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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:
Nov 2009 - Jan 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
EC regulation 761/2009
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
sampling at the beginning (t=0h) and at the end of testing (t=72h)
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: ATCC (Amerian Type Culture Collection) 22662
- Source (laboratory, culture collection): LGC Promochem GmbH, Wesel, Germany
- Age of inoculum (at test initiation): 4 days
- Method of cultivation: continiously maintained in cornical flasks containing nutrient medium at 21 to 24°C , continious light 4400-8800lux
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Test temperature:
21°C
pH:
7.3-7.4 (start in test cultures)
7.2 (start in control cultures)
7.5-9.9 (after 72h in test cultures)
9.7 (after 72h in control cultures)
Nominal and measured concentrations:
nominal concentrations: 0.39, 0.78, 1.56, 3.13, 6.25, 12.50, 25.00, 50.00, 100.00mg/L
measured concentrations: 0.38, 0.75, 1.42, 2.83, 6.86, 12.37, 24.69, 50.38, 100.53 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): cornical flasks (Erlenmeyer)
- Material, size, headspace, fill volume: 250ml, 100ml fill volume
- Initial cells density: 10000/ml
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6



GROWTH MEDIUM
- Standard medium used: yes


OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continiously
- Light intensity and quality: 5193lux +-14%



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: determined by Casy Cell Counter, Model DT, Schärfe System GmbH, Germany (pore size:60micro m)



TEST CONCENTRATIONS
- Test concentrations: 0, 0.39, 0.78, 1.56, 3.13, 6.25, 12.50, 25.00, 50.00, 100.00mg/L nominal concentrations
Reference substance (positive control):
yes
Remarks:
K2Cr2O7
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
6.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
6.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
11.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
33.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
72 hr EC50 growth rate: 0.87mg/L K2Cr2O7
72 hr EC50 yield: 0.65mg/L K2Cr2O7

Mean yield, average specific growth rates and percent inhibition:

 

Nominal test substance conc. (mg/L)

Yield (cells x 103/ml)    0-72h

Growth rate (per day)   0-72h

Percent Inhibition based on

 

Mean

SD

Mean

SD

yield

growth rate

0 (control)

855.0

104.3

1.48

0.04

0.0

0.0

0.39

827.9

147.2

1.47

0.06

3.2

0.9

0.78

876.1

110.4

1.49

0.04

-2.5

-0.5

1.56

964.9

110.1

1.52

0.04

-12.9

-2.7

3.13

833.4

241.3

1.46

0.11

2.5

1.5

6.30

889.0

201.8

1.49

0.08

-4.0

-0.4

12.50

371.1

32.3

1.21

0.03

56.6

18.3

25.00

120.5

15.7

0.85

0.04

85.9

42.5

50.00

51.3

21.4

0.58

0.11

94.0

60.6

100.00

6.8

0.9

0.17

0.02

99.2

88.4

Validity criteria fulfilled:
yes
Conclusions:
Test Organism: Pseudokirchnerella subcapitata Test Type: Static
Based on yield/growth rate: 72hr EC50: 11.8 mg a.i./L
72 hr NOEC, based on yield: 6.3mg a.i./L; based on growth rate: 33.5 mg a.i./L
Endpoint Effected: toxicity to aquatic algae and cyanobacteria
Executive summary:

In a 72 hour acute toxicity study, the cultures of Pseudokirchneriella subcapita were exposed to Guanidine Nitrate at nominal concentrations of 0, 0.39, 0.78, 1.56, 3.13, 6.25, 12.50, 25.00, 50.00, and 100.00 mg a.i./L under static conditions in accordance with the EC regulation 761/2009 Part C.3.

The 72h-EC50 values based on yield ( and growth rate) were 11.8mg a.i./L (11.8 mg a.i./L) and

the 72h-NOEC values based on yield (and growth rate) were 6.3 mg a.i./L (33.5 mg a.i./L), respectively.

This toxicity study is classified as acceptable and satisfies the guideline requirements for algal growth inhibition test.

 

Results Synopsis

Test Organism: Pseudokirchnerella subcapitata Test Type: Static

Based on yield/growth rate: 72hr EC50: 11.8 mg a.i./L

72 hr NOEC, based on yield: 6.3mg a.i./L; based on growth rate: 33.5 mg a.i./L

Endpoint Effected: toxicity to aquatic algae and cyanobacteria

Description of key information

In a read-across approach with Guanidine nitrate, in a 72 hour acute toxicity study, the cultures of Pseudokirchneriella subcapita were exposed to Guanidine Nitrate.

The 72h-EC50values based on yield ( and growth rate) were 6.3mg a.i./L (6.3 mg a.i./L) and the 72h-NOEC values based on yield (and growth rate) were 11.8 mg a.i./L (33.5 mg a.i./L), respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
33.5 mg/L
EC10 or NOEC for freshwater algae:
6.3 mg/L

Additional information

In a 72 hour acute toxicity study (Seibersdorf, 2010), the cultures of Pseudokirchneriella subcapita were exposed to read-across substance Guanidine Nitrate. The 72h-EC50 values based on growth rate (yield) were 33.5mg a.i./L (11.8 mg a.i./L) and the 72h-NOEC values based on yield (and growth rate) were 6.3 mg a.i./L, respectively.

The study was performed under static conditions in accordance with the EC regulation 761/2009 Part C.3.

Justification for read-across:

Guanidine hydrochloride and guanidine nitrate dissociate in aqueous media to yield the guanidine ion and the respective anion. Therefore it is reasonable to discuss the effects of the ions separately. The chloride ion is a naturally occurring essential ion in human beings with well-known metabolism and mechanisms of action as described in standard textbooks on pharmacology and physiology. As well it is found as salt in the Earth´s crust and is dissolved in seawater. Effects of guanidine hydrochloride are expected to be based primarily on the guanidine ion. The physiological processing of the guanidine ion is expected to be independent of the individual source. Therefore read-across from guanidine nitrate for effects of guanidine dissociated from guanidine hydrochloride is considered valid. This strategy is supported by a quite similar toxicological profile of both substances, as shown in acute toxicity, irritation, sensitization and genotoxic studies.

A more detailed justification for read-across is attached in IUCLID chapter 13.