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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: read-across from a guideline study
Justification for type of information:
The information is retrieved from read across. The read across justification is presented in the Aquatic toxicity Endpoint summary.
Reason / purpose:
read-across source
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
29 mg/L
Basis for effect:
growth rate
Remarks on result:
other: read-across from Methacrylic acid and corrected for difference in log Kow and molecular weight as is shown in the read across rationale.
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
5.3 mg/L
Basis for effect:
growth rate
Remarks on result:
other: read-across from Methacrylic acid and corrected for difference in log Kow and molecular weight as is shown in the read across rationale.
Validity criteria fulfilled:
yes
Remarks:
The Annex XI criteria are fulfilled
Conclusions:
The ErC50 and NOEC for algae are 29 and 5.3 mg/l, respectively.
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:
other: Guideline study, GLP, analytical monitoring, closed vessels
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
At the start of the test, samples were taken of each test solution, using the excess remaining after filling the test vessels, and were analyzed for test substance concentration. At the end of the test each blank solution was sampled and analyzed in the same manner.
Vehicle:
no
Details on test solutions:
Two stock solutions were prepared by direct addition of the test substance to 1000 ml of sterile culture medium to give final concentrations of 410 and 10000 mg/L. The three lowest concentrations were prepared by addition of aliquots of the nominal 410 mg/L solution to sterile medium, to a final volume of 1000 ml. The remaining test concentrations were prepared by addition of aliquots of the nominal 10000 mg/l solution to sterile medium, to a final volume of 1000 ml. Test solutions were all clear and colorless.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Test organisms were from laboratory cultures maintained under axenic conditions. A culture in the exponential growth phase was used as inoculum
for the test.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
standard test medium used
Test temperature:
24°C
pH:
start of test 6.39-8.21
end of test 6.11 - 9.69
Nominal and measured concentrations:
Nominal = 0.86, 1.9, 4.1, 9.1, 20, 45 and 100 mg/L
Geometric mean measured = 0.85, 2.0, 3.7, 8.2, 19, 45, 100 mg/L
Details on test conditions:
Test vessels were borosilicate glass bottles of 50 ml nominal capacity, filled completely with airtight, teflon faced disc/crimp closures. Cultures were incubated at 24+/-2C under continous "cool white" illumination with orbital shaking. Four replicates of the control and duplicates of the test substance were employed. At 24, 48 and 72 hours replicate vessels were sacrificed and counted.
Ph was measured at the start of the test and at the end of the test the pH of two repliacte test solutions (containing algae) from each control and test concentration was determined.
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
45 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
8.2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate and biomass
Details on results:
Mean measured concentration of the test substance ranged from 88 -105% of nominal exposure concentrations
Validity criteria fulfilled:
yes
Conclusions:
In a valid guideline study, the 72 hr EbC50 and ErC50 were 20 and 45 mg/L, respectively for MAA with Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata). The NOEC for growth and biomass was 8.2 mg/L.
Executive summary:

For Methacrylic acid, the algae toxicity was investigated in a study according to OECD TG 201 and in compliance with GLP criteria (MTX, 1999). Cultures of freshwater algae (P. subcapitata) were exposed to nominal test substance concentrations of 0 (control), 0.86, 1.9, 4.1, 9.1, 20, 45 and 100 mg/L in closed vessels for 72 hours under static conditions. Test substance analysis was performed and geomean measured values determined at 0.85, 2.0, 3.7, 8.2, 19, 45 and 100 mg/L (88 -105% of nominal). Cell counts were made at 24, 48 and 72 hours after start of exposure and algal growth rate determined.

The 72 -h ErC50 and 72 -h NOErC values were determined at 45 mg/L and 8.2 mg/L, respectively, based on geometric mean measured concentrations.

Description of key information

The toxicity to algae and cyanobacteria is assessed based on read-across from the close structural analogue Methacrylic acid (CAS# 79 -41 -4). The information on Methacrylic acid is summarised below. The read across rationale is presented in the Aquatic Endpoint summary.

For Methacrylic acid, the algae toxicity was investigated in a study according to OECD TG 201 and in compliance with GLP criteria (MTX, 1999). Cultures of freshwater algae (P. subcapitata) were exposed to nominal test substance concentrations of 0 (control), 0.86, 1.9, 4.1, 9.1, 20, 45 and 100 mg/L in closed vessels for 72 hours under static conditions. Test substance analysis was performed and geomean measured values determined at 0.85, 2.0, 3.7, 8.2, 19, 45 and 100 mg/L (88 -105% of nominal). Cell counts were made at 24, 48 and 72 hours after start of exposure and algal growth rate determined.

The 72 -h ErC50 and 72 -h NOErC values were determined at 45 mg/L and 8.2 mg/L, respectively, based on geometric mean measured concentrations. After correction for difference in molecular weight and log Kow between the source and target substance, the 72 -h ErC50 and 72 -h NOErC values are 29 mg/L and 5.3 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
29 mg/L
EC10 or NOEC for freshwater algae:
5.3 mg/L

Additional information