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EC number: 231-717-9
CAS number: 7699-43-6
PNEC values for the aquatic compartment cannot be derived. The available
acute ecotoxicity tests in fish and daphnids show EC50 or LC50 values
which are higher than 100 mg/L (based on added test substance) or > 100%
v/v saturated solution. When zirconium dichloride oxide is dissolved in
a buffered aqueous solution (such as a natural surface water)
precipitation of zirconium as zirconium hydroxide/zirconium dioxide (pH
dependent), zirconium carbonate (pH dependent) and/or zirconium
phosphate will occur. The precipitation of zirconium phosphate in algal
test media seems to result in some growth inhibition due to phosphate
deprivation (i.e., a secondary effect). This was demonstrated in algal
growth inhibition experiments with read across substances. The fact that
in an algal growth inhibition test with zirconium dichloride oxide no
measurable zirconium concentrations > LOQ (11 µg Zr/L) could be detected
in any of the treatments whereas significant reduction of growth was
observed in the 100% v/v saturated solution supports the assumption that
the observed effects are not due to primary exposure to bioavailable
zirconium, but rather due to a secondary effect such as phosphate
deprivation. This is further supported by the study of Kumar and Rai
(1978), in which it was demonstrated that additional phosphate dosing
countered the effect on algal growth. The phosphate deprivation effect
is not considered environmentally relevant as it may only occur
extremely locally. Overall, in view of the extremely low bioavailability
of zirconium in environmentally relevant media at environmentally
relevant conditions, it can be concluded that zirconium from zirconium
dichloride oxide is not toxic to aquatic organisms.
Similarly, microorganisms in a sewage treatment plant are not expected
to be exposed to zirconium (dichloride oxide), as zirconium will have
been removed from the water column through hydrolysis and carbonate
and/or phosphate complexation before reaching the biological treatment
step. Often a pH increase step is included for metal precipitation as
one of the (first) waste water treatment steps in on-site waste water
treatment plants. If such as step is included the removal efficiency
will be 100%. Moreover, no adverse effects have been observed in an
activated sludge respiration inhibition test with the read across
substance zirconium acetate, another 'water soluble' zirconium compound
with similar behaviour in the aquatic environment as zirconium
dichloride oxide. Therefore no PNEC needs to be derived.
As no PNEC aquatic could be derived, no PNEC values for soil and
sediment can be derived either by using the equilibrium partitioning
method. No toxicity data are available for sediment or soil organisms,
except for a short-term toxicity study with terrestrial plants, yielding
only unbound NOEC values. Therefore, no PNEC values for soil and
sediment can be derived applying the assessment factor method either.
Since zirconium dichloride oxide is not considered hazardous to the
environment, no chemical safety assessment needs to be conducted and
therefore no PNECs need to be derived for these compartments.
No long-term oral or dietary avian toxicity studies are available. A
repeated dose toxicity study in rats (OECD 422 study with zirconium
acetate, another 'water soluble' zirconium compound) did not observe any
significant adverse effects up to and including the highest test dose
(NOAEL >= 1000 mg/kg bw/day, based on anhydrous test compound).
Therefore no PNEC oral can be derived. This route is also not relevant
anyway as it can reasonably be assumed that zirconium will not
bioaccumulate in the food chain.
The substance does not need to be classified for environmental hazards,
based on the available information for zirconium dichloride oxide, used
in combination with information from read across substances. In none of
the studies used to cover the aquatic toxicity endpoints, adverse
effects have been observed up to and including the limit test
concentration of 100 mg/L or upon exposure to a 100% v/v saturated
solution. Only for algae, growth inhibition was observed at this limit
test concentration for zirconium dichloride oxide as well as for two
read across substances, however, the observed inhibition was concurrent
with phosphate depletion from the test medium (through heavy
complexation with zirconium), and was hence considered a phosphate
deprivation effect, which is not considered relevant at a normal
environmental scale. Since there were no signs of primary toxicity, the
effect in algae was not considered relevant for hazard assessment or
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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