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Toxicity to aquatic algae and cyanobacteria

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toxicity to aquatic algae and cyanobacteria
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Good quality report but no analytical monitoring.
according to guideline
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
Analytical monitoring:
not specified
Details on test solutions:
Range finding test: up to 1070 mg/l.
A water accommodated fraction was prepared of 1L medium containing 1640 mg of test substance by stirring for 1 hour. After settling, the clear upper layer of each extract was siphoned off and used in the test.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- Strain/source: Scenedesmus subspicatus (86.81 SAG) from the Collection of Algal Cultures, Institute for Plant Physiology, University of Göttingen, Germany.
- Breeding method: according to OECD guideline.
- Age: not reported.
- Control: yes.
Test type:
Water media type:
Limit test:
Total exposure duration:
3 d
18 mg/L CaCl2.2H2O and 15 mg/L MgSO4.7H2O. This results in a hardness of the medium of 18 mg/L as CaCO3.
NaHCO3 was added at 150 mg/L (different from guideline in order to have greater buffer capacity)
Test temperature:
23 ± 1°C
pH: 8.0-8.2 range throughout the test with and without MDI.
Nominal and measured concentrations:
Loading of 1640 mg/l.
Details on test conditions:
- Renewal of test solution: no. - Exposure vessel type: 200 ml conical flasks. - Number of replicates, individuals per replicate: six replicates with test substance, six control and one background control (coulter counter). Addition of 5.49 105 cell/ml in 100 ml of medium. - Intensity of irradiation: 60-120 µmol/s m2. Photoperiod: not reported.
Reference substance (positive control):
not specified
Not reported.
3 d
Dose descriptor:
Effect conc.:
1 640 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth rate
3 d
Dose descriptor:
Effect conc.:
> 1 640 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
No significant inhibition of growth by MDI.

Control: Growth curve conform to guideline.
Given that the NOEC was found to be 1640 mg/l, an EC50 of >1640 mg/l may be assigned.

Description of key information

In a study with Scenedesmus subspicatus (Blom et al, 1994) no toxicity was observed after 3d exposure to a loading rate of 1640 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 640 mg/L
EC10 or NOEC for freshwater algae:
1 640 mg/L

Additional information

The test substance is covered by the category approach of methylenediphenyl diisocyanates (MDI). Hence, data of the category substances can be used to cover this endpoint. The read-across category justification document is attached in IUCLID section 13. It is important to note that the MDI category approach for read-across of environmental and human hazards between the MDI substances belonging to the MDI category is work in progress under REACH. Therefore the read-across document should be considered a draft.

In a limit test with Scenedesmus subspicatus (Blom and Oldersma, 1994) exposed to PMDI, no toxicity was observed after 72 hours exposure to a loading rate of 1640 mg/L. This was based on the growth rate of the algae. Hence, the 72h-NOELR was 1640 mg/L and the 72h-EC50 was > 1640 mg/L. The test was carried out according to OECD Guideline 201 and the water accommodated fraction method. The result was corroborated by the mecocosm study (Heimbach, 1993), where no effects were seen in the phytoplankton up to 1000 and 10,000 mg/L. Hence, the results indicates that MDI is not toxic to freshwater green algae.

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