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EC number: 235-120-4
CAS number: 12070-08-5
The acute toxicity to aquatic invertebrates was tested using titanium dioxide and titanium. Hence, for titanium carbide this endpoint is derived by read-across from titanium dioxide and titanium.Reliable, publically available relevant data for TiO2 short-term toxicity to aquatic invertebrates do not report mortality in any of the species tested. These data are used in a weight-of-evidence approach. Due to similar or lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide and titanium (the source substances), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.
al. (2008) examined the effect of TiO2 nanoparticles (primary
particle size distribution: 20.5 +/- 6.7 nm) to adult Daphnia pulex as
well as to neonate Cerodaphnia dubia (< 24 h). Test organisms
were exposed for 48 h to nominal concentrations of 0 (control) and 10
mg/L. Major particle diameters observed in suspension were 687.5 nm. 10
mg TiO2/L did not result in immobilisation in both species.
In a limit
study according to OECD guideline 202 (Johnson et al., 1986) Daphnia
magna was exposed to a single nominal concentration of 1000 mg TiO2/L
for 48 h. Microscopic examinations of daphnids following exposure to TiO2
suspensions showed that the daphnids filtered the TiO2 particles,
passing them to the gut. Thus combined oral exposure and exposure via
the aqueous phase did not result in 50 % mortality. The 48 hour EC50
was > 1000 mg/L.
Johnson et al. (1986) also Wahrheit et al. (2007) investigated the
effects of TiO2 on Daphnia magna after 48 h. While the
particle size of TiO2 used in the test was not stated by
Johnson et al. (1986), Wahrheit et al. (2007) used fine (defined as ~
100 nm) and ultrafine (defined as < 100 nm) test material at nominal
test concentrations of 0 (control), 0.1, 1.0, 10, 100 mg TiO2/L.
Actual particle size of ultrafine and fine TiO2 was 140 nm
and 380 nm, respectively. No toxic effects could be observed after
exposure for 48 h.
is in agreement with the result of Lovern & Klaper (2006) who studied
the short-term toxicity of TiO2 to Daphnia magna (U.S.
EPA standard operating procedure 2024) with different TiO2 samples
in two tests. TiO2 mixtures were prepared either by
sonication or placement in tetrahydrofuran (THF) and filtration.
Sonicated TiO2 samples were used at nominal test
concentrations of 50, 200, 250, 300, 400 and 500 ppm, whereas lower
concentrations of 0.2, 1, 2, 5, 6, 8 and 10 ppm were used for the
assessment of filtered (THF) samples. The way the particles were
prepared, however, influenced their toxicity: while unfiltered,
sonicated TiO2 samples did not cause mortality or only 9 %
effects at 500 ppm, filtered (THF) samples had toxic effects.
Transmission-electron micrograph (TEM) images of the solutions show that
the particles in the filtered solutions (filter size 200 nm) had a mean
particle diameter of 30 nm, while particle size of sonicated TiO2 solution
samples ranged from 100 to 500 nm. Thus, the study emphasises that the
type of dispersion and size of the TiO2 particles may
influence toxicity. Lovern & Klaper (2006) suggested that particle
aggregation likely is the reason for the absence of effects in
unfiltered, sonicated TiO2 samples.
obtained with the filtered (THF) TiO2 samples are not
considered relevant for real-world environmental exposure due to the
dispersion treatment of TiO2 before the toxicity test, and
only the results for sonicated, unfiltered TiO2 samples (48-h
EC50 > 100 ppm) are further considered in the assessment.
toxicity experiments with TiO2 (particle size: 100 nm and 200
nm) conducted by Dabrunz et al. (2011) did not result in mortality of Daphnia
magna after the standard exposure duration of 48 h at the maximum
concentration tested (8 mg/L) in any of the experiments. However,
prolonged exposure up to 96 h led to an increase in toxicity. In
addition, in experiments with prolonged exposure duration smaller
particle size resulted in higher toxicity. Besides, in a prolonged
experiment up to 96 h the authors observed “biological surface coating”
of neonate daphnids with TiO2 particles. This biological
surface coat completely disappeared with the first molting (shedding of
shell) but reoccurred within 1 h after the first molting and continued
steadily during the 96-h exposure period, causing a delay in molting and
significantly lower molting success of only 10% compared to the control
(p = 0.0065).
the standard duration of short-term toxicity experiments with daphnids
is 48 h, and substance assessment as well as classification and
labelling are based on standard experiments with an exposure duration of
48 h, and toxic effects may mainly be attributed to physical effects,
results obtained in the prolonged experiments are not carried forward to
the effects assessment of titanium carbide. In addition,
(eco-)toxicologically relevant release of Ti ions from titanium carbide
is not expected as the concentration of soluble Ti ions was below the
method detection limit (< 0.4 µg/L) in the T/D test. Thus, TiC is
considered to be practically insoluble and the formation of insoluble Ti
compounds due to Ti ion release form TiC with subsequent biological
surface coating and physical effects is considered to be irrelevant.
publications considered as reliable (see above), additional publically
available information of lower reliability is available on TiO2/Ti
short-term toxicity to aquatic invertebrates. These data are considered
supporting information only and are not decisive for the substance
(2008) investigated the 48-h toxicity of nano TiO2 (25–70 nm)
to T. platyurus and D. magna according to Standard
Operational Procedures “Thamnotoxkit F TM magna” (1995) and “Daphtoxkit
F TM magna” (1996), respectively. Nanosize TiO2 did not
induce mortality in T. platyurus at 20,000 mg/L whereas the same
concentration induced 60 % mortality in D. magna. No toxicity
could be observed at lower levels (incubation in the dark).
(48-h) of TiO2 nanoparticles (50–150 nm) at 100 mg/L on Chydorus
sphaericus were tested in a Chydotox test (Velzeboer et al., 2008).
Under the conditions of the Chydotox test no mortality was observed.
and Rico-Martínez (2001) investigated the influence of Ti (speciation as
well as test concentrations not specified) to neonate females of three
rotifer species (Lecane hamata,Lecane luna, and Lecane
quadridentata). Test organisms where exposed to the test substance
for 48 h. The 48-h LC50 (nominal concentrations) for Lecane
hamata, Lecane luna, and Lecane quadridentata are
15.6 mg Ti/L, 11.9 mg Ti/L and 8.5 mg Ti/L, respectively, demonstrating
different susceptibility to the test chemical.
al. (2005) conducted a one-week toxicity tests using the freshwater
amphipod Hyalella azteca. The 7-d LC50 of Ti (element)
to Hyalella azteca was determined to be 0.979 mg Ti/L (nominal)
or <0.272 mg Ti/L (measured).
of ecotoxic effects in most of the experiments referenced in this
section may at least partly be explained by low concentrations of small
TiO2 particles in suspension due to aggregation and
agglomeration (Lovern & Klaper, 2006; Velzeboer, 2008; Wahrheit et al.,
2007; Griffitt et al., 2008). It is assumed that the actual
concentrations of nano-sized TiO2 material in the tests were
probably far lower than the nominal test concentrations applied. The
results of Dabrunz et al. (2011) suggest that toxic effects that could
be partly observed at very high concentrations and/or prolonged exposure
duration is caused be physical effects.
lower transformation/dissolution results for titanium carbide (the
target substance) than titanium dioxide (the source substance) the
resulting toxicity potential is also be expected to be lower. Therefore,
the dose descriptors are expected to be sufficiently high for the target
substance, and read-across to the source chemical is adequately
protective. In fact, (eco-)toxicologically relevant release of Ti ions
from titanium carbide is not expected as the concentration of soluble Ti
ions was below the method detection limit (< 0.4 µg/L) in the T/D test.
Thus, TiC in considered to be practically insoluble. Release of Ti ions
to any ecotoxicologically relevant extent (and potential subsequent
formation of soluble and/or insoluble Ti compounds) is not expected.
Therefore, any toxic effects to aquatic invertebrates are not expected
to arise from TiC.
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