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Ecotoxicological information

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
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)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Test Item Name CERAPHYL® 41
CAS Number 93925-36-1
Batch/Lot Number 0001749388
Analysed Purity 100 % (Refer Certificate of Analysis in APPENDIX 7)
Manufactured by Ashland Inc.
Supplied to JRF by Ashland Inc.
Date of Manufacture June 18, 2014
Date of Expiry June 18, 2016
Appearance: Clear, water white to straw colored liquid
Storage Temperature: Ambient
Storage Container: In original container as supplied by the Sponsor
Analytical monitoring:
yes
Details on sampling:
The test solutions were analysed for concentration of dedocyl alcohol using the validated analytical method. Quantitative analysis of dodecanol, tridecanol, tetradecanol, dodecyl lactate, tridecyl lactate, tetradecyl lactate, and pentadecyl lactate was done in 100% WAF of CERAPHYL® 41 by area % normalization. Two replicates each of 100.5 mL were centrifuged at 2000 rpm for 10 minutes. Collected sample were centrifuged in order to remove algal cell. Samples were sent for test concentration analysis at 0 h.. Same procedure was followed for sample collection at 24 h, 48 h and 72 h.
Details on test solutions:
Quantity of 202.6 mg CERAPHYL® 41 were weighed in two replicates, and made up to 2000 mL with sterile distilled water in two different glass bottles (stock A and B) and kept for continuous stirring using magnetic stirrer for approximate 24 h at room temperature. After stirring, test solutions were kept for re-equilibrium for approximate 24 h. After phase separation, test solutions were collected from lower portion by “L” shaped glass tube without disturbing the phase. Volume of 1200 mL was collected from each bottle and mixed together (stock C). To prepared the concentration of 100% WAF prepared at 100 mg CERAPHYL® 41/L and OECD medium preparation, after sample collection, total 31.2 mL of OECD stock solutions (24 mL of stock solution I, 2.4 mL of stock solution II, 2.4 mL of stock solution III, and 2.4 mL of stock solution IV) were added to the collected sample for preparation of algal medium and used for the treatment.
The initial cell concentration of the alga stock culture was determined as 6138 cells/mL by using a haemocytometer and microscope. Each replicate was inoculated with 0.5 mL of alga culture to obtain the required cell density.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Strain Number : ATCC 22662
Origin and Source of Culture: American Type Culture Collection, 10801, University of Boulevard, Manassas, Virginia, 20110-2209, USA
Subculture Maintained at : Jai Research Foundation
Date of Receipt (at JRF) : May 13, 2010
Date of Last Subculture : January 19, 2016
Method of Cultivation : Static condition
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
22 - 24 °C
pH:
8.0 - 8.2
Nominal and measured concentrations:
100% WAF prepared at 100 mg CERAPHYL® 41/L corresponding with an initially measured concentration of 1.8 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1.8 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (total fraction)
Basis for effect:
growth rate
Remarks on result:
other: Concentration refers to the nominal loading.
Executive summary:

This study was performed to assess the alga (Pseudokirchneriella subcapitata)growth inhibition caused bywater accommodated fractions (WAFs) of CERAPHYL® 41.Exponentially growing cultures of algae (6138 cells/mL) were exposed to limit test concentration of 100.0% water accommodated fraction (WAF) prepared at 100 mg CERAPHYL® 41/L. A control group was run concurrently. The algal growth was assessed at 24, 48, and 72 h.

The test media were analysed for concentration and stability of the various components in CERAPHYL® 41 based on dodecyl alcohol as a standard at 0 h and every 24 h interval during main study. An initial dodecanol concentration of 0.2 mg/L was measured in the sample taken at the start of the test. This concentration corresponds with 1.8 mg/LCERAPHYL® 41.The dodecanol in test media was unstable as it decreased below detection limit within 24 hours.Quantitative analysis of dodecanol and identification of other components like tridecanol, tetradecanol, dodecyl lactate, tridecyl lactate, tetradecyl lactate, and pentadecyl lactate was done in WAFs of CERAPHYL® 41 prepared at different concentrations.

The percent inhibition and growth rate reduction at tested concentration were 26.74 and 6.15%, respectively. A statistically significant decrease in average specific growth rate was observed in the CERAPHYL® 41 treated solutions compared to the controls. Since the study was conducted as a limit test, no NOEC or LOEC could be determined, but the EC10(0-72h) for growth rate reduction exceeded the solubility limit of CERAPHYL® 41 in water.

Based on the results, it can be concluded that the EC50(0-72 h) for both growth inhibition and growth rate reduction is greater than 100% WAF prepared at 100 mg CERAPHYL® 41/L actually corresponding with an initial concentration of 1.8 mg CERAPHYL® 41/L based on measured dodecanol concentrations, thus exceeding its solubility limit in algal medium. Further, the concentrations of the various components, including the lactates, rapidly decreased to levels below detection. This means that due to its low solubility and high instability in water, environmental concentrations of CERAPHYL® 41 that are toxic to algae are not expected to be achievable.

Description of key information

A study was performed to assess inhibition of growth of the algae Pseudokirchneriella subcapitata when exposed to water accommodated fractions (WAFs) of CERAPHYL® 41. Exponentially growing cultures of algae were exposed to limit test concentration of 100.0% water accommodated fraction (WAF) prepared at 100 mg CERAPHYL® 41/L for 71 hours.

The test media were analysed for concentration and stability of the various components in CERAPHYL® 41 with dodecyl alcohol as an anaytical standard at 0 h and every 24 h interval during main study. An initial dodecanol concentration of 0.2 mg/L was measured in the sample taken at the start of the test corresponding with 1.8 mg/LCERAPHYL® 41. Quantitative analysis of dodecanol and other components like tridecanol, tetradecanol, dodecyl lactate, tridecyl lactate, tetradecyl lactate, and pentadecyl lactate showed that the concentrations of the various components, including the lactates, rapidly decreased to levels below detection.

The percent inhibition and growth rate reduction at tested concentration were 26.74 and 6.15%, respectively. Based on the results, it can be concluded that the EC50(0-72 h) for both growth inhibition and growth rate reduction was greater than 100% WAF prepared at 100 mg CERAPHYL® 41/L, actually corresponding with an initial concentration of 1.8 mg CERAPHYL® 41/L and exceeding its solubility limit in algal medium. It was concluded that, due to its low solubility and high instability in water, environmental concentrations of CERAPHYL® 41 that are toxic to algae are not expected to be achievable.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.8 mg/L

Additional information

The available data hold only very limited information about the NOEC/EC10 for growth rate, so no key values could be provided for the NOEC or EC10. The EC50(0-72 h) for both growth inhibition and growth rate reduction exceeded its solubility limit in algal medium.