periodic replenishment of culture medium. The master cultures were maintained in the laboratory under constant agitation by orbital shaker (100 to 150 rpm) and constant illumination at 24 ±1 °C.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24 °C ± 1 °C
pH:
7.4-8.8
Nominal and measured concentrations:
A preliminary media preparation trial indicated that a saturated solution method of preparation was appropriate for this test item. Based on the results of the range-finding test, the definitive test was conducted with an aqueous solution of the test item at nominal concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution. The 100% v/v saturated solution corresponds to an initial loading rate of 50 mg/L.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate was used as the reference item at concentrations of 0.25 mg/L, 0.50 mg/L, 1.0 mg/L, 2.0 mg/L and 4.0 mg/L.
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
81 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
Statistically-derived value corresponding to an 81% v/v saturated solution prepared from a dilution of an initial test solution with an initial loading rate of 50 mg/L.
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
40 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
Statistically-derived value corresponding to a test solution prepared as a dilution of an initial test solution with an initial loading rate of 50 mg/L, resulting in an 81% v/v saturation solution.
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
32 other: % v/v saturated soluton
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
32% v/v saturated solution prepared from a dilution of an initial test solution with an initial loading rate of 50 mg/L.
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
16 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
Test solution prepared as a dilution of an initial test solution with an initial loading rate of 50 mg/L, resulting in a 32% v/v saturation solution.
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
100 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
100% v/v saturated solution prepared from a dilution of an initial test solution with an initial loading rate of 50 mg/L.
Duration:
72 h
Dose descriptor:
LOELR
Effect conc.:
50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other:
Remarks:
Test solution prepared as a dilution of an initial solution with an initial loading rate of 50 mg/L, resulting in a 100% v/v saturation solution.
Results with reference substance (positive control):
The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

A preliminary media preparation trial indicated that a saturated solution method of preparation was appropriate for this test item. Based on the results of the range-finding test, the definitive test was conducted with an aqueous solution of the test item at nominal concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution. The 100% v/v saturated solution corresponds to an initial loading rate of 50 mg/L. Analysis of the test preparations at 0 and 72 hours showed measured test concentrations of less than the limit of quantification (LOQ) (0.34 mg/L).

Validity criteria fulfilled:
yes
Remarks:
Cell concentrations of control increased by a factor of 157 after 72 h (protocol ≥ factor of 16); mean of coeffs of var.for growth rates control 10% (protocol ≤ 35%); coeff. of var. of avg. sp.growth rate in replicate control cultures 1% (protocol ≤ 7%).
Conclusions:
The test substance caused a reduction of growth in the algal cultures (test units) exposed to test concentrations of the test item for 72 h. The test concentrations included the 100% v/v saturated solution and a series of dilutions containing 0.10, 1.0, 10, and 100% v/v saturated solution. The effects concentrations were reported both as 48-h EC50 of 81% v/v saturated solution and 48-h EL50 of 40 mg/L. The no effects concentrations were reported both as 48-h NOEC of 32% v/v saturated solution and 48-h NOELR of 16 mg/L.

Description of key information

The key study was a static acute toxicity test on the effects of the substance on the freshwater unicellular green alga, Pseudokirchneriella subcapitata following OECD Guideline 201. The test substance caused a reduction of growth in the algal cultures (test units) exposed to test concentrations of the test item for 72 h. The test concentrations included the 100% v/v saturated solution and a series of dilutions containing 0.10, 1.0, 10, and 100% v/v saturated solution.  The effects concentrations were reported both as 48-h EC50 of 81% v/v saturated solution and 48-h EL50 of 40 mg/L.  The no effects concentrations were reported both as 48-h NOEC of 32% v/v saturated solution and 48-h NOELR of 16 mg/L. 

Key value for chemical safety assessment

EC50 for freshwater algae:
40 mg/L
EC10 or NOEC for freshwater algae:
16 mg/L

Additional information