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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Remarks:
based on study on C12 naphthalene
Adequacy of study:
key study
Study period:
from 14 January 2013 to April 11, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: guidance test with GLP compliance
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Qualifier:
according to guideline
Guideline:
other: Commission regulation (EC) No. 440/2008 of 30 May 2008, Part C: Methods for the determination of ecotoxicity, Publication No. L142, C3: “Algal Inhibition Test”; Amended by EC No. 761/2009 of 23 July 2009, Publication No. L220.
Qualifier:
according to guideline
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Qualifier:
according to guideline
Guideline:
other: Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
yes
Details on sampling:
Frequency: at t=0 h, t=24 h and t=72 h
Volume: 1 ml
Storage: Samples were stored in a freezer until analysis.
Vehicle:
no
Details on test solutions:
All test solutions were individually prepared. Preparation of test solutions started with loading rates that were magnetically stirred for one day to ensure reaching maximum dissolution in test medium. This resulted in clear solutions containing a floating layer. Consequently, these were left to settle for another day after which the clear and colourless Water Accommodated Fractions (WAFs) were collected by means of siphoning. The WAFs prepared at 1.0 and 10 mg/l were clear and colourless, whereas the WAF prepared at 100 mg/l was slightly hazy.
After preparation, volumes of 50 ml were added to each replicate of the respective test concentration. Subsequently, 1 ml of an algal suspension was added to each replicate providing a cell density of 10^4 cells/ml.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Species: Pseudokirchneriella subcapitata, strain: NIVA CHL 1
Source: In-house laboratory culture.
Stock culture: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 21-24 °C.
Light intensity: 60 to 120 µE/m2/s when measured in the photosynthetically effective wavelength range of 400 to 700 nm.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
24 mg CaCO3/l
Test temperature:
The temperature of the test medium was 19.2 °C at the start of the test. During the exposure period the temperature measured in the incubator was maintained between 22.2 and 22.7 °C.
pH:
7.9-8.4
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
nominal: WAFs prepared at loading rates of 1.0, 10 and 100 mg/l.
measured: 0.2 mg/l for the nomimal concentration of 100 mg/l
Details on test conditions:
Controls: Test medium without test substance or other additives.
Replicates: 6 replicates of the control and the WAF 100 mg/l,
3 replicates of the WAFs 1.0 and 10 mg/l,
1 extra replicate of each test group for sampling purposes,
1 or 2 extra replicates of each WAF without algae.
Test vessels: 100 ml, all-glass, containing 50 ml of test solution
Medium: M2
Illumination: Continuously using TLD-lamps of the type ‘Cool-white’ of 30 Watt, with a light intensity within the range of 80 to 93 µE/m2/s
Incubation: Capped vessels were distributed at random in the incubator and as such were daily repositioned. During incubation the algal cells were kept in suspension by continuous shaking.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.2 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Details on results:
Analysis of the sample taken at the start of the test from the WAF prepared at 100 mg/l showed a measured concentration of 1880 µg/l for peak 1. This concentration decreased to 286 µg/l after 24 hours and further to 121 µg/l after 72 hours of exposure. For peak 2 the measured concentrations
decreased from 1122 µg/l at the start to 152 µg/l after 24 hours and further to 59 µg/l after 72 hours of exposure.
The study endpoints were based on the Time Weighted Average (TWA) exposure concentrations of peak 2, being a worst-case approach (lowest concentrations measured). The average exposure concentration was calculated to correspond with 0.2 mg/l (201 µg/l).
No significant differences were recorded between the values for growth rate or yield at any of the test concentrations when compared to the control group.
Microscopic observations of the algae exposed to the WAF prepared at 100 mg/l at the end of the test revealed a normal and healthy appearance of the exposed cells when compared to the control.
Results with reference substance (positive control):
The EC50 for growth rate reduction (ERC50: 0-72 h) was 1.7 mg/l with a 95 % confidence interval ranging from 1.2 to 2.3 mg/l. The historical ranges for growth rate reduction lie between 0.82 and 2.3 mg/l. Hence, the ERC50: 0-72 h for the algal culture tested corresponds with this range.
Reported statistics and error estimates:
Statistical analysis of the data was not needed as the effects recorded were not significant (<10 %).
Validity criteria fulfilled:
yes
Conclusions:
Both the EC50 for growth rate reduction (72 h-ERC50) and the EC50 for yield inhibition (72 h-EYC50) exceeded 0.2 mg/l, being the Time Weight Average concentration in a WAF prepared at a loading rate of 100 mg/l.
Executive summary:

Algal growth inhibition test was performed according to OECD guideline No. 201 under GLP compliance. The result showed no reduction of growth rate or inhibition of yield was recorded at any of the WAFs of Alkylated Naphthalene tested. Both the EC50 for growth rate reduction (72 h-ErC50) and the EC50 for yield inhibition (72 h-EyC50) exceeded 0.2 mg/l, being the Time Weight Average concentration in a WAF prepared at a loading rate of 100 mg/l (EL50).

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Remarks:
read-across details
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Basis for effect:
other: based on growth rate and yield
Remarks on result:
not measured/tested
Remarks:
based on read-across
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Basis for effect:
other: based on growth rate and yield
Remarks on result:
not measured/tested
Remarks:
based on read-across
Conclusions:
Based on read-across the EL50 for growth rate and biomass is set at > 100 mg/L. The NOELR is 100 mg/L.

Description of key information

In a study on an analogue, both the EC50 for growth rate reduction (72 h-ErC50) and the EC50 for yield inhibition (72 h-EyC50) exceeded 0.2 mg/l, being the Time Weight Average concentration in a WAF prepared at a loading rate of 100 mg/l (EL50).

The data on the analogue can be used as read-across to assess the toxicity towards algae(see section 13)

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

Algal growth inhibition test was performed according to OECD guideline No. 201 under GLP compliance. The result showed no reduction of growth rate or inhibition of yield was recorded at any of the WAFs of Alkylated Naphthalene tested. Both the EC50 for growth rate reduction (72 h-ErC50) and the EC50 for yield inhibition (72 h-EyC50) exceeded 0.2 mg/l, being the Time Weight Average concentration in a WAF prepared at a loading rate of 100 mg/l (EL50). The NOELR is 100 mg/L for both growth rate and yield.