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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
Study period:
20th May 2019 to 17th June 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Test substance is a UVCB
Analytical monitoring:
yes
Details on sampling:
At the start, samples were taken from one additional replicate of each test item concentration and the control and at the end samples were taken from pooled replicates. Samples were analyzed with a LC-MS method, implemented under non-GLP and documented finally in the GLP raw data. The method was validated as stated in Annex I. All concentration levels and the control were analytically verified via LC-MS at the start (0 hours) and at the end of the exposure (72 hours) with algae
Vehicle:
yes
Details on test solutions:
Water accommodated fractions (WAF) were prepared because the test item is an UVCB substance with compounds of different and low water solubility (measured water solubility is approximately 0.4 mg/L). This procedure is in accordance with the OECD guidance document No. 23 (2018) and ASTM D6018 (2014). Using this approach, aqueous media were prepared by mixing the test item with water for a prolonged period sufficient to ensure equilibration between the test item and the water phase. Five water accommodated fractions (WAF) were prepared separately with nominal loading rates of the test item in the range of 1.00 to 100 mg/L set up in a geometric series with a factor of V10: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L. The water accommodated fractions (WAF) were prepared 24 ± 1 hour prior to the start of the exposure in a tightly closed glass flask with a side-arm near the bottom. The procedure according to ASTM D6081 (2014) was carried out. For each loading rate, an appropriate amount of the test item was pipetted onto the surface of an appropriate amount of dilution water (see Table 2). The dispersion was stirred for 24 + 1 hour at approximately 500 rpm at room temperature, creating a vortex within the cylinder of ca. 10% of the liquid depth. After completion of stirring, the stock solution was allowed to stand for 1 hour at room temperature. Then the WAFs were removed via the side-arm of the flask (from the approximate bottom of the glass flask). At least the first 25 mL were discarded. The WAFs were checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was negative
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Pseudokirchneriella subcapitata is a suitable green alga species according to the guideline. Fresh stocks are prepared every month on Z-Agar. Light intensity amounted to 2567 - 5130 lux (35 - 70 pE • nr2 • s_1) for 24 hours per day. The culture medium used was Nutrient medium Z according to LGttge et a/. (1994)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
52mg CaCO3/L
Test temperature:
Nominal range: 21 - 24°C, controlled at ± 2°C
pH:
The pH of the test medium had to be 7.5 + 0.1 and was adjusted prior to testing with addition of 1 M NaOH and HCI
Conductivity:
233µS/cm
Nominal and measured concentrations:
Five Water Accommodated Fractions (WAF) were tested with a nominal loading rates set up in a geometric series with a factor of V10: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L.
Details on test conditions:
Light intensity (target)
Approximately 4440 to 8880 lux, corresponding to 60 to
120 pE*rrr2*s'1
Light regime
24 hours/day light
Light homogeneity (target)
Within ± 15% over incubation area
Reference substance (positive control):
yes
Key result
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
ca. 2.89 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.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
The toxicity of potassium dichromate (Sigma Aldrich, batch number MKBV0900V, purity 99.0%, CAS RN 7778-50-9) to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined over a period of 72 hours from 2019-03-05 to 2019-03-08. The reference item toxicity is in the valid range which was established by calculation of the average of the historic reference data since 2005, and the limits were set using the threefold standard deviation of these values.

EC 50-Values of the Reference item based on nominal concentrations [mg/L], (0-72 hours)

SD = Standard deviation

   Current Study  Valid Range (average +/- 3 x SD)
   Growth Rate Inhibition  
 ErC50  0.701     0.752 +/- 0.534
 95% Confidence interval  0.660 -0.750
       Yield inhibition
 EyC50  0.353     0.405 +/-0.308
 95% Confidence interval  0.312 -0.394
Validity criteria fulfilled:
yes
Conclusions:
The test substance was found to inhibit the growth of the freshwater green alga Pseudokirchneriella subcapitata after 72 hours. The EL50-values for inhibition of growth rate (ErL50 and yield (EyL50) after 72 hours were > 100 mg/L and 9.90 (1.98 - 48.4) mg/L, respectively. The EL10-values for inhibition of growth rate (ErL10) and yield (EyL10) after 72 hours were 2.89 (< 1.00 - 13.8) mg/L and < 1.00 mg/L, respectively. The NOEL-values for both inhibition of growth rate and yield after 72 hours were < 1.00 mg/L
Executive summary:

The toxicity of the test substance to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201 guidelines. The aim of the study was to determination NOEL, LOEL, EL10, EL20- and EL50 values of growth rate and yield over a period of 72 hours. The test item is an UVCB substance with compounds of different water solubility. Therefore, a water accommodated fraction (WAF) was prepared. Using this approach, aqueous media were prepared by mixing the test item in dilution water for a prolonged period sufficient to ensure equilibration between the test item and the water phase. Five Water Accommodated Fractions (WAF) were tested with a nominal loading rates set up in a geometric series with a factor of 3.16: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L. The WAFs were checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was negative. Three replicates were tested for each test item loading and six replicates for the control. The test media were clear throughout the test period. The environmental conditions were within the acceptable limits.

The concentration of the test substance was analytically verified via LC-MS/MS in fresh media at the start of the exposure (0 hours) and in the corresponding old media at the end of the exposure (72 hours) in all replicates with algae. At the end of exposure after 72 hours, the measured concentrations were in the range of 100% to 118% of the initially measured concentrations. As the test item is a UVCB and it was not possible to analytically identify the constituent(s) being measured and how much of the constituent(s) was contained in the test substance, all effect values given are based on the nominal test item loading rates of the test substance. In this study, test susbtance was found to inhibit the growth of the freshwater green algae Pseudokirchneriella subcapitata after 72 hours. The EL50-values for inhibition of growth rate (ErL50 and yield (EyL50) after 72 hours were > 100 mg/L and 9.90 (1.98 - 48.4) mg/L, respectively. The EL10-values for inhibition of growth rate (ErL10) and yield (EyL10) after 72 hours were 2.89 (< 1.00 - 13.8) mg/L and < 1.00 mg/L, respectively. The NOEL-values for both inhibition of growth rate and yield after 72 hours were < 1.00 mg/L.

Description of key information

Under the conditions of this study, exposure of the test material to the growth rate of Pseudokirchneriella subcapitata has been investigated and gave a 72 -hour EL50 value of greater than 100 mg/L loading rate WSF. Consequently, the EL10 was determined to be 2.89 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
2.89 mg/L

Additional information

The toxicity of the test substance to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201 guidelines. The aim of the study was to determination NOEL, LOEL, EL10, EL20- and EL50 values of growth rate and yield over a period of 72 hours. The test item is an UVCB substance with compounds of different water solubility. Therefore, a water accommodated fraction (WAF) was prepared. Using this approach, aqueous media were prepared by mixing the test item in dilution water for a prolonged period sufficient to ensure equilibration between the test item and the water phase. Five Water Accommodated Fractions (WAF) were tested with a nominal loading rates set up in a geometric series with a factor of 3.16: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L. The WAFs were checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was negative. Three replicates were tested for each test item loading and six replicates for the control. The test media were clear throughout the test period. The environmental conditions were within the acceptable limits.

In this study, test substance was found to inhibit the growth of the freshwater green algae Pseudokirchneriella subcapitata after 72 hours. The EL50-values for inhibition of growth rate (ErL50 and yield (EyL50) after 72 hours were > 100 mg/L and 9.90 (1.98 - 48.4) mg/L, respectively. The EL10-values for inhibition of growth rate (ErL10) and yield (EyL10) after 72 hours were 2.89 (< 1.00 - 13.8) mg/L and < 1.00 mg/L, respectively. The NOEL-values for both inhibition of growth rate and yield after 72 hours were < 1.00 mg/L.

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