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One available study examined the acute toxicity effects of the test substance,disodium disilicate (delta-crystalline)in fish (Danio rerio). The LC50 was determined to be above than 500 mg/L.

The effects ofdisodium disilicate (delta-crystalline)to Algae (Scenedesmus subspicatus) were examined in two growth inhibition test studies. In both studies the NOEC (72 hour) was determined to be 18 mg/L. The EbC50 in both studies were similar (51.6 mg/L and 44.1 mg/L). In the key study higher concentrations were also examined while the pH was adjusted (to 7.6), the obtained NOEC was thereby higher, 100 mg/L.

One study examined the effect of the test substancedisodium disilicate (delta-crystalline)on micro-organisms, by means of measuring the inhibitory effect in respiration (oxygen consumption) of micro-organisms in activated sludge taken from a domestic sewage. The EC50 value obtained in the study was 720 mg/L fordisodium disilicate (delta-crystalline).

The following studies were waived:

In accordance with column 2 of REACH Annex IX, a long-term toxicity test with aquatic invertebrates and a long term toxicity test with fish (required in section 9.1.5 and 9.1.6 respectively) does not need to be conducted in accordance to the chemical safety assessment indicating thatdisodium disilicate (delta-crystalline)needs no further investigation regarding these two kind of studies. The substance is expected to have a low potential for bioaccumulation (log Kow expected3 as the substance is not soluble in octanol).In addition it was shown that disodium disilicate (delta-crystalline) is hydrolysed to water glass in aqueous solution which is identical to silicate. Therefore it can be concluded that disodium disilicate (delta-crystalline) is hydrolytically degraded to a naturally occurring substance which is widespread in nature. In addition the concentration related silicate-release of disodium disilicate (delta-crystalline) is not expected to be significantly higher than natural fluctuations in silicate levels.Thus, based on this assessment a long-term toxicity test is not scientifically justified and not in line with animal welfare.