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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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
not specified
Analytical monitoring:
yes
Remarks:
HPLC
Details on sampling:
At the beginning and end of exposure
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23 +- 2°C
Nominal and measured concentrations:
nominal: 120, 69.8, 40.6, 23.6, 13.8, 8.0 mg/L (common ratio: 1.7) and control group
Details on test conditions:
- Initial cell concentration: 1x10^4 cells/mL
- Exposure period: 72 h
- Culture method: shake cultur (100 rpm)
- Number of vessels: 3 vessels per concentration
- Test volume: 100 mL/ vessel
- Test water temperature: 23 +- 2°C
- Lighting: 4000 - 5000 lux (continuous lighting)
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
40.6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
64.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
The results relate to nominal concentartion based on test substance concentrations
Conclusions:
After 72 h a EC50 of 64.5 mg/L and a NOEC of 40.6 mg/L were determined based on growth rate for adipic acid towards algae.
Executive summary:

A study was conducted in accordance with OECD Guideline for Testing of Chemicals No. 201 'Alga, Growth Inhibition Test' to assess the toxicity of the test substance towards algae after 72 h.

Exponentially growing algal cells (Pseudokirchnerella subcapitata, previously Selenastrum capricornutum) were exposed for a period of 72 hours to a range of concentrations, nominally 120, 69.8, 40.6, 23.6, 13.8, 8.0 mg/L of adic acid and a control. During the test a temperature range of 21 - 25 °C was maintained in the test vessels.

After 72 h a EC50 of 64.5 mg/L and a NOEC of 40.6 mg/L were determined based on growth rate for adipic acid towards algae.

Description of key information

A study was conducted in accordance with OECD Guideline for Testing of Chemicals No. 201 'Alga, Growth Inhibition Test' to assess the toxicity of the test substance towards algae after 72 h.

Exponentially growing algal cells (Pseudokirchnerella subcapitata, previously Selenastrum capricornutum) were exposed for a period of 72 hours to a range of concentrations, nominally 120, 69.8, 40.6, 23.6, 13.8, 8.0 mg/L of adic acid and a control. During the test a temperature range of 21 - 25 °C was maintained in the test vessels.

After 72 h a EC50 of 64.5 mg/L and a NOEC of 40.6 mg/L were determined based on growth rate for adipic acid towards algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
64.5 mg/L
EC10 or NOEC for freshwater algae:
40.6 mg/L

Additional information

Preparing the SIDS-dossier within the scope of the ICCA/HPV-program the study conducted by the National Institute of Technology and Evaluation, Japan was not available. The BASF study was taken into account.

Toxicity to algae was assessed using effect concentration relating to biomass obtained in a study conducted to the EU-method C.2. According to the Guidance on information requirements and chemical safety assessment R.7b (ECHA, 2008) results based on the biomass should not be used for assessment since biomass results depend on the growth rate of the species as well as the test duration and other elements of the test design. Thus, the presented result was scored as not reliable. Reconsiderations results in an 72-h EC50 of 39.8 mg/l and an 72-h EC10 of 14 mg/l.

This study on aquatic algae was characterized by a concentration-dependant decrease of pH. At the end of the 72-hour exposure period, the pH in the control treatment was 10.1, whereas it decreased from 8.2 to 5.4 in the range of concentrations (31.3 - 62.5 mg/L) covering the EC50 value (39.8 mg/L). Furthermore, it should be noticed that the pH value in the control treatment is high compared to the guideline's requirements. Based on this observation, a pH effect cannot be ruled out when considering the toxicity reported in this study.

Describing the toxicity towards aquatic algae, the study conducted by the National Institute of Technology and Evaluation, Japan is preferred, despite deficiencies in study documentation concerning pH.