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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented report but with some deviations from standard method and no analytical monitoring reported.
Qualifier:
according to
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Version / remarks:
Cited as OECD Guide-line 202, part 2 (Daphnia sp., Reproduction Test)
GLP compliance:
no
Analytical monitoring:
not specified
Vehicle:
no
Details on test solutions:
Substance dispersed in water by gentle stirring with glass rod followed by mixing with magnetic stirrer for 1 hour.
Test organisms (species):
Daphnia magna
Details on test organisms:
- Strain/source: clone from "Bundesgesundheitsamt" in Berlin (FRG)
- Breeding method: with Scenedesmus subspicatus as food in wet gravel pit water
- Pretreatment: not reported
- Feeding during test: not fed.
- Control group: not reported.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Post exposure observation period:
Test parameter: reproduction.
Test temperature:
20 ± 1°C
pH:
- pH: not reported. - Adjustment of pH: not reported.
Dissolved oxygen:
Dissolved oxygen: not reported.
Nominal and measured concentrations:
Concentrations: 1, 3.16 and 10 mg/l.
Details on test conditions:
- Renewal of test solution: thrice a week.
- Exposure vessel type: 250 ml beakers.
- Number of replicates, individuals per replicate: 4 replicates with 5 individuals per replicate (250ml) for each concentration of both test and reference substance and controls.
- Intensity of irradiation: not reported.
Photoperiod: 12 hours
Reference substance (positive control):
yes
Remarks:
K2Cr2O7
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Details on results:
- Effect data: no negative effect on reproduction observed with any concentration. Number of young per individual after 21 days >> 60.
Results with reference substance (positive control):
First young born after 10 days (max. 9 days according to guideline 202). Number of young per individual after 21 days » 60.
Concentrations: 0.05, 0.1, 0.2, 0.4 mg/l
Results: Number of young per individual after 21 days » 60.

Description of key information

MDI reacts readily with water to form predominantly insoluble and inert polyurea (Yakabe et al 1994) and therefore long-term tests are not appropriate for the derivation of PNEC values. The available chronic Daphnia magna study (OECD 211) indicated no long-term effects after 21 days exposure to 10 mg/L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
10 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 semi-static study with Daphnia magna (Caspers et al, 1986) with PMDI, no long-term toxicity was observed after 21 days exposure to 10 mg/L, which was the highest concentration tested. The test was carried out according to OECD Guideline 211 and the result was corroborated by the mesocosm study where no chronic effects were seen to the zooplankton at loadings of 1000 and 10,000 mg/L.

MDI is rapidly hydrolysed in aqueous solution. However, MDI is hydrophobic and poorly soluble in water and thus the heterogeneous reaction with water or soil is less rapid. The major product of such a reaction is insoluble polyurea (Yakabe et al 1994). Therefore, the long-term toxicity value is not appropriate to derive PNEC values.