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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

Short-term toxicity to invertebrates: 48 hr EL50 272 mg/l loading rate (WAFs), Acartia tonsa, (guideline ISO/FDIS 14669 a PARCOM ring test protocol).

Key value for chemical safety assessment

Additional information

A 48-h LL50 value of 272 mg/l and NOELR of 100 mg/l loading rate (WAFs) (not possible to extrapolate to measured concentrations) have been determined for the effects of the registration substance on mobility of the marine copepod Acartia tonsa. The LL50 is above the water solubility limit of the substance (0.0073 – 0.0088 mg/l at 23°C).

For monoconstituent substances it would not normally be appropriate to test at concentrations above the solubility limit. However, the results as reported do provide strong evidence of the absence of toxicity at the solubility limit of the substance following short-term exposures.

This is the only reliable study available for this substance and it has been chosen as key.

A 48-h EC50 value of 169 mg/l has been determined for the effects of the read-across substance trimethox(vinyl)silane (CAS 2768-02-7) on mobility of Daphnia magna. The data indicate that the vinyl side chain is unlikely to contribute significant excess ecotoxicity to the substance.

The data above are supported by read-across evidence relevant to the impurities. The registration substance has an average purity of >80% Vi4-D4, with <15% 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane Vi5-D5 (CAS 17704-22-2; Impurity 1) and <10% 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane Vi3-D3 (CAS 3901-77-7; Impurity 2) present as impurities. After due consideration of the properties, the presence of these impurities is not expected to affect the overall hazard profile of the substance. Read-across studies are in place as supporting studies, to consider the properties of the impurities. Data for Vi5-D5 are read-across from decamethylcyclopentasiloxane D5 (CAS 541-02-6), data for Vi3-D3 are read-across from hexamethyltrisiloxane D3 (CAS 541-05-9). These siloxanes have similar properties with regard to aquatic ecotoxicity.  Further information is given in a supporting report (PFA, 2017) attached in Section 13 of the IUCLID 6 dossier.

A reliable short-termDaphniastudy is available for the siloxane D5 (CAS 541-02-6) and is read-across to Impurity 1 (Vi5-D5). This study (48-h, flow through test withDaphnia magna) gave a result 48-h EC50>2.9 µg/l. EC50was not reached within the limit of solubility in test media.

A reliable short-termDaphniastudy is available for the siloxane D3 (CAS 541-05-9) and is read-across to Impurity 2 (Vi3-D3). This study (48-h, flow through test withDaphnia magna) gave a result 48-h EC50>1.6 mg/l. EC50 was not reached within the limit of solubility in test media.