Registration Dossier
Registration Dossier
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EC number: 201-286-1 | CAS number: 80-51-3
Endpoint summary
Administrative data
Description of key information
The following ecotoxicity data for aquatic organisms is available for OBSH (m = measured concentration). It should be noted that these values may reflect toxic effects of degradation products as well as the parent compound.
Short-term toxicity
Fish [Oryzias latipes]: LC50(96 hrs) > 6.6 mg/L (m, semi-static)
Invertebrates [Daphnia magna]: EC50(48 hrs) = 2.9 mg/L (m, semi-static)
Algae [Pseudokirchneriella subcapitata]: EC50(72 hrs) = 0.35 mg/L (growth rate) (m, static)
Long-term toxicity:
NOEC for freshwater fish (Oryzias latipes, Early-Life Stage Toxicity Test, 45d): 0.09 mg/L (m, flow-through)
NOEC for freshwater invertebrates (Daphnia magna, 21 d reproduction study): 2.13 mg/L (m, semi-static)
NOEC for fresh water algae (Pseudokirchnerella subcapitata, 3 d, growth rate): 0.059 mg/L (m, static)
Additional information
Furthermore, the hydrolysis studies showed quite short hydrolysis half-lives of 5.9 hr (pH=9), 7.9 (pH=7), 11.7 (pH=4). The pH range of the toxicity studies were in the range of 7.3 – 9.0. At these pH-ranges, a large percentage of the mother substance is degraded (>65% after 12 hours, >88% after 24 hours, >98% after 48 hours) during the test, if no water exchange has been carried out. The main degradation products from the hydrolysis have been identified to be hydrazine (CAS No. 302-01-2) and 4,4’-oxybis(benzenesulfonic acid) (SIDS Initial Assessment Profile,http://webnet.oecd.org/hpv/ui/handler.axd?id=f4e8a387-2cf6-49f6-8af6-78ea04bf97a3). It is very likely that especially hydrazine has contributed to the observed toxicity.
Therefore, the environmental safety assessment must be performed for OBSH degradation products. Hydrazine monohydrate was used as a worst-case scenario, because it is very toxic to environmental organisms and is classified as hazardous to the aquatic environment H400, Acute Hazard, Category 1 and H 410, Chronic Hazard, Category 1 according to the CLP Regulation.
No literature toxicity data can be found for the other main degradation product, namely 4,4’-oxybis(benzenesulfonic acid, but data for similar substances such as Disodium oxybis(methylbenzenesulfonate, 4-hydroxybenzenesulphonic acid, Benzene sulfonic acids and Hydropes were less toxic compared to hydrazine monohydrate.
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