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EC number: 215-222-5
CAS number: 1314-13-2
Over the exposure period, post hatch survival of control
individuals was <70% (at 32dph).
A summary of the observations on zebrafish hatching success,
growth and survival of individuals exposed to ZnO nanoparticles (NM-110
= Z-COTE), ZnO bulk material (NM-113) and ionic zinc (Zn++)
Nominal test concentration
Measured test concentration as mean ± SD(µg ZnO/L)
on day 35
Mean % survival at hatching and day 32 post hatch
Standard Length at 32d post hatch
at 32d post hatch3
(mean ± SD)
observations calculated from initial stocking numbers
observations calculated from hatched individuals
based on censored data (Annex
Summary of life cycle effects in Zebrafish exposed to zinc oxide
nanoparticles expressed as LOEC and NOEC concentrations based on nominal
Larval total length
Larval dry weight
Delay in hatching
= days post hatch
= No-observed-effect concentration
= Lowest –observed-effect concentration
on cumulative number of larvae hatching on day 4 and day 5
rerio embroys were exposed to a various of doses of ZnO nanoparticles
(Z-COTE). The endpoints measured were
survival, Hatching success, Delay (if any) in hatching, Larval survival
(32dph), Larval weight at end of study (32dph) and standard larval
length at the end of the study
results from the biological data are discussed for time to hatching,
developmental and survival. There appears to be a slight delay in the
hatching of larvae exposed to >180 µg/L nZnO, however, this may be the
result of a data bias from one replicate tank and repetition of the
study is required to confirm this finding. As
no clear dose-dependent effect on growth or survival was observed with
respect to exposure to ZnO nanoparticles in the range tested, both NOEC
and LOEC values have been defined as > 540 µg/L. Data
from the additional bulk ZnO and Zn++positive control
treatments suggest that at similar concentrations of 180 µg/L ionic zinc
and bulk ZnO have an inhibitory effect on growth compared to nZnO. The
poor growth rates, high mortality at the transition from yolk-sac stage
to independent feeding and a notable number of undersized fish at the
end of the study all indicate that the larvae were either not feeding
properly or the dietary regime was sub-optimal. Following the transition
to an Artemia only diet there was always prey items present in the water
column of the exposure tanks and at termination on day 35, all
individuals measured under the microscope were observed to have food in
survival during the embryonic stage and immediately post hatching
suggests that the batch of eggs used in this study were of poor quality.
Additional handling and staging of individual eggs at the start of the
study may also have attributed to the poor survival. Despite the low
survival, no clear dose related effects following exposure to zinc oxide
nanoparticles in the concentration range tested were observed were
Per the 64th meeting of the ECHA Member State Committee (MSC), one of the three environmental toxicity study requests (fish testing) was removed from the draft in advance of the meeting, based on PfAs received, which MSC agreed to since fish were proven to be less sensitive to Zn2+ ions.
Nonetheless, for freshwater, the comparison of the chronic ecotoxicity data obtained within the same studies for the same species/endpoints after exposing the organisms to either the soluble Zn2+ion or the ZnO-NP form show that there is generally no difference in toxicity between the two Zn-forms.
The general observation of similar toxicity by the Zn-ion and the ZnO-NP is most relevant for the discussion on the aquatic PNEC developed for zinc substances; it can be concluded that the available data show that the general Zn-ion based PNEC for freshwater is relevant for the nano-ZnO, too.
Nano ZnO chronic toxicity
The present review focused notably on these chronic data, which are considered to be of major relevancy for the risk assessment and the related PNECs. Like for the acute toxicity, the data are presented in the attached tables as normalized values with the ecotoxicity value observed for the soluble zinc salts (Zn2+) as reference (ECx = 100%). The ratio ECx Zn2+/ECx nano ZnO is provided. The detail of the studies is available in the relevant IUCLID sections.
The freshwater chronic dataset now covers all main taxonomic groups, with 2 invertebrates (mollusc and crustacean), 2 algae, 1 fish species and 1 aquatic plant species. In addition, data on 1 sediment crustacean is also included. The full set of EC10/NOEC values are presented in the attached tables.
The marine chronic dataset covers all main taxonomic groups, with 1 invertebrate (clam), 2 algae, 1 fish species.
For freshwater, the comparison of the chronic ecotoxicity data obtained within the same studies for the same species/endpoints after exposing the organisms to either the soluble Zn2+ion or the ZnO-NP form show that there is generally no difference in toxicity between the two Zn-forms.
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