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EC number: 231-717-9
CAS number: 7699-43-6
Chemical analysis of the test preparations at 0 and 48 hours showed
measured dissolved zirconium concentrations of less than the limit of
quantitation (LOQ) of the analytical method employed (which was
determined to be 0.051 mg Zr/L). As a result, it was considered
unnecessary to carry on to the definitive stage of testing.
The acute toxicity of zirconium dichloride oxide to Tubifex
tubifex was studied under semi-static conditions according to the
APHA method. Tubifex tubifex were exposed to control and test
chemical following a logarithmic scale for 96 hours. Mortality and
immobilization were recorded at intervals of 30 min and 1, 2, 4, 8, 14,
33, 48 and 96 hours. No significant immobilization was observed after 96
The endpoint was covered using a weight of evidence approach including two studies with zirconium dichloride oxide (Harris, 2014; Khangarot, 1991) and a read across study with zirconium dioxide (Bazin, 1994). All studies indicate that zirconium is not toxic to aquatic invertebrates, with the EC50 values being > 100% v/v saturated solution (Harris, 2014) or > 100 mg/L (initial loading rate, Khangarot, 1991; Bazin, 1994). Although zirconium dichloride oxide is a 'water soluble' compound, zirconium precipitates out of solution at environmentally relevant conditions, justifying read across from zirconium dioxide (which is an insoluble zirconium compound) to zirconium dichloride oxide.
Three relevant studies were identified and were used in a weight of
evidence approach to cover this endpoint.
In the most recent study of Harris (2014), a range finding study was
performed in which the highest test concentration was a 100% v/v
saturated solution of zirconium dichloride oxide. No immobility was
observed after 48 hours, which leads to an EC50 > 100% v/v saturated
solution. Dissolved zirconium concentration was < LOQ (i.e. 0.051 mg
Zr/L) in all treatments. Because zirconium was not available to cause
effects in Daphnia magna, no further testing was performed.
The second study (Khangarot, 1991) investigated the toxicity of
zirconium dichloride oxide to Tubifex tubifex. The worms were exposed up
to 96 h. The EC50 values determined at 24 h, 48 h and 96 h were all >
100 mg/L expressed as elemental zirconium or zirconium dichloride oxide.
The study was however considered reliable with restrictions since no
analytics were performed and not all details on the results were shown.
Because of the precipitation of zirconium at environmentally relevant
conditions, it is considered justified to perform read across from
insoluble zirconium substances such as zirconium dioxide (for further
argumentation reference can be made to the read across document attached
to IUCLID Section 13). Therefore, the study from Bazin (1994) performed
with zirconium dioxide (an insoluble zirconium compound) was included in
the weight of evidence approach.
In this study, the acute toxicity of zirconium dioxide to Daphnia magna
was studied under static conditions according to EU method C2. No
significant immobilization was observed at a loading rate of 100 mg/L
(ZrO2). The 48-h EC50 was thus superior to this value.
In conclusion, at environmentally relevant pH values, zirconium
dichloride oxide can be concluded not to cause any acute adverse effects
in aquatic invertebrates.
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