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EC number: 231-717-9
CAS number: 7699-43-6
The aquatic toxicity of the substance zirconium dichloride oxide (a
'water soluble' zirconium compound) is evaluated using data for
zirconium dichloride oxide as well as data from read across substances
such as zirconium acetate (another 'water soluble' zirconium compound),
zirconium basic carbonate (a sparingly soluble zirconium compound) and
zirconium dioxide (an insoluble zirconium compound). Read across from
insoluble or sparingly soluble zirconium substances is considered
acceptable because stirring experiments performed with zirconium
dichloride oxide in aquatic test media (e.g., Harris, 2014; Vryenhoef,
2014) indicated that zirconium from the 'water soluble' zirconium
dichloride oxide does not stay in solution at environmentally relevant
pH levels. Rapid hydrolysis occurs, resulting in precipitation of
zirconium hydroxides or zirconium dioxide. Further, heavy complexing
will occur with phosphates, which results in 100% precipitation whenever
phosphate is present in excess. Complexation with carbonates may also
result in progressive precipitation with increasing pH levels. As a
result, at environmentally relevant conditions, zirconium dichloride
oxide cannot be considered as a water soluble compound. Overall,
zirconium is not bioavailable in the aquatic environment and therefore
no adverse effects are to be expected in aquatic organisms.
Further argumentation for the read across approach is given in the read
across document attached to IUCLID Section 13.
Zirconium dichloride oxide is concluded not to be toxic (acutely) to
fish and aquatic invertebrates. The studies that were used for endpoint
coverage (performed with zirconium dichloride oxide and/or read across
substances) were performed according to internationally accepted
guidelines and did not report any adverse effects (mortality in fish,
immobilization in daphnids) at the limit test concentration of 100 mg/L
or upon exposure to a 100% v/v saturated solution. In algal growth
experiments with read across substances, it was demonstrated that the
observed growth inhibition was concurrent with phosphate depletion.
Toxicity to algae is therefore due to phosphate deprivation as no
primary toxic effects have been observed. Although no phosphate
monitoring was performed during the algal growth inhibition study with
zirconium dichloride oxide (Vryenhoef, 2014), here too, the observed
effect on growth of algae exposed to the 100% v/v saturated solution can
be assumed to be due to phosphate deprivation. This is supported by the
fact that no dissolved zirconium could be detected at levels > LOQ (11
µg Zr/L) in any of the test solutions. Further confirmation for this is
provided by the study of Kumar and Rai (1978), where it was demonstrated
that dosing additional phosphate to the test medium countered the effect
on growth. Phosphate deprivation is a secondary effect which is not
considered relevant at a normal environmental scale. Therefore, no
effects on algae are expected in the environment either. Finally, based
on read across from zirconium acetate, another 'water soluble' zirconium
compound with similar behaviour in the aquatic environment as zirconium
dichloride oxide, the substance is not expected to cause any adverse
effects in aquatic microorganisms either.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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